Open inflation and the singular boundary

The singularity in Hawking and Turok's model (hep-th/9802030) of open inflation has some appealing properties. We suggest that this singularity should be regularized with matter. The singular instanton can then be obtained as the limit of a family of ``no-boundary'' solutions where both the geometry and the scalar field are regular. Using this procedure, the contribution of the singularity to the Euclidean action is just 1/3 of the Gibbons-Hawking boundary term. Unrelated to this question, we also point out that gravitational backreaction improves the behaviour of scalar perturbations near the singularity. As a result, the problem of quantizing scalar perturbations and gravity waves seems to be very well posed.Comment: 7 page

A prescription for probabilities in eternal inflation

Some of the parameters we call ``constants of Nature'' may in fact be variables related to the local values of some dynamical fields. During inflation, these variables are randomized by quantum fluctuations. In cases when the variable in question (call it $\chi$) takes values in a continuous range, all thermalized regions in the universe are statistically equivalent, and a gauge invariant procedure for calculating the probability distribution for $\chi$ is known. This is the so-called ``spherical cutoff method''. In order to find the probability distribution for $\chi$ it suffices to consider a large spherical patch in a single thermalized region. Here, we generalize this method to the case when the range of $\chi$ is discontinuous and there are several different types of thermalized region. We first formulate a set of requirements that any such generalization should satisfy, and then introduce a prescription that meets all the requirements. We finally apply this prescription to calculate the relative probability for different bubble universes in the open inflation scenario.Comment: 15 pages, 5 figure

Exact Relativistic Two-Body Motion in Lineal Gravity

We consider the N-body problem in (1+1) dimensional lineal gravity. For 2 point masses (N=2) we obtain an exact solution for the relativistic motion. In the equal mass case we obtain an explicit expression for their proper separation as a function of their mutual proper time. Our solution gives the exact Hamiltonian to infinite order in the gravitational coupling constant.Comment: latex, 11 pages, 2 figures, final version to appear in Phys. Rev. Let

Rotating Dilaton Solutions in 2+1 Dimensions

We report a three parameter family of solutions for dilaton gravity in 2+1 dimensions with finite mass and finite angular momentum. These solutions are obtained by a compactification of vacuum solutions in 3+1 dimensions with cylindrical symmetry. One class of solutions corresponds to conical singularities and the other leads to curvature singularities.Comment: Accepted to be published in Gen. Rel. Grav., added reference

Collisions of particles in locally AdS spacetimes I. Local description and global examples

We investigate 3-dimensional globally hyperbolic AdS manifolds containing "particles", i.e., cone singularities along a graph $\Gamma$. We impose physically relevant conditions on the cone singularities, e.g. positivity of mass (angle less than $2\pi$ on time-like singular segments). We construct examples of such manifolds, describe the cone singularities that can arise and the way they can interact (the local geometry near the vertices of $\Gamma$). We then adapt to this setting some notions like global hyperbolicity which are natural for Lorentz manifolds, and construct some examples of globally hyperbolic AdS manifolds with interacting particles.Comment: This is a rewritten version of the first part of arxiv:0905.1823. That preprint was too long and contained two types of results, so we sliced it in two. This is the first part. Some sections have been completely rewritten so as to be more readable, at the cost of slightly less general statements. Others parts have been notably improved to increase readabilit

Primordial Gravitational Waves From Open Inflation

We calculate the spectrum of gravitational waves generated during inflation in open $(\Omega _0<1)$ inflationary models. In such models an initial epoch of old inflation solves the horizon and flatness problems, and during this first epoch of inflation the quantum state of the graviton field rapidly approaches the Bunch-Davies vacuum. Then old inflation ends by the nucleation of a single bubble, inside of which there is a shortened epoch of slow-roll inflation giving $\Omega _0<1$ today. In this paper we re-express the Bunch-Davies vacuum for the graviton field in terms of the hyperbolic modes inside the bubble and propagate these modes forward in time into the present era. We derive the expression for the contribution from these gravity waves to the cosmic microwave background anisotropy including the effect of a finite energy difference across the bubble wall.Comment: 40 pages, TEX with phyzzx macro, 5 figure

The architecture of Abell 1386 and its relationship to the Sloan Great Wall

We present new radial velocities from AAOmega on the Anglo-Australian Telescope for 307 galaxies (b_J < 19.5) in the region of the rich cluster Abell 1386. Consistent with other studies of galaxy clusters that constitute sub-units of superstructures, we find that the velocity distribution of A1386 is very broad (21,000--42,000 kms^-1, or z=0.08--0.14) and complex. The mean redshift of the cluster that Abell designated as number 1386 is found to be ~0.104. However, we find that it consists of various superpositions of line-of-sight components. We investigate the reality of each component by testing for substructure and searching for giant elliptical galaxies in each and show that A1386 is made up of at least four significant clusters or groups along the line of sight whose global parameters we detail. Peculiar velocities of brightest galaxies for each of the groups are computed and found to be different from previous works, largely due to the complexity of the sky area and the depth of analysis performed in the present work. We also analyse A1386 in the context of its parent superclusters: Leo A, and especially the Sloan Great Wall. Although the new clusters may be moving toward mass concentrations in the Sloan Great Wall or beyond, many are most likely not yet physically bound to it.Comment: 21 pages, 9 figures, includes the full appendix table. Accepted for publication in MNRA

Particle Spectrum Created Through Bubble Nucleation

Using the multi-dimensional wave function formalism, we investigate the quantum state of a scalar field inside a true vacuum bubble nucleated through false vacuum decay in flat spacetime. We developed a formalism which allows us a mode-by-mode analysis. To demonstrate its advantage, we describe in detail the evolution of the quantum state during the tunneling process in terms of individual mode functions and interpret the result in the language of particle creation. The spectrum of the created particles is examined based on quantum field theory in the Milne universe.Comment: 14 pages, revtex file, 4 uuencoded compressed postscript figures appended at the en

Combined Risk Factors and Digestive Disorders in Mid-Lactation Holstein Cows: A Case Study

Digestive disorders can be a significant cause of disease on dairies and are frustrating because of their unpredictability. Diets that may support excellent health in most cases may nonetheless result in significant gastrointestinal disease, even leading to deadly conditions such as hemorrhagic bowel syndrome. To our knowledge, there is limited research on these conditions, as many risk factors fail to reproduce disease when experimentally administered to cows, leading many to conclude that these disorders are generally multifactorial in nature and difficult to replicate. In this case study, we document the outbreak and resolution of digestive disorders among 15 control cows enrolled in a larger production study. Over 14 weeks, cows were individually fed, with milk yield and composition, blood variables, and health observations recorded. The diet included drought-stressed corn silage that introduced difficulties including low energy density, high dry matter content (making it unstable at feedout), and mycotoxin contamination. By weeks 4–5 on the study, sporadic diarrhea began to appear and milk fat content had dropped from 3.7% to 3.4%, on average. Coincident with the onset of environmental heat stress, three cows developed severe digestive disorders, resulting in a displaced abomasum in one cow. At that point, the diet was changed to replace some corn silage with wheat straw, a direct-fed microbial was added to the diet, and organic acid treatment of the silage face was initiated. Within a month after these changes were implemented, essentially all signs of digestive problems resolved, including milk fat content, fecal consistency, and blood plasma concentrations of haptoglobin and D-lactate. This case study points to multiple factors that likely combined to lead to microbial and gastrointestinal disruptions resulting in clinical disease in a subset of cows