# Helios Sanchis AlepuzKarl-Franzens-Universität Graz | KFU Graz · Department of Theoretical Physics

Helios Sanchis Alepuz

PhD

## About

74

Publications

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1,654

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Introduction

Additional affiliations

August 2012 - August 2015

January 2011 - present

**Karl-Franzens-Universität Graz**

January 2007 - December 2008

## Publications

Publications (74)

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...

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...

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 syste...

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, represent...

We study electromagnetic as well as strong isospin breaking effects in the isospin mass splittings of light pseudoscalar and vector mesons. To this end we employ a coupled system of quark Dyson-Schwinger and meson Bethe-Salpeter equations whose interaction kernels contain gluon, pion and photon exchange interactions. In bound states, QCD-induced is...

The spectrum of glueballs with quantum numbers JPC = 0±+, 2±+, 3±+, 4±+ is calculated in quenched quantum chromodynamics (QCD) from bound state equations. The input is taken from a parameter-free calculation of two- and three-point functions. Our results agree well with lattice results where available and contain also some additional states. For th...

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 Poincar\'e-invariant bound states. In the respective quark interaction kernel, beyond the gluon-intermediated interactions for valence...

We study electromagnetic as well as strong isospin breaking effects in the isospin mass splittings of light pseudoscalar and vector mesons. To this end we employ a coupled system of quark Dyson-Schwinger and meson Bethe-Salpeter equations whose interaction kernels contain gluon, pion and photon exchange interactions. In bound states, QCD-induced is...

Thermal simulations are an important part of the design process in many engineering disciplines. In simulation-based design approaches, a considerable amount of time is spent by repeated simulations. An alternative, fast simulation tool would be a welcome addition to any automatized and simulation-based optimisation workflow. In this work, we prese...

The spectrum of glueballs with quantum numbers $J^\mathsf{PC}=0^{\pm+},2^{\pm+},3^{\pm+},4^{\pm+}$ is calculated in quenched quantum chromodynamics from bound state equations. The input is taken from a parameter-free calculation of two- and three-point functions. Our results agree well with lattice results where available and contain also some addi...

We give an overview of results for the quenched glueball spectrum from two-body bound state equations based on the 3PI effective action. The setup, which uses self-consistently calculated two- and three-point functions as input, is completely self-contained and does not have any free parameters except for the coupling. The results for J PC = 0 ±+ ,...

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-t...

Thermal simulations are an important part in the design of electronic systems, especially as systems with high power density become common. In simulation-based design approaches, a considerable amount of time is spent by repeated simulations. In this work, we present a proof-of-concept study of the application of convolutional neural networks to ac...

We calculate the glueball spectrum for spin up to $$J=$$ J = 4 and positive charge parity in pure Yang–Mills theory. We construct the full bases for $$J=$$ 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 seco...

We give an overview of results for the quenched glueball spectrum from two-body bound state equations based on the 3PI effective action. The setup, which uses self-consistently calculated two- and three-point functions as input, is completely self-contained and does not have any free parameters except for the coupling. The results for $J^{\mathsf{P...

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. W...

We study solutions of the stellar structure equations for spherically symmetric objects in modified theories of gravity, where the Einstein-Hilbert Lagrangian is replaced by f(R)=R+αR2 and f(R,Q)=R+αR2+βQ, with R being the Ricci scalar curvature, Q=RμνRμν and Rμν the Ricci tensor. We work in the Palatini formalism, where the metric and the connecti...

An exploratory study of the timelike pion electromagnetic form factor in a Poincaré-covariant bound state formalism in the isospin symmetric limit is presented. Starting from a quark interaction kernel representing gluon-intermediated interactions for valence-type quarks, nonvalence effects are included by introducing pions as explicit degrees of f...

An exploratory study of the time-like pion electromagnetic form factor in a Poincar\'e-covariant bound state formalism in the isospin symmetric limit is presented. Starting from a quark interaction kernel representing gluon-intermediated interactions for valence-type quarks, non-valence effects are included by introducing pions as explicit degrees...

We study solutions of the stellar structure equations for spherically symmetric objects in Palatini $f(R)=R+\alpha R^2$ and $f(R,Q)=R+\alpha R^2+\beta Q$ in the mass-radius region associated to neutron stars. We illustrate the potential impact of the $R^2$ and $Q$ terms by studying a range of viable values of $\alpha$ and $\beta$. Similarly, we use...

We provide results for the spectrum of scalar and pseudoscalar glueballs in pure Yang–Mills theory using a parameter-free fully self-contained truncation of Dyson–Schwinger and Bethe–Salpeter equations. The only input, the scale, is fixed by comparison with lattice calculations. We obtain ground state masses of $$1.9\,\text {GeV}$$ 1.9 GeV and $$2....

