{"title":"Structure, maximum mass, and stability of compact stars in \\(f(\\mathcal {Q,T})\\) gravity","authors":"G. G. L. Nashed, Tiberiu Harko","doi":"10.1140/epjc/s10052-024-13436-8","DOIUrl":null,"url":null,"abstract":"<div><p>We investigate the properties of compact objects in the <i>f</i>(<i>Q</i>, <i>T</i>) theory, where <span>\\(\\mathcal {Q}\\)</span> is the non-metricity scalar and <span>\\({ \\mathcal {T}}\\)</span> is the trace of the energy–momentum tensor. We derive an interior analytical solution for anisotropic perfect-fluid spheres in hydrostatic equilibrium using the linear form of <span>\\(f(\\mathcal {Q}, { \\mathcal {T}})=\\mathcal {Q}+\\psi { \\mathcal {T}}\\)</span>, where <span>\\(\\psi \\)</span> represents a dimensional parameter. Based on the observational constraints related to the mass and radius of the pulsar SAX J1748.9-2021, <span>\\(\\psi \\)</span> is set to a maximum negative value of <span>\\(\\psi _1=\\psi / \\kappa ^2=-0.04\\)</span>, where <span>\\(\\kappa ^2\\)</span> is the gravitational coupling constant. The solution results in a stable compact object, which does not violate the speed of sound condition <span>\\(c_s^2\\le \\frac{c^2}{3}\\)</span>. The effective equation of state is similar to the quark matter equation of state, and involves the presence of an effective bag constant. When <span>\\(\\psi \\)</span> is negative, the star has a slightly larger size as compared to GR stars with the same mass. The difference in the predicted star size between the theory with a negative <span>\\(\\psi \\)</span> and GR for the same mass is attributed to an additional force appearing in the hydrodynamic equilibrium equation. The maximum compactness allowed by the strong energy condition for <span>\\(f(\\mathcal {Q}, { \\mathcal {T}})\\)</span> theory and for GR is <span>\\(C = 0.514\\)</span> and 0.419, respectively, with the <span>\\(f(\\mathcal {Q}, { \\mathcal {T}})\\)</span> prediction about <span>\\(10\\%\\)</span> higher than the GR one. Assuming a surface density at saturation nuclear density of <span>\\(\\rho _{\\text {nuc}} = 4\\times 10^{14}~\\hbox {g}/\\hbox {cm}^3\\)</span>, the maximum mass of the star is <span>\\(4.66 M_\\odot \\)</span>, with a radius of 14.9 km.</p></div>","PeriodicalId":788,"journal":{"name":"The European Physical Journal C","volume":null,"pages":null},"PeriodicalIF":4.2000,"publicationDate":"2024-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjc/s10052-024-13436-8.pdf","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"The European Physical Journal C","FirstCategoryId":"4","ListUrlMain":"https://link.springer.com/article/10.1140/epjc/s10052-024-13436-8","RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"PHYSICS, PARTICLES & FIELDS","Score":null,"Total":0}
引用次数: 0
Abstract
We investigate the properties of compact objects in the f(Q, T) theory, where \(\mathcal {Q}\) is the non-metricity scalar and \({ \mathcal {T}}\) is the trace of the energy–momentum tensor. We derive an interior analytical solution for anisotropic perfect-fluid spheres in hydrostatic equilibrium using the linear form of \(f(\mathcal {Q}, { \mathcal {T}})=\mathcal {Q}+\psi { \mathcal {T}}\), where \(\psi \) represents a dimensional parameter. Based on the observational constraints related to the mass and radius of the pulsar SAX J1748.9-2021, \(\psi \) is set to a maximum negative value of \(\psi _1=\psi / \kappa ^2=-0.04\), where \(\kappa ^2\) is the gravitational coupling constant. The solution results in a stable compact object, which does not violate the speed of sound condition \(c_s^2\le \frac{c^2}{3}\). The effective equation of state is similar to the quark matter equation of state, and involves the presence of an effective bag constant. When \(\psi \) is negative, the star has a slightly larger size as compared to GR stars with the same mass. The difference in the predicted star size between the theory with a negative \(\psi \) and GR for the same mass is attributed to an additional force appearing in the hydrodynamic equilibrium equation. The maximum compactness allowed by the strong energy condition for \(f(\mathcal {Q}, { \mathcal {T}})\) theory and for GR is \(C = 0.514\) and 0.419, respectively, with the \(f(\mathcal {Q}, { \mathcal {T}})\) prediction about \(10\%\) higher than the GR one. Assuming a surface density at saturation nuclear density of \(\rho _{\text {nuc}} = 4\times 10^{14}~\hbox {g}/\hbox {cm}^3\), the maximum mass of the star is \(4.66 M_\odot \), with a radius of 14.9 km.
期刊介绍:
Experimental Physics I: Accelerator Based High-Energy Physics
Hadron and lepton collider physics
Lepton-nucleon scattering
High-energy nuclear reactions
Standard model precision tests
Search for new physics beyond the standard model
Heavy flavour physics
Neutrino properties
Particle detector developments
Computational methods and analysis tools
Experimental Physics II: Astroparticle Physics
Dark matter searches
High-energy cosmic rays
Double beta decay
Long baseline neutrino experiments
Neutrino astronomy
Axions and other weakly interacting light particles
Gravitational waves and observational cosmology
Particle detector developments
Computational methods and analysis tools
Theoretical Physics I: Phenomenology of the Standard Model and Beyond
Electroweak interactions
Quantum chromo dynamics
Heavy quark physics and quark flavour mixing
Neutrino physics
Phenomenology of astro- and cosmoparticle physics
Meson spectroscopy and non-perturbative QCD
Low-energy effective field theories
Lattice field theory
High temperature QCD and heavy ion physics
Phenomenology of supersymmetric extensions of the SM
Phenomenology of non-supersymmetric extensions of the SM
Model building and alternative models of electroweak symmetry breaking
Flavour physics beyond the SM
Computational algorithms and tools...etc.