TY  - JOUR
AU  - Jovanović, Predrag
AU  - Borka Jovanović, Vesna
AU  - Borka, Duško
AU  - Popović, Luka Č.
PY  - 2020
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/8827
AB  - Here we study the potential observational signatures of supermassive black hole binaries (SMBHBs) in the Fe Kα line profiles emitted from the accretion disks around their components. We simulated the Fe Kα line emission from the relativistic accretion disks using ray tracing method in Kerr metric. The obtained profiles from the SMBHBs are then compared with those in the case of the single supermassive black holes (SMBHs). We considered two models of the SMBHBs: a model when the secondary SMBH is embedded in the accretion disk around the primary, causing an empty gap in the disk, and a model with clearly separated components, where the accretion disks around both primary and secondary give a significant contribution to the composite Fe Kα line emission of a such SMBHB. The obtained results showed that both models of SMBHBs can leave imprints in the form of ripples in the cores of the emitted Fe Kα line profiles, which may look like an absorption component in the line profile. However, in the case of the composite line profiles emitted from two accretion disks, these ripples could have much higher amplitudes and strongly depend on orbital phase of the system, while for those emitted from a disk with an empty gap, the corresponding ripples mostly have lower amplitudes and do not vary significantly with orbital phase. The present day X-ray telescopes are not able to detect such signatures in the observed X-ray spectra of SMBHBs. However this will be possible with the next generation of X-ray observatories, which will also enable application of such effects as a tool for studying the properties of these objects. © 2020, Astronomical Institute, Slovak Academy of Sciences.
T2  - Contributions of the Astronomical Observatory Skalnaté Pleso
T1  - Possible observational signatures of supermassive black hole binaries in their Fe Kα line profiles
VL  - 50
IS  - 1
SP  - 219
EP  - 234
DO  - 10.31577/caosp.2020.50.1.219
ER  - 

@article{
author = "Jovanović, Predrag and Borka Jovanović, Vesna and Borka, Duško and Popović, Luka Č.",
year = "2020",
abstract = "Here we study the potential observational signatures of supermassive black hole binaries (SMBHBs) in the Fe Kα line profiles emitted from the accretion disks around their components. We simulated the Fe Kα line emission from the relativistic accretion disks using ray tracing method in Kerr metric. The obtained profiles from the SMBHBs are then compared with those in the case of the single supermassive black holes (SMBHs). We considered two models of the SMBHBs: a model when the secondary SMBH is embedded in the accretion disk around the primary, causing an empty gap in the disk, and a model with clearly separated components, where the accretion disks around both primary and secondary give a significant contribution to the composite Fe Kα line emission of a such SMBHB. The obtained results showed that both models of SMBHBs can leave imprints in the form of ripples in the cores of the emitted Fe Kα line profiles, which may look like an absorption component in the line profile. However, in the case of the composite line profiles emitted from two accretion disks, these ripples could have much higher amplitudes and strongly depend on orbital phase of the system, while for those emitted from a disk with an empty gap, the corresponding ripples mostly have lower amplitudes and do not vary significantly with orbital phase. The present day X-ray telescopes are not able to detect such signatures in the observed X-ray spectra of SMBHBs. However this will be possible with the next generation of X-ray observatories, which will also enable application of such effects as a tool for studying the properties of these objects. © 2020, Astronomical Institute, Slovak Academy of Sciences.",
journal = "Contributions of the Astronomical Observatory Skalnaté Pleso",
title = "Possible observational signatures of supermassive black hole binaries in their Fe Kα line profiles",
volume = "50",
number = "1",
pages = "219-234",
doi = "10.31577/caosp.2020.50.1.219"
}

Jovanović, P., Borka Jovanović, V., Borka, D.,& Popović, L. Č.. (2020). Possible observational signatures of supermassive black hole binaries in their Fe Kα line profiles. in Contributions of the Astronomical Observatory Skalnaté Pleso, 50(1), 219-234.
https://doi.org/10.31577/caosp.2020.50.1.219

Jovanović P, Borka Jovanović V, Borka D, Popović LČ. Possible observational signatures of supermassive black hole binaries in their Fe Kα line profiles. in Contributions of the Astronomical Observatory Skalnaté Pleso. 2020;50(1):219-234.
doi:10.31577/caosp.2020.50.1.219 .

Jovanović, Predrag, Borka Jovanović, Vesna, Borka, Duško, Popović, Luka Č., "Possible observational signatures of supermassive black hole binaries in their Fe Kα line profiles" in Contributions of the Astronomical Observatory Skalnaté Pleso, 50, no. 1 (2020):219-234,
https://doi.org/10.31577/caosp.2020.50.1.219 . .

TY  - JOUR
AU  - Zakharov, Alexander F.
AU  - Jovanović, Predrag
AU  - Borka, Duško
AU  - Borka Jovanović, Vesna
PY  - 2020
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/8826
AB  - It is established that there are supermassive black holes in centers of galaxies. A supermassive black hole with mass around 4 × 106 M⊙ is located at the Galactic Center. Such an approach for the Galactic Center looks rather natural, in spite of that consequences of model must be checked with observa- tions. We discuss opportunities to check this with forthcoming observations of shadows in mm band for the Galactic Center as it was done recently for M87*. Observations of bright stars moving near the Galactic Center gives another op-portunity to evaluate gravitational potential. We discuss opportunities to use these observations to constrain alternative theories of gravity. © 2020, Astronomical Institute, Slovak Academy of Sciences.
T2  - Contributions of the Astronomical Observatory Skalnaté Pleso
T1  - Observational tests of general relativity and alternative theories of gravity with Galactic Center observations using current and future large observational facilities
VL  - 50
IS  - 1
SP  - 203
EP  - 218
DO  - 10.31577/caosp.2020.50.1.203
ER  - 

@article{
author = "Zakharov, Alexander F. and Jovanović, Predrag and Borka, Duško and Borka Jovanović, Vesna",
year = "2020",
abstract = "It is established that there are supermassive black holes in centers of galaxies. A supermassive black hole with mass around 4 × 106 M⊙ is located at the Galactic Center. Such an approach for the Galactic Center looks rather natural, in spite of that consequences of model must be checked with observa- tions. We discuss opportunities to check this with forthcoming observations of shadows in mm band for the Galactic Center as it was done recently for M87*. Observations of bright stars moving near the Galactic Center gives another op-portunity to evaluate gravitational potential. We discuss opportunities to use these observations to constrain alternative theories of gravity. © 2020, Astronomical Institute, Slovak Academy of Sciences.",
journal = "Contributions of the Astronomical Observatory Skalnaté Pleso",
title = "Observational tests of general relativity and alternative theories of gravity with Galactic Center observations using current and future large observational facilities",
volume = "50",
number = "1",
pages = "203-218",
doi = "10.31577/caosp.2020.50.1.203"
}

Zakharov, A. F., Jovanović, P., Borka, D.,& Borka Jovanović, V.. (2020). Observational tests of general relativity and alternative theories of gravity with Galactic Center observations using current and future large observational facilities. in Contributions of the Astronomical Observatory Skalnaté Pleso, 50(1), 203-218.
https://doi.org/10.31577/caosp.2020.50.1.203

Zakharov AF, Jovanović P, Borka D, Borka Jovanović V. Observational tests of general relativity and alternative theories of gravity with Galactic Center observations using current and future large observational facilities. in Contributions of the Astronomical Observatory Skalnaté Pleso. 2020;50(1):203-218.
doi:10.31577/caosp.2020.50.1.203 .

Zakharov, Alexander F., Jovanović, Predrag, Borka, Duško, Borka Jovanović, Vesna, "Observational tests of general relativity and alternative theories of gravity with Galactic Center observations using current and future large observational facilities" in Contributions of the Astronomical Observatory Skalnaté Pleso, 50, no. 1 (2020):203-218,
https://doi.org/10.31577/caosp.2020.50.1.203 . .

TY  - JOUR
AU  - Dialektopoulos, Konstantinos F.
AU  - Borka, Duško
AU  - Capozziello, Salvatore
AU  - Borka Jovanović, Vesna
AU  - Jovanović, Predrag
PY  - 2019
UR  - https://link.aps.org/doi/10.1103/PhysRevD.99.044053
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/8084
AB  - Nonlocal theories of gravity have recently drawn a lot of attention because they can suitably represent the behavior of gravitational interaction in the ultraviolet regime. Furthermore, at infrared scales, they give rise to notable cosmological effects which could be important to describe the dark energy behavior. In particular, exponential forms of the distortion function seem particularly useful for this purpose. Using Noether symmetries, it can be shown that the only nontrivial form of the distortion function is the exponential one, which is working not only for cosmological minisuperspaces, but also in a spherically symmetric spacetime. Taking this result into account, we study the weak-field approximation of this type of nonlocal gravity, and comparing with the orbits of the S2 star around the Galactic center (NTT/VLT data), we set constraints on the parameters of the theory. Nonlocal effects do not play a significant role on the orbits of S2 stars around Sgr A∗ but give richer phenomenology at cosmological scales than the ΛCDM model. Also, we show that the nonlocal gravity model gives better agreement between theory and astronomical observations than Keplerian orbits. © 2019 American Physical Society.
T2  - Physical Review D
T1  - Constraining nonlocal gravity by S2 star orbits
VL  - 99
IS  - 4
SP  - 044053
DO  - 10.1103/PhysRevD.99.044053
ER  - 

@article{
author = "Dialektopoulos, Konstantinos F. and Borka, Duško and Capozziello, Salvatore and Borka Jovanović, Vesna and Jovanović, Predrag",
year = "2019",
abstract = "Nonlocal theories of gravity have recently drawn a lot of attention because they can suitably represent the behavior of gravitational interaction in the ultraviolet regime. Furthermore, at infrared scales, they give rise to notable cosmological effects which could be important to describe the dark energy behavior. In particular, exponential forms of the distortion function seem particularly useful for this purpose. Using Noether symmetries, it can be shown that the only nontrivial form of the distortion function is the exponential one, which is working not only for cosmological minisuperspaces, but also in a spherically symmetric spacetime. Taking this result into account, we study the weak-field approximation of this type of nonlocal gravity, and comparing with the orbits of the S2 star around the Galactic center (NTT/VLT data), we set constraints on the parameters of the theory. Nonlocal effects do not play a significant role on the orbits of S2 stars around Sgr A∗ but give richer phenomenology at cosmological scales than the ΛCDM model. Also, we show that the nonlocal gravity model gives better agreement between theory and astronomical observations than Keplerian orbits. © 2019 American Physical Society.",
journal = "Physical Review D",
title = "Constraining nonlocal gravity by S2 star orbits",
volume = "99",
number = "4",
pages = "044053",
doi = "10.1103/PhysRevD.99.044053"
}

Dialektopoulos, K. F., Borka, D., Capozziello, S., Borka Jovanović, V.,& Jovanović, P.. (2019). Constraining nonlocal gravity by S2 star orbits. in Physical Review D, 99(4), 044053.
https://doi.org/10.1103/PhysRevD.99.044053

Dialektopoulos KF, Borka D, Capozziello S, Borka Jovanović V, Jovanović P. Constraining nonlocal gravity by S2 star orbits. in Physical Review D. 2019;99(4):044053.
doi:10.1103/PhysRevD.99.044053 .

