Searcharxiv⌕ Search

arXiv subjects

A. J. da Silva

Publications and source records attributed to A. J. da Silva.

At least 37 records · Page 2Linked to original sources
arXiv2015

Lorentz breaking supersymmetry and Horava-Lifshitz-like models

We present a Lorentz-breaking supersymmetric algebra characterized by a critical exponent $z$. Such construction requires a non trivial modification of the supercharges and superderivatives. The improvement of renormalizability for supersymmetric scalar QED is shown and the Kählerian effective potentials are calculated in different cases. We also show how the theory flows naturally to the Lorentz symmetric case at low energies.

hep-th↗
arXiv2014

On the Horava-Lifshitz-like extensions of supersymmetric theories

Within the superfield approach, we formulate two different extensions of the Wess-Zumino model and super-QED with Horava-Lifshitz-like additive terms, discuss their quantum properties and calculate lower contributions to the effective action. In the case of the gauge theory, the one-loop effective potential turns out to be gauge independent.

hep-th↗
arXiv2014

Gravitational corrections to the scattering in a massless quantum electrodynamics

We discuss the role of gravitational corrections to the running of the electric charge through the evaluation of scattering amplitudes of charged particles in massless scalar electrodynamics. Computing the complete divergent part of the S-matrix amplitude for two distinct scattering processes, we show that quantum gravitational corrections do not alter the running behavior of the electric charge. Our result does not exclude the possibility that the presence of a second dimensional constant in the model (a cosmological constant or the presence of massive particles) could alter this behavior, as was proposed in earlier works.

hep-th↗
arXiv2014

On the generic higher-derivative N=2, d=3 gauge theory

We formulate a generic $\mathcal{N}=2$ three-dimensional superfield higher-derivative gauge theory coupled to the matter, which, in certain cases reduces to the $\mathcal{N}=2$ three-dimensional scalar super-QED, or supersymmetric Maxwell-Chern-Simons or Chern-Simons theories with matter. For this theory, we explicitly calculate the one-loop effective potential.

hep-th↗
arXiv2014

Braneworld solutions for F(R) models with non-constant curvature

This work deal with braneworld scenarios with generalized gravity. We investigate models where the potential of the scalar field is polynomial or nonpolynomial. We obtain exact and approximated solutions for the scalar field, warp factor and energy density, in the complex scenario with no restriction on the scalar curvature. In particular, we describe the case where the brane may split, engendering internal structure, with the splitting caused by the same parameter that controls deviation from standard gravity.

hep-th↗
arXiv2014

On the one-loop effective potential in the higher-derivative four-dimensional chiral superfield theory with a nonconventional kinetic term

We explicitly calculate the one-loop effective potential for a higher-derivative four-dimensional chiral superfield theory with a nonconventional kinetic term. We consider the cases of minimal and nonminimal general Lagrangians. In particular, we find that in the minimal case the divergent part of the one-loop effective potential vanishes by reason of the chirality.

hep-th↗
arXiv2013

Maximum likelihood q-estimator reveals nonextensivity regulated by extracellular potassium in the mammalian neuromuscular junction

Recently, we demonstrated the existence of nonextensivity in neuromuscular transmission [Phys. Rev. E 84, 041925 (2011)]. In the present letter, we propose a general criterion based on the q-calculus foundations and nonextensive statistics to estimate the values for both scale factor and q-index using the maximum likelihood q-estimation method (MLqE). We next applied our theoretical findings to electrophysiological recordings from neuromuscular junction (NMJ) where spontaneous miniature end plate potentials (MEPP) were analyzed. These calculations were performed in both normal and high extracellular potassium concentration, [K+]o. This protocol was assumed to test the validity of the q-index in electrophysiological conditions closely resembling physiological stimuli. Surprisingly, the analysis showed a significant difference between the q-index in high and normal [K+]o, where the magnitude of nonextensivity was increased. Our letter provides a general way to obtain the best q-index from the q-Gaussian distribution function. It also expands the validity of Tsallis statistics in a more realistic stimulus condition. Physical and physiological implications of these findings are discussed in detail.

