R. Durrer et Zh. Zhou, LARGE-SCALE STRUCTURE FORMATION WITH GLOBAL TOPOLOGICAL DEFECTS, Physical review. D. Particles and fields, 53(10), 1996, pp. 5394-5410
We investigate cosmological structure formation seeded by topological
defects which may form during a phase transition in the early Universe
. First, we derive a partially new, local, and gauge-invariant system
of perturbation equations to treat microwave background and dark matte
r fluctuations induced by topological defects or any other type of see
ds. We then show that this system is well suited for numerical analysi
s of structure formation by applying it to seeds induced by fluctuatio
ns of a global scalar field. Our numerical results cover a larger dyna
mical range than those covered by previous investigations and are comp
lementary to them since we use substantially different methods. The re
sulting microwave background fluctuations are compatible with older si
mulations. We also obtain a scale-invariant spectrum of fluctuations a
lthough with somewhat higher amplitude. On the other hand, our dark ma
tter results yield a smaller bias parameter compatible with b similar
to 2 on scales of 20h(-1) Mpc in contrast with previous work which yie
lded larger bias factors. Our conclusions are thus more positive. Acco
rding to the aspects analyzed in this work, global topological defect-
induced fluctuations yield viable scenarios of structure formation and
do better than standard CDM on large scales.