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We prove that the core of a complex manifold X is the union of pairwise disjoint pseudoconcave sets on which all uniformly bounded continuous plurisubharmonic functions on X are constant. Similarly, the minimal kernel of a weakly complete complex manifold decomposes into the union of compact pseudoconcave sets on which all continuous plurisub-harmonic functions are constant. Versions of these results for standard smoothness classes are obtained. Analogous facts are discussed in the context of Richberg's regularization of continuous strongly plurisubharmonic functions.
Proceedings of the American Mathematical Society, 2019
Let M be a complex manifold and P SH cb (M) be the space of bounded continuous plurisubharmonic functions on M. In this paper we study when the functions from P SH cb (M) separate points. Our main results show that this property is equivalent to each of the following properties of M : (1) the core of M is empty. (2) for every w 0 ∈ M there is a continuous plurisubharmonic function u with the logarithmic singularity at w 0. Moreover, the core of M is the disjoint union of the sets E j that are 1-pseudoconcave in the sense of Rothstein and have the following Liouville property: every function from P SH cb (M) is constant on each of E j .
Izvestiya: Mathematics, 2021
We give a geometric condition on a compact subset of a complex manifold which is necessary and sufficient for the existence of a smooth strictly plurisubharmonic function defined in a neighbourhood of this set.
Mathematische Annalen, 1998
Let Ω be a domain in C n. An upper semicontinuous function u : Ω → [−∞, ∞) is said to be plurisubharmonic if the restriction of u to each complex line is subharmonic (we allow the function identically −∞ to be plurisubharmonic). We say that u is strictly plurisubharmonic if for every z 0 ∈ Ω there is a neigbourhood U of z 0 and λ > 0 such that u(z) − λ|z| 2 is plurisubharmonic on U. We write PSH(Ω) for the set of plurisubharmonic functions on Ω, PSH − (Ω) for the subset of bounded from above and PSH c (Ω) for the set of continuous functions on Ω which are plurisubharmonic on Ω. It is a natural question whether it is possible to approximate elements of one of these classes by elements of a smaller one. It may be useful to recall some known facts regarding this problem. Richberg [5] showed that for every strictly plurisubharmonic continuous function u on Ω and every positive continuous function ε on Ω, there exists a C ∞ smooth strictly plurisubharmonicũ on Ω such that 0 < u −ũ < ε on Ω. Later, Fornaess and Narasimhan proved that every plurisubharmonic function u on a pseudoconvex domain Ω can be approximated from above by a sequence of C ∞ smooth strictly plurisubharmonic functions. A remarkable example of Fornaess [1] shows that the above conclusion fails without the assumption on pseudoconvexity of Ω. In fact, the domain Ω in Fornaess'example is a smoothly bounded Hartogs domain in C 2. Recall that Ω is said to be Hartogs if (z, w) ∈ Ω ⇒ (z, w) ∈ Ω provided that |w| = |w |. Regarding approximation on smoothly bounded domain, Fornaess and Wiegerinck [2] proved that every continuous function on Ω which is plurisubharmonic on Ω, can be approximated uniformly on Ω by C ∞ smooth plurisubharmonic functions on neigbourhoods of Ω. Besides, Fornaess and Wiegerinck show that every plurisubharmonic function u on a bounded Reinhardt domain Ω can be approximated from above by a sequence of smooth strictly plurisubharmonic functions on Ω. Recall that Ω is said to be Reinhardt if (z 1 , • • • , z n) ∈ Ω ⇒ (z 1 , • • • , z n) ∈ Ω provided that |z i | = |z i | for every 1 i n. This result is very interesting in comparison with the mentioned above example of Fornaess. The aim of the present paper is to study the problem of approximation on Ω of the upper regularization u * of a given function u ∈ PSH − (Ω) by elements in PSH c (Ω), where u * (z) = limsup ξ→z u(ξ). This problem has been considered by in [7]
Cornell University - arXiv, 2022
Replying to three questions posed by N. Shcherbina, we show that a compact psudoconcave set can have the core smaller than itself, that the core of a compact set must be pseudoconcave, and that it can be decomposed into compact pseudoconcave sets on which all smooth plurisubharmonic functions are constant.
