260 research outputs found
Euclidean-Minkowskian duality of Wilson-loop correlation functions
We discuss the analyticity properties of the Wilson--loop correlation
functions relevant to the problem of soft high-energy scattering, directly at
the level of the functional integral, in a genuinely nonperturbative way.Comment: 12 pages, 1 figure. To appear in the proceedings of the Tenth
Workshop on Non-Perturbative Quantum Chromodynamics, Paris, France, 8-12th
June 200
Lattice approach to high-energy hadron-hadron scattering
We discuss the non perturbative approach to the problem of high-energy
hadron-hadron (dipole-dipole) scattering at low momentum transfer by means of
numerical simulations in Lattice Gauge Theory.Comment: 4 pages, 5 figures, LaTeX with espcrc2.sty (v. 2.7). To appear in the
proceedings of the 14th International QCD Conference (QCD 08), Montpellier,
France, 7-12 July 200
Reviewing the problem of the U(1) axial symmetry and the chiral transition in QCD
We discuss the role of the U(1) axial symmetry for the phase structure of QCD
at finite temperature. We expect that, above a certain critical temperature,
also the U(1) axial symmetry will be (effectively) restored. We will try to see
if this transition has (or has not) anything to do with the usual chiral
transition: various possible scenarios are discussed. In particular, supported
by recent lattice results, we analyse a scenario in which a U(1)-breaking
condensate survives across the chiral transition. This scenario can be
consistently reproduced using an effective Lagrangian model. The effects of the
U(1) chiral condensate on the slope of the topological susceptibility in the
full theory with quarks are studied: we find that this quantity (in the chiral
limit of zero quark masses) acts as an order parameter for the U(1) axial
symmetry above the chiral transition. Further information on the new U(1)
chiral order parameter is derived from the study (at zero temperature) of the
radiative decays of the pseudoscalar mesons in two photons: a comparison of our
results with the experimental data is performed.Comment: 27 pages, LaTeX file. Completely revised version including new
references and new comments on the result
Asymptotic Energy Dependence of Hadronic Total Cross Sections from Lattice QCD
The nonperturbative approach to soft high-energy hadron-hadron scattering,
based on the analytic continuation of Wilson-loop correlation functions from
Euclidean to Minkowskian theory, allows to investigate the asymptotic energy
dependence of hadron-hadron total cross sections in lattice QCD. In this paper
we will show, using best fits of the lattice data with proper functional forms
satisfying unitarity and other physical constraints, how indications emerge in
favor of a universal asymptotic high-energy behavior of the kind B log^2 s for
hadronic total cross sections.Comment: Revised and extended version; 29 pages, 4 figure
Gauge invariant Field Strength Correlators in QCD
Gauge invariant correlators in QCD are studied on the lattice.A Systematic
determination of the correlation lengths for gluon field strength correlators
and quark correlators is made.The measurement of the gluon and quark
condensates is discussed.Comment: 5 pages,4 figures.Presented by A.Di Giacomo to ICHEP98. To appear in
the proceedings Misprints correcte
Effects of an extra U(1) axial condensate on the strong decays of pseudoscalar mesons
We consider a scenario (supported by some lattice results) in which a
U(1)-breaking condensate survives across the chiral transition in QCD. This
scenario has important consequences for the pseudoscalar-meson sector, which
can be studied using an effective Lagrangian model. In particular, generalizing
the results obtained in two previous papers, where the effects on the radiative
decays eta,eta' --> gamma gamma were studied, in this paper we study the
effects of the U(1) chiral condensate on the strong decays of the "light"
pseudoscalar mesons, i.e., eta,eta' --> 3pi^0; eta,eta' --> pi^+ pi^- pi^0;
eta' --> eta pi^0 pi^0; eta' --> eta pi^+ pi^-; and also on the strong decays
of an exotic ("heavy") SU(3)-singlet pseudoscalar state eta_X, predicted by the
model.Comment: One misprint in Eq. (2.10) has been eliminated; Eqs. (B.8) and (B.9)
in Appendix B have been corrected; 46 pages, 1 tabl
The effects of an extra U(1) axial condensate on the radiative decay eta' --> gamma gamma at finite temperature
Supported by recent lattice results, we consider a scenario in which a
U(1)-breaking condensate survives across the chiral transition in QCD. This
scenario has important consequences on the pseudoscalar-meson sector, which can
be studied using an effective Lagrangian model. In particular, generalizing the
results obtained in a previous paper (where the zero-temperature case was
considered), we study the effects of this U(1) chiral condensate on the
radiative decay eta' --> gamma gamma at finite temperature.Comment: 15 pages, LaTeX fil
Asymptotic high-energy behavior of hadronic total cross sections from lattice QCD
We will show how a universal and Froissart-like (i.e., of the kind "B log^2
s") hadron-hadron total cross section can emerge in QCD asymptotically at high
energy, finding indications for this behavior from the lattice. The functional
integral approach provides the natural setting for achieving this result, since
it encodes the energy dependence of hadronic scattering amplitudes in a single
elementary object, i.e., a proper correlation function of two Wilson loops.Comment: Talk given (by E. Meggiolaro) at the "48th Rencontres de Moriond on
QCD and High Energy Interactions", La Thuile (Valle d'Aosta, Italy), 9-16
March 2013; 4 pages, 1 tabl
Aprotic sulfur-metal batteries: lithium and beyond
Metal-sulfur batteries constitute an extraordinary research playground that ranges from fundamental science to applied technologies. However, besides the widely explored Li-S system, a remarkable lack of understanding hinders advancements and performance in all other metal-sulfur systems. In fact, similarities and differences make all generalizations highly inconsistent, thus unavoidably suggesting the need for extensive research explorations for each formulation. Here we review critically the most remarkable open challenges that still hinder the full development of metal-S battery formulations, starting from the lithium benchmark and addressing Na, K, Mg, and Ca metal systems. Our aim is to draw an updated picture of the recent efforts in the field and to shed light on the most promising innovation paths that can pave the way to breakthroughs in the fundamental comprehension of these systems or in battery performance
Wilson-loop formalism for Reggeon exchange in soft high-energy scattering
We derive a nonperturbative expression for the non-vacuum,
qqbar-Reggeon-exchange contribution to the meson-meson elastic scattering
amplitude at high energy and low momentum transfer, in the framework of QCD.
Describing the mesons in terms of colourless qqbar dipoles, the problem is
reduced to the two-fermion-exchange contribution to the dipole-dipole
scattering amplitudes, which is expressed as a path integral, over the
trajectories of the exchanged fermions, of the expectation value of a certain
Wilson loop. We also show how the resulting expression can be reconstructed
from a corresponding quantity in the Euclidean theory, by means of analytic
continuation. Finally, we make contact with previous work on Reggeon exchange
in the gauge/gravity duality approach.Comment: A few misprints in the expressions for the relevant Wilson loops have
been corrected. 55 pages, 7 figure
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