The topological susceptibility of two-dimensional U(N)U(N) gauge theories

In this paper we study the topological susceptibility of two-dimensional $U(N)$ gauge theories. We provide explicit expressions for the partition function and the topological susceptibility at finite lattice spacing and finite volume. We then examine the particularly simple case of the abelian $U(1)$ theory, the continuum limit, the infinite volume limit, and we finally discuss the large $N$ limit of our results.Comment: 11 pages, 7 eps figure

Foreigners, Immigrants, Host Cities: The Policies of Multi-Ethnicity in Rome. Reading Governance in a Local Context

This paper reviews the experience of Rome in dealing with the challenges posed by a multi-ethnic society. A central feature of the local political strategy is the “Pact of Integration”. The adoption of the Pact proposes governance as a model of participation including many actors, namely immigrant communities, in the comprehensive development of the quality of life of the city and not only in the decision-making mechanisms of local powers. The Pact represents a contract by which the social and political acceptance of foreigners in the local environment is perceived as benefiting both the foreign and autochthonous communities. On one hand, immigrants are incorporated into their local environment, following from the recognition of foreigners’ rights and needs for solidarity. On the other hand, foreigners are considered agents of local development insofar as they are both consumers and producers. The multiethnic society can then be a source of development. The preface by Franca Eckert Coen provides an overview of the city’s experiences in managing religious differences.Immigration, Governance, Multi-ethnicity

Tracking moving optima using Kalman-based predictions

The dynamic optimization problem concerns finding an optimum in a changing environment. In the field of evolutionary algorithms, this implies dealing with a timechanging fitness landscape. In this paper we compare different techniques for integrating motion information into an evolutionary algorithm, in the case it has to follow a time-changing optimum, under the assumption that the changes follow a nonrandom law. Such a law can be estimated in order to improve the optimum tracking capabilities of the algorithm. In particular, we will focus on first order dynamical laws to track moving objects. A vision-based tracking robotic application is used as testbed for experimental comparison

El centro comercial como modificador del con-texto: Bogotá dilatada, comprimida y emulsionada

La ciudad de Bogotá se puede definir como una red de complejidades conformada por las actividades e interacciones de los individuos que la habitan un extenso territorio. En la actualidad, esta definición queda determinada por el resultado del crecimiento y transformación urbana que gira en torno a las nuevas actividades de consumo y ocio. El espacio público clásico, cada vez más reducido en términos de su esfera de influencia e identidad, no concentra las diferentes actividades que dinamizan el habitar en comunidad, por lo tanto, la forma y el contenido de éste lugar público, se trasladada a la unidad edilicia “privadas” llamada shopping mall. Este espacio/edificio es el resultado de los cambios en las dinámicas sociales de la sociedad contemporánea de la capital latinoamericana.Bogotá, can be defined as a network of activities, comprised complexities and interactions of individuals that inhabit this extended territory. Currently, this definition is determined by the result of growth and urban transformation that revolves around new consumption and leisure activities. The classic public space, increasingly reduced in terms of its sphere of influence and identity, does not concentrate the different activities that invigorate the dwell in community, therefore, the form and content of this public place, is transferred to the "private unit" calls shopping mall. This space / building is the result of changes in the social dynamics of contemporary society of this Latin American capital.Peer Reviewe

Static and dynamic properties of synaptic transmission at the cyto-neural junction of frog labyrinth posterior canal

The properties of synaptic transmission have been studied at the cyto-neural junction of the frog labyrinth posterior canal by examining excitatory postsynaptic potential (EPSP) activity recorded intraaxonally from the afferent nerve after abolishing spike firing by tetrodotoxin. The waveform, amplitude, and rate of occurrence of the EPSPs have been evaluated by means of a procedure of fluctuation analysis devised to continuously monitor these parameters, at rest as well as during stimulation of the semicircular canal by sinusoidal rotation at 0.1 Hz, with peak accelerations ranging from 8 to 87 deg.s-2. Responses to excitatory and inhibitory accelerations were quantified in terms of maximum and minimum EPSP rates, respectively, as well as total numbers of EPSPs occurring during the excitatory and inhibitory half cycles. Excitatory responses were systematically larger than inhibitory ones (asymmetry). Excitatory responses were linearly related either to peak acceleration or to its logarithm, and the same occurred for inhibitory responses. In all units examined, the asymmetry of the response yielded nonlinear two-sided input-output intensity functions. Silencing of EPSPs during inhibition (rectification) was never observed. Comparison of activity during the first cycle of rotation with the average response over several cycles indicated that variable degrees of adaptation (up to 48%) characterize the excitatory response, whereas no consistent adaptation was observed in the inhibitory response. All fibers appeared to give responses nearly in phase with angular velocity, at 0.1 Hz, although the peak rates generally anticipated by a few degrees the peak angular velocity. From the data presented it appears that asymmetry, adaptation, and at least part of the phase lead in afferent nerve response are of presynaptic origin, whereas rectification and possible further phase lead arise at the encoder. To confirm these conclusions a simultaneous though limited study of spike firing and EPSP activity has been attempted in a few fibers

