The research field of theoretical particle physics deals with the theoretical understanding of the properties of matter and their interactions. Here, different approaches (lattice gauge theory, perturbation theory) are pursued in order to answer, for example, the question of the origin of mass and the evolution of the universe. State-of-the-art computer systems are used and developed for the associated calculations.

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The research group of Prof. Knechtli deals with simulations of the theory of strong interaction, quantum chromodynamics (QCD) on the lattice. In particular, novel algorithms are developed in the framework of the DFG research group "Future Methods for Studies of Trapped Gluons in QCD (FOR 5269)" (https://confluence.desy.de/display/for5269).(https://confluence.desy.de/display/for5269). The interests of the group are the physics of charmonium, glueballs and hybrid mesons, the static potential and the calculation of the strong coupling constant. Besides QCD, gauge theories in 5 dimensions and spin models are studied using Monte Carlo simulations.

The main focus of Prof. Hölbling's work is the numerical treatment of quantum field theories. In addition to computations in phenomenological lattice QCD, whose main goal is consistency tests of the Standard Model and related searches for new physics, he also deals with conceptual and algorithmic issues of discretized quantum field theories. These include, besides the understanding of chiral and other symmetries on the lattice, especially the construction of improved effects. Furthermore, Prof. Hölbling is working on the real-time dynamics of quantum fields and their interaction with semiclassical gravity. Go to the website of Prof. Hölbling here

Prof. Günther's research focus is the study of the QCD phase diagram using lattice gauge theory methods. In particular, she is concerned with the behavior of QCD matter at finite densities, which is a particular challenge for lattice QCD calculations. Here, the notorious "sign problem" prevents the use of the established Monte Carlo simulations, which is why new methods are sought or extrapolations are used to solve QCD in this domain. The knowledge gained in this way can be used to understand heavy ion collisions at particle accelerators in order to theoretically explain the results obtained there from first principles. To reproduce the experimental conditions in lattice QCD simulations, Prof. Günther uses the method of analytical continuation of imaginary chemical potential.