Stable rank of leavitt path algebra

We characterize the values of the stable rank for Leavitt path algebras, by giving concrete criteria in terms of properties of the underlying graph.

Model structures on the category of small double categories

In this paper we obtain several model structures on DblCat, the category of small double categories. Our model structures have three sources. We first transfer across a categorification-nerve adjunction. Secondly, we view double categories as internal categories in Cat and take as our weak equivalences various internal equivalences defined via Grothendieck topologies. Thirdly, DblCat inherits a model structure as a category of algebras over a 2-monad. Some of these model structures coincide and the different points of view give us further results about cofibrant replacements and cofi brant objects. As part of this program we give explicit descriptions and discuss properties of free double categories, quotient double categories, colimits of double categories, and several nerves and categorifications.

Quantum symmetries for exceptional SU(4) modular invariants associated with conformal embeddings

Three exceptional modular invariants of SU(4) exist at levels 4, 6 and 8. They can be obtained from appropriate conformal embeddings and the corresponding graphs have self-fusion. From these embeddings, or from their associated modular invariants, we determine the algebras of quantum symmetries, obtain their generators,and, as a by-product, recover the known graphs E4, E6 and E8 describing exceptional quantum subgroups of type SU(4). We also obtain characteristic numbers (quantum cardinalities, dimensions) for each of them and for their associated quantum groupoïds.

A model structure for coloured operads in symmetric spectra

We describe a model structure for coloured operads with values in the category of symmetric spectra (with the positive model structure), in which fibrations and weak equivalences are defined at the level of the underlying collections. This allows us to treat R-module spectra (where R is a cofibrant ring spectrum) as algebras over a cofibrant spectrum-valued operad with R as its first term. Using this model structure, we give sufficient conditions for homotopical localizations in the category of symmetric spectra to preserve module structures.

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Equivariant semiprojectivity

We define equivariant semiprojectivity for C* -algebras equipped with actions of compact groups. We prove that the following examples are equivariantly semiprojective: A. Arbitrary finite dimensional C*-algebras with arbitrary actions of compact groups. - B. The Cuntz algebras Od and extended Cuntz algebras Ed, for finite d, with quasifree actions of compact groups. - C. The Cuntz algebra O∞ with any quasifree action of a finite group. For actions of finite groups, we prove that equivariant semiprojectivity is equiv- alent to a form of equivariant stability of generators and relations. We also prove that if G is finite, then C*(G) is graded semiprojective.

Desarrollo de un softphone, implementación de una centralita basada en código libre e integración con herramienta CRM

El proyecto consiste en la creación mediante software libre de un sistema de telefonía corporativo, que ofrece la mayor parte de las funcionalidades de un sistema telefónico implantado en cualquier PYME de la actualidad y que tiene como elemento principal una centralita telefónica Asterisk, así como en el desarrollo de un softphone(teléfono software) utilizando el protocolo de señalización SIP, que explota gran parte de las funcionalidades que proporciona la centralita. Este sistema de telefonía tiene además la capacidad de integrarse con herramientas CRM a través de la importación de los contactos en el listín corporativo del softphone.

Space-time within general relativity : a structural realist understanding

ABSTRACT This dissertation investigates the, nature of space-time as described by the theory of general relativity. It mainly argues that space-time can be naturally interpreted as a physical structure in the precise sense of a network of concrete space-time relations among concrete space-time points that do not possess any intrinsic properties and any intrinsic identity. Such an interpretation is fundamentally based on two related key features of general relativity, namely substantive general covariance and background independence, where substantive general covariance is understood as a gauge-theoretic invariance under active diffeomorphisms and background independence is understood in the sense that the metric (or gravitational) field is dynamical and that, strictly speaking, it cannot be uniquely split into a purely gravitational part and a fixed purely inertial part or background. More broadly, a precise notion of (physical) structure is developed within the framework of a moderate version of structural realism understood as a metaphysical claim about what there is in the world. So, the developement of this moderate structural realism pursues two main aims. The first is purely metaphysical, the aim being to develop a coherent metaphysics of structures and of objects (particular attention is paid to the questions of identity and individuality of these latter within this structural realist framework). The second is to argue that moderate structural realism provides a convincing interpretation of the world as described by fundamental physics and in particular of space-time as described by general relativity. This structuralist interpretation of space-time is discussed within the traditional substantivalist-relationalist debate, which is best understood within the broader framework of the question about the relationship between space-time on the one hand and matter on the other. In particular, it is claimed that space-time structuralism does not constitute a 'tertium quid' in the traditional debate. Some new light on the question of the nature of space-time may be shed from the fundamental foundational issue of space-time singularities. Their possible 'non-local' (or global) feature is discussed in some detail and it is argued that a broad structuralist conception of space-time may provide a physically meaningful understanding of space-time singularities, which is not plagued by the conceptual difficulties of the usual atomsitic framework. Indeed, part of these difficulties may come from the standard differential geometric description of space-time, which encodes to some extent this atomistic framework; it raises the question of the importance of the mathematical formalism for the interpretation of space-time.

