2,578 research outputs found
Analysis of enhanced tan(beta) corrections in MFV GUT scenarios
We analyse a minimal supersymmetric standard model (MSSM) taking a minimal
flavour violation (MFV) structure at the GUT scale. We evaluate the parameters
at the electroweak scale taking into account the full flavour structure in the
evolution of the renormalization group equations. We concentrate mainly on the
decay Bs -> mu mu and its correlations with other observables like b -> s
gamma, b -> s l l, Delta M_Bs and the anomalous magnetic moment of the muon. We
restrict our analysis to the regions in parameter space consistent with the
dark matter constraints. We find that the BR(Bs -> mu mu) can exceed the
current experimental limit in the regions of parameter space which are allowed
by all other constraints thus providing an additional bound on supersymmetric
parameters. This holds even in the constrained MSSM. Assuming an hypothetical
measurement of BR(Bs -> mu mu) ~ 10^-7 we analyse the predicted MSSM spectrum
and flavour violating decay modes of supersymmetric particles which are found
to be small.Comment: 47 pages, 16 figures (best viewed printed or in pdf format), updated
lattice inputs used, version submitted to PR
Disordered Mott insulators in strong electric fields
We characterize the current-carrying nonequilibrium steady-state in a
single-band Hubbard model confronted with a static electric field in the
presence of quenched disorder. As disorder is not expected to dissipate the
extra energy injected by the field, optical phonons assisted by a fermionic
heat bath serve as dissipation channels for the current-induced Joule heat
generated by the accelerated electrons. In a purely electronic setup, the
disorder-induced dephasing cannot contribute states within the gap but only
smear out the edges of the Hubbard bands. When phonons are taken into account,
the different nature of disorder-induced dephasing and phonon-related
dissipation becomes clear. We show that although both disorder and
electron-phonon interaction enhance the current at off-resonant fields,
disorder effects play a marginal role since they cannot provide in-gap states
which are instead brought about by phonons and represent the privileged
relaxation pathway for excited electrons.Comment: 15 pages, 17 figures, comments are welcom
Correlated band structure and the ground-state phase diagram in high-Tc cuprates
We review results obtained with a recently proposed variational cluster
approach (VCA) for the competition between d-wave superconductivity (dSC) and
antiferromagnetism (AF) in the high-Tc cuprates. Comparing the single-particle
spectra of a two-dimensional Hubbard model with quantum Monte-Carlo (QMC) and
experimental data, we verify that the VCA correctly treats the low-energy
excitations. The cluster calculations reproduce the overall ground-state phase
diagram of the high-temperature superconductors both for electron- and
hole-doping. In particular, they include salient features such as the enhanced
robustness of the AF state in case of electron doping. For electron- but also
for hole-doping, we clearly identify a tendency to phase separation into a
mixed AF-dSC phase at low and a pure dSC-phase at high doping.Comment: 4 pages, 3 figures, submitted to the SCES'0
Correlated Mott insulators in a strong electric field: The effects of phonon renormalization
We characterize the response of a Mott insulating system to a static electric
field in terms of its conducting and spectral properties. Dissipation is
included by a coupling to fermionic baths and to either optical or acoustic
phonons. This paper extends and completes the analysis made in a previous work
by the authors [arXiv:2207.01921]. In the present work phonons are included
diagrammatically within the Migdal approximation by also including
self-consistency from the electronic feedback. The nonequilibrium steady-state
is addressed by means of the dynamical mean-field theory based on the
nonequilibrium Green's function approach, while the so-called auxiliary master
equation approach is employed as impurity solver. With optical phonons the
self-consistency suppresses the steady-state current at the onset of the
metallic phase with respect to the nonself-consistent case. This is due to the
interaction of phonons with the hot electrons of the lattice which increases
their temperature, thus providing a less effective relaxation channel for the
current-induced Joule heat. In addition, in the case of optical phonons the
results are essentially independent of the temperature of the fermionic baths,
as the latter is sensibly smaller than their characteristic frequency. On the
other hand, with acoustic phonons the steady-state current is slightly
suppressed by the self-consistent treatment only at field strengths close to
half of the gap, away from the metallic phase, and especially at very small
phonon frequency. Also, in this case the results seem to slightly depend on the
temperature of the fermionic baths.Comment: 14 pages, 19 figures, comments are welcom
Characterization of the translocon of the outer envelope of chloroplasts
The protein translocon of the outer envelope of chloroplasts (Toc) consists of the core subunits Toc159, Toc75, and Toc34. To investigate the molecular structure, the core complex was purified. This core complex has an apparent molecular mass of ∼500 kD and a molecular stoichiometry of 1:4:4–5 between Toc159, Toc75, and Toc34. The isolated translocon recognizes both transit sequences and precursor proteins in a GTP-dependent manner, suggesting its functional integrity. The complex is embedded by the lipids phosphatidylcholine and digalactosyldiacylglyceride. Two-dimensional structural analysis by EM revealed roughly circular particles consistent with the formation of a stable core complex. The particles show a diameter of ∼130 Å with a solid ring and a less dense interior structure. A three-dimensional map obtained by random conical tilt reconstruction of electron micrographs suggests that a “finger”-like central region separates four curved translocation channels within one complex
Novel bi-allelic variants expand the SPTBN4-related genetic and phenotypic spectrum
Neurodevelopmental disorder with hypotonia, neuropathy, and deafness (NEDHND, OMIM #617519) is an autosomal recessive disease caused by homozygous or compound heterozygous variants in SPTBN4 coding for type 4 beta IV-spectrin, a non-erythrocytic member of the beta-spectrin family. Variants in SPTBN4 disrupt the cytoskeletal machinery that controls proper localization of ion channels and the function of axonal domains, thereby generating severe neurological dysfunction. We set out to analyze the genetic causes and describe the clinical spectrum of suspected cases of NEDHND. Variant screening was done by whole exome sequencing; clinical phenotypes were described according to the human phenotype ontology, and histochemical analysis was performed with disease-specific antibodies. We report four families with five patients harboring novel homozygous and compound heterozygous SPTBN4 variants, amongst them a multi-exon deletion of SPTBN4. All patients presented with the key features of NEDHND; severe muscular hypotonia, dysphagia, absent speech, gross motor, and mental retardation. Additional symptoms comprised horizontal nystagmus, epileptiform discharges in EEG without manifest seizures, and choreoathetosis. Muscle histology revealed both characteristics of myopathy and of neuropathy. This report expands the SPTBN4 variant spectrum, highlights the spectrum of morphological phenotypes of NEDHND-patients, and reveals clinical similarities between the NEDHND, non-5q SMA, and congenital myopathies
Various quantum nonlocality tests with a simple 2-photon entanglement source
Nonlocality is a fascinating and counterintuitive aspect of Nature, revealed
by the violation of a Bell inequality. The standard and easiest configuration
in which Bell inequalities can be measured has been proposed by
Clauser-Horne-Shimony-Holt (CHSH). However, alternative nonlocality tests can
also be carried out. In particular, Bell inequalities requiring multiple
measurement settings can provide deeper fundamental insights about quantum
nonlocality as well as offering advantages in the presence of noise and
detection inefficiency. In this article we show how these nonlocality tests can
be performed using a commercially available source of entangled photon pairs.
We report the violation of a series of these nonlocality tests (I3322, I4422
and chained inequalities). With the violation of the chained inequality with 4
settings per side we put an upper limit at 0.49 on the local content of the
states prepared by the source (instead of 0.63 attainable with CHSH). We also
quantify the amount of true randomness that has been created during our
experiment (assuming fair sampling of the detected events).Comment: 8 pages, 5 figure
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