Non-analyticities in three-dimensional gauge theories

Quantum fluctuations generate in three-dimensional gauge theories not only radiative corrections to the Chern-Simons coupling but also non-analytic terms in the effective action. We review the role of those terms in gauge theories with massless fermions and Chern-Simons theories. The explicit form of non-analytic terms turns out to be dependent on the regularization scheme and in consequence the very existence of phenomena like parity and framing anomalies becomes regularization dependent. In particular we find regularization regimes where both anomalies are absent. Due to the presence of non-analytic terms the effective action becomes not only discontinuous but also singular for some background gauge fields which include sphalerons. The appearence of this type of singularities is linked to the existence of nodal configurations in physical states and tunneling suppression at some classical field configurations. In the topological field theory the number of physical states may also become regularization dependent. Another consequence of the peculiar behaviour of three-dimensional theories under parity odd regularizations is the existence of a simple mechanism of generation of a mass gap in pure Yang-Mills theory by a suitable choice of regularization scheme. The generic value of this mass does agree with the values obtained in Hamiltonian and numerical analysis. Finally, the existence of different regularization regimes unveils the difficulties of establishing a Zamolodchikov c-theorem for three-dimensional field theories in terms of the induced gravitational Chern-Simons couplings.Comment: 21 pages; Contribution to Ian Kogan Memorial Collection, ``From Fields to Strings: Circumnavigating Theoretical Physics'

Observational Constraints on Transverse Gravity: a Generalization of Unimodular Gravity

We explore the hypothesis that the set of symmetries enjoyed by the theory that describes gravity is not the full group of diffeomorphisms Diff(M), as in General Relativity, but a maximal subgroup of it, TransverseDiff(M), with its elements having a jacobian equal to unity; at the infinitesimal level, the parameter describing the coordinate change, xi^mu (x), is transverse, i.e., partial_mu(xi^mu)=0. Incidentally, this is the smaller symmetry one needs to propagate consistently a graviton, which is a great theoretical motivation for considering these theories. Also, the determinant of the metric, g, behaves as a "transverse scalar", so that these theories can be seen as a generalization of the better-known unimodular gravity. We present our results on the observational constraints on transverse gravity, in close relation with the claim of equivalence with general scalar-tensor theory. We also comment on the structure of the divergences of the quantum theory to the one-loop order.Comment: Prepared for the First Mediterranean Conference on Classical and Quantum Gravity, MCCQG, Kolymbari (Crete, Greece), 14-18 September, 2009; also, ERE2009: Gravitation in the Large, Bilbao (Spain), 7-11 September, 200

Treatment of dogs with compensated myxomatous mitral valve disease with spironolactone-a pilot study

Spironolactone improves outcome in dogs with advanced myxomatous mitral valve disease (MMVD). Its efficacy in preclinical MMVD is unknown. The hypothesis was the administration of spironolactone to dogs with compensated MMVD demonstrating risk factors for poorer prognosis will decrease the rate of disease progression. The aim was to provide pilot data to evaluate preliminary effects and sample size calculation for a definitive clinical trial

Nanopore-based complete genome sequence of a Sri Lankan cassava mosaic virus (Geminivirus) strain from Thailand

Sri Lankan cassava mosaic virus is an emerging pathogen in Southeast Asia. Here, we report the complete genome of a Thai isolate obtained using Nanopore technology. The isolate was collected in 2019 from the northeastern province of Surin, soon after disease eradication was reported in the country