Nagoya Mathematical Journal, 1998
It is proved that the C 2-smoothly bounded pseudoconvex domains in P n admit bounded plurisubharmonic exhaustion functions. Further arguments are given concerning the question of existence of strictly plurisubharmonic functions on neighbourhoods of real hypersurfaces in F n. Let Ω (c M be a pseudoconvex domain in a Kahler manifold M. When M is P fc , Takeuchi [T], showed that the function-log<5^ is strictly plurisubharmonic (p.s.h.) in Ω. Here SQ denotes the distance to the boundary for the standard Kahler metric on Ψ k. The result was extended by Elencwajg [E] to the case where M is Kahler with strictly positive holomorphic bisectional curvature. See also Suzuki [Su] and Green-Wu [G.W]. Based on their result we show that if Ω <ε M is pseudoconvex with C 2 boundary, then there is a bounded strictly p.s.h. function on Ω. When M-C k the question was solved by Diedrich-Fornaess [D.F]. For a survey in this case see [S]. We give an example of a compact Kahler manifold M, containing a Stein domain Ω d M, with smooth boundary, however given any neighborhood U of 9Ω, there is no nonconstant bounded p.s.h. function on U Π Ω. We show next that the existence of a strictly p.s.h. function near dΩ is equivalent to the nonexistence of a positive current T of bidimension (1,1) supported on dΩ and satisfying the equation ddT = 0. This result is inspired by a duality argument due to Sullivan [Su]. §1. Plurisubharmonic exhaustion function on smoothly bounded domains Let (M,ω) be a Kahler manifold. Let Ω d M be a pseudoconvex domain with smooth boundary. We consider first the question of existence of a strictly plurisubharmonic bounded exhaustion function for Ω.
Development of Mathematics, 1950–2000, 2000
A contribution to the book project Développement des mathématiques au cours de la seconde moitié du XX e siècle Development of mathematics 1950-2000, edited by Jean-Paul Pier Christer O. Kiselman Contents: 1. Introduction 2. Setting the stage 3. The emergence of plurisubharmonic functions 4. Domains of holomorphy and pseudoconvex domains 5. Integration on analytic varieties 6. Weighted estimates for the Cauchy-Riemann operator 7. Small sets: pluripolar sets and negligible sets 8. The analogy with convexity 9. Lelong numbers 10. The growth at infinity of entire functions 11. The existence of a tangent cone 12. The complex Monge-Ampère operator 13. The global extremal function 14. The relative extremal function 15. Green functions 16. Plurisubharmonic functions as lower envelopes References Resumo: Plursubharmonaj funkcioj kaj potenciala teorio en pluraj kompleksaj variabloj Ni prezentos superrigardon de la evoluigo de la teorio pri plursubharmonaj funkcioj kaj la potenciala teorio ligita al ili ekde ilia difino en 1942ĝis 1997.
Potential Analysis, 2008
Edlund, T. 2005. Pluripolar sets and pluripolar hulls. Acta Universitatis Upsaliensis. Uppsala Dissertations in Mathematics 41. vii, 23 pp. Uppsala. ISBN 91-506-1812-1
Journal of Mathematical Analysis and Applications, 2011
A weak and a strong concept of plurifinely plurisubharmonic and plurifinely holomorphic functions are introduced. Strong will imply weak. The weak concept is studied further. A function f is weakly plurifinely plurisubharmonic if and only if f • h is finely subharmonic for all complex affine-linear maps h. As a consequence, the regularization in the plurifine topology of a pointwise supremum of such functions is weakly plurifinely plurisubharmonic, and it differs from the pointwise supremum at most on a pluripolar set. Weak plurifine plurisubharmonicity and weak plurifine holomorphy are preserved under composition with weakly plurifinely holomorphic maps.
