arXiv subjects

Helios Sanchis-Alepuz

Publications and source records attributed to Helios Sanchis-Alepuz.

At least 19 recordsLinked to original sources

arXiv2022

Glueballs from bound state equations

Glueballs are bound states in the spectrum of quantum chromodynamics which consist only of gluons. They belong to the group of exotic hadrons which are widely studied experimentally and theoretically. We summarize how to calculate glueballs in a functional framework and discuss results for pure Yang-Mills theory. Our setup is totally self-contained with the scale being the only external input. We enumerate a range of tests that provide evidence of the stability of the results. This illustrates the potential of functional equations as a continuum first-principles method complementary to lattice calculations.

hep-ph↗

arXiv2022

Approximating the full-field temperature evolution in 3D electronic systems from randomized "Minecraft" systems

Neural Networks as fast physics simulators have a large potential for many engineering design tasks. Prerequisites for a wide-spread application are an easy-to-use workflow for generating training datasets in a reasonable time, and the capability of the network to generalize to unseen systems. In contrast to most previous works where training systems are similar to the evaluation dataset, we propose to adapt the type of training system to the network architecture. Specifically, we apply a fully convolutional network and, thus, design 3D systems of randomly located voxels with randomly assigned physical properties. The idea is tested for the transient heat diffusion in electronic systems. Training only on random "Minecraft" systems, we obtain good generalization to electronic systems four times as large as the training systems (one-step prediction error of 0.07% vs 0.8%).

physics.comp-ph↗

arXiv2022

Towards Real Time Thermal Simulations for Design Optimization using Graph Neural Networks

This paper presents a method to simulate the thermal behavior of 3D systems using a graph neural network. The method discussed achieves a significant speed-up with respect to a traditional finite-element simulation. The graph neural network is trained on a diverse dataset of 3D CAD designs and the corresponding finite-element simulations, representative of the different geometries, material properties and losses that appear in the design of electronic systems. We present for the transient thermal behavior of a test system. The accuracy of the network result for one-step predictions is remarkable (\SI{0.003}{\%} error). After 400 time steps, the accumulated error reaches \SI{0.78}{\%}. The computing time of each time step is \SI{50}{ms}. Reducing the accumulated error is the current focus of our work. In the future, a tool such as the one we are presenting could provide nearly instantaneous approximations of the thermal behavior of a system that can be used for design optimization.

cs.CE↗

arXiv2022

Elucidating the rho-meson's role as intermediate resonance in the time-like electromagnetic pion form factor

Motivated by the planned measurements of the time-like electromagnetic proton form factors an exploratory study of the time-like electromagnetic pion form factor is presented in a formalism which describes mesons as Poincaré-invariant bound states. In the respective quark interaction kernel, beyond the gluon-intermediated interactions for valence-type quarks, non-valence effects are included by allowing the pions to couple back in a self-consistent manner to the quarks. Consequently, the opening of the dominant $ρ$ decay channel, $ρ\to ππ$, and the presence of a multi-particle branch cut, setting in when the two-pion threshold is crossed, are included consistently, first in the correspondingly calculated quark-photon vertex, and then consequently in the time-like electromagnetic pion form factor. The obtained results are in agreement with the available experimental data and provide further evidence for the efficacy of a vector-meson dominance model. Effects of going beyond the here employed isospin-symmetric limit are discussed. Last but not least, an outlook is provided on how to include in Poincaré-covariant Faddeev approaches the effects of intermediate resonances in the calculation of baryon properties.

hep-ph↗

arXiv2022

Higher spin glueballs from functional methods

We calculate the glueball spectrum for spin up to J=4 and positive charge parity in pure Yang-Mills theory. We construct the full bases for J=0,1,2,3,4 and discuss the relation to gauge invariant operators. Using a fully self-contained truncation of Dyson-Schwinger equations as input, we obtain ground states and first and second excited states from extrapolations of the eigenvalue curves. Where available, we find good quantitative agreement with lattice results.

hep-ph↗

arXiv2018

Recent developments in bound-state calculations using the Dyson-Schwinger and Bethe-Salpeter equations

