Lecture IX - Functorial Property of the Fundamental Group
... We now turn to the most basic functor in algebraic topology namely, the π1 functor. Recall that the fundamental group of a space involves a base point and according to theorem (7.8) the fundamental group of a path connected space is unique upto isomorphism. However, this isomorphism is not canonical ...
... We now turn to the most basic functor in algebraic topology namely, the π1 functor. Recall that the fundamental group of a space involves a base point and according to theorem (7.8) the fundamental group of a path connected space is unique upto isomorphism. However, this isomorphism is not canonical ...
The Topologist`s Sine Curve We consider the subspace X = X ∪ X of
... for every positive integer n, we choose 0 < un < x(1/n) such that sin(1/un ) = (−1)n . Then, by the mean value theorem, there exists 0 < tn < 1/n such that x(tn ) = un . By construction, the sequence {tn } converges to 0, but {σ(tn )} does not converge. This contracdicts the continuity of σ at 0. Th ...
... for every positive integer n, we choose 0 < un < x(1/n) such that sin(1/un ) = (−1)n . Then, by the mean value theorem, there exists 0 < tn < 1/n such that x(tn ) = un . By construction, the sequence {tn } converges to 0, but {σ(tn )} does not converge. This contracdicts the continuity of σ at 0. Th ...
BBA IInd SEMESTER EXAMINATION 2008-09
... b) For every subset A of X, f ( A ) f ( A) c) For every closed subset B of Y, f 1 ( B) is closed in X ...
... b) For every subset A of X, f ( A ) f ( A) c) For every closed subset B of Y, f 1 ( B) is closed in X ...
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... that I could apply to such an object, so leaving the n out is unambiguous), and that (P0 , . . . , P̌i , . . . , Pn ) = (P0 , . . . , Pi−1 , Pi+1 , . . . , Pn ). It’s σ with the ith entry removed. So we have a homomorphism ∂n : Cn (X) → Cn−1 (X), and it satisfies the following property. Theorem 1.1 ...
... that I could apply to such an object, so leaving the n out is unambiguous), and that (P0 , . . . , P̌i , . . . , Pn ) = (P0 , . . . , Pi−1 , Pi+1 , . . . , Pn ). It’s σ with the ith entry removed. So we have a homomorphism ∂n : Cn (X) → Cn−1 (X), and it satisfies the following property. Theorem 1.1 ...
Chapter 5 Homotopy Theory
... • This product does not depend on the representatives of the homotopy classes. • Theorem. The n-th homotopy groups are groups. • The set π0 (X) is not a group; it is rather the number of independent component of X. • Proposition. Higher homotopy groups πn (X, x0 ), for any n ≥ 2, are Abelian. • Prop ...
... • This product does not depend on the representatives of the homotopy classes. • Theorem. The n-th homotopy groups are groups. • The set π0 (X) is not a group; it is rather the number of independent component of X. • Proposition. Higher homotopy groups πn (X, x0 ), for any n ≥ 2, are Abelian. • Prop ...
Geometry and Topology, Lecture 4 The fundamental group and
... A path in a topological space X is a continuous map α : I = [0, 1] → X . Starts at α(0) ∈ X and ends at α(1) ∈ X . Proposition The relation on X defined by x0 ∼ x1 if there exists a path α : I → X with α(0) = x0 , α(1) = x1 is an equivalence relation. Proof (i) Every point x ∈ X is related to itself ...
... A path in a topological space X is a continuous map α : I = [0, 1] → X . Starts at α(0) ∈ X and ends at α(1) ∈ X . Proposition The relation on X defined by x0 ∼ x1 if there exists a path α : I → X with α(0) = x0 , α(1) = x1 is an equivalence relation. Proof (i) Every point x ∈ X is related to itself ...
