Levi-Civita connections of flag manifolds

Levi-Civita联络的零化可投影性

Null-projectability of Levi-Civita connections

本文研究Levi-Civita联络沿零化平行分布叶状结构的可投影性，将Afifi关于中性符号中等维数分布的经典结果推广到任意维数，并引入Riemann扩张的适当推广。

Connections compatible with tensors. A characterization of left-invariant Levi--Civita connections in Lie groups

Symmetric connections that are compatible with semi-Riemannian metrics can be characterized using an existence result for an integral leaf of a (possibly non integrable) distribution. In this paper we give necessary and sufficient conditions for a left-invariant connection on a Lie group to be the Levi-Civita connection of some semi-Riemannian metric on the group. As a special case, we will consider constant connections in $\R^n$.

When is a Connection a Levi-Civita Connection?

We consider the more general question as to when a connection is a metric connection. There are two aspects to this investigation: first, the determination of the integrability conditions that ensure the existence of a local parallel metric in the neighbourhood of a given point and second, the characterization of the topological obstruction to a globally defined parallel metric.

Diffeological Levi-Civita connections

A diffeological connection on a diffeological vector pseudo-bundle is defined just the usual one on a smooth vector bundle; this is possible to do, because there is a standard diffeological counterpart of the cotangent bundle. On the other hand, there is not yet a standard theory of tangent bundles, although there are many suggested and promising versions, such as that of the internal tangent bundle, so the abstract notion of a connection on a diffeological vector pseudo-bundle does not automatically provide a counterpart notion for Levi-Civita connections. In this paper we consider the dual o…

Levi-Civita's Theorem for Noncommutative Tori

We show how to define Riemannian metrics and connections on a noncommutative torus in such a way that an analogue of Levi-Civita's theorem on the existence and uniqueness of a Riemannian connection holds. The major novelty is that we need to use two different notions of noncommutative vector field. Levi-Civita's theorem makes it possible to define Riemannian curvature using the usual formulas.

具有常Levi-Civita或Bismut全纯截面曲率的局部共形Kähler流形

Locally conformally Kähler manifolds with constant Levi-Civita or Bismut holomorphic sectional curvature

本文针对具有常Levi-Civita或Bismut全纯截面曲率的局部共形Kähler流形，运用已有技术解答了相关类似问题，推进了非Kähler几何中相关猜想的研究。

仿射-正交流形与到Levi-Civita联络的形变

Affine-Orthogonal Manifolds and Deformation to Levi-Civita Connections

研究配备平坦仿射联络和对角化Riemannian度量的仿射-正交流形，证明其向Levi-Civita联络的形变迫使Euler示性数消失，为Chern猜想提供证据。

Odd Symmetric Tensors, and an Analogue of the Levi-Civita Connection for an Odd Symplectic Supermanifold

We consider odd Poisson (odd symplectic) structure on supermanifolds induced by an odd symmetric rank $2$ (non-degenerate) contravariant tensor field. We describe the difference between odd Riemannian and odd symplectic structure in terms of the Cartan prolongation of the corresponding Lie algebras, and formulate an analogue of the Levi-Civita theorem for an odd symplectic supermanifold.

Metrized Quantum Vector Bundles over Quantum Tori Built from Riemannian Metrics and Rosenberg's Levi-Civita Connections

We build metrized quantum vector bundles, over a generically transcendental quantum torus, from Riemannian metrics, using Rosenberg's Levi-Civita connections for these metrics. We also prove that two metrized quantum vector bundles, corresponding to positive scalar multiples of a Riemannian metric, have distance zero between them with respect to the modular Gromov-Hausdorff propinquity.

Non-Riemannian Gravitation amd its relation with Levi-Civita theories

The mathematical relations between certain classical Non-Riemannian gravity models and Einstein-Proca theories are discussed in details. We also show some relations with theories with scalar fields.

Levi-Civita Ricci-flat metrics on non-Kähler Calabi-Yau manifolds

In this paper, we provide new examples of Levi-Civita Ricci-flat Hermitian metrics on certain compact non-Kähler Calabi-Yau manifolds, including every compact Hermitian Weyl-Einstein manifold, every compact locally conformal hyperKähler manifold, certain suspensions of Brieskorn manifolds, and every generalized Hopf manifold provided by suspensions of exotic spheres. These examples generalize previous constructions on Hopf manifolds. Additionally, we also construct new examples of compact Hermitian manifolds with nonnegative first Chern class that admit constant strictly negative Riemannian sc…

Quasi-Kaehler manifolds with a pair of Norden metrics

The basic class of the non-integrable almost complex manifolds with a pair of Norden metrics are considered. The interconnections between corresponding quantities at the transformation between the two Levi-Civita connections are given. A 4-parametric family of 4-dimensional quasi-Kaehler manifolds with Norden metric is characterized with respect to the associated Levi-Civita connection.