The Michigan Mathematical Journal, 2006
N g u y e n Q uang D i e u 1. Introduction Let be a domain in C n. An upper semicontinuous function u : → [−∞, ∞) is said to be plurisubharmonic if the restriction of u to each complex line is subharmonic (we allow the function identically −∞ to be plurisubharmonic). We write PS H() for the set of plurisubharmonic functions on , PS H − () for the set of plurisubharmonic functions bounded from above on , and PS H(¯) for the set of plurisubharmonic functions on neighborhoods of¯. If u is a function bounded from above on , then by u * we mean the upper regularization of u; that is, if z ∈¯ then u * (z) = lim sup ξ →z u(ξ). For a given point z ∈¯ , we define the following class of Jensen measures: J 1 z (¯) = µ ∈ B(¯) : u * (z) ≤ ¯ u * dµ ∀u ∈ PS H − () , where B(¯) is the set of positive regular Borel measures with mass 1 on¯. We can define J 2 z and J 3 z analogously when PS H − () is replaced by PS H c () (the set of plurisubharmonic functions on , continuous on¯) and PS H c (¯) (the set of continuous functions on¯ that are uniform limits of continuous functions in PS H(¯)), respectively. For simplicity of notation, we will write J i z instead of J i z (¯) if there is no risk of confusion. It is obvious that δ z ∈ J 1 z ⊂ J 2 z ⊂ J 3 z , where δ z is the Dirac measure at z. With a little more effort, one can prove that each J i z is a closed convex subset of B(¯). We say that is J-regular if J 1 z = J 3 z for all z ∈. The classes J 1 z , J 2 z , J 3 z are introduced and studied extensively in [CCeW; DW; P; S2; W1; W2] and elsewhere. The main reason for introducing them is a duality theorem of Edwards that allows us to express upper envelopes of plurisubharmonic functions as lower envelopes of integrals with respect to Jensen measures. Since the traditional method of constructing plurisubharmonic functions has been to take envelopes over classes of plurisubharmonic functions, Edwards's duality theorem provides alternative ways of investigating these constructions. As an illustration of this idea, we prove in [DW] that, for every bounded domain in C n : (i) if J 1 z = J 2 z for all z ∈ then every u ∈ PS H − () is the pointwise limit
Transactions of the American Mathematical Society, 1988
Invariant classes of functions on complex homogeneous spaces, with properties similar to those of the class of plurisubharmonic functions, are studied. The main tool is a regularization method for these classes, and the main theorem characterizes dual classes of functions (where duality is defined in terms of the local maximum property). These results are crucial in proving a duality theorem for complex interpolation of normed spaces, which is given elsewhere.
math.ac.vn
Let Ω be an open set in Cn. An upper semicontinuous function u : Ω → R ∪ {−∞} is called plurisubharmonic if u restricted to l ∩ Ω is subharmonic for every complex line l. Here we allow the constant function −∞ to be plurisubhar-monic. Denote by ♢♢ℋ(Ω) the cone of plurisubharmonic functions ...
Journal of Mathematical Analysis and Applications, 2016
In this paper, we prove that a continuous F -plurisubharmonic functions defined in an F -open set in C n is F -maximal if and only if it is F -locally F -maximal.
Annali di Matematica Pura ed Applicata, 2003
In this paper we focus on the maximum modulus principle and weak unique continuation for CR functions on an abstract almost CR manifold M . It is known that some assumption must be made on M in order to have either of these: it suffices to consider the standard CR structure on the sphere S 3 in C 2 to see that the maximum modulus principle is not valid in the presence of strict pseudoconvexity. For weak unique continuation, Rosay [R] has shown by an example that there is a strictly pseudoconvex CR structure on R 3 , which is a perturbation of the aforementioned standard CR structure on S 3 , such that there exists a smooth CR function u, u ≡ 0, with u ≡ 0 on a nonempty open set. However positive results were obtained in [DCN] under the assumption of pseudoconcavity and in [HN] under the assumption of essential pseudoconcavity (and also finite kind for the maximum modulus principle).
