arXiv subjects

A. Zadra

Publications and source records attributed to A. Zadra.

8 recordsLinked to original sources

arXiv1997

Algebra of non-local charges in the O(N) WZNW model at and beyond criticality

We derive the classical algebra of the non-local conserved charges in the O(N) WZNW model and analyze its dependence on the coupling constant of the Wess-Zumino term. As in the non-linear sigma model, we find cubic deformations of the O(N) affine algebra. The surprising result is that the cubic algebra of the WZNW non-local charges does not obey the Jacobi identity, thus opposing our expectations from the known Yangian symmetry of this model.

solv-int↗

arXiv1996

Classical and quantum N=1 super $W_\infty$-algebras

We construct higher-spin N=1 super algebras as extensions of the super Virasoro algebra containing generators for all spins $s\ge 3/2$. We find two distinct classical (Poisson) algebras on the phase super space. Our results indicate that only one of them can be consistently quantized.

hep-th↗

arXiv1996

Higher spin constraints and the super $( W_{\infty\over 2}\oplus W_{{1+\infty}\over 2})$ algebra in the super eigenvalue model

We show that the partition function of the super eigenvalue model satisfies an infinite set of constraints with even spins $s=4,6,\cdots,\infty$. These constraints are associated with half of the bosonic generators of the super $\left( W_{\infty \over 2}\oplus W_{{1+\infty}\over 2}\right)$ algebra. The simplest constraint $(s=4)$ is shown to be reducible to the super Virasoro constraints, previously used to construct the model. All results hold for finite $N$.

hep-th↗

arXiv1996

Screening in Two-dimensional QCD

We discuss the issue of screening and confinement of external colour charges in bosonised two-dimensional quantum chromodynamics. Our computation relies on the static solutions of the semi-classical equations of motion. The significance of the different representations of the matter field is explicitly studied. We arrive at the conclusion that the screening phase prevails, even in the presence of a small mass term for the fermions. To confirm this result further, we outline the construction of operators corresponding to screened quarks.

hep-th↗

arXiv1995

Algebra of Non-Local Charges in Supersymmetric Non-Linear Sigma Models

We propose a graphic method to derive the classical algebra (Dirac brackets) of non-local conserved charges in the two dimensional supersymmetric non-linear $O(N)$ sigma model. As in the purely bosonic theory we find a cubic Yangian algebra. We also consider the extension of graphic methods to other integrable theories.

solv-int↗

arXiv1994

Non-critical superstrings: a comparison between continuum and discrete approaches

We review the relation between the matrix model and Liouville approaches to two-dimensional gravity as elaborated by Moore, Seiberg and Staudacher. Then, based on the supersymmetric Liouville formulation and the discrete eigenvalue model proposed by Alvarez-Gaumé, Itoyama, Mañes and Zadra, we extend the previous relation to the supersymmetric case. The minisuperspace approximation for the supersymmetric case is formulated, and the corresponding wave equation is found.

hep-th↗

arXiv1993

The Algebra of Non-Local Charges in Non-Linear Sigma Models

We obtain the exact Dirac algebra obeyed by the conserved non-local charges in bosonic non-linear sigma models. Part of the computation is specialized for a symmetry group $O(N)$. As it turns out the algebra corresponds to a cubic deformation of the Kac-Moody algebra. The non-linear terms are computed in closed form. In each Dirac bracket we only find highest order terms (as explained in the paper), defining a saturated algebra. We generalize the results for the presence of a Wess-Zumino term. The algebra is very similar to the previous one, containing now a calculable correction of order one unit lower.

hep-th↗

arXiv1991

Superloop Equations and Two Dimensional Supergravity

We propose a discrete model whose continuum limit reproduces the string susceptibility and the scaling dimensions of $(2,4m)$-minimal superconformal models coupled to $2D$-supergravity. The basic assumption in our presentation is a set of super-Virasoro constraints imposed on the partition function. We recover the Neveu-Schwarz and Ramond sectors of the theory, and we are also able to evaluate all planar loop correlation functions in the continuum limit. We find evidence to identify the integrable hierarchy of non-linear equations describing the double scaling limit as a supersymmetric generalization of KP studied by Rabin.

hep-th↗