A study on relativistic lagrangian field theories with non-topological soliton solutions

We perform a general analysis of the dynamic structure of two classes of relativistic lagrangian field theories exhibiting static spherically symmetric non-topological soliton solutions. The analysis is concerned with (multi-) scalar fields and generalized gauge fields of compact semi-simple Lie groups. The lagrangian densities governing the dynamics of the (multi-) scalar fields are assumed to be general functions of the kinetic terms, whereas the gauge-invariant lagrangians are general functions of the field invariants. These functions are constrained by requirements of regularity, positivity of the energy and vanishing of the vacuum energy, defining what we call "admissible" models. In the scalar case we establish the general conditions which determine exhaustively the families of admissible lagrangian models supporting this kind of finite-energy solutions. We analyze some explicit examples of these different families, which are defined by the asymptotic and central behaviour of the fields of the corresponding particle-like solutions. From the variational analysis of the energy functional, we show that the admissibility constraints and the finiteness of the energy of the scalar solitons are necessary and sufficient conditions for their linear static stability against small charge-preserving perturbations. Furthermore we perform a general spectral analysis of the dynamic evolution of the small perturbations around the statically stable solitons, establishing their dynamic stability. Next, we consider the case of many-components scalar fields, showing that the resolution of the particle-like field problem in this case reduces to that of the one-component case. The study of these scalar models is a necessary step in the analysis of the gauge fields.Comment: LaTeX (uses elsart.cls), 57 pages, 9 Postscript figures, final version to appear in Annals of Physics, some minor corrections adde

Search for fast optical transients using archival VERITAS data

Fast optical transient phenomena have been observed in the cosmos. Conventional optical telescopes typically lack the fine time resolution required to investigate sub-second transients. Ground based Cherenkov telescopes are powerful devices for finding optical transients as they are designed to capture optical lightbursts on nanosecond time scales. The Very Energetic Radiation Imaging Telescope Array System (VERITAS) is an array of four imaging atmospheric Cherenkov telescopes (IACTs) that has been collecting data since 2007. A significant portion of the archived data corresponds to background signals that can be surveyed to find transient events. We discuss a methodology for conducting an archival search for serendipitous transients. With the analysis employed we achieved a nominal time resolution of approximately 150 ms and a limiting blue band magnitude of 8.9. The archival search revealed signals from transients occurring in the atmosphere, including meteor-like events and satellite flares. No astrophysical or astronomical candidates were found.Des ph ́enomnes de transmissions optiques rapides ont été observer dans le cosmos. Cependant, les télescopes optiques conventionnels n'ont pas la résolution temporelle suffisante pour observer des transmissions de moins dune seconde. Nous utilisons Les télescopes de Tcherenkov pour ce faire, ce sont des outils puissants pour trouver ces transmissions optiques. Ils peuvent capter des impulsions de transmission optique à l'échelle de la nanoseconde. En fonction depuis 2007, VERITAS (Very Energetic Radiation Imaging Telescope Array System) est un réseau de 4 télescopes a imagerie Tcherenkov atmosphérique. Une grande partie des données d'archive corresponde à des signaux de fond qui peuvent être examiner pour trouver événement de transmission optique. Dans cette thèse, nous développons une méthodologie pour trouver des transmissions optiques fortuite dans les archives. L'analyse utilise permet d'atteindre une résolution nominale temporelle d'approximativement 150 ms et d'une limite dans la bande B de magnitude 8.9. Les recherches dans les archives ont révélé des signaux des transmissions optiques ayant eu lieu dans l'atmosphere, cela inclut les météorites et les satellites. Aucun candidat astrophysique ou astronomique n'a été observer

Growth observations on European (Anguilla anguilla L.) and American (Anguilla rostrata Le Sueur) glass eels

Comparative growth observations (13 months) of European (Anguilla anguilla L.) and American (Anguilla rostrata Le Sueur) glass eels were undertaken. Plastic containers (60 x 30 x 35 cm, volume of 30 L) were combined with a sedimentation tank and submerged, gravel, biological filter to form a recirculation system. Feeding commenced on the second day after arrival of the fish and proceeded as follows : days 1 to 50, krill hydrolysate ; days 51 to 58, krill hydrolysate mixed with a salmon starter feed ; day 59 onwards, standard salmon feed. Feed was provided at 2-hourly intervals via automatic feeders for the first 161 days of rearing, and thereafter by hand 5 times a day at a feeding rate of 5 % of the fish biomass. The average individual weight of the European eels on rrival (x = 0.266 ± 0.005 g), was significantly higher than that of the American eels (x = 0.167 ± 0.006 g). After 45 days of rearing, the weight differences between the species became insignificant. Except for the different transportation mortalities on arrival, the European and the American eels demonstrated similar mortality rates during the experiment ( 1 2 . 5 % ) , food conversion rate (2.3) and specific growth rate (0.90 and 0.99 respectively). No parasites or diseases were detected. No differences were observed in general behaviour and feeding between the two species

Summer survival and activity patterns of estuary feeding anadromous Salmo trutta

There is generally a very poor understanding of how anadromous brown trout, Salmo trutta, use marine ecosystems. In this study, we use acoustic telemetry techniques to test four alternative hypotheses for estuarine coastal habitat use by this species on a population in the Clyde, west‐central Scotland. Anadromous brown trout in their second (or more) summer feeding in the marine environment did not show patterns of estuarine use predicted from studies on other populations of this species. They did not (a) use the inner Clyde Estuary as a staging post for onward migration to open coastal waters, nor did they (b) pass through the estuary rapidly nor did they (c) make multiple incursions into freshwater. In contrast, fish utilised a very geographically constrained area of the inner estuary (<8 km in length), within which fish were highly mobile, exhibiting more activity during a flooding tide and exhibited high survivorship compared with reports from other studies. The reasons why estuarine use by anadromous brown trout in the Clyde may differ from that reported elsewhere is discussed