Every smooth 4-sphere is the same as the standard one.
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Turing complete flow on 4-sphere preserves volume.
Calegari's 4-spheres from fibered knots are proven standard.
Paper proves every stable 4-sphere has a unique diffeomorphism class.
Smoothly isotopic 3-discs in 4-sphere become identical after 5-dimensional push.
New homotopy 4-spheres and real projective 4-spaces created.
Generators of the 4-sphere's smooth mapping class group via diffeomorphisms of Montesinos twins.
Smoothly knotted 5RP^2 found in 4-sphere.
Kervaire's sphere-link is equivalent to a ribbon sphere-link, simplifying complex 2-complexes.
Gluck twisting certain knots results in standard 4-spheres.
We present an infinite sequence of smooth embeddings of a connected sum of 6 projective planes in the 4-sphere, which are all ambient homeomorphic, but pairwise ambient non-diffeomorphic. The double covers of the 4-sphere ramified along these surfaces form a family of the exotic $\Bbb CP^2#5\bar{\Bbb CP^2}$ constructed…
New research finds 145 infinite families of CS spheres are standard.
In relation to the 4-dimensional smooth Poincaré conjecture we construct a tentative invariant of homotopy 4-spheres using embedded contact homology (ECH) and Seiberg-Witten theory (SWF). But for good reason it is a constant value independent of the sphere, so this null-result demonstrates that one should not try to us…
Torsion elements on surfaces extend over 4-sphere in various ways.
New findings about twists in 4-sphere diffeomorphisms.
We show that a finite group which admits a faithful, smooth, orientation-preserving action on a homology 4-sphere, and in particular on the 4-sphere, is isomorphic to a subgroup of the orthogonal group SO(5), by explicitly determining the various groups which can occur (up to an indetermination of index two in the case…
For every N > 0 there exists a group of deficiency less than -N that arises as the fundamental group of a smooth homology 4-sphere and also as the fundamental group of the complement of a compact contractible submanifold of the 4-sphere. A group is the fundamental group of the complement of a contractible submanifold o…
Study -instantons on 7-sphere from 4-sphere instantons.
Theta graph diffeomorphism shows nontrivial mapping class of 4-sphere.
Approaches 4D Schoenflies via pseudo-isotopy.
The paper constructs homotopy 4-spheres using pochette surgery.
Study pochette surgery on 4-manifolds, focusing on 4-spheres.
The Price twist creates three 4-manifolds from a 4-sphere.
A surface in the 4-sphere is trivially embedded, if it bounds a 3-dimensional handle body in the 4-sphere. For a surface trivially embedded in the 4-sphere, a diffeomorphism over this surface is extensible if and only if this preserves the Rokhlin quadratic form of this embedded surface.
Heegaard diagrams for 5-manifolds help in understanding their structure.
Study on Ricci flow on 4-spheres, proving standard sphere convergence.
New theory proves infinite homology 3-spheres in homology 4-spheres.
Researchers found non-smoothable surfaces in a 4-sphere, solving K3 problems.
Gompf proposed a conjecture on Cappell-Shaneson matrices whose affirmative answer implies that all Cappell-Shaneson homotopy 4-spheres are diffeomorphic to the standard 4-sphere. We study Gompf conjecture on Cappell-Shaneson matrices using various algebraic number theoretic techniques. We find a hidden symmetry between…
New spanning 3-disks found for unlink in 4-sphere.
Examples are given to show that some compact contractible 4-manifolds can be knotted in the 4-sphere. It is then proved that any finitely presented perfect group with a balanced presentation is a knot group for an embedding of some contractible 4-manifold in the 4-sphere.
Standardizes Dunfield-Gong's 4-sphere, solves knot sliceness problem.
We prove that the infinite family of homotopy 4-spheres constructed by Daniel Nash are all diffeomorphic to 4-sphere.
3-balls in 4-sphere become isotopic in 5-ball.
Concerns decompositions of smooth 4-manifolds as the union of two handlebodies, each with handles of index <=2 (``Heegard'' decompositions).Sample result: Two 2-complexes are (up to 2-deformation) dual spines of a Heegard decomposition of the 4-sphere if and only if they satisfy the conclusions of the Alexander-Lefshet…
In this paper, Problem 4.17 on R. Kirby's problem list is solved by constructing infinitely many aspherical 4-manifolds that are homology 4-spheres
Researchers create infinite Brunnian links of 3-balls in 4-sphere.
Infinite Klein bottles with 4-fold meridians found.
The only finite nonabelian simple group acting on a homology 3-sphere - necessarily non-freely - is the dodecahedral group (in analogy, the only finite perfect group acting freely on a homology 3-sphere is the binary dodecahedral group ). In the present pa…
This is the first comprehensive introduction to the authors' recent attempts toward a better understanding of the global concepts behind spinor representations of surfaces in 3-space. The important new aspect is a quaternionic-valued function theory, whose "meromorphic functions" are conformal maps into quaternions, wh…
We discuss the constant problem for conic 4-spheres. Based on earlier works of Chang-Han-Yang and Han-Li-Teixeira, we are able to find a necessary condition for the existence problem. In particular, when the condition is sharp, we have the uniqueness result similar to that of Troyanov in dimension 2. It indicat…
We characterize Willmore tori in the 4-sphere with nontrivial normal bundle as Twistor projections of elliptic curves in complex projective space or as inverted minimal tori (with planar ends) in Euclidean 4-space.
Explains a 1978 construction for Yang-Mills instantons.
For a non-orientable closed surface standardly embedded in the 4-sphere, a diffeomorphism over this surface is extendable if and only if this diffeomorphism preserves the Guillou-Marin quadratic form of this embedded surface.
New non-orientable 4-manifolds created via knotting operations.
New 3D handlebodies in 4-sphere and 5-ball are not isotopic even with same boundary.
We prove that a constrained Willmore immersion of a 2-torus into the conformal 4-sphere is either of "finite type", that is, has a spectral curve of finite genus, or is of "holomorphic type" which means that it is super conformal or Euclidean minimal with planar ends. This implies that all constrained Willmore tori in …
Studied are moduli spaces of self dual or anti-self dual connections on noncommutative 4-manifolds, especially deformation quantization of compact spin Riemannian 4-manifolds and their isometry groups have 2-torus subgroup. Then such moduli spaces of irreducible modules associated with highestweights of compact connect…