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Quartic gravity theory is considered with the Einstein-Hilbert Lagrangean $R+aR^{2}+bR_{\mu \nu}R^{\mu \nu},$ $R_{\mu \nu}$ being Ricci\'s tensor and R the curvature scalar. The parameters $a$ and $b$ are taken of order 1 km$^{2}.$…

General Relativity and Quantum Cosmology · Physics 2021-06-16 Emilio Santos

We report neutron star predictions based on our most recent equations of state. These are derived from chiral effective field theory, which allows for a systematic development of nuclear forces, order by order. We utilize high-quality…

Nuclear Theory · Physics 2022-03-01 Francesca Sammarruca , Randy Millerson

Gravitation might make a preferred frame appear, and with it a clear space/time separation--the latter being, a priori, needed by quantum mechanics (QM) in curved space-time. Several models of gravitation with an ether are discussed: they…

General Relativity and Quantum Cosmology · Physics 2008-04-07 Mayeul Arminjon

New observational data, measured with a high degree of accuracy, of compact isolated neutron stars and binary stars in gravitational wave remnants have the potential to explore the strong field gravity. Within the framework of…

General Relativity and Quantum Cosmology · Physics 2024-02-06 Naosad Alam , Subrata Pal , A. Rahmansyah , A. Sulaksono

Neutron stars are discussed as laboratories of physics of strong gravitational fields. The mass of a neutron star is split into matter energy and gravitational field energy contributions. The energy of the gravitational field of neutron…

General Relativity and Quantum Cosmology · Physics 2007-05-23 M. Dyrda , B. Kinasiewicz , M. Kutschera , A. Szmaglinski

General properties of neutron stars are briefly reviewed with an emphasis on the indispensability of general relativity in our understanding of these fascinating objects. In Newtonian gravity the pressure within a star merely plays the role…

High Energy Astrophysical Phenomena · Physics 2017-03-02 K. Yavuz Ekşi

We numerically construct compact stars in the scalar-tensor theory of gravity with non-minimal derivative coupling of a scalar field to the curvature and nonzero cosmological constant. There are two free parameters in this model of gravity:…

General Relativity and Quantum Cosmology · Physics 2025-04-08 P. E. Kashargin , A. A. Lebedev , S. V. Sushkov

With recent advances in neutron star observations, major progress has been made in determining the pressure of neutron star matter at high density. This pressure is constrained by the neutron star deformability, determined from…

We investigate the behavior of curvature invariants for a large ensemble of neutron stars built with equations of state (EOSs) that satisfy constraints from nuclear theory and perturbative QCD, as well as measurements of neutron-star…

General Relativity and Quantum Cosmology · Physics 2026-04-23 Iván Garibay , Christian Ecker , Luciano Rezzolla

In the context of f(R) gravity theories, we show that the apparent mass of a neutron star as seen from an observer at infinity is numerically calculable but requires careful matching, first at the star's edge, between interior and exterior…

General Relativity and Quantum Cosmology · Physics 2016-09-14 Miguel Aparicio Resco , Alvaro de la Cruz-Dombriz , Felipe J. Llanes-Estrada , Victor Zapatero Castrillo

Einstein's theory of general relativity describes gravity as the interaction of particles with space-time geometry, as opposed to interacting with a physical fluid, as in the old gravitational aether theories. Moreover, any theoretical…

Popular Physics · Physics 2010-04-19 Niayesh Afshordi

In General Relativity there is a maximum mass allowed for neutron stars that, if exceeded, entails their collapse into a black hole. Its precise value depends on details of the nuclear matter equation of state about which we are much more…

General Relativity and Quantum Cosmology · Physics 2013-05-30 Antonio Dobado , Felipe J. Llanes-Estrada , Jose Antonio Oller

Neutron stars provide a natural laboratory for studying the properties of dense nuclear matter under extreme conditions. In this proceeding, we review our current understanding of dense isospin symmetric and asymmetric matter and neutron…

Nuclear Theory · Physics 2025-04-01 Rajesh Kumar , Veronica Dexheimer , Johannes Jahan

We investigate how current and proposed observations of neutron stars can lead to an understanding of the state of their interiors and the key unknowns: the typical neutron star radius and the neutron star maximum mass. A theoretical…

Astrophysics · Physics 2008-11-26 James M. Lattimer , Maddapa Prakash

I show that several observable properties of bursting neutron stars in metric theories of gravity can be calculated using only conservation laws, Killing symmetries, and the Einstein equivalence principle, without requiring the validity of…

Astrophysics · Physics 2008-11-26 Dimitrios Psaltis

We introduce additional restriction into "general ether theory" - a generalization of Lorentz ether theory to gravity - which fixes the signs of the cosmological constants in this theory. This leads to an oscillating universe, thus, solves…

General Relativity and Quantum Cosmology · Physics 2009-12-08 Ilja Schmelzer

The properties of matter at ultra-high densities, low temperatures, and with a significant asymmetry between protons and neutrons can be studied exclusively through astrophysical observations of neutron stars. We show that measurements of…

High Energy Astrophysical Phenomena · Physics 2010-02-16 Feryal Ozel , Dimitrios Psaltis

We consider a Lorentz-violating theory of gravity where the aether vector is taken to be nondynamical. This "ponderable aether theory" is almost the same as Einstein-aether theory (where the aether vector is dynamical), but involves…

General Relativity and Quantum Cosmology · Physics 2015-08-19 Antony J. Speranza

The past years have witnessed tremendous progress in understanding the properties of neutron stars and of the dense matter in their cores, made possible by electromagnetic observations of neutron stars and the detection of gravitational…

We investigate the effects of relativity on the gravitational instability of finite isothermal gaseous spheres. In the first part of the paper, we treat the gravitational field within the framework of Newtonian mechanics but we use a…

Astrophysics · Physics 2009-11-07 Pierre-Henri Chavanis