arXiv subjects

R. Bufalo

Publications and source records attributed to R. Bufalo.

At least 37 records · Page 2Linked to original sources

arXiv2020

Induced Maxwell-Chern-Simons Effective Action in Very Special Relativity

In this paper, we study the one-loop induced photon's effective action in the very special relativity electrodynamics in $(2+1)$ spacetime (VSR-QED$_{3}$). Due to the presence of new nonlocal couplings resulting from the VSR gauge symmetry, we have additional graphs contributing to the $\langle AA\rangle$ and $\langle AAA \rangle$ amplitudes. From these contributions, we discuss the VSR generalization of the Abelian Maxwell-Chern-Simons Lagrangian, consisting in the dynamical part and the Chern-Simons-like self-couplings, respectively. We use the VSR-Chern-Simons electrodynamics to discuss some non-Ohmic behavior on topological materials, in particular VSR effects on Hall's conductivity. In the dynamical part of the effective action, we observe the presence of a UV/IR mixing, due to the entanglement of the VSR nonlocal effects to the quantum higher-derivative terms. Furthermore, in the self-coupling aspect, we verify the validity of the Furry's theorem in the VSR-QED$_{3}$ explicitly.

hep-th↗

arXiv2020

One-loop Photon's Effective Action in the Noncommutative Scalar QED$_{3}$

In this paper, we consider the evaluation of the effective action for photons coupled to charged scalar fields in the framework of a $(2+1)$-dimensional noncommutative spacetime. In order to determine the noncommutative Maxwell Lagrangian density, we follow a perturbative approach, by integrating out the charged scalar fields, to compute the respective graphs for the vev's $\left\langle AA \right\rangle$, $\left\langle AAA \right\rangle$ and $\left\langle AAAA \right\rangle$. Surprisingly, it is shown that these contributions are planar and that, in the highly noncommutative limit, correspond to the Maxwell effective action and its higher-derivative corrections. It is explicitly verified that the one-loop effective action is gauge invariant, as well as under discrete symmetries: parity, time reversal and charge conjugation. Moreover, a comparison of the main results with the noncommutative QED$_{3}$ is established. In particular, the main difference is the absence of parity violating terms in the photon's effective action coming from integrating out the charged scalar fields.

hep-th↗

arXiv2019

Tree-level processes in very special relativity

In this paper we discuss the Bhabha and Compton scattering for the quantum electrodynamics defined in the framework of very special relativity (VSR). The main aspect of the VSR setting is that it admits different types of interactions appearing in a nonlocal form due to the modified gauge invariance. We explore the richness of these new couplings in the evaluation of the differential cross-section for these tree-level processes. We assess the behavior of the leading VSR Lorentz violation modifications by considering some special limits for the Bhabha and Compton cross-section expressions.

hep-th↗

arXiv2019

Thermal effects of Very Special Relativity Quantum Electrodynamics

In this paper we compute the high-temperature effective Lagrangian for the quantum electrodynamics defined in the framework of Very Special Relativity (VSR). The main aspect of the VSR setting is that it modifies the gauge invariance, admitting now different types of interactions appearing in a nonlocal form. In order to explore the richness of these new couplings, we employ the usual Matsubara imaginary-time formalism to evaluate the effective Lagrangian at one and two-loop order. We illustrate the leading VSR Lorentz violation modifications by computing high-temperature internal energy density and establishing a comparison with the expected contribution.

hep-th↗

arXiv2018

Noncommutative Jackiw-Pi model: One-loop renormalization

In this paper, we study the quantum behavior of the noncommutative Jackiw-Pi model. After establishing the Becchi-Rouet-Store-Tyutin (BRST) invariant action, the perturbative renormalizability is discussed, allowing us to introduce the renormalized mass and gauge coupling. We then proceed to compute the one-loop correction to the basic 1PI functions, necessary to determine the renormalized parameters (mass and charge), next we discuss the physical behaviour of these parameters.

hep-th↗

arXiv2018

Radiative Corrections in GSDKP

We show explicit the first radiative correction for the vertex and photon-photon 4-point function in Generalized Scalar Duffin-Kemmer-Petiau Quantum Electrodynamcis (GSDKP), utilizing the dimensional regularization method, where the gauge symmetry is manifest. As we shall see one of the consequences of the study is that the DKP algebra ensures the functioning of theWard- Takahashi-Fradkin (WTF) identities in the first radiative corrections prohibiting certain ultraviolet (UV) divergences. This result leads us to ask whether this connection between DKP algebra, UV divergences, and quantum gauge symmetry (WTF) is a general statment.

