scholarly journals Harmonic branched coverings and uniformization of CAT(k) spheres

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Christine Breiner ◽  
Chikako Mese
Keyword(s):  
Harmonic Map ◽  
Branched Coverings ◽  
Curvature Bound ◽  
Branched Covering

Abstract Let S be a surface with a metric d satisfying an upper curvature bound in the sense of Alexandrov (i.e. via triangle comparison). We show that an almost conformal harmonic map from a surface into ( S , d ) {(S,d)} is a branched covering. As a consequence, if ( S , d ) {(S,d)} is homeomorphically equivalent to the 2-sphere 𝕊 2 {\mathbb{S}^{2}} , then it is conformally equivalent to 𝕊 2 {\mathbb{S}^{2}} .

Strongly-cyclic branched coverings and the Alexander polynomial of knots in rational homology spheres

2007 ◽  
Vol 142 (2) ◽  
pp. 259-268 ◽  
Author(s):  
YUYA KODA
Keyword(s):  
Fundamental Group ◽  
Homology Group ◽  
Alexander Polynomial ◽  
Homology Sphere ◽  
Cyclic Covering ◽  
Rational Homology ◽  
Branched Coverings ◽  
Branched Covering ◽  
Rational Homology Spheres ◽  
Rational Homology Sphere

AbstractLet K be a knot in a rational homology sphere M. In this paper we correlate the Alexander polynomial of K with a g-word cyclic presentation for the fundamental group of the strongly-cyclic covering of M branched over K. We also give a formula for the order of the first homology group of the strongly-cyclic branched covering.

scholarly journals Indecomposable branched coverings over the projective plane by surfaces M with χ(M) ≤ 0

2018 ◽  
Vol 27 (05) ◽  
pp. 1850030
Author(s):  
Natalia A. Viana Bedoya ◽  
Daciberg Lima Gonçalves ◽  
Elena A. Kudryavtseva
Keyword(s):  
Projective Plane ◽  
Euler Characteristic ◽  
Covering Surface ◽  
Branched Coverings ◽  
Branched Covering

In this work, we study the decomposability property of branched coverings of degree [Formula: see text] odd, over the projective plane, where the covering surface has Euler characteristic [Formula: see text]. The latter condition is equivalent to say that the defect of the covering is greater than [Formula: see text]. We show that, given a datum [Formula: see text] with an even defect greater than [Formula: see text], it is realizable by an indecomposable branched covering over the projective plane. The case when [Formula: see text] is even is known.

On the Branch Points in the Branched Coverings of Links

1985 ◽  
Vol 28 (2) ◽  
pp. 165-173
Author(s):  
Shintchi Kinoshita
Keyword(s):  
Fundamental Group ◽  
Symmetric Group ◽  
Branch Points ◽  
Branched Coverings ◽  
Branched Covering ◽  
Exact Position ◽  
Monodromy Map

AbstractLet l be a polygonal link in a 3-sphere S3 and a branched covering of l, which depends on the choice of a monodromy map ϕ. Let be the link in over l. In this paper we determine the exact position of in for some cases. For instance, if l is a torus link ((n + 1)p, n) and ϕ is an appropriate monodromy map of the fundamental group of S3 - l into the symmetric group of degree n + 1, then is an S3 and l is a torus link (np,n2). The 3-fold irregular branched covering of a doubled knot k is an S3, if it exists. The position of the link over k is shown in a figure. The link over knot 61 is obtained by K. A. Perko and the author, independently, and shown without proof in a paper by R. H. Fox [Can. J. Math. 22 (1970), 193-201]. The result mentioned in the above includes this case.

scholarly journals ON THE EXISTENCE OF BRANCHED COVERINGS BETWEEN SURFACES WITH PRESCRIBED BRANCH DATA, II

2008 ◽  
Vol 17 (07) ◽  
pp. 787-816 ◽  
Author(s):  
EKATERINA PERVOVA ◽  
CARLO PETRONIO
Keyword(s):  
Projective Plane ◽  
Double Point ◽  
Total Degree ◽  
Euler Characteristics ◽  
Branched Coverings ◽  
Branched Covering ◽  
Closed Surfaces ◽  
Branching Points

