The fundamental structure of matter

Abstract: The subject of this thesis is "the fundamental structure of matter, that is, the quest of understanding the deepest level of the physical world, and the interactions relevant at that level. The hope is that, as one goes deeper, the laws are going to be simpler, not necessarily in mathematical terms, but in conceptual terms. The goal is fewer and fewer ad hoc assumptions, inspiring and driving the pursuit for the fundamental structure of matter. The thesis consists of an introductory part, giving a broad overview of where the subject stands today, and of a more detailed part, containing our own contributions to the advances of this knowledge. Six reproduced papers are appended at the end. There we treat the fundamental structure of matter on three different levels. The first three papers are concerned with the inner structure of particles (hadrons) that interact via the strong nuclear force. Here we have investigated the interactions of the so-called quarks inside hadrons, taking into account also their spin structure. Besides protons and neutrons, we have also studied more exotic particles containing quarks, so-called mesons, that are only produced in high-energy collision processes. Om a more fundamental, but speculative, level we have constructed a new model for an underlying substructure common to both quarks and leptons (particles unaffected by the strong interaction), i.e., all particles that build up matter. We also investigate some of the physical consequences of this model, particularly the possibility of radiative neutrino decay. On the large scale, we analyse the origin of the so-called dark matter in the Universe, which we propose is composed out of enormous lumps exclusively made of quarks, without any "normal" hadrons. We also explore the connection of this phenomenon to the mysterious bursts of gammarays seen in astrophysics.