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Rodrigo F. Sobreiro

Publications and source records attributed to Rodrigo F. Sobreiro.

At least 19 recordsLinked to original sources

Spontaneous symmetry breaking in a non-Abelian topological gauge theory

We study the spontaneous symmetry breaking mechanism in a non-Abelian topological gauge field theory, built from the twisted $\mathcal{N} = 2$ super-Yang-Mills theory in the presence of a Fujikawa-type potential. Specifically, by employing Fujikawa's Becchi-Rouet-Stora-Tyutin method, local degrees of freedom are released from the introduction of a potential in the trivial sector of equivariant cohomology. Such a potential displays a nontrivial vacuum solution, which induces the spontaneous symmetry breaking of the gauge symmetry together with the original fermionic scalar supersymmetry of the topological action. In this case, not only massive vector bosons emerge, but also fermionic fields with massive poles. This result shows that the introduction of a topological phase in non-Abelian gauge theories could provide a mechanism of mass generation for fermions with their masses correlated to the mass of Higgs gauge bosons ($m_B$). For the SSB in the topological case, three different vacuum directions are required. Otherwise, the supersymmetry could not be broken, and mass generation for fermions will not occur. Starting with a theory with symmetry $G = SU(N)$, to obtain a gauge theory at the end of the process, we must have $N \geq 3$. We study a maximal symmetry breaking of the type $SU(3) \rightarrow U(1) \times U(1)$, and obtain their fermionic propagators with mass poles $m^2_F = m^2_B = v^2$ after SSB, being $v^2 $ the energy scale introduced by the Fujikawa-type potential.

hep-th

Generating Jackiw-Teitelboim Euclidean gravity from static three-dimensional Maxwell-Chern-Simons electromagnetism

We consider pure three-dimensional Maxwell-Chern-Simons electrodynamics in the static limit. We show that this theory can be mapped onto a two-dimensional gravitational model in the first-order formalism of Riemannian manifolds with Euclidean signature, coupled to a real scalar field naturally interpreted as a dilaton. In this framework, the Newtonian and cosmological constants in two dimensions are fully determined by the electric charge. The solution to this gravitational model is found to be trivial: a constant dilaton field on a flat manifold. However, we introduce two distinct shifts of the spin-connection that transform the model into Jackiw-Teitelboim gravity. Specifically, we identify two additional solutions: a hyperbolic manifold with also a constant dilaton configuration; and a spherical manifold where, again, the dilaton assumes a constant, nonzero field configuration. In both non-flat cases, by employing the Gauss-Bonnet theorem in the specific cases of compact manifolds, we establish that the manifold's radius is fixed by the cosmological constant (and, therefore, by the electric charge).

hep-th

Topological symmetry-restored phase of gravity

In this work, we propose a topological quantum field theory phase for four-dimensional gravity. We show it is able to generate, not only General Relativity, but the whole family of Lovelock-Cartan theories of gravity. This is accomplished due to the existence of a topological symmetry which, when explicitly broken via the introduction of a mass scale, releases the local degrees of freedom of gravity. Additionally, we introduce an extended notion of the (anti-)self-dual Landau gauge conditions to evaluate the Ward identities, counterterms, and prove the quantum stability of the model, to all orders in perturbation theory, using the algebraic renormalization technique.

gr-qc

A relativistic non-perturbative local model of fractons and its non-local perturbative hidden sector

We construct, from first principles, a covariant local model for scalar fractonic matter coupled to a symmetric tensor gauge field. The free gauge field action is just the one of the Blasi-Maggiore model. The scalar sector, describing fracton charges, is a non-trivial covariant generalization of Pretko's quartic model. Because the model has no quadratic term in the scalar field, a direct perturbative treatment fails. Remarkably, by performing a suitable change of variables, we demonstrate that the action can be driven to a perturbative effective action. However, at the price of carrying non-local interacting terms. We study the perturbative regime of the model first by analyzing the classical field equations and some possible simple solutions, which are in accordance with the expected immobile behavior of fractons. We also derive the fracton dispersion relation and, by playing with the parameters of the model, show that there are at least six distinct phases: one with two massive fractonic modes, one of them being tachyonic; one with massless states associated with a long-range attractive potential; a mixed phase with one massive and one massless state; another one where physical states of the scalar field cannot occur at all in the physical spectrum; a massive phase with states of two different masses; and second phase where the scalar field cannot be associated with physical particles, in spite of its mass being real. Moreover, we find evidence that fractonic bound states emerge in the model for some of these phases.

hep-th

Unifying fractons, gravitons and photons from a gauge theoretical approach

We revisit the first principles gauge theoretical construction of relativistic gapless fracton theory developed by A.~Blasi and N.~Maggiore. The difference is that, instead of considering a symmetric tensor field, we consider a vector field with a gauge group index, \emph{i.e.} the usual Einstein-Cartan variable used in the first order formalism of gravity. After discussing the most general quadratic action for this field, we explore the physical sectors contained in the model. Particularly, we show that the model contains not only linear gravity and fractons, but also ordinary Maxwell equations, suggesting an apparent electrically charged phase of, for instance, spin liquids and glassy dynamical systems. Moreover, by a suitable change of field variables, we recover the Blasi-Maggiore gauge model of fractons and linear gravity.

