About me

RESEARCH INTERESTS

CPT- and Lorentz symmetry violation

My work focuses on studying CPT- and Lorentz violation, which is motivated by certain prototype fundamental theories such as string theory and loop quantum gravity. The field is a thrust in modern fundamental research, since Lorentz violation is a clear indicator for physics at the Planck scale and its discovery would radically change our physical paradigm. The community is very active with hundreds of research papers produced over the past 15 years on theory and experiment.
The research is carried out within the Standard-Model Extension (SME), which is a low-energy effective framework for parameterizing such violations in the Standard Model of elementary particle physics and General Relativity. The minimal SME involves all operators with a mass dimension ≤ 4, whereas the nonminimal part comprises all higher-dimensional operators. My interests within the SME are multifold. They range from theoretical aspects auch as the properties of Lorentz-violating quantum field theories to more phenomenological topics, e.g., constraining Lorentz-violating coefficients by measurements.

Particle Phenomenology

Experimental data on ultra-high energy cosmic rays provide an essential basis for the search for CPT- and Lorentz violation. In the past vacuum Cherenkov radiation was studied thoroughly for many sectors of the SME. In contrast, not much research has been carried out on photon decay and there is a great potential in obtaining new bounds from recent data on ultra-high energy photons (measured, e.g., by H.E.S.S). From the modified photon dispersion relation the decay rate would be computed within the nonstandard quantum field theory based on the Lorentz-violating coefficients to be bounded. This allows for gaining information on the efficiency of the process. The bounds follow from the modified kinematics and the experimental data.

Quantum Field Theory

The SME is based on the concept of field theory and after quantization it describes the physics of all Standard-Model particles in the presence of Lorentz violation. I find it fascinating to explore the properties of such modified quantum field theories and to investigate whether they are still well-behaved. This concerns a large variety of characteristics such as microcausality, unitarity, stability, etc. In a series of research articles Lorentz-violating quantum field theories were investigated where I mainly focused on the CPT-even photon sector and the nonminimal fermion sector. My calculations were carried out in perturbation theory with respect to the fine structure constant. They involve the computation of modified free-field objects such as photon polarization vectors, fermion spinors, and propagators. These are then used to either show the properties mentioned above or to demonstrate that they do not hold for certain cases. All results obtained in the past years suggest that quantum field theories seem to be very robust with respect to Lorentz violation, i.e., except for some rare, pathological cases they are well-behaved at tree-level.

Modifications of General Relativity

The SME includes a framework for a modified theory of gravity. The recent approach of Finsler geometry is very promising to describe Lorentz-violating background fields in curved spacetimes. However it is still in its infancy and there are many questions to be answered.