Tag Archives: coarse geometry

The real form of the coarse Baum-Connes conjecture

Following up on my post a few days back about Dranishnikov’s talk… After the talk, Sasha asked me if I knew a reference where some “standard” facts about the real version of the coarse Baum-Connes conjecture were stated (as, for example, that the real coarse index of the Dirac operator vanishes for positive scalar curvature manifolds, or that the complex form of the coarse Baum-Connes conjecture implies the real form.

I was sure that these “well known to experts” results must be written down somewhere. Maybe they are, but I couldn’t find a clean reference.  So I thought it might be helpful to put together a little note summarizing some of these standard facts.  I’ve now posted this on the arXiv and it is available here.  If you need the real version of CBC for something, this might be useful.

Originally, Nigel and I were going to cover the real version of everything in Analytic K-Homology.  But at some point we got fed up with Clifford algebras and retreated to the complex world.  I think that was the only way to get the book finished, but it has left a few loose ends!

Imported “Interesting Mathematics”

For a few years I ran a blog over at blogspot.com called “Interesting Mathematics”, the URL being coarsemath.blogspot.com. It went quiet in 2010, which was a high-stress year for me, and never really got started again.

So, I succeeded (just now) in figuring out how to import all the old posts from “Interesting Mathematics” onto this blog. Of course that gives me an incentive to continue blogging about mathematics here.

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Coarse Math at MSRI!

Forwarded from Vincent Lafforgue

From August 15, 2011 to December 16, 2011, MSRI (Berkeley) hosts a program on Quantitative Geometry. It is organized by Keith Ball, Emmanuel Breuillard, Jeff Cheeger, Marianna Csornyei, Mikhail Gromov, Bruce Kleiner, Vincent Lafforgue, Manor Mendel, Assaf Naor (main organizer), Yuval Peres, and Terence Tao. This is a big program with many available positions.

Examples of areas that will be covered by the program are: geometric group theory, the theory of Lipschitz functions (e.g., Lipschitz extension problems and structural aspects such as quantitative differentiation), large scale and coarse geometry, embeddings of metric spaces and their applications to algorithm design, geometric aspects of harmonic analysis and probability, quantitative aspects of linear and non-linear Banach space theory, quantitative aspects of geometric measure theory and isoperimetry, and metric invariants arising from embedding theory and Riemannian geometry. Go to http://tinyurl.com/28x94y6 for more details.

The deadline for applications is
-October 1, 2010 for Research Professors
-December 1, 2010 for Research Members and Postdoctoral Fellows.
Look at
http://www.msri.org/propapps/applications/application_material
for more details.

Permanence properties in coarse geometry

I hate to think how long it has been since I last posted here. My apologies – it has been a difficult summer for various non-mathematical reasons. Anyhow, trying to get back on track let me mention a survey article that Erik Guentner sent me called “Permanence properties in coarse geometry”. What Erik means by “permanence properties” is statements like “the property of having finite asymptotic dimension is closed under group extensions”. Many statements of this kind, for a variety of coarse properties (asymptotic dimension, embeddability in Hilbert space, property A/exactness, etc) have by now been proved and this is a very nice survey bringing together general techniques for obtaining such results with specific applications.

JohnR

Metric spaces with dilations, and metric trees

Here is a gentle introduction to the theory of metric spaces with dilations (“rescaling maps”, so that one can define an appropriate notion of tangent space.) This appears on the arXiv today.

http://arxiv.org/abs/1007.2362

Also a couple of elegant-looking papers on metric trees and their embeddings into Banach spaces

http://arxiv.org/abs/1007.2207

http://arxiv.org/abs/1007.2208

Lots of interesting stuff on the arXiv today. I probably won’t be posting much for a few weeks as I have some personal business to take care of.