The radius of almost convexity of order α in the class of univalent functions

In this paper the radius of almost convexity of order in the class of functions f(z)=z+₂z²+... analytic and univalent in ¦z¦<1 is found. The solution to a problem of A. Renyi is given in this connection.Translated from Matematicheskii Zametki, Vol. 20, No. 1, pp. 105–112, January, 1976.     

Improvement of the Ul’yanov inequality for mixed moduli of smoothness for functions with lacunary Fourier coefficients

An inequality for the mixed moduli of smoothness for functions with lacunary Fourier coefficients improving the known Ul’yanov inequality for moduli of smoothness is obtained in the paper.     

On the unit group and the class number¶of certain composita of two real quadratic fields

The purpose of this paper is to exhibit a new family of real bicyclic biquadratic fields K for which we can write the Hasse unit index of the group generated by the units of the three quadratic subfields in the unit group E _K of K. As a byproduct, one can explicitly relate the class number of K with the product of the class numbers of the three quadratic subfields. Received: 25 July 2000 / Revised version: 12 December 2000     

The Sato–Tate distribution in families of elliptic curves with a rational parameter of bounded height

We obtain new results concerning the Sato–Tate conjecture on the distribution of Frobenius angles over parametric families of elliptic curves with a rational parameter of bounded height.     

Extremal partition and estimates for the coefficients in the class σ(r)

Let be the known class of functions f(z)=z+₀+₁z^–1+..., that are meromorphic and univalent in the region U^*={z ¦z¦ < 1}, and let (r) be the class of functions of for which f(U^*) does not contain a singly connected domain D_f, 0 D_f, with conformal radius r with respect to the coordinate origin, 0 < r < 1. Sharp inequalities are obtained for certain functionals, and sharp bounds are obtained for ¦ ₁ ¦ and ¦ ₂ ¦ in the class (r). The proof illustrates the possibility of using results with a symmetrization character in problems on extremal partition of a Riemannian sphere to obtain sharp bounds for coefficients in the classes and (r).Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 196, pp. 101–116, 1991.     

On the growth and range of functions in Möbius invariant spaces

This paper is a continuation of our earlier work and focuses on the structural and geometric properties of functions in analytic Besov spaces, primarily on univalent functions in such spaces and their image domains. We improve several earlier results.     

The Deligne–Mumford compactification of the real multiplication locus and Teichmüller curves in genus 3

In the moduli space M \mathcal{M} _g of genus-g Riemann surfaces, consider the locus RM_O \mathcal{R}{\mathcal{M}_{\mathcal{O}}} of Riemann surfaces whose Jacobians have real multiplication by the order O \mathcal{O} in a totally real number field F of degree g. If g = 3, we compute the closure of RM_O \mathcal{R}{\mathcal{M}_{\mathcal{O}}} in the Deligne–Mumford compactification of M \mathcal{M} _g and the closure of the locus of eigenforms over RM_O \mathcal{R}{\mathcal{M}_{\mathcal{O}}} in the Deligne–Mumford compactification of the moduli space of holomorphic 1-forms. For higher genera, we give strong necessary conditions for a stable curve to be in the boundary of RM_O \mathcal{R}{\mathcal{M}_{\mathcal{O}}} . Boundary strata of RM_O \mathcal{R}{\mathcal{M}_{\mathcal{O}}} are parameterized by configurations of elements of the field F satisfying a strong geometry of numbers type restriction.     

An analogue of the Dedekind–Rademacher sum and certain ray class invariants of real quadratic fields

In this paper, we consider a certain product of double sine functions as an analogue of the Dedekind–Rademacher sum. Its reciprocity formulas are established by decomposition of a certain double zeta function. As their applications, we reconstruct and refine a part of Arakawa?s work on ray class invariants of real quadratic fields, and prove directly explicit relations between various invariants which are defined in terms of the double sine function and are related to the Stark–Shintani conjecture. Moreover, in some examples, new expressions of the invariants are revealed. As two appendices, we give a new proof of Carlitz?s three-term relation for the Dedekind–Rademacher sum and a simple proof of Arakawa?s transformation formula for an analogue of the generalized Eisenstein series originated with Lewittes.     

The generalized Laguerre inequalities and functions in the Laguerre-Pólya class

The principal goal of this paper is to show that the various sufficient conditions for a real entire function, φ(x), to belong to the Laguerre-Pólya class (Definition 1.1), expressed in terms of Laguerre-type inequalities, do not require the a priori assumptions about the order and type of φ(x). The proof of the main theorem (Theorem 2.3) involving the generalized real Laguerre inequalities, is based on a beautiful geometric result, the Borel-Carathédodory Inequality (Theorem 2.1), and on a deep theorem of Lindelöf (Theorem 2.2). In case of the complex Laguerre inequalities (Theorem 3.2), the proof is sketched for it requires a slightly more delicate analysis. Section 3 concludes with some other cognate results, an open problem and a conjecture which is based on Cardon’s recent, ingenious extension of the Laguerre-type inequalities.     

Benford’s law and distribution functions of sequences in (0, 1)

Applying the theory of distribution functions of sequences x _n ∈ [0, 1], n = 1, 2, ..., we find a functional equation for distribution functions of a sequence x _n and show that the satisfaction of this functional equation for a sequence x _n is equivalent to the fact that the sequence x _n to satisfies the strong Benford law. Examples of distribution functions of sequences satisfying the functional equation are given with an application to the strong Benford law in different bases. Several direct consequences from uniform distribution theory are shown for the strong Benford law.     

On the order of approximation to functions ofH p (R) (0<p≦1) by certain means of Fourier integrals

H ^P (R ₊ ² ) — R ₊ ² ={zC: Imz>0} ^p (R) — H ^p (R ₊ ² ). P ^k (f,x) — ë- — ,W ^k (f,x) — — R ^k, (f,x) — f H (R) (. §1,1)–3)); _k (, f) _p — - . , fH ^p (R) 0<p1,kN; (1+)^–1<p1, 0<<,kN.     

The growth of solutions of f″+ e-zf′+ Q(z)f - 0 where the order (Q)＝ I

This paper investigates the growth of solutions of the equation f" + e-zf′ + Q(z)f＝ 0 wherethe order (Q)＝ 1. When Q(z) ＝ h(z)ebz, h(z) is nonzero polynomial, b ≠ -1 is a complex constant, every solution of the above equation has infinite order and the hyper-order 1. We improve the results of M. Frei, M.Ozawa, G. Gundersen and J. K. Langley.     

The Equation f′′′?+?ff′′?+?g(f′)?=?0 and the Associated Boundary Value Problems

We study the concave and convex solutions of the third order similarity differential equation f′′′?+?ff′′?+?g(f′)?=?0, and especially the ones that satisfies the boundary conditions f(0)?=?a, f′(0)?=?b and f′(t) → λ as t →?+?∞, where λ is a root of the function g. According to the sign of g between b and λ, we obtain results about existence, uniqueness and boundedness of solutions to this boundary value problem, that we denote by ${({\mathcal P}_{{\bf g};a,b,\lambda})}$ . In this way, we pursue and complete the study done in 2008.     

The method of two-time Green’s functions in the magnetism theory of metals with strong correlations

We apply the Bogoliubov-Tyablikov method of two-time Green’s functions to a multielectron theory of metals in the framework of the models with strong correlations, which are the Hubbard model and the Vonsovskii s-d(f) exchange model. We discuss the atomic representation in the problem of describing electron states, the metal-insulator transition, the problem of noncoherent states, and the Kondo effect. We analyze the ferromagnetism criterion in systems of strongly correlated electrons, which differs drastically from the Stoner condition.