Imaginative Cosmology

TL;DR

This paper reviews unconventional cosmological ideas including non-singular models, string theory-based approaches, and varying speed of light theories, highlighting their potential to address fundamental cosmological problems and proposing experimental tests.

Contribution

It introduces and discusses alternative cosmological models that challenge standard inflationary paradigms, offering new solutions and insights into the universe's fundamental properties.

Findings

Non-singular dilaton cosmology avoids the initial singularity.

String theory-inspired models address cosmological problems without inflation.

Varying speed of light theory offers solutions to horizon and flatness problems.

Abstract

We review a few off-the-beaten-track ideas in cosmology. They solve a variety of fundamental problems; also they are fun. We start with a description of non-singular dilaton cosmology. In these scenarios gravity is modified so that the Universe does not have a singular birth. We then present a variety of ideas mixing string theory and cosmology. These solve the cosmological problems usually solved by inflation, and furthermore shed light upon the issue of the number of dimensions of our Universe. We finally review several aspects of the varying speed of light theory. We show how the horizon, flatness, and cosmological constant problems may be solved in this scenario. We finally present a possible experimental test for a realization of this theory: a test in which the Supernovae results are to be combined with recent evidence for redshift dependence in the fine structure constant.