We provide results for the spectrum of scalar and pseudoscalar glueballs in pure Yang-Mills theory using a parameter-free fully self-contained truncation of Dyson-Schwinger and Bethe-Salpeter equations. The only input, the scale, is fixed by comparison with the gluon propagator from (gauge-fixed) lattice calculations. We obtain ground state masses...

A calculation of hadronic timelike form factors in the Poincaré-covariant Bethe-Salpeter formalism necessitates knowing the analytic structure of the non-perturbative quark-photon vertex in the context of the Poincaré-covariant Bethe-Salpeter formalism. We include, in the interaction between quark and antiquark, the possibility of non-valence effec...

A calculation of hadronic timelike form factors in the Poincar\'e-covariant Bethe-Salpeter formalism necessitates knowing the analytic structure of the non-perturbative quark-photon vertex in the context of the Poincar\'e-covariant Bethe-Salpeter formalism. We include, in the interaction between quark and antiquark, the possibility of non-valence e...

We present progress on the study of decay-channel effects in the properties of hadrons using covariant Bethe-Salpeter equations (BSEs). The main goal will be to develop BSE kernels that contain explicit decay mechanisms. This will be first explored in the meson sector where, for example, a kernel suitable to study the rho meson should contain a vir...

We report on a functional renormalisation group approach to bound state properties similar to the Dyson-Schwinger–Bethe-Salpether approach. The current approach is set-up for the two-flavour quark-meson model for an illustration of the basic properties. This allows us to access the pion and sigma poles and decay properties. First numerical results...

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-...

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...

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 $\Sigma^0$ to $\Lambda$ transition. We work in the combined framework of Dyson-Schwinger equations and covariant Bethe-Salpeter equations with all elements, the baryon three body wave functio...

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 bot...

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...

We present a calculation of the Hadron spectrum in the Dyson-Schwinger/Bethe-Salpeter approach to continuum QCD. A sophisticated truncation featuring all covariant structures of the quark-gluon vertex, with its inherent flavour dependence, is employed in a framework that preserves the dynamics of chiral symmetry breaking. The study is suggestive as...

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 th...

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.
The masses of both the ground state mesons and baryons are found to be in
reasonable agreement with contemporary `quark-core rai...

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 co...

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.

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 bar...

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 motivate...

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-t...

We report on recent results of a calculation of the nucleon and delta masses
in a covariant bound-state approach, where to the simple rainbow-ladder
gluon-exchange interaction kernel we add a pion-exchange contribution to
account for pion cloud effects. We observe good agreement with lattice data at
large pion masses. At the physical point our mass...

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 th...

We present first results for the excited nucleon spectrum in the framework of Poincaré-covariant three-body Bethe-Salpeter equations using the Rainbow-Ladder truncation of the interaction kernel. As expected, this truncation does not provide the mechanisms for a correct description of the spectrum. We also comment on possible steps beyond Rainbow-L...

We study baryons as three-body systems using the QCD degrees of freedom in
the framework of covariant Bethe-Salpeter equations. The interaction among
quarks is reduced to a vector-vector interaction via a single dressed-gluon
exchange (Rainbow-Ladder truncation). The formalism allows for the study of the
hadron spectrum as well as their internal pr...

The electromagnetic form factors of the Delta and Omega baryons are
calculated in the framework of Poincare-covariant bound-state equations. The
quark-quark interaction is truncated to a single dressed-gluon exchange where
for the dressings we use two different models and compare the results. The
calculation predicts an oblate shape for the electri...

We consider static spherically symmetric stellar configurations in Palatini
theories of gravity in which the Lagrangian is an unspecified function of the
form f(R,R_{\mu\nu}R^{\mu\nu}). We obtain the Tolman-Oppenheimer-Volkov
equations corresponding to this class of theories and show that they recover
those of f(R) theories and General Relativity i...

We consider static spherically symmetric stellar configurations in Palatini
theories of gravity in which the Lagrangian is an unspecified function of the
form $f(R,R_{\mu\nu}R^{\mu\nu})$. We obtain the Tolman-Oppenheimer-Volkov
equations corresponding to this class of theories and show that they recover
those of $f(R)$ theories and General Relativi...

A calculation of the masses and electromagnetic properties of the Delta and
Omega baryon together with their evolution with the current quark mass is
presented. Hereby a generalized Bethe-Salpeter approach with the interaction
truncated to a dressed one-gluon exchange is employed. The model dependence is
explored by investigating two forms for the...

