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1.
Rafael López 《manuscripta mathematica》2003,110(1):45-54
Let Ω be a smooth domain on the unit sphere 𝕊n whose closure is contained in an open hemisphere and denote by ℋ the mean curvature of ∂Ω as a submanifold of Ω with respect
to the inward unit normal. It is proved that for each real number H that satisfies inf ℋ > − H ≥ 0, there exists a unique radial graph on Ω bounded by ∂Ω with constant mean curvature H. The orientation on the graph is based on the normal that points on the opposite side as the radius vector.
Received: 5 June 2001 / Revised version: 9 April 2002
Research partially supported by a DGICYT Grant No. BFM2001-2967.
Mathematics Subject Classification (2000): 53A10, 53C42, 49Q05, 49Q10 相似文献
2.
By an ℱK-convex function on a length metric space, we mean one that satisfies f
n
≥ −Kf on all unitspeed geodesics. We show that natural ℱK-convex (-concave) functions occur in abundance on metric spaces of curvature bounded above (below) by K in the sense of Alexandrov. We prove Lipschitz extension and approximation theorems for ℱK-convex functions on CAT(K) spaces.
Received: 10 May 2002
Mathematics Subject Classification (2000): 53C70, 52A41 相似文献
3.
Paweł Strzelecki Heiko von der Mosel 《Calculus of Variations and Partial Differential Equations》2006,25(4):431-467
Motivated by previous work on elastic rods with self-contact, involving the concept of the global radius of curvature for
curves (as defined by Gonzalez and Maddocks), we define the global radius of curvature Δ[X] for a wide class of continuous parametric surfaces X for which the tangent plane exists on a dense set of parameters. It turns out that in this class of surfaces a positive lower
bound Δ[X] ≥ θ > 0 provides, naively speaking, the surface with a thickness of magnitude θ; it serves as an excluded volume constraint
for X, prevents self-intersections, and implies that the image of X is an embedded C1-manifold with a Lipschitz continuous normal. We also obtain a convergence and a compactness result for such thick surfaces,
and show one possible application to variational problems for embedded objects: the existence of ideal surfaces of fixed genus
in each isotopy class.
The proofs are based on a mixture of elementary topological, geometric and analytic arguments, combined with a notion of the
reach of a set, introduced by Federer in 1959.
Mathematics Subject Classification (2000) 49Q10, 53A05, 53C45, 57R52, 74K15 相似文献
4.
Stephen M. Robinson 《Mathematical Programming》2003,97(1-2):245-265
This is an expository paper about the analysis of variational conditions over sets defined in finite-dimensional spaces by
fairly smooth functions satisfying a constraint qualification. The primary focus is on results that can provide quantitative
and computable sensitivity information for particular instances of the problems under study, and our objective is to give
a personal view of the state of current knowledge in this area and of gaps in that knowledge that require future work. The
writing style is informal, in keeping with the objective of focusing the reader's attention on the basic concepts and the
relationships between them, rather than on details of the particular results themselves.
Received: December 1, 2002 / Accepted: April 25, 2003
Published online: May 28, 2003
Key words. variational condition – variational inequality – complementarity – sensitivity – stability – nondegeneracy
Mathematics Subject Classification (2000): Primary: 90C31. Secondary: 47J20, 49J40, 49J53, 90C33 相似文献
5.
6.
We show that a static Lorentzian manifold satisfying a completeness assumption is geodesically connected. In particular,
such condition is satisfied by all compact static manifolds; in the compact case, we also prove the existence of a closed
geodesic in every free homotopy class determined by a finite number of deck transformations.
Received: 28 July 2002 /
Published online: 16 May 2003
Mathematics Subject Classification (1991): 53C22, 53C50, 58E10
The first and the second author are sponsored by the MIUR national project ``Metodi variazionali e topologici nello studio
di fenomeni nonlineari'. The third author is partially sponsored by CNPq, Brazil. 相似文献
7.
