Bouncing Cosmology made simple

TL;DR

This paper introduces the wedge diagram, a visual tool to illustrate how bouncing cosmological models resolve key problems like horizon, flatness, and entropy issues, offering a clear comparison with other scenarios.

Contribution

It presents the wedge diagram as an intuitive method to analyze and compare classical bouncing cosmologies with standard models, highlighting their advantages.

Findings

Wedge diagram effectively illustrates bounce scenarios.

Bouncing models address horizon and flatness problems.

Comparison with other cosmologies is facilitated.

Abstract

We introduce the "wedge diagram," an intuitive way to illustrate how cosmological models with a classical (non-singular) bounce generically resolve fundamental problems in cosmology. These include the well-known horizon, flatness, and inhomogeneity problems; the small tensor-to-scalar ratio observed in the cosmic microwave background; the low entropy at the beginning of a hot, expanding phase; and the avoidance of quantum runaway. The same diagrammatic approach can be used to compare with other cosmological scenarios.