非交换微分形式上Levi-Civita联络的存在性与唯一性

Existence and uniqueness of the Levi-Civita connection on noncommutative differential forms

该研究结合希尔伯特模与代数方法，给出非交换微分形式上埃尔米特无挠联络的存在充要条件与唯一充分条件，证明紧黎曼流形θ-形变存在唯一该类联络并显式构造，还得到经典Levi-Civita联络的新构造。

Finite element approximation of the Levi-Civita connection and its curvature in two dimensions

We construct finite element approximations of the Levi-Civita connection and its curvature on triangulations of oriented two-dimensional manifolds. Our construction relies on the Regge finite elements, which are piecewise polynomial symmetric (0,2)-tensor fields possessing single-valued tangential-tangential components along element interfaces. When used to discretize the Riemannian metric tensor, these piecewise polynomial tensor fields do not possess enough regularity to define connections and curvature in the classical sense, but we show how to make sense of these quantities in a distributi…

Geometric structures in $Sol_3$

In this paper, we conclude the geometric structures in $Sol_3$ with the Levi-Civita connection and the semi-symmetric non-metric connection. We discuss two special cases to study the geometric structures in $Sol_3$ with the semi-symmetric non-metric connection, namely $\widehat{P}=a(X_3)\partial_3$ and $\widehat{P}=b(X_3)\partial_1$, also get relatively complete conclusions respectively. As a special case, we investigate the geometric structures in $Sol_3$ with the Levi-Civita connection.

Invariant and anti-invariant submanifolds of special quasi-sasakian manifolds

The present paper deals with the study of Chaki-pseudo parallel and Deszcz-pseudo parallel invariant submanifolds of SQ-Sasakian manifolds with respect to Levi-Civita connection and semisymmetric metric connection and obtain that these two classes are equivalent with a certain condition. Also the invariant and anti-invariant submanifolds of SQ-Sasakian manifolds with respect to Levi-Civita connection as well as semisymmetric metric connection whose metrics are Ricci solitons are studied.

典范广义 Levi-Civita 联络及其曲率

The canonical generalised Levi-Civita connection and its curvature

本文在精确 Courant 代数胚上由广义度量与散度算子构造典范广义 Levi-Civita 联络，消除联络选择歧义，并用经典几何数据分解其曲率，给出广义 Ricci 张量与标量不变量工具箱。

Courant代数胚上的平坦广义联络

Flat Generalized Connections on Courant Algebroids

本文研究传递Courant代数胚上含典范Levi-Civita联络的度量广义联络的平坦性条件，指出其构造单元为紧单李群，刻画了对应李群上的左不变平坦Levi-Civita广义联络并证明非平坦联络存在。

Self-similar solutions to the Hesse flow

We define a Hesse soliton, that is, a self-similar solution to the Hesse flow on Hessian manifolds. On information geometry, the $e$-connection and the $m$-connection are important, which do not coincide with the Levi-Civita one. Therefore, it is interesting to consider a Hessian manifold with a flat connection which does not coincide with the Levi-Civita one. We call it a proper Hessian manifold. In this paper, we show that any compact proper Hesse soliton is expanding and any non-trivial compact gradient Hesse soliton is proper. Furthermore, we show that the dual space of a Hesse-Einstein ma…

Determination of the metric from the connection

As is well known, a metric on a manifold determines a unique symmetric connection for which the metric is parallel: the Levi-Civita connection. In this paper we investigate the inverse problem: to what extent is the metric of a Riemannian manifold determined by its Levi-Civita connection? It is shown that for a generic Levi-Civita connection of a metric $h$ there exists a set of positive semi-definite tensor fields $h_{a}$ such that the parallel metrics are the positive-definite linear combinations of the $h_{a}$. Moreover, the set of all parallel metrics may be constructed by a soley algebrai…