We review in detail modern numerical methods used in the determination and solution of Bethe-Salpeter and Dyson--Schwinger equations. The algorithms and techniques described are applicable to both the rainbow-ladder truncation and its non-trivial extensions. We discuss pedagogically the steps involved in constructing conventional mesons and baryons as systems of two- and three-quarks respectively. As further application we describe the self-consistent calculation of form-factors and highlight the challenges that remain therein.

hep-ph↗

arXiv2018

Electromagnetic transition form factors of baryons in a relativistic Faddeev approach

The covariant Faddeev approach which describes baryons as relativistic three-quark bound states and is based on the Dyson-Schwinger and Bethe-Salpeter equations of QCD is briefly reviewed. All elements, including especially the baryons' three-body-wave-functions, the quark propagators and the dressed quark-photon vertex, are calculated from a well-established approximation for the quark-gluon interaction. Selected previous results of this approach for the spectrum and elastic electromagnetic form factors of ground-state baryons and resonances are reported. The main focus of this talk is a presentation and discussion of results from a recent investigation of the electromagnetic transition form factors between ground-state octet and decuplet baryons as well as the octet-only $Σ^0$ to $Λ$ transition.

hep-ph↗

arXiv2017

Electromagnetic transition form factors of baryons in the space-like momentum region

We present results from a calculation of the electromagnetic transition form factors between ground-state octet and decuplet baryons as well as the octet-only $Σ^0$ to $Λ$ transition. We work in the combined framework of Dyson-Schwinger equations and covariant Bethe-Salpeter equations with all elements, the baryon three body wave function, the quark propagators and the dressed quark-photon vertex determined from a well-established, momentum dependent approximation for the quark-gluon interaction. We discuss in particular the similarities among the different transitions as well as the differences induced by SU(3)-isospin symmetry breaking. We furthermore provide estimates for the slopes of the electric and magnetic $Σ^0$ to $Λ$ transitions at the zero photon momentum point.

hep-ph↗

arXiv2016

Baryons as relativistic three-quark bound states

We review the spectrum and electromagnetic properties of baryons described as relativistic three-quark bound states within QCD. The composite nature of baryons results in a rich excitation spectrum, whilst leading to highly non-trivial structural properties explored by the coupling to external (electromagnetic and other) currents. Both present many unsolved problems despite decades of experimental and theoretical research. We discuss the progress in these fields from a theoretical perspective, focusing on nonperturbative QCD as encoded in the functional approach via Dyson-Schwinger and Bethe-Salpeter equations. We give a systematic overview as to how results are obtained in this framework and explain technical connections to lattice QCD. We also discuss the mutual relations to the quark model, which still serves as a reference to distinguish 'expected' from 'unexpected' physics. We confront recent results on the spectrum of non-strange and strange baryons, their form factors and the issues of two-photon processes and Compton scattering determined in the Dyson-Schwinger framework with those of lattice QCD and the available experimental data. The general aim is to identify the underlying physical mechanisms behind the plethora of observable phenomena in terms of the underlying quark and gluon degrees of freedom.

hep-ph↗

arXiv2016

On light baryons and their excitations

We study ground states and excitations of light octet and decuplet baryons within the framework of Dyson-Schwinger and Faddeev equations. We improve upon similar approaches by explicitly taking into account the momentum-dependent dynamics of the quark-gluon interaction that leads to dynamical chiral symmetry breaking. We perform calculations in both the three-body Faddeev framework and the quark-diquark approximation in order to assess the impact of the latter on the spectrum. Our results indicate that both approaches agree well with each other. The resulting spectra furthermore agree one-to-one with experiment, provided well-known deficiencies of the rainbow-ladder approximation are compensated for. We also discuss the mass evolution of the Roper and the excited Delta with varying pion mass and analyse the internal structure in terms of their partial wave decompositions.

hep-ph↗

arXiv2016

Hyperon elastic electromagnetic form factors in the space-like momentum region

We present a calculation of the electric and magnetic form factors of ground-state octet and decuplet baryons including strange quarks. We work with a combination of Dyson-Schwinger equations for the quark propagator and covariant Bethe-Salpeter equations describing baryons as bound states of three (non-perturbative) quarks. Our form factors for the octet baryons are in good agreement with corresponding lattice data at finite $Q^2$; deviations in some isospin channels for the magnetic moments can be explained by missing meson cloud effects. At larger $Q^2$ our quark core calculation has predictive power for both, the octet and decuplet baryons.

