Category Archives: Mathematics

H_2(Gamma_N(p),Z)

Posted on January 30, 2015 by Persiflage

In this post (which is a follow-up to the last post), I wanted to compute the group \( H_2(\Gamma_N(p),\mathbf{Z})\), where \( \Gamma_N(p)\) is the congruence subgroup of \( \mathrm{SL}_N(\mathbf{Z})\) for large enough \( N\) and \( p\) is prime. In … Continue reading →

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Stable completed homology without Quillen-Lichtenbaum

Posted on January 21, 2015 by Persiflage

Having just made (hopefully) the final revisions on my paper on stable completed cohomology groups, I wanted to record here a few remarks which didn’t otherwise make it into the paper. The first is that, in addition to the result … Continue reading →

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Inverse Galois Problems II

Posted on January 13, 2015 by Persiflage

David Zywina was in town today to talk about a follow up to his previous results mentioned previously on this blog. This time, he talked about his construction of Galois groups which were simple of orthogonal type, in particular, the … Continue reading →

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Abelian Spiders

Posted on January 11, 2015 by Persiflage

This is a blog post about the thesis of my student Zoey Guo, who is graduating this year. (For a blog post on the thesis of my other student graduating this year, see this.) Let \(\Phi\) be a finite graph. … Continue reading →

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Higher direct images of canonical extensions

Posted on January 4, 2015 by Persiflage

I like Kai-Wen’s talks; he gives lots of examples, writes big with big chalk, and clearly explains the key points of the argument. I’m not sure I would classify his thesis as light reading material, but if he produced a … Continue reading →

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Derived Langlands

Posted on December 22, 2014 by Persiflage

Although it has been in the air for some time, it seems as though ideas from derived algebraic geometry have begun to inform developments in the Langlands program. (A necessary qualifier: I am talking about reciprocity in the classical arithmetic … Continue reading →

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Harris 60

Posted on December 15, 2014 by Persiflage

I’ve just returned from the excellent MSRI workshop which honored Michael Harris’ 60th birthday, and here is a brief summary of some of the gossip and mathematics I picked up when I was there. First, let me take note of … Continue reading →

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The Modular Forms Database is Annoying

Posted on November 23, 2014 by Persiflage

It used to be the case, 10 or so years ago, that William Stein maintained a website with extensive tables of \(q\)-expansions of modular forms, computed using magma. However, as the edifice of civilization begins to crumble, this website no … Continue reading →

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Mysterious Formulae

Posted on November 15, 2014 by Persiflage

I’m not one of those mathematicians who is in love with abstraction for its own sake (not that there’s anything wrong with that). I can still be seduced by an explicit example, or even — quell horreur — a definite … Continue reading →

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In Brief

Posted on October 21, 2014 by Persiflage

The start of the academic year has a habit of bringing forth distractions, not least of all to someone as disorganized as me. So here are a few remarks in brief. The class number of \(\mathbf{Q}(\zeta_{151})^{+}\) is one. John Miller, … Continue reading →

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