Is Dark Energy Evolving? What We’re Learning from DES and DESI

Speaker: Joshua Frieman (SLAC) In Person and zoom

Zoom Link
SLAC Colloquium Website

Over the last 25 years, the Lambda-Cold Dark Matter model (LCDM)—with 70% of the universe in the form of vacuum energy or equivalently Einstein’s cosmological constant, Lambda---has become the standard paradigm for cosmology. Until recently, it has proven consistent with an array of increasingly precise measurements of cosmic structure and expansion history. However, the latest results from large supernova surveys and baryon acoustic oscillation measurements suggest that evolving or dynamical dark energy models may provide a better fit to the data than LCDM. In this talk, I will discuss these results, focusing on the latest measurements from the Dark Energy Survey (DES) and the Dark Energy Spectroscopic Instrument (DESI), describe their interpretation in terms of physically motivated dark energy models, and show how near-future experiments such as the Vera Rubin Observatory Legacy Survey of Space and Time (LSST) should provide definitive judgment on the current hints for evolving dark energy.