The Cosmological Constant from a Quantum Gravitational $\theta$-Vacua and the Gravitational Hall Effect

TL;DR

This paper proposes a novel quantum gravitational framework linking the cosmological constant to topological $ heta$-sectors, inspired by the quantum Hall effect, suggesting $ heta$-dependence protects $ ext{Lambda}$ from quantum corrections.

Contribution

It introduces a new perspective on the cosmological constant using background-independent quantum gravity and topological $ heta$-sectors, drawing analogies with the quantum Hall effect.

Findings

$ heta$-parameter is related to $ ext{Lambda}$ via $ heta=12\pi^2/( ext{Lambda} ext{l}_{ ext{Pl}}^2)$

The cosmological constant acts as a quantum gravitational Hall resistivity

$ ext{Lambda}$ is topologically protected against perturbative quantum corrections

Abstract

We provide a new perspective on the cosmological constant by exploring the background-independent Wheeler-DeWitt quantization of general relativity. The Chern-Simons-Kodama state of quantum gravity, a generalization of the Hartle-Hawking and Vilenkin states, has a striking structural similarity to the topological field theory of the quantum Hall effect. As a result, we study the gravitational topological $\theta$-sectors in analogy to Yang-Mills theory. We find that the cosmological constant $\Lambda$ is intimately linked to the $\theta$-parameter by $\theta=12\pi^2/(\Lambda \ell^2_{\rm Pl}) \mod 2\pi$ due to the fact that Chern-Simons-Kodama state must live in a particular $\theta$-sector. This result is shown in the canonical, non-perturbative formalism. Furthermore, we explain how the physics of the Hamiltonian constraint is analogous to the quantum Hall effect, with the cosmological constant playing the role of a quantum gravitational Hall resistivity. These relations suggest that $\Lambda$ is topologically protected against perturbative graviton loop corrections, analogous to the robustness of quantized Hall conductance against disorder in a metal.