arXiv subjects
Publications and source records attributed to Everton M. C. Abreu.
In this Letter we have derived the Jeans length in the context of the Kaniadakis statistics. We have compared this result with the Jeans length obtained in the non-extensive Tsallis statistics and discussed the main differences between these two models. We have also obtained the kappa-sound velocity. Finally, we have applied the results obtained here to analyze an astrophysical system.
In this paper we have analyzed the $κ$-deformed Minkowski spacetime through the light of the interference phenomena in QFT where two opposite chiral fields are put together in the same multiplet and its consequences are discussed. The chiral models analyzed here are the chiral Schwinger model, its generalized version and its gauge invariant version, where a Wess-Zumino term were added. We will see that the final actions obtained here are in fact related to the original ones via duality transformations.
With the elements of the Doplicher, Fredenhagen and Roberts (DFR) noncommutative formalism, we have constructed the standard electroweak model. To accomplish this task we have begun with the WM-product basis group of symmetry. We have introduced the spontaneous symmetry breaking and the hypercharge in DFR framework. The electroweak symmetry breaking was analyzed and the masses of the new bosons were computed.
In this paper, by using Verlinde's formalism and a modified Padmanabhan's prescription, we have obtained the lowest order quantum correction to the gravitational acceleration and MOND-type theory by considering a nonzero difference between the number of bits of the holographic screen and the number of bits of the holographic screen that satisfy the equipartition theorem (the bulk). We will also carry out an analysis for the pure and an asymptotic (actual) de Sitter Universe considering the holographic principle. We had also used nonextensive concepts into the theory and we accomplished a $N$-dimensional generalization of our results. Some physical consequences of the nonextensive ideas in Gauss-Bonnet (GB) gravity theory were analyzed also. We have obtained the $q$-parameter as a function of the GB coefficient and some physical aspects were discussed.
The Doplicher-Fredenhagen-Roberts (DFR) framework for noncommutative (NC) space-times is considered as an alternative approach to describe the physics of quantum gravity, for instance. In this formalism, the NC parameter, {\it i.e.} $θ^{μν}$, is promoted to a coordinate of a new extended space-time. Consequently, we have a field theory in a space-time with spatial extra-dimensions. This new coordinate has a canonical momentum associated, where the effects of a new physics can emerge in the fields propagation along the extra-dimension. In this paper we introduce the gauge invariance in the DFR NC space-time. We present the non-Abelian gauge symmetry in DFR formalism, and the consequences of this symmetry in the presence of such extra-dimension. The gauge symmetry in this DFR scenario can reveal new fields attached to $θ$-extra-dimension. We obtain the propagation of these gauge fields in terms of canonical momentum associated with $θ$-coordinate.
The so-called canonical noncommutativity is based on a constant noncommutative parameter ($θ$). However, this formalism breaks Lorentz invariance and one way to recover it is to define the NC parameter as a variable, an extra coordinate of the system. One approach that uses the variable $θ$ was developed by Doplicher, Fredenhagen and Roberts (DFR) and hence, their phase-space is formed by $(x,p,θ)$ with extra-dimensions. In this work we have demonstrated precisely that this phase-space is incomplete because the variable $θ$ requires an associated momentum and the so-called DFR phase-space is in fact formed by $(x, p, θ, π)$, where $π$ is an useful object. One of the models used here to demonstrate this fact brought other interesting results. We have used this complete phase-space to explain some undefined results in the $θ$-variable literature. Finally, we have shown the importance of this DFR-momentum since with it we could fill the gap that exist in $θ$-variable results. In other words, we have computed the field commutation relations of a QFT in this DFR phase-space. The results obtained here match exactly with the postulated (not demonstrated) values that dwell in the DFR literature.
In this work we have obtained Maxwell-type equations for a compressible fluid which sources are functions of velocity and vorticity. A correlation function and the dispersion relation were analyzed as function of the Reynolds number. A Lagrangian for the Lamb vector and the vorticity was constructed and the equations of motion were discussed. After that, we have analyzed the case of a charged fluid dynamics. Finally, the non-Abelian generalization of some results was introduced. A basic review for non-Abelian fluids was described in the Appendix.
