Jacques Distler

I will report on some work in progress with Dan Freed and Greg Moore. In an orientifold background, D-brane charge takes values in a certain twisted version of KR Theory. Moreover, there is a nontrivial background charge (\'tadpole\'). Up \'til now, this background charge has only been calculated rationally -- i.e., ignoring torsion. We derive a formula for it, over the integers. Only after \'inverting 2\', does the charge localize to the fixed point sets of the orientifold action, and we can give a compact formula for it.

In the 1990s, the eprint arXivs fundamentally reshaped scientific communication in Math and Physics. In this decade, blogs, wikis and other, similar, tools are mediating an equally profound reshaping of scientific communication. I will talk about my own experience, as a blogger, software designer, and physicist, pointing to some of the successes and some of the challenges ahead.