The Fourth Generation t-prime in Extensions of the Standard Model

We study the effects of a fourth generation t' quark in various extensions of the standard model. In the Randall-Sundrum model, the decay t'--> t Z has a large branching ratio that could be detected at the Large Hadron Collider (LHC). We also look at the two-Higgs doublet models I, II and III, and note that, in the latter, the branching ratio of t' --> t H, where H is a Higgs scalar or pseudoscalar, is huge and we discuss detection at the LHC. A few comments about the minimal supersymmetric standard model are also included.Comment: 4 pages, 2 figures. Version to be published in Phys. Rev.

Watson's theorem and electromagnetism in K -> pi pi decay

We consider what constraints unitarity and CPT invariance yield on the strong and electromagnetic phases entering K -> pi pi decay. In particular, we show that the relative size of the electromagnetically-induced changes in the I=0 and I=2 phase shifts in the two--pion final state do not depend on the explicit coupling to the pi^+ pi^- gamma channel. This demonstrates that Watson's theorem can be extended to include the presence of electromagnetism. We point out the consequences for the general structure of the K -> pi pi decay amplitudes in the presence of isospin violation.Comment: 7 pages, LaTeX, axodraw.st

Dense Regular Packings of Irregular Non-Convex Particles

We present a new numerical scheme to study systems of non-convex, irregular, and punctured particles in an efficient manner. We employ this method to analyze regular packings of odd-shaped bodies, not only from a nanoparticle but also both from a computational geometry perspective. Besides determining close-packed structures for many shapes, we also discover a new denser configuration for Truncated Tetrahedra. Moreover, we consider recently synthesized nanoparticles and colloids, where we focus on the excluded volume interactions, to show the applicability of our method in the investigation of their crystal structures and phase behavior. Extensions to the presented scheme include the incorporation of soft particle-particle interactions, the study of quasicrystalline systems, and random packings.Comment: 4 pages, 3 figure

Far-Ultraviolet Number Counts of Field Galaxies

The far-ultraviolet (FUV) number counts of galaxies constrain the evolution of the star-formation rate density of the universe. We report the FUV number counts computed from FUV imaging of several fields including the Hubble Ultra Deep Field, the Hubble Deep Field North, and small areas within the GOODS-North and -South fields. These data were obtained with the Hubble Space Telescope Solar Blind Channel of the Advance Camera for Surveys. The number counts sample a FUV AB magnitude range from 21-29 and cover a total area of 15.9 arcmin^2, ~4 times larger than the most recent HST FUV study. Our FUV counts intersect bright FUV GALEX counts at 22.5 mag and they show good agreement with recent semi-analytic models based on dark matter "merger trees" by Somerville et al. (2011). We show that the number counts are ~35% lower than in previous HST studies that use smaller areas. The differences between these studies are likely the result of cosmic variance; our new data cover more lines of sight and more area than previous HST FUV studies. The integrated light from field galaxies is found to contribute between 65.9 +/-8 - 82.6 +/-12 photons/s/cm^2/sr/angstrom to the FUV extragalactic background. These measurements set a lower limit for the total FUV background light.Comment: Accepted for publication in ApJ, including 34 pages, 6 figures, and 2 table

A Web/Grid Services Approach for Integration of Virtual Clinical & Research Environments

Clinicans have responsibilities for audit and research, often participating in projects with basic scientist colleagues. Our work in a regional teaching hospital setting involves collaboration with the medical school computer services and builds upon work developed in computer science department as part of the Collaborative Orthopaedic Research Environment (CORE) project[1]. This has established a pilot study for proof of concept work. Users are mapped to a personal profile implemented using XML and a service oriented architecture (SOA)[2,3]. This bridges the e-Health and e-Science domains, addressing some of the basic questions of security and uptake

Far-Ultraviolet Number Counts on Field Galaxies

The far-ultraviolet (FUV) number counts of galaxies constrain the evolution of the star formation rate density of the universe. We report the FUV number counts computed from FUV imaging of several fields including the Hubble Ultra Deep Field, the Hubble Deep Field North, and small areas within the GOODS-North and South fields. These data were obtained with the Hubble Space Telescope (HST) Solar Blind Channel of the Advance Camera for Surveys. The number counts sample an FUV AB magnitude range from 21 to 29 and cover a total area of 15.9 arcmin^2, ~4 times larger than the most recent HST FUV study. Our FUV counts intersect bright FUV Galaxy Evolution Explorer counts at 22.5 mag and they show good agreement with recent semi-analytic models based on dark matter "merger trees" by R. S. Somerville et al. We show that the number counts are ~35% lower than in previous HST studies that use smaller areas. The differences between these studies are likely the result of cosmic variance; our new data cover more lines of sight and more area than previous HST FUV studies. The integrated light from field galaxies is found to contribute between 65.9^(+8)_(–8) and 82.6^(+12)_(–)12 photons s^(–1) cm^(–2) sr^(–1) Å^(–1) to the FUV extragalactic background. These measurements set a lower limit for the total FUV background light

Statistical mechanics of the multi-constraint continuous knapsack problem

We apply the replica analysis established by Gardner to the multi-constraint continuous knapsack problem,which is one of the linear programming problems and a most fundamental problem in the field of operations research (OR). For a large problem size, we analyse the space of solution and its volume, and estimate the optimal number of items to go into the knapsack as a function of the number of constraints. We study the stability of the replica symmetric (RS) solution and find that the RS calculation cannot estimate the optimal number of items in knapsack correctly if many constraints are required.In order to obtain a consistent solution in the RS region,we try the zero entropy approximation for this continuous solution space and get a stable solution within the RS ansatz.On the other hand, in replica symmetry breaking (RSB) region, the one step RSB solution is found by Parisi's scheme. It turns out that this problem is closely related to the problem of optimal storage capacity and of generalization by maximum stability rule of a spherical perceptron.Comment: Latex 13 pages using IOP style file, 5 figure

Near-Ultraviolet Sources in the Hubble Ultra Deep Field: The Catalog

The catalog from the first high-resolution U-band image of the Hubble Ultra Deep Field, taken with Hubble's Wide-Field Planetary Camera 2 through the F300W filter, is presented. We detect 96 U-band objects and compare and combine this catalog with a Great Observatories Origins Deep Survey B-selected catalog that provides B, V, i, and z photometry, spectral types, and photometric redshifts. We have also obtained far-ultraviolet (FUV, 1614 Å) data with Hubble's Advanced Camera for Surveys Solar Blind Channel (ACS/SBC) and with GALEX. We detected 31 sources with ACS/SBC, 28 with GALEX/FUV, and 45 with GALEX/NUV. The methods of observations, image processing, object identification, catalog preparation, and catalog matching are presented