University of Cambridge > Talks.cam > DAMTP Friday GR Seminar > Resolving the Hubble tension with emergent dark radiation in unitary gravity

Resolving the Hubble tension with emergent dark radiation in unitary gravity

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We propose a one-parameter extension to ΛCDM, expected to strongly affect cosmological tensions. An effective dark radiation component in the early universe redshifts away as hot dark matter, then quintessence, leaving a falsifiable cosmic torsion field in the current epoch. Our modified gravity is a new Poincaré gauge theory (PGT), foremost among the 33 PGTs recently found algorithmically to be both power-counting renormalisable and free from ghosts and tachyons. To obtain it, we systematically chart the cosmologies of these new PGTs, as special cases of the most general parity-preserving, Ostrogradsky-stable PGT with a Yang-Mills action. As well as the massless 2+ graviton, our theory may contain a massive 0- graviton. The flat Friedmann equations are emergent for any spatial curvature (k-screening), with tension-resolving freedom at the scale-invariant epoch that reliably attracts away to modern ΛCDM evolution. Ongoing work maps the PGT to an equivalent `extended’ Weyl gauge theory (eWGT) and even a metrical Galileon counterpart. We close with upcoming Hamiltonian analysis, COSMOMC validation and solar system tests.

This talk is part of the DAMTP Friday GR Seminar series.

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