bio  website  math.lsa.umich.edu/~speyer 

location  Ann Arbor  
age  33  
visits  member for  4 years, 6 months 
seen  2 hours ago  
stats  profile views  27,345 
Associate Professor of Mathematics at the University of Michigan. My research interests are in combinatorial algebraic geometry, particularly Schubert calculus, matroids and cluster algebras. I also enjoy thinking about number theory and computational mathematics.
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Holomorphic trivialization of $(x,y) \subset \mathbb{C}[x,y]/(y^2  x^3 + x)$
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Holomorphic trivialization of $(x,y) \subset \mathbb{C}[x,y]/(y^2  x^3 + x)$
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Holomorphic trivialization of $(x,y) \subset \mathbb{C}[x,y]/(y^2  x^3 + x)$
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answered  Holomorphic trivialization of $(x,y) \subset \mathbb{C}[x,y]/(y^2  x^3 + x)$ 
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awarded  Nice Answer 
Apr 13 
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Geometric explanation of Hutton's formula?
You're welcome! Sorry for the missing scalar factors in the first version; added now. 
Apr 13 
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Geometric explanation of Hutton's formula?
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Apr 13 
answered  Geometric explanation of Hutton's formula? 
Apr 12 
awarded  Enlightened 
Apr 12 
awarded  Nice Answer 
Apr 9 
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Cyclic extensions
You may be looking for Kummer's theorem: If $n$ is relatively prime to the characteristic of $K$, and $x^n1$ splits in $K$, THEN every degree $n$ cyclic extension of $K$ is of the form $L=K(a)$ with $a^n \in K$. The answers below indicate why each hypothesis is needed. 
Apr 9 
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How to check whether a matrix is completely positive or not?
I suspect the closers misread this question as the far easier one abx understood; I'm voting to reopen. 
Apr 9 
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How to check whether a matrix is completely positive or not?
@abx The $x_i$ are required to be $\geq 0$; this is more restrictive than being positive definite. (I was confused by this for quite a while as well.) 
Apr 8 
revised 
How to flow submanifolds?
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Apr 8 
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How to flow submanifolds?
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Apr 8 
answered  How to flow submanifolds? 
Apr 8 
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What is the Tutte polynomial encoding?
We don't know the dimension of the vector space in $K_0$ spanned by all matroids, although we do know from DerksenFink that it is spanned by Schubert matroids. Alex and I did some preliminary work investigating positivity properties of this $K$class, but nothing we are willing to state publicly yet. 
Apr 8 
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What is the Tutte polynomial encoding?
@მამუკაჯიბლაძე Thanks! Not much more progress beyond what's in our paper, no. (There are results in the paper which are not in this answer.) For the study of the invariant in $K_0(G(d,n))$, the starting point is DerksenFink arxiv.org/abs/0908.2988 , which works out the vector space of matroids modulo "obvious $K$theory relations". This has dimension $\binom{n}{d}$ and has basis the Schubert matroids. Since $\binom{n}{d} = \dim K_0(G(d,n))$, I had hoped the obvious relations were all of them, but they are not, because the fact that $\dim Z \leq n1$ also gives relations. (continued) 
Apr 6 
answered  Convergence of the Double Integral of a Polynomial Reciprocal 
Apr 6 
answered  How to recognize a Hopf algebra? 