arXiv subjects

Leonardo P. G. De Assis

Publications and source records attributed to Leonardo P. G. De Assis.

5 recordsLinked to original sources

arXiv2026

Revealing Gauge Constraints in LQG-Inspired Yang-Mills Theory

The consistent embedding of Loop Quantum Gravity (LQG) effects within the Standard Model requires a rigorous understanding of how Planck-scale deformations manifest at low energies. While phenomenological approaches often introduce canonical deformations with multiple free parameters to capture these effects, the physical requirement of gauge symmetry in the framework of a covariant Effective Field Theory (EFT) imposes strict conditions on the allowed interaction structure. In this paper, we demonstrate that these conditions act as physical selection rules for admissible quantum gravity models. By applying non-Abelian Ward identities and a covariant operator mapping to the dimension-six operator basis, we derive a fundamental on-shell equivalence between kinetic and cubic interaction terms. As a paradigmatic application, we show that the Levy-Helayel-Neto (LHN) framework, a candidate effective description of LQG, satisfies this physical requirement only when its parameters obey the specific algebraic relation: theta_3 / theta_8 = -1/2 * [ 1 + theta_7 * (ell_P / L)^(2 + 2 Upsilon) ] + O(ell_P). It must be highlighted that this result advances the physical understanding of LQG phenomenology by revealing that the apparent freedom in defining the Hamiltonian is illusory; the parameters are bound by the necessity of preserving the gauge structure of the Standard Model.

physics.gen-ph↗

arXiv2026

Constructing Dimension-8 SMEFT from Conserved Currents

Effective Field Theories (EFTs) are the primary tool for interpreting precision collider data in the absence of new resonances. However, in the dimension-8 Standard Model Effective Field Theory (SMEFT), the utility of traditional algebraically minimal bases is fundamentally limited by kinematic mixing: multiple operators contribute to a single high-energy amplitude, creating degeneracies that obscure ultraviolet interpretations and complicate the application of theoretical constraints. We introduce a generative framework that resolves this by constructing operators directly from the conserved Noether currents of the Standard Model. The resulting Kinematically Diagonalized Current Basis (KDCB) ensures that each operator maps to a unique asymptotic energy scaling ($E^4$, $E^2$, $E^0$) in scattering amplitudes. This organization makes S-matrix positivity bounds manifest, enables a stable auxiliary-field formulation for Monte Carlo simulation, and provides direct diagnostics for universal versus non-universal ultraviolet completions through current decomposition. By rotating the operator space into physically interpretable sectors, the KDCB offers a transformative framework for global fits and a clear pathway from high-energy data to the structure of new physics.

hep-ph↗

arXiv2014

Vortex Solutions and a Novel Role for R-parity in an N=2-Supersymmetric Model for Graphene

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.

hep-th↗

arXiv2012

A non-equilibrium picture of the chemical freeze-out in hadronic thermal models

Thermal models have proven to be an useful and simple tool used to make theoretical predictions and data analysis in relativistic and ultra-relativistic heavy ion collisions. A new version of these models is presented here, incorporating a non equilibrium feature to the description of the intermediate fireball state formed at the chemical freeze-out. Two different effective temperatures are attributed to the expanding fireball, regarding its baryonic and mesonic sectors. The proposal is not merely to include an additional degree of freedom to reach a better adjustment to the data, but to open a room in the model conception for considerations on the non-equilibrium scenario of the system evolution. A set of well consolidated data for particles production is used to validated the reformulated version of thermal models presented here. A rather good performance of the extended version was verified, both for the quality of particle ratio data fittings as well as for describing the asymptotic energy behavior of temperatures and baryochemical potential of the colliding nuclear system.

nucl-th↗

arXiv2012

Nuclear evaporation process with simultaneous multiparticle emission

The nuclear evaporation process is reformulated by taking into account simultaneous multiparticle emission from a hot compound nucleus appearing as an intermediate state in many nuclear reaction mechanisms. The simultaneous emission of many particles is particularly relevant for high excitation energy of the compound nucleus.These channels are effectively open in competition with the single particle emissions and fission in this energy regime. Indeed, the inclusion of these channels along the decay evaporating chain shows that the yield of charged particles and occurrence of fission are affected by these multiparticle emission processes of the compounded nucleus, when compared to the single sequential emission results. The effect also shows a qualitative change in the neutron multiplicity of different heavy compound nucleus considered. This should be an important aspect for the study of spallation reaction in Acceleration Driven System (ADS) reactors. The majority of neutrons generated in these reactions come from the evaporation stage of the reaction, the source of neutron for the system. A Monte Carlo simulation is employed to determine the effect of these channels on the particle yield and fission process. The relevance of the simultaneous particle emission with the increasing of excitation energy of the compound nucleus is explicitly shown.

nucl-th↗