physics.gen-ph↗

arXiv2018

Perturbative effective action for the photon in noncommutative QED$_{2}$ and exactness of the Schwinger mass

In this paper, we discuss the noncommutative QED$_2$ in the S-matrix framework. We are interested in perturbatively proving that the exact Schwinger mass $μ^2=\frac{e^2}π$ does not receive noncommutative corrections to any order in loop expansion. In this sense, the S-matrix approach is useful since it allows us to work with the effective action $Γ[A]$ (interaction term) to compute the corresponding gauge field 1PI two-point function at higher orders. Furthermore, by means of $α^*$-cohomology, we generalize the QED$_2$ S-matrix analysis in the Moyal star product to all translation-invariant star products.

hep-th↗

arXiv2017

Normalizability analysis of the generalized quantum electrodynamics from the causal point of view

The causal perturbation theory is an axiomatic perturbative theory of the S-matrix. This formalism has as its essence the following axioms: causality, Lorentz invariance and asymptotic conditions. Any other property must be showed via the inductive method order-by-order and, of course, it depends on the particular physical model. In this work we shall study the normalizability of the generalized quantum electrodynamics in the framework of the causal approach. Furthermore, we analyse the implication of the gauge invariance onto the model and obtain the respective Ward-Takahashi-Fradkin identities.

hep-th↗

arXiv2017

Axion Mass Bound in Very Special Relativity

In this paper we propose a very special relativity (VSR)-inspired description of the axion electrodynamics. This proposal is based upon the construction of a proper study of the SIM$(2)$--VSR gauge-symmetry. It is shown that the VSR nonlocal effects give a health departure from the usual axion field theory. The axionic classical dynamics is analysed in full detail, first by a discussion of its solution in the presence of an external magnetic field. Next, we compute photon-axion transition in VSR scenario by means of Primakoff interaction, showing the change of a linearly polarized light to a circular one. Afterwards, duality symmetry is discussed in the VSR framework.

hep-th↗

arXiv2017

One-loop $\mathbfβ$ function of noncommutative scalar $QED_{4}$

In this paper, we consider the $β$ function at one-loop approximation for noncommutative scalar QED. The renormalization of the full theory, including the basic vertices, and the renormalization group equation are fully established. Next, the complete set of the one-loop diagrams corresponding to the first-order radiative corrections to the basic functions is considered: gauge, charged scalar and ghost fields self-energies, and three- and four-point vertex functions $\left<ϕ^†ϕA\right>$ and $\left<ϕ^†ϕA A\right>$, respectively. We pay special attention to the noncommutative contributions to the renormalization constants. To conclude, the one-loop $β$ function of noncommutative scalar QED is then computed and comparison to known results is presented.

hep-th↗

arXiv2017

Three-dimensional noncommutative Yukawa theory: Induced effective action and propagating modes

In this paper, we establish the analysis of noncommutative Yukawa theory, encompassing neutral and charged scalar fields. We approach the analysis by considering carefully the derivation of the respective effective actions. Hence, based on the obtained results, we compute the one-loop contributions to the neutral and charged scalar field self-energy, as well as to the Chern-Simons polarization tensor. In order to properly define the behaviour of the quantum fields, the known UV/IR mixing due to radiative corrections is analysed in the one-loop physical dispersion relation of the scalar and gauge fields.

hep-th↗

arXiv2017

BRST Quantization of Unimodular Gravity

We study the quantization of two versions of unimodular gravity, namely, fully diffeomorphism-invariant unimodular gravity and unimodular gravity with fixed metric determinant utilizing standard path integral approach. We derive the BRST symmetry of effective actions corresponding to several relevant gauge conditions. We observe that for some gauge conditions, the restricted gauge structure may complicate the formulation and effective actions, in particular, if the chosen gauge conditions involve the canonical momentum conjugate to the induced metric on the spatial hypersurface. The BRST symmetry is extended further to the finite field-dependent BRST transformation, in order to establish the mapping between different gauge conditions in each of the two versions of unimodular gravity.