$α$-associated Metric On Rigged Null hypersurfaces

Let $x:M\to\Bm$ be the canonical injection of a Null Hypersurface $(M,g)$ in a semi-Riemannian manifold $(\overline{M},\bar g)$. A rigging for $M$ is a vector field $L$ defined on some open set of $\overline{M}$ containing $M$ such that $L_p\notin T_pM$ for each $p\in M$. Such a vector field induces a null rigging $N$. Let $\bar η$ be the 1-form which is $\bar g$-metrically equivalent to $N$ and $η=x^\star\barη$ its pull back on $M$. We introduce and study for a given non vanishing function $α$ on $M$ the so-called $α$-associated (semi-)Riemannian metric $ g_α=g+αη\otimes η$. For a closed rigg…

Some Rigidity Conditions on Berwald Structures

This thesis contains an introduction to the method of average in Finsler geometry. The method is applied to Berwald spaces, obtaining geodesic rigidity conditions. We prove that the Levi-Civita connection of any Riemannian metric affine equivalent to the Berwald metric leaves invariant the indicatrix of th Finsler metric F. A converse result also holds: if (M,F) is a Finsler structure such that there is a Riemannian connection whose Levi-Civita leaves invariant by parallel transport the indicatrix of the Finsler structure, then the structure (M,F) is Berwald. As an application we obtain a nece…

The canonical involution in the space of connections of a $(J^{2}=\pm 1)$-metric manifold

A $(J^{2}=\pm 1)$-metric manifold has an almost complex or almost product structure $J$ and a compatible metric $g$. We show that there exists a canonical involution in the set of connections on such a manifold, which allows to define a projection over the set of connections adapted to $J$. This projection sends the Levi Civita connection onto the first canonical connection. In the almost Hermitian case, it also sends the $\nabla^{-}$ connection onto the Chern connection, thus applying the line of metric connections defined by $\nabla ^{-}$ and the Levi Civita connections onto the line of cano…

A note on the Gauss-Bonnet-Chern theorem for general connection

In this paper, we prove a local index theorem for the DeRham Hodge-laplacian which is defined by the connection compatible with metric. This connection need not be the Levi-Civita connection. When the connection is Levi-Civita connection, this is the classical local Gauss-Bonnet-Chern theorem.

Notes on flat pseudo-Riemannian manifolds

In these notes we survey basic concepts of affine geometry and their interaction with Riemannian geometry. We give a characterization of affine manifolds which has as counterpart those pseudo-Riemannian manifolds whose Levi-Civita connection is flat. We show that no connected semisimple Lie group admits a left invariant flat affine connection. We characterize flat pseudo-Riemannian Lie groups. For a flat left-invariant pseudo-metric on a Lie group, we show the equivalence between the completeness of the Levi-Civita connection and unimodularity of the group. We emphasize the case of flat left i…

On the geometry of warped foliations

We discuss the geometry of warped foliations. After examining the Levi-Civita connection, we describe the formulae for sectional, Ricci and scalar curvatures. In the final part of this note, we present some examples.

A note on the CR cohomology of Levi-Flat minimal orbits in complex flag manifolds

We prove a relation between the $\bar\partial_M$ cohomology of a minimal orbit $M$ of a real form $G_0$ of a complex semisimple Lie group $G$ in a flag manifold $G/Q$ and the Dolbeault cohomology of the Matsuki dual open orbit $X$ of the complexification $K$ of a maximal compact subgroup $K_0$ of $G_0$, under the assumption that $M$ is Levi-flat.

On the geometry of the rescaled Riemannian metric on tensor bundles of arbitrary type

Let $(M,g)$ be an $n-$dimensional Riemannian manifold and $T_{1}^{1}(M)$ be its $(1,1)-$tensor bundle equipped with the rescaled Sasaki type metric $% ^{S}g_{f}$ which rescale the horizontal part by a nonzero differentiable function $f$. In the present paper, we discuss curvature properties of the Levi-Civita connection and another metric connection of $T_{1}^{1}(M)$. We construct almost paracomplex Norden structures on $T_{1}^{1}(M)$ and investigate conditions for these structures to be para-Kähler (paraholomorphic) and quasi-Kähler. Also, some properties of almost paracomplex Norden structur…

Conjugate connections and statistical structures on almost Norden manifolds

Relations between conjugate connections with respect to the pair of Norden metrics and to the almost complex structure on almost Norden manifolds are studied. Conjugate connections of the Levi-Civita connections induced by the Norden metrics are obtained. Statistical structures on almost Norden manifolds are considered.

