We consider the conformal class of the Riemannian product $g_0 + g$, where $g_0$ is the constant curvature metric on $S^m$ and $g$ is a metric of constant scalar curvature on some closed manifold. We show that the number of metrics of constant scalar curvature in the conformal class grows at least linearly with respect to the square root of the scalar curvature of $g$. This is obtained by studying radial solutions of the equation $Δu -λu + λu^p =0$ on $S^m$, and the number of solutions in terms of $λ$.
The goal of this paper is to study conformal Yamabe soliton and $*$-Yamabe soliton, whose potential vector field is torse forming. Here, we have characterized conformal Yamabe soliton admitting potential vector field as torse forming with respect to Riemannian connection, semi-symmetric metric connection and projective semi-symmetric connection on Riemannian manifold. We have also shown the nature of $*$-Yamabe soliton with torse forming vector field on Riemannian manifold admitting Riemannian connection. Lastly we have developed an example to corroborate some theorems regarding Riemannian con…
Reducible Riemannian manifolds with conformal product structures
Université Paris-Saclay（巴黎萨克雷大学）；CNRS（法国国家科学研究中心）；Institute of Mathematics “Simion Stoilow” of the Romanian Academy（罗马尼亚科学院西米翁·斯托伊洛瓦数学研究所）；Fakultät für Mathematik Universität Regensburg（雷根斯堡大学数学学院）
Conformal gradient vector fields on Riemannian manifolds with boundary
设$(M^n,g)$是具有光滑边界的$n$维紧连通黎曼流形.我们证明了$M$上存在一个非平凡的共形梯度向量场，并对Ricci曲率进行适当的控制，使得$M$等距于$\mathbb{S}^{n}$的半球。证明了如果一个Einstein流形上存在非零共形梯度向量场，则它的标量曲率为正，且等距于$\mathbb{S}^{n}$的半球。进一步证明了如果$ M $存在一个非平凡共形向量场且具有常数量曲率，则其数量曲率为正。最后，对共形向量场能量的适当控制意味着$M$与半球$\mathbb{S}^n_+$等距。
Let $(M^n,g)$ be an $n$-dimensional compact connected Riemannian manifold with boundary. In this article, we study the effects of the presence of a nontrivial conformal vector field on $(M^n,g)$. We used the wekk-known de-Rham Laplace operator and a nontrivial solution of the famous Fischer-Marsden differential equation to provide two characterizations of the hemisphere $\mathbb{S}^{n}_{+}(c)$ of constant curvature $c>0.$ As a consequence of the characterization using the Fischer-Marsden equation, we prove the cosmic no-hair conjecture under a given integral condition.
Locally conformal flat Riemannian manifolds with constant principal Ricci curvatures and locally conformal flat C-spaces
证明了任何局部共形平坦黎曼流形，只要其Jacobi算子沿每条测地线具有常特征值，则该流形具有常主Ricci曲率。本文给出了4，5，6，7，8维具有常Ricci特征值的局部共形平坦黎曼流形的局部分类（直到等距）.证明了任意具有常主Ricci曲率的n维$(4\leq n \leq 8)$局部共形平坦黎曼流形是黎曼局部对称空间.
The present paper deals with the characterization of a new submersion named semi-invariant conformal $ζ^{\perp }$-Riemannian submersion from almost contact metric manifolds onto Riemannian manifolds which is the generalization of some known submersions on Riemannian manifolds. We give important and adequate conditions for such submersions to be totally geodesic and harmonic. Also, few examples are examined for such submersions endowed with horizontal Reeb vector field.
A 4-dimensional Riemannian manifold M, equipped with an additional tensor structure S, whose fourth power is minus identity, is considered. The structure S has a skew-circulant matrix with respect to some basis of the tangent space at a point on M. Moreover, S acts as an isometry with respect to the metric g. A fundamental tensor is defined on such a manifold (M,g,S) by g and by the covariant derivative of S. This tensor satisfies a characteristic identity which is invariant to the usual conformal transformation. Some curvature properties of (M,g,S) are obtained. A Lie group as a manifold of t…
We study left-invariant foliations ${\mathcal F}$ on semi-Riemannian Lie groups $G$ generated by a subgroup $K$. We are interested in such foliations which are conformal and with minimal leaves of codimension two. We classify such foliations ${\mathcal F}$ when the subgroup $K$ is one of the important $\text{SU}(2)$, $\text{SL}_{2}(\mathbb R)$, $\text{SU}(2)\times\text{SU}(2)$, $\text{SU}(2)\times\text{SL}_{2}(\mathbb R)$, $\text{SU}(2)\times\text{SO}(2)$, $\text{SL}_{2}(\mathbb R)\times\text{SU}(2)$. This way we construct new multi-dimensional families of Lie groups $G$ carrying such foliatio…
In this paper, we bend a closed Riemannian manifold in the conformal class, through solving a fully nonlinear equation. As a result, we prove that each metric of quasi-negative Ricci curvature is conformal to a metric with negative Ricci curvature.
Conformally flat Einstein-like 4-manifolds and conformally flat Riemannian 4-manifolds all of whose Jacobi operators have parallel eigenspaces along every geodesic
We introduce a new notion of a homogeneous pair for a pseudo-Riemannian metric $g$ and a positive function $f$ on a manifold $M$ admitting a free $\mathbb{R}_{>0}$-action. There are many examples admitting this structure. For example, (a) a class of pseudo-Hessian manifolds admitting a free $\mathbb{R}_{>0}$-action and a homogeneous potential function such as the moduli space of torsion-free $G_2$-structures, (b) the space of Riemannian metrics on a compact manifold, and (c) many moduli spaces of geometric structures such as torsion-free ${\rm Spin}(7)$-structures admit this structure. Hence w…
