Subgroup Complexes
... The p-subgroups complex is really a geometry for G. Whatever one means by a geometry, there is usually a simplicial complex involved, it is associated to a prime p, and the stabilizers of simplices are treated as analogues of parabolic subgroups. One can take the view that the most canonically defin ...
... The p-subgroups complex is really a geometry for G. Whatever one means by a geometry, there is usually a simplicial complex involved, it is associated to a prime p, and the stabilizers of simplices are treated as analogues of parabolic subgroups. One can take the view that the most canonically defin ...
Cup products.
... 1. Show that if X is the union of contractible open subsets A and B, then all cup products of positive-dimensional classes in H ∗ (X) are zero. In particular, this is the case if X is a suspension. Conclude that spaces such as RP2 and T 2 cannot be written as unions of two open contractible subsets. ...
... 1. Show that if X is the union of contractible open subsets A and B, then all cup products of positive-dimensional classes in H ∗ (X) are zero. In particular, this is the case if X is a suspension. Conclude that spaces such as RP2 and T 2 cannot be written as unions of two open contractible subsets. ...
I.2 Topological Space, basis and subbasis
... 2. Let X be a set. Then T = P(X) is called the discrete topology and T = {∅, X} the indiscrete topology. 3. X = {a, b}. Then T = {∅, X, {a}} is a topology. 4. Let X be an infinite set. Then T = {U ⊂ X|U c is a f inite set} ∪ {∅} is called cofinite topology. Definition 2 Let X and Y be topological sp ...
... 2. Let X be a set. Then T = P(X) is called the discrete topology and T = {∅, X} the indiscrete topology. 3. X = {a, b}. Then T = {∅, X, {a}} is a topology. 4. Let X be an infinite set. Then T = {U ⊂ X|U c is a f inite set} ∪ {∅} is called cofinite topology. Definition 2 Let X and Y be topological sp ...