# Higgs Hour: A new theory of the universe

#### Higgs Hour: A new theory of the universe

- Event time: 1:00pm until 2:00pm
- Event date: 17th February 2023
- Speaker: Professor Neil Turok (School of Physics & Astronomy, University of Edinburgh)
- Location: Higgs Centre Seminar Room, Room 4305, James Clerk Maxwell Building (JCMB) (James Clerk Maxwell Building (JCMB)) James Clerk Maxwell Building Peter Guthrie Tait Road Edinburgh EH9 3FD GB

### Event details

Observations of the universe on very small and large scales have revealed a surprising economy in its basic laws and structure. In this light, we have attempted to find new, more minimal solutions to cosmology’s central puzzles. Instead of postulating a pre-hot big bang period, such as inflation, we extrapolate the observed, simple universe all the way back to the initial singularity. Instead of adding new particles and forces to the Standard Model, we improve it by cancelling its Weyl anomalies, so that it couples more consistently to gravity. Weyl symmetry then allows us to analytically extend cosmic spacetime so that CPT is actually a symmetry of the universe as well as its basic laws. In this way, we obtain the simplest-yet explanation of the dark matter, requiring no new particles beyond RH neutrinos, already needed to explain neutrino oscillations. Our new understanding of the boundary conditions at the bang allows us to calculate the gravitational entropy for realistic cosmologies, with radiation, matter, lambda and space curvature. We find that it favours flat, homogeneous and isotropic universes like ours, making inflation redundant. It also favours a small, positive cosmological constant. Our new mechanism for cancelling trace anomalies explains why there are three generations of standard model fermions. It exploits dimension zero fields which are unusual in having a single physical state – the vacuum. In this state, they have scale-invariant fluctuations which source comoving curvature perturbations in the early universe. We recently calculated their amplitude and spectral tilt ab initio, in terms of Standard Model couplings extrapolated to the Planck scale. Remarkably, subject to two key theoretical assumptions, both the amplitude and the spectral tilt agree with the values measured by the Planck satellite, with no free parameters. (See **arXiv:2302.00344** and references therein).

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