In this paper we consider the hyperbolic Kac–Moody algebra F associated with the generalized Cartan matrix ( 2 −2 0 −2 2 −1 0 −1 2 ) . Its connection to Siegel modular forms of genus 2 was first studied by A. Feingold and I. Frenkel. The denominator function of F is not an automorphic form. However, Gritsenko and Nikulin extended F to a generalized Kac–Moody algebra whose denominator function i...

Abstract We show that if a locally compact group $G$ is non-abelian, then the amenability constant of its Fourier algebra $\geq 3/2$, extending result [9] who proved this holds for finite non-abelian groups. Our lower bound, which known to be best possible, improves on results by previous authors and answers question raised [16]. To do this, we study minorant constant, related anti-diagonal in ...