λ-Automorphisms of a Riemannian foliation

We study geometric properties of -automorphisms of a Riemannian foliationF which is not harmonic. This notion was first introduced in [KTT] for the case whereF is harmonic. Transversal Killing, affine, conformal, projective fields are all examples of -automorphisms. We derive several general identities for a -automorphism. In particular, we extend the results on the transversal conformal and Killing fields obtained in [PrY], [NY1,2]. Furthermore, we analyse the geometric meaning of the condition appearing in our results.The present studies were supported (in part) by the Basic Science Research Institute Program, Ministry of Education, 1994, Project No. BSRI-94-1404     

The Isometry of Riemannian Manifold to a Sphere

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Pairwise products of moduli of families of curves on a Riemannian Möbius strip

We investigate pairwise products of moduli of families of curves on a Riemannian Möbius strip and obtain estimates for these products. As one of the factors, we consider the modulus of a family of arcs from a broad class of families of this sort (for each of these families, we determine the modulus and extremal metric).     

An Invariant of Gauge Transformations of Contact Riemannian Structures

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Every Sub-Riemannian Manifold Is the Gromov–Hausdorff Limit of a Sequence Riemannian Manifolds

In this paper, we will show that every sub-Riemannian manifold is the Gromov–Hausdorff limit of a sequence of Riemannian manifolds.     

Localization of Chern–Simons type invariants of Riemannian foliations

We prove an Atiyah–Bott–Berline–Vergne type localization formula for Killing foliations in the context of equivariant basic cohomology. As an application, we localize some Chern–Simons type invariants, for example the volume of Sasakian manifolds and secondary characteristic classes of Riemannian foliations, to the union of closed leaves. Various examples are given to illustrate our method.     

Isoparametric Riemannian Submanifolds of ℝ n,k

We prove that, essentially, the only complete, irreducible, and isoparametric Riemannian submanifolds of ^n,k are hyperbolic spaces or isoparametric submanifolds of Euclidean spaces. In particular, a simple and geometric proof of the theorem of Wu is derived.     

λ-Equidistributed sequences of partitions and a theorem of the De Bruijn-Post type

Summary The notion of uniform distribution of a sequence is generalized to sequences of partitions in a separable metric space X. Results concern Riemann integrability with respect to a probability on X, and Riemann approximations of Lebesgue integrals.Lavoro presentato al terzo Convegno nazionale «Analisi reale e teoria della misura» (Capri, 12–16 settembre 1988).     

On Riemannian g-natural Metrics of the Form a.g s + b.g h + c.g v on the Tangent Bundle of a Riemannian Manifold (M, g)

Let (M, g) be a Riemannian manifold and TM its tangent bundle. In [5] we have investigated the family of all Riemannian g-natural metrics G on TM (which depends on 6 arbitrary functions of the norm of a vector u TM). In this paper, we continue this study under some additional geometric properties, and then we restrict ourselves to the subfamily {G=a.g^s + b.g^h + c.g^v, a, b and c are constants satisfying a > 0 and a(a + c) – b² > 0}. It is known that the Sasaki metric g^s is extremely rigid in the following sense: if (TM, g^s) is a space of constant scalar curvature, then (M, g) is flat. Here we prove, among others, that every Riemannian g-natural metric from the subfamily above is as rigid as the Sasaki metric.     

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??A single distribution-free (nonparametric) Phase II exponentially weighted moving average (EWMA) chart based on the Cucconi statistic, referred to as the EWMA-Cucconi (EC) chart, is considered here for simultaneously monitoring shifts in the unknown location and scale parameters of a univariate continuous process. A comparison with some other existing nonparametric EWMA charts is presented in terms of the average, the standard deviation and some percentiles of the run length distribution. Numerical results based on Monte Carlo analysis show that the EC chart provides quite a satisfactory performance. The effect of the Phase I (reference) sample size on the IC performance of the EC chart is studied in detail. The application of the EC chart is illustrated by two real data examples.     

Majorana–Oppenheimer Approach to Maxwell Electrodynamics. Part II. Curved Riemannian Space

The Riemann–Silberstein–Majorana–Oppenheimer approach to the Maxwell electrodynamics in the presence of electrical sources, arbitrary media and curved space-time is investigated within the matrix formalism and tetrad method. Symmetries of the matrix Maxwell equation under transformations of the local gauge complex rotation group SO(3,C) is demonstrated explicitly. Equivalence of the approach to general covariant Proca technique and spinor formalism is shown.     

A class of Kazdan-Warner typed equations on non-compact Riemannian manifolds

In this paper,we discuss a Kazdan-Warner typed equation on certain non-compact Rie- mannian manifolds.As an application,we prove an existence theorem of Hermitian-Yang-Mills-Higgs metrics on holomorphic line bundles over certain non-compact K(?)hler manifolds.     

On a new family of complete G 2-holonomy Riemannian metrics on S 3 × ℝ4

Studying a system of first-order nonlinear ordinary differential equations for the functions determining a deformation of the standard conic metric over S ³ × S ³, we prove the existence of a one-parameter family of complete G ₂-holonomy Riemannian metrics on S ³ × ?⁴.     

Fredholm properties of Riemannian exponential maps on diffeomorphism groups

We prove that exponential maps of right-invariant Sobolev H ^r metrics on a variety of diffeomorphism groups of compact manifolds are nonlinear Fredholm maps of index zero as long as r is sufficiently large. This generalizes the result of Ebin et al. (Geom. Funct. Anal. 16, 2006) for the L ² metric on the group of volume-preserving diffeomorphisms important in hydrodynamics. In particular, our results apply to many other equations of interest in mathematical physics. We also prove an infinite-dimensional Morse Index Theorem, settling a question raised by Arnold and Khesin (Topological methods in hydrodynamics. Springer, New York, 1998) on stable perturbations of flows in hydrodynamics. Finally, we include some applications to the global geometry of diffeomorphism groups.