Dialektopoulos, Konstantinos F., Borka, Duško, Capozziello, Salvatore, Borka Jovanović, Vesna, Jovanović, Predrag, "Constraining nonlocal gravity by S2 star orbits" in Physical Review D, 99, no. 4 (2019):044053,
https://doi.org/10.1103/PhysRevD.99.044053 . .

TY  - JOUR
AU  - Dialektopoulos, Konstantinos F.
AU  - Borka, Duško
AU  - Capozziello, Salvatore
AU  - Borka Jovanović, Vesna
AU  - Jovanović, Predrag
PY  - 2019
UR  - https://link.aps.org/doi/10.1103/PhysRevD.99.044053
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/8090
AB  - Nonlocal theories of gravity have recently drawn a lot of attention because they can suitably represent the behavior of gravitational interaction in the ultraviolet regime. Furthermore, at infrared scales, they give rise to notable cosmological effects which could be important to describe the dark energy behavior. In particular, exponential forms of the distortion function seem particularly useful for this purpose. Using Noether symmetries, it can be shown that the only nontrivial form of the distortion function is the exponential one, which is working not only for cosmological minisuperspaces, but also in a spherically symmetric spacetime. Taking this result into account, we study the weak-field approximation of this type of nonlocal gravity, and comparing with the orbits of the S2 star around the Galactic center (NTT/VLT data), we set constraints on the parameters of the theory. Nonlocal effects do not play a significant role on the orbits of S2 stars around Sgr A∗ but give richer phenomenology at cosmological scales than the ΛCDM model. Also, we show that the nonlocal gravity model gives better agreement between theory and astronomical observations than Keplerian orbits.
T2  - Physical Review D
T1  - Constraining nonlocal gravity by S2 star orbits
VL  - 99
IS  - 4
SP  - 044053
DO  - 10.1103/PhysRevD.99.044053
ER  - 

@article{
author = "Dialektopoulos, Konstantinos F. and Borka, Duško and Capozziello, Salvatore and Borka Jovanović, Vesna and Jovanović, Predrag",
year = "2019",
abstract = "Nonlocal theories of gravity have recently drawn a lot of attention because they can suitably represent the behavior of gravitational interaction in the ultraviolet regime. Furthermore, at infrared scales, they give rise to notable cosmological effects which could be important to describe the dark energy behavior. In particular, exponential forms of the distortion function seem particularly useful for this purpose. Using Noether symmetries, it can be shown that the only nontrivial form of the distortion function is the exponential one, which is working not only for cosmological minisuperspaces, but also in a spherically symmetric spacetime. Taking this result into account, we study the weak-field approximation of this type of nonlocal gravity, and comparing with the orbits of the S2 star around the Galactic center (NTT/VLT data), we set constraints on the parameters of the theory. Nonlocal effects do not play a significant role on the orbits of S2 stars around Sgr A∗ but give richer phenomenology at cosmological scales than the ΛCDM model. Also, we show that the nonlocal gravity model gives better agreement between theory and astronomical observations than Keplerian orbits.",
journal = "Physical Review D",
title = "Constraining nonlocal gravity by S2 star orbits",
volume = "99",
number = "4",
pages = "044053",
doi = "10.1103/PhysRevD.99.044053"
}

Dialektopoulos, K. F., Borka, D., Capozziello, S., Borka Jovanović, V.,& Jovanović, P.. (2019). Constraining nonlocal gravity by S2 star orbits. in Physical Review D, 99(4), 044053.
https://doi.org/10.1103/PhysRevD.99.044053

Dialektopoulos KF, Borka D, Capozziello S, Borka Jovanović V, Jovanović P. Constraining nonlocal gravity by S2 star orbits. in Physical Review D. 2019;99(4):044053.
doi:10.1103/PhysRevD.99.044053 .

Dialektopoulos, Konstantinos F., Borka, Duško, Capozziello, Salvatore, Borka Jovanović, Vesna, Jovanović, Predrag, "Constraining nonlocal gravity by S2 star orbits" in Physical Review D, 99, no. 4 (2019):044053,
https://doi.org/10.1103/PhysRevD.99.044053 . .

TY  - CONF
AU  - Ignjatović, Siniša R.
AU  - Borka Jovanović, Vesna
AU  - Borka, Duško
AU  - Jovanović, Predrag
PY  - 2019
UR  - http://aip.scitation.org/doi/abs/10.1063/1.5091205
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/8093
AB  - The simplest form of the Hyperfine Interaction (HFI) of quarks is a color-spin interaction, sometimes called Fermi-Breit (FB) HFI. For conventional hadrons, this HFI for quark-antiquark (qq) pairs is twice as strong as the same HFI for quark-quark (qq or qq) pairs, but this difference is absorbed into the different HFI constants for mesons and baryons, which are free parameters of the fits. For tetraquarks, however, qqHFI is only half as strong as the qq/qqHFI and both kinds of pairs coexist within the same state. Hence it is worth investigating a model with different fit constants for qq and qq/q pairs. We have investigated 3 models of spin-color HFI for light scalar tetraquarks: 2 models with single constants for both kinds of pairs and one model with different fit constants. The light scalar nonet is chosen because of a lack of other experimentally observed multiplets interpretable as pure exotic states. Since even the nonet contains only 3 particles with distinct masses (i. e. 3 fit points), the constituent quark masses had to be taken from conventional hadron fits obtained in our previous work. The two-constant model did not prove to be a viable alternative to the one-constant models. © 2019 Author(s).
C3  - AIP Conference Proceedings
T1  - Hyperfine interactions of constituent quarks and the mass spectrum of tetraquark states
VL  - 2075
SP  - 080004
DO  - 10.1063/1.5091205
ER  - 

@conference{
author = "Ignjatović, Siniša R. and Borka Jovanović, Vesna and Borka, Duško and Jovanović, Predrag",
year = "2019",
abstract = "The simplest form of the Hyperfine Interaction (HFI) of quarks is a color-spin interaction, sometimes called Fermi-Breit (FB) HFI. For conventional hadrons, this HFI for quark-antiquark (qq) pairs is twice as strong as the same HFI for quark-quark (qq or qq) pairs, but this difference is absorbed into the different HFI constants for mesons and baryons, which are free parameters of the fits. For tetraquarks, however, qqHFI is only half as strong as the qq/qqHFI and both kinds of pairs coexist within the same state. Hence it is worth investigating a model with different fit constants for qq and qq/q pairs. We have investigated 3 models of spin-color HFI for light scalar tetraquarks: 2 models with single constants for both kinds of pairs and one model with different fit constants. The light scalar nonet is chosen because of a lack of other experimentally observed multiplets interpretable as pure exotic states. Since even the nonet contains only 3 particles with distinct masses (i. e. 3 fit points), the constituent quark masses had to be taken from conventional hadron fits obtained in our previous work. The two-constant model did not prove to be a viable alternative to the one-constant models. © 2019 Author(s).",
journal = "AIP Conference Proceedings",
title = "Hyperfine interactions of constituent quarks and the mass spectrum of tetraquark states",
volume = "2075",
pages = "080004",
doi = "10.1063/1.5091205"
}

Ignjatović, S. R., Borka Jovanović, V., Borka, D.,& Jovanović, P.. (2019). Hyperfine interactions of constituent quarks and the mass spectrum of tetraquark states. in AIP Conference Proceedings, 2075, 080004.
https://doi.org/10.1063/1.5091205

Ignjatović SR, Borka Jovanović V, Borka D, Jovanović P. Hyperfine interactions of constituent quarks and the mass spectrum of tetraquark states. in AIP Conference Proceedings. 2019;2075:080004.
doi:10.1063/1.5091205 .

Ignjatović, Siniša R., Borka Jovanović, Vesna, Borka, Duško, Jovanović, Predrag, "Hyperfine interactions of constituent quarks and the mass spectrum of tetraquark states" in AIP Conference Proceedings, 2075 (2019):080004,
https://doi.org/10.1063/1.5091205 . .

TY  - JOUR
AU  - Jovanović, Predrag
AU  - Borka, Duško
AU  - Borka Jovanović, Vesna
PY  - 2019
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/8788
AB  - In this work we used the observed additional perihelion precession in the Solar System, obtained from the observations of planets and spacecrafts, to study the possible existence of Yukawa correction term to the Newtonian gravitational potential. Our study was motivated by previous analyses which indicated the possible discrepancies from Newtonian gravity in this form and at wide range of astrophysical scales. Yukawa gravity was introduced to cure some shortcomings of General Relativity (GR) at galactic and extragalactic scales. We demonstrated that this form of gravity can give the values for orbital precession which are comparable or even in better agreement with observations than the corresponding predictions of GR. The obtained results can be used for setting stronger constraints on variation of the gravitational constant G, as well as on the fundamental constant δ of Yukawa gravity. Moreover, Yukawa gravity could be used to improve the results for the motion of planets, other Solar System bodies, as well as spacecrafts, and as a consequence, it can help us to get more reliable predictions for natural hazards in the Solar System, such as potential impacts by near-Earth objects. © 2019, Geographical Institute "Jovan Cviji" of the Serbian Academy of Sciences and Arts. All rights reserved.
T2  - Journal of the Geographical Institute Jovan Cvijic, SASA
T1  - Constraining Yukawa gravity from planetary motion in the solar system
VL  - 69
IS  - 3
SP  - 265
EP  - 269
DO  - 10.2298/IJGI1903265J
ER  - 

@article{
author = "Jovanović, Predrag and Borka, Duško and Borka Jovanović, Vesna",
year = "2019",
abstract = "In this work we used the observed additional perihelion precession in the Solar System, obtained from the observations of planets and spacecrafts, to study the possible existence of Yukawa correction term to the Newtonian gravitational potential. Our study was motivated by previous analyses which indicated the possible discrepancies from Newtonian gravity in this form and at wide range of astrophysical scales. Yukawa gravity was introduced to cure some shortcomings of General Relativity (GR) at galactic and extragalactic scales. We demonstrated that this form of gravity can give the values for orbital precession which are comparable or even in better agreement with observations than the corresponding predictions of GR. The obtained results can be used for setting stronger constraints on variation of the gravitational constant G, as well as on the fundamental constant δ of Yukawa gravity. Moreover, Yukawa gravity could be used to improve the results for the motion of planets, other Solar System bodies, as well as spacecrafts, and as a consequence, it can help us to get more reliable predictions for natural hazards in the Solar System, such as potential impacts by near-Earth objects. © 2019, Geographical Institute "Jovan Cviji" of the Serbian Academy of Sciences and Arts. All rights reserved.",
journal = "Journal of the Geographical Institute Jovan Cvijic, SASA",
title = "Constraining Yukawa gravity from planetary motion in the solar system",
volume = "69",
number = "3",
pages = "265-269",
doi = "10.2298/IJGI1903265J"
}

Jovanović, P., Borka, D.,& Borka Jovanović, V.. (2019). Constraining Yukawa gravity from planetary motion in the solar system. in Journal of the Geographical Institute Jovan Cvijic, SASA, 69(3), 265-269.
https://doi.org/10.2298/IJGI1903265J

Jovanović P, Borka D, Borka Jovanović V. Constraining Yukawa gravity from planetary motion in the solar system. in Journal of the Geographical Institute Jovan Cvijic, SASA. 2019;69(3):265-269.
doi:10.2298/IJGI1903265J .

