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Brans-Dicke Theory with Λ>0: Black Holes and Large Scale Structures
Sourav Bhattacharya1, Konstantinos F Dialektopoulos1, Antonio Enea Romano1
1ITCP and Department of Physics, University of Crete, 70013 Heraklion, Greece.
Physical Review Letters
|November 14, 2015
Summary
Brans-Dicke theory with a positive cosmological constant (Λ) reveals black holes require ω=∞, aligning with general relativity. Cosmic structures are constrained by Brans-Dicke parameter ω for observational consistency.
Area of Science:
- Cosmology and astrophysics
- Theoretical physics
- General relativity and modified gravity theories
Background:
- Investigating cosmic structures within Brans-Dicke theory is crucial for understanding gravity beyond Einstein's general relativity.
- The role of the cosmological constant (Λ) and the Brans-Dicke parameter (ω) significantly influences gravitational phenomena.
- Black hole thermodynamics and the 'no-hair' theorem are fundamental concepts in gravitational physics.
Purpose of the Study:
- To analyze the existence and properties of regular stationary black hole solutions in Brans-Dicke theory with a positive cosmological constant (Λ).
- To explore generalizations of Brans-Dicke theory to circumvent the black hole no-hair theorem.
- To investigate the impact of a stationary cosmological event horizon on black hole solutions and stellar structures.
Main Methods:
- Step-by-step analysis of cosmic structures within the framework of Brans-Dicke theory.
- Perturbative study of generic spherical cosmic structures.
- Mathematical derivation and analysis of black hole solutions and their properties.
Main Results:
- Regular stationary black hole solutions exist only for ω=∞, reducing Brans-Dicke theory to general relativity.
- A non-trivial Brans-Dicke hair can exist on a black hole horizon if there's no stationary cosmological event horizon.
- The presence of a stationary cosmological event horizon precludes regular stationary solutions for stars.
- For stars, predicted maximum sizes are observationally consistent only for ω>0 or ω≲-5.
- Conclusions differ qualitatively from Λ=0 spacetimes.
Conclusions:
- The 'no-hair' theorem in Brans-Dicke theory with Λ is strict unless generalizations are considered.
- The existence of a cosmological event horizon fundamentally alters the possibility of regular astrophysical objects like stars.
- Specific ranges of the Brans-Dicke parameter (ω) are required for theoretical models of cosmic structures to match observational data.
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