Whispers from the dark side: Confronting light new physics with NANOGrav data

Ratzinger, Wolfram; Schwaller, Pedro

doi:10.21468/scipostphys.10.2.047

Cited by 101 publications

(71 citation statements)

References 41 publications

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“…Varying the ALP mass gives detectable GW signals across a vast range of frequencies, from the earth-based Einstein Telescope (ET) laser interferometer to the space-based interferometers LISA, BBO, DECIGO and µAres as well as the current and future pulsar timing arrays NANOGrav and SKA. For NANOGrav, we show the 2σ region where the model could explain the recently observed signal [52]. At even lower masses, gravitational waves from ALPs can cause spectral distortions in the CMB.…”

Section: Phenomenologysupporting

confidence: 61%

Gravitational waves from an axion-dark photon system: A lattice study

2021

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In this work, we present a lattice study of an axion - dark photon system in the early Universe and show that the stochastic gravitational wave (GW) background produced by this system may be probed by future GW experiments across a vast range of frequencies. The numerical simulation on the lattice allows us to take into account non-linear backreaction effects and enables us to accurately predict the final relic abundance of the axion or axion-like particle (ALP) as well as its inhomogeneities, and gives a more precise prediction of the GW spectrum. Importantly, we find that the GW spectrum has more power at high momenta due to 2\rightarrow12→1 processes. Furthermore, we find the degree of polarization of the peak of the GW spectrum depends on the ALP-dark photon coupling and that the polarization can be washed out or even flipped for large values thereof. In line with recent results in the literature, we find the ALP relic abundance may be suppressed by two orders of magnitude and discuss possible extensions of the model that expand the viable parameter space. Finally, we discuss the possibility to probe ultralight ALP dark matter via spectral distortions of the CMB.

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Section: Phenomenologysupporting

confidence: 61%

Gravitational waves from an axion-dark photon system: A lattice study

2021

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“…Similarly to the axion case, models featuring a cosmological phase transition in the early Universe can boost the DM power spectrum on small scales [48] and be tested by PTAs. Interestingly, if the phase transition happens at low enough temperatures (T 1 GeV), these models are also expected to generate a background of gravitational waves which could be searched for in PTAs (see for example [49]). We leave to future works a detailed study of these scenarios.…”

Section: Axions With Pq Symmetry Breaking After Inflationmentioning

confidence: 99%

Probing small-scale power spectra with pulsar timing arrays

Lee

Mitridate

Trickle

et al. 2021

J. High Energ. Phys.

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Models of Dark Matter (DM) can leave unique imprints on the Universe’s small scale structure by boosting density perturbations on small scales. We study the capability of Pulsar Timing Arrays to search for, and constrain, subhalos from such models. The models of DM we consider are ordinary adiabatic perturbations in ΛCDM, QCD axion miniclusters, models with early matter domination, and vector DM produced during inflation. We show that ΛCDM, largely due to tidal stripping effects in the Milky Way, is out of reach for PTAs. Axion miniclusters may be within reach, although this depends crucially on whether the axion relic density is dominated by the misalignment or string contribution. Models where there is matter domination with a reheat temperature below 1 GeV may be observed with future PTAs. Lastly, vector DM produced during inflation can be detected if it is lighter than 10−16 GeV. We also make publicly available a Python Monte Carlo tool for generating the PTA time delay signal from any model of DM substructure.

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“…[2][3][4]), which may be visible by planned gravitational wave experiments such as LISA [5], DECIGO [6], BBO [7] and Taiji [8]. In fact recent evidence for a possible stochastic background of gravitational waves by the NANOGrav experiment [9] has been interpreted as the gravitational wave signal of a first-order phase transition [10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

On the perturbative expansion at high temperature and implications for cosmological phase transitions

Gould

Tenkanen

2021

J. High Energ. Phys.

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We revisit the perturbative expansion at high temperature and investigate its convergence by inspecting the renormalisation scale dependence of the effective potential. Although at zero temperature the renormalisation group improved effective potential is scale independent at one-loop, we show how this breaks down at high temperature, due to the misalignment of loop and coupling expansions. Following this, we show how one can recover renormalisation scale independence at high temperature, and that it requires computations at two-loop order. We demonstrate how this resolves some of the huge theoretical uncertainties in the gravitational wave signal of first-order phase transitions, though uncertainties remain stemming from the computation of the bubble nucleation rate.

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Whispers from the dark side: Confronting light new physics with NANOGrav data

Cited by 101 publications

References 41 publications

Gravitational waves from an axion-dark photon system: A lattice study

Gravitational waves from an axion-dark photon system: A lattice study

Probing small-scale power spectra with pulsar timing arrays

On the perturbative expansion at high temperature and implications for cosmological phase transitions

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