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We show that there exist smooth, simply connected, four-dimensional spin manifolds which do not admit Einstein metrics, but nonetheless satisfy the strict Hitchin-Thorpe inequality. Our construction makes use of the Bauer/Furuta cohomotopy…

微分几何 · 数学 2007-05-23 Masashi Ishida , Claude LeBrun

We prove a Theorem on homotheties between two given tangent sphere bundles $S_rM$ of a Riemannian manifold $M,g$ of $\dim\geq 3$, assuming different variable radius functions $r$ and weighted Sasaki metrics induced by the conformal class of…

微分几何 · 数学 2019-07-25 Rui Albuquerque

We study null Sasakian structures in dimension five. First, based on a result due to Koll\'ar [Ko], we improve a result by Boyer, Galicki and Matzeu in [BGM] and prove that simply connected manifolds diffeomorphic to $# k(S^2\times S^3)$…

微分几何 · 数学 2024-03-04 Jaime Cuadros

We survey on the geometry of the tangent bundle of a Riemannian manifold, endowed with the classical metric established by S. Sasaki 60 years ago. Following the results of Sasaki, we try to write and deduce them by different means.…

微分几何 · 数学 2019-09-05 Rui Albuquerque

We study homogeneous instantons on the seven dimensional Stiefel manifold V in the context of $G_2$ and Sasakian geometry. According to the reductive decomposition of V we provide an explicit description of all invariant $G_2$ and Sasakian…

微分几何 · 数学 2026-01-13 Andrés J. Moreno , Luis E. Portilla

We study super Yang-Mills theories on five-dimensional Sasaki-Einstein manifolds. Using localisation techniques, we find that the contribution from the vector multiplet to the perturbative partition function can be calculated by counting…

高能物理 - 理论 · 物理学 2015-06-18 Johannes Schmude

The AdS/CFT correspondence between Sasaki-Einstein spaces and quiver gauge theories is studied from the perspective of massless BPS geodesics. The recently constructed toric Lpqr geometries are considered: we determine the dual…

高能物理 - 理论 · 物理学 2009-11-11 Sergio Benvenuti , Martin Kruczenski

We present a general numerical method for investigating prescribed Ricci curvature problems on toric K\"ahler manifolds. This method is applied to two generalisations of Einstein metrics, namely Ricci solitons and quasi-Einstein metrics. We…

微分几何 · 数学 2015-11-13 Stuart James Hall , Thomas Murphy

A Sasaki-like almost contact complex Riemannian manifold is defined as an almost contact complex Riemannian manifold which complex cone is a holomorphic complex Riemannian manifold. Explicit compact and non-compact examples are given. A…

微分几何 · 数学 2016-06-15 Stefan Ivanov , Hristo Manev , Mancho Manev

Two Kaehler metrics on one complex manifold are said to be c-projectively equivalent if their J-planar curves, i.e., curves defined by the property that their acceleration is complex proportional to their velocity, coincide. The degree of…

微分几何 · 数学 2015-10-02 Vladimir S. Matveev , Stefan Rosemann

We construct quasi-Einstein metrics on some hypersurface families. The hypersurfaces are circle bundles over the product of Fano, K\"ahler-Einstein manifolds. The quasi-Einstein metrics are related to various gradient K\"ahler-Ricci…

微分几何 · 数学 2015-06-04 Stuart James Hall

We show that $\scriptstyle{#9(S^2\times S^3)}$ admits an 8-dimensional complex family of inequivalent non-regular Sasakian-Einstein structures. These are the first known Einstein metrics on this 5-manifold. In particular, the bound…

微分几何 · 数学 2007-05-23 Charles P. Boyer , Krzysztof Galicki , Michael Nakamaye

We construct symplectic and K\"ahler ray reduced spaces and discuss their relation with the Marsden-Weinstein (point) reduction. This K\"ahler reduction is well defined even when the momentum value is not totally isotropic. The…

微分几何 · 数学 2008-03-18 Oana Mihaela Drăgulete

It is well known that any 4-dimensional hyperkahler metric with two commuting Killing fields may be obtained explicitly, via the Gibbons-Hawking Ansatz, from a harmonic function invariant under a Killing field on R^3. In this paper, we find…

微分几何 · 数学 2007-05-23 David M. J. Calderbank , Henrik Pedersen

In supergravity compactifications, there is in general no clear prescription on how to select a finite-dimensional family of metrics on the internal space, and a family of forms on which to expand the various potentials, such that the…

高能物理 - 理论 · 物理学 2018-05-09 Stefanos Katmadas , Alessandro Tomasiello

In this paper, we show that the existence of Sasakian-Einstein metrics is closely related to the properness of corresponding energy functionals. Under the condition that admitting no nontrivial Hamiltonian holomorphic vector field, we prove…

微分几何 · 数学 2011-07-21 Xi Zhang

We establish an equivalence between conformally Einstein--Maxwell Kahler 4-manifolds (recently studied in many works) and extremal Kahler 4-manifolds (in the sense of Calabi) with nowhere vanishing scalar curvature. The corresponding pairs…

微分几何 · 数学 2019-01-07 Vestislav Apostolov , David M. J. Calderbank

We show that transverse coupled K\"ahler-Einstein metrics on toric Sasaki manifolds arise as a critical point of a volume functional. As a preparation for the proof, we re-visit the transverse moment polytopes and contact moment polytopes…

微分几何 · 数学 2022-11-04 Akito Futaki

In this paper, a survey of the recent results about the classification of the connected holonomy groups of the Lorentzian manifolds is given. A simplification of the construction of the Lorentzian metrics with all possible connected…

微分几何 · 数学 2016-11-08 Anton S. Galaev

A systematic construction of St\"{a}ckel systems in separated coordinates and its relation to bi-Hamiltonian formalism are considered. A general form of related hydrodynamic systems, integrable by the Hamilton-Jacobi method, is derived. One…

可精确求解与可积系统 · 物理学 2015-06-26 Maciej Blaszak , Wen-Xiu Ma