Lorentz symmetry breaking in the noncommutative Wess-Zumino model: One loop corrections

In this paper we deal with the issue of Lorentz symmetry breaking in quantum field theories formulated in a non-commutative space-time. We show that, unlike in some recente analysis of quantum gravity effects, supersymmetry does not protect the theory from the large Lorentz violating effects arising from the loop corrections. We take advantage of the non-commutative Wess-Zumino model to illustrate this point.Comment: 9 pages, revtex4. Corrected references. Version published in PR

The Noncommutative Supersymmetric Nonlinear Sigma Model

We show that the noncommutativity of space-time destroys the renormalizability of the 1/N expansion of the O(N) Gross-Neveu model. A similar statement holds for the noncommutative nonlinear sigma model. However, we show that, up to the subleading order in 1/N expansion, the noncommutative supersymmetric O(N) nonlinear sigma model becomes renormalizable in D=3. We also show that dynamical mass generation is restored and there is no catastrophic UV/IR mixing. Unlike the commutative case, we find that the Lagrange multiplier fields, which enforce the supersymmetric constraints, are also renormalized. For D=2 the divergence of the four point function of the basic scalar field, which in D=3 is absent, cannot be eliminated by means of a counterterm having the structure of a Moyal product.Comment: 15 pages, 7 figures, revtex, minor modifications in the text, references adde

The three-dimensional noncommutative Gross-Neveu model

This work is dedicated to the study of the noncommutative Gross-Neveu model. As it is known, in the canonical Weyl-Moyal approach the model is inconsistent, basically due to the separation of the amplitudes into planar and nonplanar parts. We prove that if instead a coherent basis representation is used, the model becomes renormalizable and free of the aforementioned difficulty. We also show that, although the coherent states procedure breaks Lorentz symmetry in odd dimensions, in the Gross-Neveu model this breaking can be kept under control by assuming the noncommutativity parameters to be small enough. We also make some remarks on some ordering prescriptions used in the literature.Comment: 10 pages, IOP article style; v3: revised version, accepted for publication in J. Phys.

The Link between General Relativity and Shape Dynamics

We show that one can construct two equivalent gauge theories from a linking theory and give a general construction principle for linking theories which we use to construct a linking theory that proves the equivalence of General Relativity and Shape Dynamics, a theory with fixed foliation but spatial conformal invariance. This streamlines the rather complicated construction of this equivalence performed previously. We use this streamlined argument to extend the result to General Relativity with asymptotically flat boundary conditions. The improved understanding of linking theories naturally leads to the Lagrangian formulation of Shape Dynamics, which allows us to partially relate the degrees of freedom.Comment: 19 pages, LaTeX, no figure

Supergiant Barocaloric Effects in Acetoxy Silicone Rubber over a Wide Temperature Range: Great Potential for Solid-state Cooling

Solid-state cooling based on caloric effects is considered a viable alternative to replace the conventional vapor-compression refrigeration systems. Regarding barocaloric materials, recent results show that elastomers are promising candidates for cooling applications around room-temperature. In the present paper, we report supergiant barocaloric effects observed in acetoxy silicone rubber - a very popular, low-cost and environmentally friendly elastomer. Huge values of adiabatic temperature change and reversible isothermal entropy change were obtained upon moderate applied pressures and relatively low strains. These huge barocaloric changes are associated both to the polymer chains rearrangements induced by confined compression and to the first-order structural transition. The results are comparable to the best barocaloric materials reported so far, opening encouraging prospects for the application of elastomers in near future solid-state cooling devices.Comment: 19 pages, 7 figures, 2 table

On the finiteness of the noncommutative supersymmetric Maxwell-Chern-Simons theory

Within the superfield approach, we prove the absence of UV/IR mixing in the three-dimensional noncommutative supersymmetric Maxwell-Chern-Simons theory at any loop order and demonstrate its finiteness in one, three and higher loop orders.Comment: 9 pages, 2 figures, revtex

Influência de cinco tipos de porta-enxerto na produção e nas características dos frutos da cultivar Thompson Seedless no Submédio São Francisco.

O presente trabalho teve como objetivo avaliar aspectos relacionados à produção e ao crescimento vegetativo da cultivar Thompson Seedless, bem como características e composição química dos frutos, sob a influência de cinco diferentes porta-enxertos (IAC 766, Couderc 1613, Harmony, Paulsen 1103 e 420A), nas condições do Vale do São Francisco, a fim de recomendar uma cultivar porta-enxerto que tenha afinidade com a variedade copa estudada

A 27-year review of mergers and acquisitions research in 27 leading management journals

This study contributes to the existing body of knowledge on mergers and acquisitions (M&As) by providing a systematic review of over 500 academic articles across 27 management journals over a 27-year time frame. There appears to be a mixture of empirical and conceptual articles, with a larger proportion being empirical but an increasing number leaning towards a conceptual nature. Our findings show that most studies follow a quantitative approach and use large samples, mostly originating from existing databases. There is an emergence of thematic areas related to the strategic factors influencing M&As, but with the human dimension, gaining increasing attention over time.authorsversionpublishe

Computing confidence intervals for output oriented DEA models: an application to agricultural research in Brazil.

We define and model the research production at Embrapa, the major Brazilian institution responsable for applied agricultural research. The main theoretical framework is Data Envelopment Analysis - DEA. We explore the economic interpretation and the statistical properties of these models to compute confidence intervals for output oriented efficiency measurements, based on a parametric flexible model, defined by the truncated normal distribution. These results provide a better insight on the efficiency classification and allow comparison among the DMUs involved int ehe evaluation process taking into account inefficiency random variation

Radiative Corrections to the Aharonov-Bohm Scattering

We consider the scattering of relativistic electrons from a thin magnetic flux tube and perturbatively calculate the order $\alpha$, radiative correction, to the first order Born approximation. We show also that the second order Born amplitude vanishes, and obtain a finite inclusive cross section for the one-body scattering which incorporates soft photon bremsstrahlung effects. Moreover, we determine the radiatively corrected Aharonov-Bohm potential and, in particular, verify that an induced magnetic field is generated outside of the flux tube.Comment: 14 pages, revtex, 3 figure