arXiv subjects

Cristine N. Ferreira

Publications and source records attributed to Cristine N. Ferreira.

15 recordsLinked to original sources

arXiv2020

Charge and Spin Currents in a Lower-Dimensional Supersymmetric Model in Presence of Vortices

We investigate charge and spin currents that may appear in some materials, considering the possible couplings and the symmetries of a field-theoretical model presented here. We inspect these possible currents in (1+2) dimensions by adopting an N =2 - D=3 supersymmetric framework with a Chern-Simons term and non-minimal couplings as well. We discuss a number of aspects in connection with a vortex configuration that is topologically viable. The new features of our investigation take into account the nature of both the U(1)-symmetry and supersymmetry (SUSY) breakings in presence of the vortex. We focus on aspects of the fermionic sector and their interactions with the currents. In connection with the spectrum of fermions, we also derive the mass gap in terms of the parameters of the the model. Another point we highlight is the role SUSY in our considerations. Once graphene and topological insulator materials are described by a Dirac-like equation, we assume, as a working hypothesis, that SUSY may also have some influence on the properties of these materials. Along this line, it is mandatory to connect the SUSY breakdown to this class of materials. We believe that our discussion could bring some elements for the understanding of this category of lower-dimensional systems.

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arXiv2016

Torsion Effects and LLG Equation

Based on the non-relativistic regime of the Dirac equation coupled to a torsion pseudo-vector, we study the dynamics of magnetization and how it is affected by the presence of torsion. We consider that torsion interacting terms in Dirac equation appear in two ways one of these is thhrough the covariant derivative considering the spin connection and gauge magnetic field and the other is through a non-minimal spin torsion coupling. We show within this framework, that it is possible to obtain the most general Landau, Lifshitz and Gilbert (LLG) equation including the torsion effects, where we refer to torsion as a geometric field playing an important role in the spin coupling process. We show that the torsion terms can give us two important landscapes in the magnetization dynamics: one of them related with damping and the other related with the screw dislocation that give us a global effect like a helix damping sharped. These terms are responsible for changes in the magnetization precession dynamics.

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arXiv2015

Thermodynamical Analysis of a Black Hole with a Global Monopole Within a Class of a f(R) Gravity

We analyze the thermodynamics of a black hole in a region that contains a global monopole in the framework of a particular class of a f(R) gravity. Specifically, we study the case in which df(R)/dR = F(R) is a power law function of the radial coordinate of the monopole spacetime, i.e., F(r) = 1 + ψ_n r^n, where ψ_n is the fine-tuned parameter corresponding to the f(R) gravity. We obtain explicit expressions for the local thermodynamic quantities of the black hole as a function of the event horizon, the parameter describing the monopole and the measurable corrections due to the f(R) theory modifications of the General Relativity. We also discussed the implications of the particular case of n=2, where the parameter ψ_2 can be related to a positive cosmological constant, that in monopole presence is characterized by a non-trivial topology observed as a deficit solid angle.

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arXiv2013

BPS solution for eleven-dimensional supergravity with a conical defect configuration

In this work, we found the solution for the field equations of eleven-dimensional supergravity with a BPS conical topological defect configuration. We chose the solutions that corresponded to a M2-brane where the space-time presents the co-dimension two. The source of the topological defect is a sigma model where the brane tension is connected with the angular deficit. We analyzed the Killing spinor equations, a 3-form gauge potential and Einstein's equations, proving that it is possible to find a full solution for the system. We analyzed the near-horizon limit proving that it is possible to obtain an $AdS_4 \times S^1 \times \mathbb{E}^6 $ geometry for certain values of the brane tension. We also discussed some applications in the strong coupling theory for condensed matter systems.

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arXiv2013

DBI equations and holographic DC conductivity

We provide a simple method for writing the Dirac-Born-Infeld (DBI) equations of a Dp-brane in an arbitrary static background whose metric depends only on the holographic radial coordinate z. Using this method we revisit the Karch-O'Bannon's procedure to calculate the DC conductivity in the presence of constant electric and magnetic fields for backgrounds where the boundary is four or three dimensional and satisfies homogeneity and isotropy. We find a frame-independent expression for the DC conductivity tensor. For particular backgrounds we recover previous results on holographic metals and strange metals.

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arXiv2010

A conical deficit in the AdS4/CFT3 correspondence

Inspired by the AdS/CFT correspondence we propose a new duality that allow the study of strongly coupled field theories living in a 2+1 conical space-time. Solving the 4-d Einstein equations in the presence of an infinite static string and negative cosmological constant we obtain a conical AdS4 space-time whose boundary is identified with the 2+1 cone found by Deser, Jackiw and 't Hooft. Using the AdS4/CFT3 correspondence we calculate retarded Green's functions of scalar operators living in the cone.

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arXiv2010

D-dimensional Randall-Sundrum models from Brans-Dicke theory and Kaluza-Klein modes

We investigate the spectroscopy of scalar and vector Kaluza-Klein modes that arise in a deformed Randall-Sundrum model that is constructed from Brans-Dicke theory. The non-minimal coupling in the Brans Dicke theory translates into a deformation of the Randall-Sundrum geometry that depends on the Brans-Dicke parameter $ω$. We find that the $ω$ parameter has a non-trivial effect in the spectroscopy of scalar and vector Kaluza-Klein modes. Our results suggest the interpretation of $ω$ as a fine-tuning parameter.

