First results for the Coulomb gauge integrals using NDIM

The Coulomb gauge has at least two advantages over other gauge choices in that bound states between quarks and studies of confinement are easier to understand in this gauge. However, perturbative calculations, namely Feynman loop integrations, are not well defined (there are the so-called energy integrals) even within the context of dimensional regularization. Leibbrandt and Williams proposed a possible cure to such a problem by splitting the space-time dimension into D = ω + ρ, i.e., introducing a specific parameter ρ to regulate the energy integrals. The aim of our work is to apply the negative dimensional integration method (NDIM) to the Coulomb gauge integrals using the recipe of split-dimension parameters and present complete results - finite and divergent parts - to the one- and two-loop level for arbitrary exponents of the propagators and dimension.

Improved Langevin approach to spinodal decomposition in the chiral transition

We use an improved Langevin description that incorporates both additive and multiplicative noise terms to study the dynamics of phase ordering. We perform real-time lattice simulations to investigate the role played by different contributions to the dissipation and noise. Lattice-size independence is assured by the use of appropriate lattice counterterms. © 2006 American Institute of Physics.

A rationale for long-lived quarks and leptons at the LHC: low energy flavour theory

In the framework of gauged flavour symmetries, new fermions in parity symmetric representations of the standard model are generically needed for the compensation of mixed anomalies. The key point is that their masses are also protected by flavour symmetries and some of them are expected to lie way below the flavour symmetry breaking scale(s), which has to occur many orders of magnitude above the electroweak scale to be compatible with the available data from flavour changing neutral currents and CP violation experiments. We argue that, actually, some of these fermions would plausibly get masses within the LHC range. If they are taken to be heavy quarks and leptons, in (bi)-fundamental representations of the standard model symmetries, their mixings with the light ones are strongly constrained to be very small by electroweak precision data. The alternative chosen here is to exactly forbid such mixings by breaking of flavour symmetries into an exact discrete symmetry, the so-called proton-hexality, primarily suggested to avoid proton decay. As a consequence of the large value needed for the flavour breaking scale, those heavy particles are long-lived and rather appropriate for the current and future searches at the LHC for quasi-stable hadrons and leptons. In fact, the LHC experiments have already started to look for them.

Automatisierte Berechnung von Feynman-Graphen

Die Berechnung von experimentell überprüfbaren Vorhersagen aus dem Standardmodell mit Hilfe störungstheoretischer Methoden ist schwierig. Die Herausforderungen liegen in der Berechnung immer komplizierterer Feynman-Integrale und dem zunehmenden Umfang der Rechnungen für Streuprozesse mit vielen Teilchen. Neue mathematische Methoden müssen daher entwickelt und die zunehmende Komplexität durch eine Automatisierung der Berechnungen gezähmt werden. In Kapitel 2 wird eine kurze Einführung in diese Thematik gegeben. Die nachfolgenden Kapitel sind dann einzelnen Beiträgen zur Lösung dieser Probleme gewidmet. In Kapitel 3 stellen wir ein Projekt vor, das für die Analysen der LHC-Daten wichtig sein wird. Ziel des Projekts ist die Berechnung von Einschleifen-Korrekturen zu Prozessen mit vielen Teilchen im Endzustand. Das numerische Verfahren wird dargestellt und erklärt. Es verwendet Helizitätsspinoren und darauf aufbauend eine neue Tensorreduktionsmethode, die Probleme mit inversen Gram-Determinanten weitgehend vermeidet. Es wurde ein Computerprogramm entwickelt, das die Berechnungen automatisiert ausführen kann. Die Implementierung wird beschrieben und Details über die Optimierung und Verifizierung präsentiert. Mit analytischen Methoden beschäftigt sich das vierte Kapitel. Darin wird das xloopsnosp-Projekt vorgestellt, das verschiedene Feynman-Integrale mit beliebigen Massen und Impulskonfigurationen analytisch berechnen kann. Die wesentlichen mathematischen Methoden, die xloops zur Lösung der Integrale verwendet, werden erklärt. Zwei Ideen für neue Berechnungsverfahren werden präsentiert, die sich mit diesen Methoden realisieren lassen. Das ist zum einen die einheitliche Berechnung von Einschleifen-N-Punkt-Integralen, und zum anderen die automatisierte Reihenentwicklung von Integrallösungen in höhere Potenzen des dimensionalen Regularisierungsparameters $epsilon$. Zum letzteren Verfahren werden erste Ergebnisse vorgestellt. Die Nützlichkeit der automatisierten Reihenentwicklung aus Kapitel 4 hängt von der numerischen Auswertbarkeit der Entwicklungskoeffizienten ab. Die Koeffizienten sind im allgemeinen Multiple Polylogarithmen. In Kapitel 5 wird ein Verfahren für deren numerische Auswertung vorgestellt. Dieses neue Verfahren für Multiple Polylogarithmen wurde zusammen mit bekannten Verfahren für andere Polylogarithmus-Funktionen als Bestandteil der CC-Bibliothek ginac implementiert.

