### Comparing invariants of SK_{1}, by Tim Wouters

[ March 18, 2010: updated preprint received, replacing the March 8, 2010, version. ]

In this text, we compare several invariants of the reduced Whitehead group SK_{1}
of a central simple algebra.

For biquaternion algebras, we compare a generalised invariant of Suslin as
constructed by the author in a previous article to an invariant introduced by
Knus-Merkurjev-Rost-Tignol. Using explicit computations, we prove these
invariants are essentially the same.

We also prove the non-triviality of an invariant introduced by Kahn. To obtain
this result, we compare Kahn's invariant to an invariant introduced by Suslin
in 1991 which is non-trivial for Platonov's examples of non-trivial SK_{1}. We
also give a formula for the value on the centre of the tensor product of two
symbol algebras.

Tim Wouters <tim@wouters.in>