Department of Physics Papers

Document Type

Journal Article

Date of this Version

1991

Publication Source

Communications in Mathematical Physics

Volume

22

Issue

13

Start Page

273

Last Page

290

DOI

10.1007/BF02099493

Abstract

In string theory and in topological quantum field theory one encounters operators whose effect in correlation functions is simply to measure the topology of 2d spacetime. In particular these 'dilation'-type operators count the number of other operators via contact terms with the latter. While contact terms in general have a reputation for being convention-dependent, the ones considered here are perfectly well-defined by virtue of their simple geometrical meaning: They reflect the geometry of the stable-curve compactification. We give an unambiguous prescription for their evaluation which involves no analytic continuation in momenta.

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Date Posted: 01 May 2017

This document has been peer reviewed.