Natural boundaries and rational approximants

The use of rational approximants to simulate the natural boundary of a function is examined. Determination of the poles of the approximants illustrates the enormous power of the MATHEMATICA computer package.     

Quantum nonlocality and beyond: limits from nonlocal computation

We address the problem of "nonlocal computation," in which separated parties must compute a function without any individual learning anything about the inputs. Surprisingly, entanglement provides no benefit over local classical strategies for such tasks, yet stronger nonlocal correlations allow perfect success. This provides intriguing insights into the limits of quantum information processing, the nature of quantum nonlocality, and the differences between quantum and stronger-than-quantum nonlocal correlations.     

Monitor for displaying real-time images of low energy ion beams

Analytical Chemistry Division. Oak Ridge National Laboratory. Oak Ridge, Tennessee, USA A monitor that provides real-time images of low energy (< 50 eV) ion beams has been designed, constructed, and tested. The cross-sectional image of the beam at the entrance aperture of the monitor is magnified by a factor of 6.5 and displayed on a CRT, following current amplification by using a dual microchannel plate assembly. The monitor provides unambiguous information regarding the cross section of any low energy ion beam. Anplication in the design and testing of quadrupole-based mass spectrometers is emphasized,     

Time-dependent electron thermal flux inhibition in direct-drive laser implosions

We simulate direct-drive CH target implosions with square laser pulses by a one-dimensional Fokker-Planck solver combined with a hydrodynamic code, and compare the results with those simulated by the flux-limited Spitzer-H?rm model. We find that the electron thermal flux inhibition is time dependent, resulting in longer density scale length, larger laser absorption, and smaller growth of Rayleigh-Taylor instability. The time of peak neutron production calculated from Fokker-Planck simulations agrees with experiments for both 1-ns and 400-ps pulses.     

Local distinguishability of multipartite orthogonal quantum states

We consider one copy of a quantum system prepared in one of two orthogonal pure states, entangled or otherwise, and distributed between any number of parties. We demonstrate that it is possible to identify which of these two states the system is in by means of local operations and classical communication alone. The protocol we outline is both completely reliable and completely general; it will correctly distinguish any two orthogonal states 100% of the time.     

Unsolvable Problems About Small Cancellation and Word Hyperbolic Groups

We apply a construction of Rips to show that a number of algorithmicproblems concerning certain small cancellation groups and, inparticular, word hyperbolic groups, are recursively unsolvable.Given any integer k > 2, there is no algorithm to determinewhether or not any small cancellation group can be generatedby either two elements or more than k elements. There is a smallcancellation group E such that there is no algorithm to determinewhether or not any finitely generated subgroup of E is all ofE, or is finitely presented, or has a finitely generated secondintegral homology group.     

New methods for determining the thermal activation energies of light sensitive traps

Two methods have been developed for determining the thermal activation energies of light sensitive traps in systems with either one or two trap types and a single type of recombination centre. No assumptions about the kinetic order are needed for the methods to be successful, although the two- trap case requires sufficient difference in trap activation energies. There is potential to apply the methods to more complex systems, and the theory is readily transferred to the traps used in ESR.