Jovanović, Predrag, Borka, Duško, Borka Jovanović, Vesna, "Constraining Yukawa gravity from planetary motion in the solar system" in Journal of the Geographical Institute Jovan Cvijic, SASA, 69, no. 3 (2019):265-269,
https://doi.org/10.2298/IJGI1903265J . .

TY  - JOUR
AU  - Zakharov, Alexander F.
AU  - Jovanović, Predrag
AU  - Borka, Duško
AU  - Borka Jovanović, Vesna
PY  - 2018
UR  - http://stacks.iop.org/1475-7516/2018/i=04/a=050?key=crossref.a23e3c8d44b40fe0c07114ff29f9d9ae
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/7668
AB  - Recently, the LIGO-Virgo collaboration discovered gravitational waves and in their first publication on the subject the authors also presented a graviton mass constraint as m(g) < 1.2 x 10(-22) eV {[}1] (see also more details in a complimentary paper {[}2]). In our previous papers we considered constraints on Yukawa gravity parameters {[}3] and on graviton mass from analysis of the trajectory of S2 star near the Galactic Center {[}4]. In the paper we analyze a potential to reduce upper bounds for graviton mass with future observational data on trajectories of bright stars near the Galactic Center. Since gravitational potentials are different for these two cases, expressions for relativistic advance for general relativity and Yukawa potential are different functions on eccentricity and semimajor axis, it gives an opportunity to improve current estimates of graviton mass with future observational facilities. In our considerations of an improvement potential for a graviton mass estimate we adopt a conservative strategy and assume that trajectories of bright stars and their apocenter advance will be described with general relativity expressions and it gives opportunities to improve graviton mass constraints. In contrast with our previous studies, where we present current constraints on parameters of Yukawa gravity {[}3] and graviton mass {[}4] from observations of S2 star, in the paper we express expectations to improve current constraints for graviton mass, assuming the GR predictions about apocenter shifts will be confirmed with future observations. We concluded that if future observations of bright star orbits during around fifty years will confirm GR predictions about apocenter shifts of bright star orbits it give an opportunity to constrain a graviton mass at a level around 5 x 10(-23) eV or slightly better than current estimates obtained with LIGO observations.
T2  - Journal of Cosmology and Astroparticle Physics
T1  - Constraining the range of Yukawa gravity interaction from S2 star orbits III: improvement expectations for graviton mass bounds
VL  - 2018
IS  - 04
SP  - 050
EP  - 050
DO  - 10.1088/1475-7516/2018/04/050
ER  - 

@article{
author = "Zakharov, Alexander F. and Jovanović, Predrag and Borka, Duško and Borka Jovanović, Vesna",
year = "2018",
abstract = "Recently, the LIGO-Virgo collaboration discovered gravitational waves and in their first publication on the subject the authors also presented a graviton mass constraint as m(g) < 1.2 x 10(-22) eV {[}1] (see also more details in a complimentary paper {[}2]). In our previous papers we considered constraints on Yukawa gravity parameters {[}3] and on graviton mass from analysis of the trajectory of S2 star near the Galactic Center {[}4]. In the paper we analyze a potential to reduce upper bounds for graviton mass with future observational data on trajectories of bright stars near the Galactic Center. Since gravitational potentials are different for these two cases, expressions for relativistic advance for general relativity and Yukawa potential are different functions on eccentricity and semimajor axis, it gives an opportunity to improve current estimates of graviton mass with future observational facilities. In our considerations of an improvement potential for a graviton mass estimate we adopt a conservative strategy and assume that trajectories of bright stars and their apocenter advance will be described with general relativity expressions and it gives opportunities to improve graviton mass constraints. In contrast with our previous studies, where we present current constraints on parameters of Yukawa gravity {[}3] and graviton mass {[}4] from observations of S2 star, in the paper we express expectations to improve current constraints for graviton mass, assuming the GR predictions about apocenter shifts will be confirmed with future observations. We concluded that if future observations of bright star orbits during around fifty years will confirm GR predictions about apocenter shifts of bright star orbits it give an opportunity to constrain a graviton mass at a level around 5 x 10(-23) eV or slightly better than current estimates obtained with LIGO observations.",
journal = "Journal of Cosmology and Astroparticle Physics",
title = "Constraining the range of Yukawa gravity interaction from S2 star orbits III: improvement expectations for graviton mass bounds",
volume = "2018",
number = "04",
pages = "050-050",
doi = "10.1088/1475-7516/2018/04/050"
}

Zakharov, A. F., Jovanović, P., Borka, D.,& Borka Jovanović, V.. (2018). Constraining the range of Yukawa gravity interaction from S2 star orbits III: improvement expectations for graviton mass bounds. in Journal of Cosmology and Astroparticle Physics, 2018(04), 050-050.
https://doi.org/10.1088/1475-7516/2018/04/050

Zakharov AF, Jovanović P, Borka D, Borka Jovanović V. Constraining the range of Yukawa gravity interaction from S2 star orbits III: improvement expectations for graviton mass bounds. in Journal of Cosmology and Astroparticle Physics. 2018;2018(04):050-050.
doi:10.1088/1475-7516/2018/04/050 .

Zakharov, Alexander F., Jovanović, Predrag, Borka, Duško, Borka Jovanović, Vesna, "Constraining the range of Yukawa gravity interaction from S2 star orbits III: improvement expectations for graviton mass bounds" in Journal of Cosmology and Astroparticle Physics, 2018, no. 04 (2018):050-050,
https://doi.org/10.1088/1475-7516/2018/04/050 . .

TY  - CONF
AU  - Capozziello, Salvatore
AU  - Borka, Duško
AU  - Borka Jovanović, Vesna
AU  - Jovanović, Predrag
PY  - 2018
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/7748
AB  - We demonstrate that the existence of a Noether symmetry in f (R) theories of gravity gives rise to an additional gravitational radius, besides the standard Schwarzschild one, determining the dynamics at galactic scales. By this feature, it is possible to explain the baryonic Tully-Fisher relation and the rotation curve of gas-rich galaxies without the dark matter hypothesis. Furthermore, under the same standard, the Fundamental Plane of elliptical galaxies can be addressed.
C3  - Galaxies
T1  - Galactic Structures from Gravitational Radii
VL  - 6
IS  - 1
SP  - 22
DO  - 10.3390/galaxies6010022
ER  - 

@conference{
author = "Capozziello, Salvatore and Borka, Duško and Borka Jovanović, Vesna and Jovanović, Predrag",
year = "2018",
abstract = "We demonstrate that the existence of a Noether symmetry in f (R) theories of gravity gives rise to an additional gravitational radius, besides the standard Schwarzschild one, determining the dynamics at galactic scales. By this feature, it is possible to explain the baryonic Tully-Fisher relation and the rotation curve of gas-rich galaxies without the dark matter hypothesis. Furthermore, under the same standard, the Fundamental Plane of elliptical galaxies can be addressed.",
journal = "Galaxies",
title = "Galactic Structures from Gravitational Radii",
volume = "6",
number = "1",
pages = "22",
doi = "10.3390/galaxies6010022"
}

Capozziello, S., Borka, D., Borka Jovanović, V.,& Jovanović, P.. (2018). Galactic Structures from Gravitational Radii. in Galaxies, 6(1), 22.
https://doi.org/10.3390/galaxies6010022

Capozziello S, Borka D, Borka Jovanović V, Jovanović P. Galactic Structures from Gravitational Radii. in Galaxies. 2018;6(1):22.
doi:10.3390/galaxies6010022 .

Capozziello, Salvatore, Borka, Duško, Borka Jovanović, Vesna, Jovanović, Predrag, "Galactic Structures from Gravitational Radii" in Galaxies, 6, no. 1 (2018):22,
https://doi.org/10.3390/galaxies6010022 . .

TY  - JOUR
AU  - Borka Jovanović, Vesna
AU  - Jovanović, Predrag
AU  - Borka, Duško
AU  - Capozziello, Salvatore
PY  - 2018
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/7781
AB  - The role of f(R) gravity, as well as the other modifications of standard Einstein’s gravity, is to explain the accelerated expansion, structure formation of the Universe, and some other phenomena at extragalactic scales (such as e.g. flat rotation curves of spiral galaxies) without adding unknown forms of dark energy or dark matter. In f(R) model, the Ricci scalar in the Einstein–Hilbert action is replaced by a general function of it. Its power-law form Rn is analyzed here using observed orbits of S-stars around the Galactic Center and also their computer simulations. We review the various consequences of the Rn gravity parameters (rc, the characteristic radius, i.e. the scalelength depending on the gravitating system properties; and β, the universal constant) on stellar dynamics and investigate their constraints from the observed S-star orbits. The presented results show that these observations could put reliable constraints on the parameters of Rn gravity.
T2  - Astronomical and Astrophysical Transactions
T1  - Rn gravity as a viable alternative to dark matter: Application to stellar dynamics
VL  - 30
IS  - 3
SP  - 351
EP  - 358
UR  - https://hdl.handle.net/21.15107/rcub_vinar_7781
ER  - 

@article{
author = "Borka Jovanović, Vesna and Jovanović, Predrag and Borka, Duško and Capozziello, Salvatore",
year = "2018",
abstract = "The role of f(R) gravity, as well as the other modifications of standard Einstein’s gravity, is to explain the accelerated expansion, structure formation of the Universe, and some other phenomena at extragalactic scales (such as e.g. flat rotation curves of spiral galaxies) without adding unknown forms of dark energy or dark matter. In f(R) model, the Ricci scalar in the Einstein–Hilbert action is replaced by a general function of it. Its power-law form Rn is analyzed here using observed orbits of S-stars around the Galactic Center and also their computer simulations. We review the various consequences of the Rn gravity parameters (rc, the characteristic radius, i.e. the scalelength depending on the gravitating system properties; and β, the universal constant) on stellar dynamics and investigate their constraints from the observed S-star orbits. The presented results show that these observations could put reliable constraints on the parameters of Rn gravity.",
journal = "Astronomical and Astrophysical Transactions",
title = "Rn gravity as a viable alternative to dark matter: Application to stellar dynamics",
volume = "30",
number = "3",
pages = "351-358",
url = "https://hdl.handle.net/21.15107/rcub_vinar_7781"
}

Borka Jovanović, V., Jovanović, P., Borka, D.,& Capozziello, S.. (2018). Rn gravity as a viable alternative to dark matter: Application to stellar dynamics. in Astronomical and Astrophysical Transactions, 30(3), 351-358.
https://hdl.handle.net/21.15107/rcub_vinar_7781

Borka Jovanović V, Jovanović P, Borka D, Capozziello S. Rn gravity as a viable alternative to dark matter: Application to stellar dynamics. in Astronomical and Astrophysical Transactions. 2018;30(3):351-358.
https://hdl.handle.net/21.15107/rcub_vinar_7781 .

