Constraints on Cosmic Strings Using Data from the Third Advanced LIGO-Virgo Observing Run.

Area of Science:

• Astrophysics
• Cosmology
• Gravitational Wave Astronomy

Background:

• Cosmic strings are hypothetical topological defects potentially formed in the early universe.
• Gravitational waves (GWs) from cosmic strings offer a unique probe of fundamental physics and early universe cosmology.
• The Advanced LIGO and Virgo observatories provide unprecedented sensitivity to detect GWs.

Purpose of the Study:

• To search for and constrain gravitational-wave signals from cosmic strings using the full O3 dataset.
• To investigate GW signals from various cosmic string loop features, including cusps, kinks, and kink-kink collisions.
• To improve constraints on the cosmic string tension parameter (Gμ) and test inflationary models.

Main Methods:

• A template-based search for short-duration transient GW signals from cosmic strings.
• Analysis of stochastic GW background energy density upper limits from O3 data.
• Development and testing of cosmic string loop distribution models to constrain Gμ.

Main Results:

• No direct detection of GWs from cosmic string loop features was made.
• Stochastic GW background upper limits significantly improved constraints on Gμ by 1-2 orders of magnitude.
• The most competitive constraints to date were set: Gμ≲4×10^{-15} for a one-loop distribution model.

Conclusions:

• The study places stringent limits on cosmic string properties, ruling out certain parameter spaces.
• The improved constraints challenge simple inflationary models, particularly those involving cosmic strings formed at the end of inflation.
• This work highlights the power of GW astronomy in probing fundamental physics and early universe scenarios.