Improved bounds on the radius and curvature of the K pi scalar form factor and implications to low-energy theorems

We obtain stringent bounds in the < r(2)>(K pi)(S)-c plane where these are the scalar radius and the curvature parameters of the scalar K pi form factor, respectively, using analyticity and dispersion relation constraints, the knowledge of the form factor from the well-known Callan-Treiman point m(K)(2)-m(pi)(2), as well as at m(pi)(2)-m(K)(2), which we call the second Callan-Treiman point. The central values of these parameters from a recent determination are accomodated in the allowed region provided the higher loop corrections to the value of th form factor at the second Callan-Treiman point reduce the one-loop result by about 3% with F-K/F-pi = 1.21. Such a variation in magnitude at the second Callan-Treiman point yields 0.12 fm(2) less than or similar to < r(2)>(K pi)(S) less than or similar to 0.21 fm(2) and 0.56 GeV-4 less than or similar to c less than or similar to 1.47 GeV-4 and a strong correlation between them. A smaller value of F-K/F-pi shifts both bounds to lower values.

Perturbative corrections for staggered four-fermion operators

We present results for one-loop matching coefficients between continuum four-fermion operators, defined in the Naive Dimensional Regularization scheme, and staggered fermion operators of various types. We calculate diagrams involving gluon exchange between quark fines, and ''penguin'' diagrams containing quark loops. For the former we use Landau-gauge operators, with and without O(a) improvement, and including the tadpole improvement suggested by Lepage and Mackenzie. For the latter we use gauge-invariant operators. Combined with existing results for two-loop anomalous dimension matrices and one-loop matching coefficients, our results allow a lattice calculation of the amplitudes for KKBAR mixing and K --> pipi decays with all corrections of O(g2) included. We also discuss the mixing of DELTAS = 1 operators with lower dimension operators, and show that, with staggered fermions, only a single lower dimension operator need be removed by non-perturbative subtraction.

Structure constants of beta deformed super Yang-Mills

We study the structure constants of the N = 1 beta deformed theory perturbatively and at strong coupling. We show that the planar one loop corrections to the structure constants of single trace gauge invariant operators in the scalar sector is determined by the anomalous dimension Hamiltonian. This result implies that 3 point functions of the chiral primaries of the theory do not receive corrections at one loop. We then study the structure constants at strong coupling using the Lunin-Maldacena geometry. We explicitly construct the supergravity mode dual to the chiral primary with three equal U(1) R-charges in the Lunin-Maldacena geometry. We show that the 3 point function of this supergravity mode with semi-classical states representing two other similar chiral primary states but with large U(1) charges to be independent of the beta deformation and identical to that found in the AdS(5) x S-5 geometry. This together with the one-loop result indicate that these structure constants are protected by a non-renormalization theorem. We also show that three point function of U(1) R-currents with classical massive strings is proportional to the R-charge carried by the string solution. This is in accordance with the prediction of the R-symmetry Ward identity.

Different patterns of uptake and depuration of cadmium by periphyton community and a grazer species (Physa sp.): A mesocosm evalution

Widespread pollution by heavy metals generated by various industries has serious adverse effects on human health and the environment. Cadmium is a heavy metal recognised as one of the most hazardous environmental pollutants. It is a non-essential and non-beneficial element to organisms, causing toxicity and other deleterious effects on various components of the aquatic environment. The ability of algal periphyton to concentrate cadmium from fresh water is well known. Moreover, periphyton communities are able to accumulate large amounts of cadmium despite its low concentration in fresh water. Many researchers use algal periphyton as an indicator of water quality in aquatic environments. In the present study, the authors ask two basic questions: Does cadmium accumulate along a food chain consisting of the periphyton community and a grazer species (Physa sp.) under semi-natural conditions provided by artificial streams? If not, which one can better indicate the water quality?

