What is heat super symmetry

Quantum field theory and elementary particle theory

Research over the past decades has shown that known matter is composed of a relatively small number of building blocks. These are on the one hand the quarks from which z. B. exist the atomic nuclei, and on the other hand around the so-called leptons, which also include the electrons that form the atomic shell.

Four different types of forces act between these particles. In addition to gravity, which does not play a major role in the atomic range, these are the electromagnetic forces, the so-called weak and strong interactions. The latter two are responsible for processes in the field of atomic nuclei and elementary particles, e.g. B. for radioactivity and nuclear fusion.

The fundamental particles and their interactions (apart from gravity) are theoretically described by the “standard model” of elementary particle physics. It was formulated in the 1970s and almost without exception is consistent with the innumerable experimental findings in particle physics. The standard model satisfies the principles of quantum theory and special relativity and is an example of a “quantum field theory”.

In the standard model, the forces between matter particles are transmitted by different messenger particles. One example are the "field quanta" of the electromagnetic force field, which are identical to the light quanta, the photons.

In our working group we deal with a wide range of questions from the field of quantum field theory. There are theoretical approaches to physics beyond the Standard Model, which could reveal itself at very high energies. These approaches use the concept of supersymmetry, a symmetry that extends the usual space-time symmetry. We investigate, among other things. basic properties of supersymmetric theories. Some of the bills can be done with pencil and paper. However, many problems cannot be solved in this way and require the use of numerical methods. For this purpose, we also carry out extensive calculations on supercomputers. In these calculations it is necessary to replace the continuum of space and time with a grid. In this way you are dealing with a finite number of variables that can be handled numerically. The calculation of physical quantities is very complex and is carried out with the help of statistical methods.

Another area of ​​our research includes the theory of the strong interactions of elementary particles. This is contained in the standard model in the form of so-called quantum chromodynamics. Due to the strength of the interaction between quarks, common approximation methods, which assume that the couplings are sufficiently small, fail. To calculate the properties of strongly interacting elementary particles, computer methods are used in which the quantum chromodynamics is placed on a grid. Masses and other characteristics of the particles can then be calculated. The results of such calculations are very important for comparison with experimental results.

When studying theories on a grid, the grid has to be fine enough to be able to resolve the details of the particles, on the other hand the entire grid has to be big enough to contain a particle completely. A great demand for computing power results from these requirements.

For the calculations, we use computing power that is made available to us on parallelized supercomputers at the Neumann Institute for Computing (NIC) in Jülich and at DESY-Zeuthen.

Another part of our activities is not about elementary particles. Remarkably, certain phenomena in the field of thermodynamics, the physics of heat, can also be described with the means of quantum field theory. This applies in particular to phase changes such as evaporation, melting and condensation. In our working group we use this connection to obtain results about systems of thermodynamics with methods of quantum field theory.

One example is the behavior of interfaces. Many systems have interfaces that separate different phases from one another, e.g. B. interfaces between gas and liquid or between different liquids. When the temperature rises, an interface can dissolve and the previously separated phases mix. The way in which the interface disappears and typical properties of the interface, which are also accessible experimentally, can be described and calculated with the help of quantum field theory.

Phase changes, such as B. the condensation of steam, can begin by nucleation. The condensation nuclei form droplets which then expand. The mechanism of droplet formation and the rate of nucleation during phase changes are studied by us using quantum field theory.