30,270 research outputs found
Quantization of the Nonlinear Sigma Model Revisited
We revisit the subject of perturbatively quantizing the nonlinear sigma model
in two dimensions from a rigorous, mathematical point of view. Our main
contribution is to make precise the cohomological problem of eliminating
potential anomalies that may arise when trying to preserve symmetries under
quantization. The symmetries we consider are twofold: (i) diffeomorphism
covariance for a general target manifold; (ii) a transitive group of isometries
when the target manifold is a homogeneous space. We show that there are no
anomalies in case (i) and that (ii) is also anomaly-free under additional
assumptions on the target homogeneous space, in agreement with the work of
Friedan. We carry out some explicit computations for the -model. Finally,
we show how a suitable notion of the renormalization group establishes the
Ricci flow as the one loop renormalization group flow of the nonlinear sigma
model.Comment: 51 page
Gauge theories with graded differential Lie algebras
We present a mathematical framework of gauge theories that is based upon a
skew-adjoint Lie algebra and a generalized Dirac operator, both acting on a
Hilbert space.Comment: 10 pages, LaTeX2e, extended version (references and comments on the
construction of physical models and on the relation to the axioms of
noncommutative geometry added
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