hep-th↗

arXiv2016

Thermal effects of a photon gas with a deformed Heisenberg algebra

In this paper we have consider the thermodynamics of a photon gas subject to the presence of a minimal measurable length following from a covariant extension of the original generalized uncertainty principle (GUP). After establishing consistently a generalized dynamics, we define a GUP deformed Maxwell invariant which serves as the basis for our study. In order to highlight the GUP effects we compute the one- and two-loop order contribution to the partition function at the high-temperature limit. Afterwards, by computing the internal energy density we conclude that the additional terms can be seen as corrections $δσ_{\rm{gup}}$ to the Stefan-Boltzmann law due to GUP effects.

hep-th↗

arXiv2016

Canonical formulation and path integral for local vacuum energy sequestering

We establish the Hamiltonian analysis and the canonical path integral for a local formulation of vacuum energy sequestering. In particular, by considering the state of the universe as a superposition of vacuum states corresponding to different values of the cosmological and gravitational constants, the path integral is extended to include integrations over the cosmological and gravitational constants. The result is an extension of the Ng-van Dam form of the path integral of unimodular gravity. It is argued to imply a relation between the fraction of the most likely values of the gravitational and cosmological constants and the average values of the energy density and pressure of matter over spacetime. Finally, we construct and analyze a BRST-exact formulation of the theory, which can be considered as a topological field theory.

hep-th↗

arXiv2016

Noncommutative Maxwell-Chern-Simons theory (I): One-loop dispersion relation analysis

In this paper, we study the three-dimensional noncommutative Maxwell-Chern-Simons theory. In the present analysis, a complete account for the gauge field two-point function renormalizability is presented and physical significant quantities are carefully established. The respective form factor expressions from the gauge field self-energy are computed at one-loop order. More importantly, an analysis of the gauge field dispersion relation, in search of possible noncommutative anomalies and infrared finiteness, is performed for three special cases, with particular interest in the highly noncommutative limit.

hep-th↗

arXiv2016

SIM$(1)$--VSR Maxwell-Chern-Simons electrodynamics

In this paper we propose a very special relativity (VSR)-inspired generalization of the Maxwell-Chern-Simons (MCS) electrodynamics. This proposal is based upon the construction of a proper study of the SIM$(1)$--VSR gauge-symmetry. It is shown that the VSR nonlocal effects present a significant and health departure from the usual MCS theory. The classical dynamics is analysed in full detail, by studying the solution for the electric field and static energy for this configuration. Afterwards, the interaction energy between opposite charges are derived and we show that the VSR effects play an important part in obtaining a (novel) finite expression for the static potential.

hep-th↗

arXiv2015

Functional quantization of Generalized Scalar Duffin-Kemmer-Petiau Electrodynamics

The main goal of this work is to study systematically the quantum aspects of the interaction between scalar particles in the framework of Generalized Scalar Duffin-Kemmer-Petiau Electrodynamics (GSDKP). For this purpose the theory is quantized after a constraint analysis following Dirac's methodology by determining the Hamiltonian transition amplitude. In particular, the covariant transition amplitude is established in the generalized non-mixing Lorenz gauge. The complete Green's functions are obtained through functional methods and the theory's renormalizability is also detailed presented. Next, the radiative corrections for the Green's functions at $α$-order are computed; and, as it turns out, an unexpected $m_{P}$-dependent divergence on the DKP sector of the theory is found. Furthermore, in order to show the effectiveness of the renormalization procedure on the present theory, a diagrammatic discussion on the photon self-energy and vertex part at $α^{2}$-order are presented, where it is possible to observe contributions from the DKP self-energy function, and then analyse whether or not this novel divergence propagates to higher-order contributions. Lastly, an energy range where the theory is well defined: $m^{2}\ll k^{2}<m_{p}^{2}$ was also found by evaluating the effective coupling for the GSDKP.

hep-th↗

arXiv2015

How unimodular gravity theories differ from general relativity at quantum level

We investigate path integral quantization of two versions of unimodular gravity. First a fully diffeomorphism-invariant theory is analyzed, which does not include a unimodular condition on the metric, while still being equivalent to other unimodular gravity theories at the classical level. The path integral has the same form as in general relativity (GR), except that the cosmological constant is an unspecified value of a variable, and it thus is unrelated to any coupling constant. When the state of the universe is a superposition of vacuum states, the path integral is extended to include an integral over the cosmological constant. Second, we analyze the standard unimodular theory of gravity, where the metric determinant is fixed by a constraint. Its path integral differs from the one of GR in two ways: the metric of spacetime satisfies the unimodular condition only in average over space, and both the Hamiltonian constraint and the associated gauge condition have zero average over space. Finally, the canonical relation between the given unimodular theories of gravity is established.

hep-th↗