Finite nilpotent semigroups of small coclass

The parameter coclass has been used successfully in the study of nilpotent algebraic objects of different kinds. In this paper a definition of coclass for nilpotent semigroups is introduced and semigroups of coclass 0, 1, and 2 are classified. Presentations for all such semigroups and formulae for their numbers are obtained. The classification is provided up to isomorphism as well as up to isomorphism or anti-isomorphism. Commutative and self-dual semigroups are identified within the classification.Comment: 11 page

World-sheet Stability of (0,2) Linear Sigma Models

We argue that two-dimensional (0,2) gauged linear sigma models are not destabilized by instanton generated world-sheet superpotentials. We construct several examples where we show this to be true. The general proof is based on the Konishi anomaly for (0,2) theories.Comment: 18 pages, LaTe

Evidenzbasierte Therapie des Raynaud-Syndroms

Zusammenfassung: Das Raynaud-Syndrom ist mit einer Prävalenz von 3-5% ein häufiges klinisches Problem. Dennoch ist die Wirkung der meisten Therapiemöglichkeiten nur unzureichend durch kontrollierte Studien belegt. Zu den Therapien mit höherem Evidenzgrad gehört der Kalziumantagonist Nifedipin, für den in Metaanalysen sowohl bei primärem als auch bei sekundärem Raynaud-Syndrom eine verbesserte periphere Durchblutung sowie eine Abnahme der Frequenz und des Schweregrades der Raynaud-Attacken nachgewiesen werden konnte. Ähnliches gilt für intravenös appliziertes Iloprost in der Therapie des sekundären Raynaud-Syndroms bei systemischer Sklerose. Intravenös verabreichtes Iloprost verbessert darüber hinaus das Abheilen von Fingerkuppenulzera bei Patienten mit systemischer Sklerose. Vielversprechende Therapieansätze stellen Angiotensin-II-Rezeptor-1-Antagonisten (Losartan), die Kalziumantagonisten Felodipin und Amlodipin, Serotonin-Reuptake-Hemmer (Fluoxetin) und Phosphodiesterase-V-Hemmer (Sildenafil, Vardenafil) dar, die sich in kontrollierten Einzelstudien als wirksam erwiesen haben. Jedoch fehlen Erfahrungen mit größeren Patientenzahlen und längeren Anwendungszeiten, um diese Therapiemöglichkeiten abschließend zu beurteile

Deformed Quantum Cohomology and (0,2) Mirror Symmetry

We compute instanton corrections to correlators in the genus-zero topological subsector of a (0,2) supersymmetric gauged linear sigma model with target space P1xP1, whose left-moving fermions couple to a deformation of the tangent bundle. We then deduce the theory's chiral ring from these correlators, which reduces in the limit of zero deformation to the (2,2) ring. Finally, we compare our results with the computations carried out by Adams et al.[ABS04] and Katz and Sharpe[KS06]. We find immediate agreement with the latter and an interesting puzzle in completely matching the chiral ring of the former.Comment: AMSLatex, 30 pages, one eps figure. V4: typos corrected, final version appearing in JHE

Monocyte chemoattractant proteins in the pathogenesis of systemic sclerosis

Activation of the immune system and increased synthesis of extracellular matrix proteins by fibroblasts are hallmarks in the pathogenesis of SSc. The molecular mechanisms underlying the infiltration of inflammatory cells into the skin and the subsequent activation of fibroblasts are still largely unknown. Chemokines are a family of small molecules that are classified according to the position of the NH2-terminal cysteine motif. Recent data indicate that chemokines and in particular two members of the subfamily of monocyte chemoattractant proteins, MCP-1 (CCL-2) and MCP-3 (CCL-7), might be involved in the pathogenesis of SSc. MCP-1 and -3 are overexpressed by SSc fibroblasts and in skin lesions from SSc patients compared to healthy controls. MCP-1 and -3 are chemotactic for inflammatory cells and stimulate their migration into the skin. In addition to their pro-inflammatory effects, MCP-1 and -3 contribute to tissue fibrosis by activating the synthesis of extracellular matrix proteins in SSc fibroblasts. Therapeutic strategies targeting MCP-1 have revealed promising results in several animal models of SSc. Antagonists against the receptor CCR2 are currently tested in clinical trials of a variety of diseases and also represent interesting candidates for target-directed therapy in SS

