On the fundamental group of Riemannian manifolds with nonnegative Ricci curvature

In 1968 Milnor conjectured that the fundamental group of any complete Riemannian manifold with nonnegative Ricci curvature is finitely generated. In this paper we obtain two results concerning Milnor’s conjecture. We first prove that the generators of fundamental group can be chosen so that it has at most logarithmic growth. Secondly we prove that the conjecture is true if additional the volume growth satisfies certain condition.     

On the fundamental group of some open manifolds

We study fundamental groups of noncompact Riemannian manifolds. We find conditions which ensure that the fundamental group is trivial, finite or finitely generated.     

Tits topology and fundamental groups of compact Riemannian manifolds

Let M be a compact Riemannian manifold without conjugate points. We generalize the Tits topology on the ideal boundary of the universal covering space of M. Then we show that if π₁(M) is amenable and is compact with respect to the Tits topology, then M is flat. This work was supported by Grant No.R01-2006-000-10047-0(2006) from the Basic Research Program of the Korea Science & Engineering Foundation.     

Surgery of closed manifolds with dihedral fundamental group

In the paper the obstruction groups to obtaining simple homotopy equivalence by surgery from normal degree 1 maps of closed manifolds with dihedral fundamental group are computed. The cases of trivial orientation for the dihedral group and nontrivial orientation for the order 2 cyclic subgroup are considered. New results concerning the Browder-Livesey groups and natural maps ofL-groups arising in index 2 inclusions of the cyclic group into the dihedral group are obtained.Translated fromMatematicheskie Zametki, Vol. 64, No. 2, pp. 238–250, August, 1998.The work of the first-named author was partially supported by of the Grant of the President of the Russian Federation, grant No. 96-15-96841. The work of the second-named author was partially suported the Ministry of Science and Technology of the Republic of Sloveniya, grant No. J1-7039-0101-95.     

Obstructions to splitting manifolds with infinite fundamental group

In this paper we calculate the obstruction groups to splitting along one-sided submanifolds when the fundamental group of the submanifold is isomorphic to or /2. We also consider the case where the obstruction group is not a Browder-Livesey group. We construct a new Levine braid that connects the Wall groups to the obstruction group for splitting. We solve the problem of the mutual disposition of images of several natural maps in Wall groups for finite 2-groups with exceptional orientation character.Translated fromMatematicheskie Zametki, Vol. 60, No. 2, pp. 163–175, August, 1996.This research was supported by the Russian Foundation for Basic Research under grant No. 93-011-1402.     

Metric projection onto subsets of compact connected two-dimensional Riemannian manifolds

The paper is focused on combinatorial properties of the metric projection P _E of a compact connected Riemannian two-dimensional manifold M ² onto its subset E consisting of k closed connected sets E _j . A point x ∈ M ² is called singular if P _E (x) contains points from at least three distinct E _j . An exact estimate of the number of singular points is obtained in terms of k and the type of the manifold M ². A similar estimate is proved for subsets E of a normed plane consisting of a finite number of connected components.     

On generalized recurrent Riemannian manifolds

The object of the present paper is to study a type of Riemannian manifolds called generalized recurrent manifolds. We have constructed two concrete examples of such a manifold whose scalar curvature is non-zero non-constant. Some other properties have been considered. Among others it is shown that on a generalized recurrent manifold with constant scalar curvature, Weyl-semisymmetry and semisymmetry are equivalent. Sufficient condition for a generalized recurrent manifold to be a special quasi Einstein manifold is obtained.     

On Gromov's large Riemannian manifolds

Gromov introduced several notions of largeness of Riemannian manifolds and proved that they are all equivalent for manifolds of nonnegative sectional curvature. In this paper, we study the equivalence of these notions in the case of nonnegative Ricci curvature and in particular we give an affirmative answer to one of Gromov's open questions.     

Pointwise characterizations of curvature and second fundamental form on Riemannian manifolds

Let M be a complete Riemannian manifold possibly with a boundary?M.For any C~1-vector field Z,by using gradient/functional inequalities of the(reflecting)diffusion process generated by L:=?+Z,pointwise characterizations are presented for the Bakry-Emery curvature of L and the second fundamental form of?M if it exists.These characterizations extend and strengthen the recent results derived by Naber for the uniform norm‖RicZ‖∞on manifolds without boundaries.A key point of the present study is to apply the asymptotic formulas for these two tensors found by the first author,such that the proofs are significantly simplified.     

Best uniform approximation by harmonic functions on subsets of Riemannian manifolds

We investigate best uniform approximations to bounded, continuous functions by harmonic functions on precompact subsets of Riemannian manifolds. Applications to approximation on unbounded subsets ofR ² are given.Communicated by J. Milne Anderson.     

On the fundamental group of compact homogeneous manifolds carrying an invariant fat distribution

We show that a homogeneous space of a compact Lie group carrying an invariant fat distribution must have finite fundamental group.     

On the existence of H-surfaces into Riemannian manifolds

This paper considers the existence of a local minimizer of a conformally invariant functional defined on a space of maps of a closed Riemann surface into a compact Riemannian manifold . The functional is defined for a given tensor on of type (1,2) and we call its extremal an -surface. In fact, we prove that there exists a local minimizer of the functional in a given homotopy class under certain conditions on , and the minimum of the Dirichlet integral of maps of the homotopy class. Received January 21, 1994 / Received in revised form October 24, 1995 / Accepted March 15, 1996     

Complete affine locally flat manifolds with a free fundamental group

Examples of free noncommutative subgroups of the affine group A(3), which act properly discontinuously on ³, are constructed in the paper. These examples refute a conjecture of Milnor to the effect that the fundamental group of any complete affine locally flat manifold contains a sòlvable subgroup of finite index.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 134, pp. 190–205, 1984.     

On the essential spectrum of complete Riemannian manifolds with finite volume

In this paper, under some growth condition on the volume of a geodesic ball with radiusr, we compute the essential spectrum of some class of Riemannian manifolds with finite volume. This result refines some earlier results of R. Brooks. Research supported by the National Natural Science Fundation of China.