Abstract
One interesting proposal to solve the black hole information loss paradox without modifying either general relativity or quantum field theory, is the soft hair, a diffeomorphism charge that records the anisotropic radiation in the asymptotic region. This proposal, however, has been challenged, given that away from the source the soft hair behaves as a coordinate transformation that forms an Abelian group, thus unable to store any information. To maintain the spirit of the soft hair but circumvent these obstacles, we consider Hawking radiation as a probe sensitive to the entire history of the black hole evaporation, where the soft hairs on the horizon are induced by the absorption of a null anisotropic flow, generalizing the shock wave considered in [1, 2]. To do so we introduce two different time-dependent extensions of the diffeomorphism associated with the soft hair, where one is the backreaction of the anisotropic null flow, and the other is a coordinate transformation that produces the Unruh effect and a Doppler shift to the Hawking spectrum. Together, they form an exact BMS charge generator on the entire manifold that allows the nonperturbative analysis of the black hole horizon, whose surface gravity, i.e. the Hawking temperature, is found to be modified. The modification depends on an exponential average of the anisotropy of the null flow with a decay rate of 4M, suggesting the emergence of a new 2-D degree of freedom on the horizon, which could be a way out of the information loss paradox.
Highlights
Be mitigated unless the horizon is bypassed
To do so we introduce two different time-dependent extensions of the diffeomorphism associated with the soft hair, where one is the backreaction of the anisotropic null flow, and the other is a coordinate transformation that produces the Unruh effect and a Doppler shift to the Hawking spectrum
Such a symmetry was discovered in [1, 19], where the soft hair is successfully implanted at the linear order on the horizon of a Schwarzschild black hole by an incoming anisotropic shock wave focused on the central singularity, leaving only the covert channel to be found
Summary
We will first introduce the BMS metric in the advanced Bondi coordinate, where the vanilla soft hair is found as the conserved charge of the residue diffeomorphism on the past null infinity I−, i.e. the BMS symmetry. We will not venture into the issue of the other BMS symmetry on the future null infinity I+. We will discuss the shock-wave-induced soft hair [1, 2], and generalize it to be time-dependent. We realize the existence of another type of the covariant transformation, previously mistaken as merely the transformation within the BMS group. These two together form the foundation for further discussions in this work
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