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Thursday, 20 April 2023
Video-Recording for any system with MP4-support
- Video.mp4 (ca. 516 Mb)
15:15 – 16:30
"Explaining the simplicity of the cosmos"
(University of Edinburgh, UK)
Observations of the universe on very small and large scales have revealed a
surprising economy in its basic laws and structure. In contrast, our theories
have become increasingly complex and contrived, introducing many new
particles, fields and even dimensions of space which are, as yet, unobserved.
In this talk, I will outline a more economical and predictive program, aiming
to solve cosmology’s main puzzles using only the Standard Model including
neutrino masses and general relativity. Instead of postulating a period of
inflation before the hot big bang, we extrapolate the observed simple universe
all the way back to the singularity. Instead of adding new particles and forces,
we assume a minimal modification of the Standard Model which improves
the vacuum and preserves local scale symmetry. The symmetry ensures that
the hot plasma filling the early universe is insensitive to the size of the universe
as it shrinks to zero at the singularity. Mathematically, the singularity is replaced
by a kind of mirror. The simplest-yet proposed dark matter candidate -- a stable,
right handed neutrino – becomes viable, a possibility to be tested by galaxy surveys
in the next few years. We calculate the gravitational entropy for realistic
cosmologies, with radiation, matter, lambda and space curvature.
We find that the entropy favours flat, homogeneous and isotropic universes like ours,
with a small positive cosmological constant. We compute the primordial fluctuations
which seeded the formation of galaxies and other structures in the universe, ab initio,
in terms of Standard Model couplings. Remarkably, subject to two key theoretical
assumptions, the amplitude and spectral tilt of these fluctuations agree with the
observed values, with no free parameters. In principle, all features of the standard
LambdaCDM model for cosmology are thereby explained in a highly predictive new
framework which does not require inflation. I'll review forthcoming observational
tests as well as remaining theoretical challenges.
Neil Turok (PhD at Imperial College London, 1983) is the Inaugural Higgs Chair of
Theoretical Physics at the University of Edinburgh. Before taking up the appointment
in Scotland, Turok was the director of the Perimeter institute in Canada from 2008 to
2019. Previously, he was Professor of Physics at Princeton University and Chair of
Mathematical Physics at the University of Cambridge.
Among his many honours, Turok was awarded Sloan and Packard Fellowships and
the James Clerk Maxwell medal of the Institute of Physics (UK).
In 2016 he was named the Gerald Whitrow Lecturer by the Royal Astronomical Society
and was also awarded the John Torrence Tate Medal for International Leadership
in Physics by the American Institute of Physics.
Born in South Africa, Turok founded the African Institute for Mathematical Sciences
(AIMS) in Cape Town in 2003. AIMS has since expanded to a network of six centres
– in South Africa, Senegal, Ghana, Cameroon, Tanzania, and Rwanda – and has
become Africa's most renowned institution for postgraduate training in mathematical
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