On a Malkin — Massera theorem : PMM vol. 43, no. 6, 1979 pp. 975–979

The results obtained in [1, 2] are complemented by an assertion on asymptotic stability uniform with respect to t₀, x₀, and also are extended to the problems of asymptotic stability with respect to a part of the variables and of optimal stabilization with respect to a part of the variables.     

Errata and addendum to “On the prime geodesic theorem for hyperbolic ‐manifolds” Math. Nachr. 291 (2018), no. 14–15, 2160–2167

We correct the exponent in the error term of the prime geodesic theorem for hyperbolic 3‐manifolds 1 and in Park's theorem for higher dimensions [ 3 , 2 ].     

Generalized cyclic displacements : PMM vol. 37, n6, 1973, pp. 1135–1137

We consider the generalized cyclic displacements of holonomic mechanical systems with a finite number of degrees of freedom, and their application to integration of the equations of motion.N.G.Chetaev in [1] turned his attention to the formulation of problems dealing with general properties of mechanical systems and connected with the groups of transformations which leave the basic mechanical functions invariant. It was he who introduced [2] the concept of cyclic displacement of a mechanical system with smooth holonomic constraints. This concept was enlarged in [3] in the course of considering a particular case of motion of a mechanical system with three degrees of freedom.     

Kenneth O. May, 1915–1977 : His early life to 1946

Kenneth Ownsworth May graduated from the University of California at Berkeley in 1936 with highest honors in mathematics. The following year he received his Masters degree and became a fellow of the Institute of Current World Affairs, and during the next two years he traveled to England, Europe, and Russia. On his return to the United States he became active in the Communist Party, the consequences of which would plague him for years. He joined the United States Army in 1942, serving with distinction, and after the war returned to Berkeley, where he obtained his Ph.D. in 1946. He immediately accepted an assistant professorship at Carleton College in Northfield, Minnesota, later moving to the University of Toronto.This part of May's biography focuses on the events up to his accepting a position at Carleton College. In this early phase his openness, his emphasis on good communications in the process of education, and his interest in practical procedures emerge which later set the background for his successful career as a leading historian of mathematics and the founding editor of Historia Mathematica.     

On sufficient optimality conditions : PMM vol. 42, no. 6, 1978, pp. 1131–1135

Sufficient conditions of optimality of the control in a nonlinear system are given. This involves a demand for existence of a function with specified properties. If this function is defined in a special manner, then the theorem derived in the paper yields the known theorem of Krotov [1]. A certain relaxation of the sufficient conditions given in [1] is obtained for the problems of the time optimal response in autonomous systems.     

J. Howard Redfield 1879–1944

During much of his life J. Howard Redfield earned his living as an engineer but his main interests lay elsewhere. He performed and wrote music and was a gifted linguist, familiar with almost all European languages, as well as with some African and Asian tongues. In middle age he turned his attention towards combinatorial mathematics but it was not until many years after his death that the mathematical world realized that he had obtained significant results.     

Smooth perturbations the self–adjoint operators defined by the ℋ︁–2–construction

The existence of the wave operators for the self–adjoint operator constructed by ??_–2–construction is discussed in the abstract theory by using Kato's smooth perturbation method. Moreover, the s–matrix is calculated explicitly.     

Eigenvalues of a λ – Rational Sturm– Liouville Problem

The Sturm – Liouville problem (1.1), (1.2) is considered, which depends rationally on the eigenvalue parameter. Estimates for the eigenvalues and especially for the embedded eigenvalues are proved. Moreover, conditions for the non – existence of embedded eigenvalues are given.