Two-point b.v.p. for multivalued equations with weakly regular r.h.s.

A two-point boundary value problem associated to a semilinear multivalued evolution equation is investigated, in reflexive and separable Banach spaces. To this aim, an original method is proposed based on the use of weak topologies and on a suitable continuation principle in Fréchet spaces. Lyapunov-like functions are introduced, for proving the required transversality condition. The linear part can also depend on the state variable x and the discussion comprises the cases of a nonlinearity with sublinear growth in x or of a noncompact valued one. Some applications are given, to the study of periodic and Floquet boundary value problems of partial integro-differential equations and inclusions appearing in dispersal population models. Comparisons are included, with recent related achievements.     

The E.E.C. and the development of O.R.

The growth of the E.E.C. has brought about a change in the scale of many organizational problems and a change in the ways that they can be tackled. Accordingly it is plausible that the techniques of O.R. should develop in response to these changes. This paper examines some desirable developments and suggests ways in which they might be achieved by adapting methods devised in other fields for similar problems.     

On the r.e. predecessors of d.r.e. degrees

Let d be a Turing degree containing differences of recursively enumerable sets (d.r.e.sets) and R[d] be the class of less than d r.e. degrees in whichd is relatively enumerable (r.e.). A.H.Lachlan proved that for any non-recursive d.r.e. d R[d] is not empty. We show that the r.e. degree defined by Lachlan for a d.r.e.set d is just the minimum degree in which D is r.e. Then we study for a given d.r.e. degree d class R[d] and show that there exists a d.r.e.d such that R d] has a minimum element 0. The most striking result of the paper is the existence of d.r.e. degrees for which R[d] consists of one element. Finally we prove that for some d.r.e. d R[d] can be the interval [a,b] for some r.e. degrees a,b, a b d. Received: 17 January 1996     

Selectively c.c.c. spaces

We present a study about a natural way of defining a selective version of the c.c.c. property. This definition and some related properties were already considered under different names in other works, such as Daniels et al. (1994) [9], Scheepers (2000) [12]. Here we will present some of its relations with other selective properties and we present some examples that show the differences among the properties considered. We also study the behavior of these properties when the products are considered.     

D.c. sets,d.c. functions and nonlinear equations

Ad.c. set is a set which is the difference of two convex sets. We show that any set can be viewed as the image of a d.c. set under an appropriate linear mapping. Using this universality we can convert any problem of finding an element of a given compact set in ⁿ into one of finding an element of a d.c. set. On the basis of this approach a method is developed for solving a system of nonlinear equations—inequations. Unlike Newton-type methods, our method does not require either convexity, differentiability assumptions or an initial approximate solution.The revision of this paper was produced during the author's stay supported by a Sophia lecturing-research grant at Sophia University (Tokyo, Japan).     

A Quasi Fixed-Point Theorem for a Product of u.s.c. or o.l.s. Correspondences with an Economic Application

In the first place, we present a quasi fixed-point theorem for a correspondence defined on some infinite-dimensional locally convex topological vector space such that some variables have open lower sections and the other ones are upper semicontinuous.In the second place, we propose a direct application of the quasi fixed-point result in an economic model. More precisely, we prove a nonemptiness result of the core of an exchange economy with asymmetric information, a continuum of states and a finite number of commodities.     

Choosing the Operational Research Programme for B.I.S.R.A

This paper examines some important problems in the evaluation and selection of research projects, with particular reference to operational research projects in a central industry research organization. A method for project evaluation is suggested which provides data suitable for use in a powerful and flexible formal procedure for project selection. In evaluating a project, the assessment of resource requirements is based on a probabilistic network plan of the project, and the estimates of benefits are derived from the marginal effects on the industry of performing or not performing the project, using discounted cash flow techniques. The procedure for project selection chooses not only the projects to be undertaken, but also the team sizes that should be used. A wide variety of constraints can be imposed on the system to reflect different aspects of management policy or other special factors. The procedures described have been implemented, and have proved well worth while.     

