arXiv subjects
Publications and source records attributed to I. C. Jardim.
This paper presents the effects of non-minimal Lorentz-violation operators in superconductivity. By constructing a Lorentz-Violating Ginzburg-Landau theory of superconductivity with a five-dimensional operator, we discuss the influence of higher dimensional Lorentz-Violating operators in the London's depth penetration, in the coherence length and critical magnetic field.
We explore the conformal 5D braneworld, where warping emerges through conformal symmetry breaking. Our scenario seamlessly aligns with conventional brane approaches if conformal symmetry remains unbroken. It is shown that a model with a single conformal breaking parameter effectively localizes gravity on the brane, but it falls short in trapping gauge bosons. However, in scenarios with two parameters, gravity is localized, and the model also achieves the localization of zero modes for both gauge and Dirac fields.
In this manuscript, we discuss the confinement of the spin $\frac{1}{2}$ field on a plethora of branewords models. Recently, in (Eur.Phys.J.C 80 (2020) 5, 432), we studied the consistency of the Standard Model (SM) fields localization on braneworlds with the Einstein equation. In that paper, we discussed the consistency of the spinor field confinement and, by using a Yukawa-like interaction given by $\mathcal{L}_{int}\propto f(y)\barΨΨ$, we obtained that the function must be defined as $f(y)\propto e^{-A}A'$. This shape of the scalar function emerge from the requirement that the spin $\frac{1}{2}$ (zero-mode) localization cannot modify the metric on bulk. This ensures that the confinement of gravity on the brane is preserved. In the present manuscript, we find a covariant scalar-coupling function that can generate this interaction. This provide a new mechanism for localizing fermion fields over the brane. We also discuss massive modes and we found some gravitational configuration where there are confined and discretized massive modes.
Wormholes (WH) require negative energy, and therefore an exotic matter source. Since Casimir energy is negative, it has been speculated as a good candidate to source that objects a long time ago. However only very recently a full solution for $D = 4$ has been found by Garattini, thus the Casimir energy can be a source of traversable WHs. In the manuscript published by the authors, we show that this solution is possible for all space-time of dimension $D > 3$. Recently, Garattini sought to analyze the effects of Yukawa-type terms on shape functions and obtained promising results. However, it assumes reasonably questionable premises when establishing a non-homogeneity in the Equation of State, when assuming a fixation between the constants that is only observed in the usual model and when considering the Zero Tidal Condition, not observed in Casimir's wormholes. In this work, we study the effects generated by Yukawa-type corrective factors on traversable wormhole solutions generated by Casimir energy without assuming such premises. We observe that, in addition to being possible to build traversable wormholes that satisfy all the necessary conditions, it is possible to obtain an adequate fixation of the constants in order to recover the standard case without a double limit. It was observed that, in the global and constant cases, it is possible to set a value in the shielding parameter that makes the wormhole generate a repulsive gravitational force. Finally, we observed that in the constant case there was a limitation for the shielding factor, something not observed in the original article.
This paper presents the effects of Lorentz violation in superconductivity. Constructing a Lorentz-Violating Ginzburg-Landau theory of superconductivity we discuss the influence of the Lorentz-Violating tensors $\hat{k}_{c}^{ij}$ and $\hat{k}_a^i$ in the London's depth penetration, in the coherence length and critical magnetic field.
Wormholes (WH) require negative energy, and therefore an exotic matter source. Since Casimir energy is negative, it has been speculated as a good candidate to source that objects a long time ago. However only very recently a full solution for D = 4 has been found by Garattini [1], thus the Casimir energy can be a source of traversable WHs. Soon later Alencar et al [2] have shown, that this is not true in D = 3. In this paper, we show that Casimir energy can be a source of the Morris-Thorne WH for all spacetime with D > 3. Finally, we add the cosmological constant and find that for D = 3 Casimir WHs are possible, however, the space must always being AdS. For D > 3, we show that the cosmological constant invert the signal with increasing throat size.
In this paper we study the coupling of $p$-form fields with geometrical tensor fields, namely Ricci, Einstein, Horndeski and Riemann in Randall-Sundrum scenarios with co-dimension one. We consider delta-like and branes generated by a kink and a domain wall. We begin by a detailed study of the Kalb-Ramond (KR) field. The analysis of KR field is very rich since it is a tensorial object and more complex non-minimal couplings are possible. The generalization to $p$-forms can provide more information about the properties and structures that can possibly be universal in the geometrical localization mechanism. The zero mode is treated separately and conditions for localization of zero modes of $p-$forms are found for all the cases above and with this we arrive at the above conclusion about vector fields. Another property that can be tested is the absence of resonances found in the case of vector fields. For this we analyze the possible unstable massive modes for all the above cases via transmission coefficient. Our conclusion is that we have more probability to observe massive unstable modes in the Ricci and Riemann coupling.
The Geometrical Localization mechanism in Randall-sundrum (RS) scenarios is extended by considering the coupling between a quadratic mass term and geometrical tensors. Since the quadratic term is symmetric, tensors with two symmetric indices have to be taken into account. These are the Ricci and the Einstein tensors. For the Ricci tensor it is shown that a localized zero mode exists while that is not possible for the Einstein tensor. It is already known that the Ricci scalar generates a localized solution but the metrics do not. Therefore, it can be conclude that divergenceless tensors do not localize the zero mode of gauge fields. The result is valid for any warp factor recovering the RS metrics at the boundaries, and therefore is valid for RS I and II models. We also compute resonances for all couplings. These are calculated using the transfer matrix method. The cases studied consider the standard RS with delta-like branes, and branes generated by kinks and domain-wall as well. The parameters are changed to control the thickness of the smooth brane. We find that, for all cases considered, geometrical coupling does not generate resonances. This enforces similar results for the coupling with the Ricci scalar and points to the existence of some unidentified fundamental structure of these couplings.
