BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:Radiation from Global Cosmic Strings with Adaptive Mesh Refinement
  - Amelia Drew (DAMTP)
DTSTART:20210312T130000Z
DTEND:20210312T140000Z
UID:TALK157348@talks.cam.ac.uk
CONTACT:Justin Ripley
DESCRIPTION:Cosmic strings are a well-motivated potential source both of d
 ark matter axions and gravitational waves\, arising naturally from spontan
 eous symmetry breaking in field theories. Although they are modelled usefu
 lly by the Nambu-Goto action\, their complex non-linear dynamics introduce
 s uncertainties which can have a significant effect on their predicted rad
 iative spectra. We present adaptive mesh refinement (AMR) simulations of g
 lobal cosmic strings using the public numerical relativity code\, GRChombo
 \, to evolve the underlying complex field equations\, to address this issu
 e. We perform a quantitative investigation of the dynamics of single sinus
 oidally displaced string configurations\, studying a wide range of string 
 energy densities μ∝lnλ\, defined by the string width parameter λ over
  two orders of magnitude. We investigate the resulting massless (Goldstone
  boson or axion) and massive radiation signals\, using quantitative diagno
 stic tools to determine the eigenmode decomposition and compare the oscill
 ating string trajectory with an inverse square backreaction model accounti
 ng for radiation energy losses\, finding excellent agreement. We further f
 ind that non-linear massive radiation is (exponentially) suppressed with i
 ncreasing λ. We conclude that analytic radiation modelling in the thin-st
 ring (Nambu-Goto) limit provides the appropriate cosmological limit for gl
 obal strings. We comment on the implications of this study for predictions
  of axions and gravitational waves produced by cosmic string networks\, as
  well as preliminary work towards implementing global string evolution in 
 full numerical relativity.
LOCATION:Zoom
END:VEVENT
END:VCALENDAR