spintwo.net jens boos | theoretical gravity & high energy physics


I am interested in modeling and constraining new physics at the intersection of high energy theory and gravity. Since Einstein gravity is perturbatively nonrenormalizable, putative ultraviolet completions of gravity may include new particles, new forms of geometry, or entirely new principles of physics that manifest themselves at short distances without spoiling desirable infrared properties. This can have implications both in pure gravity as well as in physics beyond the standard model, and it is my goal to understand the ramifications of such new physics for observable quantities.

Modified gravity theories

The formation of singularities inside of black holes is a robust prediction of General Relativity. At the same time, the existence of a spacetime singularity implies the end of predictability in any physical theory. For this reason I am interested in modifications of General Relativity that may solve the classical singularity problem.

Observational consequences of new physics

Sometimes we are lucky, and a very simple “new physics” model can make a striking prediction. For example, in the diagram above you see the dashed and dotted curves: these are the transmission coefficients for a particular scattering problem in ordinary quantum mechanics, plotted as a function of frequency ω. If one allows for physics to become nonlocal, however, this transmission coefficient drops to zero around a characteristic frequency (circled in red). This could mean that some sort of resonance effect occurs, and the scattering becomes completely reflective.

Black holes and compact gravitational objects

What happens when black holes or other compact gravitational objects interact with new physics? Above you can see a cosmic string (red) attached to a black hole (the black circle). Often, the new physics has a backreaction on the compact gravitational object; in this case, the cosmic string extracts rotational energy (green) from the central black hole. In my work I try to find such signatures of new physics in their interaction with gravitational objects.

Effects of Non-locality in Gravity and Quantum Theory

Book cover of “Effects of Non-locality in Gravity and Quantum Theory”

In my PhD thesis I investigate the role that locality plays in many areas of physics: gravity, quantum scattering, quantum field theoretical vacuum polarization, and Hawking radiation of black holes. In a second step, I ask what would happen if there was a small deviation from locality. As it turns out, the presence of such a “non-locality” modifies many well-known results in physics.

The type of non-locality I study is of a mild form: it respects Lorentz invariance and is not mediated by new particles, and its form is inspired by some models in string theory. With sufficient resolution in high energy experiments we may be able to constrain the value of this non-locality, or perhaps even measure it directly, providing insights on the subatomic structure of our Universe.

My PhD thesis is available for free on the arXiv, but it has also been published as a book in the Springer Theses series.