Nikitas Stamatopoulos, Physics PhD Candidate

Department of Physics And Astronomy
Wilder Lab 113
Dartmouth College
Hanover, NH 03755

Phone: (603) 646-0947
Email: nstamato[at]dartmouth[dot]edu

Advisor: Marcelo Gleiser

My work is best viewed through videos of my simulations. Below you can watch the emergence of scalar oscillons in 1+1 dimensions in an expanding background from (quasi) thermal initial conditions. The field value is displayed on the left and the corresponding energy density is on the right. The oscillons emerge as localized peaks in the energy density of the field. In this case the field is oscillating about the minimum (\phi=0) in a \phi^6 potential. For more information see here and here.

Going over to 3+1 dimensions, the oscillons become slightly harder to visualize but they can be seen through isosurfaces in the energy density. Below you can see the oscillons forming after the universe has cooled off from the expansion. Again the field value is plotted on the left with isosurfaces at \phi=-1.3 (red) and \phi=-0.55 (blue). The field is oscillating about the minimum \phi=-1 in a symmetric double well potential. The corresponding energy density is shown on the right with an energy isosurface at E=0.2. More information here.

Recently, we have shown that oscillons emerge after the end of hybrid inflation for a wide range of parameter values, consistent with WMAP 7-year data. Simulations in 3+1 dimensions including Friedmann expansion in FRW space, show that oscillons can persist to contribute up to 20% of the energy density of the universe. In the video below, energy isosurfaces are plotted for 10 times the average energy of the simulation volume (light blue) and 12 times the average energy (purple). More information here.

If the Hubble volume is smaller than the size of the box of a 3+1 simulation, the system can evolve into the formation of domain walls. Plotted below, are isosurfaces of the field at \phi=0 (green). \phi=1 (blue) and \phi=-1 (red) for such a case.

In case you're not impressed by these, you can always see me playing the guitar!