121426208
Vacuum Energy in Gauged Extended Supergravity
Abstract The one loop vacuum energy in gauged extended supergravity is calculated in anti de Sitter space using zeta function regularisation. It vanishes for N ⩾ 5. The energy zeta function has no poles for N ⩾ 3.
118590129
CMB anisotropy due to cosmic strings: Large angular scale
54002264
The SU(5) potential in desitter space
Abstract The one-loop effective potential for a minimal SU (5) theory is calculated on a curved DeSitter background spacetime. The stability of its extrema in the following subgroups is investigated: SU (4) × U (1), SU (3) × SU (2) × U (1), SU (3) × U (1) × U (1), SU (2) × SU (2) × U (1) × U (1). A combination of analytic and numerical methods is used to obtain phase diagrams for the model. In the inflationary universe, the curvature effects do not prevent a slide into the SU (4) × U (1) extremum.
13728005
Large Angular Scale CMB Anisotropy Induced by Cosmic Strings
B. Allen, R. R. Caldwell, E. P. S. Shellard, A. Stebbins, and S. Veeraraghavan Department of Physics, University of Wisconsin – Milwaukee, P.O. Box 413, Milwaukee, Wisconsin 53201, U.S.A. University of Cambridge, D.A.M.T.P. Silver Street, Cambridge CB3 9EW, U.K. NASA/Fermilab Astrophysics Center, P.O. Box 500, Batavia, Illinois 60510, U.S.A. NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771
7392737
Timing of a Young Mildly Recycled Pulsar with a Massive White Dwarf Companion
We report on timing observations of the recently discovered binary pulsar PSR J1952+2630 using the Arecibo Observatory. The mildly recycled 20.7-ms pulsar is in a 9.4-hr orbit with a massive, MW D > 0.93 M⊙, white dwarf (WD) companion. We present, for the first time, a phase-coherent timing solution, with precise spin, astrometric, and Keplerian orbital parameters. This shows that the characteristic age of PSR J1952+2630 is 77 Myr, younger by one order of magnitude than any other recycled pulsar–massive WD system. We derive an upper limit on the true age of the system of 150 Myr. We investigate the formation of PSR J1952+2630 using detailed modelling of the mass-transfer process from a naked helium star on to the neutron star following a common-envelope phase (Case BB Roche-lobe overflow). From our modelling of the progenitor system, we constrain the accretion efficiency of the neutron star, which suggests a value between 100 and 300% of the Eddington accretion limit. We present numerical models of the chemical structure of a possible oxygenneon-magnesium WD companion. Furthermore, we calculate the past and the future spin evolution of PSR J1952+2630, until the system merges in about 3.4 Gyr due to gravitational wave emission. Although we detect no relativistic effects in our timing analysis we show that several such effects will become measurable with continued observations over the next 10 years; thus PSR J1952+2630 has potential as a testbed for gravitational theories.
118708943
Multi-taper Spectral Analysis in Gravitational Wave Data Analysis
Spectral estimation plays a significant role in gravitational wave data analysis. We provide a brief introduction to multi-taper methods which use multiple orthogonal tapers (or windows) to provide spectral estimators with excellent bias and variance properties. Multi-taper methods are also extremely powerful for the estimation and removal of sharp spectral peaks in the presence of noise such as arise due to power line harmonics or suspension resonances. We present examples of these methods using the GRASP (Gravitational Radiation Analysis and Simulation Package) software package.
124123364
Comments on the Doorway State in Pb 206
The neutron capture cross section of $^{206}\mathrm{Pb}(n, \ensuremath{\gamma})$ has been measured with high resolution at the Oak Ridge electron linear accelerator. The capture results show that the reported ${s}_{\frac{1}{2}}$ doorway in $^{206}\mathrm{Pb}$ is not observed in the photon channel.
138041514
GENERATION AND CHARACTERIZATION OF 5-MICRON ELECTRON BEAM FOR PROBING OPTICAL SCALE STRUCTURES
In recent years advanced acceleration technologies have progress toward combination of electron beam, laser and optical scale dielectric structures. In present paper described generation of the electron beam probe with parameters satisfied to perform test of such optical structures.
35408696
WITNESS BUNCH ACCELERATION IN A MULTI-BUNCH PWFA ∗
We present initial experimental results showing the excitation of plasma wakefields by a train of two drive bunches. These wakefields are experienced by a trailing witness bunch that gains energy while retaining a finite energy spread. These well controlled plasma wakefield accelerator (PWFA) experiments are important to test the theory of the PWFA and serve as a testbed for techniques that will be used in high energy experiments.
117206415
Event‐by‐Event Energy Estimation and Spectral Determination with Milagro
The observed characteristics of a TeV gamma ray shower which triggers Milagro depend on core location, zenith angle, and primary energy. An algorithm to estimate the primary energy on an event‐by‐event basis based upon observed quantities has been devised. This algorithm is applied to signals observed from sources to determine energy spectra in the energy range 1 to 100 TeV. Results for spectral determination are presented for the Crab nebula. For the Crab nebula our results are similar to atmospheric Cherenkov telescope measurements.
121348159
Measurement of the Crab spectrum with Milagro
Through use of new algorithms for estimating γ-ray and cosmic ray primary energies of events in Milagro we determine the energy spectra of gamma rays from the Crab nebula and spectra of Milagro background triggers have been determined in the energy range 1 to 100 TeV. The measured spectra are compared with those measured by ACT techniques and direct measurements of cosmic ray spectra.