A Note on the Near Horizon Charges for the Five Dimensional Myers-Perry Black Holes

Inspired by the recent work on the spacetime structure near generic black hole horizons [1], the near horizon charges for an explicit example in higher dimensions than four (d > 4), namely for the five dimensional Myers-Perry metric with two equal rotation parameter are found in Hamiltonian formalism. Finding the supertranslation and the one-form superrotation, it is proved that the Myers-Perry black hole with two equal rotation parameter a = b does not satisfy the gauge flatness condition due to the non-vanishing associated field strength in five dimensional spacetime. It is shown that as the near horizon limit of such a metric satisfies a specific set of boundary conditions, the near horizon algebra can be represented as an infinitely many copies of Heisenberg algebras as a generalisation to the Kerr case in four dimensions

Subleading non linear gravitational memory effect

We apply the new method based on null geodesics for detecting gravitational memory and find the bulk memory in Newman-Unti gauge around the boundary of the conformally compactified space time. We show how we use the newly found conserved charges in the subleading orders of large-$r$ expansion of the BMS charges to define the gravitational memory at each order in the non-linearised gravitational theory. We also find the gravitational shift in the $r$ direction. It is shown that the longitudinal displacement at order $1/r$ is the relative radius change between two detectors derived by Strominger and Zhiboedov

Black hole quantum atmosphere for freely falling observers

We analyze Hawking radiation as perceived by a freely-falling observer and try to draw an inference about the region of origin of the Hawking quanta. To do so, first we calculate the energy density from the stress energy tensor, as perceived by a freely-falling observer. Then we compare this with the energy density computed from an effective temperature functional which depends on the state of the observer. The two ways of computing these quantities show a mismatch at the light ring outside the black hole horizon. To better understand this ambiguity, we show that even taking into account the (minor) breakdown of the adiabatic evolution of the temperature functional which has a peak in the same region of the mismatch, is not enough to remove it. We argue that the appearance of this discrepancy can be traced back to the process of particle creation by showing how the Wentzel–Kramers–Brillouin approximation for the field modes breaks down between the light ring at 3M and 4M, with a peak at r=3.3M exactly where the energy density mismatch is maximized. We hence conclude that these facts strongly support a scenario where the Hawking flux does originate from a “quantum atmosphere” located well outside the black hole horizon. © 2019 The Author