Matter Fields in the Lagrangian Loop Representation: Scalar QED

We present the extension of the Lagrangian loop gauge invariant representation in such a way to include matter fields. The partition function of lattice compact U(1)-Higgs model is expressed as a sum over closed as much as open surfaces. We have simulated numerically the loop action equivalent to the Villain form of the action and mapped out the beta-gamma phase diagram of this model.Comment: 10 pages, LaTe

On the Path Integral Loop Representation of (2+1) Lattice Non-Abelian Theory

A gauge invariant Hamiltonian representation for SU(2) in terms of a spin network basis is introduced. The vectors of the spin network basis are independent and the electric part of the Hamiltonian is diagonal in this representation. The corresponding path integral for SU(2) lattice gauge theory is expressed as a sum over colored surfaces, i.e. only involving the $j_p$ attached to the lattice plaquettes. This surfaces may be interpreted as the world sheets of the spin networks In 2+1 dimensions, this can be accomplished by working in a lattice dual to a tetrahedral lattice constructed on a face centered cubic Bravais lattice. On such a lattice, the integral of gauge variables over boundaries or singular lines -- which now always bound three coloured surfaces -- only contributes when four singular lines intersect at one vertex and can be explicitly computed producing a 6-j or Racah symbol. We performed a strong coupling expansion for the free energy. The convergence of the series expansions is quite different from the series expansions which were performed in ordinary cubic lattices. In the case of ordinary cubic lattices the strong coupling expansions up to the considered truncation number of plaquettes have the great majority of their coefficients positive, while in our case we have almost equal number of contributions with both signs. Finally, it is discused the connection in the naive coupling limit between this action and that of the B-F topological field theory and also with the pure gravity action.Comment: 16 pages, REVTEX, 8 Encapsulated Postscript figures using psfig, minor changes in text and reference

The basis of the physical Hilbert space of lattice gauge theories

Non-linear Fourier analysis on compact groups is used to construct an orthonormal basis of the physical (gauge invariant) Hilbert space of Hamiltonian lattice gauge theories. In particular, the matrix elements of the Hamiltonian operator involved are explicitly computed. Finally, some applications and possible developments of the formalism are discussed.Comment: 14 pages, LaTeX (Using amsmath

En memoria de Miguel Fisac

Miguel Fisac was a pithy person, sculpted from a single stone. There is no point in distinguishing parts where there were none, but it is worthwhile to attempt to analyze different points of view on the activity of a monolithic personality. Architects, designers, contractors, inventors, troublemakers and theologians among others could rightly claim him as one of their own. Given the exclusive attitudes adopted by most trades, however, they would be more likely to define him as “an outsider who did things”. At the age of nearly 93, in his last project, which he left in the design phase, he was planning to use the “construction system with precast members combining architecture and strength“ that he had patented years before in Spain and 21 other countries, the United States and Russia among them.Miguel Fisac era un personaje escueto, de una sola pieza, no cabe distinguir partes donde no las hay, pero si tratar de analizar desde distintos puntos de vista la actividad de una personalidad monolítica; arquitectos, diseñadores, constructores, inventores, polemistas y teólogos entre otros podrían con facilidad reivindicar su figura como uno de los suyos, aunque dado el afán de exclusividad que caracteriza a todo gremio, es más probable que lo calificaran como “alguien, de fuera, que ha hecho cosas”. Al filo de los 93 años, en su última obra, aún en proyecto, iba a emplear un “sistema de construcción mediante elementos prefabricados con funciones arquitectónicas y resistentes conjuntas” patentado por él hace años en España y en otros 21 países, entre ellos, Estados Unidos y Rusia

Continuum spin foam model for 3d gravity

An example illustrating a continuum spin foam framework is presented. This covariant framework induces the kinematics of canonical loop quantization, and its dynamics is generated by a {\em renormalized} sum over colored polyhedra. Physically the example corresponds to 3d gravity with cosmological constant. Starting from a kinematical structure that accommodates local degrees of freedom and does not involve the choice of any background structure (e. g. triangulation), the dynamics reduces the field theory to have only global degrees of freedom. The result is {\em projectively} equivalent to the Turaev-Viro model.Comment: 12 pages, 3 figure

Classical Loop Actions of Gauge Theories

Since the first attempts to quantize Gauge Theories and Gravity in the loop representation, the problem of the determination of the corresponding classical actions has been raised. Here we propose a general procedure to determine these actions and we explicitly apply it in the case of electromagnetism. Going to the lattice we show that the electromagnetic action in terms of loops is equivalent to the Wilson action, allowing to do Montecarlo calculations in a gauge invariant way. In the continuum these actions need to be regularized and they are the natural candidates to describe the theory in a ``confining phase''.Comment: LaTeX 14 page

Mathematical modeling and simulation of volatile reduced sulfur compounds oxidation in biotrickling filters

[Abstract] The odour generated by industrial gaseous emissions causing nuisances generally is due to the presence of volatile reduced sulfur compounds (VRSC) Although a number of microorganisms are known for degrading VRSC, the treatment of a mixture of reduced sulfur compounds remains challenging for several reasons. To resolve these problems two-stage systems have been proposed, in the first reactor H2S is bio-oxidized and in the second the rest of the VRSC mixture, avoiding the inhibition effects of H2S over the bio-oxidation of these compounds. In the systems described the complete oxidation of H2S must be performed in the first reactor, if some H2S pass though out the first reactor it would have an effect on the bio-oxidation of the other VRSC present in the mixture in the second bioreactor. This situation was modelled and simulated, and is presented in this article. The bio-oxidation of H2S and DMS in a biotrickling filter is described through a model of the mass transfer and chemical reaction processes. The biotrickling filter is modeled as a fixed bed of packing material which supports the growth of micro-organisms as biofilms. When air flows in the bed, H2S and DMS are continuously transferred from the gas phase to the biofilm, where they diffuse and are oxidized by aerobic microbial activity. A summary of the equations, results of the simulation and sensibility to the inhibition constants are reported

Adaptation of a flocculent Saccharomyces cerevisiae strain to lignocellulosic inhibitors by cell recycle batch fermentation

The ethanol production from lignocellulosic feedstocks is considered a promising strategy to increase global production of biofuels without impacting food supplies. However, some compounds released during the hydrolysis of lignocellulosic materials are toxic for the microbial metabolism, causing low ethanol yield and productivity during the fermentation. As an attempt to overcome this problem, the present study evaluated the adaptation of a flocculent strain of Saccharomyces cerevisiae (NRRL Y-265) to several inhibitory compounds usually found in lignocellulosic hydrolysates (acetic acid, furfural, hydroxymethylfurfural, vanillin, syringaldehyde, and hydroxybenzoic acid), aiming to minimize their negative effects on yeast metabolism, maximizing the ethanol production as a consequence. Cell recycle batch fermentation (CRBF) was performed during 39 consecutive days, using five different fermentation media with sequential increase in the concentration of inhibitory compounds, simulating the composition of lignocellulosic hydrolysates. This strategy allowed obtaining a yeast strain with increased ethanol volumetric productivity and growth rate (10% and 70% respectively, over parent strain) able to produce ethanol with better results when cultivated in glucose-supplemented steam-exploded eucalyptus hydrolysate.This work was funded by CONICYT-MINERGIA, Chile (Programa Pasantias en Extranjero, Convocatoria 2010) and by Innova Chile Project 208-7320 Technological Consortium Bioenercel S.A