Relativistic quark models and the current algebra

In this thesis we are concerned with finding representations of the algebra of SU(3) vector and axial-vector charge densities at infinite momentum (the "current algebra") to describe the mesons, idealizing the real continua of multiparticle states as a series of discrete resonances of zero width. Such representations would describe the masses and quantum numbers of the mesons, the shapes of their Regge trajectories, their electromagnetic and weak form factors, and (approximately, through the PCAC hypothesis) pion emission or absorption amplitudes.

We assume that the mesons have internal degrees of freedom equivalent to being made of two quarks (one an antiquark) and look for models in which the mass is SU(3)-independent and the current is a sum of contributions from the individual quarks. Requiring that the current algebra, as well as conditions of relativistic invariance, be satisfied turns out to be very restrictive, and, in fact, no model has been found which satisfies all requirements and gives a reasonable mass spectrum. We show that using more general mass and current operators but keeping the same internal degrees of freedom will not make the problem any more solvable. In particular, in order for any two-quark solution to exist it must be possible to solve the "factorized SU(2) problem," in which the currents are isospin currents and are carried by only one of the component quarks (as in the K meson and its excited states).

In the free-quark model the currents at infinite momentum are found using a manifestly covariant formalism and are shown to satisfy the current algebra, but the mass spectrum is unrealistic. We then consider a pair of quarks bound by a potential, finding the current as a power series in 1/m where m is the quark mass. Here it is found impossible to satisfy the algebra and relativistic invariance with the type of potential tried, because the current contributions from the two quarks do not commute with each other to order 1/m³. However, it may be possible to solve the factorized SU(2) problem with this model.

The factorized problem can be solved exactly in the case where all mesons have the same mass, using a covariant formulation in terms of an internal Lorentz group. For a more realistic, nondegenerate mass there is difficulty in covariantly solving even the factorized problem; one model is described which almost works but appears to require particles of spacelike 4-momentum, which seem unphysical.

Although the search for a completely satisfactory model has been unsuccessful, the techniques used here might eventually reveal a working model. There is also a possibility of satisfying a weaker form of the current algebra with existing models.

Accumulation of Heavy Metals in Franciscanas from Buenos Aires Province, Argentina

Marine mammals accumulate heavy metals in their tissues at different concentrations according to trophic levels and environmental conditions. The franciscana (Pontoporia blainvillei) is a small coastal species inhabiting the marine and estuarine areas of the Southwestern Atlantic Ocean. Its diet includes numerous species of small fish, squid and crustaceans. The aims of this study were to (i) assess the heavy metal concentration and burden distribution in different franciscana age classes and sex, and to (ii) evaluate both the accumulation processes and the transplacental transference of zinc, cadmium, copper and total mercury. Heavy metal concentrations (wet weight) were determined in eighteen dolphins by Atomic Absorption Spectrophotometry (AAS), by the cold vapour technique (mercury) or with air/acetylene flame (cadmium, zinc and copper). Liver showed the highest concentrations of mercury (max. 8.8 mg/g), zinc (max. 29.7 mg/g) and copper (max. 19.0 mg/g), whereas the highest cadmium concentrations (max. 6.7 mg/g) were found in kidney. Adults contained the highest concentrations for all heavy metals, followed by juveniles and calves in decreasing order, suggesting an age-related accumulation. No differences (p<0.05) were found between sexes within each age class. Organ burden distribution followed the same pattern for all metals and age classes: liver tissues contained maximum burdens. Mercury concentrations were higher than those of cadmium in both foetuses and newborns; and neither metal could be detected in the foetus. The analysed data suggested differences in the placental transference between metals, being significant for mercury and almost null in the case of cadmium. We can conclude that franciscana accumulates heavy metals and, due to its coastal distribution, it may be considered as a biomonitor of its environment. SPANISH: Los mamíferos marinos acumulan metales pesados en sus tejidos cuyas concentraciones están en relación con su nivel trófico y las condiciones ambientales. La franciscana (Pontoporia blainvillei) es una especie costera que habita áreas marinas y estuariales en el Atlántico Sudoccidental. Su dieta está constituída por peces, como item alimentario principal, calamares y crustáceos. El objetivo del presente trabajo es estudiar la distribución de metales pesados en diferentes clases de edad y en ambos sexos, evaluando procesos de acumulación y cargas de cadmio, mercurio total, cinc y cobre. Las concentraciones de metales pesados (en peso húmedo) fueron determinadas en dieciocho delfines por Espectrofotometría de Absorción Atómica (EAA), usando la técnica de vapor frío (mercurio) o llama de aire/acetileno (cadmio, cinc y cobre). El hígado presentó las concentraciones más altas de mercurio (máx. 8,8 mg/g), cinc (máx. 29,7 mg/g) y cobre (máx. 19,0 mg/g), mientras que las más altas de cadmio (máx. 6,7 mg/g) fueron encontradas en el riñón. Los adultos presentaron los niveles más altos, presentando los juveniles y cachorros concentraciones menores, lo cual sugirió una acumulación con la edad. No se encontraron diferencias significativas (p < 0,05) entre sexos dentro de cada clase de edad. Las cargas de metales pesados en los órganos presentaron la misma disribución para todos los metales y clases de edad. Los valores más altos fueron encontrados en el hígado, incluyendo los correspondientes a cadmio. Las concentraciones de mercurio y cadmio fueron no detectables en el feto, mientras que las de mercurio fueron superiores a las de cadmio en los cachorros. Los datos encontrados en el feto sugieren una transferencia nula a través de la placenta. Podemos concluir que P.blainvillei acumula metales pesados en sus tejidos y debido a su distribución costera, esta especie puede ser considerada como un biomonitor de su ambiente.

