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Filling radii of finitely presented groups

Steve M. Gersten and Tim R. Riley

Quarterly Journal of Mathematics (Oxford)), 53(1), pages 31–45, 2002.

The filling radius function R of Gromov measures the minimal radii of van Kampen diagrams filling edge-circuits w in the Cayley 2-complex of a finite presentation P. It is known that the Dehn function can be bounded above by a double exponential in R and the length of the loop, and it is an open question whether a single exponential bound suffices. We define the upper filling radius rmax of w to be the maximal radius of minimal area fillings of w and let rmax be the corresponding filling function, so rmax(n) is the maximum of rmax(w) over all edge-circuits w of length at most n. We show that the Dehn function is bounded above by a single exponential in rmax and the length of the loop. We give an example of a finite presentation P where R is linearly bounded but rmax grows exponentially.

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