Detection of Charged MSSM Higgs Bosons at CERN LEP-II and NLC

We study the possibility of detecting the charged Higgs bosons predicted in the Minimal Supersymmetric Standard Model $(H^\pm)$, with the reactions $e^{+}e^{-}\to \tau^-\bar \nu_{\tau}H^+, \tau^+\nu_\tau H^-$, using the helicity formalism. We analyze the region of parameter space $(m_{A^0}-\tan\beta)$ where $H^\pm$ could be detected in the limit when $\tan\beta$ is large. The numerical computation is done for the energie which is expected to be available at LEP-II ($\sqrt{s}=200$ GeV) and for a possible Next Linear $e^{+}e^{-}$ Collider ($\sqrt{s}=500$ GeV).Comment: Latex file and 5 figure

Non-ergodic states induced by impurity levels in quantum spin chains

The semi-infinite XY spin chain with an impurity at the boundary has been chosen as a prototype of interacting many-body systems to test for non-ergodic behavior. The model is exactly solvable in analytic way in the thermodynamic limit, where energy eigenstates and the spectrum are obtained in closed form. In addition of a continuous band, localized states may split off from the continuum, for some values of the impurity parameters. In the next step, after the preparation of an arbitrary non-equilibrium state, we observe the time evolution of the site magnetization. Relaxation properties are described by the long-time behavior, which is estimated using the stationary phase method. Absence of localized states defines an ergodic region in parameter space, where the system relaxes to a homogeneous magnetization. Out of this region, impurity levels split from the band, and localization phenomena may lead to non-ergodicity.Comment: 10 pages, 5 figures. arXiv admin note: substantial text overlap with arXiv:1703.0344

Relativistic Quantum Scattering of High Energy Fermions in the Presence of Phase Transition

We study the high energy behaviour of fermions hitting a general wall caused by a first-order phase transition. The wall profile is introduced through a general analytic function. The reflection coefficient is computed in the high energy limit and expressed in terms of the poles of the wall profile function. It is shown that the leading singularity gives the high energy behaviour.Comment: 10 page

Urban utopias in Havana's representations. An interdisciplinary analysis

This investigation consists of an interdisciplinary analysis of photographic, cinematographic, architectural and literary documents representing the city of Havana in Cuba during different periods of the twentieth century. These periods are: the decade of the Great Depression; the 1950s during the rapid growth of the tourist industry in the island; the first fifteen years following the 1959 Cuban Revolution; and the so-called 'Special Period' during the 1990s, following the collapse of the Soviet Union. It was during these periods that the city went through very important transformations due to historical and cultural contingencies. These contingencies refer to the beginnings of the development of the city as a tourist centre, the first debates and cultural manifestations related to the Afro-Cuban traditions in the island, the post - 1959 evolutionary processes and the effects of the end of the Cold War on the city. The documents analysed have been drawn firstly from cultural productions made by Cubans: Cuban filmography and photography pre- and post-1959. Secondly, there are also those documents produced by non-Cubans, mainly Hollywood productions and other types of representation, which have also contributed greatly to create a particular image of Havana. An important part of this analysis also includes the architectural particularities of the city, with an emphasis on the symbology of some of its main buildings, such as the Capitolio and the National Hotel. This analysis relates the dominant visual tropes of the Cuban capital with more generic discourses regarding the tradition of utopian thought in the West and their embodiment in the image of the modern city. The diverse archival documents discussed throughout this thesis reflect recurrent themes that have characterised this tradition: the contemporary ideal of a harmonious multicultural society; the romanticisation of the 'old city' as a visual reminder of our 'non-capitalist' past and the utopianism associated with the dichotomy between work and leisure and between the diurnal and the nocturnal. Most of these themes can be found as forming part of the discourse on the national in Cuba, also characterised by a deep utopianism. The thesis examines the social and cultural history of Havana in order to analyse how the different documents have reflected, or even contributed, to the construction and problematisation of a Cuban national identity, while at the same time making testimony of the existence in the city of different cultural traditions. This has necessarily involved a reflection on the dynamics between the two main cultural traditions present in Havana: the Euro-Cuban and the Afro-Cuban. This thesis proposes that the cultural battles between the African, European and North American traditions in the city have been decisive in the modern re-fashioning of Havana as a museum-city, facilitating the predominantly nostalgic character of its most recent representations. This investigation also takes into account the crucial role of the city's spatial gendrification - the position of women within the urban space - when describing Havana's utopian representations. Finally, the interdisciplinary character of this thesis contributes to the analyses of the cultural history of cities as well as the relevance of the visual in the recreations of modern urban life and its relations to the narratives of the national