Deflection angle and lensing signature of covariant f(T) gravity

Ren, Xin; Zhao, Yaqi; Saridakis, Emmanuel N.; Cai, Yi-Fu

doi:10.48550/arxiv.2105.04578

Cited by 10 publications

(24 citation statements)

References 68 publications

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“…The above invariants reveal the presence of the singularity at r = 0 as expected, which is more mild than the case of simple TEGR, a known feature of higher-order torsional theories [7,56,60,80].…”

Section: B Invariantssupporting

confidence: 66%

Stability of motion and thermodynamics in charged black holes in $f(T)$ gravity

Nashed,

Saridakis

2021

Preprint

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We investigate the stability and thermodynamics of spherically symmetric solutions in f (T ) gravity using the perturbative approach. We consider small deviations from general relativity and we extract charged black hole solutions for two charge profiles, namely with or without a perturbative correction in the charge distribution. We examine their asymptotic behavior, we extract various torsional and curvature invariants, and we calculate the energy and the mass of the solutions. Furthermore, we study the stability of the obtained black hole solutions, by analyzing the geodesic deviation, and we extract the unstable regimes in the parameter space. We calculate the inner (Cauchy) and outer (event) horizons, showing that for larger deviations from general relativity or larger charges, the horizon disappears and the central singularity becomes a naked one. Additionally, we perform a detailed thermodynamic analysis examining the temperature, entropy, heat capacity and Gibb's free energy. Concerning the heat capacity we find that for larger deviations from general relativity it is always positive, and this shows that f (T ) modifications improve the thermodynamic stability, which is not the case in other classes of modified gravity.

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Section: B Invariantssupporting

confidence: 66%

Stability of motion and thermodynamics in charged black holes in $f(T)$ gravity

Nashed,

Saridakis

2021

Preprint

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“…This conclusion is expected to hold true even if the universal and EoS-independent relation between that baryonic and gravitational masses for static NSs is found. However, in order to be accurate, one must perform similar calculations for spherical symmetric spacetimes in other modified gravities, like f (T ) gravity [77,78] or even Einstein-Gauss-Bonnet gravity [79].…”

Section: Discussionmentioning

confidence: 99%

Maximum Baryon Masses for Static Neutron Stars in $f(R)$ Gravity

Astashenok,

Capozziello,

Odintsov

et al. 2021

Preprint

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We investigate the upper mass limit predictions of the baryonic mass for static neutron stars in the context of f (R) gravity. We use the most popular f (R) gravity model, namely the R 2 gravity, and calculate the maximum baryon mass of static neutron stars adopting several realistic equations of state and one ideal equation of state, namely that of causal limit. Our motivation is based on the fact that neutron stars with baryon masses larger than the maximum mass for static neutron star configurations inevitably collapse to black holes. Thus with our analysis, we want further to enlighten the predictions for the maximum baryon masses of static neutron stars in R 2 gravity, which, in turn, further strengthens our understanding of the mysterious mass-gap region. As we show, the baryon masses of most of the equations of states studied in this paper, lie in the lower limits of the mass-gap region M ∼ 2.5 − 5M⊙, but intriguingly enough, the highest value of the maximum baryon masses we found is of the order of M ∼ 3M⊙. This upper mass limit also appears as a maximum static neutron star gravitational mass limit in other contexts. Combining the two results which refer to baryon and gravitational masses, we point out that the gravitational mass of static neutron stars cannot be larger than three solar masses, while based on maximum baryon masses results of the present work, we can conspicuously state that it is highly likely the lower mass limits of astrophysical black holes in the range of M ∼ 2.5 − 3M⊙. This, in turn, implies that maximum neutron star masses in the context of R 2 gravity are likely to be in the lower limits of the range of M ∼ 2.4 − 3M⊙. Hence our work further supports the General Relativity claim that neutron stars cannot have gravitational masses larger than 3M⊙ and then, to explain observations comparable or over this limit, we need alternative extensions of General Relativity, other than f (R) gravity.

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“…Thus automatically, one has available the lowest astrophysical black hole mass limit. Finally, let us comment that the same procedure performed in this paper, can be applied in other modified gravity theories, such as f (T ) gravity, in which the spherically symmetric solutions have also extended terms similar to the ones of f (R) gravity, see for example [12,13].…”

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confidence: 86%

Novel Stellar Astrophysics from Extended Gravity

Astashenok,

Capozziello,

Odintsov

et al. 2021

Preprint

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Deflection angle and lensing signature of covariant f(T) gravity

Cited by 10 publications

References 68 publications

Stability of motion and thermodynamics in charged black holes in $f(T)$ gravity

Stability of motion and thermodynamics in charged black holes in $f(T)$ gravity

Maximum Baryon Masses for Static Neutron Stars in $f(R)$ Gravity

Novel Stellar Astrophysics from Extended Gravity

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