442 research outputs found

### Gauge Couplings at High Temperature and the Relic Gravitino Abundance

In higher-dimensional supersymmetric theories gauge couplings of the
effective four-dimensional theory are determined by expectation values of
scalar fields. We find that at temperatures above a critical temperature $T_*$,
which depends on the supersymmetry breaking mass scales, gauge couplings
decrease like T^{-\a}, \a > 1. This has important cosmological
consequences. In particular it leads to a relic gravitino density which becomes
independent of the reheating temperature for $T_R > T_*$. For small gravitino
masses, m_{3/2} \ll m_{\gl}, the mass density of stable gravitinos is
essentially determined by the gluino mass. The observed value of cold dark
matter, \O_{\rm CDM}h^2 \sim 0.1, is obtained for gluino masses m_{\gl} =
{\cal O}(1 {\rm TeV}).Comment: 11 pages, 2 figures, comment on supersymmetry breaking mechanisms and
two references adde

### A note on the predictions of models with modular flavor symmetries

Models with modular flavor symmetries have been thought to be highly predictive. We point out that these predictions are subject to corrections from nonâ€“holomorphic terms in the Lagrangean. Specifically, in the models discussed in the literature, the KÃ¤hler potential is not fixed by the symmetries, for instance. The most general KÃ¤hler potential consistent with the symmetries of the model contains additional terms with additional parameters, which reduce the predictive power of these constructions. We also comment on potential ways of how one may conceivably retain the predictivity

### The Flavor of Cosmology

We discuss the cosmology of models in which the standard model Yukawa
couplings depend on scalar field(s), often referred to as flavons. We find that
thermal corrections of the flavon potential tend to decrease the Yukawa
couplings, providing an important input to model-building. Working in the
specific framework of Froggatt-Nielsen models, we compute the abundance of
flavons in the early universe generated both via freeze-in and from coherent
oscillations induced by thermal corrections to their potential, and discuss
constraints on flavon models from cosmology. We find that cosmology places
important constraints on theories containing flavons even for regions of
parameter space inaccessible to collider searches.Comment: 26 pages, 5 figures, 5 appendice

### Gauged Discrete Symmetries and Proton Stability

We discuss the results of a search for anomaly free Abelian Z_N discrete
symmetries that lead to automatic R-parity conservation and prevents dangerous
higher-dimensional proton decay operators in simple extensions of the minimal
supersymmetric extension of the standard model (MSSM) based on the left-right
symmetric group, the Pati-Salam group and SO(10). We require that the
superpotential for the models have enough structures to be able to give correct
symmetry breaking to MSSM and potentially realistic fermion masses. We find
viable models in each of the extensions and for all the cases, anomaly freedom
of the discrete symmetry restricts the number of generations.Comment: 8 pages, 2 figures; v2 : typos fixed, references adde

### Non-thermal Gravitino Dark Matter in Gauge Mediation

We show that gravitinos produced by decays of a supersymmetry breaking scalar
field (the pseudo-moduli field) can naturally explain the observed abundance of
dark matter in a certain class of the gauge mediation models. We study the
decay processes as well as cosmological constraints on this scenario in detail,
particularly focusing on different behavior of the real and imaginary
components of the pseudo-moduli field. Cosmologically viable scenario emerges
when the gravitino and the pseudo-moduli masses are O(10-100) MeV and O(100)
GeV, respectively.Comment: 32 pages, 10 figure

### Thermally induced subgap features in the cotunneling spectroscopy of a carbon nanotube

We report on nonlinear cotunneling spectroscopy of a carbon nanotube quantum
dot coupled to Nb superconducting contacts. Our measurements show rich subgap
features in the stability diagram which become more pronounced as the
temperature is increased. Applying a transport theory based on the
Liouville-von Neumann equation for the density matrix, we show that the
transport properties can be attributed to processes involving sequential as
well as elastic and inelastic cotunneling of quasiparticles thermally excited
across the gap. In particular, we predict thermal replicas of the elastic and
inelastic cotunneling peaks, in agreement with our experimental results.Comment: 21 pages, 9 figures, submitted to New Journal of Physic

### Asymptotic symmetries on Kerr--Newman horizon without anomaly of diffeomorphism invariance

We analyze asymptotic symmetries on the Killing horizon of the
four-dimensional Kerr--Newman black hole. We first derive the asymptotic
Killing vectors on the Killing horizon, which describe the asymptotic
symmetries, and find that the general form of these asymptotic Killing vectors
is the universal one possessed by arbitrary Killing horizons. We then construct
the phase space associated with the asymptotic symmetries. It is shown that the
phase space of an extreme black hole either has the size comparable with a
non-extreme black hole, or is small enough to exclude degeneracy, depending on
whether or not the global structure of a Killing horizon particular to an
extreme black hole is respected. We also show that the central charge in the
Poisson brackets algebra of these asymptotic symmetries vanishes, which implies
that there is not an anomaly of diffeomorphism invariance. By taking into
account other results in the literature, we argue that the vanishing central
charge on a black hole horizon, in an effective theory, looks consistent with
the thermal feature of a black hole. We furthermore argue that the vanishing
central charge implies that there are infinitely many classical configurations
that are associated with the same macroscopic state, while these configurations
are distinguished physically.Comment: 14 pages, v2: references added, minor corrections, v3: new pars and
refs. added and corresponding correction

### Clostridium difficile infection in the United States: A national study assessing preventive practices used and perceptions of practice evidence

We surveyed 571 US hospitals about practices used to prevent Clostridium difficile infection (CDI). Most hospitals reported regularly using key CDI prevention practices, and perceived their strength of evidence as high. The largest discrepancy between regular use and perceived evidence strength occurred with antimicrobial stewardship programs.Infect. Control Hosp. Epidemiol. 2015;36(8):969â€“971</jats:p

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