4,842 research outputs found
News from the Virasoro algebra
It is shown that the local quantum field theory of the chiral energy-
momentum tensor with central charge coincides with the gauge invariant
subtheory of the chiral current algebra at level 1, where the gauge
group is the global symmetry. At higher level, the same scheme gives
rise to -algebra extensions of the Virasoro algebra.Comment: 4 pages, Latex, DESY 93-11
Feeling good about being hungry: food-related thoughts in eating disorder
Objectives: This study explores the relationships to food and hunger in women living with anorexic type eating difficulties and asks how imagery-based elaborations of food and eating thoughts are involved in their eating restraint, and recovery. Design: The qualitative idiographic approach of Interpretative Phenomenological Analysis (IPA) was used. Four in-depth semi-structured interviews were conducted with women self-selected as having experienced anorexia or anorexic like behaviour. Methods: The data was analysed using IPA and an audit of the analysis was conducted to ensure that the process followed had been systematic and rigorous and appropriately considered reflexivity. Results: Hunger was perceived positively by participants as confirmation that they were achieving their goal of losing weight, or avoiding weight gain. Hunger conferred a sense of being in control for the participants. Intrusive thoughts about food were reported as being quickly followed by elaborative mental imagery of the positive aspects of weight loss, and the negative consequences of eating. Imagery appeared to serve to maintain anorexic behaviours rather than to motivate food seeking. However, negative imagery of the consequences of anorexia were also described as supporting recovery. Conclusions: The finding that physiological sensations of hunger were experienced as positive confirmation of maintaining control has potentially important clinical and theoretical implications. It suggests further attention needs to be focused upon how changes in cognitive elaboration, involving mental imagery, are components of the psychological changes in the development of, maintenance of, and recovery from, anorexia
Segal-Bargmann-Fock modules of monogenic functions
In this paper we introduce the classical Segal-Bargmann transform starting
from the basis of Hermite polynomials and extend it to Clifford algebra-valued
functions. Then we apply the results to monogenic functions and prove that the
Segal-Bargmann kernel corresponds to the kernel of the Fourier-Borel transform
for monogenic functionals. This kernel is also the reproducing kernel for the
monogenic Bargmann module.Comment: 11 page
Birkhoff strata of the Grassmannian Gr: Algebraic curves
Algebraic varieties and curves arising in Birkhoff strata of the Sato
Grassmannian Gr are studied. It is shown that the big cell
contains the tower of families of the normal rational curves of all odd orders.
Strata , contain hyperelliptic curves of genus
and their coordinate rings. Strata , contain
plane curves for and and
curves in , respectively. Curves in the strata
have zero genus.Comment: 14 pages, no figures, improved some definitions, typos correcte
Full density matrix dynamics for large quantum systems: Interactions, Decoherence and Inelastic effects
We develop analytical tools and numerical methods for time evolving the total
density matrix of the finite-size Anderson model. The model is composed of two
finite metal grains, each prepared in canonical states of differing chemical
potential and connected through a single electronic level (quantum dot or
impurity). Coulomb interactions are either excluded all together, or allowed on
the dot only. We extend this basic model to emulate decoherring and inelastic
scattering processes for the dot electrons with the probe technique. Three
methods, originally developed to treat impurity dynamics, are augmented to
yield global system dynamics: the quantum Langevin equation method, the well
known fermionic trace formula, and an iterative path integral approach. The
latter accommodates interactions on the dot in a numerically exact fashion. We
apply the developed techniques to two open topics in nonequilibrium many-body
physics: (i) We explore the role of many-body electron-electron repulsion
effects on the dynamics of the system. Results, obtained using exact path
integral simulations, are compared to mean-field quantum Langevin equation
predictions. (ii) We analyze aspects of quantum equilibration and
thermalization in large quantum systems using the probe technique, mimicking
elastic-dephasing effects and inelastic interactions on the dot. Here, unitary
simulations based on the fermionic trace formula are accompanied by quantum
Langevin equation calculations
Minisuperspace Examples of Quantization Using Canonical Variables of the Ashtekar Type: Structure and Solutions
The Ashtekar variables have been use to find a number of exact solutions in
quantum gravity and quantum cosmology. We investigate the origin of these
solutions in the context of a number of canonical transformations (both complex
and real) of the basic Hamiltonian variables of general relativity. We are able
to present several new solutions in the minisuperspace (quantum cosmology)
sector. The meaning of these solutions is then discussed.Comment: 23 pages, latex, 3 figures (uuencoded, separate file
Towards a definition of quantum integrability
We briefly review the most relevant aspects of complete integrability for
classical systems and identify those aspects which should be present in a
definition of quantum integrability.
We show that a naive extension of classical concepts to the quantum framework
would not work because all infinite dimensional Hilbert spaces are unitarily
isomorphic and, as a consequence, it would not be easy to define degrees of
freedom. We argue that a geometrical formulation of quantum mechanics might
provide a way out.Comment: 37 pages, AmsLatex, 1 figur
Type I D-branes in an H-flux and twisted KO-theory
Witten has argued that charges of Type I D-branes in the presence of an
H-flux, take values in twisted KO-theory. We begin with the study of real
bundle gerbes and their holonomy. We then introduce the notion of real bundle
gerbe KO-theory which we establish is a geometric realization of twisted
KO-theory. We examine the relation with twisted K-theory, the Chern character
and provide some examples. We conclude with some open problems.Comment: 23 pages, Latex2e, 2 new references adde
Lipidomic profiling in Crohn's disease: abnormalities in phosphatidylinositols, with preservation of ceramide, phosphatidylcholine and phosphatidylserine composition.
Crohn's disease is a chronic inflammatory condition largely affecting the terminal ileum and large bowel. A contributing cause is the failure of an adequate acute inflammatory response as a result of impaired secretion of pro-inflammatory cytokines by macrophages. This defective secretion arises from aberrant vesicle trafficking, misdirecting the cytokines to lysosomal degradation. Aberrant intestinal permeability is also well-established in Crohn's disease. Both the disordered vesicle trafficking and increased bowel permeability could result from abnormal lipid composition. We thus measured the sphingo- and phospholipid composition of macrophages, using mass spectrometry and stable isotope labelling approaches. Stimulation of macrophages with heat-killed Escherichia coli resulted in three main changes; a significant reduction in the amount of individual ceramide species, an altered composition of phosphatidylcholine, and an increased rate of phosphatidylcholine synthesis in macrophages. These changes were observed in macrophages from both healthy control individuals and patients with Crohn's disease. The only difference detected between control and Crohn's disease macrophages was a reduced proportion of newly-synthesised phosphatidylinositol 16:0/18:1 over a defined time period. Shotgun lipidomics analysis of macroscopically non-inflamed ileal biopsies showed a significant decrease in this same lipid species with overall preservation of sphingolipid, phospholipid and cholesterol composition
Asymmetric Heat Flow in Mesoscopic Magnetic System
The characteristics of heat flow in a coupled magnetic system are studied.
The coupled system is composed of a gapped chain and a gapless chain. The
system size is assumed to be quite small so that the mean free path is
comparable to it. When the parameter set of the temperatures of reservoirs is
exchanged, the characteristics of heat flow are studied with the Keldysh Green
function technique. The asymmetry of current is found in the presence of a
local equilibrium process at the contact between the magnetic systems. The
present setup is realistic and such an effect will be observed in real
experiments. We also discuss the simple phenomenological explanation to obtain
the asymmetry.Comment: 13 pages, 3 figure
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