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M. Gomes

Publications and source records attributed to M. Gomes.

At least 37 records · Page 2Linked to original sources

Remarks on a Lorentz-breaking 4D chiral gauge theory

We investigate a Lorentz-violating chiral model composed by two fermions, a complex scalar field and a gauge field. We show that by convenientely adjusting the parameters of the model, it is possible to generate an unambiguous Carroll-Field-Jackiw term and, at the same time, provide the cancelation of the chiral anomaly. The renormalizability of the model is investigated and it is shown that the same counterterms needed in the symmetric phase also renormalize the model with broken symmetry.

hep-th↗

On one-loop corrections in the Horava-Lifshitz-like QED

We study the one-loop two point functions of the gauge, scalar and spinor fields for a Horava-Lifshitz-like QED with critical exponent $z=2$. It turns out that, in certain cases, the dynamical restoration of the Lorentz symmetry at low energies can take place. We also analyze the three point vertex function of the gauge and spinor fields and prove that the triangle anomaly identically vanishes in this theory.

hep-th↗

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↗

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↗

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↗

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↗

Chern-Simons terms in Lifshitz like quantum electrodynamics

In this work the generation of generalized Chern-Simons terms in three dimensional quantum electrodynamics with high spatial derivatives is studied. We analyze the self-energy corrections to the gauge field propagator by considering an expansion of the amplitude up to third order in the external momenta. The divergences of the corrections are determined and explicit forms for the Chern-Simons terms with high derivatives are obtained. Some unusual aspects of the calculation are stressed and the existence of a smooth isotropic limit is proved. The transversality of the anisotropic gauge propagator is also discussed.

hep-th↗

Stochastic Quantization of the Spherical Model and Supersymmetry

We use the stochastic quantization method to construct a supersymmetric version of the quantum spherical model. This is based on the equivalence between the Brownian motion described by a Langevin equation and the supersymmetric quantum mechanics, which is connected with the existence of the Nicolai map. We investigate the critical behavior of the supersymmetric model at finite as well as at zero temperatures, showing that it exhibits both classical and quantum phase transitions, and determine the critical dimensions.

cond-mat.stat-mech↗

Competing interactions and the Lifshitz-type Nonlinear Sigma Model

We establish the equivalence between the continuum limit of the quantum spherical model with competing interactions, which is relevant to the investigation of Lifshitz points, and the O(N) nonlinear sigma model with the addition of higher order spatial derivative operators, which breaks the Lorentz symmetry and is known as Lifshitz-type (or anisotropic) nonlinear sigma model. In the context of the 1/N expansion, we also discuss the renormalization properties of this nonlinear sigma model and find the nontrivial fixed points of the beta-functions in various dimensions, which turn out to be connected with the existence of phase transitions in the quantum spherical model.

hep-th↗

Braneworlds scenarios in a gravity model with higher order spatial three-curvature terms

In this work we study a Horava-like five-dimensional model in the context of braneworld theory. To begin with, the equations of motion of such model are obtained and, within the realm of warped geometry, we show that the model is consistent if and only if $λ$ takes its relativistic value 1. Furthermore, since the first derivative of the warp factor is discontinuous over the branes, we show that the elimination of problematic terms involving the square of the warp factor second order derivatives are eliminated by imposing detailed balance condition in the bulk. Afterwards, the Israel's junction conditions are computed, allowing the attainment of an effective Lagrangian in the visible brane. In particular, for a (4+1)-dimensional Horava-like model defined in the bulk without cosmological constant, we show that the resultant effective Lagrangian in the brane corresponds to a (3+1)-dimensional Horava-like model with an emergent positive cosmological constant but without detailed balance condition. Now, restoration of detailed balance condition, at this time imposed over the brane, plays an interesting role by fitting accordingly the sign of the arbitrary constant $β$ that labels the extra terms in the model, insuring a positive brane tension and a real energy for the graviton within its dispersion relation. To end up with, the brane consistency equations are obtained and, as a result, we show that the detailed balance condition again plays an essential role in eliminating bad behaving terms and that the model admits positive brane tensions in the compactification scheme if, and only if, $β$ is negative, what is in accordance with the previous result obtained for the visible brane.

hep-th↗

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↗

Propagator in the Horava-Lifshitz gravity

In this paper it is studied the propagator for the modified theory of gravity proposed by Ho\vrava. We first calculate the propagator in the $λ=1$ case and show that the main poles that arise correspond to the spin two particle and scalar particle, already known in the literature. The presence of a bad ultraviolet behaving term spoils renormalizability of the theory but it is eliminated by imposing the detailed balance condition, although just a soft version of this condition is actually needed. The problems of a negative mass term and a residue with undefined sign, which is due to the presence of the cosmological constant, is verified at the tree level demanding a complete elimination of the tadpole in order to be fully analyzed. However, in the absence of such constant, the extra scalar degree of freedom has no dynamics, at least at the tree-level, and the theory posses only two dynamical degrees of freedom. Also, to understand the implications of $λ$, we analyse a simplified model, the $λR$ theory, and verify that it becomes non unitary, being a strong argument to set $λ=1$.

hep-th↗

Dynamics of a Dirac Fermion in the presence of spin noncommutativity

Recently, it has been proposed a spacetime noncommutativity that involves spin degrees of freedom, here called "spin noncommutativity". One of the motivations for such a construction is that it preserves Lorentz invariance, which is deformed or simply broken in other approaches to spacetime noncommutativity. In this work, we gain further insight in the physical aspects of the spin noncommutativity. The noncommutative Dirac equation is derived from an action principle, and it is found to lead to the conservation of a modified current, which involves the background electromagnetic field. Finally, we study the Landau problem in the presence of spin noncommutativity. For this scenario of a constant magnetic field, we are able to derive a simple Hermitean non-commutative correction to the Hamiltonian operator, and show that the degeneracy of the excited states is lifted by the noncommutativity at the second order or perturbation theory.

hep-th↗

Supersymmetric Extension of the Quantum Spherical Model

In this work, we present a supersymmetric extension of the quantum spherical model, both in components and also in the superspace formalisms. We find the solution for short/long range interactions through the imaginary time formalism path integral approach. The existence of critical points (classical and quantum) is analyzed and the corresponding critical dimensions are determined.

cond-mat.stat-mech↗