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arXiv2008

Static strings in global AdS space and quark anti-quark potential

We investigate the finite temperature quark anti-quark problem in a compact space $S^{n-1}\times S^1$ by considering static strings in global $AdS_{n+1}$ space with $n\ge 3$. For high temperatures we work in the black hole metric where two possible solutions show up : the big black hole and the small black hole. Using the AdS/CFT correspondence, we calculate the quark anti-quark potential (free energy) as a function of the distance. We show that this potential can be intrepeted as confining for the $AdS$ space and deconfining for the big black hole. We find for the small black hole a confining limit for the potential but this solution is instable following the Hawking-Page criteria. Our results for the free energy reinforce the Witten interpretation of the confinement/deconfinement transition as the dual of the well-known Hawking-Page transition.

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arXiv2006

Static strings in Randall-Sundrum scenarios and the quark anti-quark potential: Erratum

We correct the energy of the static strings in hep-th/0512295, for large quark anti-quark separation. This energy is a smooth function of the quark separation for any position of the infrared brane. The asymptotic behavior of this energy is that of the Cornell potential as stated in the article. However, this identification does not fixes the AdS radius.

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arXiv2006

Heavy quark potential at finite temperature from gauge/string duality

A static string in an AdS Schwarzschild space is dual to a heavy quark anti-quark pair in a gauge theory at high temperature. This space is non confining in the sense that the energy is finite for infinite quark anti-quark separation. We introduce an infrared cut off in this space and calculate the corresponding string energy. We find a deconfining phase transition at a critical temperature T_C. Above T_C the string tension vanishes representing the deconfined phase. Below T_C we find a linear confining behavior for large quark anti-quark separation. This simple phenomenological model leads to the appropriate zero temperature limit, corresponding to the Cornell potential and also describes a thermal deconfining phase transition. However the temperature corrections to the string tension do not recover the expected results for low temperatures.

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arXiv2006

Supermassive screwed cosmic string in dilaton gravity

The early Universe might have undergone phase transitions at energy scales much higher than the one corresponding to the Grand Unified Theories (GUT) scales. At these higher energy scales, the transition at which gravity separated from all other interactions; the so-called Planck era, more massive strings called supermassive cosmic strings, could have been produced, with energy of about 10^{19}GeV. The dynamics of strings formed with this energy scale cannot be described by means of the weak-field approximation, as in the standard procedure for ordinary GUT cosmic strings. As suggested by string theories, at this extreme energies, gravity may be transmitted by some kind of scalar field (usually called the {\it dilaton}) in addition to the tensor field of Einstein's theory of gravity. It is then permissible to tackle the issue regarding the dynamics of supermassive cosmic strings within this framework. With this aim we obtain the gravitational field of a supermassive screwed cosmic string in a scalar-tensor theory of gravity. We show that for the supermassive configuration exact solutions of scalar-tensor screwed cosmic strings can be found in connection with the Bogomol'nyi limit. We show that the generalization of Bogomol'nyi arguments to the Brans-Dicke theory is possible when torsion is present and we obtain an exact solution in this supermassive regime, with the dilaton solution obtained by consistency with internal constraints.

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arXiv2006

Static strings in Randall-Sundrum scenarios and the quark anti-quark potential

We calculate the energy of a static string in an AdS slice between two D3-branes with orbifold condition. The energy for configurations with endpoints on a brane grows linearly for large separation between these points. The derivative of the energy has a discontinuity at some critical separation. Choosing a particular position for one of the branes we find configurations with smooth energy. In the limit where the other brane goes to infinity the energy has a Coulombian behaviour for short separations and can be identified with the Cornell potential for a quark anti-quark pair. This identification leads to effective values for the AdS radius, the string tension and the position of the infrared brane. These results suggest an approximate duality between static strings in an AdS slice and a heavy quark anti-quark configuration in a confining gauge theory.

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arXiv2005

On the Potentials of Supersymmetric Theories with Gauge-Field Mixing Terms

In this letter, we reconsider the delicate issue of symmetry and supersymmetry breakings for gauge theories with gauge-field mixings. The purpose is to study generalyzed potentials in the presence of more than a single gauge potential. In this work, following a stream of investigation on supersymmetric gauge theories without flat directions, we contemplate the possibility of building up D- and F-term potentials by means of a gauge-field mixing in connection with a U(1)x U(1)' -symmetry. We investigate a generalized potential including an N=1 supersymmetric extension of the Maxwell-Chern-Simons model focusing on the study of cosmic string configurations. This analysis sheds some light on the formation of cosmic strings for model with violation of Lorentz symmetry.

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arXiv2004

Topological mass term in effective Brane-World scenario with torsion

In this work we investigate a braneworld scenario where a Kalb-Ramond field propagates, together with gravity, in a five dimensional AdS slice. The rank-2 Kalb-Ramond field is associated with torsion. We study the compactification of the Kalb-Ramond field to four dimensional space-time without gauge fixing, focusing on the effects of torsion. On the brane the Kalb-Ramond field interacts with $A_μ$-gauge and scalar matter fields. We analyze the propagators of this theory and as an application investigate the consistency of such a model in the presence of a cosmic string configuration. One interesting feature of this model is the presence of topological charge coming from a topological mass term that couples the gauge field $A_μ$ with Kalb-Ramond modes.

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arXiv2004

Nonequivalent Seiberg-Witten maps for noncommutative massive U(N) gauge theory

Massive vector fields can be described in a gauge invariant way with the introduction of compensating fields. In the unitary gauge one recovers the original formulation. Although this gauging mechanism can be extended to noncommutative spaces in a straightforward way, non trivial aspects show up when we consider the Seiberg-Witten map. As we show here, only a particular class of its solutions leads to an action that admits the unitary gauge fixing.

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