In this manuscript we show that the geometrical localization mechanism implies a four dimensional mass for the photon. The consistence of the model provides a mass given exactly by $m_γ=\sqrt{R}/4$ where $R$ is the Ricci scalar. As a consequence, the cosmological photon has a mass related to the vacuum solution of the Einstein equation. At the present age of the universe we have a dS vacuum with $R=4Λ$, where Lambda is a positive cosmological constant. With this we find that $m_γ\approx 2\times 10^{-69}$ kg, which is below the present experimental upper bounds, and such correction may be observed in the next years with more precise measurements. By considering the value of $R$ inside some astrophysical sources and environments we find that the bound is also satisfied. The experimental verification of this mass, beyond pointing to the existence of extra dimensions, would imply in a fundamental change in cosmology, astrophysics and in particle physics since the same mechanism is valid for non-abelian gauge fields.
In this paper we study how to include the cosmological constant in geometric scalar theory of gravity (GSG). Firstly we show that the cosmological constant could not be modeled by a matter field, unlike in General Relativity. We also show that a spherically symmetric matter distribution, over the de Sitter vacuum, does not produce the Kottler solution and no black hole. To circumvent this problem we introduce an coupling term between the scalar field and the vacuum curvature in way to provide the Kottler solution. We also apply the original (GSGI) and the modified (GSGII) geometric scalar theory of gravity to the Friedmann-Robertson-Walker cosmology. A numerical analysis indicates that GSGII is most sensible to the cosmological constant them GSGI.
Geometrical coupling in a co-dimensional one Randall-Sundrum scenario (RS) is used to study resonances of $p-$form fields. The resonances are calculated using the transfer matrix method. The model studied consider the standard RS with delta-like branes, and branes generated by kinks and domain-wall as well. The parameters are changed to control the thickness of the smooth brane. With this a very interesting pattern is found for the resonances. The geometrical coupling does not generate resonances for the reduced $p-$form in all cases considered.
It is shown here that the zero mode of any form field can be trapped to the brane using the model proposed by Ghoroku and Nakamura. We start proven that the equations of motion can be obtained without splitting the field in even and odd parts. The massive and tachyonic cases are studied revealing that this mechanism only traps the zero mode. The result is then generalized to thick branes. In this scenario, the use of a delta like interaction of the quadratic term is necessary leading to a "mixed" potential with singular and smooth contributions. It is also shown that all forms produces an effective theory in the brane without gauge fixing. The existence of resonances with the transfer matrix method is then discussed. With this we analyze the resonances and look for peaks indicating the existence of unstable modes. Curiously no resonances are found in opposition of other models in the literature. Finally we find analytical solutions for arbitrary $p-$forms when a specific kind of smooth scenario is considered.
In this paper we present two different solutions to the problem of zero mode localization of ELKO spinor. In a recent paper the present authors reopened this problem since the solution presented before did not satisfy the boundary condition at the origin. The first solution is given by the introduction of a mass term and by coupling the spinor with the brane through a delta function. The second solution is reached by a Yukawa geometrical coupling with the Ricci scalar. This two models changes consistently the the boundary condition at infinity and at the origin. For the case of Geometrical coupling we are able to show that the zero mode is localized for any smooth version of the RS model.
We show that the statement in Yu-Xiao Liu, Xiang-Nan Zhou, Ke Yang and Feng-Wei Chen [Phys. Rev. D 86 , 064012 (2012)] that the zero mode of ELKO spinor is localized in some thin brane scenarios is not correct. This reopens the problem of localization of ELKO spinors.
In this work a study of the gravity is made using Einstein's equation in the post-Newtonian approach. This is a method to linearise the General Relativity indicated to treat non-relativistic objects. It enables us to construct, from metric-independent elements, fields that are governed by equations similar to the Maxwell's ones in Lorentz gauge. We promediate these equations for matter distributed in local systems, like solar systems or galaxies. Finally we define the large scale fields for this distribution, which includes terms analogous to electromagnetic case, like polarization, magnetization and superiors terms.
The general solution of Einstein's gravity equation in $D$ dimensions for an anisotropic and spherically symmetric matter distribution is calculated in a bulk with position dependent cosmological constant. Results for $n$ concentric $(D-2)-$branes with arbitrary mass, radius and pressure with different cosmological constant between branes are found. It is shown how the difference between the cosmological constant contributes to the effective mass of each brane, and it is also shown that the equation of state for each brane influences the dynamics of branes, which can be divided into eras according to the dominant matter. This scenario can be used to model the universe in the D=5 case, which may presents a richer phenomenology than the current models. The evolution law of the branes is studied, and the anisotropic pressure that remove divergences is found. The Randall-Sundrum metric in an outside region in the flat branes limit is also derived.
The Friedmann-Robertson-Walker metric with spherical topology is calculated as an effective metric at the brane in a multiple branes in $D-$dimensional spacetime scenario. In this model the radius of the brane is the cosmological scale factor, and its evolution is calculated from the viewpoint of the observers on their respective branes. The cosmology of the brane-universe is analyzed in cases where the anisotropic pressure has a cosmological constant like state equation. The pressure values needed to distinguish the oscillating, expanding or collapsing solutions are found, and the minimum value of a brane-universe mass to prevent a collapse into a black hole is also calculated. Finally the equation of motion is solved numerically in order to illustrate the different cosmological scenarios and to validate the analytical results.