Robuta

https://www.preprints.org/manuscript/201809.0604 The Riemann Zeta Function of a Matrix/Tensor[v1] | Preprints.org This paper attempts to extend the Riemann Zeta function of a complex number to a function of a matrix and/or a tensor $A$, namely $$\zeta (A)=\sum... function of a matrixriemann zeta