Non-Gaussianity from cosmic magnetic fields

Brown, Iain A.; Crittenden, Robert

doi:10.1103/physrevd.72.063002

Cited by 85 publications

(118 citation statements)

References 60 publications

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“…This has been calculated in [1,4,6,18], and it shares the same k-dependence as the spectral amplitude of the magnetic field energy density Ω B . For a causal magnetic field with n ≥ 2 it is simply constant in k up to the damping scale k D , which we assume time-independent.…”

Section: Jhep00(2010)000mentioning

confidence: 90%

CMB temperature anisotropy at large scales induced by a causal primordial magnetic field

Bonvin¹,

Caprini²

2010

J. Cosmol. Astropart. Phys.

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We present an analytical derivation of the Sachs Wolfe effect sourced by a primordial magnetic field. In order to consistently specify the initial conditions, we assume that the magnetic field is generated by a causal process, namely a first order phase transition in the early universe. As for the topological defects case, we apply the general relativistic junction conditions to match the perturbation variables before and after the phase transition which generates the magnetic field, in such a way that the total energy momentum tensor is conserved across the transition and Einstein's equations are satisfied. We further solve the evolution equations for the metric and fluid perturbations at large scales analytically including neutrinos, and derive the magnetic Sachs Wolfe effect. We find that the relevant contribution to the magnetic Sachs Wolfe effect comes from the metric perturbations at next-to-leading order in the large scale limit. The leading order term is in fact strongly suppressed due to the presence of free-streaming neutrinos. We derive the neutrino compensation effect dynamically and confirm that the magnetic Sachs Wolfe spectrum from a causal magnetic field behaves as ℓ(ℓ + 1) C B ℓ ∝ ℓ 2 as found in the latest numerical analyses.c SISSA/ISAS 2018

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Section: Jhep00(2010)000mentioning

confidence: 90%

CMB temperature anisotropy at large scales induced by a causal primordial magnetic field

Bonvin¹,

Caprini²

2010

J. Cosmol. Astropart. Phys.

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“…While the majority of the studies on primordial and CMB NG focus on the scalar mode, tensor-mode NG has been attracting attention as a probe of high-energy theories of gravity (e.g., Maldacena & Pimentel 2011;McFadden & Skenderis 2011;Soda et al 2011;Shiraishi et al 2011;Gao et al 2011) or primordial magnetic fields (Brown & Crittenden 2005;Shiraishi et al 2012;Shiraishi 2012) 5 . Recently, the possibility of observable tensor bispectra has been vigorously discussed in a model where the inflaton couples to a pseudoscalar field (Barnaby et al 2012a;Cook & Sorbo 2013;Ferreira & Sloth 2014).…”

Section: Parity-violating Tensor Non-gaussianity Motivated By Pseudo-mentioning

confidence: 99%

Planck2015 results

Ade

Aghanim

Arnaud

et al. 2016

A&A

477

256

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The Planck full mission cosmic microwave background (CMB) temperature and E-mode polarization maps are analysed to obtain constraints on primordial non-Gaussianity (NG). Using three classes of optimal bispectrum estimators -separable template-fitting (KSW), binned, and modalwe obtain consistent values for the primordial local, equilateral, and orthogonal bispectrum amplitudes, quoting as our final result from temperature alone f local NL = 2.5 ± 5.7, f equil NL = −16 ± 70, and f ortho NL = −34 ± 33 (68% CL, statistical). Combining temperature and polarization data we obtain f local NL = 0.8 ± 5.0, f equil NL = −4 ± 43, and f ortho NL = −26 ± 21 (68% CL, statistical). The results are based on comprehensive cross-validation of these estimators on Gaussian and non-Gaussian simulations, are stable across component separation techniques, pass an extensive suite of tests, and are consistent with estimators based on measuring the Minkowski functionals of the CMB. The effect of time-domain de-glitching systematics on the bispectrum is negligible. In spite of these test outcomes we conservatively label the results including polarization data as preliminary, owing to a known mismatch of the noise model in simulations and the data. Beyond estimates of individual shape amplitudes, we present model-independent, three-dimensional reconstructions of the Planck CMB bispectrum and derive constraints on early universe scenarios that generate primordial NG, including general single-field models of inflation, axion inflation, initial state modifications, models producing parityviolating tensor bispectra, and directionally dependent vector models. We present a wide survey of scale-dependent feature and resonance models, accounting for the "look elsewhere" effect in estimating the statistical significance of features. We also look for isocurvature NG, and find no signal, but we obtain constraints that improve significantly with the inclusion of polarization. The primordial trispectrum amplitude in the local model is constrained to be g local NL = (−9.0 ± 7.7) × 10 4 (68% CL statistical), and we perform an analysis of trispectrum shapes beyond the local case. The global picture that emerges is one of consistency with the premises of the ΛCDM cosmology, namely that the structure we observe today was sourced by adiabatic, passive, Gaussian, and primordial seed perturbations.

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“…In this case the only non-zero correlations between multipole coefficients are between those that have ∆l = 0 and ∆l = ±2, and ∆m = 0, ∆m = ±1, and ∆m = ±2, and we have accounted for all non-zero correlations. Even though we have computed only the two-point correlation function, such off-diagonal correlations indicate that in this model the CMB temperature anisotropy is non-gaussian [31]. Such an homogeneous magnetic field might explain the tentative large-scale non-gaussianity of the CMB temperature anisotropy (also see Refs.…”

Section: Discussionmentioning

confidence: 99%