We review the derivation of a noncommutative version of the nonlinear sigma model on CP n and it's soliton solutions for finite θ emphasizing the similarities it bears to the GMS scalar field theory. It is also shown that unlike the scalar theory, some care needs to be taken in defining the topological charge of BPS solitons of the theory due to nonvanishing surface terms in the energy functional. Finally it is shown that, like its commutative analogue, the noncommutative CP n -model also exhibits a non-BPS sector. Unlike the commutative case however, there are some surprises in the noncommutative case that merit further study.
Optical absorption is investigated for SiC crystals irradiated with 7 MeV electrons. The band gap of the specimen is found to be narrowed from 3.01 eV before irradiation to 2.81 eV after irradiation with 3 × 1018 electrons/cm2. It is recovered to 2.99 eV by isochronal annealing up to 1000 °C for 30 minutes in hydrogen atmosphere. Two annealing stages are observed at around 150 and 650 °C. The activation energies of the recovery for the two stages are estimated to be about 0.16 and 1.3 eV, respectively.
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Deep level centers in silicon introduced by high-energy He irradiation and subsequent annealingThe n-type silicon crystals of about 0.15, 0.9, and 10 ncm (pulled material) and 120 ncm (float-zone material) are exposed to 2-9-MeV electron beams at total integrated fluxes up to about 10 18 electrons/cm 2 • The production rates of each complex defect in irradiated silicon are investigated. They are obtained from the condition of charge neutrality by using the experimental values of the resistivity as a function of bombardment dose. The electron energy dependence and the impurity density dependence of the production rate are determined for each complex defect. The results suggest that a configuration of the defect states at E, -0.3 eV may be associated with a phosphorus atom, and in the intrinsic region the two occupied and vacant states should be symmetrically located above and below the middle of the energy gap, respectively.
The depth distribution of the radiation dcfects in n‐type silicon are approximately determined from the measured values of the resistivity versus depth curve by using the production rates of each defect obtained in a previous paper for 2, 3.9, 4.5, 7, and 9 MeV electrons. The observed elec‐tron ranges are in good agreement with the theoretical values of Berger and Seltzer. The defect distribution can be qualitatively interprctcd by tsking into account the energy spectra of electrons at various depths and the production rate of defects. The total nnmbers of vacancy‐related defects Nt produced by electron irradiation at depths from zero to the maximum one at which the resistiv‐ity changes arc estimated. The energy dependence of Nt are fairly well explained by applying Cahn's theory.
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