1,486 research outputs found
Supersymmetry Breaking and Moduli Stabilization with Anomalous U(1) Gauge Symmetry
We examine the effects of anomalous U(1)_A gauge symmetry on soft
supersymmetry breaking terms while incorporating the stabilization of the
modulus-axion multiplet responsible for the Green-Schwarz (GS) anomaly
cancellation mechanism. In case of the KKLT stabilization of the GS modulus,
soft terms are determined by the GS modulus mediation, the anomaly mediation
and the U(1)_A mediation which are generically comparable to each other,
thereby yielding the mirage mediation pattern of superparticle masses at low
energy scale. Independently of the mechanism of moduli stabilization and
supersymmetry breaking, the U(1)_A D-term potential can not be an uplifting
potential for de Sitter vacuum when the gravitino mass is smaller than the
Planck scale by many orders of magnitude. We also discuss some features of the
supersymmetry breaking by red-shifted anti-brane which is a key element of the
KKLT moduli stabilization.Comment: 32 pages; references are adde
Soft-Wall Stabilization
We propose a general class of five-dimensional soft-wall models with AdS
metric near the ultraviolet brane and four-dimensional Poincar\'e invariance,
where the infrared scale is determined dynamically. A large UV/IR hierarchy can
be generated without any fine-tuning, thus solving the electroweak/Planck scale
hierarchy problem. Generically, the spectrum of fluctuations is discrete with a
level spacing (mass gap) provided by the inverse length of the wall, similar to
RS1 models with Standard Model fields propagating in the bulk. Moreover two
particularly interesting cases arise. They can describe: (a) a theory with a
continuous spectrum above the mass gap which can model unparticles
corresponding to operators of a CFT where the conformal symmetry is broken by a
mass gap, and; (b) a theory with a discrete spectrum provided by linear Regge
trajectories as in AdS/QCD models.Comment: 27 pages, 6 figures, 1 table. v2: references added, version to appear
in NJP Focus Issue on Extra Dimension
Inhibition of nitrogenase by oxygen in marine cyanobacteria controls the global nitrogen and oxygen cycles
International audienceCyanobacterial N2-fixation supplies the vast majority of biologically accessible inorganic nitrogen to nutrient-poor aquatic ecosystems. The process, catalyzed by the heterodimeric protein complex, nitrogenase, is thought to predate that of oxygenic photosynthesis. Remarkably, while the enzyme plays such a critical role in Earth's biogeochemical cycles, the activity of nitrogenase in cyanobacteria is markedly inhibited in vivo at a post-translational level by the concentration of O2 in the contemporary atmosphere leading to metabolic and biogeochemical inefficiency in N2 fixation. We illustrate this crippling effect with data from Trichodesmium spp. an important contributor of "new nitrogen" to the world's subtropical and tropical oceans. The enzymatic inefficiency of nitrogenase imposes a major elemental taxation on diazotrophic cyanobacteria both in the costs of protein synthesis and for scarce trace elements, such as iron. This restriction has, in turn, led to a global limitation of fixed nitrogen in the contemporary oceans and provides a strong biological control on the upper bound of oxygen concentration in Earth's atmosphere
Stability of Scalar Fields in Warped Extra Dimensions
This work sets up a general theoretical framework to study stability of
models with a warped extra dimension where N scalar fields couple minimally to
gravity. Our analysis encompasses Randall-Sundrum models with branes and bulk
scalars, and general domain-wall models. We derive the Schrodinger equation
governing the spin-0 spectrum of perturbations of such a system. This result is
specialized to potentials generated using fake supergravity, and we show that
models without branes are free of tachyonic modes. Turning to the existence of
zero modes, we prove a criterion which relates the number of normalizable zero
modes to the parities of the scalar fields. Constructions with definite parity
and only odd scalars are shown to be free of zero modes and are hence
perturbatively stable. We give two explicit examples of domain-wall models with
a soft wall, one which admits a zero mode and one which does not. The latter is
an example of a model that stabilizes a compact extra dimension using only bulk
scalars and does not require dynamical branes.Comment: 25 pages, 2 figures; v2: minor changes to text, references added,
matches published versio
Superconductivity and electronic structure of the W7Re13B compound
The superconductor W7Re13B has been studied by the magnetic measurements and microwave absorption. The crystal structure of W7Re13B is cubic (ÂŻ-Mn type). This compound exhibits a sharp superconducting transition at a temperature of Tc = 7:2 K. The electronic structure of W7Re13B has been studied by X-ray photoelectron spectroscopy and the band structure has been calculated by the full-potential local-orbital minimum-basis method using the scalar-relativistic mode. The main contribution to the density of states at the Fermi level is from 5d electrons of W and Re. The W and Re bands are similar and substituting W by Re does not change the total density of states
On the presentation of the LHC Higgs Results
We put forth conclusions and suggestions regarding the presentation of the
LHC Higgs results that may help to maximize their impact and their utility to
the whole High Energy Physics community.Comment: Conclusions from the workshops "Likelihoods for the LHC Searches",
21-23 January 2013 at CERN, "Implications of the 125 GeV Higgs Boson", 18-22
March 2013 at LPSC Grenoble, and from the 2013 Les Houches "Physics at TeV
Colliders" workshop. 16 pages, 3 figures. Version 2: Comment added on the
first publication of signal strength likelihoods in digital form by ATLA
Supersymmetric Brane World Scenarios from Off-Shell Supergravity
Using N=2 off-shell supergravity in five dimensions, we supersymmetrize the
brane world scenario of Randall and Sundrum. We extend their construction to
include supersymmetric matter at the fixpoints.Comment: 15 pages, no figures, late
The Wilsonian Renormalization Group in Randall-Sundrum 1
We find renormalization group transformations for the compactified
Randall-Sundrum scenario by integrating out an infinitesimal slice of
ultraviolet degrees of freedom near the Planck brane. Under these
transformations the coefficients of operators on the Planck brane experience RG
evolution. The extra-dimensional radius also scales, flowing to zero in the IR.
We find an attractive fixed point in the context of a bulk scalar field theory.
Calculations are simplified in the low energy effective theory as we
demonstrate with the computation of a loop diagram.Comment: 19 pages, typos adde
Role of interferonâÎł and inflammatory monocytes in driving colonic inflammation during acute Clostridium difficile infection in mice
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/136491/1/imm12700.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136491/2/imm12700_am.pd
Suppressing Electroweak Precision Observables in 5D Warped Models
We elaborate on a recently proposed mechanism to suppress large contributions
to the electroweak precision observables in five dimensional (5D) warped
models, without the need for an extended 5D gauge sector. The main ingredient
is a modification of the AdS metric in the vicinity of the infrared (IR) brane
corresponding to a strong deviation from conformality in the IR of the 4D
holographic dual. We compute the general low energy effective theory of the 5D
warped Standard Model, emphasizing additional IR contributions to the wave
function renormalization of the light Higgs mode. We also derive expressions
for the S and T parameters as a function of a generic 5D metric and zero-mode
wave functions. We give an approximate formula for the mass of the radion that
works even for strong deviation from the AdS background. We proceed to work out
the details of an explicit model and derive bounds for the first KK masses of
the various bulk fields. The radion is the lightest new particle although its
mass is already at about 1/3 of the mass of the lightest resonances, the KK
states of the gauge bosons. We examine carefully various issues that can arise
for extreme choices of parameters such as the possible reintroduction of the
hierarchy problem, the onset of nonperturbative physics due to strong IR
curvature or the creation of new hierarchies near the Planck scale. We conclude
that a KK scale of 1 TeV is compatible with all these constraints.Comment: 44 pages, 11 figures, references adde
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