Probing early-universe phase transitions with CMB spectral distortions

Amin, Mustafa A.; Grin, Daniel

doi:10.1103/physrevd.90.083529

Cited by 14 publications

(15 citation statements)

References 101 publications

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“…Cosmic defects also exhibit other potentially observable effects: non-Gaussianity [88][89][90] and spectral distortions [91] in the CMB, lensing events [92,93], and cosmic rays from the decay of strings into particle radiation [94][95][96][97][98][99][100][101][102][103]. In the case of Nambu-Goto strings, a stochastic background of GWs is expected from the oscillations of the resulting loops, chopped off from the main string network through cosmic history [73,[78][79][80][104][105][106][107][108][109][110][111].…”

Section: Introductionmentioning

confidence: 99%

Irreducible background of gravitational waves from a cosmic defect network: Update and comparison of numerical techniques

et al. 2020

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Cosmological phase transitions in the early Universe may produce relics in the form of a network of cosmic defects. Independently of the order of a phase transition, topology of the defects, and their global or gauge nature, the defects are expected to emit gravitational waves (GWs) as the network energymomentum tensor adapts itself to maintaining scaling. We show that the evolution of any defect network (and for that matter any scaling source) emits a GW background with spectrumand Ω GW ∝ const (i.e., exactly scale invariant) for f ≫ f eq , where f 0 and f eq denote respectively the frequencies corresponding to the present and matter-radiation equality horizons. This background represents an irreducible emission of GWs from any scaling network of cosmic defects, with its amplitude characterized only by the symmetry-breaking scale and the nature of the defects. Using classical lattice simulations we calculate the GW signal emitted by defects created after the breaking of a global symmetry OðNÞ → OðN − 1Þ. We obtain the GW spectrum for N between 2 and 20 with two different techniques: integrating over unequal-time correlators of the energy-momentum tensor, updating our previous work on smaller lattices, and for the first time, comparing the result with the real-time evolution of the tensor perturbations sourced by the same defects. Our results validate the equivalence of the two techniques. Using cosmic microwave background upper bounds on the defects' energy scale, we discuss the difficulty of detecting this GW background in the case of global defects.

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Section: Introductionmentioning

confidence: 99%

Irreducible background of gravitational waves from a cosmic defect network: Update and comparison of numerical techniques

et al. 2020

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“…If more small-scale perturbations are present in different directions, an anisotropic distortion could be created, allowing us to probe scale-dependent non-Gaussianity in the ultra-squeezed limit [451][452][453][454] or possibly cosmic bubble collisions [397]. Finally, also tensor and vector modes lead to dissipation; however, unless a very blue power spectrum is realised, the associated distortion signals should be sub-dominant [455][456][457].…”

Section: Damping Of Small-scale Acoustic Modesmentioning

confidence: 99%

Features and new physical scales in primordial observables: Theory and observation

Chluba

Hamann

Patil

2015

Int. J. Mod. Phys. D

212

233

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June 22, 20152 All cosmological observations to date are consistent with adiabatic, Gaussian and nearly scale invariant initial conditions. These findings provide strong evidence for a particular symmetry breaking pattern in the very early universe (with a close to vanishing order parameter, ), widely accepted as conforming to the predictions of the simplest realizations of the inflationary paradigm. However, given that our observations are only privy to perturbations, in inferring something about the background that gave rise to them, it should be clear that many different underlying constructions project onto the same set of cosmological observables. Features in the primordial correlation functions, if present, would offer a unique and discriminating window onto the parent theory in which the mechanism that generated the initial conditions is embedded. In certain contexts, simple linear response theory allows us to infer new characteristic scales from the presence of features that can break the aforementioned degeneracies among different background models, and in some cases can even offer a limited spectroscopy of the heavier degrees of freedom that couple to the inflaton. In this review, we offer a pedagogical survey of the diverse, theoretically well grounded mechanisms which can imprint features into primordial correlation functions in addition to reviewing the techniques one can employ to probe observations. These observations include cosmic microwave background anisotropies and spectral distortions as well as the matter two and three point functions as inferred from large-scale structure and potentially, 21 cm surveys.

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“…Moving forward, while here we focused on the GW-induced SDs, the limits could be made even more compelling by considering the signals arising from both the tensor and scalar perturbations that energetic events could produce (e.g., Tashiro et al 2013;Amin & Grin 2014, for SDs from scalar perturbations of CS and PTs, respectively). This potential for combining sources is another advantage SD experiments have over GW-based experiments, since the latter are only sensitive to the direct tensor perturbations.…”

Section: Discussionmentioning

confidence: 99%

Bridging the gap: spectral distortions meet gravitational waves

Kite,

Ravenni,

Patil

et al. 2020

Preprint

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Gravitational waves (GWs) have the potential to probe the entirety of cosmological history due to their nearly perfect decoupling from the thermal bath and any intervening matter after emission. In recent years, GW cosmology has evolved from merely being an exciting prospect to an actively pursued avenue for discovery, and the early results are very promising. As we highlight in this paper, spectral distortions (SDs) of the cosmic microwave background (CMB) uniquely probe GWs over six decades in frequency, bridging the gap between astrophysical high-and cosmological low-frequency measurements. This means SDs will not only complement other GW observations, but will be the sole probe of physical processes at certain scales. To illustrate this point, we explore the constraining power of various proposed SD missions on a number of phenomenological scenarios: early-universe phase transitions (PTs), GW production via the dynamics of SU(2) and ultra-light U(1) axions, and cosmic string (CS) network collapse. We highlight how some regions of parameter space were already excluded with data from COBE/FIRAS, taken over two decades ago. To facilitate the implementation of SD constraints in arbitrary models we provide GW2SD. This tool calculates the window function, which easily maps a GW spectrum to a SD amplitude, thus opening another portal for GW cosmology with SDs, with wide reaching implications for particle physics phenomenology.

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Probing early-universe phase transitions with CMB spectral distortions

Cited by 14 publications

References 101 publications

Irreducible background of gravitational waves from a cosmic defect network: Update and comparison of numerical techniques

Irreducible background of gravitational waves from a cosmic defect network: Update and comparison of numerical techniques

Features and new physical scales in primordial observables: Theory and observation

Bridging the gap: spectral distortions meet gravitational waves

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