Manuel A. Gómez 《Numerical Algorithms》1999,22(3-4):305-316
In this paper, an O(n
2) active set method is presented for minimizing the parametric quadratic function (1/2)x′Dx-a′x + λmax(c - γ x,0) subject to l ⩽ x ⩽ b, for all nonnegative values of the parameter γ. Here, D is a positive diagonal n x n matrix, a and γ are arbitrary N-vectors, c is an arbitrary scalar, l and b are arbitrary n-vectors, such thatl ⩽ b. An extension of this algorithm is presented for minimizing the parametric function (1/2)x′Dx-a
′
x + λ |γ′x - c| subject to l ⩽ x ⩽ b. It is also shown that these problems arise naturally in a tax programming problem.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
8.
We consider super-Brownian motion whose historical paths reflect from each other, unlike those of the usual historical super-Brownian
motion. We prove tightness for the family of distributions corresponding to a sequence of discrete approximations but we leave
the problem of uniqueness of the limit open. We prove a few results about path behavior for processes under any limit distribution.
In particular, we show that for any γ > 0, a “typical” increment of a reflecting historical path over a small time interval
Δt is not greater than (Δt)3/4−γ.
Received: 16 March 2000 / Revised version: 26 February 2001 / Published online: 9 October 2001 相似文献
9.
In this paper we consider the problem
where B is a ball in R
n
. For a small d>0, we show the uniqueness (up to rotation) of the one-bubbling solution which concentrates at a point of the boundary.
Received: 12 December 2001 / Published online: 10 February 2003
RID="⋆"
ID="⋆" Supported by M.U.R.S.T., project: ``Variational methods and nonlinear differential equations'
RID="⋆⋆"
ID="⋆⋆" Partial supported by National Center for Theoretical Sciences of NSC, Taiwan
Mathematics Subject Classification (2000): 35J60 相似文献
10.
Michael Bildhauer 《manuscripta mathematica》2003,110(3):325-342
Suppose that f: ℝ
nN
→ℝ is a strictly convex energy density of linear growth, f(Z)=g(|Z|2) if N>1. If f satisfies an ellipticity condition of the form
then, following [Bi3], there exists a unique (up to a constant) solution of the variational problem
provided that the given boundary data u
0
W
1
1
(ω;ℝ
N
) are additionally assumed to be of class L
∞(ω;ℝ
N
). Moreover, if μ<3, then the boundedness of u
0 yields local C
1,α-regularity (and uniqueness up to a constant) of generalized minimizers of the problem
In our paper we show that the restriction u
0L
∞(ω;ℝ
N
) is superfluous in the two dimensional case n=2, hence we may prescribe boundary values from the energy class W
1
1
(ω;ℝ
N
) and still obtain the above results.
Received: 12 February 2002 / Revised version: 7 October 2002 Published online: 14 February 2003
Mathematics Subject Classification (2000): 49N60, 49N15, 49M29, 35J 相似文献
11.
We study the minimal and maximal closed extension of a differential operator A on a manifold B with conical singularities, when A acts as an unbounded operator on weighted L
p
-spaces over B, 1<p<∞. Under suitable ellipticity assumptions we can define a family of complex powers A
z
, zℂ. We also obtain sufficient information on the resolvent of A to show the boundedness of the purely imaginary powers. Examples concern unique solvability and maximal regularity for the
solution of the Cauchy problem for the Laplacian on conical manifolds as well as certain quasilinear diffusion equations.
Received: 12 June 2001; in final form: 3 June 2002 /
Published online: 1 April 2003
Mathematics Subject Classification (2000): 35J70, 47A10, 35K57 相似文献
12.
Theodoros Vlachos 《manuscripta mathematica》2003,110(1):77-91
We show that minimal surfaces in space forms are determined, up to ambient isometries, by the induced metric and certain
invariants which are defined in terms of the higher fundamental forms and the complex structure.
