Research Group of Prof. Dr. Frans R. Klinkhamer
Focus: fundamental aspects of elementary particle physics and structure of spacetime  
Four main topics:  
1. Baryon number violation through nonperturbative effects in the Electroweak Standard Model:  
Sphalerons and spectral flow:
New results on spectral flow and sphalerons have been obtained in [Klinkhamer & Lee, 2001] and are under investigation. Two reviews: [Klinkhamer, 2002; Klinkhamer & Rupp, 2003]. The sphaleron $\text{S}$ is related to the AdlerBellBardeen anomaly. Over the years, it has become clear that there are more sphalerons. In fact, there also exists a sphaleron $\text{S}^{*}$ related to the $SU(2)$ Witten anomaly; see [Klinkhamer, 1993]. And, finally, there exists a sphaleron $\widehat{\text{S}}$ related to the $SU(3)$ Bardeen anomaly; see [Klinkhamer & Rupp, 2005; Klinkhamer & Nagel, 2017].  
2. CPT anomaly:  
Chiral gauge theories defined over a topologically nontrivial space manifold have an anomalous breaking of Lorentz and CPT invariance. An extensive review: [Klinkhamer, 2005].  
 
 
 
 
 
3. Smallscale structure of spacetime:  
The goal is to investigate a possible nontrivial structure of spacetime at very small length scales.
 
4. Vacuum energy and cosmology:  
Since 1998, it has become clear that there is not one cosmological constant problem but that there are three:  
 
Taking Lorentzinvariance seriously (cf. recent UHECR bounds on Lorentz violation in the photon sector [Klinkhamer et al., 2017]), a new approach [Klinkhamer & Volovik, 2008] to this set of problems is based on the following assumption: the perfect quantum vacuum can be considered to behave as a selfsustained Lorentzinvariant medium with a new type of conserved charge. The argument is based solely on thermodynamics (cf. Einstein 1907) and has an analog in condensedmatter physics (LarkinPikin effect, 1969).
Recent results are reviewed in
[Klinkhamer & Volovik, 2016;
Klinkhamer & Volovik, 2019].
 
Some talks:  
