arXiv research

New metrics of nonnegative curvature found on 2-sphere bundles.

This paper classifies equivariant principal bundles over a 2-sphere using isotropy representations.

Researchers classify differential operators between 3-sphere and 2-sphere bundles.

Proves Arnol'd's conjecture about Legendrian curves.

Kähler structures on products of 2-spheres have identical Chern classes.

Let M be a smooth 4-manifold which admits a relatively minimal hyperelliptic genus h Lefschetz fibration over the 2-sphere. If all of the vanishing cycles for this fibration are nonseparating curves, then we show that M is a 2-fold cover of a 2-sphere bundle over the 2-sphere, branched over an embedded surface. If the …

We consider the geodesic flow of reversible Finsler metrics on the 2-sphere and the 2-torus, whose geodesic flow has vanishing topological entropy. Following a construction of A. Katok, we discuss examples of Finsler metrics on both surfaces, which have large ergodic components for the geodesic flow in the unit tangent…

The paper classifies Willmore 2-spheres in $S^n$.

By studying the Higgs bundle equations with the gauge group replaced by the group of symplectic diffeomorphisms of the 2-sphere we encounter the notion of a folded hyperkaehler 4-manifold and conjecture the existence of a family of such metrics parametrised by an infinite-dimensional analogue of Teichmueller space.

Study on topological rigidity of ALE vector bundles with specific conditions.

The study finds infinitely many periodic orbits just above a critical value on a 2-sphere.

Study confirms uniqueness of minimal sphere in Atiyah-Hitchin manifold.

We show that any 4-manifold, after surgery on a curve, admits an achiral Lefschetz fibration. In particular, we show that the connected sum of any simply connected 4-manifold with a 2-sphere bundle over the 2-sphere will admit an achiral Lefschetz fibration. We also show these surgered manifolds admit near-symplectic s…

Minimal vector fields on a 2-sphere with varying volumes are discovered.

We prove that the space of gauge equivalence classes of U(1)-invariant connections on some SU(2)-principle bundles over the 4-sphere S^4 is weakly homotopy equivalent to a component of the second loop space of the 2-sphere S^2.

A self-transverse immersion of the 2-sphere into 4-space with algebraic number of self intersection points equal to -n induces an immersion of the circle bundle over the 2-sphere of Euler class 2n into 4-space. Precomposing the circle bundle immersions with their universal covering maps, we get for n>0 immersions g_n o…

We construct new complete, compact, inhomogeneous Einstein metrics on S^{m+2} sphere bundles over 2n-dimensional Einstein-Kahler spaces K_{2n}, for all n \ge 1 and all m \ge 1. We also obtain complete, compact, inhomogeneous Einstein metrics on warped products of S^m with S^2 bundles over K_{2n}, for m>1. Additionally,…

We introduce a local coordinate description for the correspondence between the space of oriented affine lines in Euclidean ${\Bbb{R}}^3$ and the tangent bundle to the 2-sphere. These can be utilised to give canonical coordinates on surfaces in ${\Bbb{R}}^3$, as we illustrate with a number of explicit examples.

The possibility of the global Lagrangian reduction of a mechanical system with symmetry is shown to be connected with the characteristic class of a principal fiber bundle of the configuration space over the factor manifold. It is proved that the reduced system is globally Lagrangian if and only if the product of the mo…

A Bott tower is the total space of a tower of fibre bundles with base CP^1 and fibres CP^1. Every Bott tower of height n is a smooth projective toric variety whose moment polytope is combinatorially equivalent to an n-cube. A circle action is semifree if it is free on the complement to fixed points. We show that a (qua…

We show that any Jacobi field along a harmonic map from the 2-sphere to the complex projective plane is integrable (i.e., is tangent to a smooth variation through harmonic maps). This provides one of the few known answers to this problem of integrability, which was raised in different contexts of geometry and analysis.…

We prove that the only exact Lagrangian submanifolds in an ALE space are spheres. ALE spaces are the simply connected hyperkahler manifolds which at infinity look like C^2/G for any finite subgroup G of SL(2,C). They can be realized as the plumbing of copies of the cotangent bundle of a 2-sphere according to ADE Dynkin…

The Pachner graph of 2-spheres is studied, focusing on subgraphs of flag and stacked 2-spheres.

A surface $Σ$ endowed with a Poisson tensor $π$ is known to admit a canonical integration $\mathcal{G}(π)$, which is a 4-dimensional manifold with a (symplectic) groupoid structure. In this short note we show that when $π$ is not an area form on the 2-sphere, then $\mathcal{G}(π)$ is diffeomorphic to the cotangent bund…

New non-orientable 4-manifolds created via knotting operations.

Proves properties of 4-manifolds with scalar curvature constraints.

Study conic 2-spheres, pinching curvature to find limits.

We calculate the Wess-Zumino term $Γ(g)$ for a harmonic map $g$ of a closed surface to a compact, simply connected, simple Lie group $G$ in terms of the energy and the holonomy of the Chern-Simons line bundle on the moduli space of flat $G$-connections. In the case of the 2-sphere we deduce that $Γ(g)$ is 0 or $π$ and …

Unique simple spines of homotopy 2-spheres are shown to be ambiently isotopic.

A conformal immersion of a 2-torus into the 4-sphere is characterized by an auxiliary Riemann surface, its spectral curve. This complex curve encodes the monodromies of a certain Dirac type operator on a quaternionic line bundle associated to the immersion. The paper provides a detailed description of the geometry and …

The 3-sphere has either 2 minimal 2-spheres or an optimal foliation by 2-spheres.

Concrete example of 2-sphere with constant curvature 1 and closed geodesics.

Generalizes surgery theorem for positive Ricci curvature metrics.

The paper studies minimal 2-spheres of constant curvature in complex hyperquadrics using matrix theory.

Isotopic surfaces in 4-manifolds are shown to be equivalent after stabilization.

Complete obstruction found for 2-spheres in 5-manifolds to be isotopic.

We study metric spaces homeomorphic to the 2-sphere, and find conditions under which they are quasisymmetrically homeomorphic to the standard 2-sphere. As an application of our main theorem we show that an Ahlfors 2-regular, linearly locally contractible metric 2-sphere is quasisymmetrically homeomorphic to the standar…

In this paper we obtain the following results: (1) Any compact Stein surface with boundary embeds naturally into a symplectic Lefschetz fibration over the 2-sphere. (2) There exists a minimal elliptic fibration over the 2-disk, which is not Stein. (3) The circle bundle over a genus n>1 surface with euler number e=-1 ad…

Motivated by the rich theory of harmonic maps from a 2-sphere, we study biharmonic maps from a 2-sphere in this paper. We first derive biharmonic equation for rotationally symmetric maps between rotationally symmetric 2-manifolds. We then apply the equation to obtain a classification of biharmonic maps in a family of r…

Classifies 5D stationary black hole domains using plumbing and disc bundles.

The degree of certain holomorphic 2-spheres is bounded.

Study hyperbolic 2-spheres with cone points, describing spaces for n=3.

New orbits found in Lagrangian systems on surfaces.

The paper examines the rigidity of marginally outer trapped 2-spheres in spacetime.

To every real analytic Riemannian manifold M there is associated a complex structure on a neighborhood of the zero section in the real tangent bundle of M. This structure can be uniquely specified in several ways, and is referred to as a Grauert tube. We say that a Grauert tube is entire if the complex structure can be…

Taut foliations map leaves to branched 2-sphere covers.

The study proves the existence of geodesics on reversible Finsler spheres.

Complete invariant defined for doodles on a sphere.