In today's episode, we are thrilled to welcome Molly Burkmar (Ph.D. student at the University of Portsmouth), a researcher in cosmology. Molly Burkmar takes us on an in-depth exploration into the dynamics of Friedmann-Lemaître-Robertson-Walker (FLRW) cosmologies consisting of dark matter, radiation, and dark energy with a quadratic equation of state.

Molly Burkmar focuses her analysis on non-singular bouncing and cyclic cosmologies, casting a spotlight on the potential for closed models to always have a bounce under any initial conditions. With a careful examination of the range of dynamical behaviors admitted by the system, she identifies a unique class of closed models that admit a non-singular bounce, characterized by early- and late-time accelerated expansion connected by a decelerating phase.

Our conversation delves into the conditions under which these bouncing models become relevant, exploring the necessary presence of dark matter and radiation at a specific energy scale, requiring a period such as reheating. Molly Burkmar further investigates the effects of imposing an upper limit on dark matter and radiation energy densities.

The episode continues with a consideration of potential parameter values for the dark energy component that could explain the discrepancy between the observed value of the cosmological constant (Λ) and theoretical estimates.

Despite finding that the remaining models do not allow for an early- and late-time accelerated expansion connected by a decelerating period, Dr. Burkmar's qualitative analysis sets the stage for constructing more realistic models with realistic quantitative behavior.

Join us for this fascinating episode as we delve into the enigmatic world of dark matter, dark energy, and the cosmic forces that shape our universe.

Institute of Cosmology and Gravitation (University of Portsmouth), researching bouncing cosmologies: Bouncing cosmology from nonlinear dark energy with two cosmological constants https://arxiv.org/abs/2302.03710