File:Cosmic strings evolution during the expansion of the Universe.webm

English: This movie shows a small Nambu-Goto cosmic string simulation in a Friedmann-Lemaître matter-dominated expanding Universe. The box is a fixed comoving volume containing initially 50 correlation lengths of strings created from Vachaspati-Vilenkin (VV) initial conditions. Each string is made of 20 points per correlation length.

The first part of the movie shows the VV initial conditions, where the strings are essentially distributed along a cubic crystal system. Then, evolution is switched on. The lower right number shows the Hubble radius, normalized to the size of the comoving box. It gives the typical size of the observable universe. The evolution runs as long as the Hubble radius remains within the comoving box, above which periodic boundary conditions would start to be significant. During the run, strings are color-coded. White strings are longer than the Hubble radius, red strings are loops smaller that the Hubble radius which evolves as predicted by the so-called "scaling regime", an universal attractor. Other structures are not yet relaxed and are made of small loops. Freshly formed small loops are yellow, and get bluer with time. Therefore, very old and very small loops, not yet in scaling, are very blue.

Finally, the movie ends with a frozen configuration at the time the observable universe fills the whole box. The virtual observer rotates around the box and plunges in to give some inner view of the structures