S.A.G.B.I. bases for rings of formal modular seminvariants

We use the theory of S.A.G.B.I. bases to construct a generating set for the ring of invariants for the four and five dimensional indecomposable modular representations of a cyclic group of prime order. We observe that for the four dimensional representation the ring of invariants is generated in degrees less than or equal to 2p–3, and for the five dimensional representation the ring of invariants is generated in degrees less than or equal to 2p–2. Received: January 22, 1997     

Optimization of the Relaxation Parameter for S.S.O.R. and A.D.I. Preconditioning

We present and compare several approaches for the optimization of the relaxation parameter both for A.D.I. and S.S.O.R. basic iteration and preconditioning conjugate gradient method. For each kind of preconditioning a detailed link between estimates of the spectral radius of the iteration matrix and of the condition number resulting from preconditioning is proposed. It allows to choose the best approach in order to obtain the optimal relaxation parameter and the corresponding optimal estimates either of the spectral radius of the iteration matrix and of the resulting condition mumber of the S.S.O.R. and A.D.I. preconditioning.     

Relative entropy tuples,relative u.p.e. and c.p.e. extensions

Relative entropy tuples both in topological and measure-theoretical settings, relative uniformly positive entropy (rel.-u.p.e.) and relative completely positive entropy (rel.-c.p.e.) are studied. It is shown that a relative topological Pinsker factor can be deduced by the smallest closed invariant equivalence relation containing the set of relative entropy pairs. A relative disjointness theorem involving relative topological entropy is proved. Moreover, it is shown that the product of finite rel.-c.p.e. extensions is also rel.-c.p.e.. The first author is partially supported by NCET, NNSF of China (no. 10401031) and CNRS-K.C.Wong Fellowship. The second author is supported by the national key project for basic science (973). The third author is supported by NNSF of China (no. 10401031).     

Monotone factors of I.I.D. processes

LetB(p) andB(q) be Bernoulli shifts on {0, 1,...,d - 1}^ℤ. Ifh(p)>h(q), it is a classical theorem of Sinai that there is a factor map takingB(p) toB(q). If, in addition,p stochastically dominatesq, we can ask whether there is such a factor map ϕ which is monotone: ϕ(x) _i≤x_i for each coordinatei of almost every pointx. Here we show that there is a monotone finitary code fromB(p) toB(q) in the case whereB(q) is a shift on two symbols.     

The periodogram of an i.i.d. sequence

Periodogram ordinates of a Gaussian white-noise computed at Fourier frequencies are well known to form an i.i.d. sequence. This is no longer true in the non-Gaussian case. In this paper, we develop a full theory for weighted sums of non-linear functionals of the periodogram of an i.i.d. sequence. We prove that these sums are asymptotically Gaussian under conditions very close to those which are sufficient in the Gaussian case, and that the asymptotic variance differs from the Gaussian case by a term proportional to the fourth cumulant of the white noise. An important consequence is a functional central limit theorem for the spectral empirical measure. The technique used to obtain these results is based on the theory of Edgeworth expansions for triangular arrays.     

On a result of W.A. Kirk and L.M. Saliga

We prove that the conclusion of a result of Kirk and Saliga (J. Comput. Appl. Math. 113 (2000) 141, Theorem 4.3, p. 149) remain valid for a wide class of contractive gauge functions.     

The Influence of P. A. Florensky on N. N. Luzin

The study of the early history of the Moscow school of the theory of functions has been greatly enhanced by the discovery of correspondence between one of its founders, N. N. Luzin, and the priest, theologian, philosopher, and scientist P. A. Florensky. The correspondence reveals that Luzin experienced a profound spiritual crisis in 1905 when his materialist worldview collapsed. This crisis continued for three years and was finally resolved when Luzin had a decisive encounter with the religious philosophy of Florensky. After this, Luzin's interest in mathematics gradually revived until he was able, by 1909, to commit himself to a career in mathematics.Copyright 1998 Academic Press.Les études concernant l'histoire des débuts de l'école moscovite de la théorie des functions ont été grandement éclairées par la découverte d'une correspondance entre l'un de ses fondateurs, N. N. Luzin, et P. A. Florenski, un prêtre, théologien, philosophe, et savant. Cette correspondance révèle que Luzin a traversé une crise spirituelle profonde à partir de 1905, lorsque sa perspective matérialiste du monde s'est effondrée. Cette crise a duré trois ans, et a trouvé sa résolution dans la rencontre décisive de Luzin avec la philosophie religieuse de Florenski. Par la suite, l'intérêt de Luzin pour les mathématiques s'est progressivement ravivé, jusqu'à ce qu'il soit en mesure de décider, en 1909, de consacrer sa vie aux mathématiques.Copyright 1998 Academic Press.[formula]Copyright 1998 Academic Press.MSC 1991 subject classification: 01A30, 01A60, 01A80, 03-03     