Received: 6 May 2002 / Revised version: 5 July 2002
Current address: Institut für Mathematik, Universit?t Augsburg, Universit?tsstrasse 12, D-86135 Augsburg, Germany. e-mail: Theodoros.Vlachos@Math.Uni-Augsburg.De
The author was supported by the Alexander von Humboldt Foundation
Mathematics Subject Classification (2000): 53A10, 53C42
Acknowledgements. This work was written during the author's stay at the University of Augsburg as a research fellow of the Alexander von Humboldt
Foundation. I wish to express my gratitude to the Alexander von Humboldt Foundation for its generous support. Moreover, I
wish to thank Professor J.H. Eschenburg for many fruitful and stimulating conversations. 相似文献
13.
We introduce a new upper bound for the maximum-entropy sampling problem. Our bound is described as the solution of a linear
integer program. The bound depends on a partition of the underlying set of random variables. For the case in which each block
of the partition has bounded cardinality, we describe an efficient dynamic-programming algorithm to calculate the bound. For
the very special case in which the blocks have no more than two elements, we describe an efficient algorithm for calculating
the bound based on maximum-weight matching. This latter formulation has particular value for local-search procedures that
seek to find a good partition. We relate our bound to recent bounds of Hoffman, Lee and Williams. Finally, we report on the
results of some computational experiments.
Received: September 27, 2000 / Accepted: July 26, 2001 Published online: September 5, 2002
Key words. experimental design – design of experiments – entropy – maximum-entropy sampling – matching – integer program – spectral
bound – Fischer's inequality – branch-and-bound – dynamic programming
Mathematics Subject Classification (2000): 52B12, 90C10
Send offprint requests to: Jon Lee
Correspondence to: Jon Lee 相似文献
14.
S. R. Athreya M. T. Barlow R. F. Bass E. A. Perkins 《Probability Theory and Related Fields》2002,123(4):484-520
We consider diffusions corresponding to the generator
for continuous with γ
i
nonnegative. We show uniqueness for the corresponding martingale problem under certain non-degeneracy conditions on b
i
, γ
i
and present a counter-example when these conditions are not satisfied. As a special case, we establish uniqueness in law
for some classes of super-Markov chains with state dependent branching rates and spatial motions.
Received: 31 March 2001 / Revised version: 6 November 2001 / Published online: 1 July 2002 相似文献
15.
Jorge Lauret 《Annals of Global Analysis and Geometry》2006,30(2):107-138
Let (N, γ) be a nilpotent Lie group endowed with an invariant geometric structure (cf. symplectic, complex, hypercomplex or any of their ‘almost’ versions). We define a left invariant Riemannian metric on N compatible with γ to be minimal, if it minimizes the norm of the invariant part of the Ricci tensor among all compatible metrics with the same scalar curvature. We prove that minimal metrics (if any) are unique up to isometry and scaling, they develop soliton solutions for the ‘invariant Ricci’ flow and are characterized as the critical points of a natural variational problem. The uniqueness allows us to distinguish two geometric structures with Riemannian data, giving rise to a great deal of invariants.Our approach proposes to vary Lie brackets rather than inner products; our tool is the moment map for the action of a reductive Lie group on the algebraic variety of all Lie algebras, which we show to coincide in this setting with the Ricci operator. This gives us the possibility to use strong results from geometric invariant theory.Communicated by: Nigel Hitchin (Oxford)
Mathematics Subject Classifications (2000): Primary: 53D05, 53D55; Secondary: 22E25, 53D20, 14L24, 53C30. 相似文献
16.
