Bispectrum of galaxies from high-redshift galaxy surveys: Primordial non-Gaussianity and nonlinear galaxy bias

Sefusatti, Emiliano; Komatsu, Eiichiro

doi:10.1103/physrevd.76.083004

Cited by 228 publications

(327 citation statements)

References 66 publications

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“…To put forth a concrete example, limits on inflationary non-Gaussianities of the equilateral [27] or orthogonal [28] kind, assuming a cosmic variance limited experiment and assuming the same scaling as in the linear regime, go as k −3/2 max . Preliminary forecasts for these parameters for the Euclid survey [29], using k max 0.1 h Mpc −1 at redshift z = 0, give constraints of order ∆f equal,ortho NL ∼ 10, which is about a factor of 7 improvement from the Planck's limits [30]. If we naively rescale as stated the above limits by the k max that we find in this paper for the dark matter clustering, we find ∆f equil., ortho.…”

Section: Discussionmentioning

confidence: 99%

The Effective Field Theory of Large Scale Structures at two loops

Carrasco

Foreman

Green

et al. 2014

J. Cosmol. Astropart. Phys.

203

499

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Large scale structure surveys promise to be the next leading probe of cosmological information. It is therefore crucial to reliably predict their observables. The Effective Field Theory of Large Scale Structures (EFTofLSS) provides a manifestly convergent perturbation theory for the weakly non-linear regime of dark matter, where correlation functions are computed in an expansion of the wavenumber k of a mode over the wavenumber associated with the non-linear scale k NL . Since most of the information is contained at high wavenumbers, it is necessary to compute higher order corrections to correlation functions. After the one-loop correction to the matter power spectrum, we estimate that the next leading one is the two-loop contribution, which we compute here. At this order in k/k NL , there is only one counterterm in the EFTofLSS that must be included, though this term contributes both at tree-level and in several one-loop diagrams. We also discuss correlation functions involving the velocity and momentum fields. We find that the EFTofLSS prediction at two loops matches to percent accuracy the non-linear matter power spectrum at redshift zero up to k ∼ 0.6 h Mpc −1 , requiring just one unknown coefficient that needs to be fit to observations. Given that Standard Perturbation Theory stops converging at redshift zero at k ∼ 0.1 h Mpc −1 , our results demonstrate the possibility of accessing a factor of order 200 more dark matter quasi-linear modes than naively expected. If the remaining observational challenges to accessing these modes can be addressed with similar success, our results show that there is tremendous potential for large scale structure surveys to explore the primordial universe.

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Section: Discussionmentioning

confidence: 99%

The Effective Field Theory of Large Scale Structures at two loops

Carrasco

Foreman

Green

et al. 2014

J. Cosmol. Astropart. Phys.

203

499

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show abstract

“…However, to constrain the possible non-Gaussianities of the initial perturbations, to check the gravitational clustering scenario (through the measure of the non-Gaussianities generated by the nonlinear dynamics), and to break parameter degeneracies, it is useful to study higher order statistics. The three-point correlation function or bispectrum in Fourier space, which is the lowest order statistics beyond the Gaussian, is the main quantity studied in this context (Peebles 1980;Frieman & Gaztanaga 1994, 1999Scoccimarro & Couchman 2001;Bernardeau et al 2002b;Verde et al 2002;Takada & Jain 2003;Kayo et al 2004;Sefusatti & Komatsu 2007;Nishimichi et al 2007;Sefusatti et al 2010;Nishimichi et al 2010). …”

Section: Introductionmentioning

confidence: 99%

Combining perturbation theories with halo models for the matter bispectrum

Valageas

Nishimichi

2011

A&A

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Aims. We investigate how unified models should be built to be able to predict the matter-density bispectrum (and power spectrum) from very large to small scales and that are at the same time consistent with perturbation theory at low k and with halo models at high k. Methods. We use a Lagrangian framework to decompose the bispectrum into "3-halo", "2-halo", and "1-halo" contributions, related to "perturbative" and "non-perturbative" terms. We describe a simple implementation of this approach and present a detailed comparison with numerical simulations. Results. We show that the 1-halo and 2-halo contributions contain counterterms that ensure their decay at low k, as required by physical constraints, and allow a better match to simulations. Contrary to the power spectrum, the standard 1-loop perturbation theory can be used for the perturbative 3-halo contribution because it does not grow too fast at high k. Moreover, it is much simpler and more accurate than two resummation schemes investigated in this paper. We obtain a good agreement with numerical simulations on both large and small scales, but the transition scales are poorly described by the simplest implementation. This cannot be amended by simple modifications to the halo parameters, but we show how it can be corrected for the power spectrum and the bispectrum through a simple interpolation scheme that is restricted to this intermediate regime. Then, we reach an accuracy on the order of 10% on mildly and highly nonlinear scales, while an accuracy on the order of 1% is obtained on larger weakly nonlinear scales. This also holds for the real-space two-point correlation function.

