Neutron star masses in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="d1e1456" altimg="si3.svg"><mml:msup><mml:mrow><mml:mi>R</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msup></mml:math>-gravity

Sbisà, Fulvio; Baqui, P. O.; Miranda, Tays; Jorás, S. E.; Piattella, Oliver F.

doi:10.1016/j.dark.2019.100411

Cited by 23 publications

(32 citation statements)

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“…Should A(∞) go instead to some constant A ∞ , a simple re-scaling of the initial condition as A(0) → A(0)/A ∞ brings the numerical problem into the desired form 27. For an extended discussion on the definition of the gravitational mass in models with R 2 -corrections see[222] 28. For some analysis of charged neutron matter within GR see e.g [226]…”

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confidence: 99%

Stellar structure models in modified theories of gravity: Lessons and challenges

2020

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The understanding of stellar structure represents the crossroads of our theories of the nuclear force and the gravitational interaction under the most extreme conditions observably accessible. It provides a powerful probe of General Relativity on its strong field regime, and opens fruitful avenues for the exploration of new gravitational physics. The latter can be captured via the so-called modified theories of gravity, which modify the Einstein-Hilbert action of General Relativity and/or some of its building blocks/principles. These theories typically change the Tolman-Oppenheimer-Volkoff equations of stellar's hydrostatic equilibrium, having a large impact on the astrophysical properties of the corresponding stars, and thus opening a new window to constrain these theories with present and future observations of different types of stars. For relativistic stars, such as neutron stars, the uncertainty on the equation of state of matter at supranuclear densities intertwines with the new parameters coming from the modified gravity side, providing a whole new phenomenology for the typical predictions of stellar structure models, such as mass-radius relations, maximum masses, or moment of inertia. For non-relativistic stars, such as white, brown and red dwarfs, the weakening/strengthening of the gravitational force inside astrophysical bodies via the modified Newtonian (Poisson) equation may induce changes on the star's mass, radius, central density or luminosity, having an impact, for instance, in the Chandrasekhar's limit for white dwarfs, or in the minimum mass for stable hydrogen burning for high-mass brown dwarfs. This work aims to provide a broad overview of the main such results achieved in the recent literature for many such modified theories of gravity, by combining the results and constraints obtained from the analysis of relativistic and non-relativistic stars in different scenarios. Moreover, we will build a bridge between the efforts of the community working on different theories, formulations, types of stars, theoretical modellings, and observational aspects, highlighting some of the most promising opportunities in the field.

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confidence: 99%

Stellar structure models in modified theories of gravity: Lessons and challenges

2020

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“…is no longer constant outside the star, and the surface mass M s = M (R s ) is different from the asymptotic or ADM (=Arnowitt-Deser-Misner) mass M ∞ = lim r→∞ M (r) as seen by a distant observer. M s is also different from M ρ (R s ), because it receives additional contributions from the curvature scalar inside the star radius (for a detailed discussion see [49]).…”

Section: Resultsmentioning

confidence: 99%

“…BPS Skyrme neutron stars, by construction, do not have a crust region, although a crust can be added without difficulty [50]. Other EoS, which are much softer in the low-density region, produce pronounced crust regions for small mass neutron stars and, thus, the crossing happens for much larger masses, see, e.g., [49]. Another interesting quantity is the mass at the surface of the star, M s , which in f (R) gravity is a second, independent and invariant mass observable, as explained in [49].…”

Section: Resultsmentioning

confidence: 99%

“…Other EoS, which are much softer in the low-density region, produce pronounced crust regions for small mass neutron stars and, thus, the crossing happens for much larger masses, see, e.g., [49]. Another interesting quantity is the mass at the surface of the star, M s , which in f (R) gravity is a second, independent and invariant mass observable, as explained in [49]. It may be understood as a sum of the mass contributions of matter and curvature inside the star.…”

Section: Resultsmentioning

confidence: 99%

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BPS Skyrme neutron stars in generalized gravity

Adam,

Huidobro,

Vazquez

et al. 2020

Preprint

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We study the coupling of nuclear matter described by the BPS Skyrme model to generalized gravity. Concretely, we consider the Starobinsky model which provides the leading-order correction to the Einstein-Hilbert action. Static solutions describing neutron stars are found both for the full field theory and for the mean-field approximation. We always consider the full Starobinsky model in the nonperturbative approach, using appropriately generalized shooting methods for the numerical neutron star calculations. Many of our results are similar to previous investigations of neutron stars for the Starobinsky model using other models of nuclear matter, but there are some surprizing discrepancies. The "Newtonian mass" relevant for the surface redshift, e.g., results larger than the ADM mass in our model, in contrast to other investigations. This difference is related to the particularly high stiffness of nuclear matter described by the BPS Skyrme model and offers an interesting possibility to distinguish different models of nuclear matter within generalized gravity.

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“…It may happen, as it was discussed in, for instance, [108][109][110], that the extra terms introduced by the invariants provide a non-zero contribution to the mass function far away from the star's surface (when p(R) = 0, where R is the star's radius); that is, the mass function does not converge when r → ∞ but can oscillate instead around a constant value. This fact has following consequences: as proposed in [108] and then discussed in more detail in [111], in the case of f (R) metric gravity and general ST theories which introduce an additional degree of freedom, this phenomena could be used to test such theories against GR by the mean of the surface gravitational redshift. It comes from the fact that mass measured by a distant observer (gravitational mass) differs from the stellar mass, which is understood as a sphere bounded by the star's surface together with gravitational energy, in the energy of the extra degree of freedom, which happens not to be zero inside and outside the star.…”

Section: Discussionmentioning

confidence: 97%