Manuscripta Mathematica, 1982
Inventiones Mathematicae, 2000
Bulletin of the American Mathematical Society, 1967
2014
We show that every strictly pseudoconvex domain Ω with smooth boundary in a complex manifold M admits a global defining function, i.e., a smooth plurisubharmonic function ϕ : U → R defined on an open neighbourhood U ⊂ M of Ω such that Ω = {ϕ < 0}, dϕ = 0 on bΩ and ϕ is strictly plurisubharmonic near bΩ. We then introduce the notion of the core c(Ω) of an arbitrary domain Ω ⊂ M as the set of all points where every smooth and bounded from above plurisubharmonic function on Ω fails to be strictly plurisubharmonic. If Ω is not relatively compact in M, then in general c(Ω) is nonempty, even in the case when M is Stein. It is shown that every strictly pseudoconvex domain Ω ⊂ M with smooth boundary admits a global defining function that is strictly plurisubharmonic precisely in the complement of c(Ω). We then investigate properties of the core. Among other results we prove 1-pseudoconcavity of the core, we show that in general the core does not possess an analytic structure, and we investigate Liouville type properties of the core.
Annales de l'Institut Fourier, 2018
Cet article est mis à disposition selon les termes de la licence CREATIVE COMMONS ATTRIBUTION-PAS DE MODIFICATION 3.
The Journal of Geometric Analysis, 1998
Let M be a smoothly bounded compact pseudoconvex complex manifold of finite type in the sense of D'Angelo such that the complex structure of M extends smoothly up to bM. Let m be an arbitrary nonnegative integer. Let f be a function in H(M) ∩ H m (M), where H m (M) is the Sobolev space of order m. Then f can be approximated by holomorphic functions on M in the Sobolev space H m (M). Also, we get a holomorphic approximation theorem near a boundary point of finite type.
Mathematische Zeitschrift
In previous works, G. Tomassini and the authors studied and classified complex surfaces admitting a real-analytic plurisubharmonic exhaustion function; let X be such a surface and D ⊆ X a domain admitting a continuous plurisubharmonic exhaustion function: what can be said about the geometry of D? If the exhaustion of D is assumed to be smooth, the second author already answered this question; however, the continuous case is more difficult and requires different methods. In the present paper, we address such question by studying the local maximum sets contained in D and their interplay with the complex geometric structure of X; we conclude that, if D is not a modification of a Stein space, then it shares the same geometric features of X.
Mathematische Annalen, 2020
We prove that for a pseudoconvex domain of the form $${\mathfrak {A}} = \{(z, w) \in {\mathbb {C}}^2 : v > F(z, u)\}$$ A = { ( z , w ) ∈ C 2 : v > F ( z , u ) } , where $$w = u + iv$$ w = u + i v and F is a continuous function on $${\mathbb {C}}_z \times {\mathbb {R}}_u$$ C z × R u , the following conditions are equivalent: The domain $$\mathfrak {A}$$ A is Kobayashi hyperbolic. The domain $$\mathfrak {A}$$ A is Brody hyperbolic. The domain $$\mathfrak {A}$$ A possesses a Bergman metric. The domain $$\mathfrak {A}$$ A possesses a bounded smooth strictly plurisubharmonic function, i.e. the core $$\mathfrak {c}(\mathfrak {A})$$ c ( A ) of $$\mathfrak {A}$$ A is empty. The graph $$\Gamma (F)$$ Γ ( F ) of F can not be represented as a foliation by holomorphic curves of a very special form, namely, as a foliation by translations of the graph $$\Gamma ({\mathcal H})$$ Γ ( H ) of just one entire function $${\mathcal {H}} : {\mathbb {C}}_z \rightarrow {\mathbb {C}}_w$$ H : C z → C w .
Journal of Mathematical Analysis and Applications
The primary objective of this paper is to study core sets in the setting of m-subharmonic functions on the class of (non-compact) Kähler manifolds. Core sets are investigated in different aspects by considering various classes of plurisubharmonic functions. One of the crucial concepts in studying the structure of this kind of sets is the pseudoconcavity. In a more general way, we will have the structure of core defined with respect to the m-subharmonic functions, which we call m-core in our setting, in terms of m-pseudoconcave sets.
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