Construction of representations of compact special linear groups of degree two

Abstract

We construct the finite-dimensional continuous complex representations of $\mathrm{SL}_2$ over compact discrete valuation rings of even residual characteristic. We also prove that the complex group algebras of $\mathrm{SL}_2$ over finite quotient rings of such compact discrete valuation rings depend on the characteristic of the ring. In particular, we prove that the group algebras $\mathbb{C}[\mathrm{SL}_2 (\mathbb{Z}/2^r \mathbb{Z})]$ and $\mathbb{C}[\mathrm{SL}_2 (\mathbb{F}_2 [t]/(t^r ))]$ are not isomorphic for any $r\geq 4.$