## Arithmetic of Hermitian forms

### Summary

Summary: We investigate the following two problems on a hermitian form $\Phi$ over an algebraic number field: (1) classification of $\Phi$ over the ring of algebraic integers; (2) hermitian Diophantine equations. The same types of problems for quadratic forms were treated in the author's previous articles. Here we discuss the hermitian case. Problem (2) concerns an equation $\x\Phi\cdot\tr \x^{\r}=\Psi$, where $\Phi$ and $\Psi$ represent hermitian forms. We connect the number of such $\x$ modulo a group of units with the class number and mass of the unitary group of a form $\Th$ such that $\Phi\approx\Psi\oplus\Th$.

### Mathematics Subject Classification

11E39, 11E41, 11D09