Borka Jovanović, Vesna, Jovanović, Predrag, Borka, Duško, Capozziello, Salvatore, "Rn gravity as a viable alternative to dark matter: Application to stellar dynamics" in Astronomical and Astrophysical Transactions, 30, no. 3 (2018):351-358,
https://hdl.handle.net/21.15107/rcub_vinar_7781 .

TY  - JOUR
AU  - Borka Jovanović, Vesna
AU  - Jovanović, Predrag
AU  - Borka, Duško
AU  - Capozziello, Salvatore
PY  - 2018
UR  - http://www.mdpi.com/2218-2004/7/1/4
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/8218
AB  - The global properties of elliptical galaxies are connected through the so-called fundamental plane of ellipticals, which is an empirical relation between their parameters: effective radius, central velocity dispersion and mean surface brightness within the effective radius. We investigated the relation between the parameters of the fundamental plane equation and the parameters of modified gravity potential f ( R ) . With that aim, we compared theoretical predictions for circular velocity in f ( R ) gravity with the corresponding values from a large sample of observed elliptical galaxies. Besides, we consistently reproduced the values of coefficients of the fundamental plane equation as deduced from observations, showing that the photometric quantities like mean surface brightness are related to gravitational parameters. We show that this type of modified gravity, especially its power-law version— R n , is able to reproduce the stellar dynamics in elliptical galaxies. In addition, it is shown that R n gravity fits the observations very well, without the need for a dark matter.
T2  - Atoms
T1  - Fundamental Plane of Elliptical Galaxies in f(R) Gravity: The Role of Luminosity
VL  - 7
IS  - 1
SP  - 4
DO  - 10.3390/atoms7010004
ER  - 

@article{
author = "Borka Jovanović, Vesna and Jovanović, Predrag and Borka, Duško and Capozziello, Salvatore",
year = "2018",
abstract = "The global properties of elliptical galaxies are connected through the so-called fundamental plane of ellipticals, which is an empirical relation between their parameters: effective radius, central velocity dispersion and mean surface brightness within the effective radius. We investigated the relation between the parameters of the fundamental plane equation and the parameters of modified gravity potential f ( R ) . With that aim, we compared theoretical predictions for circular velocity in f ( R ) gravity with the corresponding values from a large sample of observed elliptical galaxies. Besides, we consistently reproduced the values of coefficients of the fundamental plane equation as deduced from observations, showing that the photometric quantities like mean surface brightness are related to gravitational parameters. We show that this type of modified gravity, especially its power-law version— R n , is able to reproduce the stellar dynamics in elliptical galaxies. In addition, it is shown that R n gravity fits the observations very well, without the need for a dark matter.",
journal = "Atoms",
title = "Fundamental Plane of Elliptical Galaxies in f(R) Gravity: The Role of Luminosity",
volume = "7",
number = "1",
pages = "4",
doi = "10.3390/atoms7010004"
}

Borka Jovanović, V., Jovanović, P., Borka, D.,& Capozziello, S.. (2018). Fundamental Plane of Elliptical Galaxies in f(R) Gravity: The Role of Luminosity. in Atoms, 7(1), 4.
https://doi.org/10.3390/atoms7010004

Borka Jovanović V, Jovanović P, Borka D, Capozziello S. Fundamental Plane of Elliptical Galaxies in f(R) Gravity: The Role of Luminosity. in Atoms. 2018;7(1):4.
doi:10.3390/atoms7010004 .

Borka Jovanović, Vesna, Jovanović, Predrag, Borka, Duško, Capozziello, Salvatore, "Fundamental Plane of Elliptical Galaxies in f(R) Gravity: The Role of Luminosity" in Atoms, 7, no. 1 (2018):4,
https://doi.org/10.3390/atoms7010004 . .

TY  - CONF
AU  - Zakharov, Alexander F.
AU  - Jovanović, Predrag
AU  - Borka, Duško
AU  - Borka Jovanović, Vesna
PY  - 2017
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/7166
AB  - One could use trajectories of test particles to evaluate a gravitational potential. In particular, in the case of the Galactic Center one could use photon trajectories to analyze a shadow structure. Another way is to use bright stars near the Galactic Center to evaluate a gravitational potential and constrain parameters of a model for the Galactic Center. In particular, one could obtain constraints on parameters of black hole, stellar cluster and dark matter concentration. Earlier, we constrained parameters of Fr and a Yukawa potential from observational data for the S2 star trajectory. Now gravity theories with a massive graviton are a subject of intensive studies. People proposed different experimental ways to evaluate a graviton mass. Recently, the joint LIGO and VIRGO collaboration reported not only a discovery of gravitational waves and binary black holes, but the team claimed also that found a constraint on a graviton mass as 1.2 x 10(-22) eV. We show that an analysis of the S2 star trajectory could constrain a graviton mass with a comparable accuracy and this constraint is consistent with LIGOs one.
C3  - Journal of Physics: Conference Series
T1  - Graviton mass evaluation with trajectories of bright stars at the Galactic Center
VL  - 798
DO  - 10.1088/1742-6596/798/1/012081
ER  - 

@conference{
author = "Zakharov, Alexander F. and Jovanović, Predrag and Borka, Duško and Borka Jovanović, Vesna",
year = "2017",
abstract = "One could use trajectories of test particles to evaluate a gravitational potential. In particular, in the case of the Galactic Center one could use photon trajectories to analyze a shadow structure. Another way is to use bright stars near the Galactic Center to evaluate a gravitational potential and constrain parameters of a model for the Galactic Center. In particular, one could obtain constraints on parameters of black hole, stellar cluster and dark matter concentration. Earlier, we constrained parameters of Fr and a Yukawa potential from observational data for the S2 star trajectory. Now gravity theories with a massive graviton are a subject of intensive studies. People proposed different experimental ways to evaluate a graviton mass. Recently, the joint LIGO and VIRGO collaboration reported not only a discovery of gravitational waves and binary black holes, but the team claimed also that found a constraint on a graviton mass as 1.2 x 10(-22) eV. We show that an analysis of the S2 star trajectory could constrain a graviton mass with a comparable accuracy and this constraint is consistent with LIGOs one.",
journal = "Journal of Physics: Conference Series",
title = "Graviton mass evaluation with trajectories of bright stars at the Galactic Center",
volume = "798",
doi = "10.1088/1742-6596/798/1/012081"
}

Zakharov, A. F., Jovanović, P., Borka, D.,& Borka Jovanović, V.. (2017). Graviton mass evaluation with trajectories of bright stars at the Galactic Center. in Journal of Physics: Conference Series, 798.
https://doi.org/10.1088/1742-6596/798/1/012081

Zakharov AF, Jovanović P, Borka D, Borka Jovanović V. Graviton mass evaluation with trajectories of bright stars at the Galactic Center. in Journal of Physics: Conference Series. 2017;798.
doi:10.1088/1742-6596/798/1/012081 .

Zakharov, Alexander F., Jovanović, Predrag, Borka, Duško, Borka Jovanović, Vesna, "Graviton mass evaluation with trajectories of bright stars at the Galactic Center" in Journal of Physics: Conference Series, 798 (2017),
https://doi.org/10.1088/1742-6596/798/1/012081 . .

TY  - CONF
AU  - Zakharov, Alexander F.
AU  - Jovanović, Predrag
AU  - Borka, Duško
AU  - Borka Jovanović, Vesna
PY  - 2017
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/7172
AB  - In February 2016 the LIGO and VIRGO collaboration reported the discovery of gravitational waves in merging black holes, therefore, the team confirmed GR predictions about an existence of black holes and gravitational waves in the strong gravitational field limit. Moreover, in their papers the joint LIGO and VIRGO team presented an upper limit on graviton mass such as m(g) LT 1.2 x 10(-22) eV (Abbott et al. 2016). So, the authors concluded that their observational data do not show any violation of classical general relativity. We show that an analysis of bright star trajectories could constrain graviton mass with a comparable accuracy with accuracies reached with gravitational wave interferometers and the estimate is consistent with the one obtained by the LIGO and VIRGO collaboration. This analysis gives an opportunity to treat observations of bright stars near the Galactic Center as a useful tool to obtain constraints on the fundamental gravity law such as modifications of the Newton gravity law in a weak field approximation. In that way, based on a potential reconstruction at the Galactic Center we obtain bounds on a graviton mass.
C3  - EPJ Web of Conferences
T1  - Graviton mass bounds from an analysis of bright star trajectories at the Galactic Center
VL  - 138
SP  - UNSP 01010
DO  - 10.1051/epjconf/201713801010
ER  - 

@conference{
author = "Zakharov, Alexander F. and Jovanović, Predrag and Borka, Duško and Borka Jovanović, Vesna",
year = "2017",
abstract = "In February 2016 the LIGO and VIRGO collaboration reported the discovery of gravitational waves in merging black holes, therefore, the team confirmed GR predictions about an existence of black holes and gravitational waves in the strong gravitational field limit. Moreover, in their papers the joint LIGO and VIRGO team presented an upper limit on graviton mass such as m(g) LT 1.2 x 10(-22) eV (Abbott et al. 2016). So, the authors concluded that their observational data do not show any violation of classical general relativity. We show that an analysis of bright star trajectories could constrain graviton mass with a comparable accuracy with accuracies reached with gravitational wave interferometers and the estimate is consistent with the one obtained by the LIGO and VIRGO collaboration. This analysis gives an opportunity to treat observations of bright stars near the Galactic Center as a useful tool to obtain constraints on the fundamental gravity law such as modifications of the Newton gravity law in a weak field approximation. In that way, based on a potential reconstruction at the Galactic Center we obtain bounds on a graviton mass.",
journal = "EPJ Web of Conferences",
title = "Graviton mass bounds from an analysis of bright star trajectories at the Galactic Center",
volume = "138",
pages = "UNSP 01010",
doi = "10.1051/epjconf/201713801010"
}

Zakharov, A. F., Jovanović, P., Borka, D.,& Borka Jovanović, V.. (2017). Graviton mass bounds from an analysis of bright star trajectories at the Galactic Center. in EPJ Web of Conferences, 138, UNSP 01010.
https://doi.org/10.1051/epjconf/201713801010

Zakharov AF, Jovanović P, Borka D, Borka Jovanović V. Graviton mass bounds from an analysis of bright star trajectories at the Galactic Center. in EPJ Web of Conferences. 2017;138:UNSP 01010.
doi:10.1051/epjconf/201713801010 .

