论文标题

来自假想时间密度 - 密度相关函数的物理见解

Physical insights from imaginary-time density--density correlation functions

论文作者

Dornheim, Tobias, Moldabekov, Zhandos, Tolias, Panagiotis, Böhme, Maximilian, Vorberger, Jan

论文摘要

相关量子多体系统的动态属性的准确理论描述,例如动态结构因子$ s(\ mathbf {q},ω)$在许多领域中都是重要的任务。不幸的是,高度准确的量子蒙特卡洛方法通常仅限于虚构的时间域,而虚构的时间密度密度 - 密度相关函数的分析延续$ f(\ sathbf {q},τ),τ)$ to真实频率是一个众所周知的硬问题。在这项工作中,我们认为不需要这样的分析延续,因为$ f(\ mathbf {q},τ)$所包含的定义与$ s(\ mathbf {q},ω)$相同的物理信息,仅在不熟悉的表示中。具体而言,我们展示了如何直接从$τ$域中提取关键信息,例如温度或准粒子激发能,这与在极端条件下的物质方程测量非常相关。作为一个实践的例子,我们考虑\ emph {ab intio}均匀电子气(UEG)的蒙特蒙特卡洛结果,并证明即使是在低密度直接表现出\ emph {roton特征} \ emph {roton特征}的非平凡过程,在$ f(\ mathbf {q} Q}中,也是在低密度直接表现出来的。实际上,由于许多原因,直接在$τ$域中工作是有利的,并且具有对理论和实验之间前所未有的一致性的诱人承诺。

The accurate theoretical description of the dynamic properties of correlated quantum many-body systems such as the dynamic structure factor $S(\mathbf{q},ω)$ constitutes an important task in many fields. Unfortunately, highly accurate quantum Monte Carlo methods are usually restricted to the imaginary time domain, and the analytic continuation of the imaginary time density--density correlation function $F(\mathbf{q},τ)$ to real frequencies is a notoriously hard problem. In this work, we argue that no such analytic continuation is required as $F(\mathbf{q},τ)$ contains, by definition, the same physical information as $S(\mathbf{q},ω)$, only in an unfamiliar representation. Specifically, we show how we can directly extract key information such as the temperature or quasi-particle excitation energies from the $τ$-domain, which is highly relevant for equation-of-state measurements of matter under extreme conditions. As a practical example, we consider \emph{ab initio} path integral Monte Carlo results for the uniform electron gas (UEG), and demonstrate that even nontrivial processes such as the \emph{roton feature} of the UEG at low density straightforwardly manifest in $F(\mathbf{q},τ)$. In fact, directly working in the $τ$-domain is advantageous for many reasons and holds the enticing promise for unprecedented agreement between theory and experiment.

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