We study the modal logic M L
r
of the countable random frame, which is contained in and `approximates' the modal logic of almost sure frame validity, i.e.
the logic of those modal principles which are valid with asymptotic probability 1 in a randomly chosen finite frame. We give
a sound and complete axiomatization of M L
r
and show that it is not finitely axiomatizable. Then we describe the finite frames of that logic and show that it has the
finite frame property and its satisfiability problem is in EXPTIME. All these results easily extend to temporal and other
multi-modal logics. Finally, we show that there are modal formulas which are almost surely valid in the finite, yet fail in
the countable random frame, and hence do not follow from the extension axioms. Therefore the analog of Fagin's transfer theorem
for almost sure validity in first-order logic fails for modal logic.
Received: 1 May 2000 / Revised version: 29 July 2001 / Published online: 2 September 2002
Mathematics Subject Classification (2000): 03B45, 03B70, 03C99
Key words or phrases: Modal logic – Random frames – Almost sure frame validity – Countable random frame – Axiomatization – Completeness 相似文献
17.
Romain Dujardin 《Mathematische Annalen》2003,325(4):745-765
In this paper we study laminar currents in ℙ2. Given a sequence of irreducible algebraic curves (C
n
) converging in the sense of currents to T, we find geometric conditions on the curves ensuring that the limit current T is laminar. This criterion is then applied to meromorphic dynamical systems in ℙ2, and laminarity of the dynamical ``Green' current is obtained for a wide class of meromorphic self maps of ℙ2, as well as for all bimeromorphic maps of projective surfaces.
Received: 24 September 2001 / Published online: 10 February 2003
Mathematics Subject Classification (2000): 32U40, 37Fxx, 32H50 相似文献
18.
We perform a smoothed analysis of a termination phase for linear programming algorithms. By combining this analysis with
the smoothed analysis of Renegar's condition number by Dunagan, Spielman and Teng (http://arxiv.org/abs/cs.DS/0302011) we
show that the smoothed complexity of interior-point algorithms for linear programming is O(m
3
log(m/Σ)). In contrast, the best known bound on the worst-case complexity of linear programming is O(m
3 L), where L could be as large as m. We include an introduction to smoothed analysis and a tutorial on proof techniques that have been useful in smoothed analyses.
Received: December 10, 2002 / Accepted: April 28, 2003
Published online: June 5, 2003
Key words. smoothed analysis – linear programming – interior-point algorithms – condition numbers
Mathematics Subject Classification (1991): 90C05, 90C51, 68Q25 相似文献
19.
Seyed Mahmoud Sheikholeslami 《Central European Journal of Mathematics》2010,8(3):468-473
A set S of vertices of a graph G = (V, E) without isolated vertex is a total dominating set if every vertex of V(G) is adjacent to some vertex in S. The total domination number γ
t
(G) is the minimum cardinality of a total dominating set of G. The total domination subdivision number sdγt
(G) is the minimum number of edges that must be subdivided (each edge in G can be subdivided at most once) in order to increase the total domination number. Karami, Khoeilar, Sheikholeslami and Khodkar,
(Graphs and Combinatorics, 2009, 25, 727–733) proved that for any connected graph G of order n ≥ 3, sdγ
t
(G) ≤ 2γ
t
(G) − 1 and posed the following problem: Characterize the graphs that achieve the aforementioned upper bound. In this paper
we first prove that sdγ
t
(G) ≤ 2α′(G) for every connected graph G of order n ≥ 3 and δ(G) ≥ 2 where α′(G) is the maximum number of edges in a matching in G and then we characterize all connected graphs G with sdγ
t
(G)=2γ
t
(G)−1. 相似文献
20.
Stefan Hildebrandt Heiko von der Mosel 《Calculus of Variations and Partial Differential Equations》2005,23(4):415-424
We present a new variational proof of the well-known fact that every Riemannian metric on a two-dimensional, simply connected domain with boundary can be represented by globally conformal parameters. From this the corresponding result for a metric on S2 is derived.Received: 1 September 2004, Accepted: 13 September 2004, Published online: 10 December 2004Mathematics Subject Classification:
49Q05, 53A10, 53C42 相似文献