In this paper, by using Verlinde's formalism and a modified Padmanabhan's prescription, we have obtained the lowest order quantum correction to the gravitational acceleration and MOND-type theory by considering a nonzero difference between the number of bits of the holographic screen and number of bits of the holographic screen that satisfy the equipartition theorem. We will also carry out a phase transition and critical phenomena analysis in MOND-type theory where critical exponents are obtained.
In this paper we have derived the equipartition law of energy using Tsallis formalism and the Kaniadakis power law statistics in order to obtain a modified gravitational constant. We have applied this result in the gravothermal collapse phenomenon. We have discussed the equivalence between Tsallis and the Kaniadakis statistics in the context of Verlinde entropic formalism. In the same way we have analyzed negative heat capacities in the light of gravothermal catastrophe. The relative deviations of the modified gravitational constants are derived.
In this work, we focus on the fermionic structure of the low-energy excitations of graphene (a monolayer of carbon atoms) to propose a new supersymmetric field-theoretic model for this physical system. In the current literature, other proposals for describing graphene physics have been contemplated at the level of supersymmetric quantum mechanics. Also, by observing the inhomogeneities between neighbor carbon atoms, Jackiw {\it et al.} have set up an interesting chiral Abelian gauge theory. We show in this paper that our formulation encompasses models discussed previously as sectors of an actually richer (supersymmetric) planar gauge model. Possible interpretations for the fields involved in the present graphene model are proposed and the question of supersymmetry breaking is discussed.
In a previous work, we have been able to settle Jackiw's et al. chiral gauge theory for Dirac fermions in graphene in an N=1 supersymmetric framework, using a tau3-QED prescription, defined by means of a single pair of gauge charged superfields, but without preserving a global phase symmetry associated to the electric charge. In the present work, we propose another N=1-generalisation which indeed preserves this symmetry, namely, a straightforward extension built upon a set of two pairs of (chiral) gauge-charged superfields plus an extra pair of electrically neutral superfields. We then further proceed to establish, via a dimensional reduction procedure, an N=2 extension, allowing for the identification of non-perturbative features, as we put forward Bogomol'nyi equations and obtain vortex-like solutions saturating a topologically non-trivial bound. Remarkably, the bosonic projection of the N=2 functional space onto the saturated regime analysed herewith reveals to be free from extra scalar degrees of freedom that would otherwise demand a phenomenological interpretation. The investigation of Jackiw's model within an N=2 complex superspace is also motivated by the assumption that an R-parity-like symmetry could provide a route to incorporate the global phase-fermion number invariance as an external-like symmetry of the theory, thus associating the electric charge in graphene to the complex covariance (super-)space for the N=2-D=3 setup. We prove such a hypothesis to be realisable, as we build up the model endowed with all the symmetries required to further extend Jackiw's chiral gauge theory.
It is a very well known fact that the energy conditions concerning traversable wormhole (WH) solutions of Einstein equations are violated. Consequently, attempts to avoid the violation of the energy conditions constitutes one of the main areas of research in WH physics. On the other hand, the current literature shows us that noncommutativity is one of the most promising candidates to help us to understand the physics of the early Universe. However, since noncommutativity does not change the commutative results, we also can expect that energy conditions violation near the throat must occur. We will show here that the violation of the energy conditions, described in a noncommutative space-time, has fixed conditions on the angular momentum of a rotating WH with constant angular velocity. Also, we have established a new theoretical bound on the NC constant, $θ$, as a function of some WH parameters.
The accelerated expansion of the Universe is one of the greatest challenges of modern physics. One candidate to explain this phenomenon is a new field called dark energy. In this work we have used the Tsallis nonextensive statistical formulation of the Friedmann equation to explore the Barboza-Alcaniz and Chevalier-Polarski-Linder parametric dark energy models and the Wang-Meng and Dalal vacuum decay models. After that, we have discussed the observational tests and the constraints concerning the Tsallis nonextensive parameter.