Cooperation Strategies for Enhanced Connectivity at Home

WHILE AT HOME , USERS MAY EXPERIENCE A POOR I NTERNET SERVICE while being connected to their 802.11 Access Points (APs). The AP is just one component of the Internet Gateway (GW) that generally includes a backhaul connection (ADSL, fiber,etc..) and a router providing a LAN. The root cause of performance degradation may be poor/congested wireless channel between the user and the GW or congested/bandwidth limited backhaul connection. The latter is a serious issue for DSL users that are located far from the central office because the greater the distance the lesser the achievable physical datarate. Furthermore, the GW is one of the few devices in the home that is left always on, resulting in energy waste and electromagnetic pollution increase. This thesis proposes two strategies to enhance Internet connectivity at home by (i) creating a wireless resource sharing scheme through the federation and the coordination of neighboring GWs in order to achieve energy efficiency while avoiding congestion, (ii) exploiting different king of connectivities, i.e., the wired plus the cellular (3G/4G) connections, through the aggregation of the available bandwidth across multiple access technologies. In order to achieve the aforementioned strategies we study and develop: • A viable interference estimation technique for 802.11 BSSes that can be implemented on commodity hardware at the MAC layer, without requiring active measurements, changes in the 802.11 standard, cooperation from the wireless stations (WSs). We extend previous theoretical results on the saturation throughput in order to quantify the impact in term of throughput loss of any kind of interferer. We im- plement and extensively evaluate our estimation technique with a real testbed and with different kind of interferer, achieving always good accuracy. • Two available bandwidth estimation algorithms for 802.11 BSSes that rely only on passive measurements and that account for different kind of interferers on the ISM band. This algorithms can be implemented on commodity hardware, as they require only software modifications. The first algorithm applies to intra-GW while the second one applies to inter-GW available bandwidth estimation. Indeed, we use the first algorithm to compute the metric for assessing the Wi-Fi load of a GW and the second one to compute the metric to decide whether accept incoming WSs from neighboring GWs or not. Note that in the latter case it is assumed that one or more WSs with known traffic profile are requested to relocate from one GW to another one. We evaluate both algorithms with simulation as well as with a real test-bed for different traffic patterns, achieving high precision. • A fully distributed and decentralized inter-access point protocol for federated GWs that allows to dynamically manage the associations of the wireless stations (WSs) in the federated network in order to achieve energy efficiency and offloading con- gested GWs, i.e, we keep a minimum number of GWs ON while avoiding to create congestion and real-time throughput loss. We evaluate this protocol in a federated scenario, using both simulation and a real test-bed, achieving up to 65% of energy saving in the simulated setting. We compare the energy saving achieved by our protocol against a centralized optimal scheme, obtaining close to optimal results. • An application level solution that accelerates slow ADSL connections with the parallel use of cellular (3G/4G) connections. We study the feasibility and the potential performance of this scheme at scale using both extensive throughput measurement of the cellular network and trace driven analysis. We validate our solution by implementing a real test bed and evaluating it “in the wild, at several residential locations of a major European city. We test two applications: Video-on-Demand (VoD) and picture upload, obtaining remarkable throughput increase for both applications at all locations. Our implementation features a multipath scheduler which we compare to other scheduling policies as well as to transport level solution like MTCP, obtaining always better results

Conpsumptionscapes: estereotipos de videojuegos y ambientes urbanos de Latinoamérica. Casos de estudio: Uncharted 3: Drake’s Deception / Uncharted 4: The Thief End

The consumption landscape refers to the context in which the daily basic needs of a society are determined. The small store in the neighborhood and the street market are architectural structures or urban spaces which shape the lives of cities as we know them today. Shopping centres are the evolution of these building formats and can characterize contemporary life. The exercise proposed by this article is to review the condition of the contexts of consumption in which the narrative of video games are developed through the study and selection of cases (Uncharted 3: Drake’s Deception / Uncharted 4: A Thief’s End). These demonstrate that the urban landscape with which our cities are represented appears as scenarios loaded with stereotypes. The emphasis of this research is on the representation of the historical Latin American city as a spatially modelled and stereotyped territory where the narrative is contextualized. This article does not focus on how the story develops within a commercial space but instead proposes a transversal idea that the consumption contexts are landscapes determined by cultural logics where the plot occurs. Consumption landscapes are the simultaneous spatial, cultural and historical constructions that give meaning to a narrative and represent an augmented reality of our cities: extensive, immersive and suggestive, but also perverse.El paisaje de consumo se refiere al contexto en el que las necesidades básicas de una sociedad se determinan diariamente. La pequeña tienda en el barrio y el mercado de calle, son estructuras arquitectónicas o espacios urbanos, que dieron forma a la vida de las ciudades como la conocemos hoy. Los centros comerciales son la evolución de estos formatos de construcción y pueden caracterizar la vida contemporánea. El ejercicio propuesto por este artículo es revisar la condición de los contextos de consumo en los que se desarrolla la narrativa de los videojuegos a través del estudio y la selección de casos (Uncharted 3: Drake’s Deception / Uncharted 4: A Tief’s End) que demuestran que, el paisaje urbano con el que se representan nuestras ciudades aparece como un contexto cargado de estereotipos donde la vida cotidiana tiene lugar. El foco de la investigación está en la representación de la ciudad histórica latinoamericana como un territorio modelado espacialmente y estereotipada como un contexto narrativo jugable. No es importante determinar si la historia se desarrolla dentro de un espacio comercial, sino proponer la idea transversal de que los contextos de consumo que estructuran dichos paisajes y que determinan las lógicas culturales donde se desarrolla la trama. Los paisajes de consumo son la construcción espacial, cultural e histórica (al mismo tiempo) que da sentido a la narrativa y representa una realidad aumentada de nuestras ciudades: extensa, inmersiva y sugerente, pero también perversa