This is a survey paper on cohomology theories for A∞ and E∞ ring spectra. Different constructions and main properties of topological André-Quillen cohomology and of topological derivations are described. We give sample calculations of these cohomology theories and outline applications to the existence of A∞ and E∞ structures on various spectra. We also explain the relationship between topologic...

In the present article, we investigate a possibility of a real-valued map on the space of tuples of commuting trace-class self-adjoint operators, which behaves like the usual trace map on the space of trace-class linear operators. It turns out that such maps are related with continuous group homomorphisms from the Milnor’s K-group of the real numbers into the additive group of real numbers. Usi...

In this note, we describe a theory of linked Hom spaces which complements that of linked Grassmannians. Given two chains of vector bundles linked by maps in both directions, we give conditions for the space of homomorphisms from one chain to the other to be itself represented by a vector bundle. We apply this to present a more transparent version of an earlier construction of limit linear serie...

We uncover a somewhat surprising connection between spaces of multiplicative maps between A∞-ring spectra and topological Hochschild cohomology. As a consequence we show that such spaces become infinite loop spaces after looping only once. We also prove that any multiplicative cohomology operation in complex cobordisms theory MU canonically lifts to an A∞-map MU → MU . This implies, in particul...

We introduce and study two-parameter subproduct product systems of C⁎-algebras as the operator-algebraic analogues of, in relation to, Tsirelson's Hilbert spaces. Using several inductive limit techniques, we show that (i) any C⁎-subproduct system can be dilated to a C⁎-product system; (ii) admits unit, i.e., co-multiplicative family projections, assembled into C⁎-algebra, which comes equipped w...

In this article we generalize both ordinary and permutation voltage constructions to obtain all branched coverings of maps. We approach a map as a set of flags together with three fixed-point-free involutions and relate this approach with other standard representations. We define a lift as a function from these flags into a group. Ordinary voltage and ordinary current assignments are special ca...

The most powerful feature of categories of posets with directed sups is the ability to solve domain equations such as D ∼= D. A crucial ingredient of this technique is the fact that for certain kinds of diagrams (in particular sequences of “projection pairs”) the limit and colimit are isomorphic. This much is known to everyone in the subject: what appears not to be generally known is (i) that w...

Recall that a continuous function $fcolon Xto Y$ between Tychonoff spaces is proper if and only if the Stone extension $f^{beta}colon beta Xtobeta Y$ takes remainder to remainder, in the sense that $f^{beta}[beta X-X]subseteq beta Y-Y$. We introduce the notion of ``taking remainder to remainder" to frames, and, using it, we define a frame homomorphism $hcolon Lto M$ to be $beta$-proper, $lambd...

Let $G$ be a countable monoid and let $A$ an Artinian group (resp. module). $\Sigma \subset A^G$ closed subshift which is also subgroup submodule) of $A^G$. Suppose that $\Gamma$ finitely generated consisting pairwise commuting cellular automata \to \Sigma$ are homomorphisms groups modules) with binary operation given by composition maps. We show the valuation action on $\Sigma$ satisfies natur...