34,335 research outputs found
Primitive Vassiliev Invariants and Factorization in Chern-Simons Perturbation Theory
The general structure of the perturbative expansion of the vacuum expectation
value of a Wilson line operator in Chern-Simons gauge field theory is analyzed.
The expansion is organized according to the independent group structures that
appear at each order. It is shown that the analysis is greatly simplified if
the group factors are chosen in a certain way that we call canonical. This
enables us to show that the logarithm of a polinomial knot invariant can be
written in terms of primitive Vassiliev invariants only.Comment: 15 pages, latex, 2 figure
Some Global Aspects of Duality is String Theory
We explore some of the global aspects of duality transformations in String
Theory and Field Theory. We analyze in some detail the equivalence of dual
models corresponding to different topologies at the level of the partition
function and in terms of the operator correspondence for abelian duality. We
analyze the behavior of the cosmological constant under these transformations.
We also explore several examples of non-abelian duality where the classical
background interpretation can be maintained for the original and the dual
theories. In particular we construct a non-abelian dual of which
turns out to be a three-dimensional black holeComment: 31pp. One figure available upon request. CERN-TH-6991/6
Remarks on Time-Space Noncommutative Field Theories
We propose a physical interpretation of the perturbative breakdown of
unitarity in time-like noncommutative field theories in terms of production of
tachyonic particles. These particles may be viewed as a remnant of a continuous
spectrum of undecoupled closed-string modes. In this way, we give a unified
view of the string-theoretical and the field-theoretical no-go arguments
against time-like noncommutative theories. We also perform a quantitative study
of various locality and causality properties of noncommutative field theories
at the quantum level.Comment: 19 pages, LaTe
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