14,247 research outputs found

### String Theory and Quark Confinement

This article is based on a talk given at the ``Strings'97'' conference. It
discusses the search for the universality class of confining strings. The key
ingredients include the loop equations, the zigzag symmetry, the non-linear
renormalization group. Some new tests for the equivalence between gauge fields
and strings are proposed.Comment: 13 pages, latex; talk at STRINGS'9

### Hard exclusive production of two pions: Dipion mass distributions in gamma* N -->pi pi N and gamma* gamma --> pi pi

The leading twist parametrization of dipion mass distribution in hard
exclusive reactions is proposed. Its parameters are related to quark
distributions (usual and skewed) in the pion and to distributions amplitudes of
mesons ($\pi$, $\rho$, etc.). We show that measurements of the shape of dipion
mass distribution in hard exclusie reactions can give important information
about partonic structure of the pion. The expression for the amplitude of the
reaction $\gamma^*\gamma\to \pi\pi$ near the threshold in terms of singlet
quark distribution in the pion is presented.Comment: Talk given at 7th International Workshop on Deep Inelastic Scattering
and QCD (DIS 99), Zeuthen, Germany, 19-23 Apr 1999. Minor typos are correcte

### World Sheet Logarithmic CFT in AdS Strings, Ghost-Matter Mixing and M-theory

We discuss several closely related concepts in the NSR formulation of
superstring theory. We demonstrated that recently proposed NSR model for
superstrings on $AdS_5 \times S^5$ is described by the world-sheet logarithmic
conformal field theory (LCFT). The origin of LCFT on a world-sheet is closely
connected to the matter-ghost mixing in the structure of a brane-like vortex
operators. We suggest a dynamical origin of M theory as a string theory with an
extra dimension given by bosonised superconformal ghosts.Comment: 20 pages, no figures, harvmac, corrected some typo

### On Polyakov's basic variational formula for loop spaces

We use the homological algebra context to give a more rigorous proof of
Polyakov's basic variational formula for loop spaces.Comment: Latex, 17 pages, no figure

### Various Properties of Compact QED and Confining Strings

The effects bringing about by the finiteness of the photon mass due to the
Debye screening in the monopole gas in three-dimensional compact QED are
studied. In this respect, a representation of the partition function of this
theory as an integral over monopole densities is derived. Dual formulation of
the Wilson loop yields a new theory of confining strings, which in the
low-energy limit almost coincides with the one corresponding to the case when
the photon is considered to be massless, whereas in the high-energy limit these
two theories are quite different from each other. The confining string mass
operator in the low-energy limit is also found, and its dependence on the
volume of observation is studied.Comment: 7 pages, LaTeX, no figures, 1 reference is added, final version to
appear in Phys. Lett.

### Classical Hamiltonian Reduction and Superconformal Algebras

The Polyakov's "soldering procedure" which shows how two-dimensional
diffeomorphisms can be obtained from SL(2,R) gauge transformations is discussed
using the free-field representation of SL(2,R) current algebra. Using this
formalism, the relation of Polyakov's method to that of the Hamiltonian
reduction becomes transparent. This discussion is then generalised to N=1
superdiffeomorphisms which can be obtained from N=1 super Osp(1,2) gauge
transformations. It is also demonstrated that the phase space of the Osp(2,2)
supercurrent algebra represented by free superfields is connected to the
classical phase space of N=2 superconformal algebra via Hamiltonian reduction.}Comment: 21 pages, revised version contains minor grammatical changes and an
update of refernce

### On the NSR formulation of String Theory on AdS_5 X S^5

We discuss the NSR formulation of the superstring action on AdS_5 X S^5
proposed recently by Kallosh and Tseytlin in the Green-Schwarz formalism.We
show that the stress-energy tensor corresponding to the NSR action for AdS
superstring contains the branelike terms, corresponding to exotic massless
vertex operators (refered to as the branelike vertices). The corresponding
sigma-model action has the manifest SO(1,3) X SO(6) invariance of superstring
theory on AdS_5 X S^5. We argue that adding the branelike terms is equivalent
to curving the space-time to obtain the AdS_5 X S^5 background. We commence the
study of the proposed NSR sigma-model by analyzing the scattering amplitudes
involving the branelike vertex operators.The analysis shows quite an unusual
momentum dependence of these scattering amplitudes.Comment: 15 pages more corrections and references adde

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