I am currently an postdoctoral fellow at the Max Planck Institute for Mathematics in Bonn. For the academic year 2014-5, I was here as an NSF postdoctoral fellow, sponsored by Peter Teichner. From fall 2012 to spring 2014, I was a postdoc at UC Berkeley, sponsored by Kolya Reshetikhin.

My research revolves around quantum field theory, focusing both on applications of homotopical ideas to QFT itself and applications of QFT to geometry and representation theory. My books and papers are described below.

- Inspired by the work of Beilinson-Drinfeld and Francis-Gaitsgory-Lurie on
*factorization algebras*, Kevin Costello and I have developed a version of factorization algebras appropriate to perturbative QFT, building upon Costello's earlier work developing a renormalization machine. We have proved a kind of deformation quantization theorem for field theory, as well as a factorization refinement of the Noether theorem. We develop these ideas in a two-volume book ``Factorization Algebras in Quantum Field Theory'' to be published by Cambridge University Press, with the first volume available in December 2016. The first volume introduces factorization algebras and develops examples, primarily from free field theories. (This is not as boring as it might sound: we recover vertex algebras in complex dimension 1 and a quantum group for abelian Chern-Simons theory in dimension 3.) The second volume develops interacting classical and quantum field theory using the Batalin-Vilkovisky formalism and proves the deformation quantization and Noether theorems. (We are editing it for publication in 2017.) - My thesis shows how these ideas work in several simple contexts. The thesis has a few distinct pieces. First, I provide an expository introduction to the Batalin-Vilkovisky formalism. Second, I prove that the BV formalism provides a determinantal functor on perfect complexes. Third, I show by example how our factorization algebra procedure recovers vertex algebras, notably free bosons, free fermions, and affine Kac-Moody vertex algebras. Finally, I prove an index theorem based on our techniques. Some of my recent work is about extending and enhancing these results.
- In Chiral differential operators via Batalin-Vilkovisky quantization, written with Vassily Gorbounov and Brian Williams, we construct the curved βγ system using a combination of the BV formalism and Gelfand-Kazhdan formal geometry, modified to work with factorization algebras. We then show that the associated vertex algebra is the chiral differential operators. Our methods use BV techniques to realize mathematically the physical arguments given by Witten and Nekrasov recovering CDOs from the βγ system.
- With Rune Haugseng, we carefully study linear BV quantization and formulate it as a functor of infinity-categories and then as a map of derived stacks in the imaginatively-named Linear BV quantization as a functor of infinity-categories.
- With Ryan Grady, I have pursued several projects touching on derived geometry and QFT. In One-dimensional Chern-Simons Theory and the A-hat genus, we constructed a one-dimensional TFT whose partition function recovers the A-hat genus of a manifold. In L-infinity spaces and derived loop spaces, we clarified and further developed Costello's approach to derived geometry via L-infinity spaces. Finally, in Lie algebroids as L-infinity spaces, we showed that Lie algebroids (and associated constructions like representations up to homotopy) fit naturally into this version of derived geometry.
- With Dmitri Pavlov, I recently reexamined filtered derived categories from the perspective of model categories and infinity-categories, with an eye towards future work on D-modules and factorization algebras, in Enhancing the filtered derived category.

There are several other projects at various stages of development. If you'd like to know more, feel free to contact me.

- With Theo Johnson-Freyd, I wrote an expository introduction to the BV formalism, emphasizing how one would rediscover Feynman diagrams for purely homological reasons.
- Based on a lecture by Costello, I wrote up an explanation for how the βγ system arises from the usual two-dimensional sigma model. To be more precise, after rewriting the sigma model in the first-order formalism, one can look at scaling the metric on the target to infinity and then take the chiral sector.
- For the seminar on topological insulators, I made slides introducing some basic, relevant ideas for a mathematical audience. It might be helpful to others wanting to see a quick overview, but beware that in this seminar I was the blind leading the blind.

With Claudia Scheimbauer, I recently taught a course on derived deformation theory and Koszul duality at the University of Bonn. Here is our website.

In spring 2013 (in Berkeley) and in fall 2014 (at MPIM), Peter Teichner and I organized seminars on factorization algebras and BV quantization. (Notes from the first seminar can be found here and the plan of the second seminar can be found here.) In fall 2015 I organized a seminar on topological insulators with Alessandro Valentino.

I've also been lucky to be an organizer of several conferences in the last two years (at the Simons Center, Banff, IBS-CGP, and Oberwolfach). I'm taking a break from that for a while.

People: DA DBE JB DC KC W(B)D PE DF JF DG EG GG RG TJF MK JL SL DN DP A(T)P N(K)R NR SS US CT HT PT