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Register a new userCorrigendum to Intersection homology with field coefficients: K-Witt spaces and K-Witt bordism
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Authors
Greg Friedman
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This note corrects an error in the char(K)=2 case of the authors computation of the bordism groups of K-Witt spaces for the field K.
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We establish a fibre sequence relating the classical Grothendieck-Witt theory of a ring $R$ to the homotopy $mathrm{C}_2$-orbits of its K-theory and Ranickis original (non-periodic) symmetric L-theory. We use this fibre sequence to remove the assumption that 2 is a unit in $R$ from various results about Grothendieck-Witt groups. For instance, we solve the homotopy limit problem for Dedekind rings whose fraction field is a number field, calculate the various flavours of Grothendieck-Witt groups of $mathbb{Z}$, show that the Grothendieck-Witt groups of rings of integers in number fields are finitely generated, and that the comparison map from quadratic to symmetric Grothendieck-Witt theory of Noetherian rings of global dimension $d$ is an equivalence in degrees $geq d+3$. As an important tool, we establish the hermitian analogue of Quillens localisation-devissage sequence for Dedekind rings and use it to solve a conjecture of Berrick-Karoubi.
Torsion sensitive intersection homology was introduced to unify severa
We compare the sheaf-theoretic and singular cha
We study the algebraic $K$-theory and Grothendieck-Witt theory of proto-exact categories of vector bundles over monoid schemes. Our main results are the complete description of the algebraic $K$-theory space of an integral monoid scheme $X$ in terms of its Picard group $operatorname{Pic}(X)$ and pointed monoid of regular functions $Gamma(X, mathcal{O}_X)$ and a description of the Grothendieck-Witt space of $X$ in terms of an additional involution on $operatorname{Pic}(X)$. We also prove space-level projective bundle formulae in both settings.
We indicate two short proofs of the Goresky-MacPherson topological invariance of intersection homology. One proof is very short but requires the Goresky-MacPherson support and cosupport axioms; the other is slightly longer but does not require these axioms and so is adaptable to more general perversities.
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