GEODYN operations description, volume 3

The operating and set-up procedures for the multi-satellite, multi-arc GEODYN- Orbit Determination program are described. All system output is analyzed. The GEODYN Program is the nucleus of the entire GEODYN system. It is a definitive orbit and geodetic parameter estimation program capable of simultaneously processing observations from multiple arcs of multiple satellites. GEODYN has two modes of operation: (1) the data reduction mode and (2) the orbit generation mode

A complete characterisation of the heralded noiseless amplification of photons

Heralded noiseless amplifcation of photons has recently been shown to provide a means to overcome losses in complex quantum communication tasks. In particular, to overcome transmission losses that could allow for the violation of a Bell inequality free from the detection loophole, for Device Independent Quantum Key Distribution (DI-QKD). Several implementations of a heralded photon amplifier have been proposed and the first proof of principle experiments realised. Here we present the first full characterisation of such a device to test its functional limits and potential for DI-QKD. This device is tested at telecom wavelengths and is shown to be capable of overcoming losses corresponding to a transmission through $20\, \rm km$ of single mode telecom fibre. We demonstrate heralded photon amplifier with a gain $>100$ and a heralding probability $>83$, required by DI-QKD protocols that use the Clauser-Horne-Shimony-Holt (CHSH) inequality. The heralded photon amplifier clearly represents a key technology for the realisation of DI-QKD in the real world and over typical network distances.Comment: 9 pages, 4 figure

Inhibitors of Pyruvate Carboxylase

This review aims to discuss the varied types of inhibitors of biotin-dependent carboxylases, with an emphasis on the inhibitors of pyruvate carboxylase. Some of these inhibitors are physiologically relevant, in that they provide ways of regulating the cellular activities of the enzymes e.g. aspartate and prohibitin inhibition of pyruvate carboxylase. Most of the inhibitors that will be discussed have been used to probe various aspects of the structure and function of these enzymes. They target particular parts of the structure e.g. avidin – biotin, FTP – ATP binding site, oxamate – pyruvate binding site, phosphonoacetate – binding site of the putative carboxyphosphate intermediate

Many-spinon states and the secret significance of Young tableaux

We establish a one-to-one correspondence between the Young tableaux classifying the total spin representations of N spins and the exact eigenstates of the the Haldane-Shastry model for a chain with N sites classified by the total spins and the fractionally spaced single-particle momenta of the spinons.Comment: 4 pages, 3 figure

Pulse-splitting in light propagation through NN-type atomic media due to an interplay of Kerr-nonlinearity and group velocity dispersion

We investigate the spatio-temporal evolution of a Gaussian probe pulse propagating through a four-level $N$-type atomic medium. At two-photon resonance of probe-and control fields, weaker probe pulses may propagate through the medium with low absorption and pulse shape distortion. In contrast, we find that increasing the probe pulse intensity leads to a splitting of the initially Gaussian pulse into a sequence of subpulses in the time domain. The number of subpulses arising throughout the propagation can be controlled via a suitable choice of the probe and control field parameters. Employing a simple theoretical model for the nonlinear pulse propagation, we conclude that the splitting occurs due to an interplay of Kerr nonlinearity and group velocity dispersion.Comment: 9 pages, 7 figure

Resummation of double logarithms in electroweak high energy processes

At future linear $e^+e^-$ collider experiments in the TeV range, Sudakov double logarithms originating from massive boson exchange can lead to significant corrections to the cross sections of the observable processes. These effects are important for the high precision objectives of the Next Linear Collider. We use the infrared evolution equation, based on a gauge invariant dispersive method, to obtain double logarithmic asymptotics of scattering amplitudes and discuss how it can be applied, in the case of broken gauge symmetry, to the Standard Model of electroweak processes. We discuss the double logarithmic effects to both non-radiative processes and to processes accompanied by soft gauge boson emission. In all cases the Sudakov double logarithms are found to exponentiate. We also discuss double logarithmic effects of a non-Sudakov type which appear in Regge-like processes.Comment: 26 pages, 3 figures, Latex2

Bright solitary waves of atomic Bose-Einstein condensates under rotation

We analyse the rotation of bright solitary waves formed of atomic Bose-Einstein condensates with attractive atomic interactions. By employing a variational technique and assuming an irrotational quadrupolar flow field, we map out the variational solutions in the rotating frame. In particular, we show that rotation has a considerable stabilising effect on the system, significantly raising the critical threshold for collapse of the bright solitary waves.Comment: 4 pages, 3 figure

Light scattering by an elongated particle: spheroid versus infinite cylinder

Using the method of separation of variables and a new approach to calculations of the prolate spheroidal wave functions, we study the optical properties of very elongated (cigar-like) spheroidal particles. A comparison of extinction efficiency factors of prolate spheroids and infinitely long circular cylinders is made. For the normal and oblique incidence of radiation, the efficiency factors for spheroids converge to some limiting values with an increasing aspect ratio a/b provided particles of the same thickness are considered. These values are close to, but do not coincide with the factors for infinite cylinders. The relative difference between factors for infinite cylinders and elongated spheroids (a/b \ga 5) usually does not exceed 20 % if the following approximate relation between the angle of incidence $\alpha (in degrees)$ and the particle refractive index m=n+ki takes the place: \alpha \ga 50 |m-1| + 5 where 1.2 \la n \la 2.0 and k \la 0.1. We show that the quasistatic approximation can be well used for very elongated optically soft spheroids of large sizes.Comment: 12 pages, 7 figures, Accepted by Measurement Science and Technology (special OPC issue

Analyticity of the Scattering Amplitude, Causality and High-Energy Bounds in Quantum Field Theory on Noncommutative Space-Time

In the framework of quantum field theory (QFT) on noncommutative (NC) space-time with the symmetry group $O(1,1)\times SO(2)$, we prove that the Jost-Lehmann-Dyson representation, based on the causality condition taken in connection with this symmetry, leads to the mere impossibility of drawing any conclusion on the analyticity of the $2\to 2$-scattering amplitude in $\cos\Theta$, $\Theta$ being the scattering angle. Discussions on the possible ways of obtaining high-energy bounds analogous to the Froissart-Martin bound on the total cross-section are also presented.Comment: 25 page

Ultra-high energy neutrino scattering

Estimates are made of the ultra-high energy neutrino cross sections based on an extrapolation to very small Bjorken x of the logarithmic Froissart dependence in x shown previously to provide an excellent fit to the measured proton structure function F_2^p(x,Q^2) over a broad range of the virtuality Q^2. Expressions are obtained for both the neutral current and the charged current cross sections. Comparison with an extrapolation based on perturbative QCD shows good agreement for energies where both fit data, but our rates are as much as a factor of 10 smaller for neutrino energies above 10^9 GeV, with important implications for experiments searching for extra-galactic neutrinos.Comment: 4 pages, 1 figure, 1 table; Title, abstract and text changed, conclusions unchanged. Version accepted for publication in Physical Review