Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Compact Stars in Symmetric Teleparallel Scalar-Tensor Gravity

Grigorios Panotopoulos, Andrés Lueiza, Nikolaos Dimakis, Andronikos Paliathanasis

TL;DR

This work investigates static, spherically symmetric compact objects in symmetric teleparallel scalar-tensor gravity with a noncoincident flat connection. By formulating a $$S=\frac{1}{\kappa}\int d^4x \sqrt{-g}[ \frac{A(\phi)}{2}Q -\frac{B(\phi)}{2}\partial_\mu\phi\partial^\mu\phi - V(\phi) ] + S_m$$ action and applying a minisuperspace reduction together with Noether symmetries, the authors derive conservation laws and identify a quadratic nonminimal coupling to the nonmetricity $Q$ that yields nontrivial vacuum solutions. They construct interior quark-star solutions using a simplified MIT bag EOS $p=\tfrac{1}{3}(\rho-4\mathcal{B})$, match them to an exterior extremal RN-like geometry, and solve the coupled mass, pressure, and scalar-field equations numerically. The resulting configurations are shown to be stable (per the Harrison–Zel’dovich–Novikov criterion) and compatible with current astrophysical constraints (GW190814, NICER, HESS J1731-347, and two-solar-mass pulsars), illustrating viable local gravitational phenomenology beyond GR within this framework. Overall, the paper demonstrates that symmetric teleparallel scalar–tensor theories with a quadratic coupling to $Q$ can describe physically plausible compact objects while enriching the landscape of modified gravity solutions.

Abstract

We investigate the existence of static, spherically symmetric compact objects within the framework of symmetric teleparallel scalar-tensor gravity. This theory extends the Brans-Dicke and scalar-tensor models within the symmetric teleparallel formalism. We consider a nontrivial connection that allows for genuinely nontrivial solutions in the limit of General Relativity. The field equations admit a minisuperspace description and by applying the method of variational symmetries we construct the corresponding conservation laws in vacuum. The application of these conservation laws enables the reconstruction of analytic black-hole solutions. Finally, we study the interior structure of compact objects matched to an extremal Reissner-Nordström exterior and show that the symmetric teleparallel scalar-tensor theory supports the existence of viable astrophysical objects.

Compact Stars in Symmetric Teleparallel Scalar-Tensor Gravity

TL;DR

This work investigates static, spherically symmetric compact objects in symmetric teleparallel scalar-tensor gravity with a noncoincident flat connection. By formulating a action and applying a minisuperspace reduction together with Noether symmetries, the authors derive conservation laws and identify a quadratic nonminimal coupling to the nonmetricity that yields nontrivial vacuum solutions. They construct interior quark-star solutions using a simplified MIT bag EOS , match them to an exterior extremal RN-like geometry, and solve the coupled mass, pressure, and scalar-field equations numerically. The resulting configurations are shown to be stable (per the Harrison–Zel’dovich–Novikov criterion) and compatible with current astrophysical constraints (GW190814, NICER, HESS J1731-347, and two-solar-mass pulsars), illustrating viable local gravitational phenomenology beyond GR within this framework. Overall, the paper demonstrates that symmetric teleparallel scalar–tensor theories with a quadratic coupling to can describe physically plausible compact objects while enriching the landscape of modified gravity solutions.

Abstract

We investigate the existence of static, spherically symmetric compact objects within the framework of symmetric teleparallel scalar-tensor gravity. This theory extends the Brans-Dicke and scalar-tensor models within the symmetric teleparallel formalism. We consider a nontrivial connection that allows for genuinely nontrivial solutions in the limit of General Relativity. The field equations admit a minisuperspace description and by applying the method of variational symmetries we construct the corresponding conservation laws in vacuum. The application of these conservation laws enables the reconstruction of analytic black-hole solutions. Finally, we study the interior structure of compact objects matched to an extremal Reissner-Nordström exterior and show that the symmetric teleparallel scalar-tensor theory supports the existence of viable astrophysical objects.
Paper Structure (6 sections, 44 equations, 4 figures)

This paper contains 6 sections, 44 equations, 4 figures.

Table of Contents

  1. Introduction
  2. Action of the theory and field equations
  3. Static, and spherically symmetric spacetimes: Structure equations
  4. Solutions in the absence of matter content
  5. Interior solutions of Quark stars: The case of the simplified MIT bag model
  6. Discussion and Concluding remarks

Figures (4)

  • Figure 1: Factor of compactness, $C=M/R$, as a function of the stellar mass.
  • Figure 2: Stellar mass as a function of the central energy density.
  • Figure 3: Gravitational redshift, $z_G$, versus stellar radius $R$.
  • Figure 4: Mass-to-radius relationships for the 3 models considered here, see text. The black dashed line corresponds to General Relativity. We have included the following astrophysical constraints: a) HESS compact object, b) NICER results, c) the most massive pulsars at two solar masses, and d) the GW190814 event. The M-R profiles pass from all allowed contours, while at the same time they can accommodate massive stars at 2 solar masses and also at 2.5 solar masses.