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arXiv:2009.04763 · International Journal of Modern Physics A

The operator algebra at the Gaussian fixed-point

H. Sonoda

Published Jun 2, 2021• 0 citations
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Abstract

We consider the multiple products of relevant and marginal scalar composite operators at the Gaussian fixed-point in [Formula: see text] dimensions. This amounts to perturbative construction of the [Formula: see text] theory where the parameters of the theory are momentum-dependent sources. Using the exact renormalization group (ERG) formalism, we show how the scaling properties of the sources are given by the short-distance singularities of the multiple products.

DOI
10.1142/s0217751x21501062

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We study how to compute the operator product expansion coefficients in the exact renormalization group formalism. After discussing possible strategies, we consider some examples explicitly, within the $\ensuremath{\epsilon}$ expansions, for the Wilson-Fisher fixed points of the real scalar theory in $d=4\ensuremath{-}\ensuremath{\epsilon}$ dimensions and the Lee-Yang model in $d=6\ensuremath{-}\ensuremath{\epsilon}$ dimensions. Finally we discuss how our formalism may be extended beyond perturbation theory.
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The large distance behaviour, near the critical temperature, of continuous phase transitions with short range interactions can be reproduced by an effective local field theory. Within this framework, the universal properties of the large distance can be determined by finding fixed points of general, functional renormalization group (RG) equations (Wilson, Wegner). For dimension D > 4, the large scale behavior is governed by the Gaussian fixed point (related to mean field theory), while for D < 4 the Gaussian fixed point is unstable. Near D = 4, the RG equations can be solved in the form of an ǫ = 4 − D expansion, a new stable fixed point is found and this leads to the famous Wilson-Fisher expansion for critical exponents and other universal quantities. Moreover, one realizes that, in this framework, the effective field theory can be reduced to a renormalizable field theory and, at leading order in the critical domain, the much simpler quantum field theory renormalization group can be used. A number of physicists, including the Saclay group (Brezin, Le Guillou, Zinn-Justin) have developed sophisticated field theory techniques, to prove general scaling laws and to calculate exponents to higher orders [1].