Direct Observation of Cosmic Strings via their Strong Gravitational Lensing Effect: I. Predictions for High Resolution Imaging Surveys

TL;DR

This paper predicts the number of strong gravitational lensing events caused by cosmic strings in high-resolution imaging surveys, showing that current and future surveys can significantly improve constraints on cosmic string tension.

Contribution

It provides theoretical estimates linking survey resolution and area to the ability to detect or constrain cosmic strings via gravitational lensing effects.

Findings

HST resolution can probe Gμ/c² ~ 10^{-7} with a few square degrees

Non-detection can double current limits on string tension

Future surveys could lower the limit to Gμ/c² < 10^{-8}

Abstract

We use current theoretical estimates for the density of long cosmic strings to predict the number of strong gravitational lensing events in astronomical imaging surveys as a function of angular resolution and survey area. We show that angular resolution is the most important factor, and that interesting limits on the dimensionless string tension Gmu/c^2 can be obtained by existing and planned surveys. At the resolution of the Hubble Space Telescope (0.14"), it is sufficient to survey of order a few square degrees -- well within reach of the current HST archive -- to probe the regime Gmu/c^2 ~ 10^{-7}. If lensing by cosmic strings is not detected, such a survey would improve the limit on the string tension by a factor of two over that available from the cosmic microwave background. Future high resolution imaging surveys, covering a few hundred square degrees or more, either from space in the optical or from large-format radio telescopes on the ground, would be able to further lower this limit to Gmu/c^2 < 10^{-8}.