Kyril Tintarev

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Let a be a quadratic form associated with a Schrödinger operator L = −∇ · (A∇) + V on a domain Ω ⊂ R d. If a is nonnegative on C ∞ 0 (Ω), then either there is W > 0 such that W |u| 2 dx ≤ a[u] for all C ∞ 0 (Ω; R), or there is a sequence ϕ k ∈ C ∞ 0 (Ω) and a function ϕ > 0 satisfying Lϕ = 0 such that a[ϕ k ] → 0, ϕ k → ϕ locally uniformly in Ω \ {x 0 }.(More)
Let Ω be a domain in R d , d ≥ 2, and 1 < p < ∞. Fix V ∈ L ∞ loc (Ω). Consider the functional Q and its Gâteaux derivative Q ′ given by Q(u) := Ω (|∇u| p +V |u| p)dx, 1 p Q ′ (u) := −∇·(|∇u| p−2 ∇u)+V |u| p−2 u. If Q ≥ 0 on C ∞ 0 (Ω), then either there is a positive continuous function W such that W |u| p dx ≤ Q(u) for all u ∈ C ∞ 0 (Ω), or there is a(More)
The paper studies the existence of minimizers for Rayleigh quotients µ Ω = inf Ω |∇u| 2 Ω V |u| 2 , where Ω is a domain in R N , and V is a nonzero nonnegative function that may have singularities on ∂Ω. As a model for our results one can take Ω to be a Lipschitz cone and V to be the Hardy potential V (x) = 1 |x| 2 .