Primordial Clocks within Stochastic Gravitational Wave Anisotropies

Abstract

A first-order phase transition in the early universe can give an observable stochastic gravitational background (SGWB), which will necessarily have primordial anisotropies across the sky. In multi-field inflationary scenarios, these anisotropies may have a significant isocurvature component very different from adiabatic fluctuations, providing an alternate discovery channel for high energy physics at inflationary scales. Here, we consider classically oscillating heavy fields during inflation that can imprint distinctive scale-invariance-breaking features in the power spectrum of primordial anisotropies. While such features are highly constrained in the cosmic microwave background, we show that their amplitude can be observably large in isocurvature SGWB, despite both probing a similar period of inflation. Measuring SGWB multipoles at the required level, $\ell \sim \mathcal{O}(10-100)$, will be technologically challenging. However, we expect that early detection of a strong isotropic SGWB, and the guarantee of anisotropies, would spur development of next-generation detectors with sufficient sensitivity, angular resolution, and foreground discrimination.

10 pages, 5 figures

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Cited by in corpus (5)

• Stochastic gravitational wave background phenomenology in a pulsar timing array
• Enhancing gravitational wave anisotropies with peaked scalar sources
• New universal property of cosmological gravitational wave anisotropies
• Back to the features: assessing the discriminating power of future CMB missions on inflationary models
• Large Primordial Fluctuations in Gravitational Waves from Phase Transitions