2,866 research outputs found
A microscopic model for Josephson currents
A microscopic model of a Josephson junction between two superconducting
plates is proposed and analysed. For this model, the nonequilibrium steady
state of the total system is explicitly constructed and its properties are
analysed. In particular, the Josephson current is rigorously computed as a
function of the phase difference of the two plates and the typical properties
of the Josephson current are recovered
Correlation Functions in the Two-dimensional Ising Model in a Magnetic Field at
The one and two-particle form factors of the energy operator in the
two-dimensional Ising model in a magnetic field at are exactly computed
within the form factor bootstrap approach. Together with the matrix elements of
the magnetisation operator already computed in ref.\,\cite{immf}, they are used
to write down the large distance expansion for the correlators of the two
relevant fields of the model.Comment: 18 pages, latex, 7 table
Topological aggregation, the twin paradox and the No Show paradox
International audienceConsider the framework of topological aggregation introduced by Chichilnisky (1980). We prove that in this framework the Twin Paradox and the No Show Paradox cannot be avoided. Anonymity and unanimity are not needed to obtain these results
Noncompact N=2 supergravity
A massive spin-one multiplet with central charge is coupled to N=2 supergravity. Compared to conventional gauge fields the anomalous magnetic moment of the spin-one particles is of the opposite sign. The construction of this theory is based on an N=2 supersymmetric gauge theory associated with the noncompact group SO(2,1). As a byproduct we present a convenient expression for the N=2 Einstein-Yang-Mills lagrangian.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24908/1/0000335.pd
La Politique Agricole Commune
La Politique Agricole Commune (PAC) est l’objet de ce numéro spécial de Regards économiques. Deux articles y sont consacrés. Le premier propose une analyse des effets économiques probables de la réforme récente de la PAC sur l’agriculture belge. Quant au second, il se demande comment rendre la PAC plus juste et plus efficace. La PAC : Une analyse de la réforme récente Les autorités régionales belges doivent se prononcer sur les différentes options de réforme de la PAC proposées par l'accord européen de juin dernier. Cet article examine les effets économiques probables de ces options sur l'agriculture belge à l'aide de deux modèles économiques complémentaires. Ce numéro donne aussi des pistes de réflexion sur quelques questions préoccupantes liées à cet accord et à l'évolution de la PAC. La PAC : Pour la rendre plus juste et plus efficace La PAC est examinée par le biais de trois questions. D’abord, quelles justifications normatives peut-on apporter à un subside de l’activité agricole pour elle même ? Ensuite, qui sont les bénéficiaires ultimes de la PAC dans ses versions passées et présente ? Enfin, peut-on reformuler une PAC dont les effets objectifs répondraient aux critères normatifs énoncés plus haut ?
Integrable field theory and critical phenomena. The Ising model in a magnetic field
The two-dimensional Ising model is the simplest model of statistical
mechanics exhibiting a second order phase transition. While in absence of
magnetic field it is known to be solvable on the lattice since Onsager's work
of the forties, exact results for the magnetic case have been missing until the
late eighties, when A.Zamolodchikov solved the model in a field at the critical
temperature, directly in the scaling limit, within the framework of integrable
quantum field theory. In this article we review this field theoretical approach
to the Ising universality class, with particular attention to the results
obtained starting from Zamolodchikov's scattering solution and to their
comparison with the numerical estimates on the lattice. The topics discussed
include scattering theory, form factors, correlation functions, universal
amplitude ratios and perturbations around integrable directions. Although we
restrict our discussion to the Ising model, the emphasis is on the general
methods of integrable quantum field theory which can be used in the study of
all universality classes of critical behaviour in two dimensions.Comment: 42 pages; invited review article for J. Phys.
Recommended from our members
Pancreatic Duct Glands Are Distinct Ductal Compartments That React to Chronic Injury and Mediate Shh-Induced Metaplasia
BACKGROUND & AIMS: Pancreatic intraepithelial neoplasia (PanIN) are pancreatic cancer precursor lesions of unclear origin and significance. PanIN aberrantly express sonic hedgehog (Shh), an initiator of pancreatic cancer, and gastrointestinal mucins. A majority of PanIN are thought to arise from ducts. We identified a novel ductal compartment that is gathered in gland-like outpouches (pancreatic duct glands [PDG]) of major ducts and characterized its role in injury and metaplasia. METHODS: The ductal system was analyzed in normal pancreata and chronic pancreatitis in humans and mice. Anatomy was assessed by serial hematoxylin and eosin sections and scanning electron microscopy of corrosion casts. Expression of mucins and developmental genes and proliferation were assessed by immunohistochemistry or real-time quantitative polymerase chain reaction. Effects of Shh on ductal cells were investigated by exposure to Shh in vitro and transgenic misexpression in vivo. RESULTS: Three-dimensional analysis revealed blind-ending outpouches of ducts in murine and human pancreata. These PDG are morphologically and molecularly distinct from normal ducts; even in normal pancreata they display PanIN and metaplastic features, such as expression of Shh and gastric mucins. They express other developmental genes, such as Pdx-1 and Hes-1. In injury, Shh is up-regulated along with gastric mucins. Expansion of the PDG compartment results in a mucinous metaplasia. Shh promotes this transformation in vitro and in vivo. CONCLUSIONS: PDG are distinct gland-like mucinous compartments with a distinct molecular signature. In response to injury, PDG undergo an Shh-mediated mucinous gastrointestinal metaplasia with PanIN-like features. PDG may provide a link between Shh, mucinous metaplasia, and neoplasia
Systematic Mutational Analysis of the Intracellular Regions of Yeast Gap1 Permease
The yeast general amino acid permease Gap1 is a convenient model for studying the intracellular trafficking of membrane proteins. Present at the plasma membrane when the nitrogen source is poor, it undergoes ubiquitin-dependent endocytosis and degradation upon addition of a good nitrogen source, e.g. ammonium. It comprises 12 transmembrane domains (TM) flanked by cytosol-facing N- and C-terminal tails (NT, CT). The NT of Gap1 contains the acceptor lysines for ubiquitylation and its CT includes a sequence essential to exit from the endoplasmic reticulum (ER).Journal ArticleResearch Support, Non-U.S. Gov'tSCOPUS: ar.jinfo:eu-repo/semantics/publishe
Scaling Limit of the Ising Model in a Field
The dilute A_3 model is a solvable IRF (interaction round a face) model with
three local states and adjacency conditions encoded by the Dynkin diagram of
the Lie algebra A_3. It can be regarded as a solvable version of an Ising model
at the critical temperature in a magnetic field. One therefore expects the
scaling limit to be governed by Zamolodchikov's integrable perturbation of the
c=1/2 conformal field theory. Indeed, a recent thermodynamic Bethe Ansatz
approach succeeded to unveil the corresponding E_8 structure under certain
assumptions on the nature of the Bethe Ansatz solutions. In order to check
these conjectures, we perform a detailed numerical investigation of the
solutions of the Bethe Ansatz equations for the critical and off-critical
model. Scaling functions for the ground-state corrections and for the lowest
spectral gaps are obtained, which give very precise numerical results for the
lowest mass ratios in the massive scaling limit. While these agree perfectly
with the E_8 mass ratios, we observe one state which seems to violate the
assumptions underlying the thermodynamic Bethe Ansatz calculation. We also
analyze the critical spectrum of the dilute A_3 model, which exhibits massive
excitations on top of the massless states of the Ising conformal field theory.Comment: 29 pages, RevTeX, 11 PostScript figures included by epsf, using
amssymb.sty (v2.2
- …