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CATEGORIES:Cosmology Lunch
SUMMARY:Cosmology from the boundary - Paolo Benincasa (Nie
ls Bohr)
DTSTART;TZID=Europe/London:20190506T130000
DTEND;TZID=Europe/London:20190506T140000
UID:TALK121360AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/121360
DESCRIPTION:Our understanding of physical phenomena is intimat
ely linked to the way we understand the relevant o
bservables describing them. While a big deal of pr
ogress has been made for processes occurring in fl
at space-time\, much less is known in cosmological
settings\, where it is still unclear how to isola
te fundamental physics from the relevant observabl
es: we do not know how to answer the question "wha
t are the conditions they ought to satisfy in orde
r to come from a consistent evolution in cosmologi
cal space-times?". In this talk I will illustrate
the path my collaborators and I have recently unde
rtaken in order to address such a question\, aimin
g towards the idea of a formulation of cosmology "
without time". \n\nThe focus of the discussion wil
l be the late-time wavefunction of the universe fo
r a large class of scalar toy models and its prope
rties in perturbation theory. I will discuss its s
ingularity structure and how it satisfies a recurs
ion relation\, which allows to compute it directly
in terms of "boundary" data. Amazingly enough\, a
new mathematical structure\, we called "cosmologi
cal polytopes"\, which has its own first principle
definition\, encodes the singularity structure we
ascribe to the perturbative wavefunction of the u
niverse\, and makes explicit its relation to the f
lat-space S-matrix. After a gentle introduction to
the cosmological polytopes\, I will stress how th
ey allow us to: compute the wavefunction of the un
iverse at arbitrary points and arbitrary loops (wi
th novel representations for it)\; interpret the r
esidues of its poles in terms of flat-space proces
ses\; provide a general geometrical proof for the
flat-space cutting rules\; reconstruct the pertur
bative wavefunction from the knowledge of the flat
-space S-matrix and a subset of symmetries enjoyed
by the wavefunction.
LOCATION:CMS\, Pav. B\, CTC Common Room (B1.19) [Potter Roo
m]
CONTACT:Sadra Jazayeri
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