[Paper Review] Gravitational Waves from Supersymmetry Breaking

Nathaniel Craig|ArXiv.org|Feb 11, 2009

Cosmology and Gravitation Theories3 citations

TL;DR

This paper proposes that first-order phase transitions among metastable supersymmetry-breaking vacua in the early Universe generate a stochastic background of gravitational waves, detectable by future ground- and space-based interferometers. The peak frequency and amplitude of the gravitational wave spectrum are directly tied to the supersymmetry-breaking scale √F, with observable signals expected for √F ∼ 10⁴–10⁸ GeV, particularly in low-scale gauge mediation scenarios.

ABSTRACT

In theories of supersymmetry breaking, it is often the case that there is more than one metastable vacuum. First-order phase transitions among such metastable vacua may generate a stochastic background of gravitational waves, the observation of which would provide a direct window into the supersymmetry-breaking sector.

Motivation & Objective

• To investigate whether first-order phase transitions among metastable supersymmetry-breaking vacua can produce a stochastic gravitational wave background.
• To determine the detectability of such gravitational wave signals using next-generation ground- and space-based detectors.
• To link the observable properties of the gravitational wave spectrum—peak frequency and amplitude—directly to the supersymmetry-breaking scale √F.
• To assess the viability of probing low-scale gauge mediation scenarios through gravitational wave observations.

Proposed method

• Modeling the phase transition dynamics in supersymmetry-breaking sectors with multiple metastable vacua, focusing on the role of the primordial supersymmetry-breaking scale √F.
• Applying established formalisms for gravitational wave production during first-order phase transitions, including bubble wall collisions and plasma turbulence.
• Using the critical temperature Tc ∼ √F and nucleation temperature T* ∼ √F to estimate the peak frequency f_p ∼ (10⁻⁸ Hz) × (1/v_b) × (β/H_*) × (T_*/1 GeV) × (g_*/100)^(1/6) for the gravitational wave spectrum.
• Deriving the gravitational wave energy density Ω_gw(f) from collision and turbulence contributions, with turbulence dominating for stronger transitions.
• Comparing predicted gravitational wave amplitudes with sensitivity curves of future detectors such as AGIS, BBO, and LISA.
• Evaluating the phenomenological viability of low-scale gauge mediation (10⁴–10⁶ GeV) and gravity mediation (10¹¹ GeV) scenarios in light of detectability.

Experimental results

Research questions

• RQ1 Can first-order phase transitions among metastable supersymmetry-breaking vacua generate a stochastic gravitational wave background detectable by future interferometers?
• RQ2 How does the peak frequency and amplitude of the gravitational wave spectrum depend on the supersymmetry-breaking scale √F?
• RQ3 What is the relative contribution of bubble collisions versus plasma turbulence to the total gravitational wave signal in such phase transitions?
• RQ4 Which classes of supersymmetry-breaking models—particularly low-scale gauge mediation—yield observable gravitational wave signals?
• RQ5 How do the sensitivity curves of future detectors like AGIS, BBO, and LISA compare to the predicted gravitational wave spectra from these phase transitions?

Key findings

• A stochastic gravitational wave background is generated during first-order phase transitions among metastable supersymmetry-breaking vacua, with peak frequency f_p ∼ (10⁻⁸ Hz) × (1/v_b) × (β/H_*) × (T_*/1 GeV) × (g_*/100)^(1/6).
• The gravitational wave energy density Ω_gw(f) is dominated by turbulence for strong phase transitions (α ≳ 0.9), with the peak amplitude reduced by 4u_s² for u_s < 1/2.
• Gravitational wave signals from low-scale gauge mediation (10⁴–10⁶ GeV) are detectable by future space-based and ground-based interferometers such as AGIS and BBO.
• Signals from gravity mediation (10¹¹ GeV) are too high in frequency (f_p ∼ 1 MHz) to be accessible to space-borne detectors.
• The predicted gravitational wave spectrum for √F ∼ 10⁴ GeV with α = 1.0 lies within the sensitivity band of AGIS-S and BBO, while AGIS-G can probe up to √F ∼ 10⁶–10⁸ GeV.
• The detection of such gravitational waves would provide a direct observational window into the dynamics of the supersymmetry-breaking sector in the early Universe.