Digital system detects binary code patterns containing errors

System of square loop magnetic cores associated with code input registers to react to input code patterns by reference to a group of control cores in such a manner that errors are canceled and patterns containing errors are accepted for amplification and processing. This technique improves reception capabilities in PCM telemetry systems

Isotopic ratios at z=0.68 from molecular absorption lines toward B 0218+357

Isotopic ratios of heavy elements are a key signature of the nucleosynthesis processes in stellar interiors. The contribution of successive generations of stars to the metal enrichment of the Universe is imprinted on the evolution of isotopic ratios over time. We investigate the isotopic ratios of carbon, nitrogen, oxygen, and sulfur through millimeter molecular absorption lines arising in the z=0.68 absorber toward the blazar B 0218+357. We find that these ratios differ from those observed in the Galactic interstellar medium, but are remarkably close to those in the only other source at intermediate redshift for which isotopic ratios have been measured to date, the z=0.89 absorber in front of PKS1830-211. The isotopic ratios in these two absorbers should reflect enrichment mostly from massive stars, and they are indeed close to the values observed toward local starburst galaxies. Our measurements set constraints on nucleosynthesis and chemical evolution models.Comment: Accepted for publication in Astronomy & Astrophysics; 10 pages, 9 figure

Quantum double of a (locally) compact group

We generalise the quantum double construction of Drinfel'd to the case of the (Hopf) algebra of suitable functions on a compact or locally compact group. We will concentrate on the *-algebra structure of the quantum double. If the conjugacy classes in the group are countably separated, then we classify the irreducible *-representations by using the connection with so-called transformation group algebras. For finite groups, we will compare our description to the result of Dijkgraaf, Pasquier and Roche. Finally we will work out the explicit examples of SU(2) and SL(2,R).Comment: LaTeX2e, 18 pages. Univ. of Amsterdam, Depts. of Math. and of Theor.Phys., to be published in the Journal of Lie Theor

Tensor product representations of the quantum double of a compact group

We consider the quantum double D(G) of a compact group G, following an earlier paper. We use the explicit comultiplication on D(G) in order to build tensor products of irreducible *-representations. Then we study their behaviour under the action of the R-matrix, and their decomposition into irreducible *-representations. The example of D(SU(2)) is treated in detail, with explicit formulas for direct integral decomposition (`Clebsch-Gordan series') and Clebsch-Gordan coefficients. We point out possible physical applications.Comment: LaTeX2e, 27 pages, corrected references, accepted by Comm.Math.Phy

Development of a Polysilicon Process Based on Chemical Vapor Deposition of Dichlorosilane in an Advanced Siemen's Reactor

Dichlorosilane (DCS) was used as the feedstock for an advanced decomposition reactor for silicon production. The advanced reactor had a cool bell jar wall temperature, 300 C, when compared to Siemen's reactors previously used for DCS decomposition. Previous reactors had bell jar wall temperatures of approximately 750 C. The cooler wall temperature allows higher DCS flow rates and concentrations. A silicon deposition rate of 2.28 gm/hr-cm was achieved with power consumption of 59 kWh/kg. Interpretation of data suggests that a 2.8 gm/hr-cm deposition rate is possible. Screening of lower cost materials of construction was done as a separate program segment. Stainless Steel (304 and 316), Hastalloy B, Monel 400 and 1010-Carbon Steel were placed individually in an experimental scale reactor. Silicon was deposited from trichlorosilane feedstock. The resultant silicon was analyzed for electrically active and metallic impurities as well as carbon. No material contributed significant amounts of electrically active or metallic impurities, but all contributed carbon

Nuclear Matter on a Lattice

We investigate nuclear matter on a cubic lattice. An exact thermal formalism is applied to nucleons with a Hamiltonian that accommodates on-site and next-neighbor parts of the central, spin- and isospin-exchange interactions. We describe the nuclear matter Monte Carlo methods which contain elements from shell model Monte Carlo methods and from numerical simulations of the Hubbard model. We show that energy and basic saturation properties of nuclear matter can be reproduced. Evidence of a first-order phase transition from an uncorrelated Fermi gas to a clustered system is observed by computing mechanical and thermodynamical quantities such as compressibility, heat capacity, entropy and grand potential. We compare symmetry energy and first sound velocities with literature and find reasonable agreement.Comment: 23 pages, 8 figures (some in color), to be submitted to Phys. Rev.

Out of equilibrium quantum field dynamics of an initial thermal state after a change in the external field

The effects of the initial temperature in the out of equilibrium quantum field dynamics in the presence of an homogeneous external field are investigated. We consider an initial thermal state of temperature T for a constant external field J. A subsequent sign flip of the external field, J to -J, gives rise to an out of equilibrium nonperturbative quantum field dynamics. The dynamics is studied here for the symmetry broken lambda(Phi^2)^2 scalar N component field theory in the large N limit. We find a dynamical effective potential for the expectation value that helps to understand the dynamics. The dynamics presents two regimes defined by the presence or absence of a temporal trapping close to the metastable equilibrium position of the potential. The two regimes are separated by a critical value of the external field that depends on the initial temperature. The temporal trapping is shorter for larger initial temperatures or larger external fields. Parametric resonances and spinodal instabilities amplify the quantum fluctuations in the field components transverse to the external field. When there is a temporal trapping this is the main mechanism that allows the system to escape from the metastable state for large N. Subsequently backreaction stops the growth of the quantum fluctuations and the system enters a quasiperiodic regime.Comment: LaTeX, 19 pages, 12 .eps figures, improved version to appear in Phys Rev

Counting Perfect Matchings and the Switch Chain

We examine the problem of exactly or approximately counting all perfect matchings in hereditary classes of nonbipartite graphs. In particular, we consider the switch Markov chain of Diaconis, Graham, and Holmes. We determine the largest hereditary class for which the chain is ergodic, and define a large new hereditary class of graphs for which it is rapidly mixing. We go on to show that the chain has exponential mixing time for a slightly larger class. We also examine the question of ergodicity of the switch chain in an arbitrary graph. Finally, we give exact counting algorithms for three classes

``Plug and play'' systems for quantum cryptography

We present a time-multiplexed interferometer based on Faraday mirrors, and apply it to quantum key distribution. The interfering pulses follow exactly the same spatial path, ensuring very high stability and self balancing. Use of Faraday mirrors compensates automatically any birefringence effects and polarization dependent losses in the transmitting fiber. First experimental results show a fringe visibility of 0.9984 for a 23km-long interferometer, based on installed telecom fibers.Comment: LaTex, 6 pages, with 2 Postscript figures, Submitted to Applied Physics Letter