Fat Euclidean Gravity with Small Cosmological Constant

TL;DR

This paper introduces a novel effective first quantized approach to gravity that addresses the cosmological constant problem by suggesting gravity may weaken at short distances, aligning with experimental tests and the Equivalence Principle.

Contribution

It presents a new first quantized framework for gravity that demonstrates the cosmological constant problem depends on short-distance gravitational details, with models showing gravity could diminish at small scales.

Findings

Gravity may shut off at short distances, reducing the cosmological constant.

The effective description aligns with experiments and the Equivalence Principle.

Fat Gravity models illustrate suppression of the cosmological constant at testable scales.

Abstract

The cosmological constant problem is usually considered an inevitable feature of any effective theory capturing well-tested gravitational and matter physics, without regard to the details of short-distance gravitational couplings. In this paper, a subtle effective description avoiding the problem is presented in a first quantized language, consistent with experiments and the Equivalence Principle. First quantization allows a minimal domain of validity to be carved out by cutting on the proper length of particle worldlines. This is facilitated by working in (locally) Euclidean spacetime, although considerations of unitarity are still addressed by analytic continuation from Lorentzian spacetime. The new effective description demonstrates that the cosmological constant problem {\it is} sensitive to short-distance details of gravity, which can be probed experimentally. ``Fat Gravity'' toy models are presented, illustrating how gravity might shut off at short but testable distances, in a generally covariant manner that suppresses the cosmological constant. This paper improves on previous work by allowing generalizations to massless matter, non-trivial spins, non-perturbative phenomena, and multiple (metastable) vacua.