It is well known that a direct Lagrangian description of radiation damping is still missing. In this paper a specific approach of this problem was used, which is the standard way to treat the radiation damping problem. A $N=2$ supersymmetric extension for the model describing the radiation damping on the noncommutative plane with electric and magnetic interactions was obtained. The entire supercharge algebra and the total Hamiltonian for the system were analyzed. Finally, noncommutativity features were introduced and its consequences were explored..
MOND theory explains the rotation curves of the galaxies. Verlinde's ideas establishes an entropic origin for gravitational forces and Tsallis principle generalizes the theory of Boltzman-Gibbs. In this work we have promoted a connection between these recent approaches, that at first sight seemed to have few or no points in common, using the Mach's principle as the background. In this way we have used Tsallis formalism to calculate the main parameters of the Machian Universe including the Hubble parameter and the age of the Universe. After that, we have also obtained a new value for the Tsallis parameter via Mach's principle. Using Verlinde's entropic gravity we have obtained new forms for MOND's well established ingredients. Finally, based on the relations between particles and bits obtained here, we have discussed the idea of bits entanglement in the holographic screen.
The interest in higher derivatives field theories has its origin mainly in their influence concerning the renormalization properties of physical models and to remove ultraviolet divergences. In this letter we have introduced the noncommutative (NC) version of the Podolsky theory and we investigated the effect of the noncommutativity over its original gauge invariance property. We have demonstrated precisely that the noncommutativity spoiled the gauge invariance of the original action. After that we have used the Noether dualization technique to obtain a dual and gauge invariant action. More than to obtain the NC Podolsky theory, we have another motivation in this work, which is to show that, although the introduction of noncommutativity spoils the gauge invariance, it is possible to recover this property using a standard dualization method which did not need any modification due to any NC effect in the original theory, by the way
Based on the connection between Tsallis nonextensive statistics and fractional dimensional space, in this work we have introduced, with the aid of Verlinde's formalism, the Newton constant in a fractal space as a function of the nonextensive constant. With this result we have constructed a curve that shows the direct relation between Tsallis nonextensive parameter and the dimension of this fractal space. We have demonstrated precisely that there are ambiguities between the results due to Verlinde's approach and the ones due to fractional calculus formalism. We have shown precisely that these ambiguities appear only for spaces with dimensions different from three. Hence, we believe that this is a result in favor of our three dimensional world.
The framework Doplicher-Fredenhagen-Roberts (DFR) of a noncommutative (NC) space-time is considered as a alternative approach to study the NC space-time of the early Universe. In this formalism, the parameter of noncommutative $θ^{μν}$ is promoted to a coordinate of the space-time, and consequently, we are describing a field theory in a space-time with extra-dimension. Consequently, there is a canonical momentum associated to this new coordinate in which the effects of a new physics can emerge in the propagation of the fields along the extra-dimension. The Fourier space of this framework is automatically extended by the addition of new momenta components. The main concept that we would like to emphasize from the outset is that the formalism demonstrated here will not be constructed introducing a NC parameter in the system, as usual. It will be generated naturally from an already NC space. When the components of the new momentum are zero, the DFR approach is reduced to the usual NC case, in which $θ^{μν}$ is a antisymmetric constant matrix. We study a scalar field action with self-quartic interaction $ϕ^{4}\star$ defined in the DFR NC spacetime, obtaining the Feynman rules in the Fourier space for the scalar propagator and vertex of the model. With these rules we are able to build out the radiative corrections to one loop order for the model propagator. The influence of the NC scale, as well as the propagation of the field in the extra-dimension, are analyzed in the ultraviolet divergences scenario. We investigate the actual possibility if this $θ^{μν}$ conjugate momentum has the property of healing the mixing IR/UV divergences that emerges in this recently new NC spacetime quantum field theory.