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A devissage--type theorem in algebraic $K$-theory is a statement that identifies the $K$-theory of a Waldhausen category $mathscr{C}$ in terms of the $K$-theories of a collection of Waldhausen subcategories of $mathscr{C}$ when a devissage condition about the existence of appropriate finite filtrations is satisfied. We distinguish between devissage theorems of emph{single type} and of emph{multiple type} depending on the number of Waldhausen subcategories and their properties. The main representative examples of such theorems are Quillens original devissage theorem for abelian categories (single type) and Waldhausens theorem on spherical objects for more general Waldhausen categories (multiple type). In this paper, we study some general aspects of devissage--type theorems and prove a general devissage theorem of single type and a general devissage theorem of multiple type.
We study a categorical construction called the cobordism category, which associates to each Waldhausen category a simplicial category of cospans. We prove that this construction is homotopy equivalent to Waldhausens $S_{bullet}$-construction and ther
For a group G that splits as an amalgamation of A and B over a common subgroup C, there is an associated Waldhausen Nil-group, measuring the failure of Mayer-Vietoris for algebraic K-theory. Assume that (1) the amalgamation is acylindrical, and (2) t
We define a $K$-theory for pointed right derivators and show that it agrees with Waldhausen $K$-theory in the case where the derivator arises from a good Waldhausen category. This $K$-theory is not invariant under general equivalences of derivators,
This paper is the first in a series in which we offer a new framework for hermitian K-theory in the realm of stable $infty$-categories. Our perspective yields solutions to a variety of classical problems involving Grothendieck-Witt groups of rings an
For G a finite group and X a G-space on which a normal subgroup A acts trivially, we show that the G-equivariant K-theory of X decomposes as a direct sum of twisted equivariant K-theories of X parametrized by the orbits of the conjugation action of G