259 research outputs found
Aspects of moduli stabilization in type IIB string theory
We review moduli stabilization in type IIB string theory compactification
with fluxes. We focus on the KKLT and Large Volume Scenario (LVS). We show that
the predicted soft SUSY breaking terms in KKLT model are not phenomenological
viable. In LVS, the following result for scalar mass, gaugino mass, and
trilinear term is obtained: , which may account
for Higgs mass limit if TeV. However, in this case
the relic abundance of the lightest neutralino can not be consistent with the
measured limits. We also study the cosmological consequences of moduli
stabilization in both models. In particular, the associated inflation models
such as racetrack inflation and K\"ahler inflation are analyzed. Finally the
problem of moduli destabilization and the effect of string moduli backreaction
on the inflation models are discussed.Comment: 34 pages, 8 figure
Cosmological Imprints of SUSY Breaking in Models of Sgoldstinoless Non-Oscillatory Inflation
In supergravity, the dynamics of the sgoldstino -- superpartner of the
goldstino superfield associated with the breaking of supersymmetry at low
energy -- can substantially modify the dynamics of inflation in the primordial
Universe. So-called sgoldstinoless models assume the existence of a nilpotency
constraint that effectively removes the sgoldstino from the theory.
Such models were proposed to realise non-oscillatory inflation scenarios with a
single scalar field, which feature a long period of kination at the end of
inflation, and therefore a non-standard post-inflationary cosmology. Using
effective operators, we propose models in which the sgoldstino is stabilized
close to the origin to reproduce the nilpotent constraint. We show that small
sgoldstino fluctuations may lead to a sizeable back-reaction on the
cosmological history. We study the effect of this back-reaction on the
inflation observables measured in the cosmic microwave background and confront
the model to a series of constraints including limits on .
We show that the peculiar form of the potential in the large supersymmetry
breaking scale limit can generate peaks in the scalar power spectrum produced
from inflation. We study how certain perturbation modes may re-enter the
horizon during or after kination and show that a large supersymmetry breaking
scale may lead to the formation of primordial black holes with various masses
in the early Universe.Comment: 26 pages, 7 figure
Modified hybrid inflation, reheating and stabilization of the electroweak vacuum
We propose a modification to the standard hybrid inflation model
\cite{Linde:1993cn}, that connects a successful hybrid inflation scenario to
the standard model higgs sector, via the electroweak vacuum stability. The
proposed model results in an effective inflation potential of a hilltop-type,
with both the trans-Planckian and sub-Planckian inflation regimes are
consistent with the recent Planck/BICEP combined results. Reheating via the
inflation sector decays to right-handed neutrinos is considered. An upper bound
on the reheating temperature
GeV, for large~(small) field inflation, will suppress contributions from
one-loop quantum corrections to the inflation potential. This may push the
neutrino Yukawa couplings to be and affect the vacuum stability.
We show that the couplings of the SM Higgs to the inflation sector can
guarantee the electroweak vacuum stability up to Planck scale. The so-called
hybrid Higgs-inflaton model leads to a positive correction for the Higgs
quartic coupling at a threshold scale, which is shown to have a very
significant effect in stabilizing the electroweak vacuum. We find that even
with neutrino Yukawa couplings, threshold corrections leave the
SM vacuum stability intact.Comment: 22 pages, 4 figures, 3 table
Inflation, superheavy metastable strings and gravitational waves in non-supersymmetric flipped SU(5)
Motivated by the NANOGrav 15 year data and other recent investigations of
stochastic gravitational background radiation based on pulsar timing arrays, we
show how superheavy strings survive inflation but the slightly heavier
monopoles do not in a non-supersymmetric hybrid inflation model based on
flipped . With the dimensionless string tension parameter , the gravitational wave spectrum emitted by the strings, which
are metastable due to breaking caused by monopole-antimonopole quantum
mechanical tunneling, is compatible with the latest NANOGrav measurement as
well as the advanced LIGO-VIRGO third run data. For ,
the string network undergoes about 30 -foldings of inflation which
suppresses the spectrum in the LIGO-VIRGO frequency range. With the symmetry
breaking chain , the estimated proton
lifetime is of order yrs.Comment: 17 pages, 2 figures and 5 table
Radion Flavor Violation in Warped Extra Dimension
We analyze the flavor violation in warped extra dimension due to radion
mediation. We show that \Delta S=2 and \Delta B=2 flavor violating processes
impose stringent constraints on radion mass, m_\phi and the scale \Lambda_\phi.
In particular, for \Lambda_\phi ~ O(1) TeV, B_d^0-\bar{B}^0_d implies that
m_\phi ~ 65 GeV. We also study radion contributions to lepton flavor violating
processes: \tau -> (e,\mu) \phi, \tau -> e\mu^+\mu^- and B -> l_i l_j. We show
that BR(B_s -> \mu^+ \mu^-) can be of order 10^{-8}, which is reachable at the
LHCb. The radion search at LHC, through the flavor violation decays into \tau
\mu or top-charm quarks, is also considered.Comment: 23 pages, 9 figure
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