On the error term $$\Delta _{(k,l)}(x)$$ Δ ( k,l ) ( x )

The Ramanujan Journal - Let k, l be non-negative integers and $$\zeta ^{(k)}(s)$$ denote the kth derivative of the Riemann zeta function $$\zeta (s).$$ Further let $$d_{(k,l)}(n)$$ be the nth...     

On congruence properties of the restricted partition functions $$p_{\omega }(n,k)$$ p ω ( n,k ) and $$p_{\nu }(n,k)$$ p ν ( n,k )

The Ramanujan Journal - In a recent work by Andrews, Dixit, and Yee the partition functions $$p_{\omega }(n)$$ and $$p_{\nu }(n)$$ were introduced in connection with the third order mock theta...     

Flag-transitive 2- $$(v,k,\lambda )$$ ( v,k , λ ) designs with $$r>\lambda (k-3)$$ r > λ ( k - 3 )

Designs, Codes and Cryptography - In this paper, we study the flag-transitive automorphism groups of 2-designs and prove that if G is a flag-transitive automorphism group of a 2-design $$\mathcal...     

Tropical Duality in $$(d+2)$$ ( d + 2 ) -Angulated Categories

Applied Categorical Structures - Let $$\mathscr {C}$$ be a 2-Calabi–Yau triangulated category with two cluster tilting subcategories $$\mathscr {T}$$ and $$\mathscr {U}$$ . A result from...     

Dynamics of kink-soliton solutions of the $$(2+1)$$ -dimensional sine-Gordon equation

Theoretical and Mathematical Physics - We study the dynamics of explicit solutions of the $$(2+1)$$ -dimensional (2D) sine-Gordon equation. The Darboux transformation is applied to the associated...     

The projective general linear group $${\mathrm {PGL}}(2,2^m)$$ PGL ( 2 , 2 m ) and linear codes of length $$2^m+1$$ 2 m + 1

Designs, Codes and Cryptography - Let $$q=2^m$$ . The projective general linear group $${\mathrm {PGL}}(2,q)$$ acts as a 3-transitive permutation group on the set of points of the projective line....     

Boundary Properties of First-Order Partial Derivatives of the Poisson Integral for the Half-Space $$\mathbb{R}_{k + 1}^ + (k >1)$$

Boundary properties of first-order partial derivatives of the Poisson integral are studied in the half-space .     

On a family of diophantine triples {k, A 2 k + 2A, (A + 1)2 k + 2 (A + 1)} with two parameters

Let A and k be positive integers. We study the Diophantine quadruples $$ \{ k,A^2 k + 2A,(A + 1)^2 k + 2(A + 1),d\} $$ . We prove that if d is a positive integer such that the product of any two distinct elements of the set increased by 1 is a perfect square, then $$ \begin{gathered} d = (4A^4 + 8A^3 + 4A^2 )k^3 + (16A^3 + 24A^2 + 8A)k^2 \hfill \\ + (20A^2 + 20A + 4)k + (8A + 4) \hfill \\ \end{gathered} $$ when 3 ≦ A ≦ 10. This extends a theorem obtained by Dujella [7] for A = 1, and also, a classical theorem of Baker and Davenport [2] for A = k = 1.     

$$\bar\partial$$ -dressing method for a few $$(2+1)$$ -dimensional integrable coupling systems

Theoretical and Mathematical Physics - Several $$(2+1)$$ -dimensional integrable coupling systems are derived from two sets of auxiliary linear problems, including the integrable coupling system of...     

Packing chromatic number, $$\mathbf (1, 1, 2, 2) $$ ( 1 , 1 , 2 , 2 ) -colorings,and characterizing the Petersen graph

The packing chromatic number $$\chi _{\rho }(G)$$     

Application of the $$\bar\partial$$ -dressing method to a $$(2+1)$$ -dimensional equation

Theoretical and Mathematical Physics - A remarkable method for investigating solutions of nonlinear soliton equation is the $$\bar\partial$$ -dressing method. Although there are other methods that...     

