In algebraic topology, a branch of mathematics, a spectrum is an object representing a generalized cohomology theory. Every such cohomology theory is representable, as follows from Brown's representability theorem. This means that, given a cohomology theory,there exist spaces such that evaluating the cohomology theory in degree on a space is equivalent to computing the homotopy classes of maps to the space , that is.Note there are several different of spectra leading to many technical difficulties, but they all determine the same , known as the stable homotopy category. This is one of the key points for introducing spectra because they form a natural home for stable homotopy theory.
There are many variations of the definition: in general, a spectrum is any sequence of pointed topological spaces or pointed simplicial sets together with the structure maps , where is the smash product. The smash product of a pointed space with a circle is homeomorphic to the reduced suspension of , denoted .
The following is due to Frank Adams (1974): a spectrum (or CW-spectrum) is a sequence of CW complexes together with inclusions of the suspension as a subcomplex of .
For other definitions, see symmetric spectrum and simplicial spectrum.
One of the most important invariants of spectra are the homotopy groups of the spectrum. These groups mirror the definition of the stable homotopy groups of spaces since the structure of the suspension maps is integral in its definition. Given a spectrum define the homotopy group as the colimitwhere the maps are induced from the composition of the map (that is, given by functoriality of ) and the structure map . A spectrum is said to be connective if its are zero for negative k.
Eilenberg–Maclane spectrum
Consider singular cohomology with coefficients in an abelian group . For a CW complex , the group can be identified with the set of homotopy classes of maps from to , the Eilenberg–MacLane space with homotopy concentrated in degree . We write this asThen the corresponding spectrum has -th space ; it is called the Eilenberg–MacLane spectrum of .
This page is automatically generated and may contain information that is not correct, complete, up-to-date, or relevant to your search query. The same applies to every other page on this website. Please make sure to verify the information with EPFL's official sources.
This course will provide an introduction to model category theory, which is an abstract framework for generalizing homotopy theory beyond topological spaces and continuous maps. We will study numerous
We propose an introduction to homotopy theory for topological spaces. We define higher homotopy groups and relate them to homology groups. We introduce (co)fibration sequences, loop spaces, and suspen
Singular cohomology is defined by dualizing the singular chain complex for spaces. We will study its basic properties, see how it acquires a multiplicative structure and becomes a graded commutative a
In the mathematical field of algebraic topology, the homotopy groups of spheres describe how spheres of various dimensions can wrap around each other. They are examples of topological invariants, which reflect, in algebraic terms, the structure of spheres viewed as topological spaces, forgetting about their precise geometry. Unlike homology groups, which are also topological invariants, the homotopy groups are surprisingly complex and difficult to compute.
In mathematics, a triangulated category is a with the additional structure of a "translation functor" and a class of "exact triangles". Prominent examples are the of an , as well as the . The exact triangles generalize the short exact sequences in an abelian category, as well as fiber sequences and cofiber sequences in topology. Much of homological algebra is clarified and extended by the language of triangulated categories, an important example being the theory of sheaf cohomology.
In mathematics, the homotopy category is a built from the category of topological spaces which in a sense identifies two spaces that have the same shape. The phrase is in fact used for two different (but related) categories, as discussed below. More generally, instead of starting with the category of topological spaces, one may start with any and define its associated homotopy category, with a construction introduced by Quillen in 1967. In this way, homotopy theory can be applied to many other categories in geometry and algebra.
1H MRS in the cerebellum was used to study the effect of 2-octynohydroxamic acid (2-octynoHA) treatment on the brain of bile duct ligated (BDL) rats (type C hepatic encephalopathy). The study included four groups of rats: negative control group (rats recei ...
Twisted topological Hochschild homology of Cn-equivariant spectra was introduced by Angeltveit, Blumberg, Gerhardt, Hill, Lawson, and Mandell, building on the work of Hill, Hopkins, and Ravenel on norms in equivariant homotopy theory. In this paper we intr ...
Let h be a connective homology theory. We construct a functorial relative plus construction as a Bousfield localization functor in the category of maps of spaces. It allows us to associate to a pair (X,H), consisting of a connected space X and an hperfect ...