Self-interaction errors in nuclear energy density functionals

When applied to a single nucleon, nuclear energy density functionals may yield a non-vanishing internal energy thus implying that the nucleon is interacting with itself. It is shown how to avoid this unphysical feature for semi-local phenomenological functionals containing all possible bilinear combinations of local densities and currents up to second order in the derivatives. The method outlined in this Rapid Communication could be easily extended to functionals containing higher order terms, and could serve as a guide for constraining the time-odd part of the functional

Multispectral scanner optical system

An optical system for use in a multispectral scanner of the type used in video imaging devices is disclosed. Electromagnetic radiation reflected by a rotating scan mirror is focused by a concave primary telescope mirror and collimated by a second concave mirror. The collimated beam is split by a dichroic filter which transmits radiant energy in the infrared spectrum and reflects visible and near infrared energy. The long wavelength beam is filtered and focused on an infrared detector positioned in a cryogenic environment. The short wavelength beam is dispersed by a pair of prisms, then projected on an array of detectors also mounted in a cryogenic environment and oriented at an angle relative to the optical path of the dispersed short wavelength beam

Nonplanar integrability at two loops

In this article we compute the action of the two loop dilatation operator on restricted Schur polynomials that belong to the su(2) sector, in the displaced corners approximation. In this non-planar large N limit, operators that diagonalize the one loop dilatation operator are not corrected at two loops. The resulting spectrum of anomalous dimensions is related to a set of decoupled harmonic oscillators, indicating integrability in this sector of the theory at two loops. The anomalous dimensions are a non-trivial function of the 't Hooft coupling, with a spectrum that is continuous and starting at zero at large N, but discrete at finite N.Comment: version to appear in JHE

A double coset ansatz for integrability in AdS/CFT

We give a proof that the expected counting of strings attached to giant graviton branes in AdS_5 x S^5, as constrained by the Gauss Law, matches the dimension spanned by the expected dual operators in the gauge theory. The counting of string-brane configurations is formulated as a graph counting problem, which can be expressed as the number of points on a double coset involving permutation groups. Fourier transformation on the double coset suggests an ansatz for the diagonalization of the one-loop dilatation operator in this sector of strings attached to giant graviton branes. The ansatz agrees with and extends recent results which have found the dynamics of open string excitations of giants to be given by harmonic oscillators. We prove that it provides the conjectured diagonalization leading to harmonic oscillators.Comment: 33 pages, 3 figures; v2: references adde

Self consistent kinetic simulations of SPT and HEMP thrusters including the near-field plume region

The Particle-in-Cell (PIC) method was used to study two different ion thruster concepts - Stationary Plasma Thrusters (SPT) and High Efficiency Multistage Plasma Thrusters (HEMP-T), in particular the plasma properties in the discharge chamber due to the different magnetic field configurations. Special attention was paid to the simulation of plasma particle fluxes on the thrusters channel surfaces. In both cases, PIC proved itself as a powerful tool, delivering important insight into the basic physics of the different thruster concepts. The simulations demonstrated that the new HEMP thruster concept allows for a high thermal efficiency due to both minimal energy dissipation and high acceleration efficiency. In the HEMP thruster the plasma contact to the wall is limited only to very small areas of the magnetic field cusps, which results in much smaller ion energy flux to the thruster channel surface as compared to SPT. The erosion yields for dielectric discharge channel walls of SPT and HEMP thrusters were calculated with the binary collision code SDTrimSP. For SPT, an erosion rate on the level of 1 mm of sputtered material per hour was observed. For HEMP, thruster simulations have shown that there is no erosion inside the dielectric discharge channel.Comment: 14 pages, 11 figures This work was presented at 21st International Conference on Numerical Simulation of Plasmas (ICNSP'09

A stereoscopic ranging system using standard PC technology

A stereoscopic ranging system is currently being developed as a key source of positional information for an underwater ROV station keeping system. Advancements in PC technology make it possible to use a relatively simple image capture card and a PC as a platform for the fast capture and processing of video images. We make use of the extensive capabilities of fast data buses and the high processing power of fast PCs with Pentium II or III processors. Using this approach we are developing an image processing system that is largely manufacturer independent and promises a good path for both hardware and software upgrading in the future

Random access quantum information processors

Qubit connectivity is an important property of a quantum processor, with an ideal processor having random access -- the ability of arbitrary qubit pairs to interact directly. Here, we implement a random access superconducting quantum information processor, demonstrating universal operations on a nine-bit quantum memory, with a single transmon serving as the central processor. The quantum memory uses the eigenmodes of a linear array of coupled superconducting resonators. The memory bits are superpositions of vacuum and single-photon states, controlled by a single superconducting transmon coupled to the edge of the array. We selectively stimulate single-photon vacuum Rabi oscillations between the transmon and individual eigenmodes through parametric flux modulation of the transmon frequency, producing sidebands resonant with the modes. Utilizing these oscillations for state transfer, we perform a universal set of single- and two-qubit gates between arbitrary pairs of modes, using only the charge and flux bias of the transmon. Further, we prepare multimode entangled Bell and GHZ states of arbitrary modes. The fast and flexible control, achieved with efficient use of cryogenic resources and control electronics, in a scalable architecture compatible with state-of-the-art quantum memories is promising for quantum computation and simulation.Comment: 7 pages, 5 figures, supplementary information ancillary file, 21 page

Solving Four Dimensional Field Theories with the Dirichlet Fivebrane

The realization of ${\cal N}=2$ four dimensional super Yang-Mills theories in terms of a single Dirichlet fivebrane in type IIB string theory is considered. A classical brane computation reproduces the full quantum low energy effective action. This result has a simple explanation in terms of mirror symmetry.Comment: Final version to appear in Phys. Rev.

Probing the mechanical unzipping of DNA

A study of the micromechanical unzipping of DNA in the framework of the Peyrard-Bishop-Dauxois model is presented. We introduce a Monte Carlo technique that allows accurate determination of the dependence of the unzipping forces on unzipping speed and temperature. Our findings agree quantitatively with experimental results for homogeneous DNA, and for $\lambda$-phage DNA we reproduce the recently obtained experimental force-temperature phase diagram. Finally, we argue that there may be fundamental differences between {\em in vivo} and {\em in vitro} DNA unzipping

Pion-nucleon scattering in a meson-exchange model

The pi-N interaction is studied within a meson-exchange model and in a coupled-channels approach which includes the channels pi-N, eta-N, as well as three effective pi-pi-N channels namely rho-N, pi-Delta, and sigma-N. Starting out from an earlier model of the Julich group systematic improvements in the dynamics and in some technical aspects are introduced. With the new model an excellent quantitative reproduction of the pi-N phase shifts and inelasticity parameters in the energy region up to 1.9 GeV and for total angular momenta J leq 3/2 is achieved. Simultaneously, good agreement with data for the total and differential pi-N -> eta-N transition cross sections is obtained. The connection of the pi_N dynamics in the S_{11} partial wave with the reaction pi-N -> eta-N is discussed.Comment: 32 pages, 9 figure