Cosmic string scenario was the first mechanism to provide the origin of density fluctuations that seeded cosmic large-scale structures from fundamental physics.Zeldovich 1980, Vilenkin 1981, & participants of this workshop with age > 0.5C yrsAnother proposal for the origin of density fluctuations was quantum fluctuations from inflation.A single parameter explains everythingMukhanov&Chivisov, Starobinsky, Hawking, Guth-Pi 1982,
As of early 1990scosmic stringsinflationspectrum of fluctuationsscale invariantscale invariantamplitude of fluctuationsfine-tuning dark mattercold or hotrequires CDMmonopole problemincompatiblenaturally solvedhorizon & flatnessproblemsno explanationnaturally solved
Cosmic string scenario explained the origin of fluctuations at least equallywell compared with inflation models (or even better if DM was hot),but cannot explain global properties (i.e. homogeneity & isotropy) of theUniverse at all.So in order to make a fully consistent cosmology, I thought cosmic stringsshould be formed during or after inflation.Oriental Medicinetreat the body as a whole systemOccidental Medicinetreat each sick partseparately
Abelian Higgs model
Cosmic strings are naturally produced after inflation.Furthermore, string density can be controlled if phase transition occurs during inflation rather than after inflation.(JY 1988)(JY 1989)cf Previous models of string formation after inflation introduced interactions between the inflaton and the string-forming field. (Shafi, Vilenkin 1984, Vishniac, Olive, Seckel 1987,) I expected everyone working on cosmic strings would like the idea, and use it.But in fact, no one used it.Because they did not care horizon/flatness/monopole problems.Because cosmic string scenario was a rival against inflation, so they did not want to have a help from its adversary.Do we need an adversary to do physics??
F term inflationcanonical kinetic termThe scalar potential contains a Hubble-induced mass termsimilar to that induced by the nonminimal coupling in the previous model.
We findSymmetry breaking (=string formation) startswhen becomes negative.inflationHubble parameter at string formation EXTRADILUTIONNumber of e-folds of inflation thereafter
Typical separation & characteristic length of strings at redshiftscale factor at the end of inflationinitial separation of stringsLoop formation by intercommutation will not start until this scale fallsshorter than the Hubble radius.Formation of small loops is suppressed, and we can evade pulsar constraints on gravitational waves from loops.
Numerical simulations in conventional scaling scenario shows that iswidely distributed between 10-7 and 0.1(Blanco-Pillado, Olum, Shlaer 2011&2014)But in our scenario, strings are stretched and small-scale structures aresmoothed out by inflation until well after the scaling regime is achieved, so we assume hereafter.
Constraint on Gm as a function of the beginning of scaling regime (Miyamoto, Yamauchi, JY 2014, preliminary)
In terms of model parametersdilution
Cosmology must be self consistent.Cosmic string formation should be considered in inflationary cosmology.We proposed some natural mechanisms of string formation in this context.Pulsar constraints can be evaded while future CMB experiment maydetect traces of cosmic strings.Physics with no potential adversaryI wish someone will do numericalsimulations of a string network starting from inflationary initialcondition, namely, from a diluteand straight configuration.