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Jim Conant's user avatar
Jim Conant's user avatar
Jim Conant's user avatar
Jim Conant
  • Member for 14 years, 3 months
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What is a continuous path?
Plaut and Berestovskii have written some papers that might be of interest. They are not exactly the same thing. They talk about $\epsilon$-chains and homotopy of $\epsilon$-chains, where an $\epsilon$-chain is a sequence of points where each point is within $\epsilon$ of the previous. They have some interesting results.
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In what ways did Leibniz's philosophy foresee modern mathematics?
I can't resist mentioning Neal Stephenson's series of novels "The Baroque Cycle," for an interesting take on both Newton and Leibniz. en.wikipedia.org/wiki/The_Baroque_Cycle
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What could be some potentially useful mathematical databases?
I'd also like to see a database of group cohomology computations for things like the mapping class group and other important groups.
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Locally flat submanifold
Another example: Take a knot $K$ in $S^3$ and consider the cone on the knot in $B^4$. This is a submanifold of $B^4$ homeomorphic to a disk, but it is not flat at the cone point.
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What are the worst notations, in your opinion?
$\mathbb Z/p$ is the worst of both worlds, in that it makes no sense.
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Kontsevich Integral without associators?
This seems highly unlikely to me. My approach to rule it out would be to look at simple knot and link diagrams to constrain what the chord-diagram valued R-matrix could possibly be.
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generators of Out(F_n) and homology
added 43 characters in body; added 42 characters in body
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generators of Out(F_n) and homology
And I should have mentioned $n>2$.
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generators of Out(F_n) and homology
It follows directly from the Nielsen presentation for $Out(F_n)$. Vogtmann has a survey, "Automorphisms of free groups and outer space," which covers this point.
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generators of Out(F_n) and homology
The abelianization is almost trivial: it's $\mathbb Z_2$.
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3D surfaces of infinite genus
By the way, there are uncountably many different embeddings of infinite genus surfaces in $\mathbb R^3$. Take a long tube, and put a line of tubes tied in knots along this tube. Letting these knots vary gives an uncountable family of surfaces,
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3D surfaces of infinite genus
You might find Benoit Kloeckner's answer at mathoverflow.net/questions/4155/… illuminating, which gives a classification of all non-compact surfaces.
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Schur-Weyl duality
I suppose you know that $S_\lambda(V)=F_\lambda\otimes_{S_k} V^{\otimes k}$, where $F_\lambda$ is the $\lambda$-irrep of the symmetric group $S_k$.
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"homotopy sphere" assumption in Poincare Conjecture
Yes, in dimension three a closed simply connected 3-manifold is a homotopy sphere. This comes from Poincare duality.
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