MathOverflow Weekly Newsletter
MathOverflow Weekly Newsletter

Top new questions this week:

What is a foliation and why should I care?

The title says everything but while it is a little bit provocative let me elaborate a bit about my question. First time when I met the foliation it was just an isolated example in the differential ...

dg.differential-geometry oa.operator-algebras differential-topology noncommutative-geometry foliations  
asked by truebaran 26 votes
answered by Pablo Lessa 41 votes

What is the "real" meaning of the $\hat A$ class (or the Todd class)?

In the Atiyah-Singer index theorem as well as in the Grothendieck-Riemann-Roch theorem, one encounters either the $\hat A$-class or the Todd class, depending on the context. I want to focus on the ...

at.algebraic-topology characteristic-classes index-theory  
asked by Sebastian Goette 23 votes

What (fun) results in graph theory should undergraduates learn?

I have the task of creating a 3rd year undergraduate course in graph theory (in the UK). Essentially the students will have seen minimal discrete math/combinatorics before this course. Since graph ...

graph-theory teaching  
asked by user62562 22 votes
answered by David Eppstein 10 votes

Is the Flajolet-Martin constant irrational? Is it transcendental?

Facebook has a new tool to estimate the average path length between you and any other person on Facebook. An interesting aspect of their method is the use of the Flajolet-Martin algorithm. In the ...

nt.number-theory transcend.-number-theory irrational-numbers  
asked by Jeffrey Shallit 19 votes

How big are the prime factors of $2^kp - 1$?

I have already asked this question here. No answers despite the bounty (which has now ended) Let $p$ be a prime number, $p > 3$. Does there always exist $k \in \mathbb N_{\ge 1}$ such that the ...

nt.number-theory prime-numbers  
asked by Ant 17 votes
answered by Gerhard Paseman 1 vote

Why should intersection cohomology and quantum cohomology be related for a symplectic resolution?

In http://arxiv.org/pdf/1410.6240.pdf M. McBreen and N. Proudfoot conjectured a precise relationship between the quantum cohomology of a symplectic resolution and the intersection cohomology of the ...

ag.algebraic-geometry geometric-rep-theory intersection-cohomology quantum-cohomology symplectic-resolution  
asked by Yellow Pig 14 votes
answered by Michael McBreen 7 votes

Algebraic spaces as locally ringed spaces

Let $S$ be a scheme (although I am more than happy to have $S=\text{Spec}(k)$ for a field $k$) and $\mathsf{AlgSp}/S$ the category of algebraic spaces over $S$. Does there exist an embedding ...

ag.algebraic-geometry stacks  
asked by Alex Youcis 14 votes
answered by nfdc23 15 votes

Greatest hits from previous weeks:

Suggestions for a good Measure Theory book

I have taken analysis and have looked at different measures, but I am currently looking at realizing a certain problem in a different light and feel that I need a better background in various measures ...

measure-theory books reference-request big-list textbook-recommendation  
asked by Andrew 20 votes
answered by efq 13 votes

why study Lie algebras?

I don't mean to be rude asking this question, I know that the theory of Lie groups and Lie algebras is a very deep one, very aesthetic and that has broad applications in various areas of mathematics ...

dg.differential-geometry lie-groups lie-algebras differential-equations  
asked by Olivier Bégassat 69 votes
answered by Deane Yang 83 votes

Can you answer these?

Can approximately periodic functions be perturbed to periodic functions on a locally compact group?

Let $G$ be a locally compact group and $H\subset G$ a closed and cocompact subgroup. I wish to consider bounded continuous functions from $G$ to $\mathbb{C}$ that are periodic in the following strong ...

fa.functional-analysis gn.general-topology c-star-algebras topological-groups  
asked by Gabor Szabo 3 votes

The non-abelian Gauss-Manin connection; non-abelian M_dR; a Grothendieck lemma for cyrstals

I'm interested in understanding the non-abelian Gauss-Manin connection on Carlos Simpson's relative de Rham Moduli space $M_{dR}(X/S,n)$ for a smooth projective morphism of schemes $X/S$. The scheme ...

ag.algebraic-geometry nt.number-theory nonabelian-cohomology  
asked by Max Menzies 7 votes

Have Grothendieck's notes in Montpellier already been investigated?

Grothendieck, who passed away on November 13, 2014, left a huge amount (around 20.000 sheets) of personal notes in the University of Montpellier that he thought he was the only one to be able to ...

soft-question ho.history-overview  
asked by Sylvain JULIEN 10 votes
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