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Neutron stars in Scalar-Tensor-Vector Gravity

  • Federico G. Lopez ArmengolEmail author
  • Gustavo E. Romero
Research Article

Abstract

Scalar-Tensor-Vector Gravity (STVG), also referred as Modified Gravity (MOG), is an alternative theory of the gravitational interaction. Its weak field approximation has been successfully used to describe Solar System observations, galaxy rotation curves, dynamics of clusters of galaxies, and cosmological data, without the imposition of dark components. The theory was formulated by John Moffat in 2006. In this work, we derive matter-sourced solutions of STVG and construct neutron star models. We aim at exploring STVG predictions about stellar structure in the strong gravity regime. Specifically, we represent spacetime with a static, spherically symmetric manifold, and model the stellar matter content with a perfect fluid energy-momentum tensor. We then derive the modified Tolman–Oppenheimer–Volkoff equation in STVG and integrate it for different equations of state. We find that STVG allows heavier neutron stars than General Relativity (GR). Maximum masses depend on a normalized parameter that quantifies the deviation from GR. The theory exhibits unusual predictions for extreme values of this parameter. We conclude that STVG admits suitable spherically symmetric solutions with matter sources, relevant for stellar structure. Since recent determinations of neutron stars masses violate some GR predictions, STVG appears as a viable candidate for a new gravity theory.

