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1.
Summary If (M, ω) is a compact symplectic manifold andL ⊂M a compact Lagrangian submanifold and if φ is a Hamiltonian diffeomorphism ofM then the V. Arnold conjecture states (possibly under additional conditions) that the number of intersection section points
ofL and φ (L) can be estimated by #{Lϒφ (L)}≥ cuplength +1. We shall prove this conjecture for the special case (L, M)=(ℝP
n
, ℂP
n
) with the standard symplectic structure. 相似文献
2.
L. Di Terlizzi 《Acta Mathematica Hungarica》2009,124(4):399-401
We considered in Example 3.1 of the paper [1] an S-structure on R2n+s
. We concluded that when s > 1 this manifold cannot be of constant φ-sectional curvature. Unfortunately this result is wrong. In fact, essentially due
to a sign mistake in defining the φ-structure and a consequent transposition of the elements of the φ-basis (3.2), some of
the Christoffel’s symbols were incorrect. In the present rectification, using a more slendler tecnique, we prove that our
manifold is of constant φ-sectional curvature −3s and then it is η-Einstein. 相似文献
3.
V. Maiorov 《Advances in Computational Mathematics》2006,25(4):435-450
We consider the manifolds H
n(φ) formed by all possible linear combinations of n functions from the set {φ(A⋅+b)}, where x→Ax+b is arbitrary affine mapping in the space ℝd. For example, neural networks and radial basis functions are the manifolds of type H
n(φ). We obtain estimates for pseudo-dimension of the manifold H
n(φ) for wide collection of the generator function φ. The estimates have the order O(d
2
n) in degree scale, that is the order is proportional to number of parameters of the manifold H
n(φ). Moreover the estimates for ɛ-entropy of the manifold H
n(φ) are obtained.
Mathematics subject classifications (2000) 41A46, 41A50, 42A61, 42C10
V. Maiorov: Supported by the Center for Absorption in Science, Ministry of Immigrant Absorption, State of Israel. 相似文献
4.
Mikhail Tyaglov 《Journal d'Analyse Mathématique》2011,114(1):1-62
For a given real entire function φ in the class U
2n
*, n ≥ 0, with finitely many nonreal zeroes, we establish a connection between the number of real zeroes of the functions Q[φ] = (φ′/φ)′ and Q
1[φ] = (φ″/φ′)′. This connection leads to a proof of the Hawaii Conjecture (T. Craven, G. Csordas, and W. Smith [5]), which states that if φ is a real polynomial, then the number of real zeroes of Q[φ] does not exceed the number of nonreal zeroes of φ. 相似文献
5.
6.
On any compact Riemannian manifold (M,g) of dimension n, the L
2-normalized eigenfunctions φ
λ
satisfy
||fl||¥ £ Cl\fracn-12\|\phi_{\lambda}\|_{\infty}\leq C\lambda^{\frac{n-1}{2}} where −Δφ
λ
=λ
2
φ
λ
. The bound is sharp in the class of all (M,g) since it is obtained by zonal spherical harmonics on the standard n-sphere S
n
. But of course, it is not sharp for many Riemannian manifolds, e.g., flat tori ℝ
n
/Γ. We say that S
n
, but not ℝ
n
/Γ, is a Riemannian manifold with maximal eigenfunction growth. The problem which motivates this paper is to determine the
(M,g) with maximal eigenfunction growth. In an earlier work, two of us showed that such an (M,g) must have a point x where the set ℒ
x
of geodesic loops at x has positive measure in S*xMS^{*}_{x}M. We strengthen this result here by showing that such a manifold must have a point where the set ℛ
x
of recurrent directions for the geodesic flow through x satisfies |{ℛ}
x
|>0. We also show that if there are no such points, L
2-normalized quasimodes have sup-norms that are o(λ
(n−1)/2), and, in the other extreme, we show that if there is a point blow-down x at which the first return map for the flow is the identity, then there is a sequence of quasimodes with L
∞-norms that are Ω(λ
(n−1)/2). 相似文献
7.
