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Date: 
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Time: 
Thursday, 20 April 2023 
VideoRecording for any system with MP4support  Video.mp4 (ca. 516 Mb) 
15:15 – 16:30

"Explaining the
simplicity of the cosmos"
Neal Turok
(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 simplestyet
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.
Biography:
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
science.
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