hep-th

Relating electrodynamics and gravity in two Euclidean dimensions

Two-dimensional electrodynamics coupled to Dirac fermions is mapped onto two-dimensional gravity in the first-order formalism, also including fermions. However, the resulting fermion-gravity coupling deviates from the conventional form, explicitly violating parity and time-reversal symmetries. Additionally, these fermions exhibit an unconventional transformation behavior under $SO(2)$ transformations. Furthermore, we analyze the consistency of this mapping at the quantum level using the path integral formalism and Becchi-Rouet-Stora-Tyutin techniques. Our findings demonstrate that quantum electrodynamics and quantum gravity remain equivalent at the quantum level.

hep-th

Homological aspects of topological gauge-gravity equivalence

In the works of A. Achúcarro and P. K. Townsend and also by E. Witten, a duality between three-dimensional Chern-Simons gauge theories and gravity was established. In all cases, the results made use of the field equations. In a previous work, we were capable to generalize Witten's work to the off-shell cases, as well as to four dimensional Yang-Mills theory with de Sitter gauge symmetry. The price we paid is that curvature and torsion must obey some constraints under the action of the interior derivative. These constraints implied on the partial breaking of diffeomorphism invariance. In the present work, we, first, formalize our early results in terms of fiber bundle theory by establishing the formal aspects of the map between a principal bundle (gauge theory) and a coframe bundle (gravity) with partial breaking of diffeomorphism invariance. Then, we study the effect of the constraints on the homology defined by the interior derivative. The main result is the emergence of a nontrivial homology in Riemann-Cartan manifolds.

hep-th

Fermionic quantum gas at finite temperature within a Lorentz violating background

In this work we consider a fermionic quantum gas within a Lorentz-Violating background at finite temperature. We derive the effective action within Path Integral formalism considering the interaction of external electromagnetic field and Lorentz violating background fields with quantum fermions. To introduce the temperature effects, we employ the Matsubara formalism. Comments about the corresponding phenomenology are also made.

hep-th

Geometrodynamical description of two-dimensional electrodynamics

Two-dimensional pure electrodynamics is mapped into two-dimensional gravity in the first order formalism at classical and quantum levels. Due to the fact that the degrees of freedom of these two theories do not match, we are enforced to introduce extra fields from the beginning. These fields are introduced through a BRST exact boundary term, so they are harmless to the physical content of the theory. The map between electromagnetism and gravity fields generate a non-trivial Jacobian, which brings extra features (but also harmless to the physical content of the gravity theory) at quantum level.

hep-th

One-loop Schwinger effect in the presence of Lorentz-violating background fields

In this work we make use of proper-time method to evaluate Schwinger effect in the presence of Lorentz-violating background fields. Specifically, we evaluate the one-loop effective Lagrangian in the presence of Lorentz-violating time-like vector background $b_μ$ and pseud-scalar $m_5$ for the pure electric case. The imaginary part of the effective Lagrangian is computed in order to calculate the Schwinger effect. Comments on phenomenology are also performed.

hep-th

Towards background field independence within the Gribov horizon

We introduce a background gauge akin to the Landau-DeWitt gauge but deformed by the presence of a gauge parameter for the quantization of Euclidean Yang-Mills theories. In the limit where the background field vanishes, standard linear covariant gauges are recovered. This gauge allows for an explicit investigation of the effects of infinitesimal Gribov copies and their impact to background and gauge parameter dependence of physical correlators. Similarly to linear covariant gauges, the introduction of gauge-invariant dressed fields is essential to restore BRST symmetry. Hence, we construct a BRST symmetric action in linear covariant background gauges which eliminates regular infinitesimal Gribov copies in analogy to the recently introduced BRST invariant (refined) Gribov-Zwanziger action. The issue of background dependence and its relation to gauge parameter dependence is discussed in the light of non-perturbative effects driven by the elimination of Gribov copies.

hep-th

Carroll limit of four-dimensional gravity theories in the first order formalism

We explore the ultra-relativistic limit of a class of four dimensional gravity theories, known as Lovelock-Cartan gravities, in the first order formalism. First, we review the well known limit of the Einstein-Hilbert action. A very useful scale symmetry involving the vierbeins and the boost connection is presented. Moreover, we explore the field equations in order to find formal solutions. Some remarkable results are obtained: Riemann and Weitzenböck like manifolds are discussed; Birkhoff's theorem is verified for the torsionless case; an explicit solution with non-trivial geometry is discussed; A quite general solution in the presence of matter is obtained. Latter, we consider the ultra-relativistic limit of the more general Lovelock-Cartan gravity. The previously scale symmetry is also discussed. The field equations are studied in vacuum and in the presence of matter. In comparison with the Einstein-Hilbert case, a few relevant results are found: Birkhoff's theorem is also verified for the torsionless case; A quite general solution in the presence of matter is obtained. This solution generalizes the previous case; Riemann and Weitzenböck like manifolds are derived in the same lines of the Einstein-Hilbert case.

