Research in theoretical physics

Statistical physics of complex systems: chaotic scattering – over-50-year-old problem solved

The word “chaos” is associated with a lack of structure, but precisely it can lead to universal statistical properties. Much of what we know about quantum systems comes from scattering experiments. Over 50 years ago, the question of universal distribution of cross sections first came up in nuclear physics. Later, when the close relationship between chaotic dynamics and the general nature of the question for the chaotic scattering of random quantum systems was understood, it was still impossible to solve the problem on account of its very complicated mathematical structure. The members of the Guhr research group have now succeeded in doing this in international collaboration using a supersymmetrical method developed in the group to solve the statistical problem.

Nanoparticles in the quantum regime

Quantum physics is known to work perfectly for microscopic particles such as atoms and photons, but its predictions turn our “classical” ever­yday experience upside down if they are applied to tangible objects. It should then be possible for one and the same object to exist simultaneously in different places and its dynamic behaviour be determined by whether or not it is observed. Prof. Klaus Hornberger’s group investigates systems that belong to the transition region between the quantum regime and classical physics.

A focus of the group’s work over the past two years has been in theoretical modelling of the gyro­dynamics of nanoscale rods suspended by laser light. By applying these theories, the researchers were able to demonstrate an ultraprecise pressure and torque sensor and develop a realistic proposal for transforming the state of the nanoparticle into a Schrödinger’s cat of unachieved macroscopicity.