Higher algebraic KK-theory of finitely generated torsion modules over principal ideal domains

The main purpose of this paper is computing higher algebraic $K$-theory of Koszul complexes over principal ideal domains. The second purpose of this paper is giving examples of comparison techniques on algebraic $K$-theory for Waldhausen categories without the factorization axiom

Fibration theorem for Waldhausen K-theory

The goal of this note is to give a variant of the generic fibration theorem for Waldhausen K-theory without assuming the factorization axiom

Negative K-groups of abelian categories

We prove that negative K-groups of small abelian categories are trivial

Local Gersten's conjecture for regular system of parameters

In this paper, we show local Gersten's conjecture for regular system of parameters. As its consequence we obtain Gersten's conjecture for a commutative regular local ring and smooth over a commutative discrete valuation ring

Gersten's conjecture for commutative discrete valuation rings

The purpose of this article is to prove that Gersten's conjecture for a commutative discrete valuation ring is true. Combining with the result of \cite{GL87}, we learn that Gersten's conjecture is true if the ring is a commutative regular local, smooth over a commutative discrete valuation ring

Motivic interpretation of Milnor KK-groups attached to Jacobian varieties

In the paper M. Somekawa, {\it{On Milnor $K$-groups attached at semi-Abelian varieties}}, K-theory, \textbf{4} (1990) p.105, Somekawa conjectures that his Milnor K-group $K(k,G_1,...,G_r)$ attached to semi-abelian varieties $G_1$,...,$G_r$ over a field $k$ is isomorphic to ${\rm Ext}_{\mathcal{M}_k}^r(\mathbb{Z},G_1[-1] \otimes ... \otimes G_r[-1])$ where $\mathcal{M}_k$ is a certain category of motives over $k$. The purpose of this note is to give remarks on this conjecture, when we take $\mathcal{M}_k$ as Voevodsky's category of motives ${\rm DM}^{eff}_{-}(k)$ .Comment: 29 page

Delooping of the KK-theory of strictly derivable Waldhausen categories

In this short note, for a morphism of Waldhausen categories $f\colon \mathbb{A} = (\mathcal{A} ,w_{\mathbb{A}}) \to \mathbb{B} = (\mathcal{B},w_{\mathbb{B}})$, we will define $\operatorname{Cone} f$ to be a Waldhausen category. There exists the canonical morphism of Waldhausen categories $\kappa_f\colon \mathbb{B}\to \operatorname{Cone} f$. We will show that the sequence $\mathbb{A}\overset{f}{\to}\mathbb{B}\overset{\kappa_f}{\to}\operatorname{Cone}f$ induces fibration sequence of spaces $K(\mathbb{A})\overset{K(f)}{\to}K(\mathbb{B})\overset{K(\kappa_f)}{\to} K(\operatorname{Cone} f)$ on connective $K$-theory. Moreover we will define a notion of strictly derivable Waldhausen categories and define non-connective $K$-theory for strictly derivable Waldhausen categories

Quasi-weak equivalences in complicial exact categories

We introduce a notion of quasi-weak equivalences associated with weak-equivalences in an exact category. It gives us a delooping for (idempotent complete) exact categories and a condition that the negative $K$-group of an exact category becomes trivial

Generalized Koszul resolutions

The main objective of this paper is to generalize a notion of Koszul resolutions and charcterizing modules which admits such a resolution. We turn out that for a noetherian ring $A$ and a coherent $A$ module $M$, $M$ has a two dimensional generalized Koszul resolution if and only if $M$ is a pure weight two module in the sense of \cite{HM09}.Comment: 14 page

What makes a multi-complex exact?

In this paper, we give a sufficient condition which makes the total complex of a cube exact. This can be regarded as a variant of the Buchsbaum-Eisenbud theorem which gives a characterization of what makes a complex of finitely generated free modules exact in terms of the grade of the Fitting ideals of boundary maps of the complex