# Feynman Graphs and Motives

Wednesday, March 20th, 2013 | Author:

Being on a school about Feynman graphs and Motives, I just learned how these are related. It's a cute story! Actually, you don't need any physics to appreciate it, though physics might let you appreciate it even more.

A Feynman graph is just a (non-directed) graph with a finite number of vertices and a finite number of edges. Physicists are interested in computing certain integrals defined in terms of Feynman graphs, which they call amplitudes.

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# Beautiful New Fonts

Wednesday, March 06th, 2013 | Author:

In this short rant, I want to convince you to try out some new beautiful fonts for your editor, terminal, wiki or website. In particular, I want you to take a look at Adobe's Source Pro Fonts. I'll explain where you can preview fonts online and how to employ them in various settings.

Category: English, Not Mathematics | Comments off

# From the Backlog 2010

Thursday, February 21st, 2013 | Author:

I have to admit that I try to read more than I actually do, in particular blog posts. In this post I give you some links from 2010 that I now read skimmed a few weeks ago and found to be fresh enough to be shared again.

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# Motives of Projective Bundles

Friday, December 14th, 2012 | Author:

Given a vector bundle E-->X of rank r+1 one can take the projective space of lines in each fiber, which results in a projective bundle P(E)-->X. A projective bundle formula for a functor F from spaces to rings tells us that F(P(E)) is a free F(X)-module of rank r.

In this post I look at some computations around projective bundle formulae for the Chow ring, the algebraic K-Theory and the (Chow) motive of some spaces, in particular flag varieties. We recover some results from the previous posts on cohomology, cycles & bundles and motive of projective space.

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# Invariants of projective space III: Motives

Monday, December 10th, 2012 | Author:

I want to explain a particularly easy example of a motivic cellular decomposition: That of $n$-dimensional projective space. The discussion started with cohomology (part 1), continued with bundles and cycles (part 2) and in this part 3, we discuss motivic stuff.

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# Invariants of projective space II: Cycles and Bundles

Thursday, December 06th, 2012 | Author:

I want to explain a particularly easy example of a motivic cellular decomposition: That of $n$-dimensional projective space. The discussion started with cohomology (part 1) and in this part 2, we discuss intersection-theoretic and bundle-theoretic invariants. In part 3 we will see the motivic stuff.

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