### Talk: Orientifold and Twisted KR Theory

I’ve alluded, before, to a seemingly interminable project I’ve been working on with Dan Freed and Greg Moore. The (original) modest goal of the project was to write down a formula for the tadpole in an orientifold background, not just rationally (as has been done before), but over the integers (i.e., including torsion).

Since the project seems to be dragging on (shifting goalposts 'n all), and since, periodically, I get asked about our result, I thought I’d provide a link to a conference talk I gave recently, on the subject. Since the talks for the conference are online, you probably *could* have found this lecture with a little help from Google, anyway. But here’s the direct link. (As always, you need a MathML-capable browser. And, yes, this is the boring default theme.)

## Re: Talk: Orientifold and Twisted KR Theory

Question:

Are twists and helices intimately related?

I recently found this engineering paper:

Hamish Mielke [MS EE, radar consultant], ‘A New twist to Fourier Transformations’.

He discusses helical functions which appear to be 3D versions of 2D elliptical functions.

Maple even has a product line devoted to this paper.

Being curious, I also found this ME paper A Mahalov [Cornell], et al, ‘Invariant helical subspaces for the Navier-Stokes equations’.

Various twistor theories in physics often use the term maximal helical violation [MHV].

Are engineers, since CP Steinmetz in the 1890s, more advanced than physicists in their use of representations, particularly with the information provided by helical equations?