Keywords

Modified gravity Vector gravity Neutron stars 

References

  1. 1.
    Bunge, M.A.: Treatise on Basic Philosophy: Ontology I: The Furniture of the World. Springer, Berlin (1977)CrossRefzbMATHGoogle Scholar
  2. 2.
    Aprile, E., Alfonsi, M., Arisaka, K., et al.: Dark matter results from 225 live days of XENON100 data. Phys. Rev. Lett. 109, 181301 (2012)ADSCrossRefGoogle Scholar
  3. 3.
    LUX Collaboration: First results from the LUX dark matter experiment at the Sanford Underground Research Facility. ArXiv e-prints: 1310.8214 (2013)Google Scholar
  4. 4.
    Agnese, R., Anderson, A.J., Asai, M., et al.: Search for low-mass weakly interacting massive particles with superCDMS. Phys. Rev. Lett. 112, 241302 (2014)ADSCrossRefGoogle Scholar
  5. 5.
    Milgrom, M.: A modification of the Newtonian dynamics as a possible alternative to the hidden mass hypothesis. Astrophys. J. 270, 365–370 (1983)ADSCrossRefGoogle Scholar
  6. 6.
    Bekenstein, J., Milgrom, M.: Does the missing mass problem signal the breakdown of Newtonian gravity? Astrophys. J. 286, 7–14 (1984)ADSCrossRefGoogle Scholar
  7. 7.
    Sanders, R.H.: Phase coupling gravity and astronomical mass discrepancies. Mon. Not. R. Astron. Soc. 235, 105–121 (1988)ADSCrossRefGoogle Scholar
  8. 8.
    Sanders, R.H.: A stratified framework for scalar–tensor theories of modified dynamics. Astrophys. J. 480, 492–502 (1997)ADSCrossRefGoogle Scholar
  9. 9.
    Bekenstein, J.D.: Relativistic gravitation theory for the modified Newtonian dynamics paradigm. Phys. Rev. D 70, 083509 (2004)ADSCrossRefGoogle Scholar
  10. 10.
    Famaey, B., McGaugh, S.S.: Modified Newtonian dynamics (MOND): observational phenomenology and relativistic extensions. Living Rev. Relativ. 15, 10 (2012)ADSCrossRefGoogle Scholar
  11. 11.
    Moffat, J.W.: Scalar tensor vector gravity theory. J. Cosmol. Astropart. Phys. 3, 4 (2006)ADSMathSciNetCrossRefzbMATHGoogle Scholar
  12. 12.
    Brownstein, J.R., Moffat, J.W.: Galaxy rotation curves without nonbaryonic dark matter. Astrophys. J. 636, 721–741 (2006)ADSCrossRefGoogle Scholar
  13. 13.
    Moffat, J.W., Rahvar, S.: The MOG weak field approximation-II. Observational test of Chandra X-ray clusters. Mon. Not. R. Astron. Soc. 441, 3724–3732 (2014)ADSCrossRefGoogle Scholar
  14. 14.
    Brownstein, J.R., Moffat, J.W.: The bullet cluster 1E0657-558 evidence shows modified gravity in the absence of dark matter. Mon. Not. R. Astron. Soc. 382, 29–47 (2007)ADSCrossRefGoogle Scholar
  15. 15.
    Moffat, J.W., Toth, V.T.: Modified gravity: cosmology without dark matter or Einstein’s cosmological constant.ArXiv e-prints: 0710.0364 (2007)Google Scholar
  16. 16.
    Lasky, P.D.: Black holes and neutron stars in the generalized tensor-vector-scalar theory. Phys. Rev. D 80, 081501 (2009)ADSCrossRefGoogle Scholar
  17. 17.
    Lasky, P.D., Doneva, D.D.: Stability and quasinormal modes of black holes in tensor–vector–scalar theory scalar field perturbations. Phys. Rev. D 82, 124068 (2010)ADSCrossRefGoogle Scholar
  18. 18.
    Mavromatos, N.E., Sakellariadou, M., Yusaf, M.F.: Can the relativistic field theory version of modified Newtonian dynamics avoid dark matter on galactic scales? Phys. Rev. D 79, 081301 (2009)ADSCrossRefGoogle Scholar
  19. 19.
    Seifert, M.D.: Stability of spherically symmetric solutions in modified theories of gravity. Phys. Rev. D 76, 064002 (2007)ADSCrossRefGoogle Scholar
  20. 20.
    Moffat, J.W., Rahvar, S.: The MOG weak field approximation and observational test of galaxy rotation curves. Mon. Not. R. Astron. Soc 436, 1439–1451 (2013)ADSCrossRefGoogle Scholar
  21. 21.
    Moffat, J.W., Toth, V.T.: Fundamental parameter-free solutions in modified gravity. Class. Quantum Gravity 26, 085002 (2009)ADSMathSciNetCrossRefzbMATHGoogle Scholar
  22. 22.
    Moffat, J.W.: Black holes in modified gravity (MOG). Eur. Phys. J. C 75, 175 (2015)ADSCrossRefGoogle Scholar
  23. 23.
    Florides, P.S.: The complete field of charged perfect fluid spheres and of other static spherically symmetric charged distributions. J. Phys. A Math. Gen. 16, 1419 (1983)ADSMathSciNetCrossRefzbMATHGoogle Scholar
  24. 24.
