Infrared finitness and analyticity properties of the loop-loop scattering amplitudes in gauge theories

We shall discuss about the infrared finitness and some analyticity properties of the loop-loop scattering amplitudes in gauge theories, when going from Minkowskian to Euclidean theory, and we shall see how they can be related to the still unsolved problem of the s-dependence of the hadron-hadron total cross-sections.Comment: Talk given at the ``International Workshop on Diffraction in High-Energy Physics'' (DIFFRACTION 2004), Cala Gonone (Sardinia, Italy), 18-23 September 2004; 3 pages, LaTeX fil

Deriving the pomeron from a Euclidean-Minkowskian duality

After a brief review, in the first part, of some relevant analyticity properties of the loop-loop scattering amplitudes in gauge theories, when going from Minkowskian to Euclidean theory, in the second part we shall see how they can be related to the still unsolved problem of the s-dependence of the hadron-hadron total cross-sections.Comment: 10 pages. Contribution to "Sense of Beauty in Physics - a volume in honour of Adriano Di Giacomo" (Pisa University Press, Pisa, 2006), on the occasion of his 70th birthda

Euclidean formulation of diffractive scattering

After a brief review (in the first part) of some relevant properties of the high-energy parton-parton scattering amplitudes, in the second part we shall discuss the infrared finiteness and some analyticity properties of the loop-loop scattering amplitudes in gauge theories, when going from Minkowskian to Euclidean theory, and we shall see how they can be related to the still unsolved problem of the s-dependence of the hadron-hadron total cross-sections.Comment: Talk given at the ``XIth International Conference on Elastic and Diffractive Scattering'' (EDS 2005), XVIIth Rencontre de Blois, Chateau de Blois (France), 15-20 May 2005; 6 page

High-energy scattering and Euclidean-Minkowskian duality

We shall discuss how some relevant analyticity and crossing-symmetry properties of the "eikonal scattering amplitudes" of two Wilson loops in QCD, when going from Euclidean to Minkowskian theory, can be related to the still unsolved problem of the asymptotic s-dependence of the hadron-hadron total cross-sections. In particular, we critically discuss the question if (and how) a pomeron-like behaviour can be derived from this Euclidean-Minkowskian duality.Comment: Talk given at the XIIth International Conference on Elastic and Diffractive Scattering (Blois Workshop, EDS 2007), ``Forward Physics and QCD'', DESY, Hamburg (Germany), 21-25 May 2007; 8 page

Remarks on the U(1) axial symmetry and the chiral transition in QCD at finite temperature

We discuss the role of the U(1) axial symmetry for the scalar and pseudoscalar meson mass spectrum of QCD at finite temperature, above the chiral transition at T_c, using a chiral effective Lagrangian model, which, in addition to the usual chiral condensate, also includes a (possible) genuine U(1)_A-breaking condensate that (possibly) survives across the chiral transition. The motivations for considering this Lagrangian (and a critical comparison with other effective Lagrangian models existing in the literature) are presented. A detailed comparison between the case N_f=3 (or N_f>3) and the (remarkably different) case N_f=2 is performed. The results obtained in the case N_f=2 are also critically compared with the available lattice results.Comment: Revised version, published in PRD; 28 pages, 1 table, 1 figur

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

Field strength correlators in QCD: new fits to the lattice data

We discuss the results obtained by fitting the lattice data of the gauge-invariant field strength correlators in QCD with some particular functions which are commonly used in the literature in some phenomenological approaches to high-energy hadron-hadron scattering. A comparison is done with the results obtained in the original fits to the lattice data

The analytic continuation of the high-energy quark-quark scattering amplitude

We consider some analytic properties of the high-energy quark-quark scattering amplitude, which can be described by the expectation value of two lightlike Wilson lines, running along the classical trajectories of the two colliding particles. We shall prove that the expectation value of two infinite Wilson lines, forming a certain hyperbolic angle in Minkowski space-time, and the expectation value of two infinite Euclidean Wilson lines, forming a certain angle in Euclidean four-space, are connected by an analytic continuation in the angular variables. This could open the possibility of evaluating the high-energy scattering amplitude directly on the lattice

The high-energy quark-quark scattering: from Minkowskian to Euclidean theory

In this paper we consider some analytic properties of the high--energy quark--quark scattering amplitude, which, as is well known, can be described by the expectation value of two lightlike Wilson lines, running along the classical trajectories of the two colliding particles. We shall prove that the expectation value of two infinite Wilson lines, forming a certain hyperbolic angle in Minkowski space--time, and the expectation value of two infinite Euclidean Wilson lines, forming a certain angle in Euclidean four--space, are connected by an analytic continuation in the angular variables. This could open the possibility of evaluating the high--energy scattering amplitude directly on the lattice or using the stochastic vacuum model. The Abelian case (QED) is also discussed