Anisotropy in solid inflation

Bartolo, N.; Matarrese, S.; Peloso, Marco; Ricciardone, Angelo

doi:10.1088/1475-7516/2013/08/022

Cited by 106 publications

(155 citation statements)

References 129 publications

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“…The I 2 (ϕ)F 2 models predict c 2 = c 0 /2, while primordial curvature perturbations sourced by large-scale magnetic fields generate non-vanishing c 0 , c 1 , and c 2 . Quite interestingly, in the proposed "solid inflation" scenario (Endlich et al 2013(Endlich et al , 2014; see also Bartolo et al 2013bBartolo et al , 2014Sitwell & Sigurdson 2014) bispectra similar to Eq. (23) can be generated, in this case with c 2 c 0 (Endlich et al 2013(Endlich et al , 2014.…”

Section: Directional-dependence Motivated By Gauge Fieldsmentioning

confidence: 88%

Planck2015 results

Ade

Aghanim

Arnaud

et al. 2016

A&A

473

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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Section: Directional-dependence Motivated By Gauge Fieldsmentioning

confidence: 88%

Planck2015 results

Ade

Aghanim

Arnaud

et al. 2016

A&A

473

256

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“…In fact, any non-Gaussianity in the form of a non-zero bispectrum will produce a correlation between a pair of modes [508,509], which implies a breaking of (statistical) translational invariance [510], and consequently of parity. This idea has been explored in [511], where it was shown that a sufficiently divergent bispectrum in the squeezed limit will couple smaller CMB modes, producing a power asymmetry in the CMB.…”

Section: Anomaly Detection: a How-to Guidementioning

confidence: 99%

“…is completely different to the physics behind the statistical anisotropy (e.g. anisotropic spacetimes [512], higher-spin (than scalar) fields [509], primordial domain walls [513], anisotropic dark energy and so on), an in-depth understanding of the physics behind the anomalies is mandatory.…”

Section: Anomaly Detection: a How-to Guidementioning

confidence: 99%

BeyondΛCDM: Problems, solutions, and the road ahead

Bull

Akrami

Adamek

et al. 2016

Physics of the Dark Universe

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210

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Despite its continued observational successes, there is a persistent (and growing) interest in extending cosmology beyond the standard model, ΛCDM. This is motivated by a range of apparently serious theoretical issues, involving such questions as the cosmological constant problem, the particle nature of dark matter, the validity of general relativity on large scales, the existence of anomalies in the CMB and on small scales, and the predictivity and testability of the inflationary paradigm. In this paper, we summarize the current status of ΛCDM as a physical theory, and review investigations into possible alternatives along a number of different lines, with a particular focus on highlighting the most promising directions. While the fundamental problems are proving reluctant to yield, the study of alternative cosmologies has led to considerable progress, with much more to come if hopes about forthcoming high-precision observations and new theoretical ideas are fulfilled.Keywords: cosmology -dark energy -cosmological constant problem -modified gravitydark matter -early universe Cosmology has been both blessed and cursed by the establishment of a standard model: ΛCDM. On the one hand, the model has turned out to be extremely predictive, explanatory, and observationally robust, providing us with a substantial understanding of the formation of large-scale structure, the state of the early Universe, and the cosmic abundance of different types of matter and energy. It has also survived an impressive battery of precision observational tests -anomalies are few and far between, and their significance is contentious where they do arise -and its predictions are continually being vindicated through the discovery of new effects (B-mode polarization [1] and lensing [2,3] of the cosmic microwave background (CMB), and the kinetic Sunyaev-Zel'dovich effect [4] being some recent examples). These are the hallmarks of a good and valuable physical theory.On the other hand, the model suffers from profound theoretical difficulties. The two largest contributions to the energy content at late times -cold dark matter (CDM) and the cosmological constant (Λ) -have entirely mysterious physical origins. CDM has so far evaded direct detection by laboratory experiments, and so the particle field responsible for it -presumably a manifestation of "beyond the standard model" particle physics -is unknown. Curious discrepancies also appear to exist between the predicted clustering properties of CDM on small scales and observations. The cosmological constant is even more puzzling, giving rise to quite simply the biggest problem in all of fundamental physics: the question of why Λ appears to take such an unnatural value [5,6,7]. Inflation, the theory of the very early Universe, has also been criticized for being fine-tuned and under-predictive [8], and appears to leave many problems either unsolved or fundamentally unresolvable. These problems are indicative of a crisis.From January 14th-17th 2015, we held a conference in Oslo, Norway to surve...

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“…for any of the components of the Riemann tensor and of the vector, it is possible to obtain (21) and prove that the mean value of the energy-momentum tensor is isotropic. Thus, if oscillations are fast compared to the curvature scale, the average energy-momentum tensor takes the perfect fluid form for any locally inertial observer.…”

Section: Isotropy Theorem For Yang-mills Theories In a General Bacmentioning

confidence: 99%

Isotropy theorem for cosmological Yang-Mills theories

2013

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We consider homogeneous non-abelian vector fields with general potential terms in an expanding universe. We find a mechanical analogy with a system of N interacting particles (with N the dimension of the gauge group) moving in three dimensions under the action of a central potential. In the case of bounded and rapid evolution compared to the rate of expansion, we show by making use of a generalization of the virial theorem that for arbitrary potential and polarization pattern, the average energy-momentum tensor is always diagonal and isotropic despite the intrinsic anisotropic evolution of the vector field. We consider also the case in which a gauge-fixing term is introduced in the action and show that the average equation of state does not depend on such a term. Finally, we extend the results to arbitrary background geometries and show that the average energy-momentum tensor of a rapidly evolving Yang-Mills fields is always isotropic and has the perfect fluid form for any locally inertial observer.

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Anisotropy in solid inflation

Cited by 106 publications

References 129 publications

Planck2015 results

Planck2015 results

BeyondΛCDM: Problems, solutions, and the road ahead

Isotropy theorem for cosmological Yang-Mills theories

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