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May
20
awarded  Notable Question
Apr
28
awarded  Revival
Feb
25
awarded  Taxonomist
Feb
25
accepted Optimal elevator placement
Feb
9
answered What kind of algorithm might solve this type of optimization problem?
Feb
5
accepted How many directed graphs of size n are there where each vertex is the tail of exactly one edge?
Feb
5
answered Finding the minimal polynomial from characteristic equation
Feb
5
answered First examples for topology of non-Hausdorff spaces
Feb
5
answered Determine the boundedness of a complex function
Feb
5
comment Proving Boundedness
Thanks; you're right on both accounts!
Feb
5
answered Proving Boundedness
Feb
5
answered Multiplying two matrices that are the same size?
Feb
4
revised Proving the Fibonacci identity $\sum_{i=1}^n f_i^2=f_nf_{n+1}$ by induction
added 176 characters in body
Feb
4
comment Rational number in $\mathbb{Z}[\omega]$ should be integer.
@brick By definition, algebraic integers are solutions of monic polynomials. Gauss's lemma says that if a monic polynomial factors over Q, it factors over Z.
Feb
4
answered Proving the Fibonacci identity $\sum_{i=1}^n f_i^2=f_nf_{n+1}$ by induction
Feb
4
answered Permutation isomorphic subgroups of $S_n$ are conjugate
Feb
4
answered Proving $\mathrm{SL}_2(\mathbb{R})\trianglelefteq\mathrm{GL}_2(\mathbb{R})$
Feb
4
answered Rational number in $\mathbb{Z}[\omega]$ should be integer.
Feb
4
comment why are CAT(0) spaces contractible?
@mathreader Take two points and look at the distance between them. The geodesics from the origin to those points form two edges of a triangle, with the line between them being the third. As both geodesics are retracted evenly, the CAT(0) property should ensure the distance between them decreases. This would make the map Lipschitz, and thus continuous.
Feb
4
comment why are CAT(0) spaces contractible?
Spheres do not have unique geodesics. Antipodal points have infinitely many geodesics connecting them.