Speaker
Kylar Greene
(Seoul National University)
Description
Many cosmological observables are sensitive primarily to ratios of physical scales rather than their absolute values. This motivates the FFAT scaling symmetry, in which correlated changes to the expansion history, primordial fluctuations, and scattering rates can leave much of the CMB phenomenology nearly unchanged while shifting the inferred absolute expansion scale. I will discuss how this symmetry provides a useful framework for understanding the Hubble tension and for constructing extensions of ΛCDM that preserve the key ratios measured by cosmological data. More broadly, I will explore a ratio-preserving approach to cosmological concordance and the observations that ultimately break these degeneracies.
Author
Kylar Greene
(Seoul National University)