Latest news:
Our new work on a Quantum spin transistor in a Heisenberg spin chain has been published in Nature Communications!
Our work on strongly interacting one-dimensional systems has also been published in Nature Communications:
General description:
Few-body physics is a general name given to physical systems with a small number of constituents. Historical examples from classical physics are the Earth-Sun two-body system that is controlled by the gravitational forces, and the more exotic Sun-Earth-Moon three-body problem where one seeks to take the effect of the Moon into account. The lessen from classical physics is that going from two to three bodies makes the problem much more complicated! With the century old realisation that microscopic physical systems such as atoms and molecules have non-classical behavior and must be described by quantum mechanics a new area of few-body physics began. As it turns out the quantum mechanical few-body problem is in most cases more complicated than the corresponding classical problem, but this does not make it any less interesting or relevant for that matter! Atoms, small molecules, nuclei, and particle systems constitute few-body problems for which we need an accurate description both from a theoretical and applied point of view.
On the other hand, it is well known that many systems that we see in nature and use in experiments and in applications have huge particle numbers. It is generally hopeless to describe the behavior of all these particles. To provide a physical framework and theory one needs to develop models where the average properties of many particles are the main variables. This could be the average interaction of a single atoms in a gas with all the other atoms in the system. Many-body theories such as statistical and quantum statistical mechanics as well as quantum many-body theory and its various numerical techniques constitute an extremely powerful framework that allow us to understand and make predictions about systems with large particle numbers.
What is much less clear are the borderline cases where the particle number is somewhere in between. More precisely, one may ask when is it appropriate to consider a system to be few-body and when should we think of a system as a true many-body system?
This question can be rephrased in a more precise and quantitative manner by asking: When do we get accurate results by applying few-body methods and when do we get accurate results from many-body methods for a given system at hand. Or even more precisely: What is the accuracy of applying either few- or many-body formalism?
The project FEW-BODY PHYSICS IN A MANY-BODY WORLD attacks this question by combining few- and many-body techniques into a combined framework that should be applicable to different physical systems in both atom, molecular, nuclear and condensed-matter context.
What is particularly exciting at the moment is that cold atomic gases containing neutral atoms or molecules can be used to interpolate between the limits of few- and many-body systems, allowing direct tests of our formalism and its predictions.
The project is funded by a Sapere Aude: DFF-Starting Grant from 2013 to 2016.
