Solitons are non-dissipative, nontrivial solutions of partial differential equations. In many cases their stability is well understood, e.g. there can be topological reasons that prevent a... Show moreSolitons are non-dissipative, nontrivial solutions of partial differential equations. In many cases their stability is well understood, e.g. there can be topological reasons that prevent a localised lump of energy to dissolve and become dissipative. However, there are very persistent, soliton-like objects even when there is no obvious conservation law that would guarantee stability and explain longevity. This thesis considers such solutions, called oscillons, that appear in variety of nonlinear scalar theories. In essence, they are persistent oscillations of the field around the (local) minimum of the potential. A numerical study of oscillons in two spatial dimensions is presented. Use of absorbing boundary conditions in the numerical grid enables the study of radiation losses over a long period of time and permits quantitative approach to the lifetime of oscillons. Furthermore, it is shown that oscillons are emitted by collapsing domains, which way they could come into being in nature, e.g. in the conditions met in the very early Universe. Show less
