A2 Toda theory in reduced WZNW framework and the representations of the W algebra

Using the reduced WZNW formulation we analyse the classical $W$ orbit content of the space of classical solutions of the $A_2$ Toda theory. We define the quantized Toda field as a periodic primary field of the $W$ algebra satisfying the quantized equations of motion. We show that this local operator can be constructed consistently only in a Hilbert space consisting of the representations corresponding to the minimal models of the $W$ algebra.Comment: 38 page

Diffraction in the semiclassical description of mesoscopic devices

In pseudo integrable systems diffractive scattering caused by wedges and impurities can be described within the framework of Geometric Theory of Diffraction (GDT) in a way similar to the one used in the Periodic Orbit Theory of Diffraction (POTD). We derive formulas expressing the reflection and transition matrix elements for one and many diffractive points and apply it for impurity and wedge diffraction. Diffraction can cause backscattering in situations, where usual semiclassical backscattering is absent causing an erodation of ideal conductance steps. The length of diffractive periodic orbits and diffractive loops can be detected in the power spectrum of the reflection matrix elements. The tail of the power spectrum shows $\sim 1/l^{1/2}$ decay due to impurity scattering and $\sim 1/l^{3/2}$ decay due to wedge scattering. We think this is a universal sign of the presence of diffractive scattering in pseudo integrable waveguides.Comment: 18 pages, Latex , ep

SUSY sine-Gordon theory as a perturbed conformal field theory and finite size effects

We consider SUSY sine-Gordon theory in the framework of perturbed conformal field theory. Using an argument from Zamolodchikov, we obtain the vacuum structure and the kink adjacency diagram of the theory, which is cross-checked against the exact S-matrix prediction, first-order perturbed conformal field theory (PCFT), the NLIE method and truncated conformal space approach. We provide evidence for consistency between the usual Lagrangian description and PCFT on the one hand, and between PCFT, NLIE and a massgap formula conjectured by Baseilhac and Fateev, on the other. In addition, we extend the NLIE description to all the vacua of the theory. (C) 2003 Elsevier B.V. All rights reserved

Multifractal Network Generator

We introduce a new approach to constructing networks with realistic features. Our method, in spite of its conceptual simplicity (it has only two parameters) is capable of generating a wide variety of network types with prescribed statistical properties, e.g., with degree- or clustering coefficient distributions of various, very different forms. In turn, these graphs can be used to test hypotheses, or, as models of actual data. The method is based on a mapping between suitably chosen singular measures defined on the unit square and sparse infinite networks. Such a mapping has the great potential of allowing for graph theoretical results for a variety of network topologies. The main idea of our approach is to go to the infinite limit of the singular measure and the size of the corresponding graph simultaneously. A very unique feature of this construction is that the complexity of the generated network is increasing with the size. We present analytic expressions derived from the parameters of the -- to be iterated-- initial generating measure for such major characteristics of graphs as their degree, clustering coefficient and assortativity coefficient distributions. The optimal parameters of the generating measure are determined from a simple simulated annealing process. Thus, the present work provides a tool for researchers from a variety of fields (such as biology, computer science, biology, or complex systems) enabling them to create a versatile model of their network data.Comment: Preprint. Final version appeared in PNAS

Study of BsB_{s} oscillations

This document contains two ALEPH Reports on three different analyses of $B_{s}$ oscillations, based on the statistics collected by the ALEPH experiment during 1991-1995. $B_{s}$ mesons are fully reconstructed in several hadronic decay channels, yielding a small sample of candidates with excellent decay length and momentum reconstruction. Semileptonic decays with a fully recontructed $D_{s}$ meson yield larger statistics with equally high $B_{s}$ purity, but somewhat degraded momentum resolution. Inclusive semileptonic decays of b hadrons yield the highest sensitivity to $B_{s}$ oscillations, due to the much higher statistics. The combination of the above three with the other ALEPH analyses gives a limit of $\Delta m_{s} > 10.7$ ps$^{-1}$ at 95% C.L. with a sensitivity equal to $13.1$ ps$^{-1}$

Kepler observations of A-F pre-main sequence stars in Upper Scorpius: Discovery of six new δ\delta~Scuti and one γ\gamma~Doradus stars

We present light curves and periodograms for 27 stars in the young Upper Scorpius association (age=$11 \pm 1$\,Myr) obtained with the Kepler spacecraft. This association is only the second stellar grouping to host several pulsating pre-main sequence (PMS) stars which have been observed from space. From an analysis of the periodograms, we identify six $\delta$~Scuti variables and one $\gamma$~Doradus star. These are most likely PMS stars or else very close to the zero-age main sequence. Four of the $\delta$~Scuti variables were observed in short-cadence mode, which allows us to resolve the entire frequency spectrum. For these four stars, we are able to infer some qualitative information concerning their ages. For the remaining two $\delta$~Scuti stars, only long-cadence data are available, which means that some of the frequencies are likely to be aliases. One of the stars appears to be a rotational variable in a hierarchical triple system. This is a particularly important object, as it allows the possibility of an accurate mass determination when radial velocity observations become available. We also report on new high-resolution echelle spectra obtained for some of the stars of our sample.Comment: 19 pages, 9 figures. Accepted for publication on MNRA

