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We suppose that the solar neutrino problem is due only to the mechanism introduced by Ellis, Hagelin, Nanopoulos and Srednicki (EHNS) to allow pure quantum states to evolve into mixed ones. Lower limits on the EHNS parameters (α, β, γ ) are obtained. We find that γ 7.4 × 10 −22 GeV if α < 2γ and α 1.5 × 10 −21 GeV if α > 2γ , with no constraint on β. This limit is consistent with the upper limits extracted from the K 0 − K 0 system and can be detected in future experiments.

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In the light of the recent Lin, Lunin, Maldacena (LLM) results, we investigate 1/2-BPS geometries in minimal (and next to minimal) supergravity in D = 6 dimensions. In the case of minimal supergravity, solutions are given by fibrations of a two-torus T 2 specified by two harmonic functions. For a rectangular torus the two functions are related by a non-linear equation with rare solutions: AdS 3 × S 3 , the pp-wave and the multicenter string. "Bubbling", i.e. superpositions of droplets, is accommodated by allowing the complex structure of the T 2 to vary over the base. The analysis is repeated in the presence of a tensor multiplet and similar conclusions are reached, with generic solutions describing D1D5 (or their dual fundamental string-momentum) systems. In this framework, the profile of the dual fundamental string-momentum system is identified with the boundaries of the droplets in a two-dimensional plane.

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