 My Research Interests
Physics Beyond the Standard Model My main interests are theories beyond the Standard Model. I am especially interested in different approaches to Quantum Gravity and their phenomenology, like the occurrence of a minimal length scale as UV-regulator, extra dimensions, modifications of Lorentz-invariance, the generalized uncertainty principle, quantum fields in curved spacetime and black holes physics. I find it promising to examine interrelationships between these topics, and I strive to develop models that are useful to directly test a given assumption. In this context, brane world scenarios are an intriguing subject which relates String Theory to existing effective models and allow us to approach a variety of topics: from the fermion mass hierarchies, over the mechanism of symmetry breaking to black holes and cosmology. Besides the string theoretical motivations, the possible existence and detection of extra dimensions has been a central point in my work [hep-ph/0112186,hep-th/0309066,hep-ph/0607112]. More generally, during my research I have been working on possible manifestations of the phenomenology of Quantum Gravity and String Theory, and examined applications for physics at the Planck scale, such as black hole and graviton production [hep-ph/0109085, hep-ph/0412265, hep-ph/0507138]. Even though these effective models are not fundamental, they allow us to make testable predictions for high energy physics and might help us to learn about the general structure of the unknown underlying theory. This is an exciting branch of physics which lives at the intersection of theoretical and experimental physics. Some years ago, I worked out a model which includes the effects of a minimal length scale into quantum field theory [hep-th/0305262] possibly with extra dimensions [hep-ph/0410122], and used it in several applications [hep-ph/0308138, hep-th/0502142, hep-ph/0405127, hep-th/0404232], some of which are still work in progress [0712.2811] . This model is related to Deformed Special Relativity [hep-th/0510245, hep-th/0702016], but differs in the implementation of the minimal length [hep-th/0603032, gr-qc/0612167]. The Cosmological Problems Cosmology and astrophysics today offer the theoretical physicist many problems to tackle which makes it an attractive research field. The most pressing questions are what is the microscopic origin of dark matter and dark energy. But also the connection to Quantum Gravity is intriguing, addressing the issue of singularity avoidance and vacuum energy. Recently, I have been working on a modification of General Relativity through a bi-metric model that introduces a mirror-matter which moves according to the Levi-Cevita connection of the second metric [0807.2838]. I have not yet closely investigated its potential to address some of the cosmological problems, but I am presently working with some collaborators on structure formation and gravitational lensing. I would like to pursue this further, both to study observational consequences as well as to better understand the theoretical implications. Intersection of Social and Natural Sciences Besides my work in theoretical physics, I am interested in interdisciplinary work combining insights from the social, the natural and the computer sciences. I believe that there is a large untapped potential in the communication between these different fields, and that a better understanding of the relations between them would be of advantage to our civilization's ability to face the challenges of the future. Network science, complex systems, web science, and systems theory, among others, fall into this category, but this intersection also includes the sociology of science, science policy making, scientometric, knowledge management and decision science that influence in many ways directly and indirectly how science is done and integrated into our daily lives. You can find out more about this on the websites of the Lightcone Institute, or on my blog, e.g. in the posts The Marketplace of Ideas, We have only ourselves to judge on each other, The Illusion of Knowledge, and Cast Away.
My Top 10
Unsolved Questions in Theoretical Physics
(See also the discussion on my blog.) - How can the apparent disagreement between general relativity (GR) and quantum gravity be resolved? Does it require to quantize gravity? If so, how? If not, see 2 and 3.
- Do black holes destroy information? If not, what happens to the matter that collapses to a black hole?
- Are there really singularities in GR (inside black holes/big bang)? If so, how can we understand what happens there? If not, how are they avoided?
- How can we explain the data (supernovae, WMAP) which seems to indicate that the universe is filled with dark energy. Is there really dark energy? If so, what is it? Why does it become important just now (coincidence problem)?
- How can we understand the rotation curves of galaxies, and the too large sizes of voids between galaxies. Does dark matter exist? If so, what is it made of?
- 6) What happened in the very early stages of the universe? How can we solve the horizon/flatness/homogeneity problem? Did inflation really take place? If so, what is the inflaton? How does electroweak symmetry breaking work? Where does the baryon-antibaryon asymmetry come from?
- Why do we experience 3+1 dimensions? Are there extra dimensions? If so, why haven't we yet noticed them?
- Are the electroweak and strong interaction unified at high energies? If so, are the currently known particles of the standard model (SM) elementary? Are there more yet unobserved particles? Why are the parameters of the SM what they are and are they in yet unknown ways related to each other (or are they related to 1. or 6.?). Why are the gauge groups of the SM what they are?
- Can we understand quantization?
- What causes particles to have masses and why are these so much smaller than the Planck mass (and hence the gravitational interaction so weak, alias the hierarchy problem)?
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