Track Momentum Discrimination Using Cluster Width in Silicon Strip Sensors for SLHC

The cluster width of a particle crossing a silicon strip (mini strip) detector can be exploited to measure its transverse momentum when the strips are parallel to the B field. This suggests the discrimination of the clusters widths to filter the majority of low momentum particles. Once performed directly on the detectors, such discrimination can be used both for low level trigger (L1) and for data reduction. This approach is discussed in the context of a first level trigger based on the Tracker for SLHC. The quality of the measurements and their discrimination capability are discussed with respect to the geometry of the sensors and to the detectors layout. Electronics issues and constraints are also reviewed

An Introduction to Community Detection in Multi-layered Social Network

Social communities extraction and their dynamics are one of the most important problems in today's social network analysis. During last few years, many researchers have proposed their own methods for group discovery in social networks. However, almost none of them have noticed that modern social networks are much more complex than few years ago. Due to vast amount of different data about various user activities available in IT systems, it is possible to distinguish the new class of social networks called multi-layered social network. For that reason, the new approach to community detection in the multi-layered social network, which utilizes multi-layered edge clustering coefficient is proposed in the paper.Comment: M.D. Lytras et al. (Eds.): WSKS 2011, CCIS 278, pp. 185-190, 201

Pre-main sequence stars with disks in the Eagle Nebula observed in scattered light

NGC6611 and its parental cloud, the Eagle Nebula (M16), are well-studied star-forming regions, thanks to their large content of both OB stars and stars with disks and the observed ongoing star formation. We identified 834 disk-bearing stars associated with the cloud, after detecting their excesses in NIR bands from J band to 8.0 micron. In this paper, we study in detail the nature of a subsample of disk-bearing stars that show peculiar characteristics. They appear older than the other members in the V vs. V-I diagram, and/or they have one or more IRAC colors at pure photospheric values, despite showing NIR excesses, when optical and infrared colors are compared. We confirm the membership of these stars to M16 by a spectroscopic analysis. The physical properties of these stars with disks are studied by comparing their spectral energy distributions (SEDs) with the SEDs predicted by models of T-Tauri stars with disks and envelopes. We show that the age of these stars estimated from the V vs. V-I diagram is unreliable since their V-I colors are altered by the light scattered by the disk into the line of sight. Only in a few cases their SEDs are compatible with models with excesses in V band caused by optical veiling. Candidate members with disks and photospheric IRAC colors are selected by the used NIR disk diagnostic, which is sensitive to moderate excesses, such as those produced by disks with low masses. In 1/3 of these cases, scattering of stellar flux by the disks can also be invoked. The photospheric light scattered by the disk grains into the line of sight can affect the derivation of physical parameters of ClassII stars from photometric optical and NIR data. Besides, the disks diagnostic we defined are useful for selecting stars with disks, even those with moderate excesses or whose optical colors are altered by veiling or photospheric scattered light.Comment: Accepted for publication in A&

Bacteria consortia and deterioration of archaeological waterlogged wood: identification by molecular and microscopy techniques

In this study molecular tools are applied to reveal and identify bacterial colonization in waterlogged wood to assessing the changes induced in anatomical structure, previously observed by Optical and Scanning Electron Microscopy (1). The results obtained by observation of wooden thin sections (OM), shown the presence of black and dark-brown areas and mineral concretions. The SEM analysis revealed a specific cell walls alteration, attributable to bacterial activity, other than abundant pyrite framboids (FeS2). The presence of sulfur compounds in archaeological waterlogged wood can indicate both long-term burial in anoxic environment and colonization by sulfate-reducing bacteria. Molecular methods allow us extract microbial genomic DNA from wood samples and in vitro amplify (PCR) bacteria DNA target sequences (16S, ITS-rRNA) (2). Through sequences analysis of PCR products cellulosolytic and ligninolytic bacteria, such as Pseudomonas, Cellulomonas, Xanthomonas and Bacillus spp, have been revealed. Moreover the presence of Marinobacter sp. and Desulforudis audaxviator, respectively iron-oxidizing and sulfate-reducing bacteria, are identify. We hypothesize that this investigation approach, can be applied to a variety of wooden artifacts of archaeological findings for both characterization of microbial colonization in order to understanding the main degradation phenomena, indispensable for a correct conservation strategies. (1) Safa A. et al. (2012) Using SEM in monitoring changes in archaeological wood: A review. Current Microscopy Contributions to Advances in Science and Technology (A. Méndez-Vilas, Ed.) (2) Palla, F., (2012) Analytical techniques: analysis of microbial colonization. In Science and Conservation in Museum Collections, B. Fabbri (ed), Nardini, Firenze. 14, 459-470