scholarly journals Gravitational decoupling of generalized Horndeski hybrid stars

2022 ◽  
Vol 82 (1) ◽  
Author(s):  
Roldao da Rocha
Keyword(s):  
General Relativity ◽  
Physical Properties ◽  
Neutron Stars ◽  
Observational Data ◽  
White Dwarfs ◽  
Mass Function ◽  
Effective Radius ◽  
Asymptotic Value ◽  
Klein Gordon ◽  
Hybrid Stars

AbstractGravitational decoupled compact polytropic hybrid stars are here addressed in generalized Horndeski scalar-tensor gravity. Additional physical properties of hybrid stars are scrutinized and discussed in the gravitational decoupling setup. The asymptotic value of the mass function, the compactness, and the effective radius of gravitational decoupled hybrid stars are studied for both cases of a bosonic and a fermionic prevalent core. These quantities are presented and discussed as functions of Horndeski parameters, the decoupling parameter, the adiabatic index, and the polytropic constant. Important corrections to general relativity and generalized Horndeski scalar-tensor gravity, induced by the gravitational decoupling, comply with available observational data. Particular cases involving white dwarfs, boson stellar configurations, neutron stars, and Einstein–Klein–Gordon solutions, formulated in the gravitational decoupling context, are also scrutinized.

The stellar graveyard

2019 ◽  
pp. 177-206
Author(s):  
Nils Andersson
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Neutron Stars ◽  
Gravitational Wave ◽  
Stellar Evolution ◽  
White Dwarfs ◽  
Supermassive Black Holes ◽  
Compact Objects ◽  
Fermi Gases ◽  
The 1950S

This chapter introduces the different classes of compact objects—white dwarfs, neutron stars, and black holes—that are relevant for gravitational-wave astronomy. The ideas are placed in the context of developing an understanding of the likely endpoint(s) of stellar evolution. Key ideas like Fermi gases and the Chandrasekhar mass are discussed, as is the emergence of general relativity as a cornerstone of astrophysics in the 1950s. Issues associated with different formation channels for, in particular, black holes are considered. The chapter ends with a discussion of the supermassive black holes that are found at the centre of galaxies.

scholarly journals Superdense Stellar Configurations in the Bimetric Scalar-Tensor Theory of Gravity

2018 ◽  
pp. 327-337
Author(s):  
L. Sh. Grigorian ◽  
H. F. Khachatryan ◽  
A. A. Saharian
Keyword(s):  
General Relativity ◽  
Scalar Field ◽  
Neutron Stars ◽  
White Dwarfs ◽  
Coupling Parameter ◽  
Spherically Symmetric ◽  
Scalar Tensor Theory ◽  
Metric Tensor ◽  
Tensor Theory ◽  
Theory Of Gravity

Models of static spherically-symmetric stellar configurations are discussed within the framework of the Bimetric scalar-tensor theory of gravity. The latter, in addition to the metric tensor and the scalar field, contains a background metric tensor as an absolute variable of the theory. The simplest variant of the theory with a constant coupling parameter and with a zero cosmological function is considered. The analysis includes both the white dwarfs and neutron stars. It is shown that, depending on the value of the theory parameter, the corresponding masses can be notably larger than those in general relativity.

scholarly journals General Relativistic Theory of Rotating Neutron Stars – A Review

1971 ◽  
Vol 46 ◽  
pp. 334-340
Author(s):  
Jeffrey M. Cohen
Keyword(s):  
General Relativity ◽  
Neutron Stars ◽  
Relativistic Theory ◽  
White Dwarfs ◽  
Relativistic Effects ◽  
Red Shift ◽  
Light Bending ◽  
Perihelion Advance ◽  
General Relativistic

Except in cosmology, astrophysicists are used to thinking of general relativistic effects as small (e.g., light bending, perihelion advance, red shift) and have generally left such problems to general relativists. However, the discovery of pulsars (Hewish et al., 1968) may have changed this. Not only is general relativity necessary to treat rotating neutron stars, but relativity was also partly responsible for the elimination of pulsating white dwarfs as pulsar models.

scholarly journals Gravitational decoupling and superfluid stars

2021 ◽  
Vol 81 (9) ◽  
Author(s):  
Roldao da Rocha
Keyword(s):  
Scalar Field ◽  
Observational Data ◽  
Mass Function ◽  
The Self ◽  
Brane Tension ◽  
Relativistic Limit ◽  
Asymptotic Value ◽  
General Relativistic ◽  
Physical Features ◽  
Scalar Gravity

AbstractThe gravitational decoupling is applied to studying minimal geometric deformed (MGD) compact superfluid stars, in covariant logarithmic scalar gravity on fluid branes. The brane finite tension is shown to provide more realistic values for the asymptotic value of the mass function of MGD superfluid stars, besides constraining the range of the self-interacting scalar field, minimally coupled to gravity. Several other physical features of MGD superfluid stars, regulated by the finite brane tension and a decoupling parameter, are derived and discussed, with important corrections to the general-relativistic limit that corroborate to current observational data.

scholarly journals Phase Conversions in Neutron Stars: Implications for Stellar Stability and Gravitational Wave Astrophysics

Universe ◽  
2021 ◽  
Vol 7 (12) ◽  
pp. 493
Author(s):  
Germán Lugones ◽  
Ana Gabriela Grunfeld
Keyword(s):  
Physical Properties ◽  
Neutron Stars ◽  
Gravitational Wave ◽  
Quark Matter ◽  
Formation Mechanisms ◽  
New Class ◽  
Stellar Stability ◽  
Hybrid Stars ◽  
Stable Hybrid

We review the properties of hybrid stars with a quark matter core and a hadronic mantle, focusing on the role of key micro-physical properties such as the quark/hadron surface and curvature tensions and the conversion speed at the interface between both phases. We summarize the results of works that have determined the surface and curvature tensions from microscopic calculations. If these quantities are large enough, mixed phases are energetically suppressed and the quark core would be separated from the hadronic mantle by a sharp interface. If the conversion speed at the interface is slow, a new class of dynamically stable hybrid objects is possible. Densities tens of times larger than the nuclear saturation density can be attained at the center of these objects. We discuss possible formation mechanisms for the new class of hybrid stars and smoking guns for their observational identification.

Origin of Magnetic Fields in White Dwarfs and Neutron Stars

1971 ◽  
Vol 231 (19) ◽  
pp. 32-33 ◽  
Author(s):  
R. F. O'CONNELL ◽  
K. M. ROUSSEL
Keyword(s):  
Magnetic Fields ◽  
Neutron Stars ◽  
White Dwarfs

scholarly journals Neutron stars as probes of dark matter

2020 ◽  
Vol 29 (14) ◽  
pp. 2043028
Author(s):  
M. Ángeles Pérez-García ◽  
Joseph Silk
Keyword(s):  
General Relativity ◽  
Dark Matter ◽  
Equation Of State ◽  
Neutron Stars ◽  
Internal Structure ◽  
Stellar Objects ◽  
Ordinary Matter ◽  
Stable Solutions ◽  
The Universe

Neutron Stars (NSs) are compact stellar objects that are stable solutions in General Relativity. Their internal structure is usually described using an equation of state that involves the presence of ordinary matter and its interactions. However there is now a large consensus that an elusive sector of matter in the universe, described as dark matter, remains as yet undiscovered. In such a case, NSs should contain both, baryonic and dark matter. We argue that depending on the nature of the dark matter and in certain circumstances, the two matter components would form a mixture inside NSs that could trigger further changes, some of them observable. The very existence of NSs constrains the nature and interactions of dark matter in the universe.

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