Generalized mode-coupling theory of the glass transition. II. Analytical scaling laws

TL;DR

This paper derives analytical scaling laws for generalized mode-coupling theory (GMCT) of the glass transition, extending MCT's success in describing relaxation dynamics and improving quantitative predictions.

Contribution

It analytically derives scaling laws for GMCT's multi-point density correlations, validating and extending MCT's classical results.

Findings

GMCT preserves MCT's scaling laws.

GMCT quantitatively improves relaxation exponents.

Tested on Percus-Yevick hard-sphere system.

Abstract

Generalized mode-coupling theory (GMCT) constitutes a systematically correctable, first-principles theory to study the dynamics of supercooled liquids and the glass transition. It is a hierarchical framework that, through the incorporation of increasingly many particle density correlations, can remedy some of the inherent limitations of the ideal mode-coupling theory (MCT). However, despite MCT's limitations, the ideal theory also enjoys several remarkable successes, notably including the analytical scaling laws for the $\alpha$- and $\beta$-relaxation dynamics. Here we mathematically derive similar scaling laws for arbitrary-order multi-point density correlation functions obtained from GMCT under arbitrary mean-field closure levels. More specifically, we analytically derive the asymptotic and preasymptotic solutions for the long-time limits of multi-point density correlators, the critical dynamics with two power-law decays, the factorization scaling laws in the $\beta$-relaxation regime, and the time-density superposition principle in the $\alpha$-relaxation regime. The two characteristic power-law-divergent relaxation times for the two-step decay and the non-trivial relation between their exponents are also obtained. The validity ranges of the leading-order scaling laws are also provided by considering the leading preasymptotic corrections. Furthermore, we test these solutions for the Percus-Yevick hard-sphere system. We demonstrate that GMCT preserves all the celebrated scaling laws of MCT while quantitatively improving the exponents, rendering the theory a promising candidate for an ultimately quantitative first-principles theory of glassy dynamics.