Per l'equazione differenziale ordinaria non lineare del 3° ordine indicata nel titolo, studiata da numerosi autori sotto l'ipotesi $h(x)\text{sgn}x\ge 0$ $for|x|>R$, si dimostra l'esistenza di almeno una soluzione limitata sopprimendo l'ipotesi suddetta.

We study the existence of positive solutions to the fourth-order two-point boundary value problem $$\left\{\begin{array}{cc}{u}^{\text{'}\text{'}\text{'}\text{'}}\left(t\right)+f(t,u\left(t\right))=0,\hfill & 0<t<1,\hfill \\ u^{\text{'}}\left(0\right)=u^{\text{'}}\left(1\right)=u^{\text{'}\text{'}}\left(0\right)=0,\hfill & u\left(0\right)=\alpha \left[u\right],\hfill \end{array}\right.$$ where $\alpha \left[u\right]={\int }_0^{1}u\left(t\right)\mathrm{d}A\left(t\right)$ is a Riemann-Stieltjes integral with $A\ge 0$ being a nondecreasing function of bounded variation and $f\in 𝒞([0,1]\times {ℝ}_{+},{ℝ}_{+})$. The sufficient conditions obtained are new and easy to apply. Their approach is based on Krasnoselskii’s fixed point theorem and the Avery-Peterson fixed point theorem.

Si dimostra un teorema di esistenza di soluzioni periodiche dell'equazione differenziale ordinaria del terzo ordine $x^{\mathrm{\prime \prime \prime }}+a(t,x,x^{\prime },x^{\mathrm{\prime \prime }})x^{\mathrm{\prime \prime }}+b(t,x,x^{\prime },x^{\mathrm{\prime \prime }})x^{\prime }+h(x)=e(t,x,x^{\prime },x^{\mathrm{\prime \prime }})$ con le funzioni $a$, $b$, $e$ periodiche in $t$ di periodo $\omega$.

We obtain estimates for the average value of the largest prime factor P(n) in short intervals [x,x+y] and of h(P(n)+1), where h is a complex-valued additive function or multiplicative function satisfying certain conditions. Letting $s_q\left(n\right)$ stand for the sum of the digits of n in base q ≥ 2, we show that if α is an irrational number, then the sequence ${\left(\alpha s_q\left(P\left(n\right)\right)\right)}_{n\in \mathbb{N}}$ is uniformly distributed modulo 1.

Per l'equazione differenziale ordinaria non lineare del 3° ordine indicata nel titolo, studiata da numerosi autori sotto l'ipotesi $h(x)\text{sgn}x\ge 0$ $for|x|>R$, si dimostra l'esistenza di almeno una soluzione limitata sopprimendo l'ipotesi suddetta.

Si dimostra un teorema di esistenza di soluzioni periodiche dell'equazione differenziale ordinaria del terzo ordine $x^{\mathrm{\prime \prime \prime }}+a(t,x,x^{\prime },x^{\mathrm{\prime \prime }})x^{\mathrm{\prime \prime }}+b(t,x,x^{\prime },x^{\mathrm{\prime \prime }})x^{\prime }+h(x)=e(t,x,x^{\prime },x^{\mathrm{\prime \prime }})$ con le funzioni $a$, $b$, $e$ periodiche in $t$ di periodo $\omega$.

We show that if p ≠ 5 is a prime, then the numbers $1/p\left(\genfrac{}{}{0pt}{}{p}{m₁,...,m_t}\right)|t\ge 1,m_i\ge 0fori=1,...,tand{\sum }_{i=1}^t{m}_i=p$ cover all the nonzero residue classes modulo p.

We study the existence and uniqueness of a positive solution to the problem $$u^{\text{'}\text{'}}=p\left(t\right)u+q(t,u)u+f\left(t\right);u\left(0\right)=u\left(\omega \right),u^{\text{'}}\left(0\right)=u^{\text{'}}\left(\omega \right)$$ with a super-linear nonlinearity and a nontrivial forcing term $f$. To prove our main results, we combine maximum and anti-maximum principles together with the lower/upper functions method. We also show a possible physical motivation for the study of such a kind of periodic problems and we compare the results obtained with the facts well known for the corresponding autonomous case.

For a double complex $(A,d^{\text{'}},d^{\text{'}\text{'}})$, we show that if it satisfies the $d^{\text{'}}{d}^{\text{'}\text{'}}$-lemma and the spectral sequence $\left\{E_r^{p,q}\right\}$ induced by $A$ does not degenerate at $E_0$, then it degenerates at $E_1$. We apply this result to prove the degeneration at $E_1$ of a Hodge-de Rham spectral sequence on compact bi-generalized Hermitian manifolds that satisfy a version of $d^{\text{'}}{d}^{\text{'}\text{'}}$-lemma.