physics.bio-ph↗
arXiv2013

Supersymmetry breaking in the three-dimensional nonlinear sigma model

In this work we discuss the phase structure of a deformed supersymmetric nonlinear sigma model in a three-dimensional space-time. The deformation is introduced by a term that breaks supersymmetry explicitly, through imposing a slightly different constraint to the fundamental superfields of the model. Using the tadpole method, we compute the effective potential at leading order in 1/N expansion. From the gap equations, i.e., conditions that minimize the effective potential, we observe that this model presents two phases as the ordinary model, with two remarkable differences: 1) the fundamental fermionic field becomes massive in both phases of the model, which is closely related to the supersymmetry breaking term; 2) the O(N) symmetric phase presents a meta-stable vacuum.

hep-th↗
arXiv2013

On the many-field f(R) brane

We consider the Randall-Sundrum braneworld theory with a single extra dimension of infinite extent to investigate generalized $f(R)$ braneworld models in the presence of several real scalar fields. In particular, we solve the modified Einstein equations for the case of flat brane, with zero cosmological constant, and for the case of bent brane, with a nonvanishing cosmological constant. In both cases we found explicit solutions for the scalar fields with analytical expressions for the respective warp factors.

hep-th↗
arXiv2013

Supergauge theories in aether superspace

Within the superfield method we extend the formulation of the Lorentz-breaking aether superspace for supergauge theories, both in three- and in four-dimensional cases.

hep-th↗
arXiv2013

Some Generalizations in Supersymmetric Quantum Mechanics and the Supersymmetric $\varepsilon$-System Revisited

We discuss two distinct aspects in supersymmetric quantum mechanics. First, we introduce a new class of operators A and $\bar{A}$ in terms of anticommutators between the momentum operator and N+1 arbitrary superpotentials. We show that these operators reduce to the conventional ones which are the starting point in standard supersymmetric quantum mechanics. In this context, we argue furthermore that supersymmetry does not only connect Schrödinger-like operators, but also a more general class of differential operators. Second, we revisit the supersymmetric $\varepsilon$-system recently introduced in the literature by exploiting its intrinsic supersymmetry. Specifically, combining the Hamilton hierarchy method and the $δ$-expansion method, we determine an energy for the first excited state of the bosonic Hamiltonian close to that calculated in earlier works.

hep-th↗
arXiv2013

Two-loop effective potential for the Wess-Zumino model in 2+1 dimensions

By using superfield techniques, the effective potential of the $\mathcal{N}=1$ Wess-Zumino model in 2+1 dimensions is computed off-shell up to two loops. It is shown that supersymmetry is not dynamically broken, and that dynamical generation of mass does not occur perturbatively. We also investigate the renormalization of the effective potential and determine the renormalization group gamma and beta functions, showing that this model is infrared free. Comparison with some other results in the literature is provided.

hep-th↗
arXiv2012

Higher-Derivative Wess-Zumino Model in Three Dimensions

We deform the well-known three dimensional $\mathcal{N}=1$ Wess-Zumino model by adding higher derivative operators (Lee-Wick operators) to its action. The effects of these operators are investigated both at the classical and quantum levels.

hep-th↗
arXiv2012

Effective potential for a SUSY Lee-Wick model: the Wess-Zumino case

Using a superfield generalization of the tadpole method, we study the one-loop effective potential for a Wess Zumino model modified by a higher-derivative term, inspired by the Lee-Wick model. The one-loop Kählerian potential is also obtained by other methods and compared with the effective potential.

hep-th↗
arXiv2012

Lorentz violation bounds on Bhabha scattering

We investigate the effect of Lorentz-violating terms on Bhabha scattering in two distinct cases correspondent to vectorial and axial nonminimal couplings in QED. In both cases, we find significant modifications with respect to the usual relativistic result. Our results reveal an anisotropy of the differential cross section which imply new constraints on the possible Lorentz violating terms.

hep-ph↗