If [Formula: see text] is a branched covering between closed surfaces, there are several easy relations one can establish between the Euler characteristics [Formula: see text] and χ(Σ), orientability of Σ and [Formula: see text], the total degree, and the local degrees at the branching points, including the classical Riemann–Hurwitz formula. These necessary relations have been shown to be also sufficient for the existence of the covering except when Σ is the sphere 𝕊 (and when Σ is the projective plane, but this case reduces to the case Σ = 𝕊). For Σ = 𝕊 many exceptions are known to occur and the problem is widely open.Generalizing methods of Baránski, we prove in this paper that the necessary relations are actually sufficient in a specific but rather interesting situation. Namely under the assumption that Σ = 𝕊, that there are three branching points, that one of these branching points has only two pre-images with one being a double point, and either that [Formula: see text] and that the degree is odd, or that [Formula: see text] has genus at least one, with a single specific exception. For the case of [Formula: see text] we also show that for each even degree there are precisely two exceptions.

Infinite time blow-up for half-harmonic map flow from R into S1

2021 ◽  
Vol 143 (4) ◽  
pp. 1261-1335
Author(s):  
Yannick Sire ◽  
Juncheng Wei ◽  
Youquan Zheng
Keyword(s):  
Blow Up ◽  
Harmonic Map ◽  
Infinite Time ◽  
Harmonic Map Flow

scholarly journals Local Regularity for the Harmonic Map and Yang–Mills Heat Flows

2021 ◽  
Author(s):  
Ahmad Afuni
Keyword(s):  
Riemannian Manifolds ◽  
Harmonic Map ◽  
Local Regularity ◽  
Yang Mills ◽  
Heat Flows ◽  
Singular Sets ◽  
Regularity Results ◽  
Local Monotonicity ◽  
Partial Differ ◽  
Singular Time

AbstractWe establish new local regularity results for the harmonic map and Yang–Mills heat flows on Riemannian manifolds of dimension greater than 2 and 4, respectively, obtaining criteria for the smooth local extensibility of these flows. As a corollary, we obtain new characterisations of singularity formation and use this to obtain a local estimate on the Hausdorff measure of the singular sets of these flows at the first singular time. Finally, we show that smooth blow-ups at rapidly forming singularities of these flows are necessarily nontrivial and admit a positive lower bound on their heat ball energies. These results crucially depend on some local monotonicity formulæ for these flows recently established by Ecker (Calc Var Partial Differ Equ 23(1):67–81, 2005) and the Afuni (Calc Var 555(1):1–14, 2016; Adv Calc Var 12(2):135–156, 2019).

Branched Coverings and Minimal Free Resolution for Infinite-Dimensional Complex Spaces

2003 ◽  
Vol 10 (1) ◽  
pp. 37-43
Author(s):  
E. Ballico
Keyword(s):  
Projective Space ◽  
Projective Spaces ◽  
Free Resolution ◽  
Complete Intersections ◽  
Vanishing Theorem ◽  
Sheaf Cohomology ◽  
Minimal Free Resolution ◽  
Branched Coverings ◽  
Infinite Dimensional ◽  
Complex Spaces

Abstract We consider the vanishing problem for higher cohomology groups on certain infinite-dimensional complex spaces: good branched coverings of suitable projective spaces and subvarieties with a finite free resolution in a projective space P(V ) (e.g. complete intersections or cones over finitedimensional projective spaces). In the former case we obtain the vanishing result for H 1. In the latter case the corresponding results are only conditional for sheaf cohomology because we do not have the corresponding vanishing theorem for P(V ).

scholarly journals Uniqueness and nonuniqueness of limits of Teichmüller harmonic map flow

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
James Kohout ◽  
Melanie Rupflin ◽  
Peter M. Topping
Keyword(s):  
Constant Curvature ◽  
Harmonic Map ◽  
Gradient Flow ◽  
Minimal Immersion ◽  
Curvature Surface ◽  
Previous Theory ◽  
Target Manifold ◽  
Harmonic Map Flow

AbstractThe harmonic map energy of a map from a closed, constant-curvature surface to a closed target manifold can be seen as a functional on the space of maps and domain metrics. We consider the gradient flow for this energy. In the absence of singularities, previous theory established that the flow converges to a branched minimal immersion, but only at a sequence of times converging to infinity, and only after pulling back by a sequence of diffeomorphisms. In this paper, we investigate whether it is necessary to pull back by these diffeomorphisms, and whether the convergence is uniform as {t\to\infty}.

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