Absolute stable rank and Witt cancellation for noncommutative rings.
There are errors in the proof of uniqueness of arithmetic subgroups of the smallest covolume. In this note we correct the proof, obtain certain results which were stated as a conjecture, and we give several remarks on further developments.
Si studiano, nell'ambito della teoria delle forme trilineari, le cosidette -forme simmetriche, pervenendo ad un teorema di struttura utile per una possibile classificazione, ancora inesistente, di tali -forme.
This paper presents algorithms for quadratic forms over a formally real algebraic function field K of one variable over a fixed real closed field k. The algorithms introduced in the paper solve the following problems: test whether an element is a square, respectively a local square, compute Witt index of a quadratic form and test if a form is isotropic/hyperbolic. Finally, we remark on a method for testing whether two function fields are Witt equivalent.
We investigate the almost regular positive definite integral quaternary quadratic forms. In particular, we show that every such form is -anisotropic for at most one prime number . Moreover, for a prime there is an almost regular -anisotropic quaternary quadratic form if and only if . We also study the genera containing some almost regular -anisotropic quaternary form. We show several finiteness results concerning the families of these genera and give effective criteria for almost regularity....
Let be a Galois extension with Galois group . We study the set of -linear combinations of characters in the Burnside ring which give rise to -linear combinations of trace forms of subextensions of which are trivial in the Witt ring W of . In particular, we prove that the torsion subgroup of coincides with the kernel of the total signature homomorphism.
An elementary proof is given of an arithmetic formula, which was stated but not proved by Liouville. An application of this formula yields a formula for the number of representations of a positive integer as the sum of twelve triangular numbers.