Probe Dependence of the Imaginary Part of HTEE

Abstract

We investigate the holographic timelike entanglement entropy (HTEE) in a five-dimensional anisotropic background, dual to a strongly coupled anisotropic plasma. Using the complex extremal surface method, we compute the HTEE analytically in the high-temperature, small-anisotropy limit $aT \ll 1$. We consider two different orientations of the boundary timelike interval: one perpendicular to the anisotropy direction and one parallel to it. We find that the imaginary part of the HTEE is not a universal property of the geometry but depends sensitively on the orientation of the extremal surface relative to the anisotropy. This demonstrates that the imaginary part arising from the UV logarithmic divergence is a probe-dependent quantity. Our results suggest that the imaginary part of HTEE can serve as a diagnostic of the coupling between the extremal surface and the anisotropic degrees of freedom of the dual field theory.