Zakharov, Alexander F., Jovanović, Predrag, Borka, Duško, Borka Jovanović, Vesna, "Graviton mass bounds from an analysis of bright star trajectories at the Galactic Center" in EPJ Web of Conferences, 138 (2017):UNSP 01010,
https://doi.org/10.1051/epjconf/201713801010 . .

TY  - JOUR
AU  - Borka, Duško
AU  - Borka Jovanović, Vesna
AU  - Jovanović, Predrag
AU  - Capozziello, Salvatore
PY  - 2017
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/11897
AB  - We investigate the possibility to explain theoretically the S2 star orbital precession around the massive object at Galactic Centre using Extended Theories of Gravity, specifically f(R, φ) a Sanders-like gravitational potential in total absence of dark matter. To this aim an analytic fourth-order theory of gravity, non-minimally coupled with a massive scalar field is considered. The interaction term is given by an analytic functions f(R, φ) where R is the Ricci scalar and φ is the scalar field. We simulated orbit of S2 star around Galactic Centre in Sanders-like gravity potentials and compared it with NTT/VLT observations. We presented maps of reduced χ 2 over the {α − mφ} parameter space in the case of NTT/VLT observations. The approach we are proposing seems reliable to constrain modified gravity models at astronomical level.
T2  - Publications of the Astronomical Observatory of Belgrade
T1  - Constraints on f(R, ɸ) (Sanders-Like) Gravity Potential From Orbit of S2 Star
IS  - 96
SP  - 205
EP  - 210
UR  - https://hdl.handle.net/21.15107/rcub_vinar_11897
ER  - 

@article{
author = "Borka, Duško and Borka Jovanović, Vesna and Jovanović, Predrag and Capozziello, Salvatore",
year = "2017",
abstract = "We investigate the possibility to explain theoretically the S2 star orbital precession around the massive object at Galactic Centre using Extended Theories of Gravity, specifically f(R, φ) a Sanders-like gravitational potential in total absence of dark matter. To this aim an analytic fourth-order theory of gravity, non-minimally coupled with a massive scalar field is considered. The interaction term is given by an analytic functions f(R, φ) where R is the Ricci scalar and φ is the scalar field. We simulated orbit of S2 star around Galactic Centre in Sanders-like gravity potentials and compared it with NTT/VLT observations. We presented maps of reduced χ 2 over the {α − mφ} parameter space in the case of NTT/VLT observations. The approach we are proposing seems reliable to constrain modified gravity models at astronomical level.",
journal = "Publications of the Astronomical Observatory of Belgrade",
title = "Constraints on f(R, ɸ) (Sanders-Like) Gravity Potential From Orbit of S2 Star",
number = "96",
pages = "205-210",
url = "https://hdl.handle.net/21.15107/rcub_vinar_11897"
}

Borka, D., Borka Jovanović, V., Jovanović, P.,& Capozziello, S.. (2017). Constraints on f(R, ɸ) (Sanders-Like) Gravity Potential From Orbit of S2 Star. in Publications of the Astronomical Observatory of Belgrade(96), 205-210.
https://hdl.handle.net/21.15107/rcub_vinar_11897

Borka D, Borka Jovanović V, Jovanović P, Capozziello S. Constraints on f(R, ɸ) (Sanders-Like) Gravity Potential From Orbit of S2 Star. in Publications of the Astronomical Observatory of Belgrade. 2017;(96):205-210.
https://hdl.handle.net/21.15107/rcub_vinar_11897 .

Borka, Duško, Borka Jovanović, Vesna, Jovanović, Predrag, Capozziello, Salvatore, "Constraints on f(R, ɸ) (Sanders-Like) Gravity Potential From Orbit of S2 Star" in Publications of the Astronomical Observatory of Belgrade, no. 96 (2017):205-210,
https://hdl.handle.net/21.15107/rcub_vinar_11897 .

TY  - JOUR
AU  - Borka Jovanović, Vesna
AU  - Borka, Duško
AU  - Jovanović, Predrag
PY  - 2017
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/11899
AB  - We use all-sky surveys at 408 and 1420 MHz with aim to investigate properties of the Galactic radio source Lupus Loop. We estimate the brightness temperature, surface brightness and radio spectral index of this supernova remnant using the method we have developed. The non-thermal nature of its radiation is confirmed, and also the distribution of spectral index over its area is given.
T2  - Publications of the Astronomical Observatory of Belgrade
T1  - Distribution of radio spectral index over the Lupus loop
IS  - 96
SP  - 211
EP  - 215
UR  - https://hdl.handle.net/21.15107/rcub_vinar_11899
ER  - 

@article{
author = "Borka Jovanović, Vesna and Borka, Duško and Jovanović, Predrag",
year = "2017",
abstract = "We use all-sky surveys at 408 and 1420 MHz with aim to investigate properties of the Galactic radio source Lupus Loop. We estimate the brightness temperature, surface brightness and radio spectral index of this supernova remnant using the method we have developed. The non-thermal nature of its radiation is confirmed, and also the distribution of spectral index over its area is given.",
journal = "Publications of the Astronomical Observatory of Belgrade",
title = "Distribution of radio spectral index over the Lupus loop",
number = "96",
pages = "211-215",
url = "https://hdl.handle.net/21.15107/rcub_vinar_11899"
}

Borka Jovanović, V., Borka, D.,& Jovanović, P.. (2017). Distribution of radio spectral index over the Lupus loop. in Publications of the Astronomical Observatory of Belgrade(96), 211-215.
https://hdl.handle.net/21.15107/rcub_vinar_11899

Borka Jovanović V, Borka D, Jovanović P. Distribution of radio spectral index over the Lupus loop. in Publications of the Astronomical Observatory of Belgrade. 2017;(96):211-215.
https://hdl.handle.net/21.15107/rcub_vinar_11899 .

Borka Jovanović, Vesna, Borka, Duško, Jovanović, Predrag, "Distribution of radio spectral index over the Lupus loop" in Publications of the Astronomical Observatory of Belgrade, no. 96 (2017):211-215,
https://hdl.handle.net/21.15107/rcub_vinar_11899 .

TY  - JOUR
AU  - Capozziello, Salvatore
AU  - Jovanović, Predrag
AU  - Borka Jovanović, Vesna
AU  - Borka, Duško
PY  - 2017
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/1696
AB  - We demonstrate that the existence of a Noether symmetry in f theories of gravity gives rise to a further gravitational radius, besides tile standard Schwarzschild one, determining the dynamics at galactic scales. By this feature, it is possible to explain the baryonic Fully-Fisher relation and the rotation curve of gas-rich galaxies without the dark matter hypothesis.
T2  - Journal of Cosmology and Astroparticle Physics
T1  - Addressing the missing matter problem in galaxies through a new fundamental gravitational radius
IS  - 6
DO  - 10.1088/1475-7516/2017/06/044
ER  - 

@article{
author = "Capozziello, Salvatore and Jovanović, Predrag and Borka Jovanović, Vesna and Borka, Duško",
year = "2017",
abstract = "We demonstrate that the existence of a Noether symmetry in f theories of gravity gives rise to a further gravitational radius, besides tile standard Schwarzschild one, determining the dynamics at galactic scales. By this feature, it is possible to explain the baryonic Fully-Fisher relation and the rotation curve of gas-rich galaxies without the dark matter hypothesis.",
journal = "Journal of Cosmology and Astroparticle Physics",
title = "Addressing the missing matter problem in galaxies through a new fundamental gravitational radius",
number = "6",
doi = "10.1088/1475-7516/2017/06/044"
}

Capozziello, S., Jovanović, P., Borka Jovanović, V.,& Borka, D.. (2017). Addressing the missing matter problem in galaxies through a new fundamental gravitational radius. in Journal of Cosmology and Astroparticle Physics(6).
https://doi.org/10.1088/1475-7516/2017/06/044

Capozziello S, Jovanović P, Borka Jovanović V, Borka D. Addressing the missing matter problem in galaxies through a new fundamental gravitational radius. in Journal of Cosmology and Astroparticle Physics. 2017;(6).
doi:10.1088/1475-7516/2017/06/044 .

Capozziello, Salvatore, Jovanović, Predrag, Borka Jovanović, Vesna, Borka, Duško, "Addressing the missing matter problem in galaxies through a new fundamental gravitational radius" in Journal of Cosmology and Astroparticle Physics, no. 6 (2017),
https://doi.org/10.1088/1475-7516/2017/06/044 . .

TY  - JOUR
AU  - Borka Jovanović, Vesna
AU  - Jovanović, Predrag
AU  - Borka, Duško
PY  - 2017
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/1496
AB  - We use radio-continuum all-sky surveys at 1420 and 408 MHz with the aim to investigate properties of the Galactic radio source Lupus Loop. The survey data at 1435 MHz, with the linear polarization of the southern sky, are also used. We calculate properties of this supernova remnant: the brightness temperature, surface brightness and radio spectral index. To determine its borders and to calculate its properties, we use the method we have developed. The non-thermal nature of its radiation is confirmed. The distribution of spectral index over its area is also given. A significant correlation between the radio spectral index distribution and the corresponding polarized intensity distribution inside the loop borders is found, indicating that the polarization maps could provide us information about the distribution of the interstellar medium, and thus could represent one additional way to search for new Galactic loops.
T2  - Revista Mexicana de Astronomia y Astrofisica
T1  - Snr Radio Spectral Index Distribution and Its Correlation with Polarization. a Case Study: the Lupus Loop
VL  - 53
IS  - 1
SP  - 37
EP  - 44
UR  - https://hdl.handle.net/21.15107/rcub_vinar_1496
ER  - 

@article{
author = "Borka Jovanović, Vesna and Jovanović, Predrag and Borka, Duško",
year = "2017",
abstract = "We use radio-continuum all-sky surveys at 1420 and 408 MHz with the aim to investigate properties of the Galactic radio source Lupus Loop. The survey data at 1435 MHz, with the linear polarization of the southern sky, are also used. We calculate properties of this supernova remnant: the brightness temperature, surface brightness and radio spectral index. To determine its borders and to calculate its properties, we use the method we have developed. The non-thermal nature of its radiation is confirmed. The distribution of spectral index over its area is also given. A significant correlation between the radio spectral index distribution and the corresponding polarized intensity distribution inside the loop borders is found, indicating that the polarization maps could provide us information about the distribution of the interstellar medium, and thus could represent one additional way to search for new Galactic loops.",
journal = "Revista Mexicana de Astronomia y Astrofisica",
title = "Snr Radio Spectral Index Distribution and Its Correlation with Polarization. a Case Study: the Lupus Loop",
volume = "53",
number = "1",
pages = "37-44",
url = "https://hdl.handle.net/21.15107/rcub_vinar_1496"
}

Borka Jovanović, V., Jovanović, P.,& Borka, D.. (2017). Snr Radio Spectral Index Distribution and Its Correlation with Polarization. a Case Study: the Lupus Loop. in Revista Mexicana de Astronomia y Astrofisica, 53(1), 37-44.
https://hdl.handle.net/21.15107/rcub_vinar_1496

Borka Jovanović V, Jovanović P, Borka D. Snr Radio Spectral Index Distribution and Its Correlation with Polarization. a Case Study: the Lupus Loop. in Revista Mexicana de Astronomia y Astrofisica. 2017;53(1):37-44.
https://hdl.handle.net/21.15107/rcub_vinar_1496 .

