1435 research outputs found
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Non-Abelian Vortices in SO(N) and USp(N) Gauge Theories
No full textNon-Abelian BPS vortices in SO(N) x U(1) and USp(2N) x U(1) gauge theories
are constructed in maximally color-flavor locked vacua. We study in detail
their moduli and transformation properties under the exact symmetry of the
system. Our results generalize non-trivially those found earlier in
supersymmetric U(N) gauge theories. The structure of the moduli spaces turns
out in fact to be considerably richer here than what was found in the U(N)
theories. We find that vortices are generally of the semi-local type, with
power-like tails of profile functions
What a top-down linguistic analysis can tell about genomic sequences
No full textThis paper presents a bottom up strategy to detect features in genomic sequences
Adaptive Service Selection - A Fuzzy-valued Matchmaking Approach
No full textService composition concerns both integration of heterogeneous distributed applications and dynamic selection of services. QoS-aware selection enables a service requester with certain QoS requirements to classify services according to their QoS guarantees. In this paper we present a method that allows for a fuzzy-valued description of QoS parameters. Fuzzy sets are suited to specify both the QoS preferences raised by a service requester such as `response time must be as lower as possible and cannot be more that 1000ms' and approximate estimates a provider can make on the QoS capabilities of its services like `availability is roughly between 95% and 99%'. We propose a matchmaking procedure based on a fuzzy-valued similarity measure that, given the specifications of QoS parameters of the requester and the providers, selects the most appropriate service among several functionally-equivalent ones, using a fuzzy ordering relation. We also devise a method for dynamical update of service offers by means of runtime monitoring of the actual QoS performance
Controllo delle superfici di prodotti in pietra naturale. Atti del Dipartimento di Ingegneria Meccanica, Nucleare e della Produzione dell'Università di Pisa.
No full textRIASSUNTO Analisi con metodi ottici di superfici lucidate. Caratterizzazione delle superfici con diverse metodologie. Incisione di codici su materiali lapidei. SUMMARY Polished surfaces analysis with optical methods. Characterization of surface with different methodologies. Marking of codes on stones materials
Database, WebGIS, storia ed archeologia: riflessioni metodologiche dietro un progetto sulla Lunigiana medievale
No full textRIASSUNTO La relazione presenta il work in progress di un gruppo di ricerca formatosi di recente e composto da docenti, ricercatori e laureandi dell’Università di Pisa e del CNR. L’équipe ha come scopo la creazione di un WebGIS sulla Bassa Lunigiana medievale che possa risultare utile a diverse tipologie di utenti: l’amministratore, il turista e il singolo cittadino, il ricercatore. In particolare riguardo all’ultima tipologia di utente si è pensato a un sistema di informazione geografica che contenga dati sia storici che archeologici, in modo da ottenere nuove capacità di analisi fondate sull’incrocio di informazioni provenienti da ricerche diverse. L’elaborazione di tale prodotto ha messo in luce le difficoltà più acute che sorgono quando si cerca di porre in relazione in maniera automatizzata dati storici e archeologici al fine di conoscere il popolamento e l’insediamento di un territorio nel tempo. SUMMARY This paper presents the work in progress to create a WebGIS about Medioeval Bassa Lunigiana. The WebGIS can be useful by administrator, tourist, citizen and university researcher
A mortalin-like gene is crucial for planarian stem cell viability
No full textSUMMARY - In adult organisms, stem cells are crucial to homeostasis and regeneration of damaged tissues. In planarians, adult stem cells (neoblasts) are endowed with an extraordinary replicative potential that guarantees unlimited replacement of all differentiated cell types and extraordinary regenerative ability. The molecular mechanisms by which neoblasts combine long-term stability and constant proliferative activity, overcoming the impact of time, remain by far unknown. Here we investigate the role of Djmot, a planarian orthologue that encodes a peculiar member of the HSP70 family, named Mortalin, on the dynamics of stem cells of Dugesia japonica. Planarian stem cells and progenitors constitutively express Djmot. Transient Djmot expression in differentiated tissues is only observed after X-ray irradiation. DjmotRNA interference causes inability to regenerate and death of the animals, as a result of permanent growth arrest of stem cells. These results provide the first evidence that an hsp-related gene is essential for neoblast viability and suggest the possibility that high levels of Djmot serve to keep a p53-like protein signaling under control, thus allowing neoblasts to escape cell death programs. Further studies are needed to unravel the molecular pathways involved in these processes
