“…, d − 1 (their notation) = n (ours); see also Theorem 2 and Proposition 2.1 of [3]. When D 2 P is positive definite, we can complement Corollary 1.3 with Du and Zhang's deep result in Theorem 2.4 of [18], so that…”
Section: Introductionmentioning
confidence: 88%
“…where we assume that 1 ≤ m ≤ n/2 without loss of generality. These symbols were also extensively studied in [3], where several positive and negative results were established. By (2), we only need to work with α > n/2.…”
Section: (Iii)mentioning
confidence: 99%
“…When P is a non-elliptic quadratic symbol, this result was already proved in Theorem 1, eq. ( 4) of [3]. To compare their results with ours, the reader can use the identity…”
We study the problem of pointwise convergence for equations of the type i ∂tu + P (D)u = 0, where the symbol P is real, homogeneous and non-singular. We prove that for initial data f ∈ H s (R n ) with s > (n − α + 1)/2 the solution u converges to f H α -a.e, where H α is the αdimensional Hausdorff measure. We improve upon this result depending on the dispersive strength of the symbol. On the other hand, we prove negative results for a large family of polynomial symbols P . Given α, we exploit a Talbot-like effect to construct regular initial data whose solutions u diverge in sets of Hausdorff dimension α. We also construct data for quadratic symbols like the saddle to show that our positive results are sometimes best possible. To compute the dimension of the sets of divergence we use a Mass Transference Principle from Diophantine approximation theory.
“…, d − 1 (their notation) = n (ours); see also Theorem 2 and Proposition 2.1 of [3]. When D 2 P is positive definite, we can complement Corollary 1.3 with Du and Zhang's deep result in Theorem 2.4 of [18], so that…”
Section: Introductionmentioning
confidence: 88%
“…where we assume that 1 ≤ m ≤ n/2 without loss of generality. These symbols were also extensively studied in [3], where several positive and negative results were established. By (2), we only need to work with α > n/2.…”
Section: (Iii)mentioning
confidence: 99%
“…When P is a non-elliptic quadratic symbol, this result was already proved in Theorem 1, eq. ( 4) of [3]. To compare their results with ours, the reader can use the identity…”
We study the problem of pointwise convergence for equations of the type i ∂tu + P (D)u = 0, where the symbol P is real, homogeneous and non-singular. We prove that for initial data f ∈ H s (R n ) with s > (n − α + 1)/2 the solution u converges to f H α -a.e, where H α is the αdimensional Hausdorff measure. We improve upon this result depending on the dispersive strength of the symbol. On the other hand, we prove negative results for a large family of polynomial symbols P . Given α, we exploit a Talbot-like effect to construct regular initial data whose solutions u diverge in sets of Hausdorff dimension α. We also construct data for quadratic symbols like the saddle to show that our positive results are sometimes best possible. To compute the dimension of the sets of divergence we use a Mass Transference Principle from Diophantine approximation theory.
“…I am not aware of such results. However, in addition to the spherical averages (discussed in Section 4), which have been studied for a long time, there are recent estimates for cones and hyperboloids; see [2], [13], and [1].…”
For Sg(x, y) = x − g(y), x, y ∈ R n , g ∈ O(n), we investigate the Lebesgue measure and Hausdorff dimension of Sg(A) given the dimension of A, both for general Borel subsets of R 2n and for product sets.
“…where L : R n−1 → R n−1 is an invertible, self-adjoint linear mapping of signature σ . This prototypical case is essentially treated in [2] (see also [11]) but, for completeness, the details are given.…”
The sharp range of $$L^p$$
L
p
-estimates for the class of Hörmander-type oscillatory integral operators is established in all dimensions under a general signature assumption on the phase. This simultaneously generalises earlier work of the authors and Guth, which treats the maximal signature case, and also work of Stein and Bourgain–Guth, which treats the minimal signature case.
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