Els fars davanters a ull de càmara

La contínua innovació en els sistemes d'il·luminació dels automòbils comporta també una millora en els sistemes d'avaluació. Aquests estan basats en la comparació dinàmica, és a dir, que siguin els propis experts o usuaris qui comprovin la qualitat dels fars durant una sèrie de proves de conducció. L'inconvenient d'aquesta mena d'avaluació és que resulta força costós, i la capacitat de retenció visual a curt termini de les persones no assegura uns resultats definitius. Per això, el departament de Desenvolupament Elèctric, Il·luminació i Senyalització del Centre Tècnic de SEAT, a Martorell, i el Centre de Visió per Computador de la UAB han ideat un sistema de gravació, del que després es podran visionar els fotogrames i fer-ne la comparació. És necessari però, sincronització i alineació espacial entre els fotogrames per ajustar correctament els resultats a la realitat de la conducció.La continua innovación en los sistemas de iluminación de los automóviles comporta también una mejora en los sistemas de evaluación. Éstos están basados en la comparación dinámica, es decir, que sean los propios expertos o usuarios quienes comprueben la calidad de los faros durante una serie de pruebas de conducción. El inconveniente de este tipo de evaluación es que resulta bastante costoso, y la capacidad de retención visual a corto plazo de las personas no asegura unos resultados definitivos. Por eso, el departamento de Desarrollo Eléctrico, Iluminación y Señalización del Centro Técnico de SEAT, en Martorell, i el Centro de Visión por Computador de la UAB han ideado un sistema de grabación, del que después se podrán visionar los videos y realizar la comparación. Es necesario sin embargo, sincronización y alineación espacial entre los fotogramas para ajustar correctamente los resultados a la realidad de la conducción.Continuous innovation in headlamp systems also implies an improvement in how they are assessed. These assessment systems are based on dynamic comparison, i.e., experts or users themselves assess the quality of headlamps by means of different driving tests. The disadvantages of this type of assessment are the elevated cost and the fact that short-term visual retention does not guarantee definitive results. For this reason, the Department of Electrical, Lighting and Signal Development at SEAT's Technical Centre in Martorell, and Computer Vision Centre of UAB have created a recording system. The frames from these recordings will later be viewed and compared. However, first they will have to be spatially synchronised and aligned in order to adjust the results to real driving situations

Experimental aspects of SU(5)xU(1) supergravity

We study various aspects of $SU(5)\times U(1)$ supergravity as they relate to the experimental verification or falsification of this model. We consider two string-inspired, universal, one-parameter, no-scale soft-supersymmetry-breaking scenarios, driven by the $F$-terms of the moduli and dilaton fields. The model is described in terms of the supersymmetry mass scale (\ie, the chargino mass $m_{\chi^\pm_1}$), $\tan\beta$, and the top-quark mass. We first determine the combined effect on the parameter space of all presently available direct and indirect experimental constraints, including the LEP lower bounds on sparticle and Higgs-boson masses, the $b\to s\gamma$ rate, the anomalous magnetic moment of the muon, the high-precision electroweak parameters $\epsilon_1,\epsilon_b$ (which imply m_t\lsim180\GeV), and the muon fluxes in underground detectors (neutrino telescopes). For the still-allowed points in $(m_{\chi^\pm_1},\tan\beta)$ parameter space, we re-evaluate the experimental situation at the Tevatron, LEPII, and HERA. In the 1994 run, the Tevatron could probe chargino masses as high as 100 GeV. At LEPII the parameter space could be explored with probes of different resolutions: Higgs boson searches, selectron searches, and chargino searches. Moreover, for m_t\lsim150\GeV, these Higgs-boson searches could explore all of the allowed parameter space with \sqrt{s}\lsim210\GeV.Comment: latex, 36 pages, 25 figures (not included). Figures are available via anonymous ftp from hplaa02.cern.ch (/pub/lopez) as either 33 ps files (Easpects*.ps, 8.1MB) or one uuencoded file (AllFigures.uu, 3.7MB

Phase-stabilized, 1.5-W frequency comb at 2.8 to 4.8 micron

We present a high-power optical parametric oscillator-based frequency comb in the mid-infrared wavelength region using periodically poled lithium niobate. The system is synchronously pumped by a 10-W femtosecond Yb:fiber laser centered at 1.07 um and is singly resonant for the signal. The idler (signal) wavelength can be continuously tuned from 2.8 to 4.8 um (1.76 to 1.37 um) with a simultaneous bandwidth as high as 0.3 um and a maximum average idler output power of 1.50 W. We also demonstrate the performance of the stabilized comb by recording the heterodyne beat with a narrow-linewidth diode laser. This OPO is an ideal source for frequency comb spectroscopy in the mid-IR.Comment: 4 figure