Abstract
Abstract We consider a classical toy model of a massive scalar field in 1 + 1 dimensions with a constant exponential expansion rate of space. The nonlinear theory under consideration supports approximate oscillon solutions, but they eventually decay due to their coupling to the expanding background. Although all the parameters of the theory and the oscillon energies are of order one in units of the scalar field mass m, the oscillon lifetime is exponentially large in these natural units. For typical values of the parameters, we see oscillon lifetimes scaling approximately as τ ∝ exp ( k E / m ) / m where E is the oscillon energy and the constant k is on the order of 5 to 15 for expansion rates between H = 0.02 m and H = 0.01 m .
Highlights
Central to many unsolved problems in particle physics and cosmology, ranging from the flatness of the slow-roll inflaton potential to the hierarchy of scales in grand unified theories, is the need to understand the origin of “unnaturally” large or small dimensionless parameters
We show that in the presence of an expanding background metric, oscillons in a simple toy model have lifetimes that are exponentially large compared to the natural scales of the system, even though all the inputs to the theory are of order one in these units
Such models have a curious property: in a simple, classical theory in which all parameters are of order one in natural units, classical dynamics generate a quantity — the oscillon lifetime — that is exponentially large compared to the natural scales of the system
Summary
Central to many unsolved problems in particle physics and cosmology, ranging from the flatness of the slow-roll inflaton potential to the hierarchy of scales in grand unified theories, is the need to understand the origin of “unnaturally” large or small dimensionless parameters. In a broad class of one-dimensional models, perturbative analyses [1] and numerical simulations [3, 9] suggest that the oscillon lifetime is infinite, but analytic arguments [12] point to the existence of non-perturbative, exponentially suppressed decay modes Such models have a curious property: in a simple, classical theory in which all parameters are of order one in natural units, classical dynamics generate a quantity — the oscillon lifetime — that is exponentially large compared to the natural scales of the system. Φis the derivative of φ with respect to time and φ′ is the derivative of φ with respect to the comoving coordinate x This expansion destabilizes oscillons whose width is of order of the horizon size 1/H, but in numerical simulations we observe that oscillons of smaller size remain stable, maintaining a fixed size in physical units. We do not need to expand the box proportionally to the runtime [11] or introduce absorbing boundaries [18] in order to prevent unwanted reflections from disturbing the oscillon solution under study
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
