arXiv subjects

Dmytro Yeroshkin

Publications and source records attributed to Dmytro Yeroshkin.

9 recordsLinked to original sources

arXiv2021

Ricci Flow on Torus Bundles

In this paper we compute the Ricci flow formulas for invariant metrics on prinicpal $G$-bundles compatible with the connection. Our primary focus is on torus bundles which we use to study a notion of Bakry-Émery Ricci flow as well as Ricci flow on circle bundles over Kähler-Einstein manifolds. The latter application gives us solutions to Ricci flows on Heisenberg groups and implicit solutions to Ricci flows on Berger 3-spheres and several other 3-dimensional manifolds.

math.DG↗

arXiv2021

On Levine's notorious hat puzzle

The Levine hat game requires $n$ players, each wearing an infinite random stack of black and white hats, to guess the location of a black hat on their own head seeing only the hats worn by all the other players. They are allowed a strategy session before the game, but no further communication. The players collectively win if and only if all their guesses are correct. In this paper we give an overview of what is known about strategies for this game, including an extended discussion of the case with $n = 2$ players (and a conjecture for an optimal strategy in this case). We also prove that $V_n$, the optimal value of the joint success probability in the $n$-player game, is a strictly decreasing function of $n$.

math.CO↗

arXiv2020

Holonomy of Manifolds with Density

In this paper we discuss some examples and general properties of holonomy groups of $\nabla^φ$ introduced by Wylie and the author, the connection corresponding to the $N=1$ Bakry-Émery Ricci curvature, and also Wylie's $\bar{\mathrm{sec}}_f$. In particular we classify all possible holonomy groups in dimension 2 and also provide two infinite families: $SL_n(\mathbb{R})$ and $SO^+(p,q)$.

math.DG↗

arXiv2017

Connectedness of two-sided group digraphs and graphs

Two-sided group digraphs and graphs, introduced by Iradmusa and Praeger, provide a generalization of Cayley digraphs and graphs in which arcs are determined by left and right multiplying by elements of two subsets of the group. We characterize when two-sided group digraphs and graphs are weakly and strongly connected and count connected components, using both an explicit elementary perspective and group actions. Our results and examples address four open problems posed by Iradmusa and Praeger that concern connectedness and valency. We pose five new open problems.

math.CO↗

arXiv2017

The weighted connection and sectional curvature for manifolds with density

In this paper we study sectional curvature bounds for Riemannian manifolds with density from the perspective of a weighted torsion free connection introduced recently by the last two authors. We develop two new tools for studying weighted sectional curvature bounds: a new weighted Rauch comparison theorem and a modified notion of convexity for distance functions. As applications we prove generalizations of theorems of Preissman and Byers for negative curvature, the (homeomorphic) quarter-pinched sphere theorem, and Cheeger's finiteness theorem. We also improve results of the first two authors for spaces of positive weighted sectional curvature and symmetry.

math.DG↗

arXiv2016

On the geometry of Riemannian manifolds with density

We introduce a new geometric approach to a manifold equipped with a smooth density function that takes a torsion-free affine connection, as opposed to a weighted measure or Laplacian, as the fundamental object of study. The connection motivates new versions of the volume and Laplacian comparison theorems that are valid for the 1-Bakry-Emery Ricci tensor, a weaker assumption than has previously been considered in the literature. As applications we prove new generalizations of Myers' theorem and Cheng's diameter rigidity result. We also investigate the holonomy groups of the weighted connection. We show that they are more general than the Riemannian holonomy, but also exhibit some of the same structure. For example, we obtain a generalization of the de Rham splitting theorem as well as new rigidity phenomena for parallel vector fields. A general feature of all of our rigidity results is that warped or twisted product splittings are characterized, as opposed to the usual isometric products.

math.DG↗

arXiv2015

On Poincare Duality for Orbifolds

In this paper we address the relation between the orbifold fundamental group and the topology of the underlying space. In particular, under the assumption that the orbifold fundamental group is equal to the fundamental group of the underlying space, we prove Poincaré Duality for orbifolds of dimension 4 and 5.

math.AT↗

arXiv2014

On Geometry and Topology of 4-Orbifolds

We prove an analogue of the result of Hsiang and Kleiner for 4-dimensional compact orbifolds with positive curvature and an isometric circle action. Additionally, we prove that when the underlying space is simply connected, then the orbifold fundamental group provides a bound on the failure of integer-valued Poincare Duality of the underlying space, and if the orbifold is simply connected, then ineteger-valued Poincre Duality holds for the underlying space.

math.DG↗

arXiv2014

Orbifold Biquotients of SU(3)

One of the main methods of constructing new spaces with positive or almost positive curvature is the study of biquotients first studied in detail by Eschenburg. We classify orbifold biquotients of the Lie Group $SU(3)$, and construct a new example of a 5-dimensional orbifold with almost positive curvature. Furthermore, we extend the work of Florit and Ziller on the geometric properties of the orbifolds $SU(3)//T^2$.

math.DG↗