The purpose of this paper is to collect the homotopical methods used in the development of the theory of flows initialized by author’s paper “A model category for the homotopy theory of concurrency”. It is presented generalizations of the classical Whitehead theorem inverting weak homotopy equivalences between CW-complexes using weak factorization systems. It is also presented methods of calcul...

This paper presents a graph-based formalism for object-oriented class structure specifications. The formalism combines labelled graphs with partial orders, to adequately model the (single) inheritance relation among objects and the overriding relation between methods within derived classes. The semantics of system extension by inheritance and aggregation is then defined as colimits in a suitabl...

We show that if U∗ is a hypercover of a topological space X then the natural map hocolim U∗→X is a weak equivalence. This fact is used to construct topological realization functors for the A1-homotopy theory of schemes over real and complex fields. In an appendix, we also prove a theorem about computing homotopy colimits of spaces that are not cofibrant. Mathematics Subject Classification (2000...

Today, Nicky spoke on a few approaches to higher K-theory. Let C be a pointed ∞-category with finite colimits (as in Lurie’s approach) or a category with cofibrations and weak equivalences satisfying certain axioms (as in Waldhausen’s approach). Recall that K0(C) was defined to be the free abelian group on isomorphism classes of objects of C modulo [X] = [X′] + [X′′] whenever we have a pushout ...

We give a brief survey of higher algebraic K-theory and its connection to motivic cohomology. We start with limits and colimits, and then pass to the combinatorial construction of topological spaces by means of “systems of simplices”, usefully mediated by simplicial sets. Definitions of K-theory are offered, and the main theorems are stated. A definition of motivic cohomology is offered and its...

We explain how the notion of homotopy colimits gives rise to that of mapping spaces, even in categories which are not simplicial. We apply the technique of model approximations and use elementary properties of the category of spaces to be able to construct resolutions. We prove that the homotopy category of any monoidal model category is always a central algebra over the homotopy category of Sp...

Are all subcategories of locally finitely presentable categories that are closed under limits and λ-filtered colimits also locally presentable? For full subcategories the answer is affirmative. Makkai and Pitts proved that in the case λ = א0 the answer is affirmative also for all iso-full subcategories, i. e., those containing with every pair of objects all isomorphisms between them. We discuss...

Generalizing the fact that Scott’s continuous lattices form the equational hull of the class of all algebraic lattices, we describe an equational hull of LFP, the category of locally finitely presentable categories, over CAT. Up to a set-theoretical hypothesis this hull is formed by the category of all precontinuous categories, i.e., categories in which limits and filtered colimits distribute. ...