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We derive some necessary conditions on a Riemannian metric $(M, g)$ in four dimensions for it to be locally conformal to K\"ahler. If the conformal curvature is non anti--self--dual, the self--dual Weyl spinor must be of algebraic type $D$…

Differential Geometry · Mathematics 2015-05-13 Maciej Dunajski , Paul Tod

We study the existence of invariant metrics with holonomy $G_{2(2)}^* \subset SO(4,3)$ on compact nilmanifolds, i.e. on compact quotients of nilpotent Lie groups by discrete subgroups. We prove that, up to isomorphism, there exists only one…

Differential Geometry · Mathematics 2014-03-27 Anna Fino , Ignacio Luján

Let $(G,g)$ be a 4-dimensional Riemannian Lie group with a 2-dimensional left-invariant, conformal foliation $\F$ with minimal leaves. Let $J$ be an almost Hermitian structure on $G$ adapted to the foliation $\F$. We classify such…

Differential Geometry · Mathematics 2022-01-12 Emma Andersdotter Svensson , Sigmundur Gudmundsson

For any 4D split-signature conformal structure, there is an induced twistor distribution on the 5D space of all self-dual totally null 2-planes, which is $(2,3,5)$ when the conformal structure is not anti-self-dual. Several examples where…

Differential Geometry · Mathematics 2024-11-05 Pawel Nurowski , Katja Sagerschnig , Dennis The

Statistical manifolds, the parameter spaces of smooth families of probability density functions, are the central objects of study in information geometry. While the elementary differential geometry of Riemannian statistical manifolds is…

Differential Geometry · Mathematics 2025-05-09 James A. Reid

In a space-time, a conformal structure is defined by the distribution of light-cones. Geodesics are traced by freely falling particles, and the collection of all unparameterized geodesics determines the projective structure of the…

Differential Geometry · Mathematics 2015-10-02 Vladimir S. Matveev , Andrzej Trautman

We consider a 2-d conformal theory based on (G x G')/ H coset sigma model introduced by Guadagnini, Martellini and Mintchev. It is shown that in the case of {SU(2) x SU(2)}/ U(1) the metric of the corresponding background is of T^{p,q}…

High Energy Physics - Theory · Physics 2009-09-17 L. A. Pando Zayas , A. A. Tseytlin

The cycle-preserving symmetries for the nine two-dimensional real spaces of constant curvature are collectively obtained within a Cayley-Klein framework. This approach affords a unified and global study of the conformal structure of the…

Mathematical Physics · Physics 2019-07-19 Francisco J. Herranz , Mariano Santander

The hierarchy of conformally invariant k-th powers of the Laplacian acting on a scalar field with scaling dimensions $\Delta_{(k)}=k-d/2$, k=1,2,3 as obtained in the recent work [1] is rederived using the Fefferman-Graham d+2 dimensional…

High Energy Physics - Theory · Physics 2008-11-26 Ruben Manvelyan , Karapet Mkrtchyan , Ruben Mkrtchyan

Fino and Kath determined all possible holonomy groups of seven-dimensional pseu\-do-Rie\-man\-nian manifolds contained in the exceptional, non-compact, simple Lie group $\mathrm{G}_2^*$ via the corresponding Lie algebras. They are…

Differential Geometry · Mathematics 2019-06-18 Christian Volkhausen

We demonstrate that all perturbative scale invariant heterotic sigma models with a compact target space $M^D$ are conformally invariant. The proof, presented in detail for up to and including two loops, utilises a geometric analogue of the…

High Energy Physics - Theory · Physics 2025-08-07 Georgios Papadopoulos

Conformal geodesics are distinguished curves on a conformal manifold, loosely analogous to geodesics of Riemannian geometry. One definition of them is as solutions to a third order differential equation determined by the conformal…

Differential Geometry · Mathematics 2021-02-09 Joel Fine , Yannick Herfray

We study complex non-K\"ahler manifolds with Hermitian metrics being locally conformal to metrics with special cohomological properties. In particular, we provide examples where the existence of locally conformal holomorphic-tamed…

Differential Geometry · Mathematics 2016-08-04 Daniele Angella , Luis Ugarte

We study the chiral de Rham complex (CDR) over a manifold $M$ with holonomy $\rm G_2$. We prove that the vertex algebra of global sections of the CDR associated to $M$ contains two commuting copies of the Shatashvili-Vafa $\rm G_2$…

Quantum Algebra · Mathematics 2016-07-01 Lázaro O. Rodríguez Díaz

Biconformal gauging of the conformal group has a scale-invariant volume form, permitting a single form of the action to be invariant in any dimension. We display several 2n-dim scale-invariant polynomial actions and a dual action. We solve…

High Energy Physics - Theory · Physics 2009-10-31 A. Wehner , J. T. Wheeler

In this paper we relate the Fefferman-Graham ambient metric construction for conformal manifolds to the approach to conformal geometry via the canonical Cartan connection. We show that from any ambient metric that satisfies a weakening of…

Differential Geometry · Mathematics 2007-05-23 Andreas Cap , A. Rod Gover

We define new Riemannian structures on 7-manifolds by a differential form of mixed degree which is the critical point of a (possibly constrained) variational problem over a fixed cohomology class. The unconstrained critical points…

Differential Geometry · Mathematics 2009-11-10 Frederik Witt

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…

Differential Geometry · Mathematics 2020-12-17 Elsa Ghandour , Sigmundur Gudmundsson , Victor Ottosson

We construct a large family of conformally covariant tridifferential operators as tangential operators in the Fefferman--Graham ambient space. Our construction is analogous to the linear and bilinear constructions of…

Differential Geometry · Mathematics 2025-11-14 Jeffrey S. Case , Opal Cieslak

A locally conformally K\"ahler (lcK) manifold is a complex manifold $(M,J)$ together with a Hermitian metric $g$ which is conformal to a K\"ahler metric in the neighbourhood of each point. In this paper we obtain three classification…

Differential Geometry · Mathematics 2021-06-15 Farid Madani , Andrei Moroianu , Mihaela Pilca