57 research outputs found
Global Renormalization Group
The motivation and the challenge in applying the renormalization group for
systems with several scaling regimes is briefly outlined. The four dimensional
model serves as an example where a nontrivial low energy scaling
regime is identified in the vicinity of the spinodal instability region. It is
pointed out that the effective theory defined in the vicinity of the spinodal
instability offers an amplification mechanism, a precursor of the condensation
that can be used to explore nonuniversal forces at high energies.Comment: LaTex, 39 pages. Final version, to appear in Phys. Rev.
Top mass determination, Higgs inflation, and vacuum stability
The possibility that new physics beyond the Standard Model (SM) appears only
at the Planck scale is often considered. However, it is usually argued
that new physics interactions at do not affect the SM stability phase
diagram, so the latter is obtained neglecting these terms. According to this
diagram, for the current experimental values of the top and Higgs masses, our
universe lives in a metastable state (with very long lifetime), near the edge
of stability. Contrary to these expectations, however, we show that the
stability phase diagram strongly depends on new physics and that, despite
claims to the contrary, a more precise determination of the top (as well as of
the Higgs) mass will not allow to discriminate between stability, metastability
or criticality of the electroweak vacuum. At the same time, we show that the
conditions needed for the realization of Higgs inflation scenarios (all
obtained neglecting new physics) are too sensitive to the presence of new
interactions at . Therefore, Higgs inflation scenarios require very severe
fine tunings that cast serious doubts on these models.Comment: 20 pages, 10 figure
Impact of Gravity on Vacuum Stability
In a pioneering paper on the role of gravity on false vacuum decay, Coleman
and De Luccia showed that a strong gravitational field can stabilize the false
vacuum, suppressing the formation of true vacuum bubbles. This result is
obtained for the case when the energy density difference between the two vacua
is small, the so called thin wall regime, but is considered of more general
validity. Here we show that when this condition does not hold, however, {\it a
strong gravitational field (Planckian physics) does not necessarily induce a
total suppression of true vacuum bubble nucleation}. Contrary to common
expectations then, gravitational physics at the Planck scale {\it does not
stabilize the false vacuum}. These results are of crucial importance for the
stability analysis of the electroweak vacuum and for searches of new physics
beyond the Standard Model.Comment: 6 pages, 4 figure
Does the Cosmological Constant really indicate the existence of a Dark Dimension?
It has been recently proposed that we might live in a universe with a single
compact extra dimension, whose mesoscopic size is dictated by the measured
value of the cosmological constant. Central to this proposal is the result that
in a dimensional theory with compact dimensions a tower of
Kaluza-Klein (KK) states contributes an amount to the vacuum
energy , where is the KK scale of the tower. We show
that the result comes from a mistreatment of the
asymptotics of the loop momenta in the original theory. When the latter
are correctly treated, new UV-sensitive terms appear in that
invalidate the prediction of the dark dimension. We also show that, despite
recent claims to the contrary, it is always possible to perform consistent
effective field theory calculations that include only a finite number of tower
states.Comment: 9 pages, 1 Appendi
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