3 research outputs found
Cosmological Landscape From Nothing: Some Like It Hot
We suggest a novel picture of the quantum Universe -- its creation is
described by the {\em density matrix} defined by the Euclidean path integral.
This yields an ensemble of universes -- a cosmological landscape -- in a mixed
state which is shown to be dynamically more preferable than the pure quantum
state of the Hartle-Hawking type. The latter is dynamically suppressed by the
infinitely large positive action of its instanton, generated by the conformal
anomaly of quantum fields within the cosmological bootstrap (the
self-consistent back reaction of hot matter). This bootstrap suggests a
solution to the problem of boundedness of the on-shell cosmological action and
eliminates the infrared catastrophe of small cosmological constant in Euclidean
quantum gravity. The cosmological landscape turns out to be limited to a
bounded range of the cosmological constant . The domain is ruled out by the
back reaction effect which we analyze by solving effective Euclidean equations
of motion. The upper cutoff is enforced by the quantum effects of vacuum energy
and the conformal anomaly mediated by a special ghost-avoidance renormalization
of the effective action. They establish a new quantum scale
which is determined by the coefficient of the topological Gauss-Bonnet term in
the conformal anomaly. This scale is realized as the upper bound -- the
limiting point of an infinite sequence of garland-type instantons which
constitute the full cosmological landscape. The dependence of the cosmological
constant range on particle phenomenology suggests a possible dynamical
selection mechanism for the landscape of string vacua.Comment: Final version, to appear in JCA