E m m y - N o e t h
e r - P r o f e s s u r 2 0 0 3
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Mathematisches
Institut
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Vorlesung von Prof. Sylvie Paycha
FROM
HEAT-OPERATORS TO ANOMALIES
a walk through various regularization (renormalization) techniques
in physics and mathematics

Abstract:
Symmetries of a classical
action functional describing a physical system (conservation laws for
such symmetries were investigated by Emmy Noether), can "break" after a
quantization procedure when going to the quantized action functional.
Anomalies in physics measure this "breaking" of symmetry at the
quantum level. We want to relate this type of anomaly to anomalies one
encounters in mathematics when extracting finite parts of diverging
quantities. For example, the zeta-determinant, which is an essential
tool to define quantized actions functional in physics, is a way of
extracting a finite part from an otherwise diverging determinant, the
eta-invariant is a way to define the phase of such a zeta-determinant.
Some anomalies in physics lie in logarithmic variations of partition
functions defined by zeta-regularization techniques, and can be
interpreted as regularized traces of some pseudo-differential operator.
For the sake of simplicity (even if this is rather non physical since
it boils down to working in a 0 dimensional space !), we shall focus on
regularized traces of operators on the circle, describing tracial
anomalies accuring from taking finite parts. We relate local terms
arising in index theory and anomalies in quantum field theory to such
tracial anomalies.
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