Summing Planar Diagrams by an Integrable Bootstrap

Correlation functions of matrix-valued fields are not generally known for massive renormalized field theories. We find the large-N limit of form factors of the (1+1)-dimensional sigma model with SU(N) X SU(N) symmetry. These form factors give a correction to the free-field approximation for the N=infinity Wightman function. The method is a combination of the 1/N-expansion of the S-matrix and Smirnov's form-factor axioms. We expand the renormalized field in terms of a free massive Bosonic field as N goes to infinity.Comment: 10 pages, revtex. Fixing of further misprints. Version to appear in Phys. Rev.

Mode Competition in Relativistic Magnetrons and Injection Locking in KW Magnetrons

Both relativistic and nonrelativistic magnetrons are under experimental and theoretical investigation at U of M. Relativistic (Titan‐6‐vane) magnetron experiments (300–400 kV, 1–10 kA, 0.5 microsecond) investigate mode control with various output coupling geometries. Mode competition between the pi mode and the 2/3 pi mode has been characterized for two‐versus‐three output extractors for comparison with particle in cell simulations. Phase measurements and time‐frequency‐analysis are performed for mode identification. Peak microwave output power on the order 0.5 GW has been measured, assuming equal output from 3 waveguides. Nonrelativistic (4 kV, <1A, kW microwave power) magnetron experiments are performed on commercial oven magnetrons for an in‐depth investigation of crossed‐field injection‐locking and noise. Injection‐locking is demonstrated by utilizing an oven magnetron as a reflection amplifier. Noise generation is explored as a function of injected signal and cathode conditions. © 2003 American Institute of PhysicsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87505/2/301_1.pd

Progress in Parallelizing XOOPIC

X11-based Unix computers) is presently a serial 2d 3v particle-in-cell plasma simulation. This effort focuses on using parallel and distributed processing to optimize the simulation for large problems. The benefits include increased capacity for memory intensive problems, and improved performance for processor-intensive problems. The MPI library enables the parallel version to be easily ported to massively parallel, SMP, and distributed computers. The philosophy employed here is to spatially decompose the system into computational regions separated by “virtual boundaries”, objects which contain the local data and algorithms to perform the local field solve and particle communication between regions. This implementation reduces the impact of the parallel extension on the balance of the code. Specific implementation details such as the hiding of communication latency behind local computation will also be discussed, as well as code features and capabilities. 1 GOALS FOR PARALLEL XOOPIC XOOPIC has been successful as a single-processor code, and is able to simulate many interesting devices including relativistic klystron oscillators, electron guns, DC discharges with gas chemistry, plasma display panel cells, and highly relativistic beams in accelerators. However, particle-in-cell simulations are very computationally intensive, and on a single processor, some problems may take months to complete. The goals, therefore, for parallel XOOPIC are: Reduce run-times for large, complex simulations from weeks to days. Distribute memory demands across machines, allowing larger simulations than possible otherwise. Cross platform portability (networks of workstations, massively parallel machines, and SMP machines). Identical usage and feature set for parallel and nonparallel versions of XOOPIC, and largely shared source code. Complete source code availability to the general public

Kabul Times. (Kabul, Afghanistan), 1978-10-26

Kabul Times. (Kabul, Afghanistan), 1978-10-26; Volume 17; Number 17