Measurement of parity violation in the early universe using gravitational-wave detectors

S. G. Crowder, R. Namba, V. Mandic, S. Mukohyama, M. Peloso

Research output: Contribution to journalArticlepeer-review

41 Scopus citations


A stochastic gravitational-wave background (SGWB) is expected to arise from the superposition of many independent and unresolved gravitational-wave signals, of either cosmological or astrophysical origin. Some cosmological models (characterized, for instance, by a pseudo-scalar inflaton, or by some modification of gravity) break parity, leading to a polarized isotropic SGWB. We present the first upper limit on this parity violation from direct gravitational-wave measurements by measuring polarization of the SGWB in recent LIGO data and by assuming a generic power-law SGWB spectrum across the LIGO-sensitive frequency region. We also estimate sensitivity to parity violation for future generations of gravitational-wave detectors, both for a power-law spectrum and for a specific model of axion inflation. Since astrophysical sources are not expected to produce a polarized SGWB, measurements of polarization in the SGWB would provide a new way of differentiating between the cosmological and astrophysical SGWB sources.

Original languageEnglish (US)
Pages (from-to)66-71
Number of pages6
JournalPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Issue number1-3
StatePublished - 2013


  • Axion inflation
  • Gravitational-wave detector
  • Parity violation
  • Stochastic gravitational-wave background

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