We show that an isometric immersion of an n−dimensional compact Riemannian manifold of non-negative Ricci curvature with scalar curvature always less than n(n−1)λ−2 into a Euclidean space of dimension n + 1 can never be contained in a ball of radius λ.

In this paper a variant of Banach's contraction principle is established. By using the properties of the spectral radius of a bounded linear operator A defined in a suitable Banach space, we conclude that another operator A has exactly one fixed point in this space. In the second part of this paper some applications are given.

In this paper, we prove a Gelfand-Mulvey type of duality for a certain class of rings which includes the Gelfand rings. We also show that the Maximal Ideal Theorem (MIT) can be replaced by the Prime Ideal Theorem (PIT) in the original Gelfand-Mulvey duality.

We identify the multiplier space of continuous vector-valued function spaces as the bounded continuous multiplier-valued space in the strong topology.

In this paper, we first prove an improved version of the selection theorem of Yannelis-Prabhakar and next prove a fixed point theorem in a non-compact product space. As applications, an intersection theorem and two equilibrium existence theorems for a non-compact abstract economy are given.

In this paper, a generalisation of the Andersen, Hilton, Rodger Theorem for embedding partial idempotent latin squares is proved. This result is then used to prove that a partial directed m-cycle system of order n can be embedded in a directed m-cycle system of order (2n + 1)m if m is odd, of order 2nm if m ≥ 8 is even, 12n + 1 if m = 6 and approximately 2n + √2n if m = 4.

We investigate the structure of the C*-algebras 𝒪ρ constructed by Doplicher and Roberts from the intertwining operators between the tensor powers of a representation ρ of a compact group. We show that each Doplicher-Roberts algebra is isomorphic to a corner in the Cuntz-Krieger algebra 𝒪A of a {0,1}-matrix A = Aρ associated to ρ. When the group is finite, we can then use Cuntz's calculation of the K-theory of 𝒪A to compute K*(𝒪ρ).

Uniqueness and regularity of periodic solutions to the semilinear dissipative wave equation with small parameter ∈ > 0,

are investigated when g(u) has a certain ‘critical’ nonlinearity.

Let G be a group and k an integer greater than 1. We say that G has the square property of k-sets and we write G ∈ DS(k) if |X2| < k2 for any subset X of G of order k. The groups in DS(2) are exactly the Dedekind groups, as Freiman showed. The class .DS(3) has been recently studied by Berkovich, Freiman and Praeger. In this paper we complete the classification of DS(3)-groups by characterising finite 2-groups of exponent 4 in DS(3).

For any α ∈ (0, 1), examples of C∞ functions fα: [0, 1] → [0, 1] with zero topological entropy and possessing a δ−scrambled set of Lebesgue measure α are given. This answers a question posed by Smítal.

We prove that some metric inequalities imply weak or weak-star normal structure. In particular, we prove that every ω*-compact convex set in the space C1(lp, lq) of nuclear operators from lp into lq, (1 < p, q < ∞, 1/p + 1/q = 1) has the weak* normal structure. This generalises a recent result of C. Lennard.

Let Γ.𝒜 be the semi-direct product group of a nuclear Lie group Γ with the additive group 𝒜 of a real nuclear vector space. We give an explicit description of all the continuous representations of Γ.𝒜 the restriction of which to 𝒜 is a cyclic unitary representation, and a necessary and sufficient condition for the unitarity of such cylindrical representations is stated. This general result is successfully used to obtain irreducible unitary representations of the nuclear Lie groups of Riemannian motions, and, in the setting of the theory of multiplicative distributions initiated by I.M. Gelfand, it is proved that for any connected real finite dimensional Lie group G and for any strictly positive integer k there exist non located and non trivially decomposable representations of order k of the nuclear Lie group (M;G) of all the G-valued test-functions on a given paracompact manifold M.

The authors give affirmative answers to two questions of H. Neumann and Wiegold on linked embeddings of groups.

We generalise Chuang's inequality to vector meromorphic functions, which is originally a sort of extension of Nevanlinna's second fundamental theorem.

In this paper we study the variational-like inequalities, which generalise some results of Parida, Sahoo and Kumar, and we also investigate the quasivariational-like inequalities. We establish some existence theorems of a solution for the above problem.

Let p be a prime and d, e positive integers. We prove that a regular d-generator metabelian p-group whose commutator subgroup has exponent pe has nilpotency class at most e(p – 2) + 1 unless e = 1, d > 2, p > 2 when the class can be p and these bounds are best possible.

The one-sided Laplace transform is defined on a space of generalised functions called transformable Boehmians. The space of one-sided Laplace transformable distributions is shown to be a proper subspace of transformable Boehmians. Some basic properties of the Laplace transform are investigated. An inversion formula and an Abelian theorem of the final type are obtained.