gr-qc

Correspondence between the twisted $N = 2$ super-Yang-Mills and conformal Baulieu-Singer theories

We characterize the correspondence between the twisted $N=2$ super-Yang-Mills theory and the Baulieu-Singer topological theory quantized in the self-dual Landau gauges. While the first is based on an on-shell supersymmetry, the second is based on an off-shell Becchi-Rouet-Stora-Tyutin symmetry. Because of the equivariant cohomology, the twisted $N=2$ in the ultraviolet regime and Baulieu-Singer theories share the same observables, the Donaldson invariants for 4-manifolds. The triviality of the Gribov copies in the Baulieu-Singer theory in these gauges shows that working in the instanton moduli space on the twisted $N=2$ side is equivalent to working in the self-dual gauges on the Baulieu-Singer one. After proving the vanishing of the $β$ function in the Baulieu-Singer theory, we conclude that the twisted $N=2$ in the ultraviolet regime, in any Riemannian manifold, is correspondent to the Baulieu-Singer theory in the self-dual Landau gauges -- a conformal gauge theory defined in Euclidean flat space.

hep-th

Non-relativistic limit of gravity theories in the first order formalism

We consider the non-relativistic limit of gravity in four dimensions in the first order formalism. First, we revisit the case of the Einstein-Hilbert action and formally discuss some geometrical configurations in vacuum and in the presence of matter at leading order. Second, we consider the more general Mardones-Zanelli action and its non-relativistic limit. The field equations and some interesting geometries, in vacuum and in the presence of matter, are formally obtained. Remarkably, in contrast to the Einstein-Hilbert limit, the set of field equations is fully determined because the boost connection appears in the action and field equations. It is found that the cosmological constant must disappear in the non-relativistic Mardones-Zanelli action at leading order. The conditions for Newtonian absolute time be acceptable are also discussed. It turns out that Newtonian absolute time can be safely implemented with reasonable conditions.

gr-qc

Hints of (de)confinement in Yang-Mills-Chern-Simons theories in the maximal Abelian gauge

The study of Yang-Mills theories in three dimensions is an insightful playground to grasp important features for the four-dimensional case. Additionally, in three dimensions, the Chern-Simons term can be introduced with a mass parameter of topological nature. Quantizing such a theory in the continuum demands a gauge fixing which, in general, is plagued by Gribov copies. In this work, Yang-Mills-Chern-Simons theories are quantized in the maximal Abelian gauge and the existence of infinitesimal Gribov copies is taken into account. The elimination of copies modifies the (Abelian) gluon propagator leading to two different phases: one in which all poles are complex and thus interpreted as a confining phase and another where an excitation which can be part of the physical spectrum is present.

hep-th

Constrained gauge-gravity duality in three and four dimensions

The equivalence between Chern-Simons and Einstein-Hilbert actions in three dimensions established by A.~Achúcarro and P.~K.~Townsend (1986) and E.~Witten (1988) is generalized to the off-shell case. The technique is also generalized to the Yang-Mills action in four dimensions displaying de Sitter gauge symmetry. It is shown that, in both cases, we can directly identify a gravity action while the gauge symmetry can generate spacetime local isometries as well as diffeomorphisms. The price we pay for working in an off-shell scenario is that specific geometric constraints are needed. These constraints can be identified with foliations of spacetime. The special case of spacelike leafs evolving in time is studied. Finally, the whole set up is analyzed under fiber bundle theory. In this analysis we show that a traditional gauge theory, where the gauge field does not influence in spacetime dynamics, can be (for specific cases) consistently mapped into a gravity theory in the first order formalism.

hep-th

Lorentz-violating Yang-Mills theory: discussing the Chern-Simons-like term generation

We analyze the Chern-Simons-like term generation in the CPT-odd Lorentz-violating Yang-Mills theory interacting with fermions. Moreover, we study the anomalies of this model as well as its quantum stability. The whole analysis is performed within the algebraic renormalization theory, which is independent of the renormalization scheme. In addition, all results are valid to all orders in perturbation theory. We find that the Chern-Simons-like term is not generated by radiative corrections, just like its Abelian version. Additionally, the model is also free of gauge anomalies and quantum stable.

hep-th

Gauge anomalies in Lorentz-violating QED

In this work we study the issue of gauge anomalies in Lorentz-violating QED. To do so, we opt to use the Becchi-Rouet-Stora-Tyutin formalism within the algebraic renormalization approach, reducing our study to a cohomology problem. Since this approach is independent of the renormalization scheme, the results obtained here are expected to be general. We find that the Lorentz-violating QED is free of gauge anomalies to all orders in perturbation theory.

hep-th