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SUMMARY:Cosmological and Astrophysical Probes of Vacuum Energy
DTSTART:20150518T140000
DTSTAMP:20260916T153720Z
UID:f5976f8467db0fdfe8b1d222b82cf39023f0dbc6ba4cd3f2841ab39f
CATEGORIES:Conferences - Seminars
DESCRIPTION:Brando Bellazzini (CEA Saclay)\nVacuum energy changes during c
 osmological phase transitions and becomes relatively important at epochs j
 ust before phase transitions. For a viable cosmology the vacuum energy jus
 t after a phase transition must be set by the critical temperature of the 
 next phase transition\, which exposes the cosmological constant problem fr
 om a different angle. We propose to experimentally test the properties of 
 vacuum energy under circumstances different from our current vacuum. One p
 romising avenue is to consider the effect of high density phases of QCD in
  neutron stars. Such phases have different vacuum expectation values and a
  different vacuum energy from the normal phase\, which can contribute an o
 rder one fraction to the mass of neutron stars. Precise observations of th
 e mass of neutron stars can potentially yield information about the gravit
 ational properties of vacuum energy\, which can significantly affect their
  mass-radius relation. A more direct test of cosmic evolution of vacuum en
 ergy could be inferred from a precise observation of the primordial gravit
 ational wave spectrum at frequencies corresponding to phase transitions. W
 hile traditional cosmology predicts steps in the spectrum determined by th
 e number of degrees of freedom both for the QCD and electroweak phase tran
 sitions\, an adjustment mechanism for vacuum energy could significantly ch
 ange this. In addition\, there might be other phase transitions where the 
 effect of vacuum energy could show up as a peak in the spectrum.
LOCATION:BSP 727 https://plan.epfl.ch/?room==BSP%20727
STATUS:CONFIRMED
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