281 research outputs found

### Bubble, Bubble, Flow and Hubble: Large Scale Galaxy Flow from Cosmological Bubble Collisions

We study large scale structure in the cosmology of Coleman-de Luccia bubble
collisions. Within a set of controlled approximations we calculate the effects
on galaxy motion seen from inside a bubble which has undergone such a
collision. We find that generically bubble collisions lead to a coherent bulk
flow of galaxies on some part of our sky, the details of which depend on the
initial conditions of the collision and redshift to the galaxy in question.
With other parameters held fixed the effects weaken as the amount of inflation
inside our bubble grows, but can produce measurable flows past the number of
efolds required to solve the flatness and horizon problems.Comment: 30 pages, 8 figures, pdftex, minor corrections and references adde

### Anthropic Explanation of the Dark Matter Abundance

I use Bousso's causal diamond measure to make a statistical prediction for
the dark matter abundance, assuming an axion with a large decay constant f_a >>
10^{12} GeV. Using a crude approximation for observer formation, the prediction
agrees well with observation: 30% of observers form in regions with less dark
matter than we observe, while 70% of observers form in regions with more dark
matter. Large values of the dark matter ratio are disfavored by an elementary
effect: increasing the amount of dark matter while holding fixed the baryon to
photon ratio decreases the number of baryons inside one horizon volume. Thus
the prediction is rather insensitive to assumptions about observer formation in
universes with much more dark matter than our own. The key assumption is that
the number of observers per baryon is roughly independent of the dark matter
ratio for ratios near the observed value.Comment: 10 pages; v3: published version, references adde

### Properties of a future susy universe

In the string landscape picture, the effective potential is characterized by
an enormous number of local minima of which only a minuscule fraction are
suitable for the evolution of life. In this "multiverse", random transitions
are continually made between the various minima with the most likely
transitions being to minima of lower vacuum energy. The inflationary era in the
very early universe ended with such a transition to our current phase which is
described by a broken supersymmetry and a small, positive vacuum energy.
However, it is likely that an exactly supersymmetric (susy) phase of zero
vacuum energy as in the original superstring theory also exists and that, at
some time in the future, there will be a transition to this susy world. In this
article we make some preliminary estimates of the consequences of such a
transition.Comment: 17 pages, 3 figures; intermediate extensions/revisions available at
http://www.bama.ua.edu/~lclavell/Susyria.pd

### Spatial Curvature Falsifies Eternal Inflation

Inflation creates large-scale cosmological density perturbations that are
characterized by an isotropic, homogeneous, and Gaussian random distribution
about a locally flat background. Even in a flat universe, the spatial curvature
measured within one Hubble volume receives contributions from long wavelength
perturbations, and will not in general be zero. These same perturbations
determine the Cosmic Microwave Background (CMB) temperature fluctuations, which
are O(10^-5). Consequently, the low-l multipole moments in the CMB temperature
map predict the value of the measured spatial curvature \Omega_k. On this basis
we argue that a measurement of |\Omega_k| > 10^-4 would rule out slow-roll
eternal inflation in our past with high confidence, while a measurement of
\Omega_k < -10^-4 (which is positive curvature, a locally closed universe)
rules out false-vacuum eternal inflation as well, at the same confidence level.
In other words, negative curvature (a locally open universe) is consistent with
false-vacuum eternal inflation but not with slow-roll eternal inflation, and
positive curvature falsifies both. Near-future experiments will dramatically
extend the sensitivity of \Omega_k measurements and constitute a sharp test of
these predictions.Comment: 16+2 pages, 2 figure

### A Conformal Field Theory for Eternal Inflation

We study a statistical model defined by a conformally invariant distribution
of overlapping spheres in arbitrary dimension d. The model arises as the
asymptotic distribution of cosmic bubbles in d+1 dimensional de Sitter space,
and also as the asymptotic distribution of bubble collisions with the domain
wall of a fiducial "observation bubble" in d+2 dimensional de Sitter space. In
this note we calculate the 2-,3-, and 4-point correlation functions of
exponentials of the "bubble number operator" analytically in d=2. We find that
these correlators, when carefully defined, are free of infrared divergences,
covariant under the global conformal group, charge conserving, and transform
with positive conformal dimensions that are related in a novel way to the
charge. Although by themselves these operators probably do not define a
full-fledged conformal field theory, one can use the partition function on a
sphere to compute an approximate central charge in the 2D case. The theory in
any dimension has a noninteracting limit when the nucleation rate of the
bubbles in the bulk is very large. The theory in two dimensions is related to
some models of continuum percolation, but it is conformal for all values of the
tunneling rate.Comment: 30 pages, 8 figure

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