In mathematics, well-behaved

topological space In mathematics, a topological space is, roughly speaking, a geometrical space in which closeness is defined but cannot necessarily be measured by a numeric distance. More specifically, a topological space is a set whose elements are called po ...

s can be localized at primes, in a similar way to the

localization of a ring In commutative algebra and algebraic geometry, localization is a formal way to introduce the "denominators" to a given ring or module. That is, it introduces a new ring/module out of an existing ring/module ''R'', so that it consists of fraction ...

at a prime. This construction was described by

Dennis Sullivan Dennis Parnell Sullivan (born February 12, 1941) is an American mathematician known for his work in algebraic topology, geometric topology, and dynamical systems. He holds the Albert Einstein Chair at the City University of New York Graduate ...

in 1970 lecture notes that were finally published in . The reason to do this was in line with an idea of making

topology In mathematics, topology (from the Greek words , and ) is concerned with the properties of a geometric object that are preserved under continuous deformations, such as stretching, twisting, crumpling, and bending; that is, without closing ...

, more precisely

algebraic topology Algebraic topology is a branch of mathematics that uses tools from abstract algebra to study topological spaces. The basic goal is to find algebraic invariants that classify topological spaces up to homeomorphism, though usually most classify ...

, more geometric. Localization of a space ''X'' is a geometric form of the algebraic device of choosing 'coefficients' in order to simplify the algebra, in a given problem. Instead of that, the localization can be applied to the space ''X'', directly, giving a second space ''Y''.

Definitions

We let ''A'' be a subring of the

rational number In mathematics, a rational number is a number that can be expressed as the quotient or fraction of two integers, a numerator and a non-zero denominator . For example, is a rational number, as is every integer (e.g. ). The set of all rat ...

s, and let ''X'' be a simply connected

CW complex A CW complex (also called cellular complex or cell complex) is a kind of a topological space that is particularly important in algebraic topology. It was introduced by J. H. C. Whitehead (open access) to meet the needs of homotopy theory. This cl ...

. Then there is a simply connected CW complex ''Y'' together with a map from ''X'' to ''Y'' such that *''Y'' is ''A''-local; this means that all its homology groups are modules over ''A'' *The map from ''X'' to ''Y'' is universal for (homotopy classes of) maps from ''X'' to ''A''-local CW complexes. This space ''Y'' is unique up to

homotopy equivalence In topology, a branch of mathematics, two continuous functions from one topological space to another are called homotopic (from grc, ὁμός "same, similar" and "place") if one can be "continuously deformed" into the other, such a defor ...

, and is called the localization of ''X'' at ''A''. If ''A'' is the localization of Z at a prime ''p'', then the space ''Y'' is called the localization of ''X'' at ''p'' The map from ''X'' to ''Y'' induces

isomorphism In mathematics, an isomorphism is a structure-preserving mapping between two structures of the same type that can be reversed by an inverse mapping. Two mathematical structures are isomorphic if an isomorphism exists between them. The word i ...

s from the ''A''-localizations of the homology and homotopy groups of ''X'' to the homology and homotopy groups of ''Y''.

References

* *{{citation, title=Geometric Topology: Localization, Periodicity and Galois Symmetry: The 1970 MIT Notes , series=K-Monographs in Mathematics , first= Dennis P., last= Sullivan, authorlink=Dennis Sullivan, editor-first= Andrew , editor-last=Ranicki, editor-link=Andrew Ranicki, isbn= 1-4020-3511-X, year=2005, url=http://www.maths.ed.ac.uk/~aar/surgery/gtop.pdf, publisher=Springer, location=Dordrecht Homotopy theory Localization (mathematics)

Definitions

See also

References