Speaker
Description
We study the emergence of hydrodynamic response and effective transport in horizonless microstate geometries given by the $1/2$-BPS Lin–Lunin–Maldacena (LLM) solutions of type IIB supergravity. These smooth, top-down backgrounds exhibit strong redshift and long-lived trapping despite having no macroscopic event horizon, making them a controlled setting to ask whether dissipative behavior can arise from coarse-graining over individual microstates. We probe the dynamics in the eikonal regime by analyzing chaotic scattering of null geodesics across ensembles of LLM microstates and extract their statistical diagnostics such as effective diffusion coefficient and viscosity. We then compare these results to the corresponding variables from the membrane paradigm of black holes, where transport coefficients are controlled by horizon data. The goal is to delineate which aspects of hydrodynamic universality can emerge without a true horizon and which require genuinely black-hole-like boundary conditions.
