# qwerty1793

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 Nov7 awarded Popular Question Oct3 awarded Caucus Aug31 revised Is the normalised Kauffman bracket more powerful than the Kauffman bracket? title clearer Aug31 asked Is the normalised Kauffman bracket more powerful than the Kauffman bracket? Apr25 awarded Nice Question Feb28 comment Knot database including text names Thanks for the suggestion. Just to let you know you can actually skip the volume filtering, Dr. Weeks built it directly into the snappea kernel! Line 90 of isometry.c defines "CRUDE_VOLUME_EPSILON" to be 0.01. Later, around line 140, when testing if two manifolds are isometric if they differ by more than this amount the entire calculation is aborted and the function returns "not isometric". Feb15 answered Interesting mathematical documentaries Jan10 awarded Yearling Oct15 accepted Manifolds with prescribed fundamental group and finitely many trivial homotopy groups Oct14 revised Manifolds with prescribed fundamental group and finitely many trivial homotopy groups added 25 characters in body Oct14 comment Manifolds with prescribed fundamental group and finitely many trivial homotopy groups Sorry, despite my efforts to make sure I wrote "finitely presented" I ended up writing finitely generated. I'll edit the question. Oct14 awarded Nice Question Oct12 asked Manifolds with prescribed fundamental group and finitely many trivial homotopy groups Sep28 comment Problems about the Estimate the Unknotting Number Yes, all knots have unknotting number less than $\lfloor n/2 \rfloor$. Suppose that making $k > \lfloor n/2 \rfloor$ crossing flips results in the unknot, then you can check that flipping all unflipped crossings instead also does. This clearly requires $\leq \lfloor n/2 \rfloor$ flips and so the unknotting number is at most $\lfloor n/2 \rfloor$. An equivalent bound also holds for unlinking links. Sep4 comment Determine if a matrix is unimodular In fact, thanks to LU decomposition, computing the determinant is at least as fast as computing a matrix product. So we can compute the determinant exactly in \$O(n^{2.376}). See en.wikipedia.org/wiki/LU_decomposition#Theoretical_complexity. Similarly, in Storjohann's paper "Near Optimal Algorithms for Computing Smith Normal Forms of Integer Matrices" he shows a similar inequality. That is, for an integer square matrix, computing its SNF is at least as fast as computing a matrix product. Sep3 revised Determine if a matrix is unimodular deleted 124 characters in body Sep3 comment Determine if a matrix is unimodular Sorry I misread the answers paper, their definition of unimodular used in Theorem 1 is more general to cover non-square matrices. I'll edit the question and remove the reference. Sep3 asked Determine if a matrix is unimodular Jun14 comment Generalising right-angled Artin groups Thanks, small type refers to the {2,3} case, correct? Is there a similar name for the {2,3,\infty} case? Jun14 accepted Generalising right-angled Artin groups