Spectral invariance of $\ast$-representations of twisted convolution algebras with applications in Gabor analysis

Abstract

We show spectral invariance for faithful $\ast$-representations for a class of twisted convolution algebras. More precisely, if $G$ is a locally compact group with a continuous $2$-cocycle $c$ for which the corresponding Mackey group $G_c$ is $C^{\ast }$-unique and symmetric, then the twisted convolution algebra $L^1(G,c)$ is spectrally invariant in $\mathbb{B}(\mathcal{H})$ for any faithful $\ast$-representation of $L^1(G,c)$ as bounded operators on a Hilbert space $\mathcal{H}$. As an application of this result we give a proof of the statement that if $\Delta$ is a closed cocompact subgroup of the phase space of a locally compact abelian group $G^{\prime }$, and if $g$ is some function in the Feichtinger algebra $S_0(G^{\prime })$ that generates a Gabor frame for $L^2(G^{\prime })$ over $\Delta$, then both the canonical dual atom and the canonical tight atom associated to $g$ are also in $S_0(G^{\prime })$. We do this without the use of periodization techniques from Gabor analysis.

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