## February 21, 2008

### ERGE

The discussion engendered by my recent post on of the application of the Exact Renormalization Group to gravity, was rather illuminating. But I think I should return to a point emphasized in my first post on the subject, namely that the ERGE , at least when truncated (which is the only recourse for practical calculations), is not fully nonperturbative. Instead, it provides a (very useful) resummation of the loop expansion.

In this post, I will discuss three examples where, as far as I can tell, the ERGE fails to capture important physics, which just happens to be invisible to all orders in the loop expansion.

## February 4, 2008

### foreignObject

MathML has been broken on Mozilla trunk for nearly 14 months now. I used to like running nightly builds of Firefox or SeaMonkey. But, since November 2006, my browser use has been frozen in amber.

Over the past several months, Karl Tomlinson has been toiling away fixing MathML on Mozilla trunk. And his efforts are definitely coming together. There are still a couple of rather serious layout bugs, and at least one æsthetic issue. But, with the release of the STIX fonts (you can still get a copy of the beta here), and various other improvements to the browser, I’ve been itching to get my hands on a version that had passable MathML support. Despite the remaining bugs, Firefox is good enough to begin playing around with.

One of the things I wanted to try out was the new support for SVG `<foreignObject>`

, which, in particular, allows one to embed MathML fragments in SVG figures. In various posts of mine, I’ve been making occasional use of the converse ability, to embed SVG in MathML equations. But the n-Category Café guys would, I think, really profit from being able to create complicated commutative diagrams, *etc.*, in SVG.