An N=2 gauge theory and its supergravity dual

We study flows on the scalar manifold of N=8 gauged supergravity in five dimensions which are dual to certain mass deformations of N=4 super Yang--Mills theory. In particular, we consider a perturbation of the gauge theory by a mass term for the adjoint hyper-multiplet, giving rise to an N=2 theory. The exact solution of the 5-dim gauged supergravity equations of motion is found and the metric is uplifted to a ten-dimensional background of type-IIB supergravity. Using these geometric data and the AdS/CFT correspondence we analyze the spectra of certain operators as well as Wilson loops on the dual gauge theory side. The physical flows are parametrized by a single non-positive constant and describe part of the Coulomb branch of the N=2 theory at strong coupling. We also propose a general criterion to distinguish between `physical' and `unphysical' curvature singularities. Applying it in many backgrounds arising within the AdS/CFT correspondence we find results that are in complete agreement with field theory expectations.Comment: 16 pages, latex2e, 1 figure. v2: minor modifications, version to appear in PL

Frontiers of antifibrotic therapy in systemic sclerosis

Although fibrosis is becoming increasingly recognized as a major cause of morbidity and mortality in modern societies, targeted anti-fibrotic therapies are still not approved for most fibrotic disorders. However, intense research over the last decade has improved our understanding of the underlying pathogenesis of fibrotic diseases. We now appreciate fibrosis as the consequence of a persistent tissue repair responses, which, in contrast to normal wound healing, fails to be effectively terminated. Profibrotic mediators released from infiltrating leukocytes, activated endothelial cells and degranulated platelets may predominantly drive fibroblast activation and collagen release in early stages, whereas endogenous activation of fibroblasts due epigenetic modifications and biomechanical or physical factors such as stiffening of the extracellular matrix and hypoxia may play pivotal role for disease progression in later stages. In the present review, we discuss novel insights into the pathogenesis of fibrotic diseases using systemic sclerosis (SSc) as example for an idiopathic, multisystem disorder. We set a strong translational focus and predominantly discuss approaches with very high potential for rapid transfer from bench-to-bedside. We highlight the molecular basis for ongoing clinical trials in SSc and also provide an outlook on upcoming trials. This article is protected by copyright. All rights reserved

F-theory and linear sigma models

We present an explicit method for translating between the linear sigma model and the spectral cover description of SU(r) stable bundles over an elliptically fibered Calabi-Yau manifold. We use this to investigate the 4-dimensional duality between (0,2) heterotic and F-theory compactifications. We indirectly find that much interesting heterotic information must be contained in the `spectral bundle' and in its dual description as a gauge theory on multiple F-theory 7-branes. A by-product of these efforts is a method for analyzing semistability and the splitting type of vector bundles over an elliptic curve given as the sheaf cohomology of a monad.Comment: 40 pages, no figures; minor cosmetic reorganization of section 4; reference [6] update

Interpreting the M2-brane Action

The world-volume theory of multiple M2-branes proposed recently has a free scalar field. For large vev of this scalar field the world-volume action reduces to that of multiple D2-branes with Yang-Mills coupling proportional to the vev. We suggest that the correct interpretation of this scalar field is as the radial position of the M2-brane center of mass in a cylindrical polar coordinate system. Regarding the azimuthal angle as compact we can regard this as a set of coincident D2-branes in type IIA string theory with varying dilaton and metric. We find that the effective world-volume theory on the D2-branes has Yang-Mills coupling proportional to the radial coordinate; furthermore the radial coordinate satisfies free field equations of motion. This agrees with the corresponding results derived from the M2-brane world-volume theory.Comment: LaTeX file, 6 page