This paper studies the question of when a loop φ={φ
t
}0≤
t
≤1 in the group Symp(M,ω) of symplectomorphisms of a symplectic manifold (M,ω) is isotopic to a loop that is generated by a time-dependent Hamiltonian function. (Loops with this property are said to
be Hamiltonian.) Our main result is that Hamiltonian loops are rigid in the following sense: if φ is Hamiltonian with respect
to ω, and if φ′ is a small perturbation of φ that preserves another symplectic form ω′, then φ′ is Hamiltonian with respect
to ω′. This allows us to get some new information on the structure of the flux group, i.e. the image of π1(Symp(M,ω)) under the flux homomorphism. We give a complete proof of our result for some manifolds, and sketch the proof in general.
The argument uses methods developed by Seidel for studying properties of Hamiltonian loops via the quantum homology of M.
Oblatum 31-X-1997 & 20-III-1998 / Published online: 14 October 1998 相似文献
8.
A. V. Isaev 《Journal of Geometric Analysis》2008,18(3):795-799
We prove a characterization theorem for the unit polydisc Δ
n
⊂ℂ
n
in the spirit of a recent result due to Kodama and Shimizu. We show that if M is a connected n-dimensional complex manifold such that (i) the group Aut (M) of holomorphic automorphisms of M acts on M with compact isotropy subgroups, and (ii) Aut (M) and Aut (Δ
n
) are isomorphic as topological groups equipped with the compact-open topology, then M is holomorphically equivalent to Δ
n
.
相似文献
9.
We will simplify earlier proofs of Perelman’s collapsing theorem for 3-manifolds given by Shioya–Yamaguchi (J. Differ. Geom.
56:1–66, 2000; Math. Ann. 333: 131–155, 2005) and Morgan–Tian ( [math.DG], 2008). A version of Perelman’s collapsing theorem states: “Let
{M3i}\{M^{3}_{i}\}
be a sequence of compact Riemannian 3-manifolds with curvature bounded from below by (−1) and
$\mathrm{diam}(M^{3}_{i})\ge c_{0}>0$\mathrm{diam}(M^{3}_{i})\ge c_{0}>0
. Suppose that all unit metric balls in
M3iM^{3}_{i}
have very small volume, at most
v
i
→0 as
i→∞, and suppose that either
M3iM^{3}_{i}
is closed or has possibly convex incompressible toral boundary. Then
M3iM^{3}_{i}
must be a graph manifold for sufficiently large
i”. This result can be viewed as an extension of the implicit function theorem. Among other things, we apply Perelman’s critical
point theory (i.e., multiple conic singularity theory and his fibration theory) to Alexandrov spaces to construct the desired
local Seifert fibration structure on collapsed 3-manifolds. 相似文献
10.
Chen Falai 《分析论及其应用》1995,11(2):1-8
This paper proved the following three facts about the Lipschitz continuous property of Bernstein polynomials and Bezier nets
defined on a triangle: suppose f(P) is a real valued function defined on a triangle T, (1) If f(P) satisfies Lipschitz continuous
condition, i.e. f(P)∃LipAα, then the corresponding Bernstein Bezier net fn∃Lip
Asec
αφα, here φ is the half of the largest angle of triangle T; (2) If Bernstein Bezier net fn∃Lip
Bα, then its elevation Bezier net Efn∃Lip
Bα; and (3) If f(P)∃Lip
Aα, then the corresponding Bernstein polynomials Bn(f;P)∃Lip
Asec
αφα, and the constant Asecαφ is best in some sense.
Supported by NSF and SF of National Educational Committee 相似文献
11.
Yong Fang 《Archiv der Mathematik》2011,97(3):281-288
Let (M, F) be a closed C
∞ Finsler manifold. The lift of the Finsler metric F to the universal covering space defines an asymmetric distance [(d)\tilde]{\widetilde d} on [(M)\tilde]{\widetilde M}. It is well-known that the classical comparison theorem of Aleksandrov does not exist in the Finsler setting. Therefore,
it is necessary to introduce new Finsler tools for the study of the asymmetric metric space ([(M)\tilde], [(d)\tilde]){(\widetilde M, \widetilde d)}. In this paper, by using the geometric flip map and the unstable-stable angle introduced in [2], we prove that if (M, F) is a closed Finsler manifold of negative flag curvature, then ([(M)\tilde], [(d)\tilde]){(\widetilde M, \widetilde d)} is an asymmetric δ-hyperbolic space in the sense of Gromov. 相似文献
12.
