Extremely high energy cosmic rays from relic particle decays

The expected proton and neutrino fluxes from decays of massive metastable relic particles is calculated using the HERWIG QCD event generator. The predicted proton spectrum can account for the observed flux of extremely high energy cosmic rays beyond the Greisen-Zatsepin-Kuzmin cutoff, for a decaying particle mass of O(10^{12}) GeV. The lifetime required is of O(10^{20}) yr if such particles constitute all of the dark matter (with a proportionally shorter lifetime for a smaller contribution). Such values are plausible if the metastable particles are hadron-like bound states from the hidden sector of supersymmetry breaking which decay through non-renormalizable interactions. The expected ratio of the proton to neutrino flux is given as a diagonistic of the decaying particle model for the forthcoming Pierre Auger project.Comment: 25 pages (Revtex) incl. 10 figures (epsf); Minor changes to reflect version accepted for publicatio

Simulation of neutrino and charged particle production and propagation in the atmosphere

A precise evaluation of the secondary particle production and propagation in the atmosphere is very important for the atmospheric neutrino oscillation studies. The issue is addressed with the extension of a previously developed full 3-Dimensional Monte-Carlo simulation of particle generation and transport in the atmosphere, to compute the flux of secondary protons, muons and neutrinos. Recent balloon borne experiments have performed a set of accurate flux measurements for different particle species at different altitudes in the atmosphere, which can be used to test the calculations for the atmospheric neutrino production, and constrain the underlying hadronic models. The simulation results are reported and compared with the latest flux measurements. It is shown that the level of precision reached by these experiments could be used to constrain the nuclear models used in the simulation. The implication of these results for the atmospheric neutrino flux calculation are discussed.Comment: 11 pages, 9 figure

DWSB in heterotic flux compactifications

We address the construction of non-supersymmetric vacua in heterotic compactifications with intrinsic torsion and background fluxes. In particular, we implement the approach of domain-wall supersymmetry breaking (DWSB) previously developed in the context of type II flux compactifications. This approach is based on considering backgrounds where probe NS5-branes wrapping internal three-cycles and showing up as four-dimensional domain-walls do not develop a BPS bound, while all the other BPS bounds characterizing the N=1 supersymmetric compactifications are preserved at tree-level. Via a scalar potential analysis we provide the conditions for these backgrounds to solve the ten-dimensional equations of motion including order \alpha' corrections. We also consider backgrounds where some of the NS5-domain-walls develop a BPS bound, show their relation to no-scale SUSY-breaking vacua and construct explicit examples via elliptic fibrations. Finally, we consider backgrounds with a non-trivial gaugino condensate and discuss their relation to supersymmetric and non-supersymmetric vacua in the present context.Comment: 56 pages, 1 figur

Flatness-Based Control Methodologies to Improve Frequency Regulation in Power Systems with High Penetration of Wind

To allow for high penetration of distributed generation and alternative energy units, it is critical to minimize the complexity of generator controls and to minimize the need for close coordination across regions. We propose that existing controls be replaced by a two-tier structure of local control operating within a global context of situational awareness. Flatness as an extension of controllability for non-linear systems is a key to enabling planning and optimization at various levels of the grid in this structure. In this study, flatness-based control for: one, Automatic Generation Control (AGC) of a multi-machine system including conventional generators; and two, Doubly fed Induction Machine (DFIG) is investigated. In the proposed approach applied to conventional generators, the local control tracks the reference phase, which is obtained through economic dispatch at the global control level. As a result of applying the flatness-based method, an $n$ machine system is decoupled into n linear controllable systems in canonical form. The control strategy results in a distributed AGC formulation which is significantly easier to design and implement relative to conventional AGC. Practical constraints such as generator ramping rates can be considered in designing the local controllers. The proposed strategy demonstrates promising performance in mitigating frequency deviations and the overall structure facilitates operation of other non-traditional generators. For DFIG, the rotor flux and rotational speed are controlled to follow the desired values for active and reactive power control. Different control objectives, such as maximum power point tracking (MPPT), voltage support or curtailing wind to contribute in secondary frequency regulation, can be achieved in this two-level control structure

Resolving phase transitions with Discontinuous Galerkin methods

We demonstrate the applicability and advantages of Discontinuous Galerkin (DG) schemes in the context of the Functional Renormalization Group (FRG). We investigate the $O(N)$-model in the large $N$ limit. It is shown that the flow equation for the effective potential can be cast into a conservative form. We discuss results for the Riemann problem, as well as initial conditions leading to a first and second order phase transition. In particular, we unravel the mechanism underlying first order phase transitions, based on the formation of a shock in the derivative of the effective potential.Comment: 19 pages, 9 figures, corrected typos, updated references, extended explanation