Person: Vioque Rodríguez, Andrea
Universidad Complutense de Madrid
Faculty / Institute
Now showing 1 - 4 of 4
PublicationThe role of strangeness in chiral and U(1)A restoration(Springer, 2021-07) Gómez Nicola, Ángel; Ruiz de Elvira Carrascal, Jacobo; Vioque Rodríguez, Andrea; Álvarez Herrero, D.© The Author(s) 2021 We use recently derived Ward identities and lattice data for the light- and strange-quark condensates to reconstruct the scalar and pseudoscalar susceptibilities (chi S kappa, chi PK) in the isospin 1/2 channel. We show that chi S kappa develops a maximum above the QCD chiral transition, after which it degenerates with chi PK. We also obtain chi S kappa within Unitarized Chiral Perturbation Theory (UChPT) at finite temperature, when it is saturated with the K0(700) (or kappa) meson, the dominant lowest-energy state in the isospin 1/2 scalar channel of pi K scattering. Such UChPT result reproduces the expected peak structure, revealing the importance of thermal interactions, and makes it possible to examine the chi S kappa dependence on the light- and strange-quark masses. A consistent picture emerges controlled by the ml/ms ratio that allows one studying K-kappa degeneration in the chiral, two-flavor and SU(3) limits. These results provide an alternative sign for O(4)xU(1)A restoration that can be explored in lattice simulations and highlight the role of strangeness, which regulated by the strange-quark condensate helps to reconcile the current tension among lattice results regarding U(1)A restoration. PublicationEffective Lagrangian at nonzero isospin chemical potential(Amer Physical Soc, 2022-12-19) Gómez Nicola, Ángel; Vioque Rodríguez, AndreaWe revisit the most general effective Lagrangian within chiral perturbation theory at nonzero isospin chemical potential mu(I) up to O(p(4)). In addition to the contributions already considered in the literature, we discuss the effects of new terms allowed by the symmetries derived within the external source method including spurion fields, as well as linear-field corrections relevant to O(p(4)). We study the influence of those new contributions to the free energy density at zero temperature and observables derived from it, such as the pion and quark condensates and the isospin density. Corrections are shown to be compatible with lattice results, which favor nonzero values for the low-energy constants (LECs) multiplying the new O(p(2)) and O(p(4)) field operators in the Lagrangian. In particular, the O(p(4)) LECs are renormalized to render the free energy density finite. Constraints on the LECs arise from preserving the physical condition n(I)(mu(I) < mu(c)) = 0, while mu(c) = M-pi, still holds to leading order and can be maintained to next-to-leading order through an additional constraint requiring the new LECs. PublicationChiral perturbation theory for nonzero chiral imbalance(Springer, 2020-06-09) Espriu, Domènec; Gómez Nicola, Ángel; Vioque Rodríguez, AndreaWe construct the most general low-energy effective lagrangian including local parity violating terms parametrized by an axial chemical potential or chiral imbalance mu (5), up to O mml:mfenced close=")" open="("p4 ml:mfenced> order in the chiral expansion for two light flavours. For that purpose, we work within the Chiral Perturbation Theory framework where only pseudo-NGB fields are included, following the external source method. The O mml:mfenced close=")" open="("p2 mml:mfenced> lagrangian is only modified by constant terms, while the O mml:mfenced close=")" open="("p4 mml:mfenced one includes new terms proportional to mu 52 and new low-energy constants (LEC), which are renormalized and related to particular observables. In particular, we analyze the corrections to the pion dispersion relation and observables related to the vacuum energy density, namely the light quark condensate, the chiral and topological susceptibilities and the chiral charge density, providing numerical determinations of the new LEC when possible. In particular, we explore the dependence of the chiral restoration temperature T-c with mu (5). An increasing T-c(mu (5)) is consistent with our fits to lattice data of the ChPT-based expressions. Although lattice uncertainties are still large and translate into the new LEC determination, a consistent physical description of those observables emerges from our present work, providing a theoretically robust model-independent framework for further study of physical systems where parity-breaking effects may be relevant, such as heavy-ion collisions. PublicationThe QCD topological charge and its thermal dependence: the role of the eta'(Springer, 2019-11-14) Gómez Nicola, Ángel; Ruiz de Elvira Carrascal, Jacobo; Vioque Rodríguez, AndreaWe analyze the contribution of the 7/(958) meson in the first two non-trivial moments of the QCD topological charge distribution, namely, the topological susceptibility and the fourth-order cumulant of the vacuum energy density. We perform our study within U(3) Chiral Perturbation Theory up to next -to-next -to-leading order in the combined chiral and large-Ne expansion. We also describe the temperature dependence of these two quantities and compare them with previous analyses in the literature. In particular, we discuss the validity of the thermal scaling of the topological susceptibility with the quark condensate, which is intimately connected with a Ward Identity relating both quantities. We also consider isospin breaking corrections from the vacuum misalignment at leading order in the U(3) framework.