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The structure of neutron stars is determined by the equation of state of the matter inside the star, which relies on the knowledge of nuclear interactions. While radii of neutron stars mostly depend on the equation of state of neutron…

Nuclear Theory · Physics 2018-07-20 Stefano Gandolfi , Diego Lonardoni

In the present paper we demonstrate that there exists a new type of neutron stars in the tensor-multi-scalar theories of gravity. We call this new type of neutron stars topological neutron stars. In addition to the standard characteristics…

General Relativity and Quantum Cosmology · Physics 2020-04-08 Daniela D. Doneva , Stoytcho S. Yazadjiev

We discuss the possible impact of strange quark matter on the evolution of core-collapse supernovae with emphasis on low critical densities for the quark-hadron phase transition. For such cases the hot proto-neutron star can collapse to a…

High Energy Astrophysical Phenomena · Physics 2013-01-29 I. Sagert , T. Fischer , M. Hempel , G. Pagliara , J. Schaffner-Bielich , F. -K. Thielemann , M. Liebendörfer

Neutron stars are valuable laboratories for the study of dense matter. Recent observations have uncovered both massive and low-mass neutron stars and have also set constraints on neutron star radii. The largest mass measurements are…

Nuclear Theory · Physics 2013-05-16 James M. Lattimer

In $f(R)$ gravity and Brans-Dicke theory with scalar potentials, we study the structure of neutron stars on a spherically symmetric and static background for two equations of state: SLy and FPS. In massless BD theory, the presence of a…

General Relativity and Quantum Cosmology · Physics 2019-10-04 Ryotaro Kase , Shinji Tsujikawa

Recent observations of neutron-star properties, in particular the recent detection of gravitational waves emitted from binary neutron stars, GW 170817, open the way to put strong constraints on nuclear interactions. In this paper, we review…

Nuclear Theory · Physics 2019-09-25 S. Gandolfi , J. Lippuner , A. W. Steiner , I. Tews , X. Du , M. Al-Mamun

Heavy scalar fields ($m_\phi\gtrsim10^{-9}$ eV) in scalar-tensor gravity are expected to be hidden from neutron-star observations because their Compton wavelength is sub-stellar. We show that neutron stars can nevertheless scalarize by…

General Relativity and Quantum Cosmology · Physics 2026-05-27 Hao-Jui Kuan , Alan Tsz-Lok Lam , Jacquelyn Noronha-Hostler , Nicolás Yunes

In the present paper we consider special classes of massive tensor-multi-scalar theories of gravity whose target space metric admits Killing field(s) with a periodic flow. For such tensor-multi-scalar theories we show that there exist mixed…

General Relativity and Quantum Cosmology · Physics 2020-01-08 Daniela D. Doneva , Stoytcho S. Yazadjiev

The recent NICER measurement of the radius of the neutron star PSR J0740+6620, and the inferred small variation of radii from 1.4$M_\odot$ to 2.1$M_\odot$, reveal key features of the equation of state of neutron star matter. The pressure…

High Energy Astrophysical Phenomena · Physics 2022-08-03 Toru Kojo , Gordon Baym , Tetsuo Hatsuda

We investigate the hadron-quark phase transition in cold neutron stars in light of (i) the observed limits on the maximum-mass of heavy pulsars, (ii) constraints on the tidal properties inferred from the gravitational waves emitted in…

High Energy Astrophysical Phenomena · Physics 2020-09-11 German Malfatti , Milva G. Orsaria , Ignacio F. Ranea-Sandoval , Gustavo A. Contrera , Fridolin Weber

We investigate the quantum hadrodynamic equation of state for neutron stars (with and without including hyperons) in the presence of strong magnetic fields. The deduced masses and radii are consistent with recent observations of high mass…

High Energy Astrophysical Phenomena · Physics 2012-11-19 Chung-Yeol Ryu , Myung-Ki Cheoun , Toshitaka Kajino , Tomoyuki Maruyama , Grant J. Mathews

We present a brief review of general results about non-rotating neutron stars in simple R-square gravity and its extension with a scalar axion field. Modified Einstein equations are presented for metrics in isotropical coordinates. The…

General Relativity and Quantum Cosmology · Physics 2020-07-08 Artyom V. Astashenok , Sergei D. Odintsov

Neutron star observations, including direct mass and radius measurements as well as the analysis of gravitational wave signals emitted by stellar mergers, provide valuable and unique insights into the properties of strongly interacting…

Nuclear Theory · Physics 2019-02-20 Aleksi Vuorinen

The profile of a neutron star probes a very large range of densities, from the density of iron up to several times the density of saturated nuclear matter, and thus no theory of hadrons can be considered reliable if extended to those…

Nuclear Theory · Physics 2025-05-20 Francesca Sammarruca , Tomiwa Ajagbonna

We investigate properties of nuclear matter, equation of state (EOS) of neutron stars and its mass-radius relation in a hard-wall AdS/QCD model by regarding baryons as solitonic configurations in gauge fields. Compared with previous…

Nuclear Theory · Physics 2025-11-07 Jun-Shuai Wang , Li-Kang Yang , Yin-Fang Liu , Yong-Liang Ma

We investigate the distribution of an interacting axion-like massive field within a magnetized Neutron Star. For this we consider the effect of an intense density-dependent axially symmetric stellar magnetic field ${\bf B}(r,\theta)$ adding…

High Energy Astrophysical Phenomena · Physics 2025-12-03 D. Suárez-Fontanella , C. Albertus , M. Ángeles Pérez-García

We investigate the equation of state (EOS) of hyperonic neutron star (NS) matter within a density-dependent relativistic mean-field (DDRMF) framework. The effects of scalar, vector, and mixed density dependencies in meson-baryon couplings…

Nuclear Theory · Physics 2025-11-04 Aprajita Shrivastava , Prasanta Char , Sakshi Gautam , Sarmistha Banik

In this work, masses and radii of neutron stars are considered to investigate the effect of nuclear symmetry energy to the astrophysical observables. A relativistic mean field model with density-dependent meson-baryon coupling constants is…

Nuclear Theory · Physics 2015-05-30 Chung-Yeol Ryu , Chang Ho Hyun , Chang-Hwan Lee

Phase transitions can play an important role in the cosmological constant problem, allowing the underlying vacuum energy, and therefore the value of the cosmological constant, to change. Deep within the core of neutron stars, the local…

General Relativity and Quantum Cosmology · Physics 2025-02-03 Giulia Ventagli , Pedro G. S. Fernandes , Andrea Maselli , Antonio Padilla , Thomas P. Sotiriou

The recent observations of neutron star mergers have changed our perspective on scalar- tensor theories of gravity, favouring models where gravitational waves travel at the speed of light. In this work we consider a scalar-tensor set-up…

General Relativity and Quantum Cosmology · Physics 2018-08-15 Javier Chagoya , Gianmassimo Tasinato