High-redshift voids in the excursion set formalism

Voids are a dominant feature of the low-redshift galaxy distribution. Several recent surveys have found evidence for the existence of large-scale structure at high redshifts as well. We present analytic estimates of galaxy void sizes at redshifts z ~ 5 - 10 using the excursion set formalism. We find that recent narrow-band surveys at z ~ 5 - 6.5 should find voids with characteristic scales of roughly 20 comoving Mpc and maximum diameters approaching 40 Mpc. This is consistent with existing surveys, but a precise comparison is difficult because of the relatively small volumes probed so far. At z ~ 7 - 10, we expect characteristic void scales of ~ 14 - 20 comoving Mpc assuming that all galaxies within dark matter haloes more massive than 10^10 M_sun are observable. We find that these characteristic scales are similar to the sizes of empty regions resulting from purely random fluctuations in the galaxy counts. As a result, true large-scale structure will be difficult to observe at z ~ 7 - 10, unless galaxies in haloes with masses less than ~ 10^9 M_sun are visible. Galaxy surveys must be deep and only the largest voids will provide meaningful information. Our model provides a convenient picture for estimating the "worst-case" effects of cosmic variance on high-redshift galaxy surveys with limited volumes.Comment: 12 pages, 9 figures, 1 table, accepted by MNRA

Simulation Analysis of High Velocity Maintenance for the B-1B

This thesis explores the impact that High Velocity Maintenance (HVM) will have on aircraft availability rates for the B-1B by examining the proposed changes to the field maintenance and supply processes for the two B-1B squadrons of the 28th Bombardment Wing located at Ellsworth AFB, SD. There is a significant restructuring of depot level maintenance planned with the implementation of HVM, and the impact that this will have on base-level operations is important to determine, for it will provide insight as to whether or not HVM will be a feasible program with a high probability of successfully improving B-1B aircraft availability rates. To examine the impact of HVM at the base level, discrete-event simulation is used. Two simulation models are created in ARENA 12. The first model captures the current state of operations for the base maintenance and supply processes, while the second model captures the processes as they are planned with the implementation of HVM. Comparisons of the two models reveal that HVM does have the potential to significantly improve aircraft availability rates, but the improvements that must occur with aircraft failure rates and base stockage effectiveness for HVM to operate as planned may not be feasible

Selfish Dark Matter

We present a mechanism where a particle asymmetry in one sector is used to generate an asymmetry in another sector. The two sectors are not coupled through particle number violating interactions and are not required to be in thermal contact with each other. When this mechanism is applied to baryogenesis in asymmetric dark matter models, we find that the dark matter particles can be extremely light, e.g. much lighter than an eV, and that in some cases there is no need to annihilate away the symmetric component of dark matter. We discuss a concrete realization of the mechanism with signals in direct detection, at the LHC, at $B$-factories or future beam dump experiments.Comment: 18+5 pages, 2 figures; Journal version: Added references, small changes to the free-streaming length estimate