Number counts and non-Gaussianity

Shandera, Sarah; Erickcek, Adrienne L.; Scott, Pat; Galarza, Jhon Yana

doi:10.1103/physrevd.88.103506

Cited by 44 publications

(70 citation statements)

References 100 publications

(187 reference statements)

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“…It is in any case interesting to ask how the dark matter substructure would change if the initial small scale perturbations were larger than expected. Other papers which constrain the power spectrum on small scales include [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35]. In particular, we note that CMB spectral distortion constraints provide an upper bound on the primordial power spectrum on about the same scales as UCMHs, which are about an order of magnitude weaker than the currently claimed constraints but independent of the DM model [20].…”

Section: Introductionmentioning

confidence: 67%

3D simulations with boosted primordial power spectra and ultracompact minihalos

et al. 2017

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We perform three-dimensional simulations of structure formation in the early Universe, when boosting the primordial power spectrum on ∼kpc scales. We demonstrate that our simulations are capable of producing power-law profiles close to the steep ρ ∝ r −9=4 halo profiles that are commonly assumed to be a good approximation to ultracompact minihalos (UCMHs). However, we show that for more realistic initial conditions in which halos are neither perfectly symmetric nor isolated the steep power-law profile is disrupted, and we find that the Navarro-Frenk-White profile is a better fit to most halos. In the presence of background fluctuations, even extreme, nearly spherical initial conditions do not remain exceptional. Nonetheless, boosting the amplitude of initial fluctuations causes all structures to form earlier and thus at larger densities. With a sufficiently large amplitude of fluctuations, we find that values for the concentration of typical halos in our simulations can become very large. However, despite the signal coming from dark matter annihilation inside the cores of these halos being enhanced, it is still orders of magnitude smaller compared to the usually assumed UCMH profile. The upper bound on the primordial power spectrum from the nonobservation of UCMHs should therefore be reevaluated.

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Section: Introductionmentioning

confidence: 67%

3D simulations with boosted primordial power spectra and ultracompact minihalos

et al. 2017

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“…Full consideration of this will require consideration of the the shape of the small-scale power spectrum, typical profile shapes and the shape of the bispectrum, amongst other factors, and goes beyond the scope of this paper. However, much work has been completed on this topic in the past [15,[19][20][21][22][23][24][25]27], and a more complete analysis using the methods presented in this paper would yield qualitatively similar results. We have also only considered an expansion to second order in local-type non-Gaussianity, although it has been shown that higher-order terms can also be important [21].…”

Section: The Primordial Black Hole Merger Ratementioning

confidence: 78%

Initial clustering and the primordial black hole merger rate

Young

Byrnes²

2020

J. Cosmol. Astropart. Phys.

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If the primordial curvature perturbation followed a Gaussian distribution, primordial black holes (PBHs) will be Poisson distributed with no additional clustering. We consider local non-Gaussianity and its impact on the initial PBH clustering and mass function due to mode coupling between long and short wavelength modes. We show that even a small amount of non-Gaussianity results in a significant enhancement on the PBH initial clustering and subsequent merger rate and that the PBH mass function shifts to higher mass PBHs.However, as the clustering becomes strong, the local number density of PBHs becomes large, leading to a large theoretical uncertainty in the merger rate.

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“…significantly affect the tails of the distribution [103]. The influence of the peak population on the power spectrum constraint is encoded in the moments I 3/2 , J 3/2 , I 1 , and J 1 of the peak distribution.…”

Section: Discussionmentioning

confidence: 99%

Density profiles of ultracompact minihalos: Implications for constraining the primordial power spectrum

et al. 2018

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Enhanced density fluctuations on small scales would lead to the formation of numerous dark matter minihalos, so limits on the minihalo abundance can place upper bounds on the small-scale primordial power spectrum. In particular, the ultracompact minihalo (UCMH), a dark matter structure hypothesized to possess a ρ ∝ r −9/4 density profile due to its formation at z ≥ 1000, has been used to establish an upper bound on the primordial power spectrum at scales smaller than 2 Mpc. The extreme slope of this density profile amplifies the observational signals of UCMHs. However, we recently showed via N-body simulations that the ρ ∝ r −9/4 density profile does not develop in realistic formation scenarios, throwing UCMH-derived power spectrum constraints into question. Instead, minihalos develop shallower inner profiles with power-law indices between −3/2 and −1. In this paper, we expand on that result and discuss its implications. Using a model that is calibrated to simulation results and predicts halo structures in spiked power spectra based on their formation times, we calculate new upper bounds on the primordial power spectrum based on limits on the dark matter annihilation rate within the Galaxy. We find that despite assuming shallower profiles, this minihalo model actually yields stronger constraints than the previous UCMH picture owing to its inclusion of all minihalos instead of only the earliest-forming ones.

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Number counts and non-Gaussianity

Cited by 44 publications

References 100 publications

3D simulations with boosted primordial power spectra and ultracompact minihalos

3D simulations with boosted primordial power spectra and ultracompact minihalos

Initial clustering and the primordial black hole merger rate

Density profiles of ultracompact minihalos: Implications for constraining the primordial power spectrum

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