Borka Jovanović, Vesna, Jovanović, Predrag, Borka, Duško, "Snr Radio Spectral Index Distribution and Its Correlation with Polarization. a Case Study: the Lupus Loop" in Revista Mexicana de Astronomia y Astrofisica, 53, no. 1 (2017):37-44,
https://hdl.handle.net/21.15107/rcub_vinar_1496 .

TY  - CONF
AU  - Zakharov, Alexander F.
AU  - Jovanović, Predrag
AU  - Borka, Duško
AU  - Borka Jovanović, Vesna
PY  - 2016
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/7119
AB  - Scientists worked in Saint-Petersburg (Petrograd, Leningrad) played the extremely important role in creation of scientific school and development of general relativity in Russia. Very recently LIGO collaboration discovered gravitational waves [1] predicted 100 years ago by A. Einstein. In the papers reporting about this discovery, the joint LIGO and VIRGO team presented an upper limit on graviton mass such as m(g) LT 1.2 x 10(-22) eV [1, 2]. The authors concluded that their observational data do not show violations of classical general relativity because the graviton mass limit is very small. We show that an analysis of bright star trajectories could bound graviton mass with a comparable accuracy with accuracies reached with gravitational wave interferometers and expected with forthcoming pulsar timing observations for gravitational wave detection. This analysis gives an opportunity to treat observations of bright stars near the Galactic Center as a tool for an evaluation specific parameters of the black hole and also to obtain constraints on the fundamental gravity law such as a modifications of Newton gravity law in a weak field approximation. In that way, based on a potential reconstruction at the Galactic Center we give a bounds on a graviton mass.
C3  - EPJ Web of Conferences
T1  - Trajectories of bright stars at the Galactic Center as a tool to evaluate a graviton mass
VL  - 125
DO  - 10.1051/epjconf/201612501011
ER  - 

@conference{
author = "Zakharov, Alexander F. and Jovanović, Predrag and Borka, Duško and Borka Jovanović, Vesna",
year = "2016",
abstract = "Scientists worked in Saint-Petersburg (Petrograd, Leningrad) played the extremely important role in creation of scientific school and development of general relativity in Russia. Very recently LIGO collaboration discovered gravitational waves [1] predicted 100 years ago by A. Einstein. In the papers reporting about this discovery, the joint LIGO and VIRGO team presented an upper limit on graviton mass such as m(g) LT 1.2 x 10(-22) eV [1, 2]. The authors concluded that their observational data do not show violations of classical general relativity because the graviton mass limit is very small. We show that an analysis of bright star trajectories could bound graviton mass with a comparable accuracy with accuracies reached with gravitational wave interferometers and expected with forthcoming pulsar timing observations for gravitational wave detection. This analysis gives an opportunity to treat observations of bright stars near the Galactic Center as a tool for an evaluation specific parameters of the black hole and also to obtain constraints on the fundamental gravity law such as a modifications of Newton gravity law in a weak field approximation. In that way, based on a potential reconstruction at the Galactic Center we give a bounds on a graviton mass.",
journal = "EPJ Web of Conferences",
title = "Trajectories of bright stars at the Galactic Center as a tool to evaluate a graviton mass",
volume = "125",
doi = "10.1051/epjconf/201612501011"
}

Zakharov, A. F., Jovanović, P., Borka, D.,& Borka Jovanović, V.. (2016). Trajectories of bright stars at the Galactic Center as a tool to evaluate a graviton mass. in EPJ Web of Conferences, 125.
https://doi.org/10.1051/epjconf/201612501011

Zakharov AF, Jovanović P, Borka D, Borka Jovanović V. Trajectories of bright stars at the Galactic Center as a tool to evaluate a graviton mass. in EPJ Web of Conferences. 2016;125.
doi:10.1051/epjconf/201612501011 .

Zakharov, Alexander F., Jovanović, Predrag, Borka, Duško, Borka Jovanović, Vesna, "Trajectories of bright stars at the Galactic Center as a tool to evaluate a graviton mass" in EPJ Web of Conferences, 125 (2016),
https://doi.org/10.1051/epjconf/201612501011 . .

TY  - JOUR
AU  - Borka Jovanović, Vesna
AU  - Capozziello, Salvatore
AU  - Jovanović, Predrag
AU  - Borka, Duško
PY  - 2016
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/1408
AB  - The fundamental plane (FP) of galaxies can be recovered in the framework of f (R) gravity avoiding the issues related to dark matter to fit the observations. In particular, the power-law version f (R) proportional to R-n, resulting from the existence of Noether symmetries for f (R), is sufficient to implement the approach. In fact, relations between the FP parameters and the corrected Newtonian potential, coming from Rn, can be found and justified from a physical point of view. Specifically, we analyze the velocity distribution of elliptical galaxies and obtain that r(c), the scale-length depending on the gravitational system properties, is proportional to re, the galaxy effective radius. This fact points out that the gravitational corrections induced by f (R) can lead photometry and dynamics of the system. Furthermore, the main byproduct of such an approach is that gravity could work in different ways depending on the scales of self-gravitating systems. (C) 2016 Elsevier B.V. All rights reserved.
T2  - Physics of the Dark Universe
T1  - Recovering the fundamental plane of galaxies by f (R) gravity
VL  - 14
SP  - 73
EP  - 83
DO  - 10.1016/j.dark.2016.10.003
ER  - 

@article{
author = "Borka Jovanović, Vesna and Capozziello, Salvatore and Jovanović, Predrag and Borka, Duško",
year = "2016",
abstract = "The fundamental plane (FP) of galaxies can be recovered in the framework of f (R) gravity avoiding the issues related to dark matter to fit the observations. In particular, the power-law version f (R) proportional to R-n, resulting from the existence of Noether symmetries for f (R), is sufficient to implement the approach. In fact, relations between the FP parameters and the corrected Newtonian potential, coming from Rn, can be found and justified from a physical point of view. Specifically, we analyze the velocity distribution of elliptical galaxies and obtain that r(c), the scale-length depending on the gravitational system properties, is proportional to re, the galaxy effective radius. This fact points out that the gravitational corrections induced by f (R) can lead photometry and dynamics of the system. Furthermore, the main byproduct of such an approach is that gravity could work in different ways depending on the scales of self-gravitating systems. (C) 2016 Elsevier B.V. All rights reserved.",
journal = "Physics of the Dark Universe",
title = "Recovering the fundamental plane of galaxies by f (R) gravity",
volume = "14",
pages = "73-83",
doi = "10.1016/j.dark.2016.10.003"
}

Borka Jovanović, V., Capozziello, S., Jovanović, P.,& Borka, D.. (2016). Recovering the fundamental plane of galaxies by f (R) gravity. in Physics of the Dark Universe, 14, 73-83.
https://doi.org/10.1016/j.dark.2016.10.003

Borka Jovanović V, Capozziello S, Jovanović P, Borka D. Recovering the fundamental plane of galaxies by f (R) gravity. in Physics of the Dark Universe. 2016;14:73-83.
doi:10.1016/j.dark.2016.10.003 .

Borka Jovanović, Vesna, Capozziello, Salvatore, Jovanović, Predrag, Borka, Duško, "Recovering the fundamental plane of galaxies by f (R) gravity" in Physics of the Dark Universe, 14 (2016):73-83,
https://doi.org/10.1016/j.dark.2016.10.003 . .

TY  - JOUR
AU  - Zakharov, Alexander F.
AU  - Jovanović, Predrag
AU  - Borka, Duško
AU  - Borka Jovanović, Vesna
PY  - 2016
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/1125
AB  - Recently LIGO collaboration discovered gravitational waves [1] predicted 100 years ago by A. Einstein. Moreover, in the key paper reporting about the discovery, the joint LIGO and VIRGO team presented an upper limit on graviton mass such as m(g) LT 1.2 x 10(-22)eV [1] (see also more details in another LIGO paper [2] dedicated to a data analysis to obtain such a small constraint on a graviton mass). Since the graviton mass limit is so small the authors concluded that their observational data do not show violations of classical general relativity. We consider another opportunity to evaluate a graviton mass from phenomenological consequences of massive gravity and show that an analysis of bright star trajectories could bound graviton mass with a comparable accuracy with accuracies reached with gravitational wave interferometers and expected with forthcoming pulsar timing observations for gravitational wave detection. It gives an opportunity to treat observations of bright stars near the Galactic Center as a wonderful tool not only for an evaluation specific parameters of the black hole but also to obtain constraints on the fundamental gravity law such as a modifications of Newton gravity law in a weak field approximation. In particular, we obtain bounds on a graviton mass based on a potential reconstruction at the Galactic Center.
T2  - Journal of Cosmology and Astroparticle Physics
T1  - Constraining the range of Yukawa gravity interaction from S2 star orbits II: bounds on graviton mass
IS  - 5
DO  - 10.1088/1475-7516/2016/05/045
ER  - 

@article{
author = "Zakharov, Alexander F. and Jovanović, Predrag and Borka, Duško and Borka Jovanović, Vesna",
year = "2016",
abstract = "Recently LIGO collaboration discovered gravitational waves [1] predicted 100 years ago by A. Einstein. Moreover, in the key paper reporting about the discovery, the joint LIGO and VIRGO team presented an upper limit on graviton mass such as m(g) LT 1.2 x 10(-22)eV [1] (see also more details in another LIGO paper [2] dedicated to a data analysis to obtain such a small constraint on a graviton mass). Since the graviton mass limit is so small the authors concluded that their observational data do not show violations of classical general relativity. We consider another opportunity to evaluate a graviton mass from phenomenological consequences of massive gravity and show that an analysis of bright star trajectories could bound graviton mass with a comparable accuracy with accuracies reached with gravitational wave interferometers and expected with forthcoming pulsar timing observations for gravitational wave detection. It gives an opportunity to treat observations of bright stars near the Galactic Center as a wonderful tool not only for an evaluation specific parameters of the black hole but also to obtain constraints on the fundamental gravity law such as a modifications of Newton gravity law in a weak field approximation. In particular, we obtain bounds on a graviton mass based on a potential reconstruction at the Galactic Center.",
journal = "Journal of Cosmology and Astroparticle Physics",
title = "Constraining the range of Yukawa gravity interaction from S2 star orbits II: bounds on graviton mass",
number = "5",
doi = "10.1088/1475-7516/2016/05/045"
}

Zakharov, A. F., Jovanović, P., Borka, D.,& Borka Jovanović, V.. (2016). Constraining the range of Yukawa gravity interaction from S2 star orbits II: bounds on graviton mass. in Journal of Cosmology and Astroparticle Physics(5).
https://doi.org/10.1088/1475-7516/2016/05/045

Zakharov AF, Jovanović P, Borka D, Borka Jovanović V. Constraining the range of Yukawa gravity interaction from S2 star orbits II: bounds on graviton mass. in Journal of Cosmology and Astroparticle Physics. 2016;(5).
doi:10.1088/1475-7516/2016/05/045 .

