Effective State Metamorphosis in Semi-Classical Loop Quantum Cosmology

TL;DR

This paper explores how modifications to geometric density in loop quantum cosmology affect the early universe's dynamics, especially for matter with arbitrary scale factor dependence, revealing new phenomenological possibilities.

Contribution

It demonstrates how matter Hamiltonians incorporate loop quantum modifications and analyzes the resulting effects on energy conditions and frequency dispersion in the early universe.

Findings

Matter with arbitrary scale dependence exhibits negative pressure near a critical scale.

Different definitions of energy density lead to significantly different physical predictions.

Modification to geometric density induces frequency dispersion effects at small scales.

Abstract

Modification to the behavior of geometrical density at short scales is a key result of loop quantum cosmology, responsible for an interesting phenomenology in the very early universe. We demonstrate the way matter with arbitrary scale factor dependence in Hamiltonian incorporates this change in its effective dynamics in the loop modified phase. For generic matter, the equation of state starts varying near a critical scale factor, becomes negative below it and violates strong energy condition. This opens a new avenue to generalize various phenomenological applications in loop quantum cosmology. We show that different ways to define energy density may yield radically different results, especially for the case corresponding to classical dust. We also discuss implications for frequency dispersion induced by modification to geometric density at small scales.