arXiv subjects
Publications and source records attributed to Steven G. Krantz.
We construct new $3$-dimensional variants of the classical Diederich-Fornaess worm domain. We show that they are smoothly bounded, pseudoconvex, and have nontrivial Nebenhülle. We also show that their Bergman projections do not preserve the Sobolev space for sufficiently large Sobolev indices.
The Wong--Rosay theorem provides a characterization of the unit ball among all strongly pseudoconvex domains in terms of holomorphic automorphism group actions. We explore variants of this theorem in the quasiconformal setting.
Let $X$ be a complete measure space of finite measure. The Lebesgue transform of an integrable function $f$ on $X$ encodes the collection of all the mean-values of $f$ on all measurable subsets of $X$ of positive measure. In the problem of the differentiation of integrals, one seeks to recapture $f$ from its Lebesgue transform. In previous work we showed that, in all known results, $f$ may be recaputed from its Lebesgue transform by means of a limiting process associated to an appropriate family of filters defined on the collection of all measurable subsets of $X$ of positive measure. The first result of the present work is that the existence of such a limiting process is equivalent to the existence of a Von Neumann-Maharam lifting of $X$. In the second result of this work we provide an independent argument that shows that the recourse to filters is a \textit{necessary consequence} of the requirement that the process of recapturing $f$ from its mean-values is associated to a \textit{natural transformation}, in the sense of category theory. This result essentially follows from the Yoneda lemma. As far as we know, this is the first instance of a significant interaction between category theory and the problem of the differentiation of integrals. In the Appendix we have proved, in a precise sense, that \textit{natural transformations fall within the general concept of homomorphism}. As far as we know, this is a novel conclusion: Although it is often said that natural transformations are homomorphisms of functors, this statement appears to be presented as a mere analogy, not in a precise technical sense. In order to achieve this result, we had to bring to the foreground a notion that is implicit in the subject but has remained hidden in the background, i.e., that of \textit{partial magma}.
In this work we consider smooth unbounded worm domains $\mathcal Z_λ$ in $\mathbb C^2$ and show that the Bergman projection, densely defined on the Sobolev spaces $H^{s,p}(\mathcal Z_λ)$, $p\in(1,\infty)$, $s\ge0$, does not extend to a bounded operator $P_λ:H^{s,p}(\mathcal Z_λ)\to H^{s,p}(\mathcal Z_λ)$ when $s>0$ or $p\neq2$. The same irregularity was known in the case of the non-smooth unbounded worm. This improved result shows that the irregularity of the projection is not a consequence of the irregularity of the boundary but instead of the infinite windings of the worm domain.
In point of fact the Indian tradition in mathematics is long and glorious. It dates back to earliest times, and indeed many of the Indian discoveries from 5000 years ago correspond rather naturally to modern mathematical results.
In this article, we have described the Rao distance (due to C.R. Rao) and ideas of conformal mappings on 3D objects with angle preservations. Three propositions help us to construct distances between the points within the 3D objects in \mathbb{R}^{3} and line integrals within complex planes. We highlight the application of these concepts to virtual tourism.
In this paper we study the Bergman kernel and projection on the unbounded worm domain $$ \mathcal{W}_\infty = \big\{(z_1,z_2)\in\mathbb{C}^2 : \big|z_1-e^{i\log|z_2|^2}\big|^2<1, z_2\neq0\big\}. $$ We first show that the Bergman space of $\mathcal{W}_\infty$ is infinite dimensional. Then we study Bergman kernel $K$ and Bergman projection $\mathcal{P}$ for $\mathcal{W}_\infty$. We prove that $K(z,w)$ extends holomorphically in $z$ (and antiholomorphically in $w$) near each point of the boundary except for a specific subset that we study in detail. By means of an appropriate asymptotic expansion for $K$, we prove that the Bergman projection $\mathcal{P}:W^s\not\to W^s$ if $s>0$ and $\mathcal{P}:L^p\not\to L^p$ if $p\neq2$, where $W^s$ denotes the classic Sobolev space, and $L^p$ the Lebesgue space, respectively, on $\mathcal{W}_\infty$.
In this paper we are concerned with the problem of completeness in the Bergman space of the worm domain $\mathcal{W}_μ$ and its truncated version $\mathcal{W}'_μ$. We determine some orthogonal systems and show that they are not complete, while showing that the union of two particular of such systems is complete. In order to prove our completeness result we introduce the Muentz-Szasz problem for the 1-dimensional Bergman space of the disk $\{ζ: |ζ-1|<1\}$ and find a sufficient condition for its solution.