On $$(\ell,m)$$-regular partitions with distinct parts

Let \(a_{\ell ,m}(n)\) denote the number of \((\ell ,m)\)-regular partitions of a positive integer n into distinct parts, where \(\ell \) and m are relatively primes. In this paper, we establish several infinite families of congruences modulo 2 for \(a_{3,5}(n)\). For example,

$$\begin{aligned} a_{3, 5}\left(2^{6\alpha +4}5^{2\beta }n+\frac{ 2^{6\alpha +3}5^{2\beta +1}-1}{3}\right) \equiv 0 , \end{aligned}$$

where \(\alpha , \beta \ge 0\).

     

Functions generating (m,M, $$\varvec{\Psi }$$ )-Schur-convex sums

Aequationes mathematicae - The notion of $$(m,M,\Psi )$$ -Schur-convexity is introduced and functions generating $$(m,M,\Psi )$$ -Schur-convex sums are investigated. An extension of the...     

Representations of $$\zeta (2n + 1)$$ and Related Numbers in the Form of Definite Integrals and Rapidly Convergent Series

Doklady Mathematics - Let $$\zeta (s)$$ and $$\beta (s)$$ be the Riemann zeta function and the Dirichlet beta function. The formulas for calculating the values of $$\zeta (2m)$$ and $$\beta (2m -...     

Recognition by spectrum of the groups $$ ^2 D_{2^m + 1} (3) $$

Abstract It is proved that a finite group with the same set of element orders as the simple group is isomorphic to . This work was supported by Russian Foundation for Basic Research (Grant No. 07-01-00148), RFBR-BRFBR (Grant No. 08-01-90006) and RFBR-GFEN (Grant No. 08-01-92200)     

Counter-examples to the Dunford–Schwartz pointwise ergodic theorem on $$\varvec{L^1+L^\infty }$$ L 1 + L ∞

Extending a result by Chilin and Litvinov, we show by construction that given any $$\sigma $$ -finite infinite measure space $$(\Omega ,\mathcal {A}, \mu )$$ and a function $$f\in L^1(\Omega )+L^\infty (\Omega )$$ with $$\mu (\{|f|>\varepsilon \})=\infty $$ for some $$\varepsilon >0$$ , there exists a Dunford–Schwartz operator T over $$(\Omega ,\mathcal {A}, \mu )$$ such that $$\frac{1}{N}\sum _{n=1}^N (T^nf)(x)$$ fails to converge for almost every $$x\in \Omega $$ . In addition, for each operator we construct, the set of functions for which pointwise convergence fails almost everywhere is residual in $$L^1(\Omega )+L^\infty (\Omega )$$ .     

A New Proof of a Result Concerning a Complete Description of $$ (n,n + 2) $$ -Graphs with Maximum Value of the Hosoya Index

Mathematical Notes - The Hosoya index is an important topological index of graphs defined as the number of their matchings. At present, for any $$ n $$ and $$ k \in \{- 1,0,1,2 \}$$ , all connected...     

A Fast Computation of the Best $${k}$$ -Digit Rational Approximation to a Real Number

Mediterranean Journal of Mathematics - Given a real number $${\alpha}$$ , we aim at computing the best rational approximation with at most $${k}$$ digits and with exactly $${k}$$ digits at the...     

Solvability and Blow-Up of Weak Solutions of Cauchy Problems for $$(3+1)$$ -Dimensional Equations of Drift Waves in a Plasma

Mathematical Notes - In this paper, two Cauchy problems that contain different nonlinearities $$|u|^q$$ and $$(\partial/\partial t)|u|^q$$ are studied. The differential operator in these problems...     

On the rational (K + 1,K + 1)-type difference equation

In this paper we investigate the boundedness character of the positive solutions of the rational difference equation of the form $$x_{n + 1} = \frac{{a_0 + \sum\nolimits_{j = 1}^k {a_j x_{n - j + 1} } }}{{b_0 + \sum\nolimits_{j = 1}^k {b_j x_{n - j + 1} } }}, n = 0,1,...$$ where k ε N, andaj,bj, j = 0,1,…, k, are nonnegative numbers such thatb ₀+∑ _j=1 ^k b _j x _n-j+1>0 for everyn ∈N ∪{0}. In passing we confirm several conjectures recently posed in the paper: E. Camouzis, G. Ladas and E. P. Quinn, On third order rational difference equations (part 6).