Spectral gap global solutions for degenerate Kirchhoff equations
No full textSUMMARY: We consider the second order Cauchy problem where is a continuous function, and is a self-adjoint nonnegative operator with dense domain on a Hilbert space. It is well known that this problem admits local-in-time solutions provided that and are regular enough, depending on the continuity modulus of , and on the strict/weak hyperbolicity of the equation. We prove that for such initial data there exist two pairs of initial data , for which the solution is global, and such that , . This is a byproduct of a global existence result for initial data with a suitable spectral gap, which extends previous results obtained in the strictly hyperbolic case with a smooth nonlinearity
Theta dependence of SU(N) gauge theories in the presence of a topological term
No full textWe review results concerning the theta dependence of 4D SU(N) gauge theories
and QCD, where theta is the coefficient of the CP-violating topological term in
the Lagrangian. In particular, we discuss theta dependence in the large-N
limit.
Most results have been obtained within the lattice formulation of the theory
via numerical simulations, which allow to investigate the theta dependence of
the ground-state energy and the spectrum around theta=0 by determining the
moments of the topological charge distribution, and their correlations with
other observables. We discuss the various methods which have been employed to
determine the topological susceptibility, and higher-order terms of the theta
expansion. We review results at zero and finite temperature. We show that the
results support the scenario obtained by general large-N scaling arguments, and
in particular the Witten-Veneziano mechanism to explain the U(1)_A problem. We
also compare with results obtained by other approaches, especially in the
large-N limit, where the issue has been also addressed using, for example, the
AdS/CFT correspondence.
We discuss issues related to theta dependence in full QCD: the neutron
electric dipole moment, the dependence of the topological susceptibility on the
quark masses, the U(1)_A symmetry breaking at finite temperature.
We also consider the 2D CP(N) model, which is an interesting theoretical
laboratory to study issues related to topology. We review analytical results in
the large-N limit, and numerical results within its lattice formulation.
Finally, we discuss the main features of the two-point correlation function
of the topological charge density
An implicit multishift QR-algorithm for Hermitian plus low rank matrices
No full textHermitian plus possibly unhermitian low rank matrices can be efficiently reduced into Hessenberg form. The resulting Hessenberg matrix can still be written as the sum of a Hermitian plus low rank matrix. In this paper we develop a new implicit multishift QR-algorithm for Hessenberg matrices, which are the sum of a Hermitian plus a possibly non-Hermitian low rank correction.The proposed algorithm exploits both the symmetry and low rank structure to obtain a QR-step involving only O(n) floating point operations instead of the standard O(n^2) operations needed for performing a QR-step on a Hessenberg matrix. The algorithm is based on a suitable O(n) representation of the Hessenberg matrix. The low rank parts present in both the Hermitian and low rank part of the sum are compactly stored by a sequence of Givens transformations and few vectors. Due to the new representation, we cannot apply classical deflation techniques for Hessenberg matrices. A new, efficient technique is developed to overcome this problem. Some numerical experiments based on matrices arising in applications are performed.The experiments illustrate effectiveness and accuracy of both the -algorithm and the newly developed deflation technique
The order of the Roberge-Weiss endpoint (finite size transition) in QCD
No full textWe consider the endpoint of the Roberge-Weiss (RW) first order transition
line present for imaginary baryon chemical potentials. We remark that it
coincides with the finite size transition relevant in the context of large
QCD and study its order in the theory with two degenerate flavors. The RW
endpoint is first order in the limit of large and small quark masses, while it
weakens for intermediate masses where it is likely in the Ising 3d universality
class. Phenomenological implications and further speculations about the QCD
phase diagram are discussed