Nonlocality of quantum matter corrections and cosmological constant running

TL;DR

This paper critically analyzes semiclassical quantum corrections to gravity, clarifying that certain contributions often attributed to the cosmological constant's running are actually higher-derivative terms, emphasizing the importance of tensor structure and derivatives.

Contribution

It provides a detailed critique of recent works by properly accounting for tensor structure and derivatives, distinguishing between cosmological constant running and higher-derivative contributions.

Findings

Quantum fluctuations contribute to higher-derivative terms, not the cosmological constant.

Misinterpretations in previous works arise from neglecting tensor structure.

Proper analysis clarifies the nature of semiclassical quantum corrections.

Abstract

Semiclassical contributions to the gravitational action include various terms with zero, two, and four derivatives of the metric as well as nonlocal form factors for these terms. Contributions to some of these terms could be confused with others on a specific metric background or for a particular gauge fixing. We present a critical analysis of the recent works where the tensor structure and the number of derivatives in the action of gravity were not properly taken into account. Taking these relevant aspects into account, we show that although some contributions owing to the quantum fluctuations of massive or massless scalar as well as fermion and vector fields may be attributed to the "running" of the cosmological constant, in reality they correspond to the fourth derivative terms of the action.