In this thesis the covariant Bethe-Salpeter equation formalism is used to
study some properties of ground-state baryons. This formalism relies on the
knowledge of the interaction kernel among quarks and of the full quark
propagator. For the interaction kernel, which is in principle a sum of
infinitely many diagrams, I use the Ladder truncation. It...

We compute the vector-meson, nucleon and delta/omega-baryon masses and their
evolution with the current-quark mass using a covariant generalized
Bethe-Salpeter equation approach. The interaction kernel is truncated to a
dressed gluon exchange. We study the model dependence of our results with the
quark-gluon dressing to assess the validity of the t...

We present the solution of the Poincare-covariant Faddeev equation for the
Delta(1232) and Omega(1672) baryons. The covariant structure of the
corresponding baryon amplitudes and their decomposition in terms of internal
spin and orbital angular momentum is explicitly derived. The interaction kernel
is truncated to a rainbow-ladder dressed-gluon exc...

We study the Hamiltonian formulation of f(R) theories of gravity both in
metric and in Palatini formalism using their classical equivalence with
Brans-Dicke theories with a non-trivial potential. The Palatini case, which
corresponds to the w=-3/2 Brans-Dicke theory, requires special attention
because of new constraints associated with the scalar fi...

The Poincare-covariant Faddeev equation and its solution in rainbow-ladder truncation, i.e., with a generalized gluon exchange as irreducible two-particle-interaction, is presented. The covariant decomposition of baryon amplitudes, representing relativistic three-quark states, is discussed and explicitly given for the Delta-baryon. The calculated D...

We show that there exist modified theories of gravity in which the metric satisfies second-order equations and in which the Big Bang singularity is replaced by a cosmic bounce without violating any energy condition. In fact, the bounce is possible even for presureless dust. We give a characterization of such theories, which are formulated in the Pa...

We show that extended theories of gravity with Lagrangian f(R,R_{\mu\nu}R^{\mu\nu}) in the Palatini formulation possess a phenomenology much richer than the simpler f(R) or f(R_{\mu\nu}R^{\mu\nu}) theories. In fact, we find that the scalars R and Q=R_{\mu\nu}R^{\mu\nu} can be written as algebraic functions of the energy density and pressure of the...

We study the field equations of modified theories of gravity in which the lagrangian is a general function of the Ricci scalar and Ricci-squared terms in Palatini formalism. We show that the independent connection can be expressed as the Levi-Civita connection of an auxiliary metric which, in particular cases of interest, is related with the physic...

We consider the early time cosmology of f(R) theories in Palatini formalism and study the conditions that guarantee the existence of homogeneous and isotropic models that avoid the Big Bang singularity. We show that for such models the Big Bang singularity can be replaced by a cosmic bounce without violating any energy condition. In fact, the bounc...

Shannon entropy [1] was introduced as a measure of the uncertainty associated with a random variable and initially it was used to quantify the information contained in a binary message. In this work, a definition of Shannon's information entropy is introduced in acoustics, defined in terms of the displacement field, as a measure of the localization...

We demonstrate the existence of Bloch oscillations of acoustic fields in sound propagation through a superlattice of water cavities and layers of methyl methacrylate. To obtain the acoustic equivalent of a Wannier-Stark ladder, we employ a set of cavities with different thicknesses. Bloch oscillations are observed as time-resolved oscillations of t...

We report the acoustic analogue of electronic Bloch oscillations and Zener tunneling in sonic crystals. First, an analytic theory of acoustic Bloch oscillations is presented for the simple case of a sound waves propagating along the normal of a multilayer made of any two different solid or fluids materials. The formulation is applied to the case of...

The observation of Bloch oscillations in sound propagation through a multilayer of two different fluidlike components is predicted. In order to obtain the equivalent to the acoustic analog of a Wannier‐Stark ladder [E. E. Mendez et al., Phys. Rev. Lett. 60, 2426–2429 (1988)], a set of cavities with increasing thickness is employed. Bloch oscillatio...

We study static quantum corrections of the Schwarzschild metric in the Boulware vacuum state. Due to the absence of a complete analytic expression for the full semiclassical Einstein equations we approach the problem by considering the s-wave approximation and solve numerically the associated backreaction equations. The solution, including quantum...

Motivated by the quest for black holes in AdS braneworlds, and in particular by the holographic conjecture relating 5D classical bulk solutions with 4D quantum corrected ones, we numerically solve the semiclassical Einstein equations (backreaction equations) with matter fields in the (zero temperature) Boulware vacuum state. In the absence of an ex...