815 research outputs found
The One-Loop Matter Bispectrum in the Effective Field Theory of Large Scale Structures
Given the importance of future large scale structure surveys for delivering
new cosmological information, it is crucial to reliably predict their
observables. The Effective Field Theory of Large Scale Structures (EFTofLSS)
provides a manifestly convergent perturbative scheme to compute the clustering
of dark matter in the weakly nonlinear regime in an expansion in , where is the wavenumber of interest and is the
wavenumber associated to the nonlinear scale. It has been recently shown that
the EFTofLSS matches to level the dark matter power spectrum at redshift
zero up to Mpc and Mpc at one
and two loops respectively, using only one counterterm that is fit to data.
Similar results have been obtained for the momentum power spectrum at one loop.
This is a remarkable improvement with respect to former analytical techniques.
Here we study the prediction for the equal-time dark matter bispectrum at one
loop. We find that at this order it is sufficient to consider the same
counterterm that was measured in the power spectrum. Without any remaining free
parameter, and in a cosmology for which is smaller than in the
previously considered cases (), we find that the prediction from
the EFTofLSS agrees very well with -body simulations up to Mpc, given the accuracy of the measurements, which is of order a few
percent at the highest 's of interest. While the fit is very good on average
up to Mpc, the fit performs slightly worse on
equilateral configurations, in agreement with expectations that for a given
maximum , equilateral triangles are the most nonlinear.Comment: 39 pages, 12 figures; v2: JCAP published version, improved numerical
data, added explanation and clarification
Lensing reconstruction from line intensity maps: the impact of gravitational nonlinearity
We investigate the detection prospects for gravitational lensing of
three-dimensional maps from upcoming line intensity surveys, focusing in
particular on the impact of gravitational nonlinearities on standard quadratic
lensing estimators. Using perturbation theory, we show that these
nonlinearities can provide a significant contaminant to lensing reconstruction,
even for observations at reionization-era redshifts. However, we show how this
contamination can be mitigated with the use of a "bias-hardened" estimator.
Along the way, we present an estimator for reconstructing long-wavelength
density modes, in the spirit of the "tidal reconstruction" technique that has
been proposed elsewhere, and discuss the dominant biases on this estimator.
After applying bias-hardening, we find that a detection of the lensing
potential power spectrum will still be challenging for the first phase of
SKA-Low, CHIME, and HIRAX, with gravitational nonlinearities decreasing the
signal to noise by a factor of a few compared to forecasts that ignore these
effects. On the other hand, cross-correlations between lensing and galaxy
clustering or cosmic shear from a large photometric survey look promising,
provided that systematics can be sufficiently controlled. We reach similar
conclusions for a single-dish survey inspired by CII measurements planned for
CCAT-prime, suggesting that lensing is an interesting science target not just
for 21cm surveys, but also for intensity maps of other lines.Comment: 40+18 pages, 13 figures, 5 tables. v2: JCAP published version, with
typos fixed and clarifications adde
What do gas-rich galaxies actually tell us about modified Newtonian dynamics?
It has recently been claimed that measurements of the baryonic Tully-Fisher
relation (BTFR), a power-law relationship between the observed baryonic masses
and outer rotation velocities of galaxies, support the predictions of modified
Newtonian dynamics for the slope and scatter in the relation, while challenging
the cold dark matter (CDM) paradigm. We investigate these claims, and find
that: 1) the scatter in the data used to determine the BTFR is in conflict with
observational uncertainties on the data; 2) these data do not make strong
distinctions regarding the best-fit BTFR parameters; 3) the literature contains
a wide variety of measurements of the BTFR, many of which are discrepant with
the recent results; and 4) the claimed CDM "prediction" for the BTFR is a gross
oversimplification of the complex galaxy-scale physics involved. We conclude
that the BTFR is currently untrustworthy as a test of CDM.Comment: 5 pages, 2 figures; minor revisions to match published versio
Gratuitous violence and the rational offender model
Rational offender models assume that individuals choose whether to offend by weighing the rewards against the chances of apprehension and the penalty if caught. While evidence indicates that rational theory is applicable to acquisitive crimes, the explanatory power for gratuitous non-fatal violent offending has not been evaluated. Lottery-type questions elicited risk attitudes and time preferences from respondents in a street survey. Admitted violent behaviour was predictable on the basis of some of these responses. Consistent with the rational model, less risk averse and more impatient individuals were more liable to violence. Such people were also more likely to be victims of violence. In line with a ‘subjective’ version of the rational model, respondents with lower estimates of average violence conviction chances and of fines were more prone to be violent
Removing systematic errors for exoplanet search via latent causes
We describe a method for removing the effect of confounders in order to
reconstruct a latent quantity of interest. The method, referred to as
half-sibling regression, is inspired by recent work in causal inference using
additive noise models. We provide a theoretical justification and illustrate
the potential of the method in a challenging astronomy application.Comment: Extended version of a paper appearing in the Proceedings of the 32nd
International Conference on Machine Learning, Lille, France, 201
Baryonic effects on the matter bispectrum
The large-scale clustering of matter is impacted by baryonic physics,
particularly AGN feedback. Modelling or mitigating this impact will be
essential for making full use of upcoming measurements of cosmic shear and
other large-scale structure probes. We study baryonic effects on the matter
bispectrum, using measurements from a selection of state-of-the-art
hydrodynamical simulations: IllustrisTNG, Illustris, EAGLE, and BAHAMAS. We
identify a low-redshift enhancement of the bispectrum, peaking at , that is present in several simulations, and discuss how it
can be associated to the evolving nature of AGN feedback at late times. This
enhancement does not appear in the matter power spectrum, and therefore
represents a new source of degeneracy breaking between two- and three-point
statistics. In addition, we provide physical interpretations for other aspects
of these measurements, and make initial comparisons to predictions from
perturbation theory, empirical fitting formulas, and the response function
formalism. We publicly release our measurements (including estimates of their
uncertainty due to sample variance) and bispectrum measurement code as
resources for the community.Comment: 29 pages, 24 figures. v2: MNRAS published version, with references
and clarifications added (conclusions unchanged). See Fig. 13 for a summary
of the main results. Simulation measurements are available at
https://github.com/sjforeman/hydro_bispectrum , and bispectrum measurement
code is available at https://github.com/sjforeman/bski
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