Implications for First-Order Cosmological Phase Transitions from the Third LIGO-Virgo Observing Run

Area of Science:

• Cosmology
• Astrophysics
• Gravitational Wave Astronomy

Background:

• First-order phase transitions in the early universe are predicted to generate gravitational waves.
• Astrophysical sources, such as compact binary mergers, also produce gravitational waves that can act as foreground noise.

Purpose of the Study:

• To constrain the normalized energy density of gravitational waves from first-order strong phase transitions.
• To establish upper limits on gravitational wave signals from both astrophysical sources and early universe phenomena.

Main Methods:

• Utilized data from the first, second, and third observing runs of the Advanced LIGO and Virgo detectors.
• Employed a broken power law model to analyze gravitational wave data.
• Considered two additional phenomenological models to characterize specific gravitational wave backgrounds.

Main Results:

• Established 95% confidence level upper limits on gravitational wave energy density at 25 Hz: Ω_{CBC}<6.1×10^{-9} for compact binary mergers and Ω_{BPL}<4.4×10^{-9} for strong first-order phase transitions.
• Set upper limits for gravitational wave backgrounds from bubble collisions (Ω_{pt}<5.0×10^{-9}) and sound waves (Ω_{pt}<5.8×10^{-9}) for phase transitions above 10⁸ GeV.

Conclusions:

• The study provides stringent constraints on gravitational wave signals from early universe phase transitions.
• These results contribute to our understanding of cosmological models and the nature of gravitational wave sources.