Sharp resolvent bounds for non-selfadjoint semiclassical elliptic quadratic differential operators are established, in the interior of the range of the associated quadratic symbol.
We study the resolvent norm of a certain class of closed linear operators on a Hilbert space, including unbounded operators with compact resolvent. It is shown that for any point in the resolvent set there exist directions in which the norm grows at least quadratically with the distance from this point. This provides a new proof not using the maximum principle that the resolvent norm of the considered class cannot have local maxima. Finally, we give new criteria for the existence of local non-degenerate minima of the resolvent norm and provide examples of (un)bounded non-normal operators havin…
We consider an arbitrary metric graph, to which we glue another graph with edges of lengths proportional to $\varepsilon$, where $\varepsilon$ is a small positive parameter. On such graph, we consider a general self-adjoint second order differential operator $\mathcal{H}_\varepsilon$ with varying coefficients subject to general vertex conditions; all coefficients in differential expression and vertex conditions are supposed to be analytic in $\varepsilon$. We introduce a special operator on a certain graph obtained by rescaling the aforementioned small edges and assume that it has no embedded …
In this article we study the semiclassical resolvent estimate for the non-selfadjoint Baouendi-Grushin operator on the two-dimensional torus $\mathbb{T}^2=\mathbb{R}^2/(2π\mathbb{Z})^2$ with Hölder dampings. The operator is subelliptic degenerating along the vertical direction at $x=0$. We exhibit three different situations: (i) the damping region verifies the geometric control condition with respect to both the non-degenerate Hamiltonian flow and the vertical subelliptic flow; (ii) the undamped region contains a horizontal strip; (iii) the undamped part is a line. In all of these situations, …
Resolvent Positive Linear Operators Exhibit the Reduction Phenomenon
Kato证明了预解式正线性算子A和乘法算子V的组合的谱界s(aA + bV)在b \in R中是凸的.这里通过一个初等引理表明,s(a A + b V)在a > 0时也是凸的,并且值得注意的是,当存在时,\partial s(a A + b V)/ \partial a <= s(A)。扩散通常具有s(A)<= 0,使得对于具有空间异质生长或衰减速率的扩散,更大的混合减少生长。当A是拉普拉斯算子或二阶椭圆算子,或非局部扩散算子时,扩散演化的模型特别发现了这个结果,这意味着选择减少扩散。这些情况在这里被证明是一个单一的、广泛的、“减少”现象的一部分。
Based on the notion of the resolvent and on the Hilbert identities, this paper presents a number of classical results in the theory of differential operators and some of their applications to the theory of automorphic functions and number theory from a unified point of view. For instance, for the Sturm-Liouville operator there is a derivation of the Gelfand-Levitan trace formula, and for the one-dimensional Schroedinger operator a derivation of Faddeev's formula for the characteristic determinant and the Zakharov-Faddeev trace identities. Recent results on the spectral theory of a certain func…