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“…Qualitatively, a sharp reflection leads to a drastic diminution in the entropy perturbation and a much smaller value of the above integral, while a smooth and more gradual reflection results in an enhanced efficiency of conversion. The leading non-gaussianity is generated when modes are outside the horizon, so the non-gaussianity is of the local, wavelength-independent type [13,21,22]. The nonlinearity parameter f N L is then defined by the relations [13…”

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confidence: 99%

Erratum: Non-Gaussian density fluctuations from entropically generated curvature perturbations in ekpyrotic models [Phys. Rev. D77, 063533 (2008)]

Lehners¹,

Steinhardt²

2009

Phys. Rev. D

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We analyze the non-gaussian density perturbations generated in ekpyrotic/cyclic models based on heterotic M-theory. In this picture, two scalar fields produce nearly scale-invariant entropic perturbations during an ekpyrotic phase that are converted into curvature modes after the ekpyrotic phase is complete and just before the big bang. Both intrinsic non-linearity in the entropy perturbation and the conversion process contribute to non-gaussianity. The range of the non-gaussianity parameter fNL depends on the details of the scalar field potential during the ekpyrotic phase, and on how gradual the conversion process is. Although a wider range is possible, in principle, natural values of the parameters of the potential combined with a gradual conversion process lead to values of −60 fNL +80, typically much greater than slow-roll inflation but within the current observational bounds.Ekpyrotic [1] and cyclic [2] models of the universe use quantum fluctuations of scalar fields produced during a slowly contracting phase with equation of state w > 1 to generate the observed nearly scale-invariant spectrum of curvature (energy density) fluctuations after the big bang. One mechanism considered for converting the fluctuations of a scalar field into cosmological curvature perturbations relies on higher-dimensional effects at the collision between orbifold planes (branes) along an extra dimension [3]. Recently, however, a new "entropic" mechanism [4,5] has been proposed that relies on two (or more) scalar fields and ordinary 4d physics, stimulating new approaches to ekpyrotic and cyclic cosmology that may not require branes or extra dimensions at all [6][7][8][9].In this paper, we wish to consider an important byproduct of the entropic mechanism: a non-gaussian contribution to the density fluctuation spectrum that is more than an order of magnitude greater than for conventional inflationary models and that can satisfy current observational bounds, including the recently claimed detection of non-gaussianity [10]. Our results differ significantly from the cases considered by Koyama et al. [11] and Buchbinder et al. [12] in which they assumed an ekpyrotic (w ≫ 1) phase that continues all the way to the conversion of entropic to curvature fluctuations, as in the "new ekpyrotic" model [6]; for these cases, the non-gaussianity is amplified by the non-linear evolution on super-horizon scales to the point where f N L , the parameter characterizing the non-linear curvature perturbation [13], reaches magnitude O(c 2 1 ), where c 1 ≈ 2 √ w + 1 parameterizes the steepness of the scalar field potential during the ekpyrotic phase. A potential problem is that a minimum of c 1 ≥ 10 is required just to satisfy the current upper bound constraints on n s , the spectral tilt of the scalar (energy density) perturbation spectrum [5]; and c 1 ≥ 30 is needed to reach the best-fit value n s ≈ 0.97. Yet, excluding finelytuned cancellations, the resulting value of f N L obtained in Ref. [6][7][8][9] is marginally consistent with current observationa...

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Bispectrum of galaxies from high-redshift galaxy surveys: Primordial non-Gaussianity and nonlinear galaxy bias

Cited by 228 publications

References 66 publications

The Effective Field Theory of Large Scale Structures at two loops

The Effective Field Theory of Large Scale Structures at two loops

Combining perturbation theories with halo models for the matter bispectrum

Erratum: Non-Gaussian density fluctuations from entropically generated curvature perturbations in ekpyrotic models [Phys. Rev. D77, 063533 (2008)]

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