122912012
Canonical treatment of «noncanonical» gauges for constrained Hamiltonian systems
27650465
Large-order perturbation theory for the electromagnetic current-current correlation function.
The constraints imposed by asymptotic freedom and analyticity on the large-order behavior of perturbation theory for the electromagnetic current-current correlation function are examined. By suitably applying the renormalization group, the coefficients of the asymptotic expansion in the deep Euclidean region may be expressed explicitly in terms of the perturbative coefficients of the Minkowski space discontinuity (the {ital R} ratio in {ital e}{sup +}{ital e{minus}} scattering). This relation yields a generic'' prediction for the large-order behavior of the Euclidean perturbation series and suggests the presence of nonperturbative 1/{ital q}{sup 2} correction in the Euclidean correlation function. No such generic'' prediction can be made for the physically measurable {ital R} ratio. A novel functional method is developed to obtain these results.
119112883
Stress-energy tensor of a quark moving through a strongly-coupled N=4 supersymmetric Yang-Mills plasma: Comparing hydrodynamics and AdS/CFT duality
The stress-energy tensor of a quark moving through a strongly-coupled $\mathcal{N}=4$ supersymmetric Yang-Mills plasma, at large ${N}_{\mathrm{c}}$, is evaluated using gauge/string duality. The accuracy with which the resulting wake, in position space, is reproduced by hydrodynamics is examined. Remarkable agreement is found between hydrodynamics and the complete result down to distances less than $2/T$ away from the quark. In performing the gravitational analysis, we use a relatively simple formulation of the bulk to boundary problem in which the linearized Einstein field equations are fully decoupled. Our analysis easily generalizes to other sources in the bulk.
40615999
Asymptotic behavior of perturbation theory for the electromagnetic current-current correlation function in QCD.
A simple and direct approach is used to examine the constraints imposed by asymptotic freedom and analytically on the large-order behavior of perturbaton theory for the current-current correlation function and its imaginary part which gives the {ital R} ratio in high-energy {ital e}{sup +-}{ital e{minus}} annihilation.
17943605
In)validity of large N orientifold equivalence
It has been argued that the bosonic sectors of supersymmetric SU(N) Yang-Mills theory, and of QCD with a single fermion in the antisymmetric (or symmetric) tensor representation, are equivalent in the N{yields}{infinity} limit. If true, this correspondence can provide useful insight into properties of real QCD (with fundamental representation fermions), such as predictions [with O(1/N) corrections] for the nonperturbative vacuum energy, the chiral condensate, and a variety of other observables. Several papers asserting to have proven this large N 'orientifold equivalence' have appeared. By considering theories compactified on R{sup 3}xS{sup 1}, we show explicitly that this large N equivalence fails for sufficiently small radius, where our analysis is reliable, due to spontaneous symmetry breaking of charge-conjugation symmetry in QCD with an antisymmetric (or symmetric) tensor representation fermion. This theory is also chirally symmetric for small radius, unlike super-Yang-Mills theory. The situation is completely analogous to large-N equivalences based on orbifold projections: simple symmetry realization conditions are both necessary and sufficient for the validity of the large N equivalence. Whether these symmetry realization conditions are satisfied depends on the specific nonperturbative dynamics of the theory under consideration. Unbroken charge-conjugation symmetry is necessary for validity of the large N orientifold equivalence. Whethermore » or not this condition is satisfied on R{sup 4} (or R{sup 3}xS{sup 1} for sufficiently large radius) is not currently known.« less
14305135
From quantum field theory to hydrodynamics: Transport coefficients and effective kinetic theory.
The evaluation of hydrodynamic transport coefficients in relativistic field theory, and the emergence of an effective kinetic theory description, is examined. Even in a weakly coupled scalar field theory, interesting subtleties arise at high temperatures where thermal renormalization effects are important. In this domain, a kinetic theory description in terms of the fundamental particles ceases to be valid, but one may derive an effective kinetic theory describing excitations with temperature dependent properties. While the shear viscosity depends on the elastic scattering of typical excitations whose kinetic energies are comparable to the temperature, the bulk viscosity is sensitive to particle nonconserving processes at small energies. As a result, the shear and the bulk viscosities have very different dependence on the interaction strength and temperature, with the bulk viscosity providing an especially sensitive test of the validity of an effective kinetic theory description. {copyright} {ital 1996 The American Physical Society.}
120315024
CROSS SECTIONS FOR THE PRODUCTION OF Cl, K, Ca, AND Sc ISOTOPES IN THE BOMBARDMENT OF Pb AND U WITH 3.0-Bev PROTONS
Cross sections for the formation of some nuclides in the mass number range 38 to 48 in the bombardment of Pb and U with 3.0-Bev protons were measured. The maximum of the isobaric yield distributions for the nuclides from the Pb bombardnnent occurs at the stability line, while that from U is somewhat on the neutron-excess side. Total cross sections of 4 to 5 mb per mass number are deduced from the Pb data leading to a revision of the mass-yield curve in this region as proposed by Wolfgang et al.The cross sections from uranium are approximately twice as large as those from Pb. The data are shown to be consistent with a cascade-fission-evaporation mechanism. (auth)
120217954
( p , xn ) and ( p , pxn ) Reactions of Yttrium-89 with 5-85-MeV Protons