On the analysis of two-time correlation functions: equilibrium vs non-equilibrium systems

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Main Authors: Ragulskaya, Anastasia, Starostin, Vladimir, Zhang, Fajun, Gutt, Christian, Schreiber, Frank
Format: Preprint
Published: 2024
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author Ragulskaya, Anastasia
Starostin, Vladimir
Zhang, Fajun
Gutt, Christian
Schreiber, Frank
author_facet Ragulskaya, Anastasia
Starostin, Vladimir
Zhang, Fajun
Gutt, Christian
Schreiber, Frank
contents X-ray photon correlation spectroscopy (XPCS) is a powerful tool for the investigation of dynamics covering a broad range of time and length scales. The two-time correlation function (TTC) is commonly used to track non-equilibrium dynamical evolution in XPCS measurements, followed by the extraction of one-time correlations. While the theoretical foundation for the quantitative analysis of TTCs is primarily established for equilibrium systems, where key parameters such as diffusion remain constant, non-equilibrium systems pose a unique challenge. In such systems, different projections ("cuts") of the TTC may lead to divergent results if the underlying fundamental parameters themselves are subject to temporal variations. This article explores widely used approaches for TTC calculations and common methods for extracting relevant information from correlation functions on case studies, particularly in the light of comparing dynamics in equilibrium and non-equilibrium systems.
format Preprint
id arxiv_https___arxiv_org_abs_2406_12520
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle On the analysis of two-time correlation functions: equilibrium vs non-equilibrium systems
Ragulskaya, Anastasia
Starostin, Vladimir
Zhang, Fajun
Gutt, Christian
Schreiber, Frank
Soft Condensed Matter
Data Analysis, Statistics and Probability
X-ray photon correlation spectroscopy (XPCS) is a powerful tool for the investigation of dynamics covering a broad range of time and length scales. The two-time correlation function (TTC) is commonly used to track non-equilibrium dynamical evolution in XPCS measurements, followed by the extraction of one-time correlations. While the theoretical foundation for the quantitative analysis of TTCs is primarily established for equilibrium systems, where key parameters such as diffusion remain constant, non-equilibrium systems pose a unique challenge. In such systems, different projections ("cuts") of the TTC may lead to divergent results if the underlying fundamental parameters themselves are subject to temporal variations. This article explores widely used approaches for TTC calculations and common methods for extracting relevant information from correlation functions on case studies, particularly in the light of comparing dynamics in equilibrium and non-equilibrium systems.
title On the analysis of two-time correlation functions: equilibrium vs non-equilibrium systems
topic Soft Condensed Matter
Data Analysis, Statistics and Probability
url https://arxiv.org/abs/2406.12520