7. Homotopy and the Fundamental Group
... thus a deformation of the identity on K. Examples of convex subsets of Rn include Rn itself, any open ball B(x, �) and the boxes [a1 , b1 ] × · · · × [an , bn ]. More generally, there is always the retract {x0 } �→ X → {x0 }, which leads to the trivial homomorphisms of groups {e} → π1 (X, x0 ) → {e ...
... thus a deformation of the identity on K. Examples of convex subsets of Rn include Rn itself, any open ball B(x, �) and the boxes [a1 , b1 ] × · · · × [an , bn ]. More generally, there is always the retract {x0 } �→ X → {x0 }, which leads to the trivial homomorphisms of groups {e} → π1 (X, x0 ) → {e ...
Fibrations handout
... A (Hurewicz) fibration is a map p : E → B which has the homotopy lifting property with respect to all spaces. A Serre fibration is a map which has the homotopy lifting property (HLP) with respect the n-disk for all n ≥ 0. (Equivalently, a Serre fibration has the HLP with respect to all finite CW com ...
... A (Hurewicz) fibration is a map p : E → B which has the homotopy lifting property with respect to all spaces. A Serre fibration is a map which has the homotopy lifting property (HLP) with respect the n-disk for all n ≥ 0. (Equivalently, a Serre fibration has the HLP with respect to all finite CW com ...
Let X be a path-connected space and suppose that every map f: S^1
... y in Y there exists a neighborhood Ny of b, so that p-1(Ny) is a disjoint union of sets Ai each of which is mapped homeomorphically onto Ny by map p. 3) If X is a contractible space then the fundamental group is trivial. 4) A topological space X is called simply connected if it is path-connected and ...
... y in Y there exists a neighborhood Ny of b, so that p-1(Ny) is a disjoint union of sets Ai each of which is mapped homeomorphically onto Ny by map p. 3) If X is a contractible space then the fundamental group is trivial. 4) A topological space X is called simply connected if it is path-connected and ...
The Arithmetic Square (Lecture 32)
... Definition 2. Let f : X → Y be a map of topological spaces. We say that f is a rational homotopy equivalence if it induces an isomorphism on rational cohomology H∗ (Y ; Q) → H∗ (X; Q) (this is equivalent to the assertion that f induces an isomorphism on rational homology). We say that a space Z is r ...
... Definition 2. Let f : X → Y be a map of topological spaces. We say that f is a rational homotopy equivalence if it induces an isomorphism on rational cohomology H∗ (Y ; Q) → H∗ (X; Q) (this is equivalent to the assertion that f induces an isomorphism on rational homology). We say that a space Z is r ...
Notes on wedges and joins
... union, and z0 is the point obtained by identification of x0 with y0 . The wedge sum is written as (X, x0 ) ∨ (Y, Y0 ), or simply as X ∨ Y . The latter notation is generally misleading, as we do not explicitly specify the basepoints x0 and y0 in X and Y . Choosing different basepoints x0 , y0 in X an ...
... union, and z0 is the point obtained by identification of x0 with y0 . The wedge sum is written as (X, x0 ) ∨ (Y, Y0 ), or simply as X ∨ Y . The latter notation is generally misleading, as we do not explicitly specify the basepoints x0 and y0 in X and Y . Choosing different basepoints x0 , y0 in X an ...
Homotopy
... Two continuous functions from one topological space to another are called homotopic if one can be “continuously deformed” into the other, such a deformation being called a homotopy between the two functions. More precisely, we have the following definition. Definition 1.1. Let X, Y be topological sp ...
... Two continuous functions from one topological space to another are called homotopic if one can be “continuously deformed” into the other, such a deformation being called a homotopy between the two functions. More precisely, we have the following definition. Definition 1.1. Let X, Y be topological sp ...
H-spaces II
... In this section we show that compact Lie groups other than SO(3)k × T l do admit special 1-tori. This implies that our theorem 1.4 is indeed stronger than theorem 1.1 of [8]. 5.1. Proposition. Let G be a compact connected Lie group which is not isomorphic to SO(3)k × T l . Then G has a subgroup isom ...