hep-ph↗

arXiv2015

Probing the quark-gluon interaction with hadrons

We present a unified picture of mesons and baryons in the Dyson-Schwinger/Bethe-Salpeter approach, wherein the quark-gluon and quark-(anti)quark interaction follow from a systematic truncation of the QCD effective action and includes all its tensor structures. The masses of some of the ground state mesons and baryons are found to be in reasonable agreement with the expectations of a `quark-core calculation', suggesting a partial insensitivity to the details of the quark-gluon interaction. However, discrepancies remain in the meson sector, and for excited baryons, that suggest higher order corrections are relevant and should be investigated following the methods outlined herein.

hep-ph↗

arXiv2015

Hadronic Observables from Dyson-Schwinger and Bethe-Salpeter equations

In these proceedings we present a mini-review on the topic of the Dyson-Schwinger/Bethe-Salpeter approach to the study of relativistic bound-states in physics. In particular, we present a self-contained discussion of their derivation, as well as their truncation such that important symmetries are maintained.

hep-ph↗

arXiv2015

Glueballs from the Bethe-Salpeter equation

We formulate a framework to determine the mass of glueball states of Landau gauge Yang-Mills theory in the continuum. To this end we derive a Bethe-Salpeter equation for two gluon bound states including the effects of Faddeev-Popov ghosts. We construct a suitable approximation scheme such that the interactions in the bound state equation match a corresponding successful approximation of the Dyson-Schwinger equations for the Landau gauge ghost and gluon propagators. Based upon a recently obtained solution for the propagators in the complex momentum plane we obtain results for the mass of the scalar and pseudoscalar glueballs. In the scalar channel we find a mass value in agreement with lattice gauge theory.

hep-ph↗

arXiv2014

Electromagnetic baryon form factors in the Poincare-covariant Faddeev approach

Baryons are treated as three-quark systems using QCD degrees of freedom in Poincare-covariant bound-state equations. The quark self-energy as well as the interaction between quarks are approximated by a vector-vector interaction via a single dressed-gluon exchange (rainbow-ladder truncation), thereby allowing a unified study of quark, meson and baryon properties. Here we will focus on the calculation of electromagnetic properties of spin-1/2 and spin-3/2 ground state baryons.

hep-ph↗

arXiv2014

Octet and Decuplet masses: a covariant three-body Faddeev calculation

We determine the baryon octet and decuplet masses as well as their wave functions in a covariant three-body Faddeev approach. We work in an approximation where irreducible three-body forces are neglected. In the two-body interactions we take into account a well explored rainbow-ladder kernel as well as flavor dependent meson-exchange terms motivated from the underlying quark-gluon interaction. Without flavor dependent forces we find agreement with the experimental spectrum on the 5-10 percent level. Including the flavor dependent terms on an exploratory level delivers a Sigma/Lambda splitting with the correct sign although the magnitude is still too small.

hep-ph↗

arXiv2014

Geonic black holes and remnants in Eddington-inspired Born-Infeld gravity

We show that electrically charged solutions within the Eddington-inspired Born-Infeld theory of gravity replace the central singularity by a wormhole supported by the electric field. As a result, the total energy associated with the electric field is finite and similar to that found in the Born-Infeld electromagnetic theory. When a certain charge-to-mass ratio is satisfied, in the lowest part of the mass and charge spectrum the event horizon disappears yielding stable remnants. We argue that quantum effects in the matter sector can lower the mass of these remnants from the Planck scale down to the TeV scale.

hep-th↗

arXiv2014

Pion cloud effects on baryon masses

In this work we explore the effect of pion cloud contributions to the mass of the nucleon and the delta baryon. To this end we solve a coupled system of Dyson-Schwinger equations for the quark propagator, a Bethe-Salpeter equation for the pion and a three-body Faddeev equation for the baryons. In the quark-gluon interaction we explicitly resolve the term responsible for the back-coupling of the pion onto the quark, representing rainbow-ladder like pion cloud effects in bound states. We study the dependence of the resulting baryon masses on the current quark mass and discuss the internal structure of the baryons in terms of a partial wave decomposition. We furthermore determine values for the nucleon and delta sigma-terms.

hep-ph↗