Softphone con soporte IAX2 para Android

El principal propósito del proyecto consiste en el intento de desarrollo de un softphone para Android empleando para ello el protocolo IAX2 soportado por la PBX Asterisk

Proyecto de migración a un sistema de telefonia IP (VOIP) basado en software libre.

Una empresa de grandària mitja s'embarca en un projecte de migració del seu sistema telefònic, basat en un model tradicional i amb múltiples problemes, tant a nivell de funcionalitat com de costos, i decideix apostar per una solució basada en programari lliure, amb Linux i Asterisk com peces angulars del disseny del projecte.

Implantación de sistema VoIP en alta disponibilidad y distribución de carga

Este documento describe el proceso de diseño, configuración e implantación de un sistema clúster VoIP basado íntegramente en software libre.

Estudio de la tecnología VoIP a través de Elastix

Estudio sobre cómo encaja la tecnología IP en el mundo de la telefonía para ver qué ventajas e inconvenientes supone cada posible solución a un problema, y elegir la mejor.

Treball Final de Master - Servidor de Comunicacions Unificades

L'objectiu d'aquest projecte és la creació d'una prova de concepte de comunicacions unificades utilitzant productes de programari lliure existents. Aquesta prova de concepte servirà per poder fer demostracions del funcionament general del programari implicat amb el mínim de preparacions, instal·lacions i configuracions prèvies possibles. El projecte es dividirà en dos appliances o LiveCD, creats a traves de Suse Studio, anomenats Comunicacions Unificades i Comunicacions Unificades 2.Els productes de programari lliure que composen el Servidor de Comunicacions Unificades els podem classificar en productes principals, plugins o addons dels productes i productes secundaris.Com a productes principals tenim els següents servidors que cobreixen les necessitats principals del Servidor de Comunicacions Unificades:Asterisk v1.8.3 : Servidor de telefonia amb veu sobre IP (VoIP).FreePBX v2.9.0beta2 : GUI de control i administració d'Asterisk.Openfire v3.7.0 : Servidor de IM basat en el protocol XMPP.BigBlueButton v0.71a : Sistema de conferència web. Pendent finalitzar-ne l'implementació.I els seguents productes principals que cobreixen les necessitats del servidor de Comunicacions Unificades 2:Zimbra v7.0.1 : Servidor de correu electrònic i de calendari. Pendent resoldre conflicte inicialització LDAP.Funambol v9.0.0 : Sincronització Zimbra amb mòbils.Com a plugins o addons del productes tenim, classificats segons el producte:Asterisk addons: chan_jingle i chan_gtalkZimlets: Asterisk, Google Translator, Funambol i SocialsOpenfire pugins: Asterisk, Facebook i GmailCom a productes secundaris tenim els clients necessaris per poder utilitzar l'appliance:Firefox: Navegador web que servirà com a interfície d'usuari per les diferents eines d'administració i la demostració.Pigdin o Spark: Clients de missatgeria instantània, per l'appliance Comunicacions Unificades.A més d'instal·lar aquests productes, s'implementa una interfície web, mitjançant Drupal, en format HTML per enllaçar les diferents eines d'administració dels productes, per a cadascun dels dos appliances i es realitzara un Kiosk appliance per a familiaritzar-se amb l'entorn SuseStudio.

Centraleta PBX

Creació d'un producte de centraleta telefònica IP amb la integració de tots els serveis auxiliars. Això inclou la part de seguretat i els serveis de xarxa.