CHANNELING ALIGNMENT FOR EPITAXIAL LIGHT-MASS FILM ON HEAVY-MASS SUBSTRATE

A simple procedure for obtaining a background-free backscattering spectrum of a light-mass film on a heavy-mass substrate by a normal incidence/grazing exit geometry has been described. Using this method such films can be aligned rapidly and accurately, and the impurity or defect information on the films can be obtained without need for realignment. Example is given from MeV Li-3+ analysis of a deposited film of Si on a single crystal substrate of yttria-stabilized, cubic zirconia.

EC/beta(+) decay of six medium-heavy nuclei

Previous experimental results of (EC+beta(+)) decay for the medium-heavy nuclei reported by our group since 1996, including Er-153, Yb-157, Fr-209, Ce-128, Ce-130, and Pr-128 have been briefly summarized. The observed low-lying states in their daughter nuclei have been reviewed in a systematic way and compared with different model calculations. Finally, some questions have been put forward for further study and discussion.

Time required for the restoration of normal heavy exercise Vo(2) kinetics following prior heavy exercise

Burnley, M., Doust, J. and Jones, A. (2006). Time required for the restoration of normal heavy exercise Vo(2) kinetics following prior heavy exercise. Journal of Applied Physiology. 101(5), pp.1320-1327 RAE2008

Laser-driven three-stage heavy-ion acceleration from relativistic laser-plasma interaction

A three-stage heavy ion acceleration scheme for generation of high-energy quasimonoenergetic heavy ion beams is investigated using two-dimensional particle-in-cell simulation and analytical modeling. The scheme is based on the interaction of an intense linearly polarized laser pulse with a compound two-layer target (a front heavy ion layer + a second light ion layer). We identify that, under appropriate conditions, the heavy ions preaccelerated by a two-stage acceleration process in the front layer can be injected into the light ion shock wave in the second layer for a further third-stage acceleration. These injected heavy ions are not influenced by the screening effect from the light ions, and an isolated high-energy heavy ion beam with relatively low-energy spread is thus formed. Two-dimensional particle-in-cell simulations show that ∼100MeV/u quasimonoenergetic Fe24+ beams can be obtained by linearly polarized laser pulses at intensities of 1.1×1021W/cm². 

Studies on Pseudoscalar Meson Bound States and Semileptonic Decays in a Relativistic Potential Model

In this thesis quark-antiquark bound states are considered using a relativistic two-body equation for Dirac particles. The mass spectrum of mesons includes bound states involving two heavy quarks or one heavy and one light quark. In order to analyse these states within a unified formalism, it is desirable to have a two-fermion equation that limits to one body Dirac equation with a static interaction for the light quark when the other particle's mass tends to infinity. A suitable two-body equation has been developed by Mandelzweig and Wallace. This equation is solved in momentum space and is used to describe the complete spectrum of mesons. The potential used in this work contains a short range one-gluon exchange interaction and a long range linear confining and constant potential terms. This model is used to investigate the decay processes of heavy mesons. Semileptonic decays are more tractable since there is no final state interactions between the leptons and hadrons that would otherwise complicate the situation. Studies on B and D meson decays are helpful to understand the nonperturbative strong interactions of heavy mesons, which in turn is useful to extract the details of weak interaction process. Calculation of form factors of these semileptonic decays of pseudo scalar mesons are also presented.