    Maurya, S.K., Gupta, Y.K., Ray, S., Chowdhury, S.R.: Spherically symmetric electromagnetic mass models of embedding class one. ArXiv e-prints: 1506.02498 (2015)Google Scholar
  25. 25.
    Silbar, R.R., Reddy, S.: Neutron stars for undergraduates. Am. J. Phys. 72, 892–905 (2004)ADSCrossRefGoogle Scholar
  26. 26.
    Douchin, F., Haensel, P.: A unified equation of state of dense matter and neutron star structure. Astron. Astrophys. 380, 151–167 (2001)ADSCrossRefGoogle Scholar
  27. 27.
    Pandharipande, V.R., Ravenhall, D.G.: Hot nuclear matter. In: Soyeur, M., Flocard, H., Tamain, B., Porneuf, M. (eds.) NATO Advanced Science Institutes ASI Series B, vol. 205, p. 103. Springer, US (1989)Google Scholar
  28. 28.
    Goriely, S., Chamel, N., Pearson, J.M.: Further explorations of Skyrme–Hartree–Fock–Bogoliubov mass formulas. XII. Stiffness and stability of neutron-star matter. Phys. Rev. C 82, 035804 (2010)ADSCrossRefGoogle Scholar
  29. 29.
    Pearson, J.M., Goriely, S., Chamel, N.: Properties of the outer crust of neutron stars from Hartree–Fock–Bogoliubov mass models. Phys. Rev. C 83, 065810 (2011)ADSCrossRefGoogle Scholar
  30. 30.
    Pearson, J.M., Chamel, N., Goriely, S., Ducoin, C.: Inner crust of neutron stars with mass-fitted Skyrme functionals. Phys. Rev. C 85, 065803 (2012)ADSCrossRefGoogle Scholar
  31. 31.
    Haensel, P., Potekhin, A.Y.: Analytical representations of unified equations of state of neutron-star matter. Astron. Astrophys. 428, 191–197 (2004)ADSCrossRefzbMATHGoogle Scholar
  32. 32.
    Potekhin, A.Y., Fantina, A.F., Chamel, N., et al.: Analytical representations of unified equations of state for neutron-star matter. Astron. Astrophys. 560, A48 (2013)ADSCrossRefGoogle Scholar
  33. 33.
    Press, W.H., Flannery, B.P., Teukolsky, S.A., Vetterling, W.T.: Numerical Recipes in FORTRAN 77, vol. 1. Cambridge University Press, Cambridge (1992)zbMATHGoogle Scholar
  34. 34.
    Orellana, M., García, F., Teppa Pannia, F.A., Romero, G.E.: Structure of neutron stars in R-squared gravity. Gen. Relativ. Gravit. 45, 771–783 (2013)ADSMathSciNetCrossRefzbMATHGoogle Scholar
  35. 35.
    Antoniadis, J., Freire, P.C.C., Wex, N., et al.: A massive pulsar in a compact relativistic binary. Science 340, 448 (2013)ADSCrossRefGoogle Scholar
  36. 36.
    Kiziltan, B., Kottas, A., De Yoreo, M., Thorsett, S.E.: The neutron star mass distribution. Astrophys. J. 778, 66 (2013)ADSCrossRefGoogle Scholar
  37. 37.
    Özel, F., Psaltis, D., Narayan, R., Santos Villarreal, A.: On the mass distribution and birth masses of neutron stars. Astrophys. J. 757, 55 (2012)ADSCrossRefGoogle Scholar
  38. 38.
    Demorest, P.B., Pennucci, T., Ransom, S.M., et al.: A two-solar-mass neutron star measured using Shapiro delay. Nature 467, 1081–1083 (2010)ADSCrossRefGoogle Scholar
  39. 39.
    Yazadjiev, S.S., Doneva, D.D., Kokkotas, K.D., Staykov, K.V.: Non-perturbative and self-consistent models of neutron stars in R-squared gravity. J. Cosmol. Astropart. Phys. 6, 3 (2014)ADSCrossRefGoogle Scholar
  40. 40.
    Lasky, P.D., Sotani, H., Giannios, D.: Structure of neutron stars in tensor–vector–scalar theory. Phys. Rev. D 78, 104019 (2008)ADSCrossRefGoogle Scholar
  41. 41.
    Sotani, H.: Slowly rotating relativistic stars in tensor–vector–scalar theory. Phys. Rev. D 81, 084006 (2010)ADSCrossRefGoogle Scholar
  42. 42.
    Yazadjiev, S.S., Doneva, D.D., Kokkotas, K.D.: Rapidly rotating neutron stars in R-squared gravity. Phys. Rev. D 91, 084018 (2015)ADSMathSciNetCrossRefGoogle Scholar
  43. 43.
    Staykov, K.V., Doneva, D.D., Yazadjiev, S.S., Kokkotas, K.D.: Slowly rotating neutron and strange stars in \(\text{ R }^{2}\) gravity. J. Cosmol. Astropart. Phys. 10, 6 (2014)ADSCrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media New York 2017

Authors and Affiliations

  • Federico G. Lopez Armengol
    • 1
    Email author
  • Gustavo E. Romero
    • 1
    • 2
  1. 1.Instituto Argentino de Radioastronomía CCT La Plata (CONICET)Buenos AiresArgentina
  2. 2.Facultad de Ciencias Astronómicas y GeofísicasUniversidad Nacional de La PlataLa PlataArgentina

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