11,682 research outputs found
Tensor Product and Permutation Branes on the Torus
We consider B-type D-branes in the Gepner model consisting of two minimal
models at k=2. This Gepner model is mirror to a torus theory. We establish the
dictionary identifying the B-type D-branes of the Gepner model with A-type
Neumann and Dirichlet branes on the torus.Comment: 26 page
Permutation branes and linear matrix factorisations
All the known rational boundary states for Gepner models can be regarded as
permutation branes. On general grounds, one expects that topological branes in
Gepner models can be encoded as matrix factorisations of the corresponding
Landau-Ginzburg potentials. In this paper we identify the matrix factorisations
associated to arbitrary B-type permutation branes.Comment: 43 pages. v2: References adde
Does autonomic function link social position to coronary risk? The Whitehall II study.
BACKGROUND: Laboratory and clinical studies suggest that the autonomic nervous system responds to chronic behavioral and psychosocial stressors with adverse metabolic consequences and that this may explain the relation between low social position and high coronary risk. We sought to test this hypothesis in a healthy occupational cohort. METHODS AND RESULTS: This study comprised 2197 male civil servants 45 to 68 years of age in the Whitehall II study who were undergoing standardized assessments of social position (employment grade) and the psychosocial, behavioral, and metabolic risk factors for coronary disease previously found to be associated with low social position. Five-minute recordings of heart rate variability (HRV) were used to assess cardiac parasympathetic function (SD of N-N intervals and high-frequency power [0.15 to 0.40 Hz]) and the influence of sympathetic and parasympathetic function (low-frequency power [0.04 to 0.15 Hz]). Low employment grade was associated with low HRV (age-adjusted trend for each modality, P< or =0.02). Adverse behavioral factors (smoking, exercise, alcohol, and diet) and psychosocial factors (job control) showed age-adjusted associations with low HRV (P<0.03). The age-adjusted mean low-frequency power was 319 ms2 among those participants in the bottom tertile of job control compared with 379 ms2 in the other participants (P=0.004). HRV showed strong (P<0.001) linear associations with components of the metabolic syndrome (waist circumference, systolic blood pressure, HDL cholesterol, triglycerides, and fasting and 2-hour postload glucose). The social gradient in prevalence of metabolic syndrome was explained statistically by adjustment for low-frequency power, behavioral factors, and job control. CONCLUSIONS: Chronically impaired autonomic function may link social position to different components of coronary risk in the general population
Orientifolds of Gepner Models
We systematically construct and study Type II Orientifolds based on Gepner
models which have N=1 supersymmetry in 3+1 dimensions. We classify the parity
symmetries and construct the crosscap states. We write down the conditions that
a configuration of rational branes must satisfy for consistency (tadpole
cancellation and rank constraints) and spacetime supersymmetry. For certain
cases, including Type IIB orientifolds of the quintic and a two parameter
model, one can find all solutions in this class. Depending on the parity, the
number of vacua can be large, of the order of 10^{10}-10^{13}. For other
models, it is hard to find all solutions but special solutions can be found --
some of them are chiral. We also make comparison with the large volume regime
and obtain a perfect match. Through this study, we find a number of new
features of Type II orientifolds, including the structure of moduli space and
the change in the type of O-planes under navigation through non-geometric
phases.Comment: 142 page
Comparison between mirror Langmuir probe and gas puff imaging measurements of intermittent fluctuations in the Alcator C-Mod scrape-off layer
Statistical properties of the scrape-off layer (SOL) plasma fluctuations are
studied in ohmically heated plasmas in the Alcator C-Mod tokamak. For the first
time, plasma fluctuations as well as parameters that describe the fluctuations
are compared across measurements from a mirror Langmuir probe (MLP) and from
gas-puff imaging (GPI) that sample the same plasma discharge. This comparison
is complemented by an analysis of line emission time-series data, synthesized
from the MLP electron density and temperature measurements. The fluctuations
observed by the MLP and GPI typically display relative fluctuation amplitudes
of order unity together with positively skewed and flattened probability
density functions. Such data time series are well described by an established
stochastic framework which model the data as a superposition of uncorrelated,
two-sided exponential pulses. The most important parameter of the process is
the intermittency parameter, {\gamma} = {\tau}d / {\tau}w where {\tau}d denotes
the duration time of a single pulse and {\tau}w gives the average waiting time
between consecutive pulses. Here we show, using a new deconvolution method,
that these parameters can be consistently estimated from different statistics
of the data. We also show that the statistical properties of the data sampled
by the MLP and GPI diagnostic are very similar. Finally, a comparison of the
GPI signal to the synthetic line-emission time series suggests that the
measured emission intensity can not be explained solely by a simplified model
which neglects neutral particle dynamics
Opening Mirror Symmetry on the Quintic
Aided by mirror symmetry, we determine the number of holomorphic disks ending
on the real Lagrangian in the quintic threefold. The tension of the domainwall
between the two vacua on the brane, which is the generating function for the
open Gromov-Witten invariants, satisfies a certain extension of the
Picard-Fuchs differential equation governing periods of the mirror quintic. We
verify consistency of the monodromies under analytic continuation of the
superpotential over the entire moduli space. We reproduce the first few
instanton numbers by a localization computation directly in the A-model, and
check Ooguri-Vafa integrality. This is the first exact result on open string
mirror symmetry for a compact Calabi-Yau manifold.Comment: 26 pages. v2: minor corrections and improvement
Matrix Factorizations, Minimal Models and Massey Products
We present a method to compute the full non-linear deformations of matrix
factorizations for ADE minimal models. This method is based on the calculation
of higher products in the cohomology, called Massey products. The algorithm
yields a polynomial ring whose vanishing relations encode the obstructions of
the deformations of the D-branes characterized by these matrix factorizations.
This coincides with the critical locus of the effective superpotential which
can be computed by integrating these relations. Our results for the effective
superpotential are in agreement with those obtained from solving the A-infinity
relations. We point out a relation to the superpotentials of Kazama-Suzuki
models. We will illustrate our findings by various examples, putting emphasis
on the E_6 minimal model.Comment: 32 pages, v2: typos corrected, v3: additional comments concerning the
bulk-boundary crossing constraint, some small clarifications, typo
Defect Perturbations in Landau-Ginzburg Models
Perturbations of B-type defects in Landau-Ginzburg models are considered. In
particular, the effect of perturbations of defects on their fusion is analyzed
in the framework of matrix factorizations. As an application, it is discussed
how fusion with perturbed defects induces perturbations on boundary conditions.
It is shown that in some classes of models all boundary perturbations can be
obtained in this way. Moreover, a universal class of perturbed defects is
constructed, whose fusion under certain conditions obey braid relations. The
functors obtained by fusing these defects with boundary conditions are twist
functors as introduced in the work of Seidel and Thomas.Comment: 46 page
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