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We introduce a class of rotationally invariant manifolds, which we call \emph{admissible}, on which the wave flow satisfies smoothing and Strichartz estimates. We deduce the global existence of equivariant wave maps from admissible…

Analysis of PDEs · Mathematics 2015-05-08 Piero D'Ancona , Qidi Zhang

Harmonic morphisms are maps between Riemannian manifolds that pull back harmonic functions to harmonic functions. These maps are characterized as horizontally weakly conformal harmonic maps and they have many interesting links and…

Differential Geometry · Mathematics 2017-12-12 Elsa Ghandour , Ye-Lin Ou

We revisit the well-established regularity estimates on harmonic maps on surfaces to question their independence with respect to the dimension of the target manifold. We are mainly interested in harmonic maps into target ellipsoids, that we…

Analysis of PDEs · Mathematics 2025-08-15 Romain Petrides

For two general polytopal complexes the set of face-wise affine maps between them is shown to be a polytopal complex in an algorithmic way. The resulting algorithm for the affine hom-complex is analyzed in detail. There is also a natural…

Combinatorics · Mathematics 2016-03-31 M. Bakuradze , A. Gamkrelidze , J. Gubeladze

A Riemannian manifold is called geometrically formal if the wedge product of any two harmonic forms is again harmonic. We classify geometrically formal compact 4-manifolds with nonnegative sectional curvature. If the sectional curvature is…

Differential Geometry · Mathematics 2015-02-03 Christian Baer

An approach is proposed for recovering affine correspondences (ACs) from orientation- and scale-invariant, e.g. SIFT, features. The method calculates the affine parameters consistent with a pre-estimated epipolar geometry from the point…

Computer Vision and Pattern Recognition · Computer Science 2018-07-11 Daniel Barath

We prove a general comparison result for homotopic finite $p$-energy $C^{1}$ $p$-harmonic maps $u,v:M\to N$ between Riemannian manifolds, assuming that $M$ is $p$-parabolic and $N$ is complete and non-positively curved. In particular, we…

Differential Geometry · Mathematics 2010-11-17 Giona Veronelli

We study biharmonic maps between conformally compact manifolds, a large class of complete manifolds with bounded geometry, asymptotically negative curvature, and smooth compactification. These metrics provide a far-reaching generalization…

Differential Geometry · Mathematics 2026-01-14 Marco Usula

We find geometric conditions on a four-dimensional almost Hermitian manifold under which the almost complex structure is a harmonic map or a minimal isometric imbedding of the manifold into its twistor space.

Differential Geometry · Mathematics 2017-11-15 Johann Davidov , Absar Ul Haq , Oleg Mushkarov

We prove that manifolds admitting a Riemannian metric for which products of harmonic forms are harmonic satisfy strong topological restrictions, some of which are akin to properties of flat manifolds. Others are more subtle, and are related…

Differential Geometry · Mathematics 2007-05-23 D. Kotschick

This paper deals essentially with affine or projective transformations of Lie groups endowed with a flat left invariant affine or projective structure. These groups are called flat affine or flat projective Lie groups. Our main results…

Differential Geometry · Mathematics 2016-02-29 Alberto Medina , Omar Saldarriaga , Hernan Giraldo

This paper deals with affine connections on real manifolds. We give a new characterization of flat affine connections on real manifolds by means of certain affine representations of the Lie group of automorphisms preserving the connection.…

Differential Geometry · Mathematics 2018-08-31 Alberto Medina , Omar Saldarriaga , Andres Villabón

For systems described by finite matrices, an affine form is developed for the maps that describe evolution of density matrices for a quantum system that interacts with another. This is established directly from the Heisenberg picture. It…

Quantum Physics · Physics 2009-11-11 Thomas F. Jordan , Anil Shaji , E. C. G. Sudarshan

Given a flat metric one may generate a local Hamiltonian structure via the fundamental result of Dubrovin and Novikov. More generally, a flat pencil of metrics will generate a local bi-Hamiltonian structure, and with additional…

Differential Geometry · Mathematics 2020-12-16 Liana David , Ian A. B. Strachan

In this paper we prove that geodesic mappings of (pseudo-) Riemannian manifolds preserve the class of differentiability \hbox{$(C^r, r\geq1)$}. Also, if the Einstein space $V_n$ admits a non trivial geodesic mapping onto a \hbox{(pseudo-)}…

Differential Geometry · Mathematics 2013-07-01 I. Hinterleitner , J. Mikeš

In this paper, we give an estimate of sub-Laplacian of Riemannian distance functions in pseudo-Hermitian geometry which plays a similar role as Laplacian comparison theorem in Riemannian geometry, and deduce a prior horizontal gradient…

Differential Geometry · Mathematics 2019-04-23 Tian Chong , Yuxin Dong , Yibin Ren , Zhang Wei

We prove existence results for Dirac-harmonic maps using index theoretical tools. They are mainly interesting if the source manifold has dimension 1 or 2 modulo 8. Our solutions are uncoupled in the sense that the underlying map between the…

Differential Geometry · Mathematics 2015-10-28 Bernd Ammann , Nicolas Ginoux

Let $\M$ be a classical Riemannian globally symmetric space of rank one and non-compact type. We prove the existence and uniqueness of solutions to the Dirichlet problem for harmonic maps into $\M$ with prescribed singularities along a…

dg-ga · Mathematics 2010-06-24 Gilbert Weinstein

The mixed scalar curvature of a foliated Riemannian manifold, i.e., an averaged mixed sectional curvature, has been considered by several geometers. We explore the Yamabe type problem: to prescribe the constant mixed scalar curvature for a…

Differential Geometry · Mathematics 2015-12-31 Vladimir Rovenski , Leonid Zelenko

Harmonic maps from Riemann surfaces arise from a conformally invariant variational problem. Therefore, on one hand, they are intimately connected with moduli spaces of Riemann surfaces, and on the other hand, because the conformal group is…

Differential Geometry · Mathematics 2017-10-05 Jürgen Jost , Enno Keßler , Jürgen Tolksdorf , Ruijun Wu , Miaomiao Zhu