Level Crossing Analysis of Cosmic Microwave Background Radiation: A method for detecting cosmic strings

TL;DR

This paper introduces a level crossing analysis method to detect cosmic strings in the cosmic microwave background, demonstrating its effectiveness in simulations with specific tension thresholds and noise considerations.

Contribution

The paper develops a novel level crossing analysis technique for identifying cosmic strings in CMB maps, extending previous methods by quantifying detection thresholds.

Findings

Detects cosmic strings with tension Gμ ≥ 4×10⁻⁹ in noise-free simulations

Detection threshold increases to Gμ ≥ 5.8×10⁻⁹ with instrumental noise

Method effectively distinguishes cosmic string signatures from Gaussian fluctuations

Abstract

In this paper we study the footprint of cosmic string as the topological defects in the very early universe on the cosmic microwave background radiation. We develop the method of level crossing analysis in the context of the well-known Kaiser-Stebbins phenomenon for exploring the signature of cosmic strings. We simulate a Gaussian map by using the best fit parameter given by WMAP-7 and then superimpose cosmic strings effects on it as an incoherent and active fluctuations. In order to investigate the capability of our method to detect the cosmic strings for the various values of tension, $G\mu$, a simulated pure Gaussian map is compared with that of including cosmic strings. Based on the level crossing analysis, the superimposed cosmic string with $G\mu\gtrsim 4\times 10^{-9}$ in the simulated map without instrumental noise and the resolution $R=1'$ could be detected. In the presence of anticipated instrumental noise the lower bound increases just up to $G\mu\gtrsim 5.8\times 10^{-9}$.