A remark on four-dimensional almost Kähler-Einstein manifolds with negative scalar curvature
Concerning the Goldberg conjecture, we will prove a result obtained by applying the result of Iton in terms of L2-norm of the scalar curvature.
Notes on the Goldberg Conjecture in Dimension Four
Concerning the integrability of almost Kahler manifolds, there is a longstanding conjecture by S.I. Goldberg, “A compact almost Kahler Einstein manifold is Kahler”. The conjecture is true in the case where the scalar curvature is non-negative. However, the conjecture is still open in the remaining case. In this note, we shall give a brief survey on the recent progress concerning the conjecture in four-dimensional case.
Photoreflectance characterization of vanadium-doped GaAs layers grown by metalorganic vapor phase epitaxy
Abstract We characterized the vanadium-doped (GaAs:V) layers grown on GaAs substrate by metalorganic vapor phase epitaxy. The conductivity of the samples is checked by the Hall effect measurements, and it is n type with electrons concentration ranging from 2×10 13 to 2×10 17  cm −3 . We used the photoreflectance technique (PR) to study the effect of vanadium doping on the optical properties of GaAs. Our experimental results show that the built-in electric field F and the broadening parameter Γ 0 increase with V-doping concentration. Furthermore, the temperature dependence of the built-in electric field and the broadening parameter of GaAs:V samples have been investigated by PR. It has been observed that these parameters increase with increasing temperature. The decrease of the built-in electric field with decreasing temperature is due to the photovoltage effect.We characterized the vanadium-doped GaAs (GaAs:V) layers grown on GaAs substrate by metalorganic vapor phase epitaxy.