Oscillons, localized oscillating configurations in nonlinear field theories, have been known to exist since the mid 1990’s. Since then a lot of research has been done to understand these exotic...Show moreOscillons, localized oscillating configurations in nonlinear field theories, have been known to exist since the mid 1990’s. Since then a lot of research has been done to understand these exotic solutions. They can emerge under rather general conditions and have been found to exist in well-motivated physical models. Although they have been studied extensively in single-field models, not a lot is known about them in theories where fields interact. In this thesis I try to gain insights into the complicated questions surrounding multi-field oscillons. In the first chapters I start by reviewing what oscillons are in the context of single-field models. I also show why it is generally expected that oscillons might have an impact on early Universe cosmology. In the last chapters I tackle multi-field oscillons in the context of two coupled scalar fields. I manage to find stable oscillons in a model with a specific ”exchange” symmetry and find a criterion to assess their stability by extending the Vakhitov-Kolokolov criterion. Oscillons in this system can both exist in in-phase and out-of-phase configurations, highlighting an interesting characteristic of oscillons in multi-field theories. Finally, I analyse oscillons in more general models of scalar fields, showing the influence of a mass mismatch on the oscillon solution and discussing its influence on stability. I conclude with some expected differences between symmetric and asymmetric couplings between the fields that need to be tested in the future.Show less
