Time Development of Exponentially Small Non-Adiabatic Transitions

Optimal truncations of asymptotic expansions are known to yield approximations to adiabatic quantum evolutions that are accurate up to exponentially small errors. In this paper, we rigorously determine the leading order non--adiabatic corrections to these approximations for a particular family of two--level analytic Hamiltonian functions. Our results capture the time development of the exponentially small transition that takes place between optimal states by means of a particular switching function. Our results confirm the physics predictions of Sir Michael Berry in the sense that the switching function for this family of Hamiltonians has the form that he argues is universal

Research on mediated suffering within social sciences: expert views on identifying a disciplinary home and research agenda

An emerging field of research within social sciences concerns itself with the issue of suffering. Following its growing (mediated) societal prevalence and impact in recent years, suffering has already spurred a rich and diverse body of work. Alongside its emergence within academia, questions arose about its disciplinary home and scope. Drawing on elite interviews with twelve leading scholars, this article positions the on-going research on media and suffering at the heart of social sciences and humanities as well as at the crossroads of different disciplines. This overall open view was reflected in discussions on the current and future scope of the research. Regarding future directions, empirical audience research is high on the academic agenda as are studies that look into the role of new media with regard to suffering. Other widely shared comments referred to a further opening up of the research in terms of methodological and disciplinary approaches

On the media construction of international disasters

For most people living in western countries, disasters are a priori cases of distant suffering as they mainly affect cultural or ethnic others. News media thus play a pivotal role in giving publicity and meaning to the numerous instances of global suffering as it is essentially through media reports that the (western) world witnesses international disasters. Accordingly, several scholars define a disaster as a media construction; they exist only when recognized and covered by the media. This paper focuses on the conceptualization of a disaster as a media construction by exploring the inherently selective nature of news coverage, the representation of suffering in Flemish news media and the possible societal implications

Exponential Asymptotics in a Singular Limit for nn-Level Scattering Systems

The singular limit \eps\ra 0 of the $S$-matrix associated with the equation i\eps d\psi(t)/dt=H(t)\psi(t) is considered, where the analytic generator H(t)\in M_n(\C) is such that its spectrum is real and non-degenerate for all $t\in\R$. Sufficient conditions allowing to compute asymptotic formulas for the exponentially small off-diagonal elements of the $S$-matrix as \eps\ra 0 are explicited and a wide class of generators for which these conditions are verified is defined. These generators are obtained by means of generators whose spectrum exhibits eigenvalue crossings which are perturbed in such a way that these crossings turn to avoided crossings. The exponentially small asymptotic formulas which are derived are shown to be valid up to exponentially small relative error, by means of a joint application of the complex WKB method together with superasymptotic renormalization. The application of these results to the study of quantum adiabatic transitions in the time dependent Schr\"odinger equation and of the semiclassical scattering properties of the multichannel stationary Schr\"odinger equation closes this paper. The results presented here are a generalization to $n$-level systems, $n\geq 2$, of results previously known for $2$-level systems only.Comment: 35 pages, Late

Density of States and Thouless Formula for Random Unitary Band Matrices

We study the density of states measure for some class of random unitary band matrices and prove a Thouless formula relating it to the associated Lyapunov exponent. This class of random matrices appears in the study of the dynamical stability of certain quantum systems and can also be considered as a unitary version of the Anderson model. We further determine the support of the density of states measure and provide a condition ensuring it possesses an analytic density

Peer recognition of prodromal signs of psychosis : a signal detection analysis : a thesis presented in partial fulfilment of the requirements for the degree in Master of Arts in Psychology at Massey University, Palmerston North, New Zealand

Using signal detection analysis, this study investigated young peoples' sensitivity to prodromal signs or psychotic symptoms compared to more everyday signs of distress in their friends. In a questionnaire format, 117 high school students (aged 13 to 16 years) were asked to report the level of concern they would have if one of their friends exhibited certain characteristics. Half of the latter were neutral, everyday phenomena (no signal), and the remainder were either DSM-IV symptoms of psychosis or empirically-derived prodromal signs of early onset psychosis (signal). Each possible sign was modified (made more serious) by descriptors used in psychological models to define pathology behaviorally: rare in youth, high in frequency, recent change, and lack of obvious (rational) environmental cause. High frequency was the modifier leading to the greatest degree of concern. Accurate and sensitive detection, based on d' values, was adequate for psychotic symptoms, especially by females rather than by males, although depressed mood (a prodromal sign in this context) was most readily detected as a worrisome feature. The study has implications for analyzing how youth judge indices of distress in their friends and for their general ability to recognize that certain characteristics are more troublesome than others. Telling a responsible adult of their concerns was the most frequently suggested response, followed by attempting to help and talking to the peer about their concerns. If rapid detection of early onset psychosis is to be a goal of preventative mental health services, youth who are sensitive to classic symptoms of psychosis may still need educating in recognizing the difference between behavioral characteristics that are part of everyday distress and those that are indicative of more serious adjustment difficulties that might be emerging

Spectral Properties of Non-Unitary Band Matrices

We consider families of random non-unitary contraction operators defined as deformations of CMV matrices which appear naturally in the study of random quantum walks on trees or lattices. We establish several deterministic and almost sure results about the location and nature of the spectrum of such non-normal operators as a function of their parameters. We relate these results to the analysis of certain random quantum walks, the dynamics of which can be studied by means of iterates of such random non-unitary contraction operators.Comment: updated version, to appear in Annales Henri Poincar