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It is shown that scalar particle creation in the gravitational field of a massive object could OCCUI even if the radius of the object is larger than the Schwarzschild radius. Scalar field condensation could change the metric drastically, and decrease the observable mass of the system.

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The importance of reducing the neutral density to reach strong drift wave turbulence is clarified from the results of the extended magnetohydrodynamics and Monte Carlo simulations in a linear magnetized plasma. An upper bound of the neutral density relating to the ion-neutral collision frequency for the excitation of drift wave instability is shown, and the necessary flow velocity to excite this instability is also estimated from the neutral distributions. Measurements of the Mach number and the electron density distributions using Mach probe in the large mirror device ͑LMD͒ of Kyushu University ͓S. Shinohara et al., Plasma Phys. Control. Fusion 37, 1015 ͑1995͔͒ are reported as well. The obtained results show a controllability of the neutral density and provide the basis for neutral density reduction and a possibility to excite strong drift wave turbulence in the LMD.