No abstract

Let G be a finite group and Irr(G) the set of all irreducible complex characters of G. Define the codegree of χ ∈ Irr(G) as cod(χ) :=and denote by cod(G) := {cod(χ)|χ ∈ Irr(G)} the codegree set of G. Let H be one of the 26 sporadic simple groups. In this paper, we show that H is determined up to isomorphism by cod(H).

Let G be a finite group and Irr(G) the set of all irreducible complex characters of G. Define the codegree of χ ∈ Irr(G) as cod(χ) :=and denote by cod(G) := {cod(χ) | χ ∈ Irr(G)} the codegree set of G. Let An be an alternating group of degree n ≥ 5. In this paper, we show that An is determined up to isomorphism by cod(An).

A toric code, introduced by Hansen to extend the Reed-Solomon code as a k-dimensional subspace of F n q , is determined by a toric variety or its associated integral convex polytope P ⊆ [0, q − 2] n , where k = |P ∩ Z n | (the number of integer lattice points of P ). There are two relevant parameters that determine the quality of a code: the information rate, which measures how much information is contained in a single bit of each codeword; and the relative minimum distance, which measures how many errors can be corrected relative to how many bits each codeword has. Soprunov and Soprunova defined a good infinite family of codes to be a sequence of codes of unbounded polytope dimension such that neither the corresponding information rates nor relative minimum distances go to 0 in the limit. We examine different ways of constructing families of codes by considering polytope operations such as the join and direct sum. In doing so, we give conditions under which no good family can exist and strong evidence that there is no such good family of codes.