Critical fluctuation patterns and anisotropic correlations driven by temperature gradients

TL;DR

This paper investigates how temperature gradients in heavy-ion collision systems influence fluctuation patterns and correlations, revealing anisotropic features that could serve as new signals for the QCD phase transition detection.

Contribution

It introduces an analysis of fluctuation spectra and correlations in inhomogeneous systems with temperature gradients, highlighting anisotropic correlations and their connection to observable flow patterns.

Findings

Correlations are long-ranged along isotherms but suppressed radially.

Inhomogeneous systems exhibit superpositions of zero and non-zero angular momentum modes.

Azimuthally sensitive observables can potentially detect the QCD phase transition.

Abstract

Studies of QCD phase transition signals are often conducted under spatially uniform temperature conditions. However, the influence of spatial temperature gradients on the signals emerging at the phase interface in the fireball generated by heavy-ion collisions has not yet been fully explored. Based on an Ising-like effective potential, we study the locally equilibrated systems with temperature gradients. In a 2D disk geometry, the low-energy fluctuation spectrum is explicitly resolved into radial and angular momentum modes. The nonlocal correaltions of singular eigen-mode exhibits strong anisotropy, which are long-ranged along isotherms but suppressed radially due to the thermal geometry of the system. Unlike homogeneous systems where the zero-momentum mode dominates, correlations in such inhomogeneous system result from the superposition of a series of zero and non-zero angular momentum modes with comparable contributions. We extract the singular angular momentum modes and establish their connection to experimentally observable anisotropic flow. We find azimuthally sensitive observables may offer a previously unexplored avenue for detecting the QCD phase transition.