17–23 oct. 2021
Village La Fayette - La Rochelle
Fuseau horaire Europe/Paris

Accuracy of Power Spectrum measurements using Scale-Free cosmologies

20 oct. 2021, 14:00
23m
Village La Fayette - La Rochelle

Village La Fayette - La Rochelle

Avenue de Bourgogne, 17041 La Rochelle, France http://www.seminaire-conference-la-rochelle.org https://goo.gl/maps/c2X8hqd9maRShkCm8 The centre is located at about 5 km from the La Rochelle train station (Gare de La Rochelle) and at about 5 km from the La Rochelle airport (Aéroport de La Rochelle-Ile de Ré). The organization will provide a shuttle transportation from both the train station and the airport to the site in the evening of the first day, and from the site to the train station and the airport in the morning of the last day.
Cosmology Cosmology

Orateur

Sara Maleubre Molinero (Laboratoire de Physique Nucléaire et de Hautes Energies (LPNHE))

Description

We exploit a suite of large \emph{N}-body simulations (up to N=$4096^3$) performed with \Abacus, of scale-free models with a range of spectral indices $n$, to better understand and quantify convergence of the matter power spectrum in dark matter only cosmological \emph{N}-body simulations. Using self-similarity to identify converged regions,
we show that the maximal wavenumber resolved at a given level of accuracy increases monotonically as a function of
time. At the 1\% level it starts at early times from a fraction of $k_\Lambda$, the Nyquist wavenumber of the initial grid, and
reaches at most, if the force softening is sufficiently small,
$\sim 2 k_\Lambda$ at the very latest times we evolve to. At
the $5\%$ level accuracy extends up to slightly larger wavenumbers, of order $5k_\Lambda$
at late times. Expressed as a suitable function of the scale-factor, accuracy shows a very simple $n$-dependence, allowing a straightforward extrapolation to place conservative bounds on the accuracy of \emph{N}-body simulations of non-scale free models like LCDM. Quantitatively our findings are broadly in line with the conservative assumptions about resolution adopted by recent studies using large cosmological simulations (e.g. Euclid Flagship) aiming to constrain the mildly non-linear regime. On the other hand, we note that studies of the matter power spectrum in the literature have often used data at larger wavenumbers,
where convergence to the physical result is poor.
Even qualitative conclusions about clustering at small scales, e.g concerning the validity of the stable clustering approximation, may need revision in light of our results.

Auteur principal

Sara Maleubre Molinero (Laboratoire de Physique Nucléaire et de Hautes Energies (LPNHE))

Co-auteurs

Prof. Daniel Eisenstein (Harvard&Smithsonian Center for Astrophysics, 60 Garden St, Cambridge, MA 02138) Dr Lehman Garrison (Center for Computational Astrophysics, Flatiron Institute, 162 Fifth Ave., New York, NY 10010) Michael Joyce (LPNHE)

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