Visible objects in our Universe like stars or planets are composed of atoms that in turn are made of protons, neutrons, and electrons. But only about 16% of the matter in our Universe is composed of known particles, the nature of the remaining 84% is unknown and is usually referred to as dark matter. The aim of this project is to study a class of new particles that could form the dark matter and to suggest different ways how the existence of these particles could be revealed.
In particular, completely new window for studying our Universe was recently open by detection of the so-called gravitational waves. These ripples in the fabric of space and time can be produced by violent processes in the Universe like phase transitions between different phases of matter shortly after Big Bang. Such a phase transition could have happened also in the dark sector, and the aim of this project is to calculate the gravitational-wave spectra that could be measured by sensitive space-based experiments that are now being built and that could shed light on the nature of dark matter in this way.
Further, the dark matter particles studied in this project interact with each other which could alter the formation of structures in our Universe. Recent observations of matter distribution in galaxies and galaxy clusters indeed suggest that the dark matter could feature such self-interactions. As a part of this project, these observations will be used to put constraints on the properties of the dark matter particles.
Only about 16% of all the matter in our Universe is formed by the matter that we know from everyday life on Earth and that builds up stars. The nature of the remaining 84% is unknown and this component is usually referred to as dark matter as it does not interact with electromagnetic radiation and its presence is revealed only by its gravitational impact. Although there are reasons to believe that dark matter weakly interacts with the ordinary matter, range of experiments that are trying to confirm this have null results up to now. On the other hand, the success of recent experiments detecting gravitational wave signals opens new possibilities to shed light on the nature of dark matter and this might be the only source of information in certain dark matter models.
The objective of this project is to identify a class of dark matter candidates that is consistent with all cosmological and experimental constraints and to provide new testable predictions related to these scenarios. The project concentrates on the so-called strongly interacting massive particles (SIMP) that feature self-interactions, hence, can address the puzzle of small scale structure observations that are in tension with the assumption of collisionless cold dark matter. Interpretation of these observations is a matter of ongoing debate, hence, the constraints on self-interactions will be revisited in view of this current progress.
Moreover, strongly coupled theories in general may feature a strong first order phase transition and can, hence, be in principle revealed by future gravitational wave experiments looking for the so-called stochastic gravitational wave background. Predictions for this gravitational wave signal will be derived for the specific setup of SIMP models, but these results will be applicable to a wide class of strongly coupled models addressing different puzzles in particle physics.