Let 
be an algebraic group. 
together with the discrete topology is a locally compact group
and one may consider the counting measure as a left invariant Haar
measure on 
.
Then 
denoted 
and is called a discrete group algebra.
Discrete Group Algebra
See also
Discrete Group, Discrete Group TheoryThis entry contributed by Mohammad Sal Moslehian
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References
Bonsall, F. F. and Duncan, J. Complete Normed Algebras. New York: Springer-Verlag, 1973.Referenced on Wolfram|Alpha
Discrete Group AlgebraCite this as:
Moslehian, Mohammad Sal. "Discrete Group Algebra." From MathWorld--A Wolfram Web Resource, created by Eric W. Weisstein. https://mathworld.wolfram.com/DiscreteGroupAlgebra.html