It is known that there are no real hypersurfaces with parallel structure Jacobi operators in a nonflat complex space form. In this paper, we classify real hypersurfaces in a nonflat complex space form whose structure Jacobi operator is cyclic-parallel.

Let (S, +) be a semigroup and (H, +) be a group (neither necessarily commutative). Suppose that J ⊂ 2s is a proper ideal in S such that

and Ω(J) = {M ⊂ S2 : there exists U(M)∈ J with M [x] ∈ J for x ∈ S/U(M)}, where M[x] = {y ∈ S : (y, x) ∈ M}. We show that if f : S → H is a function satisfying

then there exists exactly one additive function F : S → H with F(x) = f(x) J-almost everywhere in S.

We also prove some results concerning regularity of the function F.

Modules whose nonzero endomorphisms are epimorphisms and modules whose nonzero endomorphisms are monomorphisms are considered in this paper. We prove that these two classes of modules are dual to each other via Morita duality. We also prove that a left artinian ring R with Jacobson radical J has a Morita duality if either (1) J/J2 is a central bimodule; or (2) R is artinian right duo and R/J is commutative.

In this paper, by using the theory of reproducing kernel Hilbert spaces and the pair correlation formula constructed by Chandee et al. [‘Simple zeros of primitive Dirichlet $L$-functions and the asymptotic large sieve’, Q. J. Math.65(1) (2014), 63–87], we prove that at least 93.22% of low-lying zeros of primitive Dirichlet $L$-functions are simple in a proper sense, under the assumption of the generalised Riemann hypothesis.

The main result shows that a small perturbation of a univalent function is again a univalent function, hence a univalent function has a neighbourhood consisting entirely of univalent functions. For the particular choice of a linear function in the hypothesis of the main theorem, we obtain a corollary which is equivalent to the classical Noshiro–Warschawski–Wolff univalence criterion. We also present an application of the main result in terms of Taylor series, and we show that the hypothesis of our main result is sharp.

We construct a group G with the properties stated in the title.

Dedicated to Professor Koichi Ogiue on his sixtieth birthday

We show that the only parallel surfaces in SL (2,ℝ) are rotational surfaces with constant mean curvature.

Suppose that G is a graph with vertex set V (G) and edge set E (G), and let g and f be two non-negative integer-valued functions defined on V (G) such that g (x) ≤ f (x) for each x ∈ V (G). A (g, f)-factor of G is a spanning subgraph F of G such that g (x) ≤ dF (x) ≤ f (x) for each x ∈ V (F). In this paper, some sufficient conditions for a graph to have a (g, f)-factor are given.

Let Un be a U-statistic whose kernel depends on the size n of the sample under consideration. It is shown that when Un is suitably normalised its distribution function differs in Lp norm from the distribution function of a standard normal variable by a term of O(n-½).

We show that any Cuntz-Krieger algebra A over an infinite 0–1 matrix A may be realised as a Cuntz-Pimsner algebra X for a Hilbert bimodule X over a suitable Abelian C*-algebra with totally disconnected spectrum. Using Pimsner's six-term exact sequence for the KK-groups we calculate the K-groups of A. We also give a description of the corresponding Toeplitz algebra X in terms of generators and relations.

The familiar notion of the determinant is generalised to include rectangular matrices. An expression for a normalised generalised inverse of a matrix is given in terms of its determinant and a possible generalisation of the Schur complement is discussed as a simple application.

In this paper, we show that any ascending HNN-extension of a finitely presented group is properly 3-realisable. We recall that a finitely presented group G is said to be properly 3-realisable if there exists a compact 2-polyhedron K with π1(K) ≅ G and whose universal cover has the proper homotopy type of a (PL) 3-manifold (with boundary).

Recently, Pollack and Shevelev [‘On perfect and near-perfect numbers’, J. Number Theory 132 (2012), 3037–3046] introduced the concept of near-perfect numbers. A positive integer $n$ is called near-perfect if it is the sum of all but one of its proper divisors. In this paper, we determine all near-perfect numbers with two distinct prime factors.

Let G be a finite group. A nontrivial subgroup M of G is called a CC-subgroup if M contains the centralizer in G of each of its nonidentity elements. The purpose of this paper is to classify groups with a CC-subgroup of order divisible by 3. Simple groups satisfying that condition are completely determined.

We study the notion (for categories of modules) dual to that of torsion radical and its connections with projective modules.

Torsion radicals in categories of modules have been studied extensively in connection with quotient categories and rings of quotients. (See [8], [12] and [13].) In this paper we consider the dual notion, which we have called a cotorsion radical. We show that the cotorsion radicals of the category RM correspond to the idempotent ideals of R. Thus they also correspond to TTF classes in the sense of Jans [9].

It is well-known that the trace ideal of a projective module is idempotent. We show that this is in fact a consequence of the natural way in which every projective module determines a cotorsion radical. As an application of these techniques we study a question raised by Endo [7], to characterize rings with the property that every finitely generated, projective and faithful left module is completely faithful. We prove that for a left perfect ring this is equivalent to being an S-ring in the sense of Kasch. This extends the similar result of Morita [15] for artinian rings.

Order components of a finite group are introduced in [4]. We prove that, for every q, PSL (5,q) can be uniquely determined by its order componets. A main consequence of our result is the validity of Thompson's conjecture for the groups under consideration.

We consider the Brocard–Ramanujan type Diophantine equation y2=x!+A and ask about values of A∈ℤ for which there are at least three solutions in the positive integers. In particular, we prove that the set 𝒜 consisting of integers with this property is infinite. In fact we construct a two-parameter family of integers contained in 𝒜. We also give some computational results related to this equation.

We study analytic properties of certain infinite products of cyclotomic polynomials that generalise some products introduced by Mahler. We characterise those that have the unit circle as a natural boundary and use associated Dirichlet series to obtain their asymptotic behaviour near roots of unity.

On a Banach space the numerical range of an unbounded operator has a certain density property in the scalar field. Consequently all hermitian and dissipative operators are bounded. For a smooth or separable or reflexive Banach space the numerical range of an unbounded operator is dense in the scalar field.