... In this section we show that compact Lie groups other than SO(3)k × T l do admit special 1-tori. This implies that our theorem 1.4 is indeed stronger than theorem 1.1 of [8]. 5.1. Proposition. Let G be a compact connected Lie group which is not isomorphic to SO(3)k × T l . Then G has a subgroup isom ...
Problems for the exam
... 1. Let p ∈ CP2 and q ∈ RP3 . Is there a compact surface which is homotopy equivalent to CP2 \ {p} ? Is there a compact surface which is homotopy equivalent to RP3 \ {q} ? 2. Does the Borsuk-Ulam Theorem hold for the torus? In other words, is it true that for every continuous map f : S 1 × S 1 → R2 , ...
... 1. Let p ∈ CP2 and q ∈ RP3 . Is there a compact surface which is homotopy equivalent to CP2 \ {p} ? Is there a compact surface which is homotopy equivalent to RP3 \ {q} ? 2. Does the Borsuk-Ulam Theorem hold for the torus? In other words, is it true that for every continuous map f : S 1 × S 1 → R2 , ...
THE HIGHER HOMOTOPY GROUPS 1. Definitions Let I = [0,1] be
... The first part of the theorem is obvious while the second part is proved in much the same way as the analogous theorem was proved in the case of the fundamental group and is omitted. An important corollary of the above theorem is Corollary 2.4. If f : X → Y is a homeomorphism then f# : πn (X, p) → π ...
... The first part of the theorem is obvious while the second part is proved in much the same way as the analogous theorem was proved in the case of the fundamental group and is omitted. An important corollary of the above theorem is Corollary 2.4. If f : X → Y is a homeomorphism then f# : πn (X, p) → π ...
Week 5: Operads and iterated loop spaces October 25, 2015
... The operadic point of view underscores a general philosophy in “homotopy coherent mathematics:" equalities between operations often must be replaced by homotopies. However, homotopies themselves are usually too unstructured a notion to be of much use. If, however, those homotopies are encoded as pa ...
... The operadic point of view underscores a general philosophy in “homotopy coherent mathematics:" equalities between operations often must be replaced by homotopies. However, homotopies themselves are usually too unstructured a notion to be of much use. If, however, those homotopies are encoded as pa ...
Midterm 1 solutions
... Let φ : X → Y be a continuous map. Another continuous map ψ : Y → X is called homotopy inverse for φ if ψ ◦ φ ' IdX and φ ◦ ψ ' IdY . If there exists a homotopy inverse for φ, then φ is called homotopy equivalence. In that case, we say that X is homotopy equivalent to Y (or X has the same homotopy t ...
... Let φ : X → Y be a continuous map. Another continuous map ψ : Y → X is called homotopy inverse for φ if ψ ◦ φ ' IdX and φ ◦ ψ ' IdY . If there exists a homotopy inverse for φ, then φ is called homotopy equivalence. In that case, we say that X is homotopy equivalent to Y (or X has the same homotopy t ...
An introduction to equivariant homotopy theory Groups Consider
... An algebraic model, but not useful for calculations. Conjecture.(Greenlees) For any compact Lie group G there is an abelian category A(G) such that Q - G-spectra ' d. g. (A(G)) where A(G) has injective dimension equal to the rank of G. ...
... An algebraic model, but not useful for calculations. Conjecture.(Greenlees) For any compact Lie group G there is an abelian category A(G) such that Q - G-spectra ' d. g. (A(G)) where A(G) has injective dimension equal to the rank of G. ...
k h b c b a q c p e a d r e m d f g n p r l m k g l q h n f
... homotopic to IdX and IdY , respectively. S 2 minus n points is homeomorphic to R2 minus n − 1 points, which deformation retracts onto a wedge of n − 1 copies of S 1 . The fundamental group of the Möbius band is Z, while that of the projective plane is Z/2. The two spaces are therefore not homotopy ...