统计流形上可除三次形式的测地连通性

Geodesic Connectedness on Statistical Manifolds with Divisible Cubic Forms

研究统计流形上具有可除三次形式的仿射连接的测地连通性，建立类似Hopf-Rinow定理的结论，并推导出统计流形的Cartan-Hadamard型定理。

Projective vs metric structures

We present a number of conditions which are necessary for an n-dimensional projective structure (M,[nabla]) to include the Levi-Civita connection nabla of some metric on M. We provide an algorithm, which effectively checks if a Levi-Civita connection is in the projective class and, in the positive, which finds this connection and the metric. The article also provides a basic information on invariants of projective structures, including the treatment via Cartan's normal projective connection. In particular we show that there is a number of Fefferman-like conformal structures, defined on a subbu…

Higher order Levi forms on homogeneous CR manifolds

We investigate the nondegeneracy of higher order Levi forms on weakly nondegenerate homogeneous $CR$ manifolds. Improving previous results, we prove that general orbits of real forms in complex flag manifolds have order less or equal $3$ and the compact ones less or equal~$2$. Finally we construct by Lee extensions weakly nondegenerate $CR$ vector bundles with arbitrary orders of nondegeneracy.

A canonical connection on sub-Riemannian contact manifolds

We construct a canonically defined affine connection in sub-Riemannian contact geometry. Our method mimics that of the Levi-Civita connection in Riemannian geometry. We compare it with the Tanaka-Webster connection in the three-dimensional case.

A counterexample to Belgun-Moroianu conjecture

We construct an example of a closed manifold with a nonflat reducible locally metric connection such that it preserves a conformal structure and such that it is not the Levi-Civita connection of a Riemannian metric.

Derivative Operators in Metric and Geometric Structures

This paper (the seventh paper in a series of eight) continues the development of our theory of multivector and extensor calculus on smooth manifolds. Here we deal first with the concepts of ordinary Hodge coderivatives, duality identities, and Hodge coderivative identities. Then, we recall the concept of a Levi-Civita geometric structure and the concepts of Levi-Civita and gauge derivatives. New formulas that are important in the Lagrangian theory of multivector adn extensor fields are obtained. We introduce also he concept of covariant Hodge coderivative. We detail how all these concepts are …

度量 Jordan 代数的曲率

Curvatures of metric Jordan algebras

本文沿 Milnor 思路研究度量 Jordan 代数，定义并证明唯一 Jordan-Levi-Civita 联络，导出三类曲率张量及公式，并据此刻画形式实与幂零 Jordan 代数的曲率和 Einstein 度量。

Relationship between stochastic flows and connection forms

In this article I will prove new representation for the Levi-Civita connection in terms of the stochastic flow corresponding to Brownian motion on manifold.

On Gauduchon connections with Kähler-like curvature

We study Hermitian metrics with a Gauduchon connection being "Kähler-like", namely, satisfying the same symmetries for curvature as the Levi-Civita and Chern connections. In particular, we investigate $6$-dimensional solvmanifolds with invariant complex structures with trivial canonical bundle and with invariant Hermitian metrics. The results for this case give evidence for two conjectures that are expected to hold in more generality: first, if the Strominger-Bismut connection is Kähler-like, then the metric is pluriclosed; second, if another Gauduchon connection, different from Chern or Strom…

On geometry of $2$-nondegenerate CR structures of hypersurface type and flag structures on leaf spaces of Levi foliations

We construct canonical absolute parallelisms over real-analytic manifolds equipped with $2$-nondegenerate, hypersurface-type CR structures of arbitrary odd dimension not less than $7$ whose Levi kernel has constant rank belonging to a broad subclass of CR structures that we label as recoverable. For this we develop a new approach based on a reduction to a special flag structure, called the dynamical Legendrian contact structure, on the leaf space of the CR structure's associated Levi foliation. This extends the results of Porter-Zelenko [20] from the case of regular CR symbols constituting a d…

$G_2$ 复旗流形上的 CR 轨道

CR Orbits on the complex flag manifolds of $G_2$

本文显式描述了分裂实形式 $G_{2(2)}$ 在 $G_2$ 复旗流形上的轨道及其诱导的不变 CR 结构，研究了 Levi 形式并证明所有简单齐次情形均出现，同时给出了这些齐次 CR 流形的方程。

Nonholonomic Ricci Flows: III. Curve Flows and Solitonic Hierarchies

The geometric constructions are elaborated on (semi) Riemannian manifolds and vector bundles provided with nonintegrable distributions defining nonlinear connection structures induced canonically by metric tensors. Such spaces are called nonholonomic manifolds and described by two equivalent linear connections also induced in unique forms by a metric tensor (the Levi Civita and the canonical distinguished connection, d-connection). The lifts of geometric objects on tangent bundles are performed for certain classes of d-connections and frame transforms when the Riemann tensor is parametrized by…