Spontaneous Lorentz symmetry-breaking constraints in Kalb-Ramond gravity
arxiv(2024)
摘要
In this work, we study timelike and lightlike geodesics in Kalb-Ramond (KR)
gravity around a black hole with the goal of constraining the Lorentz
symmetry-breaking parameter l. The analysis involves studying the precession
of the S2 star periastron orbiting Sgr A* and geodesic precession around the
Earth. The ratio of precession frequencies for General Relativity (GR) and KR
gravity is computed, with Event Horizon Telescope (EHT) results providing a
parameter range for the spontaneous symmetry-breaking of -0.185022 ≤ l ≤
0.060938. Utilizing the geodesic precession frequency from the Gravity Probe B
(GP-B), the l parameter is further constrained to -6.30714 × 10^-12≤ l ≤ 3.90708 × 10^-12, which is consistent with the
Schwarzschild limits. Moreover, for timelike geodesics, the innermost circular
orbit (ICO) and innermost stable circular orbit (ISCO) are determined and
analyzed to illustrate the impact of the symmetry breaking term. Zoom-whirl
obstructions are compared with the Schwarzschild solution. Lower and upper
limits of the photon sphere for lightlike geodesics are established to
demonstrate the influence of KR gravity on the photon sphere. Additionally, the
shadow radius is determined for two observers, one situated at a finite
distance from the KR black hole, and the other located at an infinite distance,
to constrain the symmetry-breaking parameter l, with comparisons made to EHT
results. The bounds for l derived from constraints on the photon sphere
radius for lightlike geodesics yield -0.0700225 ≤ l ≤ 0.189785 using
EHT data. The findings of this paper align with experimental results in the l
→ 0 limit.
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