... homotopic to IdX and IdY , respectively. S 2 minus n points is homeomorphic to R2 minus n − 1 points, which deformation retracts onto a wedge of n − 1 copies of S 1 . The fundamental group of the Möbius band is Z, while that of the projective plane is Z/2. The two spaces are therefore not homotopy ...
Lecture XI - Homotopies of maps. Deformation retracts.
... 1. Check that the map φ constructed in the proof of theorem 11.3 is continuous and is indeed a homotopy. Work out the proof of theorem 11.5. 2. Show that the boundary ∂M of the Möbius band M is not a deformation retract of M by taking a base point x0 on the boundary and computing explicitly the gro ...
... 1. Check that the map φ constructed in the proof of theorem 11.3 is continuous and is indeed a homotopy. Work out the proof of theorem 11.5. 2. Show that the boundary ∂M of the Möbius band M is not a deformation retract of M by taking a base point x0 on the boundary and computing explicitly the gro ...
Math 8301, Manifolds and Topology Homework 7
... 4. Suppose X is a topological space and φ : S n−1 → X is a continuous function, where n ≥ 1. Let Y = X ∪φ en be the space obtained from the disjoint union Dn ∪ X by identifying any point v ∈ S n−1 ⊂ Dn with its image φ(v) ∈ X. We say that Y is obtained from X by attaching an n-cell. Use the Seifert- ...
... 4. Suppose X is a topological space and φ : S n−1 → X is a continuous function, where n ≥ 1. Let Y = X ∪φ en be the space obtained from the disjoint union Dn ∪ X by identifying any point v ∈ S n−1 ⊂ Dn with its image φ(v) ∈ X. We say that Y is obtained from X by attaching an n-cell. Use the Seifert- ...
Homotopy groups of spheres
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.The n-dimensional unit sphere — called the n-sphere for brevity, and denoted as Sn — generalizes the familiar circle (S1) and the ordinary sphere (S2). The n-sphere may be defined geometrically as the set of points in a Euclidean space of dimension n + 1 located at a unit distance from the origin. The i-th homotopy group πi(Sn) summarizes the different ways in which the i-dimensional sphere Si can be mapped continuously into the n-dimensional sphere Sn. This summary does not distinguish between two mappings if one can be continuously deformed to the other; thus, only equivalence classes of mappings are summarized. An ""addition"" operation defined on these equivalence classes makes the set of equivalence classes into an abelian group.The problem of determining πi(Sn) falls into three regimes, depending on whether i is less than, equal to, or greater than n. For 0 < i < n, any mapping from Si to Sn is homotopic (i.e., continuously deformable) to a constant mapping, i.e., a mapping that maps all of Si to a single point of Sn. When i = n, every map from Sn to itself has a degree that measures how many times the sphere is wrapped around itself. This degree identifies πn(Sn) with the group of integers under addition. For example, every point on a circle can be mapped continuously onto a point of another circle; as the first point is moved around the first circle, the second point may cycle several times around the second circle, depending on the particular mapping. However, the most interesting and surprising results occur when i > n. The first such surprise was the discovery of a mapping called the Hopf fibration, which wraps the 3-sphere S3 around the usual sphere S2 in a non-trivial fashion, and so is not equivalent to a one-point mapping.The question of computing the homotopy group πn+k(Sn) for positive k turned out to be a central question in algebraic topology that has contributed to development of many of its fundamental techniques and has served as a stimulating focus of research. One of the main discoveries is that the homotopy groups πn+k(Sn) are independent of n for n ≥ k + 2. These are called the stable homotopy groups of spheres and have been computed for values of k up to 64. The stable homotopy groups form the coefficient ring of an extraordinary cohomology theory, called stable cohomotopy theory. The unstable homotopy groups (for n < k + 2) are more erratic; nevertheless, they have been tabulated for k < 20. Most modern computations use spectral sequences, a technique first applied to homotopy groups of spheres by Jean-Pierre Serre. Several important patterns have been established, yet much remains unknown and unexplained.