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

location  Ann Arbor  
age  33  
visits  member for  4 years, 9 months 
seen  2 days ago  
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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.
1d

awarded  Nice Answer 
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awarded  Enlightened 
2d

awarded  Nice Answer 
Jul 22 
revised 
Constructing quintic number fields with certain splitting behaviour
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Jul 22 
comment 
Computing the Chern class of $S^6$
Does the following count: "$c_{top}(E)$ is the number of zeroes of a section of the vector bundle $E$ (counted with appropriate multiplicity). When $E$ is the tangent bundle, and your base space is a smooth compact manifold $X$, then the number of zeroes is the Euler characteristic $\chi(X)$. This is the PoincareHopf theorem and is deducible from the Lefschetz fixed point theorem mathoverflow.net/questions/153289 or Morse theory." To me, this is just describing some ways to think about Euler class without using that word, but maybe you disagree. 
Jul 22 
comment 
Constructing quintic number fields with certain splitting behaviour
I have now edited in Don's point. 
Jul 22 
revised 
Constructing quintic number fields with certain splitting behaviour
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Jul 22 
comment 
Constructing quintic number fields with certain splitting behaviour
@socalledfriendDon Excellent point! You are right! Strange that Bhargava doesn't point that out; this argument shows that Bhargava's formula is always an upper bound. 
Jul 22 
answered  Constructing quintic number fields with certain splitting behaviour 
Jul 22 
awarded  Good Question 
Jul 22 
answered  Constructing quintic number fields with certain splitting behaviour 
Jul 21 
comment 
Constructing quintic number fields with certain splitting behaviour
Agreed. I was confused by Bhargava talking about $K$ etale over $\mathbb{Q}_p$. I thought he was abusing language and meant $\mathcal{O}_K$ etale over $\mathbb{Z}_p$ (at which point, other things didn't make sense) but the statement is perfectly sensible taken literally, and then Jeremy Rouse is right that this isn't enough. 
Jul 21 
revised 
Nonvanishing of elements in cohomology of full Flag varieties
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Jul 21 
answered  Nonvanishing of elements in cohomology of full Flag varieties 
Jul 21 
comment 
Constructing quintic number fields with certain splitting behaviour
I haven't digested Bhargava's terminology well enough to tell, but does Theorem 1.3 in arxiv.org/abs/1402.0031 do the job? 
Jul 21 
answered  Isomorphism of matrix ring over ore domain 
Jul 21 
comment 
Constructing quintic number fields with certain splitting behaviour
I don't follow why square free implies (3). If $p$ factors as $\mathfrak{p}^2 \mathfrak{q}$, where $\mathcal{O}_K/\mathfrak{q} \cong \mathbb{F}_{p^3}$, I think the discriminant is squarefree. That said, you might want to look at Kedlaya arxiv.org/abs/1103.5728 for some statements about sieving for square free discriminant. 
Jul 18 
revised 
Second betti number of compact analytic spaces
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Jul 18 
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Second betti number of compact analytic spaces
Many thanks to Tara Holm for asking me a number of years ago how to get at the actual cohomology of a toric variety, and how it related to the FultonSturmfels computation. Of course, any errors introduced are mine. 
Jul 18 
answered  Second betti number of compact analytic spaces 