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Using a recent result of L\'arusson and Poletsky regarding plurisubharmonic subextensions we prove a disc formula for the quasiplurisubharmonic global extremal function for domains in complex projective space. As a corollary we get a…

Complex Variables · Mathematics 2013-05-22 Benedikt Steinar Magnusson

We give conditions characterizing holomorphic and meromorphic functions in the unit disk of the complex plane in terms of certain weak forms of the maximum principle. Our work is directly inspired by recent results of John Wermer, and by…

Complex Variables · Mathematics 2011-07-22 J. T. Anderson , J. A. Cima , N. Levenberg , T. J. Ransford

Walter Rudin, in 1966, characterized analytic functions in the unit disk in terms of the maximum principle relative to the boundary. We conjecture a generalization of this result when the disk is replaced by the punctured disk, and we prove…

Complex Variables · Mathematics 2007-05-23 John Wermer

We consider complex projective space P^{n} and a smooth closed curve gamma in P^{n}. Harvey and Lawson have defined the notion of the projective hull \hat{K} of a compact subset K in P^n. This concept is an analogue of the polynomial hull…

Complex Variables · Mathematics 2008-07-24 John Wermer

Let X be a complex manifold and c a simple closed curve in X. We address the question: What conditions on c ensure the existence of a 1-dimensional complex subvariety V with boundary c in X. When X = C^n, an answer to this question involves…

Complex Variables · Mathematics 2008-08-21 H. Blaine Lawson , John Wermer

A spectrahedron is a set defined by a linear matrix inequality. A projection of a spectrahedron is often called a semidefinitely representable set. We show that the convex hull of a finite union of such projections is again a projection of…

Optimization and Control · Mathematics 2009-08-25 Tim Netzer , Rainer Sinn

The projective hull X^ of a subset X in complex projective space P^n is an analogue of the classical polynomial hull of a set in C^n. If X is contained in an affine chart C^n on P^n, then the affine part of X^ is the set of points x in C^n…

Complex Variables · Mathematics 2017-12-12 F. Reese Harvey , H. Blaine Lawson, , John Wermer

We use our disc formula for the Siciak-Zahariuta extremal function to characterize the polynomial hull of a connected compact subset of complex affine space in terms of analytic discs.

Complex Variables · Mathematics 2007-05-23 Finnur Larusson , Ragnar Sigurdsson

We present a characterization, in terms of projective biduality, for the hypersurfaces appearing in the boundary of the convex hull of a compact real algebraic variety.

Algebraic Geometry · Mathematics 2010-07-02 Kristian Ranestad , Bernd Sturmfels

We introduce the notion of a ``projective hull'' for subsets of complex projective varieties, parallel to the idea of the polynomial hull in affine varieties. With this concept, a generalization of J. Wermer's classical theorem on the hull…

Complex Variables · Mathematics 2017-12-12 F. Reese Harvey , H. Blaine Lawson

We prove that if $K$ is a compact subset of an affine variety O = P^n - D (where D is a projective hypersuface), and if K is a compact subset of a closed analytic subvariety V \subset O, then the projective hull K^ of K has the property…

Complex Variables · Mathematics 2007-05-23 Blaine Lawson , John Wermer

We prove two disc formulas for the Siciak-Zahariuta extremal function of an arbitrary open subset of complex affine space. We use these formulas to characterize the polynomial hull of an arbitrary compact subset of complex affine space in…

Complex Variables · Mathematics 2008-08-26 Finnur Larusson , Ragnar Sigurdsson

We consider the class of (possibly) infinite metric spaces with integer-valued totally split-decomposable metric and possessing an injective hull which has the structure of a polyhedral complex. For this class, we give a characterization…

Metric Geometry · Mathematics 2015-05-29 Maël Pavón

The standard convex closed hull of a set is defined as the intersection of all images, under the action of a group of rigid motions, of a half-space containing the given set. In this paper we propose a generalisation of this classical…

Metric Geometry · Mathematics 2024-09-04 Zakhar Kabluchko , Alexander Marynych , Ilya Molchanov

We study the convex hull of a set $S\subset \mathbb{R}^n$ defined by three quadratic inequalities. A simple way of generating inequalities valid on $S$ is to take nonnegative linear combinations of the defining inequalities of $S$. We call…

Algebraic Geometry · Mathematics 2024-05-29 Grigoriy Blekherman , Alex Dunbar

This is a survey of the theory of complex projective (CP^1) structures on compact surfaces. After some preliminary discussion and definitions, we concentrate on three main topics: (1) Using the Schwarzian derivative to parameterize the…

Differential Geometry · Mathematics 2009-02-12 David Dumas

We describe convex hulls of the simplest compact space curves, reducible quartics consisting of two circles. When the circles do not meet in complex projective space, their algebraic boundary contains an irrational ruled surface of degree…

Algebraic Geometry · Mathematics 2017-01-24 Evan D. Nash , Ata Firat Pir , Frank Sottile , Li Ying

Extensions of the notions of polynomially and rationally convex hulls are introduced. Using these notions, a generalization of a result of Duval and Levenberg on polynomially convex hulls containing no analytic discs is presented. As a…

Complex Variables · Mathematics 2019-02-26 Alexander J. Izzo

Let T be the unit circle in the complex plane C. This paper proves the existence of analytic structure in a compact subset K of T X C^n, where K has so-called "lineally convex" or "hypoconvex" fibers over T. It also addresses a related…

Complex Variables · Mathematics 2007-05-23 Marshall A. Whittlesey

We construct a connected, compact set $K \subset \mathbb{C}^2$ with the following property: there exist points $p \in \hat{K} \setminus K$ such that there does not exist a sequence $\{A_\nu\}$ of analytic sets $A_\nu \subset\subset…

Complex Variables · Mathematics 2025-07-23 Tobias Harz
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