The boundary is mixed

TL;DR

This paper demonstrates how Oeckl's boundary formalism naturally integrates quantum statistical mechanics and applies it to phenomena like the Unruh effect, revealing a fundamental indeterminacy between pure and mixed states in quantum gravity.

Contribution

It formulates general-covariant quantum statistical mechanics within the boundary formalism, providing new insights into state distinctions and gravitational processes.

Findings

Boundary formalism accounts for the Unruh effect

Pure and mixed states distinction weakens in covariant context

Local gravitational processes are inherently statistical

Abstract

We show that Oeckl's boundary formalism incorporates quantum statistical mechanics naturally, and we formulate general-covariant quantum statistical mechanics in this language. We illustrate the formalism by showing how it accounts for the Unruh effect. We observe that the distinction between pure and mixed states weakens in the general covariant context, and surmise that local gravitational processes are indivisibly statistical with no possible quantal versus probabilistic distinction.