The Spectrum of Gravitational Waves from Annihilating Domain Walls

Abstract

Networks of cosmic domain walls can form in the early Universe as a consequence of the spontaneous breaking of discrete symmetries. We study the production of a cosmological background of gravitational waves (GWs) from such networks, when they annihilate due to a small explicit symmetry breaking term. Averaging over several 3+1-dimensional high-resolution lattice field simulations, we obtain a GW spectrum with the following characteristics: (1) a broad asymmetric peak, roughly located at frequency (at the time of emission) $f\sim 2H_{\mathrm{gw}}$, where $H_{\mathrm{gw}}$ is the Hubble rate at the end of GW production, shortly after annihilation, (2) a doubly broken power law spectrum $\propto k^{-n}$, with initial slope $n\sim 0.5$ after the main peak and $n\sim 1.8$ at high $f$, while the low frequency region $f<f_p$ agrees with the causality behavior $\sim k^3$. Additionally, extending previous results, we find that GW production continues to be efficient until a value of the Hubble scale $H_{\text{g}w}$ that is roughly an order of magnitude smaller than the naive estimate $\sigma H=\Delta V$, where $\sigma$ is the wall tension and $\Delta V$ the size of the symmetry breaking term, thereby leading to a $O(100)$ larger GW signal. We find such results to be robust when changing the shape of the scalar field potential or including a time-dependent symmetry breaking term. Our findings have important implications for GW searches, especially in light of the reported evidence for a stochastic GW background in Pulsar Timing Array data.

arXiv comment16 pages + appendices, 20 figures. It includes new results on scalar spectra for different bias sizes. It matches version published in JCAP

References in corpus (36)

• The NANOGrav 15-year Data Set: Evidence for a Gravitational-Wave Background
• Search for an isotropic gravitational-wave background with the Parkes Pulsar Timing Array
• Searching for the nano-Hertz stochastic gravitational wave background with the Chinese Pulsar Timing Array Data Release I
• The second data release from the European Pulsar Timing Array III. Search for gravitational wave signals
• The NANOGrav 15-year Data Set: Search for Signals from New Physics
• Detecting gravitational waves from cosmological phase transitions with LISA: an update
• Cosmology with the Laser Interferometer Space Antenna
• General Properties of the Gravitational Wave Spectrum from Phase Transitions
• Axion dark matter from topological defects
• Universal infrared scaling of gravitational wave background spectra
• On the estimation of gravitational wave spectrum from cosmic domain walls
• A review of gravitational waves from cosmic domain walls
• Evading the cosmological domain wall problem
• Studies of the motion and decay of axion walls bounded by strings
• Axion cosmology with long-lived domain walls
• Electroweak Baryogenesis in Non-minimal Composite Higgs Models
• The art of simulating the early Universe -- Part I
• CosmoLattice
• Gravitational Waves from Domain Walls in Pulsar Timing Array Datasets
• Gravitational Waves from Collapsing Vacuum Domains
• Stability of domain wall network with initial inflationary fluctuations, and its implications for cosmic birefringence
• NANOGrav spectral index $\gamma =3$ from melting domain walls
• Domain walls seeding the electroweak phase transition
• Beyond freeze-in: Dark Matter via inverse phase transition and gravitational wave signal
• High Quality QCD Axion at Gravitational Wave Observatories
• Effects of Biases in Domain Wall Network Evolution
• Revisiting evolution of domain walls and their gravitational radiation with CosmoLattice
• Effects of biases in domain wall network evolution. II. Quantitative analysis
• CLUSTEREASY: A Program for Simulating Scalar Field Evolution on Parallel Computers
• Domain wall annihilation -- a QFT perspective
• Implications for Cosmic Domain Walls from LIGO-Virgo First Three Observing Runs
• Stability of domain walls with inflationary fluctuations under potential bias, and gravitational wave signatures
• Dynamics of Long-lived Axion Domain Walls and Its Cosmological Implications
• Near-Peak Spectrum of Gravitational Waves from Collapsing Domain Walls
• Biased domain walls: faster annihilation, weaker gravitational waves
• More accurate gravitational wave backgrounds from cosmic strings

Cited by in corpus (2)

• The Science of the Einstein Telescope
• Biased Domain Walls and the Origin of Early Massive Structures