Absorption and J/psi Suppression in Heavy Ion Collisions

We discuss the J/psi suppression in the framework of multiple collision models. From the analysis of the Pb-Pb NA50 data we conclude that the strength of the absorption has increased, but we find no clear evidence for the formation of the quark-gluon plasma.Comment: 8 pages, 4 figure

Pair creation of particles and black holes in external fields

It is well known that massive black holes may form through the gravitational collapse of a massive astrophysical body. Less known is the fact that a black hole can be produced by the quantum process of pair creation in external fields. These black holes may have a mass much lower than their astrophysical counterparts. This mass can be of the order of Planck mass so that quantum effects may be important. This pair creation process can be investigated semiclassically using non-perturbative instanton methods, thus it may be used as a theoretical laboratory to obtain clues for a quantum gravity theory. In this work, we review briefly the history of pair creation of particles and black holes in external fields. In order to present some features of the euclidean instanton method which is used to calculate pair creation rates, we study a simple model of a scalar field and propose an effective one-loop action for a two-dimensional soliton pair creation problem. This action is built from the soliton field itself and the soliton charge is no longer treated as a topological charge but as a Noether charge. The results are also valid straightforwardly to the problem of pair creation rate of domain walls in dimensions greater than 2.Comment: LaTeX file (World Scientific macros), no figures, 9 pages, talk given at Xth Portuguese Meeting on Astronomy and Astrophysics, (Lisbon, Portugal, 27-28 July 2000), to be published in Proc. Xth A & A meeting, edited by J. P. S. Lemos, A. Mourao, L. Teodoro, R. Ugoccioni, (World Scientific, 2001

Trapped waves between submerged obstacles

Free-surface flows past submerged obstacles in a channel are considered. The fluid is assumed to be inviscid and incompressible and the flow to be irrotational. In previous work involving a single obstacle (Dias & Vanden-Broeck 2002), new solutions called ‘generalized hydraulic falls’ were found. These solutions are characterized by a supercritical flow on one side of the obstacle and a train of waves on the other. However, in the case of a single submerged object, the generalized hydraulic falls are unphysical because the waves do not satisfy the radiation condition. In this paper new solutions for the flow past two obstacles of arbitrary shape are computed. These solutions are characterized by a train of waves ‘trapped’ between the obstacles. The generalized hydraulic falls are shown to describe locally the flow over one of the two obstacles when the distance between the two obstacles is large

How do existential counselling psychologists and psychotherapists feel they construct a sense of being attuned to their clients? A grounded theory study.

Existential counselling psychologists and/or psychotherapists feel that particular moments in psychotherapy can give rise to feelings within them, which they feel can tell them something about the experience of the inner world of the other. This study explores this non-verbal and embodied aspect of the psychotherapeutic relationship using the construct of ‘being attuned’ to clients. Currently, there is a lack of research exploring this topic from existential practitioners’ perspective. A constructivist grounded theory approach was used where eight existential practitioners were interviewed. The concepts being dependent on the inner self, communicating non-verbally, being internally preoccupied, meeting as equals, bringing into view, being supervised and being relational-specific are illuminated as a result of this study. The two key processes found were being empathic and attuned and being within and between. The findings highlight the importance of existential practitioners’ use of their self when sensing, understanding and being with their clients on a non-verbal and embodied level. This study suggests that implementing a relational based understanding of existential practitioners’ use of their self on a non-verbal and embodied level will increase their understanding of their role in the psychotherapeutic encounter and potentially improve their clinical practice