Hybrid metric-Palatini stars

Abstract

We consider the internal structure and the physical properties of specific classes of neutron, quark and Bose-Einstein Condensate stars in the hybrid metric-Palatini gravity theory, which is a combination of the metric and Palatini $f(R)$ formalisms. The theory is very successful in accounting for the observed phenomenology, since it unifies local constraints at the Solar System level and the late-time cosmic acceleration, even if the scalar field is very light. We derive the equilibrium equations for a spherically symmetric configuration (mass continuity and Tolman-Oppenheimer-Volkoff) in the framework of hybrid metric-Palatini theory, and we investigate their solutions numerically for different equations of state of neutron and quark matter, by adopting for the scalar field potential a Higgs-type form. Stellar models, described by the stiff fluid, radiation-like, the bag model and the Bose-Einstein Condensate equations of state are explicitly constructed in both General Relativity and hybrid metric-Palatini gravity, thus allowing an in depth comparison between the predictions of these two gravitational theories. As a general result it turns out that for all the considered equations of state, hybrid metric-Palatini gravity stars are more massive than their general relativistic counterparts. Furthermore, two classes of stellar models corresponding to fixed forms of the scalar field are also investigated. Interestingly enough, in the case of a constant scalar field the equation of state of the matter takes the form of the bag model equation of state describing quark matter. As a possible astrophysical application of the obtained results we suggest that stellar mass black holes, with masses in the range of $3.8M_{\odot }$ and $6M_{\odot }$, respectively, could be in fact hybrid metric-Palatini gravity neutron or quark stars.

21 pages, 11 figures; major revisions; accepted for publication in PRD

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Cited by in corpus (11)

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• Swampland conjectures in hybrid metric-Palatini gravity
• Static spherically symmetric three-form stars
• Thin accretion disk signatures in hybrid metric-Palatini gravity
• Dynamical reconstruction of the $\Lambda$CDM model in hybrid metric-Palatini gravity
• Compact stars in the Einstein dark energy model
• Polarization and speed of gravitational waves in hybrid metric-Palatini f(R)-gravity
• Novel electrically charged wormhole, black hole and black bounce exact solutions in hybrid metric-Palatini gravity
• Gravitational wave propagation in generalized hybrid metric-Palatini gravity
• Gravitational waveforms from inspiral compact binaries in Hybrid metric-Palatini gravity
• Images of the accretion disk in Hybrid metric-Palatini gravity