Setting up tunneling conditions by means of Bohmian mechanics

Usually tunneling is established after imposing some matching conditions on the (time-independent) wave function and its first derivative at the boundaries of a barrier. Here an alternative scheme is proposed to determine tunneling and estimate transmission probabilities in time-dependent problems, which takes advantage of the trajectory picture provided by Bohmian mechanics. From this theory a general functional expression for the transmission probability in terms of the system initial state can be reached. This expression is used here to analyze tunneling properties and estimate transmissions in the case of initial Gaussian wave packets colliding with ramp-like barriers.Comment: 18 pages, 4 figure

Palestine in the British press: a postcolonial critical discourse analysis

This article examines the representations of the Israeli Palestinian conflict in the British press, starting from the premise that media representations in Britain should be analysed in relation to Britain’s role as a postcolonial power. Focusing on Britain’s colonial and postcolonial connection to this conflict, this study is based on the findings of a Postcolonial Critical Discourse Analysis of four British national newspapers (the Guardian, or Manchester Guardian; The Times; the Daily Herald, or the Sun; and the Daily Mirror) at four different points during the history of the conflict. The findings indicate that the classification of Palestine, Palestinians, Israel, Israelis, Jews, Zionists and Arabs as agents of political violence evolved over time, as violent acts and agents were perceived differently according to the dominant political discourse during each period. The contextualization of the conflict also provides insights into how the British press constructed its various ideological positions in relation to this conflict, and the extent to which the British Mandate remained visible in the later coverage of the conflict. The postcolonial approach adopted in this study indicates that the generalized lack of references to the historical facts that underpin Britain’s role in the development of the conflict represents an attempt to move away from the historical responsibilities derived from colonial encounters. This framework therefore helps to restore the largely neglected historical connection of the British Mandate to its proper place in the analysis of these mediated events

Local memories: conflict and lived experience in the Spanish Civil War

The winners of any conflict often try to impose their views on the defeated. Through official and unofficial mechanisms, most of which operate under the aegis of the state and other agents that work on its behalf, the voices of the defeated are silenced. One important counter-mechanism that is available, the one that may serve to resist the imposition of the victors’ History, is frequently found in the collection, analysis and publication of oral testimonies, which give expression to, and magnify, silenced and oppressed memories. Orality therefore provides us with a window into past events or, rather, with multiple windows that allow us to see and take account of the myriad histories of which the past is actually composed, according not to the state-imposed version, but to the ways in which people remember it. Through an ethnographic study of local memories in one southern Spanish village, this article examines some of the ways in which the Spanish Civil War is remembered, focusing particularly on the lived experience of repression and hunger, and the memories of ideological clashes, class struggles and conflicts over land ownership

Online communities of Spanish Migrants in times of austerity

This article examines the perceptions, held by Spanish migrants, of the extent to which social media facilitate the development of a sense of community within their host towns and cities. Focusing particularly on the creation of Facebook groups called ‘Españoles en…’ (‘Spaniards in…’), the study explores the role that these online tools play in the development of connections between Spanish citizens who reside in the same locality. The aim, therefore, is to ask how they try to maintain their socio-cultural identities within a diasporic community, especially one that has suffered the effects of economic austerity. Based on the results of a qualitative survey answered by Spanish migrants living in Britain, France and Germany, the article sheds light on the relative usefulness - as perceived by the migrants themselves - of online engagement in the maintenance and development of a communal mind-set. The piece suggests that the migrants’ individual backgrounds and experiences, including their individual political stances, skills, socio-economic circumstances, and regional affiliations, seem to play a more important role in shaping their conceptions of the online ‘community’, than any broader assumptions made about unitary national identity or the role of technology

Adsorbate surface diffusion: The role of incoherent tunneling in light particle motion

The role of incoherent tunneling in the diffusion of light atoms on surfaces is investigated. With this purpose, a Chudley-Elliot master equation constrained to nearest neighbors is considered within the Grabert-Weiss approach to quantum diffusion in periodic lattices. This model is applied to recent measurements of atomic H and D on Pt(111), rendering friction coefficients that are in the range of those available in the literature for other species of adsorbates. A simple extension of the model has also been considered to evaluate the relationship between coverage and tunneling, and therefore the feasibility of the approach. An increase of the tunneling rate has been observed as the surface coverage decreases.Comment: 7 pages, 2 figures; important reorganization of the work (including title changes

Phonon lineshapes in atom-surface scattering

Phonon lineshapes in atom-surface scattering are obtained from a simple stochastic model based on the so-called Caldeira-Leggett Hamiltonian. In this single-bath model, the excited phonon resulting from a creation or annihilation event is coupled to a thermal bath consisting of an infinite number of harmonic oscillators, namely the bath phonons. The diagonalization of the corresponding Hamiltonian leads to a renormalization of the phonon frequencies in terms of the phonon friction or damping coefficient. Moreover, when there are adsorbates on the surface, this single-bath model can be extended to a two-bath model accounting for the effect induced by the adsorbates on the phonon lineshapes as well as their corresponding lineshapes.Comment: 14 pages, 2 figure