Metric-Independent Volume-Forms in Gravity and Cosmology

TL;DR

This paper explores the use of alternative, metric-independent volume-forms in gravity and cosmology, revealing new mechanisms for cosmological constant generation, inflation, and supersymmetry breaking, with detailed Hamiltonian analysis.

Contribution

It introduces a class of gravity-matter models with two independent non-Riemannian volume-forms, demonstrating their physical implications and canonical structure.

Findings

New mechanism for dynamical cosmological constant

Emergent universe scenario before inflation

Spontaneous supersymmetry breaking in supergravity

Abstract

Employing alternative spacetime volume-forms (generally-covariant integration measure densities) independent of the pertinent Riemannian spacetime metric have profound impact in general relativity. Although formally appearing as "pure-gauge" dynamical degrees of freedom they trigger a number of remarkable physically important phenomena such as: (i) new mechanism of dynamical generation of cosmological constant; (ii) new type of "quintessential inflation" scenario in cosmology; (iii) non-singular initial "emergent universe" phase of cosmological evolution preceding the inflationary phase; (iv) new mechanism of dynamical spontaneous breakdown of supersymmetry in supergravity; (v) gravitational electrovacuum "bags". We study in some detail the properties, together with their canonical Hamiltonian formulation, of a class of generalized gravity-matter models built with two independent non-Riemannian volume-forms and discuss their implications in cosmology.