Universal structure of subleading infrared poles at strong coupling

Recently a concise expression for the subleading infrared singularity of dimensional-regularized gauge theories has been proposed. For conformal theories, such relation involves a universal eikonal contribution plus a non-eikonal contribution, related to the subleading term in the anomalous dimension of twist two operators with large spin. In this note we make use of the AdS/CFT correspondence in order to check such conjecture at strong coupling for the case of N=4 SYM.Comment: 13 page

New representation for the odderon wave function

New representation of the odderon wave function is derived, which is convergent in the whole impact parameter plane and provides the analytic form of the quantization condition for the integral of motion q_3. A new quantum number, triality, is identified. This, together with the choice of the conformal basis, allows for simple calculation of eigenvalues of a wide class of operators.Comment: 15 pages, latex, one .eps figur

Evolution of twist-three parton distributions in QCD beyond the large N_c limit

We formulate a consistent 1/N_c^2 expansion of the QCD evolution equations for the twist-three quark distributions g_2(x,Q^2), h_L(x,Q^2) and e(x,Q^2) based on the interpretation of the evolution as a three-particle quantum-mechanical problem with hermitian Hamiltonian. Each distribution amplitude can be decomposed in contributions of partonic components with DGLAP-type scale dependence. We calculate the 1/N_c^2 corrections to the evolution of the dominant component with the lowest anomalous dimension - the only one that survives in the large-N_c limit - and observe a good agreement with the exact numerical results for N_c=3. The 1/N_c^2 admixture of operators with higher anomalous dimensions is shown to be concentrated at a few lowest partonic components and in general is rather weak.Comment: 14 pages, LaTeX style, 2 figure

Infrared Factorization, Wilson Lines and the Heavy Quark Limit

It is shown that, in QCD, the same universal function \Gamma_{cusp}(\vartheta, \alpha_\s) determines the infrared behaviour of the on-shell quark form factor, the velocity-dependent anomalous dimension in the heavy quark effective field theory (HQET) and the renormalization properties of the vacuum averaged Wilson lines with a cusp. It is demonstrated that a combined use of the methods developed in the relevant different branches of quantum field theory essentially facilitates the all-order study of the asymptotic and analytic properties of this function.Comment: 10 page

Energy flow in QCD and event shape functions

Hadronization corrections to the thrust and related event shape distributions in the two-jet kinematical region of e+e- annihilation are summarized by nonperturbative shape functions. The moments of shape functions are given by universal matrix elements in QCD, which describe the energy flow in QCD final states. We show how the nonperturbative structure of these matrix elements may be inferred from resummed perturbation theory and Lorentz invariance. This analysis suggests the same functional forms for the shape functions as were found in phenomenological studies, and sheds light on the physical significance of the parameters that characterize these functions.Comment: 15 pages, LaTeX, 2 figure

Gauge Invariance and Anomalous Dimensions of a Light-Cone Wilson Loop in Light-Like Axial Gauge

Complete two-loop calculation of a dimensionally regularized Wilson loop with light-like segments is performed in the light-like axial gauge with the Mandelstam-Leibbrandt prescription for the gluon propagator. We find an expression which {\it exactly} coincides with the one previously obtained for the same Wilson loop in covariant Feynman gauge. The renormalization of Wilson loop is performed in the \MS-scheme using a general procedure tailored to the light-like axial gauge. We find that the renormalized Wilson loop obeys a renormalization group equation with the same anomalous dimensions as in covariant gauges. Physical implications of our result for investigation of infrared asymptotics of perturbative QCD are pointed out.Comment: 24 pages and 4 figures (included), LaTeX style, UFPD-93/TH/23, UPRF-93-366, UTF-93-29

Properties of a family of n reggeized gluon states in multicolour QCD

A general relation between families of (n+1) gluon and n gluon eigenstates of the BKP evolution kernels in the multicolour limit of QCD is derived. It allows to construct an (n+1) gluon eigenstate if an n gluon eigenstate is known; this solution is Bose symmetric and thus physical for even n. A recently found family of odderon solutions corresponds to the particular case n=2.Comment: 11 pages, 1 figur

Approximate NNLO Threshold Resummation in Heavy Flavour Decays

We present an approximate NNLO evaluation of the QCD form factor resumming large logarithmic perturbative contributions in semi-inclusive heavy flavour decays.Comment: 16 pages, 3 figures, Latex; minor changes; 2 figures adde

N=4 superconformal Ward identities for correlation functions

International audienceIn this paper we study the four-point correlation function of theenergy-momentum supermultiplet in theories with N=4 superconformal symmetry infour dimensions. We present a compact form of all component correlators as aninvariant of a particular abelian subalgebra of the N=4 superconformal algebra.This invariant is unique up to a single function of the conformal cross-ratioswhich is fixed by comparison with the correlation function of the lowesthalf-BPS scalar operators. Our analysis is independent of the dynamics of aspecific theory, in particular it is valid in N=4 super Yang-Mills theory forany value of the coupling constant. We discuss in great detail a subclass ofcomponent correlators, which is a crucial ingredient for the recent study ofcharge-flow correlations in conformal field theories. We compute the latterexplicitly and elucidate the origin of the interesting relations amongdifferent types of flow correlations previously observed in arXiv:1309.1424

Scaling Rule for Nonperturbative Radiation in a Class of Event Shapes

We discuss nonperturbative radiation for a recently introduced class of infrared safe event shape weights, which describe the narrow-jet limit. Starting from next-to-leading logarithmic (NLL) resummation, we derive an approximate scaling rule that relates the nonperturbative shape functions for these weights to the shape function for the thrust. We argue that the scaling reflects the boost invariance implicit in NLL resummation, and discuss its limitations. In the absence of data analysis for the new event shapes, we compare these predictions to the output of the event generator PYTHIA.Comment: 23 pages, 3 figures, uses JHEP3.cls (included); v2 - version to appear in JHE