On Infinitesimal $τ$-Isospectrality of Locally Symmetric Spaces
Chandrasheel Bhagwat, Kaustabh Mondal, Gunja Sachdeva
Abstract
Let $(τ, V_τ)$ be a finite dimensional representation of a maximal compact subgroup $K$ of a connected non-compact semisimple Lie group $G$, and let $Γ$ be a uniform torsion-free lattice in $G$. We obtain an infinitesimal version of the celebrated Matsushima-Murakami formula, which relates the dimension of the space of automorphic forms associated to $τ$ and multiplicities of irreducible $τ^\vee$-spherical spectra in $L^2(Γ\backslash G)$. This result gives a promising tool to study the joint spectra of all central operators on the homogenous bundle associated to the locally symmetric space and hence its infinitesimal $τ$-isospectrality. Along with this we prove that the almost equality of $τ$-spherical spectra of two lattices assures the equality of their $τ$-spherical spectra.
