In this paper we show that the convolution product of "almost characters" of a connected reductive group over a finite field is given by "structure constants" whose leading coefficients can be interpreted in K-theoretic terms and in particular are natural numbers. I wish to thank M. Finkelberg and V. Ostrik for comments on an earlier version of this paper.
"Convolution of Almost Characters." Asian J. Math. 8 (4) 769 - 772, December, 2004.