A classical theorem of M. Fried [2] asserts that if non-zero integers $\beta ₁,...,{\beta }_l$ have the property that for each prime number p there exists a quadratic residue ${\beta }_j$ mod p then a certain product of an odd number of them is a square. We provide generalizations for power residues of degree n in two cases: 1) n is a prime, 2) n is a power of an odd prime. The proofs involve some combinatorial properties of finite Abelian groups and arithmetic results of [3].

We consider certain class of second order nonlinear nonautonomous delay differential equations of the form $$a\left(t\right)x^{\text{'}\text{'}}+b\left(t\right)g(x,x^{\text{'}})+c\left(t\right)h\left(x(t-r)\right)m\left(x^{\text{'}}\right)=p(t,x,x^{\text{'}})$$ and $${\left(a\left(t\right)x^{\text{'}}\right)}^{\text{'}}+b\left(t\right)g(x,x^{\text{'}})+c\left(t\right)h\left(x(t-r)\right)m\left(x^{\text{'}}\right)=p(t,x,x^{\text{'}}),$$ where $a$, $b$, $c$, $g$, $h$, $m$ and $p$ are real valued functions which depend at most on the arguments displayed explicitly and $r$ is a positive constant. Different forms of the integral inequality method were used to investigate the boundedness of all solutions and their derivatives. Here, we do not require construction of the Lyapunov-Krasovski functional to establish our results....

For μ ∈ ℂ such that Re μ > 0 let ${ℱ}_{\mu }$ denote the class of all non-vanishing analytic functions f in the unit disk with f(0) = 1 and $Re(2\pi /\mu z{f}^{\text{'}}\left(z\right)/f\left(z\right)+(1+z)/(1-z))>0$ in . For any fixed z₀ in the unit disk, a ∈ ℂ with |a| ≤ 1 and λ ∈ ̅, we shall determine the region of variability V(z₀,λ) for log f(z₀) when f ranges over the class ${ℱ}_{\mu }\left(\lambda \right)=f\in {ℱ}_{\mu }:f^{\text{'}}\left(0\right)=(\mu /\pi )(\lambda -1)and{f}^{\text{'}\text{'}}\left(0\right)=(\mu /\pi )\left(a\right(1-\left|\lambda \right|²)+(\mu /\pi )(\lambda -1)²-(1-\lambda ²))$. In the final section we graphically illustrate the region of variability for several sets of parameters.

Viene dimostrata l'esistenza di soluzioni del problema di Darboux per l'equazione iperbolica $z_{xy}^{\mathrm{\prime \prime }}=f(x,y,z,Z_x^{\prime },z_y)$ sul planiquarto $x\ge 0$, $y\ge 0$. Qui, $f$ è una funzione continua, con valori in uno spazio Banach che soddisfano alcune condizioni di regolarità espresse in termini della misura di non-compattezza $\alpha$.

We are interested whether there is a nonnegative integer $u_0$ and an infinite sequence of digits $u_1,u_2,u_3,\cdots$ in base $b$ such that the numbers $u_0{b}^n+u_1{b}^{n-1}+\cdots +u_{n-1}b+u_n,$ where $n=0,1,2,\cdots ,$ are all prime or at least do not have prime divisors in a finite set of prime numbers $S.$ If any such sequence contains infinitely many elements divisible by at least one prime number $p\in S,$ then we call the set $S$ unavoidable with respect to $b$. It was proved earlier that unavoidable sets in base $b$ exist if $b\in \{2,3,4,6\},$ and that no unavoidable set exists in base $b=5.$ Now,...

We consider the boundary value problem $$\begin{array}{c}{u}^{\text{'}\text{'}\text{'}}\left(t\right)=f(t,u\left(t\right),u^{\text{'}}\left(t\right),u^{\text{'}\text{'}}\left(t\right)),0<t<1,\\ u\left(0\right)=u^{\text{'}}\left(0\right)=0,u\left(1\right)={\int }_0^{1}g\left(s\right)u\left(s\right)\mathrm{d}s,\end{array}$$ where $f:[0,1]\times {ℝ}^3\to {ℝ}^{+}$, $g:[0,1]\to {ℝ}^{+}$ are continuous functions. The case when $f=f\left(u\right(t\left)\right)$ was studied in 2018 by Guendouz et al. Using the fixed-point theory on cones they established the existence of positive solutions. Here, by the method developed by ourselves very recently, we establish the existence, uniqueness and positivity of the solution under easily verified conditions and propose an iterative method for finding the solution. Some examples demonstrate the validity of the...