Zakharov, Alexander F., Jovanović, Predrag, Borka, Duško, Borka Jovanović, Vesna, "Constraining the range of Yukawa gravity interaction from S2 star orbits II: bounds on graviton mass" in Journal of Cosmology and Astroparticle Physics, no. 5 (2016),
https://doi.org/10.1088/1475-7516/2016/05/045 . .

TY  - JOUR
AU  - Borka, Duško
AU  - Capozziello, Salvatore
AU  - Jovanović, Predrag
AU  - Borka Jovanović, Vesna
PY  - 2016
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/1070
AB  - We consider possible signatures for the so called hybrid gravity within the Galactic Central Parsec. This modified theory of gravity consists of a superposition of the metric Einstein-Hilbert Lagrangian with an f(R) term constructed a la Palatini and can be easily reduced to an equivalent scalar-tensor theory. Such an approach is introduced in order to cure the shortcomings related to f(R) gravity, in general formulated either in metric or in metric-affine frameworks. Hybrid gravity allows to disentangle the further gravitational degrees of freedom with respect to those of standard General Relativity. The present analysis is based on the S2 star orbital precession around the massive compact dark object at the Galactic Center where the simulated orbits in hybrid modified gravity are compared with astronomical observations. These simulations result with constraints on the range of hybrid gravity interaction parameter phi(0), showing that in the case of S2 star it is between -0.0009 and -0.0002. At the same time, we are also able to obtain the constraints on the effective mass parameter m(phi), and found that it is between -0.0034 and -0.0025 AU(-1) for S2 star. Furthermore, the hybrid gravity potential induces precession of S2 star orbit in the same direction as General Relativity. In previous papers, we considered other types of extended gravities, like metric power law f(R)proportional to R-n gravity, inducing Yukawa and Sanders-like gravitational potentials, but it seems that hybrid gravity is the best among these models to explain different gravitational phenomena at different astronomical scales. (C) 2016 Elsevier B.V. All rights reserved.
PB  - Elsevier
T2  - Astroparticle Physics
T1  - Probing hybrid modified gravity by stellar motion around Galactic Center
VL  - 79
SP  - 41
EP  - 48
DO  - 10.1016/j.astropartphys.2016.03.002
ER  - 

@article{
author = "Borka, Duško and Capozziello, Salvatore and Jovanović, Predrag and Borka Jovanović, Vesna",
year = "2016",
abstract = "We consider possible signatures for the so called hybrid gravity within the Galactic Central Parsec. This modified theory of gravity consists of a superposition of the metric Einstein-Hilbert Lagrangian with an f(R) term constructed a la Palatini and can be easily reduced to an equivalent scalar-tensor theory. Such an approach is introduced in order to cure the shortcomings related to f(R) gravity, in general formulated either in metric or in metric-affine frameworks. Hybrid gravity allows to disentangle the further gravitational degrees of freedom with respect to those of standard General Relativity. The present analysis is based on the S2 star orbital precession around the massive compact dark object at the Galactic Center where the simulated orbits in hybrid modified gravity are compared with astronomical observations. These simulations result with constraints on the range of hybrid gravity interaction parameter phi(0), showing that in the case of S2 star it is between -0.0009 and -0.0002. At the same time, we are also able to obtain the constraints on the effective mass parameter m(phi), and found that it is between -0.0034 and -0.0025 AU(-1) for S2 star. Furthermore, the hybrid gravity potential induces precession of S2 star orbit in the same direction as General Relativity. In previous papers, we considered other types of extended gravities, like metric power law f(R)proportional to R-n gravity, inducing Yukawa and Sanders-like gravitational potentials, but it seems that hybrid gravity is the best among these models to explain different gravitational phenomena at different astronomical scales. (C) 2016 Elsevier B.V. All rights reserved.",
publisher = "Elsevier",
journal = "Astroparticle Physics",
title = "Probing hybrid modified gravity by stellar motion around Galactic Center",
volume = "79",
pages = "41-48",
doi = "10.1016/j.astropartphys.2016.03.002"
}

Borka, D., Capozziello, S., Jovanović, P.,& Borka Jovanović, V.. (2016). Probing hybrid modified gravity by stellar motion around Galactic Center. in Astroparticle Physics
Elsevier., 79, 41-48.
https://doi.org/10.1016/j.astropartphys.2016.03.002

Borka D, Capozziello S, Jovanović P, Borka Jovanović V. Probing hybrid modified gravity by stellar motion around Galactic Center. in Astroparticle Physics. 2016;79:41-48.
doi:10.1016/j.astropartphys.2016.03.002 .

Borka, Duško, Capozziello, Salvatore, Jovanović, Predrag, Borka Jovanović, Vesna, "Probing hybrid modified gravity by stellar motion around Galactic Center" in Astroparticle Physics, 79 (2016):41-48,
https://doi.org/10.1016/j.astropartphys.2016.03.002 . .

TY  - JOUR
AU  - Jovanović, Predrag
AU  - Borka Jovanović, Vesna
AU  - Borka, Duško
AU  - Popović, Luka C. 
PY  - 2016
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/952
AB  - Here we present a short overview and main results of our investigations of several effects which can induce shifts in the broad Fe K alpha line emitted from relativistic accretion disks around single and binary supermassive black holes. We used numerical simulations based on ray-tracing method in the Kerr metric to study the role of classical Doppler shift, special relativistic transverse Doppler shift and Doppler beaming, general relativistic gravitational red-shift, and perturbations of the disk emissivity in the formation of the observed Fe K alpha line profiles. Besides, we also investigated whether the observed line profiles from the binary systems of supermassive black holes could be affected by the Doppler shifts due to dynamics of such systems. The presented results demonstrate that all these effects could have a significant influence on the observed profiles of the broad Fe K alpha line emitted from relativistic accretion disks around single and binary supermassive black holes.
PB  - Springer
T2  - Astrophysics and Space Science
T1  - Line shifts in accretion disks-the case of Fe K alpha
VL  - 361
IS  - 2
DO  - 10.1007/s10509-016-2653-z
ER  - 

@article{
author = "Jovanović, Predrag and Borka Jovanović, Vesna and Borka, Duško and Popović, Luka C. ",
year = "2016",
abstract = "Here we present a short overview and main results of our investigations of several effects which can induce shifts in the broad Fe K alpha line emitted from relativistic accretion disks around single and binary supermassive black holes. We used numerical simulations based on ray-tracing method in the Kerr metric to study the role of classical Doppler shift, special relativistic transverse Doppler shift and Doppler beaming, general relativistic gravitational red-shift, and perturbations of the disk emissivity in the formation of the observed Fe K alpha line profiles. Besides, we also investigated whether the observed line profiles from the binary systems of supermassive black holes could be affected by the Doppler shifts due to dynamics of such systems. The presented results demonstrate that all these effects could have a significant influence on the observed profiles of the broad Fe K alpha line emitted from relativistic accretion disks around single and binary supermassive black holes.",
publisher = "Springer",
journal = "Astrophysics and Space Science",
title = "Line shifts in accretion disks-the case of Fe K alpha",
volume = "361",
number = "2",
doi = "10.1007/s10509-016-2653-z"
}

Jovanović, P., Borka Jovanović, V., Borka, D.,& Popović, L. C.. (2016). Line shifts in accretion disks-the case of Fe K alpha. in Astrophysics and Space Science
Springer., 361(2).
https://doi.org/10.1007/s10509-016-2653-z

Jovanović P, Borka Jovanović V, Borka D, Popović LC. Line shifts in accretion disks-the case of Fe K alpha. in Astrophysics and Space Science. 2016;361(2).
doi:10.1007/s10509-016-2653-z .

Jovanović, Predrag, Borka Jovanović, Vesna, Borka, Duško, Popović, Luka C. , "Line shifts in accretion disks-the case of Fe K alpha" in Astrophysics and Space Science, 361, no. 2 (2016),
https://doi.org/10.1007/s10509-016-2653-z . .

TY  - JOUR
AU  - Ignjatović, Siniša R.
AU  - Borka Jovanović, Vesna
PY  - 2014
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/10286
AB  - There are several kinds of exotic hadron states. In this paper, we are concerned with the flavor exotic meson states: the tetraquarks and meson molecules. Two distinct models of tetraquarks are studied: diquark-antidiquark bound states and uncorrelated quarks. Although diquark is not a color singlet, there is a strong theoretical evidence that such states do exist within hadrons. Both tetraquark models as well as methods used to study such states are reviewed. The meson-meson molecules are also mentioned. It is remarked that hadron spectroscopy per se may not always be sufficient to discern between physically distinct models.
T2  - Facta Universitatis, Series: Physics, Chemistry and Technology
T1  - On some models of the exotic hadron states
VL  - 12
IS  - 2
SP  - 151
EP  - 158
DO  - 10.2298/FUPCT1402151I
ER  - 

@article{
author = "Ignjatović, Siniša R. and Borka Jovanović, Vesna",
year = "2014",
abstract = "There are several kinds of exotic hadron states. In this paper, we are concerned with the flavor exotic meson states: the tetraquarks and meson molecules. Two distinct models of tetraquarks are studied: diquark-antidiquark bound states and uncorrelated quarks. Although diquark is not a color singlet, there is a strong theoretical evidence that such states do exist within hadrons. Both tetraquark models as well as methods used to study such states are reviewed. The meson-meson molecules are also mentioned. It is remarked that hadron spectroscopy per se may not always be sufficient to discern between physically distinct models.",
journal = "Facta Universitatis, Series: Physics, Chemistry and Technology",
title = "On some models of the exotic hadron states",
volume = "12",
number = "2",
pages = "151-158",
doi = "10.2298/FUPCT1402151I"
}

Ignjatović, S. R.,& Borka Jovanović, V.. (2014). On some models of the exotic hadron states. in Facta Universitatis, Series: Physics, Chemistry and Technology, 12(2), 151-158.
https://doi.org/10.2298/FUPCT1402151I

Ignjatović SR, Borka Jovanović V. On some models of the exotic hadron states. in Facta Universitatis, Series: Physics, Chemistry and Technology. 2014;12(2):151-158.
doi:10.2298/FUPCT1402151I .

