Growth structures in a Friedmann universe

Journal Article · Sun Nov 15 04:00:00 EST 1981 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/159391· OSTI ID:5609205

Barrow, J D; Silk, J

Motivated by observational evidence for the existence of flattened or striated structures of very large scale (approx.100 Mpc) in the universe, we study the evolution of nonspherical structures. We set up equations to describe the evolution of a rotating, dust ellipsoid in an expanding universe. We derive solutions for the shape and density evolutions as the ellipsoid expands along with a Friedmann background universe and show that deviations from spherical symmetry are preserved by adiabatic expansion. Analytic expressions are derived to describe the nonlinear evolution of pressure-free ellipsoids. We calculate details of ''pancake'' formation which are relevant for realistic theories of galaxy and cluster formation. In particular, the density collapse at turnaround and the collapse velocity at pancake formation are found to be reduced relative to the spherical case if the initial fluctuations are anisotropic: this may affect kinematic determinations of ..cap omega.. in the local supercluster and also enable galaxies with massive halos to form during the fragmentation of pancakes whose dynamics are dominated by massive neutrinos. Significant deviations from spherical symmetry in the baryon irregularity spectrum might also be naturally associated with primordial isothermal inhomogeneities in a Friedmann universe and their possible origin at the epoch of ''grand unification.'' An exact model for a general relativistic pancake collapse is given, based on an exact solution to Einstein's equations found by Szekeres. This collapse does not pass through a series of ellipsoids and has no symmetries.

• Research Organization: Department of Physics, University of California at Berkeley
• OSTI ID: 5609205
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 250:2; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640105 -- Astrophysics & Cosmology-- Galaxies
640106* -- Astrophysics & Cosmology-- Cosmology
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ANISOTROPY
BARYONS
CONFIGURATION
COSMOLOGICAL MODELS
COSMOLOGY
EINSTEIN FIELD EQUATIONS
ELEMENTARY PARTICLES
ELLIPTICAL CONFIGURATION
EQUATIONS
EXPANSION
FERMIONS
FIELD EQUATIONS
FIELD THEORIES
GALACTIC EVOLUTION
GENERAL RELATIVITY THEORY
GRAVITATIONAL COLLAPSE
HADRONS
MATHEMATICAL MODELS
MOTION
ROTATION
SPACE-TIME
UNIVERSE