# [Phys-seminars] 2011-11-07 Particles and Fields Seminar

physics at bgu.ac.il physics at bgu.ac.il
Wed Nov 2 10:25:15 IST 2011

Particles and Fields Seminar

DATE: 07-11-2011

TIME: 14:00pm (Mon)

PLACE: Physics building (#54) room 207

TITLE:
Non Singular Creation of the Universe and its Present Vacuum Energy Density

SPEAKER:
Prof. Eduardo Guendelman, Physics Department, Ben Gurion University of the Negev

We consider a non singular origin for the Universe starting from an
Einstein static Universe in the framework of a theory which uses two
volume elements $\\sqrt{-{g}}d^{4}x$ and $\\Phi d^{4}x$, where $\\Phi$
is a metric independent density, also curvature, curvature square
terms, first order formalism and for scale invariance a dilaton field
$\\phi$ are considered in the action. In the Einstein frame we also
add a cosmological term that parametrizes the zero point fluctuations.
The resulting effective potential for the dilaton contains two flat
regions, for $\\phi \\rightarrow \\infty$ relevant for the non singular
origin of the Universe and $\\phi \\rightarrow -\\infty$, describing our
present Universe. Surprisingly, avoidance of singularities and
stability as $\\phi \\rightarrow \\infty$ imply a positive but small
vacuum energy as $\\phi \\rightarrow -\\infty$. Zero vacuum energy
density for the present universe is the \"threshold\" for universe
creation. This requires a modified emergent universe scenario,
where the universe although very old, it does have a beginning.

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