Non-standard embedding and five-branes in heterotic M-Theory

We construct vacua of M-theory on S^1/Z_2 associated with Calabi-Yau three-folds. These vacua are appropriate for compactification to N=1 supersymmetry theories in both four and five dimensions. We allow for general E_8 x E_8 gauge bundles and for the presence of five-branes. The five-branes span the four-dimensional uncompactified space and are wrapped on holomorphic curves in the Calabi-Yau space. Properties of these vacua, as well as of the resulting low-energy theories, are discussed. We find that the low-energy gauge group is enlarged by gauge fields that originate on the five-brane world-volumes. In addition, the five-branes increase the types of new E_8 x E_8 breaking patterns allowed by the non-standard embedding. Characteristic features of the low-energy theory, such as the threshold corrections to the gauge kinetic functions, are significantly modified due to the presence of the five-branes, as compared to the case of standard or non-standard embeddings without five-branes.Comment: 34 pages, Latex 2e with amsmath, typos removed, factors corrected, refs improve

Observation of the Ankle and Evidence for a High-Energy Break in the Cosmic Ray Spectrum

We have measured the cosmic ray spectrum at energies above $10^{17}$ eV using the two air fluorescence detectors of the High Resolution Fly's Eye experiment operating in monocular mode. We describe the detector, PMT and atmospheric calibrations, and the analysis techniques for the two detectors. We fit the spectrum to models describing galactic and extragalactic sources. Our measured spectrum gives an observation of a feature known as the ``ankle'' near $3\times 10^{18}$ eV, and strong evidence for a suppression near $6\times 10^{19}$ eV.Comment: 14 pages, 9 figures. To appear in Physics Letters B. Accepted versio

Measurement of Pressure Dependent Fluorescence Yield of Air: Calibration Factor for UHECR Detectors

In a test experiment at the Final Focus Test Beam of the Stanford Linear Accelerator Center, the fluorescence yield of 28.5 GeV electrons in air and nitrogen was measured. The measured photon yields between 300 and 400 nm at 1 atm and 29 deg C are Y(760 Torr, air) = 4.42 +/- 0.73 and Y(760 Torr, nitrogen) = 29.2 +/- 4.8 photons per electron per meter. Assuming that the fluorescence yield is proportional to the energy deposition of a charged particle traveling through air, good agreement with measurements at lower particle energies is observed.Comment: 22 pages, 14 figures, 2 tables, submitted to Astroparticle Physic

A Likelihood Method for Measuring the Ultrahigh Energy Cosmic Ray Composition

Air fluorescence detectors traditionally determine the dominant chemical composit ion of the ultrahigh energy cosmic ray flux by comparing the averaged slant depth of the shower maximum, $X_{max}$, as a function of energy to the slant depths expect ed for various hypothesized primaries. In this paper, we present a method to make a direct measurement of the expected mean number of protons and iron by comparing the shap es of the expected $X_{max}$ distributions to the distribution for data. The advantages of this method includes the use of information of the full distribution and its ability to calculate a flux for various cosmic ray compositi ons. The same method can be expanded to marginalize uncertainties due to choice of spectra, hadronic models and atmospheric parameters. We demonstrate the technique with independent simulated data samples from a parent sample of protons and iron. We accurately predict the number of protons and iron in the parent sample and show that the uncertainties are meaningful.Comment: 11 figures, 22 pages, accepted by Astroparticle Physic

Alternative Methods to Finding Patterns in HiRes Stereo Data

In this paper Ultra High Energy Cosmic Rays UHECRs data observed by the HiRes fluorescence detector in stereo mode is analyzed to search for events in the sky with an arrival direction lying on a great circle. Such structure is known as the arc structure. The arc structure is expected when the charged cosmic rays pass through the galactic magnetic field. The arcs searched for could represent a broad or a small scale anisotropy depending on the proposed source model for the UHECRs. The Arcs in this paper are looked for using Hough transform were Hough transform is a technique used to looking for patterns in images. No statistically significant arcs were found in this study

The Discovery and Mass Measurement of a New Ultra-Short-Period Planet: K2-131b

FWN – Publicaties zonder aanstelling Universiteit LeidenStars and planetary system

Strategic analysis framework for evaluating distributed generation and utility strategies

A strategic analysis framework for evaluating distributed generation and distribution utility strategies is presented. The framework is based on the idea of evaluating all distributed generation issues across many scenarios to encapsulate the breadth of uncertainties stemming from independent distributed generation in regulated distribution networks. A distributed generation value function is proposed to enable distribution system planners and strategists to gauge the aggregate impact of distributed generation on all parts of the distribution business. This enables the distribution company to formulate its response to distributed generation by testing prospective strategies using the range of generation market, power network and utility business models proposed. The results from a case study based on the UK situation shows the potential value of distributed generation (both positive and negative) to distribution network operators. The case study also demonstrates the application of the proposed strategic analysis framework and the value of the results produced

Enhancing flexibility and transparency in the connection of dispersed generation

This paper proposes an approach to assessing generator connection requests that seeks to enhance flexibility and transparency by trading network reinforcement to accommodate generation against operational constraints on the generator that can reduce the required network reinforcement. The impact of dispersed generation and the passing on of costs to generators is briefly discussed. The trade-off concept is introduced and there is supplementary discussion of nondespatchable generation and the monitoring and control of generators. A method of evaluating generator connections is proposed and an example illustrates the resultant choice faced by generators. Finally, some conclusions are draw

Developing distributed generation penetration scenarios

The growth of distributed generation requires analysis based on realistic forecasts of future scenarios. This paper presents an original methodology that has been employed to develop penetration scenarios to support further research. The methodology combines top-down and bottom-up approaches to produce robust scenarios. The top-down approach is based on forecasts of total distributed generation at a national level. The bottom-up approach exploits expert opinion to determine the most likely developments under different conditions. The two approaches are combined according to the objectives of the analysis to be supported. The methodology offers a useful tool for scenario development and supports ongoing research in distributed generation