Dr. RobertRobert C. Helling

Rm 82, Research III, International Jacobs University Bremen, Campusring 1, D-28759 Bremen, Germany, Phone +49 421 200 3574, Fax +49 200 3229, Email helling@atdotde.de
I am a postdoc in the theoretical physics group at IUB. My research is in the area of superstring theory and its nonperturbative version, M-Theory.

Before joining IUB, I studied at Hamburg University and the Albert Einstein Institute in Potsdam under Hermann Nicolai. Later, I was a postdoc at Humboldt University Berlin and DAMTP Cambridge.

Me research includes the following areas:
  • In a certain sector, M-Theory is described by a quantum mechanical matrix model. Using perturbation theory one can compute scattering amplitudes and compare these to graviton scattering in supergravity. This is laid out in my PhD Thesis which summarises several papers. One of these studies rather general dynamics of moduli and has recently been of use in cosmological models. With Hermann Nicolai we wrote lecture notes on the M(atrix) model and supermembranes.
  • At small scales, one expects space-time manifold to resolve and to be replaced by a more general structure like non-commutative geometry. The non-commutative torus is a particularly simple example. Due to "Morita equivalence", it can have different descriptions that are physically equivalent. This we used to investigate continuity of scattering amplitudes on the parameter of noncommutativity, how a commutative theory can be dual to one with UV/IR-mixing and how to generalise SU(N) gauge theory to noncommutative spaces (seminar slides).
  • The most general solutions of branes are hard to find, but those that preserve some supersymmetry have a simpler description due to BPS equations. We used these to investigate brane splitting and joining transitions in the dual gauge theory (seminar slides). This has applications in the stringy Higgs mechanism, G2 manifolds and N=1 theories in general.
  • Besides string theory, people use "loop quantum gravity" to approach the quantisation of gravity. We worked out the similarities and differences of the two approaches in the solvable worldsheet theory of the bosonic string which is a non-trivial yet tractable diffeomorphism invariant theory (seminar slides). There is now a less technical write up containing a new calculation of the optical absorption spectrum of the polymer oscillator here.
  • Have you ever wondered if the universe really is the same in all directions? There are some rumors that the CMB shows that it is not quite. This is our contribution to this question. More specifically, we show how to use a bit of representation theory of SU(2) to easily compute "multipole vectors", a representation of the CMB which is rotationally covariant such that one can easily spot anisotropies.
  • As a summerstudent I joint the protein folding group at the NEC Research Institute in Princeton, NJ. There, we found an explanation why natural proteins have secondary structure: This makes them better designable! This paper was published in Science and has 200+ citations according to SSI.

I have written a less technical account on the M(atrix)-Modell of M-Theory (in German) and how physical space-time can be an emergent concept in string theory. The latter won me the Schlössmann Award. I maintain atdotde, a blog partially on physics, and I should better maintain my personal home-page. I am a co-moderator of the String Coffee Table. In the past, I gave physics lectures based on a Star Trek theme for high school students. "Phaser, Wurmloch, Warpantriebe" are the slides.

Other interests include scuba diving, jazz music (active and passive), and programming. Here are a number of projects:

  • LogVyper, a TeX-based divelog with web interface that reads out my Suunto Vyper dive computer (there is also an old version that connected to my Aladin).
  • A seminar scheduling system with automated seminar list, poster mailing and email reminders for the Albert Einstein Institute.
  • A set of dynamic web pages for staff lists, office allocation, guest house administration etc used at the AEI as well.
  • A toolbox to create online conference proceedings including semi-automated transparency scanning and audio.
  • An formula ascii pretty printer that can be plugged into emacs.
  • As many others, I have written a sudoku solver/generator.
  • My OpenPGP public key can be found here.