an:07138351
Zbl 1444.14018
Hornbostel, Jens; Wendt, Matthias
Chow-Witt rings of classifying spaces for symplectic and special linear groups
EN
J. Topol. 12, No. 3, 916-966 (2019).
00440296
2019
j
14C17 19G12 19D45 55R40
Summary: We compute the Chow-Witt rings of the classifying spaces for the symplectic and special linear groups. In the structural description we give, contributions from real and complex realization are clearly visible. In particular, the computation of cohomology with \(\mathbf{I}^j\)-coefficients is done closely along the lines of Brown's computation of integral cohomology for special orthogonal groups. The computations for the symplectic groups show that Chow-Witt groups are a symplectically oriented ring cohomology theory. Using our computations for special linear groups, we also discuss the question when an oriented vector bundle of odd-rank splits off a trivial summand.