Speaker: Prof Ignatios Antoniadis
Affiliation: LPTHE CNRS Sorbonne University
Abstract
Extra dimensions are an important ingredient of theories of quantum gravity such as string theory. If their size is large, gravity becomes strong at energies lower than the Planck scale with important theoretical and observational consequences. I will argue on the possibility that extra dimensions acquire large size by higher dimensional inflation, relating the weakness of the actual gravitational force to the size of the observable universe. Although this can be realised for any number of extra dimensions, the requirement of (approximate) flat power spectrum of primordial density fluctuations consistent with present observations makes this simple proposal possible only for one or two extra dimensions at around the micron scale. This scenario can then be nicely combined with the Dark Dimension proposal for the cosmological constant, stemmed from the large distance swampland conjecture. I will describe its main phenomenological consequences in particle physics and cosmology.
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