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

Mixing in convective thermal fluxes in unsteady nonhomogeneous flows generating complex three dimensional vorticity patterns

Diffusion and scaling of the velocity and vorticity in a thermoelectric driven heating and cooling experimental device is presented in order to map the different patterns and transitions between two and three dimensional convection in an enclosure with complex driven flows. The size of the water tank is of 0.2 x 0.2 x 0.1 m and the heat sources or sinks can be regulated both in power and sign [1-3]. The thermal convective driven flows are generated by means of Peltier effects in 4 wall extended positions of 0.05 x 0.05 cm each. The parameter range of convective cell array varies strongly with the Topology of the boundary conditions. Side heat and momentum fluxes are a function of Rayleigh, Peclet and Nusselt numbers, [4-6] Visualizations are performed by PIV, Particle tracking and shadowgraph. The structure of the flow is shown by setting up a convective flow generated by buoyant heat fluxes. The experiments described here investigate high Prandtl number mixing using brine and fresh water in order to form a density interface and low Prandtl number mixing with temperature gradients. The evolution of the mixing fronts are compared and the topological characteristics of the merging of the convective structures are examined for different configurations. Based on two dimensional Vorticity spectral analysis, new techniques can be very useful to determine the evolution of scales considering the multi-fractal structure of the convective flows.Peer ReviewedPostprint (published version

TransverseDiff gravity is to scalar-tensor as unimodular gravity is to General Relativity

Transverse Diffeomorphism (TDiff) theories are well-motivated theories of gravity from the quantum perspective, which are based upon a gauge symmetry principle. The main contribution of this work is to firmly establish a correspondence between TransverseDiff and the better-known scalar-tensor gravity --- in its more general form ---, a relation which is completely analogous to that between unimodular gravity and General Relativity. We then comment on observational aspects of TDiff. In connection with this proof, we derive a very general rule that determines under what conditions the procedure of fixing a gauge symmetry can be equivalently applied before the variational principle leading to the equations of motion, as opposed to the standard procedure, which takes place afterwards; this rule applies to gauge-fixing terms without derivatives.Comment: 10 pages; amsart style; v3: version as appeared in JCAP, redaction improve

Augmented Reality Based on SLAM to Assess Spatial Short-Term Memory

Spatial short-term memory is defined as the limited ability of people to retain and remember the location of elements for short periods of time. In this paper, we present the first AR app based on SLAM (Simultaneous Localization and Mapping) to assess spatial short-term memory. A total of 55 participants were involved in a study for remembering the real place where four virtual objects were located in the real environment. The participants were divided into two groups: the ARGroup (the participants learned the location of the virtual objects in the real environment in an adaptation phase using AR) and the NoARGroup (the participants learned the location of the objects by looking at photographs). The results indicated that the performance outcomes in remembering objects and their location for the participants in the ARGroup were statistically significantly greater than those obtained by the participants in the NoARGroup. From this result and our observations, we can conclude that touring the augmented environment helped the participants to better remember the location of virtual objects added to the real scene compared to looking at photographs of the environment. Furthermore, statistically significant differences were not found in relation to gender or age. Finally, our app has several advantages: 1) Our app works in any environment and does not require adding real elements to the environment; 2) the evaluators can select any real environment and place the virtual elements where they want and even change them between sessions; and 3) our app could work similar to the way spatial memory does in everyday life

Osteogenic effects of simvastatin-loaded mesoporous titania thin films

The use of statins in the field of bone regeneration is under current investigation due to the existing demand for non-toxic anabolic agents capable of enhancing bone formation in cases of substantial loss. Simvastatin, a coenzyme currently prescribed in clinics to inhibit cholesterol biosynthesis, has been proven to promote osteogenic differentiation by stimulating bone formation and inhibiting osteoclasts activity. We present the loading of simvastatin in mesoporous TiO2 thin films toward combining the pro-osteogenic properties of this molecule with the demonstrated bioactivity of titania. TiO2 thin films processing and characterization were carried out, as well as evaluation of MC3T3-E1 pre-osteoblasts viability when directly incubated with different concentrations of simvastatin, followed by the analysis of osteogenic activity promoted by simvastatin upon loading in the thin films. The accessible porosity of 36% quantified on the 95 ± 5 nm thick mesoporous thin films, together with pore diameters of 5.5 nm, necks between pores of 2.8 nm and interpore distances of 12 ± 2 nm allow the loading of the simvastatin molecule, as confirmed by FTIR spectroscopy. Simvastatin was found to promote MC3T3-E1 pre-osteoblasts viability at concentrations ≤0.01 g l−1, with a cytotoxicity threshold of 0.05 g l−1. We additionally found that film loadings with 0.001 g l−1 simvastatin promotes statistically higher MC3T3-E1 pre-osteoblast proliferation whereas a higher concentration of 0.01 g l−1 leads to statistically higher osteogenic activity (ALP synthesis), after 21 days of incubation, as compared to unloaded films. These results demonstrate the potential of simvastatin local administration based on bioactive mesoporous thin films to promote pro-osteogenic properties. By focusing this strategy on the coating of metallic prostheses, the supply of simvastatin to the target tissue can be favored and risks of systemic side effects will be reduced while enhancing the osteointegration of the implants.Fil: Lopez Alvarez, Miriam. Universidad de Vigo; EspañaFil: López Puente, Vanesa. Universidad de Vigo; EspañaFil: Rodriguez Valencia, Cosme. Universidad de Vigo; EspañaFil: Angelome, Paula Cecilia. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Liz Marzan, Luis M. Ikerbasque; EspañaFil: Serra, Julia. Universidad de Vigo; EspañaFil: Pastoriza Santos, Isabel. Universidad de Vigo; EspañaFil: Gonzalez, Pio. Universidad de Vigo; Españ