Theoretical Physics Division seminar

ABSTRACT:

In my presentation I will overview selected modern techniques of calculating scattering amplitudes in Quantum Chromodynamics in a non-technical and rather basic manner. The modern methods allow not only to increase the

precision of calculations, needed to test the theory in high energy experiments, but they also can change our fundamental understanding of the theory of strong interactions.

                                                                                            Serdecznie zapraszamy,

Most of known fermionic systems become superfluid (or superconducting if particles are charged) at sufficiently low temperatures. They include electrons in metal, nuclear systems like nuclei or neutron stars, and also ultra-cold atomic gases. Developments of last decade, both theoretical and computational, resulted in an accurate and numerically tractable formulation of superfluid Density Functional Theory, known presently as time-dependent superfluid local density approximation (TDSLDA).

Dark matter (DM) candidates appear in a number of models that extend the scalar sector of the Standard Model. Commonly, the stability of DM in such models is guaranteed by a symmetry of the Lagrangian. In this talk I consider a model which allows one to stabilise DM with the CP symmetry of a more general form. Furthermore, this model introduces by construction an interesting interaction patter in the dark sector. I discuss, how this novel feature affects the thermal evolution of DM in the early Universe and the perspectives of indirect detection.

The main difficulty to address the continuity of perturbative QCD between moderate and high energies was recently solved by rewriting the theoretical descriptions of both limits in terms of the same parton distributions. I will briefly discuss this equivalence, and its implication on the saturation effects which are expected at asymptotic energies. At such energies, effective particles with the quantum numbers of the vacuum are exchanged in the t channel. While the C-even exchanges are rather well known, a C-odd exchange is also expected.