On results of G. Brosch and T.C. Alzahary

We prove a uniqueness theorem for two non-constant meromorphic functions sharing three values which improves a recent result of T.C. Alzahary. As a consequence of our main result we also improve a theorem of G. Brosch.     

Mathematical bibliography for W. H. and G. C. Young

An annotated bibliography, ordered by the time of writing, of all the mathematical publications (1895–1929)_ of the couple Grace Chisholm Young (1868–1944) and William Henry Young (1863–1942), preceded by a brief biographical note with references to secondary sources.     

The mathematics of F. J. Almgren, Jr.

Frederick Justin Almgren, Jr, one of the world’s leading geometric analysts and a pioneer in the geometric calculus of variations, died on February 5, 1997 at the age of 63 as a result of myelodysplasia. Throughout his career, Almgren brought great geometric insight, technical power, and relentless determination to bear on a series of the most important and difficult problems in his field. He solved many of them and, in the process, discovered ideas which turned out to be useful for many other problems. This article is a more-or-less chronological survey of Almgren’s mathematical research. (Excerpts from this article appeared in the December 1997 issue of theNotices of the American Mathematical Society.) Almgren was also an outstanding educator, and he supervised the thesis work of nineteen PhD students; the 1997 volume 6 issue of the journalExperimental Mathematics is dedicated to Almgren and contains reminiscences by two of his PhD students and by various colleagues. A general article about Almgren’s life appeared in the October 1997Notices of the American Mathematical Society [MD]. See [T3]for a brief biography.     

Comments on the paper by A. V. Borisov,A. A. Kilin,I. S. Mamaev “How to control the Chaplygin ball using rotors. II”

In this paper we consider the control of a dynamically asymmetric balanced ball on a plane in the case of slipping at the contact point. Necessary conditions under which a control is possible are obtained. Specific algorithms of control along a given trajectory are constructed.     

O.R. Education — A Survey of Young O.R. Workers

This paper presents the results of a survey into O.R. education that was conducted with the help of those attending the Young O.R. Conference (YOR II) held at Nottingham University in March 1982. The results of a workshop debate held at the conference into the direction of O.R. education are also discussed.The conclusions drawn are that O.R. education in this country appears to be quite successful but that it is failing to deal satisfactorily with a number of issues. These issues relate to keeping up-to-date with changes in computer technology and their impact upon O.R. workers; the teaching of methodology to deal with ill-defined problems; preparation for the political and working environment of organizations; and the fostering of desirable personal characteristics.     

Corporate Planning and Its Use of O.R. in the N.C.B.: A Personal View

Moving from Operational Research to Corporate Planning within one organisation is a rather modest change, which nevertheless leads to a different perspective. While still an advisory function, Corporate Planning, to be successful, has to maintain itself at the centre of a `messy' system tackling `messy' problems. Holding on to a clear strategy in such circumstances is not only difficult but vital. The success of the strategy depends on its robustness and ability to adapt to new circumstances. Recent debates in the O.R. literature have focused on the importance of robustness and the nature of uncertainty using the paradigms of rational and bureaucratic processes. This is a useful perspective from which to view our activities and the relative roles of Operational Research and Corporate Planning, either separately or together. The term `mature' O.R. is used to differentiate research that has been built up over many years in the N.C.B. from the problem solving activity often used to characterise O.R. The challenge is to prevent maturity developing into old age.