Guy David 《Journal of Geometric Analysis》2010,20(4):837-954
We give a new proof and a partial generalization of Jean Taylor’s result (Ann. Math. (2) 103(3), 489–539, 1976) that says that Almgren almost-minimal sets of dimension 2 in ℝ3 are locally C
1+α
-equivalent to minimal cones. The proof is rather elementary, but uses a local separation result proved in Ann. Fac. Sci.
Toulouse 18(1), 65–246, 2009 and an extension of Reifenberg’s parameterization theorem (David et al. in Geom. Funct. Anal. 18, 1168–1235, 2008). The key idea is still that if X is the cone over an arc of small Lipschitz graph in the unit sphere, but X is not contained in a disk, we can use the graph of a harmonic function to deform X and substantially diminish its area. The local separation result is used to reduce to unions of cones over arcs of Lipschitz
graphs. A good part of the proof extends to minimal sets of dimension 2 in ℝ
n
, but in this setting our final regularity result on E may depend on the list of minimal cones obtained as blow-up limits of E at a point. 相似文献
13.
We study projective curvature tensor in K-contact and Sasakian manifolds. We prove that (1) if a K-contact manifold is quasi projectively flat then it is Einstein and (2) a K-contact manifold is ξ-projectively flat if and only if it is Einstein Sasakian. Necessary and sufficient conditions for a K-contact manifold to be quasi projectively flat and φ-projectively flat are obtained. We also prove that for a (2n + 1)-dimensional Sasakian manifold the conditions of being quasi projectively flat, φ-projectively flat and locally isometric to the unit sphere S
2n+1 (1) are equivalent. Finally, we prove that a compact φ-projectively flat K-contact manifold with regular contact vector field is a principal S
1-bundle over an almost Kaehler space of constant holomorphic sectional curvature 4. 相似文献
14.
Under a general hypothesis an expanding map T of a Riemannian manifold M is known to preserve a measure equivalent to the Liouville measure on that manifold. As a consequence of this and Birkhoff’s
pointwise ergodic theorem, the orbits of almost all points on the manifold are asymptotically distributed with regard to this
Liouville measure. Let T be Lipschitz of class τ for some τ in (0,1], let Ω(x) denote the forward orbit closure of x and for a positive real number δ and let E(x0, δ) denote the set of points x in M such that the distance from x0 to Ω is at least δ. Let dim A denote the Hausdorff dimension of the set A. In this paper we prove a result which implies that there is a constant C(T) > 0 such that
dimE(x0,d) 3 dimM - \fracC(T)|logd| \dim E(x_0,\delta) \ge \dim M - \frac{C(T)}{\vert\!\log \delta \vert}
if τ = 1 and
dimE(x0,d) 3 dimM - \fracC(T)log|logd|\dim E(x_0,\delta) \ge \dim M - \frac{C(T)}{\log \vert \log \delta \vert}
if τ < 1. This gives a quantitative converse to the above asymptotic distribution phenomenon. The result we prove is of sufficient
generality that a similar result for expanding hyperbolic rational maps of degree not less than two follows as a special case. 相似文献
15.
We consider a generalized semi-infinite optimization problem (GSIP) of the form (GSIP) min{f(x)‖xεM}, where M={x∈ℝn|hi(x)=0i=l,...m, G(x,y)⩾0, y∈Y(x)} and all appearing functions are continuously differentiable. Furthermore, we assume that
the setY(x) is compact for allx under consideration and the set-valued mappingY(.) is upper semi-continuous. The difference with a standard semi-infinite problem lies in thex-dependence of the index setY. We prove a first order necessary optimality condition of Fritz John type without assuming a constraint qualification or
any kind of reduction approach. Moreover, we discuss some geometrical properties of the feasible setM.
This work was partially supported by the “Deutsche Forschungsgemeinschaft” through the Graduiertenkolleg “Mathematische Optimierung”
at the University of Trier. 相似文献
16.
