Signature of cosmic string wakes in the CMB polarization

Abstract

We calculate a signature of cosmic strings in the polarization of the cosmic microwave background (CMB). We find that ionization in the wakes behind moving strings gives rise to extra polarization in a set of rectangular patches in the sky whose length distribution is scale-invariant. The length of an individual patch is set by the co-moving Hubble radius at the time the string is perturbing the CMB. The polarization signal is largest for string wakes produced at the earliest post-recombination time, and for an alignment in which the photons cross the wake close to the time the wake is created. The maximal amplitude of the polarization relative to the temperature quadrupole is set by the overdensity of free electrons inside a wake which depends on the ionization fraction f inside the wake. The signal can be as high as 0.06µK in degree scale polarization for a string at high redshift (near recombination) and a string tension µ given by Gµ = 10 −7 .

Self-force on an arbitrarily coupled scalar charge in cylindrical thin-shell spacetimes

“…For the static charge placed in Type I or Type II geometries, the field equation (5) in cylindrical coordinates becomes…”

Thin shells joining local cosmic string geometries

“…From Eqs. (15), (16), and (17), the static values of the energy density and pressures at the throat are…”

“…The local a e-mail: eiroa@iafe.uba.ar b e-mail: erdec@df.uba.ar c e-mail: csimeone@df.uba.ar flatness of the metric implies zero force on a static particle, but relativistic particles would be deflected, and moving strings would give rise to wakes behind them [3][4][5][6][7]. Thus, though cosmic strings are not supposed today to be the main source of the primordial cosmological matter fluctuations, they can still be of relevance as a secondary source of fluctuations [13][14][15][16]. In the context of axisymmetric spacetimes, the simplicity and the physical interest of the local string metric would make it comparable to the Schwarzschild metric within spherically symmetric geometries.…”

Arbitrarily coupled massive scalar field in conical thin-shell spacetimes

“…The interest on cosmic strings has been mainly driven by the prediction of these observable effects. In particular, they have been considered as candidates for the generation of density fluctuations leading to structure formation; while in the last years they have been discarded as the main source for such cosmological process, in the present framework they are considered as possible secondary seeds for structure formation [8].…”