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https://stockholmuniversity.zoom.us/j/940229961
Our model of the universe rests on a fundamental assumption called the Cosmological Principle, which assumes the homogeneity and isotropy of the universe (there is no preferred direction or place in the universe when viewed on cosmic scales). Our observed universe clearly violates these assumptions on the few-thousand light year distance scales corresponding to galaxies (which have a density much higher than the mean density of the universe, and which often have a preferred direction defined by their orientation). However, when averaging over far larger scales, of order a billion light years, the cosmological principle is expected to be valid. Under this assumption, matter and energy obey the same physical laws everywhere. Additionally, all physical interactions should act uniformly throughout the universe (Lorentz symmetry) and be equivalent under mirror reflection (parity symmetry). Likewise, Einstein’s highly successful theory of general relativity assumes Lorentz and parity symmetry; indeed, Einstein’s great advance in 1905 was to regard the symmetry principle as the primary feature of nature that constrains the allowable dynamical laws. However, only recently have cosmological datasets grown large enough to begin testing these fundamental symmetries. That is why the vast majority of observational and theoretical work simply assumes the isotropy and homogeneity of the universe without testing these principles.
In my talk I will review the set of cosmological observations that allow us either to constrain or detect fundamental symmetries violations in the early universe. Either outcome would have important implications for our understanding of the universe. Finding a departure from isotropy and/or homogeneity in the available cosmological data will lead to an essential modification of the standard picture of the universe, and will lead to revisions of fundamental physics; proving fundamental symmetries at extreme length and/or energy scales will result in ruling out many models beyond the standard cosmological and particle physics scenarios, and will transform the cosmological principle from something near a dogma to a confirmed scientific law. My particular interest will be to address possible parity symmetry violation as manifested through prefered chirality in the early universe and its imprints on cosmological observables.