Ignjatović, Siniša R., Borka Jovanović, Vesna, "On some models of the exotic hadron states" in Facta Universitatis, Series: Physics, Chemistry and Technology, 12, no. 2 (2014):151-158,
https://doi.org/10.2298/FUPCT1402151I . .

TY  - JOUR
AU  - Zakharov, Alexander F.
AU  - Borka, Duško
AU  - Borka Jovanović, Vesna
AU  - Jovanović, Predrag
PY  - 2014
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/8601
AB  - Here we investigate possible applications of observed stellar orbits around Galactic Center for constraining the R-n gravity at Galactic scales. For that purpose, we simulated orbits of S2-like stars around the massive black hole at Galactic Center, and study the constraints on the R-n gravity which could be obtained by the present and next generations of large telescopes. Our results show that R-n gravity affects the simulated orbits in the qualitatively similar way as a bulk distribution of matter (including a stellar cluster and dark matter distributions) in Newtons gravity. In the cases where the density of extended mass is higher, the maximum allowed value of parameter beta in R-n gravity is noticeably smaller, due to the fact that the both extended mass and R-n gravity cause the retrograde orbital precession. (C) 2014 COSPAR. Published by Elsevier Ltd. All rights reserved.
T2  - Advances in Space Research
T1  - Constraints on R-n gravity from precession of orbits of S2-like stars: A case of a bulk distribution of mass
VL  - 54
IS  - 6
SP  - 1108
EP  - 1112
DO  - 10.1016/j.asr.2014.05.027
ER  - 

@article{
author = "Zakharov, Alexander F. and Borka, Duško and Borka Jovanović, Vesna and Jovanović, Predrag",
year = "2014",
abstract = "Here we investigate possible applications of observed stellar orbits around Galactic Center for constraining the R-n gravity at Galactic scales. For that purpose, we simulated orbits of S2-like stars around the massive black hole at Galactic Center, and study the constraints on the R-n gravity which could be obtained by the present and next generations of large telescopes. Our results show that R-n gravity affects the simulated orbits in the qualitatively similar way as a bulk distribution of matter (including a stellar cluster and dark matter distributions) in Newtons gravity. In the cases where the density of extended mass is higher, the maximum allowed value of parameter beta in R-n gravity is noticeably smaller, due to the fact that the both extended mass and R-n gravity cause the retrograde orbital precession. (C) 2014 COSPAR. Published by Elsevier Ltd. All rights reserved.",
journal = "Advances in Space Research",
title = "Constraints on R-n gravity from precession of orbits of S2-like stars: A case of a bulk distribution of mass",
volume = "54",
number = "6",
pages = "1108-1112",
doi = "10.1016/j.asr.2014.05.027"
}

Zakharov, A. F., Borka, D., Borka Jovanović, V.,& Jovanović, P.. (2014). Constraints on R-n gravity from precession of orbits of S2-like stars: A case of a bulk distribution of mass. in Advances in Space Research, 54(6), 1108-1112.
https://doi.org/10.1016/j.asr.2014.05.027

Zakharov AF, Borka D, Borka Jovanović V, Jovanović P. Constraints on R-n gravity from precession of orbits of S2-like stars: A case of a bulk distribution of mass. in Advances in Space Research. 2014;54(6):1108-1112.
doi:10.1016/j.asr.2014.05.027 .

Zakharov, Alexander F., Borka, Duško, Borka Jovanović, Vesna, Jovanović, Predrag, "Constraints on R-n gravity from precession of orbits of S2-like stars: A case of a bulk distribution of mass" in Advances in Space Research, 54, no. 6 (2014):1108-1112,
https://doi.org/10.1016/j.asr.2014.05.027 . .

TY  - JOUR
AU  - Zakharov, Alexander F.
AU  - Borka, Duško
AU  - Borka Jovanović, Vesna
AU  - Jovanović, Predrag
PY  - 2014
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/96
AB  - Here we investigate possible applications of observed stellar orbits around Galactic Center for constraining the R-n gravity at Galactic scales. For that purpose, we simulated orbits of S2-like stars around the massive black hole at Galactic Center, and study the constraints on the R-n gravity which could be obtained by the present and next generations of large telescopes. Our results show that R-n gravity affects the simulated orbits in the qualitatively similar way as a bulk distribution of matter (including a stellar cluster and dark matter distributions) in Newtons gravity. In the cases where the density of extended mass is higher, the maximum allowed value of parameter beta in R-n gravity is noticeably smaller, due to the fact that the both extended mass and R-n gravity cause the retrograde orbital precession. (C) 2014 COSPAR. Published by Elsevier Ltd. All rights reserved.
T2  - Advances in Space Research
T1  - Constraints on R-n gravity from precession of orbits of S2-like stars: A case of a bulk distribution of mass
VL  - 54
IS  - 6
SP  - 1108
EP  - 1112
DO  - 10.1016/j.asr.2014.05.027
ER  - 

@article{
author = "Zakharov, Alexander F. and Borka, Duško and Borka Jovanović, Vesna and Jovanović, Predrag",
year = "2014",
abstract = "Here we investigate possible applications of observed stellar orbits around Galactic Center for constraining the R-n gravity at Galactic scales. For that purpose, we simulated orbits of S2-like stars around the massive black hole at Galactic Center, and study the constraints on the R-n gravity which could be obtained by the present and next generations of large telescopes. Our results show that R-n gravity affects the simulated orbits in the qualitatively similar way as a bulk distribution of matter (including a stellar cluster and dark matter distributions) in Newtons gravity. In the cases where the density of extended mass is higher, the maximum allowed value of parameter beta in R-n gravity is noticeably smaller, due to the fact that the both extended mass and R-n gravity cause the retrograde orbital precession. (C) 2014 COSPAR. Published by Elsevier Ltd. All rights reserved.",
journal = "Advances in Space Research",
title = "Constraints on R-n gravity from precession of orbits of S2-like stars: A case of a bulk distribution of mass",
volume = "54",
number = "6",
pages = "1108-1112",
doi = "10.1016/j.asr.2014.05.027"
}

Zakharov, A. F., Borka, D., Borka Jovanović, V.,& Jovanović, P.. (2014). Constraints on R-n gravity from precession of orbits of S2-like stars: A case of a bulk distribution of mass. in Advances in Space Research, 54(6), 1108-1112.
https://doi.org/10.1016/j.asr.2014.05.027

Zakharov AF, Borka D, Borka Jovanović V, Jovanović P. Constraints on R-n gravity from precession of orbits of S2-like stars: A case of a bulk distribution of mass. in Advances in Space Research. 2014;54(6):1108-1112.
doi:10.1016/j.asr.2014.05.027 .

Zakharov, Alexander F., Borka, Duško, Borka Jovanović, Vesna, Jovanović, Predrag, "Constraints on R-n gravity from precession of orbits of S2-like stars: A case of a bulk distribution of mass" in Advances in Space Research, 54, no. 6 (2014):1108-1112,
https://doi.org/10.1016/j.asr.2014.05.027 . .

TY  - JOUR
AU  - Jovanović, Predrag
AU  - Borka Jovanović, Vesna
AU  - Borka, Duško
AU  - Bogdanović, T.
PY  - 2014
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/160
AB  - We used a model of a relativistic accretion disk around a supermassive black hole (SMBH), based on ray-tracing method in the Kerr metric, to study the variations of the composite Fe K alpha line emitted from two accretion disks around SMBHs in a binary system. We assumed that the orbit of such a binary is approximately Keplerian, and simulated the composite line shapes for different orbital elements, accretion disk parameters and mass ratios of the components. The obtained results show that, if observed in the spectra of some SMBH binaries during their different orbital phases, such composite Fe K alpha line profiles could be used to constrain the orbits and several properties of such SMBH binaries. (C) 2013 COSPAR. Published by Elsevier Ltd. All rights reserved.
T2  - Advances in Space Research
T1  - Composite profile of the Fe K alpha spectral line emitted from a binary system of supermassive black holes
VL  - 54
IS  - 7
SP  - 1448
EP  - 1457
DO  - 10.1016/j.asr.2013.10.028
ER  - 

@article{
author = "Jovanović, Predrag and Borka Jovanović, Vesna and Borka, Duško and Bogdanović, T.",
year = "2014",
abstract = "We used a model of a relativistic accretion disk around a supermassive black hole (SMBH), based on ray-tracing method in the Kerr metric, to study the variations of the composite Fe K alpha line emitted from two accretion disks around SMBHs in a binary system. We assumed that the orbit of such a binary is approximately Keplerian, and simulated the composite line shapes for different orbital elements, accretion disk parameters and mass ratios of the components. The obtained results show that, if observed in the spectra of some SMBH binaries during their different orbital phases, such composite Fe K alpha line profiles could be used to constrain the orbits and several properties of such SMBH binaries. (C) 2013 COSPAR. Published by Elsevier Ltd. All rights reserved.",
journal = "Advances in Space Research",
title = "Composite profile of the Fe K alpha spectral line emitted from a binary system of supermassive black holes",
volume = "54",
number = "7",
pages = "1448-1457",
doi = "10.1016/j.asr.2013.10.028"
}

Jovanović, P., Borka Jovanović, V., Borka, D.,& Bogdanović, T.. (2014). Composite profile of the Fe K alpha spectral line emitted from a binary system of supermassive black holes. in Advances in Space Research, 54(7), 1448-1457.
https://doi.org/10.1016/j.asr.2013.10.028

Jovanović P, Borka Jovanović V, Borka D, Bogdanović T. Composite profile of the Fe K alpha spectral line emitted from a binary system of supermassive black holes. in Advances in Space Research. 2014;54(7):1448-1457.
doi:10.1016/j.asr.2013.10.028 .

Jovanović, Predrag, Borka Jovanović, Vesna, Borka, Duško, Bogdanović, T., "Composite profile of the Fe K alpha spectral line emitted from a binary system of supermassive black holes" in Advances in Space Research, 54, no. 7 (2014):1448-1457,
https://doi.org/10.1016/j.asr.2013.10.028 . .