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Semiclassical relativistic stars.

Julio Arrechea1, Carlos Barceló2, Raúl Carballo-Rubio3,4

  • 1Instituto de Astrofísica de Andalucía (IAA-CSIC), Glorieta de la Astronomía, 18008, Granada, Spain. arrechea@iaa.es.

Scientific Reports
|September 24, 2022
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Summary
This summary is machine-generated.

Semiclassical gravity allows for ultracompact stars exceeding classical limits. A quantum scalar field and a modified stress-energy tensor create regular, stable stellar configurations beyond the Buchdahl limit.

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Area of Science:

  • Theoretical physics
  • Astrophysics
  • Quantum gravity

Background:

  • Classical general relativity predicts a limit (Buchdahl limit) for stable stars.
  • Ultracompact stars approaching black hole compactness pose theoretical challenges.

Purpose of the Study:

  • To investigate the possibility of self-consistent ultracompact stars beyond the Buchdahl limit using semiclassical gravity.
  • To explore the role of quantum effects in stellar structure.

Main Methods:

  • Integration of semiclassical equations for spherically symmetric stellar equilibrium.
  • Modeling the semiclassical contribution with a quantum massless scalar field in the Boulware vacuum.
  • Approximation of the Renormalized Stress-Energy Tensor (RSET) using the Polyakov approximation, with subsequent refinement.

Main Results:

  • Semiclassical gravity allows for ultracompact stars beyond the Buchdahl limit.
  • The Polyakov approximation of RSET revealed bounded pressures and curvatures in a small central core.
  • A minimal deformation of the RSET approximation within the core leads to strictly regular stellar configurations.

Conclusions:

  • Semiclassical gravity provides a pathway to construct regular ultracompact stars.
  • Quantum effects, specifically the RSET, are crucial for overcoming classical limits on stellar compactness.
  • These findings suggest the existence of stable, exotic stellar objects beyond classical predictions.