Structure, maximum mass, and stability of compact stars in $$f(\mathcal {Q,T})$$ f ( Q , T ) gravity
Abstract We investigate the properties of compact objects in the f(Q, T) theory, where $$\mathcal {Q}$$ Q is the non-metricity scalar and $${ \mathcal {T}}$$ T is the trace of the energy–momentum tensor. We derive an interior analytical solution for anisotropic perfect-fluid spheres in hydrostatic e...
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2024-10-01
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| Series: | European Physical Journal C: Particles and Fields |
| Online Access: | https://doi.org/10.1140/epjc/s10052-024-13436-8 |
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| author | G. G. L. Nashed Tiberiu Harko |
| author_facet | G. G. L. Nashed Tiberiu Harko |
| author_sort | G. G. L. Nashed |
| collection | DOAJ |
| description | Abstract We investigate the properties of compact objects in the f(Q, T) theory, where $$\mathcal {Q}$$ Q is the non-metricity scalar and $${ \mathcal {T}}$$ 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 $$f(\mathcal {Q}, { \mathcal {T}})=\mathcal {Q}+\psi { \mathcal {T}}$$ f ( Q , T ) = Q + ψ T , where $$\psi $$ ψ represents a dimensional parameter. Based on the observational constraints related to the mass and radius of the pulsar SAX J1748.9-2021, $$\psi $$ ψ is set to a maximum negative value of $$\psi _1=\psi / \kappa ^2=-0.04$$ ψ 1 = ψ / κ 2 = - 0.04 , where $$\kappa ^2$$ κ 2 is the gravitational coupling constant. The solution results in a stable compact object, which does not violate the speed of sound condition $$c_s^2\le \frac{c^2}{3}$$ c s 2 ≤ 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 $$\psi $$ ψ 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 $$\psi $$ ψ 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 $$f(\mathcal {Q}, { \mathcal {T}})$$ f ( Q , T ) theory and for GR is $$C = 0.514$$ C = 0.514 and 0.419, respectively, with the $$f(\mathcal {Q}, { \mathcal {T}})$$ f ( Q , T ) prediction about $$10\%$$ 10 % higher than the GR one. Assuming a surface density at saturation nuclear density of $$\rho _{\text {nuc}} = 4\times 10^{14}~\hbox {g}/\hbox {cm}^3$$ ρ nuc = 4 × 10 14 g / cm 3 , the maximum mass of the star is $$4.66 M_\odot $$ 4.66 M ⊙ , with a radius of 14.9 km. |
| format | Article |
| id | doaj-art-e22ee6e27bec4ebe9d3da4e42ffceb9d |
| institution | Kabale University |
| issn | 1434-6052 |
| language | English |
| publishDate | 2024-10-01 |
| publisher | SpringerOpen |
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| series | European Physical Journal C: Particles and Fields |
| spelling | doaj-art-e22ee6e27bec4ebe9d3da4e42ffceb9d2024-12-08T12:42:27ZengSpringerOpenEuropean Physical Journal C: Particles and Fields1434-60522024-10-01841011910.1140/epjc/s10052-024-13436-8Structure, maximum mass, and stability of compact stars in $$f(\mathcal {Q,T})$$ f ( Q , T ) gravityG. G. L. Nashed0Tiberiu Harko1Centre for Theoretical Physics, The British University in Egypt El Sherouk CityDepartment of Physics, Babes-Bolyai UniversityAbstract We investigate the properties of compact objects in the f(Q, T) theory, where $$\mathcal {Q}$$ Q is the non-metricity scalar and $${ \mathcal {T}}$$ 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 $$f(\mathcal {Q}, { \mathcal {T}})=\mathcal {Q}+\psi { \mathcal {T}}$$ f ( Q , T ) = Q + ψ T , where $$\psi $$ ψ represents a dimensional parameter. Based on the observational constraints related to the mass and radius of the pulsar SAX J1748.9-2021, $$\psi $$ ψ is set to a maximum negative value of $$\psi _1=\psi / \kappa ^2=-0.04$$ ψ 1 = ψ / κ 2 = - 0.04 , where $$\kappa ^2$$ κ 2 is the gravitational coupling constant. The solution results in a stable compact object, which does not violate the speed of sound condition $$c_s^2\le \frac{c^2}{3}$$ c s 2 ≤ 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 $$\psi $$ ψ 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 $$\psi $$ ψ 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 $$f(\mathcal {Q}, { \mathcal {T}})$$ f ( Q , T ) theory and for GR is $$C = 0.514$$ C = 0.514 and 0.419, respectively, with the $$f(\mathcal {Q}, { \mathcal {T}})$$ f ( Q , T ) prediction about $$10\%$$ 10 % higher than the GR one. Assuming a surface density at saturation nuclear density of $$\rho _{\text {nuc}} = 4\times 10^{14}~\hbox {g}/\hbox {cm}^3$$ ρ nuc = 4 × 10 14 g / cm 3 , the maximum mass of the star is $$4.66 M_\odot $$ 4.66 M ⊙ , with a radius of 14.9 km.https://doi.org/10.1140/epjc/s10052-024-13436-8 |
| spellingShingle | G. G. L. Nashed Tiberiu Harko Structure, maximum mass, and stability of compact stars in $$f(\mathcal {Q,T})$$ f ( Q , T ) gravity European Physical Journal C: Particles and Fields |
| title | Structure, maximum mass, and stability of compact stars in $$f(\mathcal {Q,T})$$ f ( Q , T ) gravity |
| title_full | Structure, maximum mass, and stability of compact stars in $$f(\mathcal {Q,T})$$ f ( Q , T ) gravity |
| title_fullStr | Structure, maximum mass, and stability of compact stars in $$f(\mathcal {Q,T})$$ f ( Q , T ) gravity |
| title_full_unstemmed | Structure, maximum mass, and stability of compact stars in $$f(\mathcal {Q,T})$$ f ( Q , T ) gravity |
| title_short | Structure, maximum mass, and stability of compact stars in $$f(\mathcal {Q,T})$$ f ( Q , T ) gravity |
| title_sort | structure maximum mass and stability of compact stars in f mathcal q t f q t gravity |
| url | https://doi.org/10.1140/epjc/s10052-024-13436-8 |
| work_keys_str_mv | AT gglnashed structuremaximummassandstabilityofcompactstarsinfmathcalqtfqtgravity AT tiberiuharko structuremaximummassandstabilityofcompactstarsinfmathcalqtfqtgravity |