In the early 1960s, Brown and Mazur proved the general Jordan-Schoenflies theorem. This fundamental theorem states: If we embed an $(n-1)$ sphere $S^{(n-1)}$ locally flatly in an $n$ sphere $S^{n}$, then it decomposes $S^{n}$ into two components. In addition, the embedded $S^{(n-1)}$ is the common boundary of the two components and each component is homeomorphic to the $n$-ball.\newline This paper gives a constructive proof of the theorem using the discrete method. More specifically, we prove the equivalent statements: Let $M$ be an $n$-manifold, which is homeomorphic to $S^{n}$. Then, every $(n-1)$-manifold $S$, a submanifold with local flatness in $M$, decomposes the space $M$ into two components where each component is homeomorphic to an $n$-ball. The method was chosen in order to evaluate the computability and computational costs among operations between cells regarding homeomorphism. In addition, methods within the proof can be extended to applications in design algorithms under the assumption that homeomorphic mappings are constructible and computable. In this new revision, We add some new detailed discussions.
In this paper we establish an optimal Lorentz estimate for the Riesz potential in the $L^1$ regime in the setting of a stratified group $G$: Let $Q\geq 2$ be the homogeneous dimension of $G$ and $\mathcal{I}_α$ denote the Riesz potential of order $α$ on $G$. Then, for every $α\in (0,Q)$, there exists a constant $C=C(α,Q)>0$ such that \begin{align} \| \mathcal{I}_αf \|_{L^{Q/(Q-α),1}(G)} \leq C\| X \mathcal{I}_1 f \|_{L^1(G)} \end{align} for distributions $f$ such that $X \mathcal{I}_1 f \in L^1(G)$, where $X$ denotes the horizontal gradient.
If a bounded domain can be covered by the polydisk through a rational proper holomorphic map, then the Bergman projection is $L^p$-bounded for $p$ in a certain range depending on the ramified rational covering. This result can be applied to the symmetrized polydisk and to the Hartogs triangle with exponent $γ$.
In this paper, we have proposed a two phase procedure (combining discrete graphs and wavelets) for constructing a true epidemic growth. In the first phase graph theory based approach was developed to update partial data available and in the second phase we used this partial data to generate a plausible complete data through wavelets. This procedure although novel and implementable, still leave some questions unanswered.
We derive a sufficient condition on a bounded pseudoconvex domain $Ω\subset\mathbb{C}^2$ with smooth boundary such that $-(-ρ)^η$ is plurisubharmonic on $Ω$ for $η>0$ arbitrarily close to $1$ (the supremum of $η$ is called Diederich-Fornæss index, see Definition (df)). This condition (see Theorem prop) extends a theorem of Fornæss and Herbig in 2007 and only requires restriction on Levi-flat sets of the boundary $\partialΩ$. Since the condition is on Levi-flat sets, it contains more geometric information. As an application of this new condition, we discuss how the geometry of the Levi-flat sets affects the Diederich-Fornæss index. Among other results, we show that the Diederich-Fornæss index is $1$ if only the Levi-flat sets form a real curve transversal to the holomorphic tangent vector fields on $\partialΩ$ (see Theorem [main]). We also give a specific example (see Theorem [example]) on the bounded pseudoconvex domains which verify the application but are neither of finite type nor admit a plurisubharmonic defining function on the boundary.
This is a tract on the art and practice of mathematical writing. Not only does the book cover basic principles of grammar, syntax, and usage, but it takes into account developments of the last twenty years that have been inspired by the Internet. There is considerable discussion of TeX and other modern writing environments. We also consider electronic journals, print-on-demand books, Open Access Journals, preprint servers, and many other aspects of modern publishing life.
We study boundary uniqueness properties of Hardy space functions in several complex variables. Along the way, we develop properties of the Lumer Hardy space.
We study the connection between weighted Bergman kernel and Green's function on a domain W lying in C for which the Green's function exists.
We consider the following conjecture (from Huang, et al): Let $Δ^+$ denote the upper half disc in $\mathbb{C}$ and let $γ= ( - 1, 1)$ (viewed as an interval in the real axis in $\mathbb{C}$). Assume that $F$ is a holomorphic function on $Δ^+$ with continuous extension up to $γ$ such that $F$ maps $γ$ into $\{|\mbox{Im} z|\leq C|\mbox{Re} z|\},$ for some positive $C.$ If $F$ vanishes to infinite order at $0$ then $F$ vanishes identically. We show that given the conditions of the conjecture, either $F\equiv 0$ or there is a sequence in $Δ^+$, converging to $0,$ along which $\mbox{Im} F/\mbox{Re} F$ (defined where $\mbox{Re} F\neq 0$) is unbounded.
Under a plausible geometric hypothesis, we show that a biholomorphic mapping of smoothly bounded, pseudoconvex domains extends to a diffeomorphism of the closures.