Multi-Scale Pipeline for the Search of String-Induced CMB Anisotropies

Abstract

We propose a multi-scale edge-detection algorithm to search for the Gott-Kaiser-Stebbins imprints of a cosmic string (CS) network on the Cosmic Microwave Background (CMB) anisotropies. Curvelet decomposition and extended Canny algorithm are used to enhance the string detectability. Various statistical tools are then applied to quantify the deviation of CMB maps having a cosmic string contribution with respect to pure Gaussian anisotropies of inflationary origin. These statistical measures include the one-point probability density function, the weighted two-point correlation function (TPCF) of the anisotropies, the unweighted TPCF of the peaks and of the up-crossing map, as well as their cross-correlation. We use this algorithm on a hundred of simulated Nambu-Goto CMB flat sky maps, covering approximately 10% of the sky, and for different string tensions Gµ. On noiseless sky maps with an angular resolution of 0.9 , we show that our pipeline detects CSs with Gµ as low as Gµ 4.3 × 10 −10 . At the same resolution, but with a noise level typical to a CMB-S4 phase II experiment, the detection threshold would be to Gµ 1.2 × 10 −7 .

Cosmic string loop production functions

“…In an expanding and decelerating universe, a cosmic string network relaxes towards an attractor configuration exhibiting universal properties -known as a scaling solution -and it subsequently remains self-similar with the Hubble radius [5][6][7][8][9][10][11][12][13]. Hence if cosmic strings were formed in phase transitions early in the history of the universe, scaling implies that they should be present all over the sky with a surface density growing with redshift z. Strings induce anisotropies in the Cosmic Microwave Background (CMB) and they have been searched for in the Planck data [14][15][16][17][18][19].…”

Cylindrical asymmetric thin-shell wormholes

“…For curiosity, we want to know about cylindrical objects which are topologically related also with planar symmetric objects. Secondly, with their natural cylindrical symmetry, cosmic strings are shown not only to be involved in astronomical phenomena such as gravitational lensing effect [28,29], but also have roots in the foundation of the large-scale structure of the universe [30], and correlations with the JCAP10(2019)067 cosmic background radiation [31,32]. However, the viability of TSWs constructed by such spacetimes must be examined by constrains due to cosmological observations [33].…”

Stochastic gravitational waves from long cosmic strings

“…In this situation, only the long strings in a network would create persistent observable signatures and are constrained by their effects onto the Cosmic Microwave Background (CMB). The maximal possible energy scale compatible with the Planck satellite data [52] is around 10 15 GeV [30,[53][54][55][56][57][58]. Let us mention that a non-scaling cosmic string network, as one that would be formed during inflation, is even less constrained [59][60][61][62][63][64].…”