Research interests
Fluctuation induced effects at boundaries
A plethora of new effects emerge from the confinement and modification of fluctuations near surfaces. These effects play an important role in the physics of nano-systems, atomic physics, and condensed and soft matter physics. A prominent example is the Casimir force between two plates due to quantum fluctuations of the electromagnetic field. Advancing the fundamental understanding of fluctuation-induced interactions in these systems requires a characterization of their dependence on surface shape and geometry. To this aim, in several breakthroughs, we were the first to develop new powerful methods to compute forces, heat radiation and transfer for arbitrary materials and shapes. One of our methods, the scattering (T operator) approach for arbitrary shapes, developed in 2006 has become a standard tool in the field. We now explore non-equilibrium systems, CFT based methods, and surface integral approaches with many new applications.
Sport science / Exercise physiology
Worldwide, a boom in investment and scientific interest in sports science has moved the field forward substantially, from an isolated sub-discipline of physiology to a shining example of the impact of multidisciplinary science. The rapidly growing amount of available exercise data from wearable devices holds a great potential for new quantitative research that is currently almost unexplored. While traditional lab studies are limited by a small sample of participants, big data collections make it possible to bring the laboratory to the road, and study millions of subjects under real world conditions. In our recent projects, we have developed a universal theoretical model for endurance performance and applied it to exercise data from thousands of runners, predicting marathon race times accurately and identify key predictive parameters of running performance. In another project, we used methods from statistical physics to analyze fluctuations of the human heart beat during physical exercise.
Urban climate
About half of humanity lives in urban environments today and that number will grow to 80% by the middle of this century. Cities have to be efficient, resilient, and sustainable, and they must address quality of life issues for their citizens. To achieve these goals, one has to understand the various processes and phenomena including local climate. New technologies provide opportunities for sensors to acquire a plethora of data with high spatial and temporal resolution. Employing a by-analogy strategy, we applied smaller scale concepts of statistical physics to study related effects at the much larger scales of cities. In our recent work, we have studied an urban climate phenomenon, known as urban heat island (UHI), resulting in an elevation of surface and air temperatures in cities when compared to their rural surroundings. Combining multi-year urban-rural temperature differences and building footprints data with a heat radiation scaling model, we showed for more than 50 cities world-wide that city texture can explain city-to-city variations in nocturnal UHI. We are currently exploring the UHI in New York City, combining longwave hyperspectral measurements with a geospatial radiosity model which describes the collective radiative heat exchange between multiple buildings.
Statistical mechanics: more projects
I have applied concepts from statistical physics to a wide range of further topics. Examples include elastic media with quenched disorder, superconductors, avalanche dynamics in granular media, dimer models, quantum magnets, and cellular automata for traffic flow.