R. Gabasov N. M. Dmitruk F. M. Kirillova 《Proceedings of the Steklov Institute of Mathematics》2010,271(1):103-124
Let f be an orientation-preserving Morse-Smale diffeomorphism of an n-dimensional (n ≥ 3) closed orientable manifold M
n
. We show the possibility of representing the dynamics of f in a “source-sink” form. The roles of the “source” and “sink” are played by invariant closed sets one of which, A
f
, is an attractor, and the other, R
f
, is a repeller. Such a representation reveals new topological invariants that describe the embedding (possibly, wild) of
stable and unstable manifolds of saddle periodic points in the ambient manifold. These invariants have allowed us to obtain
a classification of substantial classes of Morse-Smale diffeomorphisms on 3-manifolds. In this paper, for any n ≥ 3, we describe the topological structure of the sets A
f
and R
f
and of the space of orbits that belong to the set M
n
\ (A
f
∪ R
f
). 相似文献
17.
Nancy Guelman 《Bulletin of the Brazilian Mathematical Society》2002,33(1):75-97
We prove that if 𝒻1 is the time one map of a transitive and codimension one Anosov flow φ and it is C
1-approximated by Axiom A diffeomorphisms satisfying a property called P, then the flow is topologically conjugated to the suspension of a codimension one Anosov diffeomorphism. A diffeomorphism
𝒻 satisfies property P if for every periodic point in M the number of periodic points in a fundamental domain of its central manifold is constant.
Received: 15 March 2001 相似文献
18.
We show that if a closed manifold M admits an ℱ-structure (not necessarily polarized, possibly of rank zero) then its minimal entropy vanishes. In particular,
this is the case if M admits a non-trivial S
1-action. As a corollary we obtain that the simplicial volume of a manifold admitting an ℱ-structure is zero.?We also show
that if M admits an ℱ-structure then it collapses with curvature bounded from below. This in turn implies that M collapses with bounded scalar curvature or, equivalently, its Yamabe invariant is non-negative.?We show that ℱ-structures
of rank zero appear rather frequently: every compact complex elliptic surface admits one as well as any simply connected closed
5-manifold.?We use these results to study the minimal entropy problem. We show the following two theorems: suppose that M is a closed manifold obtained by taking connected sums of copies of S
4, ℂP
2,
2,S
2×S
2and the K3 surface. Then M has zero minimal entropy. Moreover, M admits a smooth Riemannian metric with zero topological entropy if and only if M is diffeomorphic to S
4,ℂP
2,S
2×S
2,ℂP
2#
2 or ℂP
2# ℂP
2. Finally, suppose that M is a closed simply connected 5-manifold. Then M has zero minimal entropy. Moreover, M admits a smooth Riemannian metric with zero topological entropy if and only if M is diffeomorphic to S
5,S
3×S
2, then on trivial S
3-bundle over S
2 or the Wu-manifold SU(3)/SO(3).
Oblatum 13-III-2002 & 12-VIII-2002?Published online: 8 November 2002
G.P. Paternain was partially supported by CIMAT, Guanajuato, México.?J. Petean is supported by grant 37558-E of CONACYT. 相似文献
19.
Ahmed Laghribi 《Israel Journal of Mathematics》2012,187(1):1-22
Let F be a field of characteristic not 2. In this article, we treat the quadratic forms of Im(W(F) → W(F(φ))) which are indecomposable, i.e., those which are not isometric to a sum of two nonzero forms of this image, where W(F) is the Witt ring of F-quadratic forms, and F(φ) is the function field of the affine quadric given by φ. This is related to the descent problems studied in [12, 14]. More precisely, we will focus on indecomposable quadratic forms of minimal dimension, which we detail for φ of dimension less than or equal to 8. We also include other related results. 相似文献
20.
We consider a (2m + 3)-dimensional Riemannian manifold M(ξ r, ηr, g ) endowed with a vertical skew symmetric almost contact 3-structure. Such manifold is foliated by 3-dimensional submanifolds
of constant curvature tangent to the vertical distribution and the square of the length of the vertical structure vector
field is an isoparametric function. If, in addition, M(ξ r, ηr, g ) is endowed with an f -structure φ, M, turns out to be a framed f−CR-manifold. The fundamental 2-form Ω associated with φ is a presymplectic form. Locally, M is the Riemannian product
of two totally geodesic submanifolds, where
is a 2m-dimensional Kaehlerian submanifold and
is a 3-dimensional submanifold of constant curvature. If M is not compact, a class of local Hamiltonians of Ω is obtained. 相似文献