Accuracy of Lagrangian approximations in voids
Author(s) -
Varun Sahni,
S. F. Shandarin
Publication year - 1996
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-8711
pISSN - 0035-8711
DOI - 10.1093/mnras/282.2.641
Subject(s) - physics , void (composites) , lagrangian , orders of approximation , perturbation (astronomy) , asymptotic expansion , approximations of π , perturbation theory (quantum mechanics) , classical mechanics , statistical physics , mathematical physics , mathematical analysis , quantum mechanics , mathematics , materials science , composite material
We study the behaviour of spherical Voids in Lagrangian perturbation theories L(n), of which the Zel'dovich approximation is the lowest order solution L(1). We find that at early times higher order L(n) give an increasingly accurate picture of Void expansion. However at late times particle trajectories in L(2) begin to turnaround and converge leading to the {\em contraction} of a Void, a sign of pathological behaviour. By contrast particle trajectories in L(3) are well behaved and this approximation gives results in excellent agreement with the exact top-hat solution as long as the Void is not too underdense. For very underdense Voids, L(3) evacuates the Void much too rapidly leading us to conclude that the Zel'dovich approximation L(1), remains the best approximation to apply to the late time study of Voids. The behavior of high order approximations in spherical voids is typical for asymptotic series and may be generic for Lagrangian perturbation theory
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