[seminar] [DANAS] Flavio Mercati, 24.02. (srijeda) 14h (c.t.), predavaona I krila IRB

[Kornelija Passek-Kumericki]

                       SEMINAR  TEORIJSKE  FIZIKE


   (Zajednički seminari Fizičkog odsjeka PMF-a te Zavoda za teorijsku
    fiziku i Zavoda za eksperimentalnu fiziku IRB-a)

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Through the big bang


Flavio Mercati
Perimeter Institute for Theoretical Physics, Canada


   Datum:  srijeda, 24. veljace 2016.
   Vrijeme: 14 sati c.t.
   Mjesto: IRB, predavaona I krila



Sazetak:


I consider the near-big-bang behaviour of a homogeneous but
anisotropic cosmological model with S^3 spatial topology - the
Bianchi IX model. This model is well-known to behave like a billiard
ball (Misner called it `mixmaster’ behaviour), which goes through an
infinite amount of bounces before reaching the big bang. However,
assuming there is at least one massless scalar field, the
mixmaster behaviour stops after a finite amount of bounces, and the
shape degrees of freedom of the geometry stabilize around a
Kasner-like solution as the singularity is reached (the so-called
`quiescent’ case).
I am able to prove that each solution of the quiescent model can be
continued uniquely past the big-bang singularity, by
demanding continuity of the shape degrees of freedom. The system goes
through a degenerate shape (a two-dimensional `pancake’- or
`cigar’-like shape), and comes out with an inverted orientation.
Continued in this way, each solution of the system looks like two
universes joined at the big bang. This makes General Relativity
compatible with the picture of the big bang being a `Janus point’ of
the kind my collaborators and I studied in the context of Newtonian
cosmological models in PRL 113, 181101, which provides a
previously-unnoticed mechanism for the emergence of an arrow of time.
This resolution of the big bang singularity is purely classical and
does not require quantum effects. Finally I will discuss how, through
the BKL conjecture, this new result generalizes to full General
Relativity (relaxing the homogeneity hypothesis) with any kind of
minimally-coupled matter (because, paraphrasing Wheeler, `the only
matter that matters is massless scalar fields’).


Voditeljica seminara: Kornelija Passek-Kumericki (passek at irb dot hr)
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