The problem of uniqueness of an entire or a meromorphic function when it shares a value or a small function with its derivative became popular among the researchers after the work of Rubel and Yang (1977). Several authors extended the problem to higher order derivatives. Since a linear differential polynomial is a natural extension of a derivative, in the paper we study the uniqueness of a meromorphic function that shares one small function CM with a linear differential polynomial, and...

It is well known that the Taylor series of every function in the Fock space $F_{\alpha }^p$ converges in norm when 1 < p < ∞. It is also known that this is no longer true when p = 1. In this note we consider the case 0 < p < 1 and show that the Taylor series of functions in $F_{\alpha }^p$ do not necessarily converge “in norm”.

Let $\varphi$ be an entire self-map of ${ℂ}^N$, $u_0$ be an entire function on ${ℂ}^N$ and $𝐮=(u_1,\cdots ,u_N)$ be a vector-valued entire function on ${ℂ}^N$. We extend the Stević-Sharma type operator to the classcial Fock spaces, by defining an operator $T_{u_0,𝐮,\varphi }$ as follows: $$-.4pt{T}_{u_0,𝐮,\varphi }f=u_0·f\circ \varphi +\sum _{i=1}^N{u}_i·\frac{\partial f}{\partial z_i}\circ \varphi .$$ We investigate the boundedness and compactness of $T_{u_0,𝐮,\varphi }$ on Fock spaces. The complex symmetry and self-adjointness of $T_{u_0,𝐮,\varphi }$ are also characterized.

Let $P\left(z\right)$ be a polynomial of degree $n$ having no zeros in $\left|z\right|<k$, $k\le 1$, and let $Q\left(z\right):=z^n\overline{P(1/\overline{z})}$. It was shown by Govil that if ${max}_{\left|z\right|=1}\left|P^{\text{'}}\left(z\right)\right|$ and ${max}_{\left|z\right|=1}\left|Q^{\text{'}}\left(z\right)\right|$ are attained at the same point of the unit circle $\left|z\right|=1$, then $$\underset{\left|z\right|=1}{max}|P^{\text{'}}\left(z\right)|\le \frac{n}{1+k^n}\underset{\left|z\right|=1}{max}\left|P\left(z\right)\right|.$$ The main result of the present article is a generalization of Govil’s polynomial inequality to a class of entire functions of exponential type.

In this note, we prove that there is no transcendental entire function $f\left(z\right)\in \mathbb{Q}\left[\right[z\left]\right]$ such that $f\left(\mathbb{Q}\right)\subseteq \mathbb{Q}$ and $\mathrm{den}f(p/q)=F\left(q\right)$, for all sufficiently large $q$, where $F\left(z\right)\in \mathbb{Z}\left[z\right]$.

Let $k$ be a nonnegative integer or infinity. For $a\in ℂ\cup \left\{\infty \right\}$ we denote by $E_k(a;f)$ the set of all $a$-points of $f$ where an $a$-point of multiplicity $m$ is counted $m$ times if $m\le k$ and $k+1$ times if $m>k$. If $E_k(a;f)=E_k(a;g)$ then we say that $f$ and $g$ share the value $a$ with weight $k$. Using this idea of sharing values we study the uniqueness of meromorphic functions whose certain nonlinear differential polynomials share a nonzero polynomial with finite weight. The results of the paper improve and generalize the related results due to...

The main objective of this paper is to give the specific forms of the meromorphic solutions of the nonlinear difference-differential equation $$f^n\left(z\right)+P_d(z,f)=p_1\left(z\right){\mathrm{e}}^{{\alpha }_1\left(z\right)}+p_2\left(z\right){\mathrm{e}}^{{\alpha }_2\left(z\right)},$$ where $P_d(z,f)$ is a difference-differential polynomial in $f\left(z\right)$ of degree $d\le n-1$ with small functions of $f\left(z\right)$ as its coefficients, $p_1$, $p_2$ are nonzero rational functions and ${\alpha }_1$, ${\alpha }_2$ are non-constant polynomials. More precisely, we find out the conditions for ensuring the existence of meromorphic solutions of the above equation.

Firstly we study the growth of meromorphic solutions of linear difference equation of the form$$A_k\left(z\right)f(z+c_k)+\cdots +A_1\left(z\right)f(z+c_1)+A_0\left(z\right)f\left(z\right)=F\left(z\right),$$ where $A_k\left(z\right),...,A_0\left(z\right)$ and $F\left(z\right)$ are meromorphic functions of finite logarithmic order, $c_i$ $(i=1,...,k,k\in \mathbb{N})$ are distinct nonzero complex constants. Secondly, we deal with the growth of solutions of differential-difference equation of the form $$\sum _{i=0}^n\sum _{j=0}^m{A}_{ij}\left(z\right)f^{\left(j\right)}(z+c_i)=F\left(z\right),$$ where $A_{ij}\left(z\right)$ $(i=0,1,...,n,j=0,1,...,m,n,m\in \mathbb{N})$ and $F\left(z\right)$ are meromorphic functions of finite logarithmic order, $c_i$ $(i=0,...,n)$ are distinct complex constants. We extend some previous results...

We investigate the exponent of convergence of the zero-sequence of solutions of the differential equation $f^{\left(k\right)}+a_{k-1}\left(z\right)f^{(k-1)}+\cdots +a₁\left(z\right)f^{\text{'}}+D\left(z\right)f=0$, (1) where $D\left(z\right)=Q₁\left(z\right)e^{P₁\left(z\right)}+Q₂\left(z\right)e^{P₂\left(z\right)}+Q₃\left(z\right)e^{P₃\left(z\right)}$, P₁(z),P₂(z),P₃(z) are polynomials of degree n ≥ 1, Q₁(z),Q₂(z),Q₃(z),$a_j\left(z\right)$ (j=1,..., k-1) are entire functions of order less than n, and k ≥ 2.

We prove the existence of sequences ${\varrho ₙ}_{n=1}^{\infty }$, ϱₙ → 0⁺, and ${zₙ}_{n=1}^{\infty }$, |zₙ| = 1/2, such that for every α ∈ ℝ and for every meromorphic function G(z) on ℂ, there exists a meromorphic function $F\left(z\right)=F_{G,\alpha }\left(z\right)$ on ℂ such that $\varrho {ₙ}^{\alpha }F(nzₙ+n\varrho ₙ\zeta )$ converges to G(ζ) uniformly on compact subsets of ℂ in the spherical metric. As a result, we construct a family of functions meromorphic on the unit disk that is $Q_m$-normal for no m ≥ 1 and on which an extension of Zalcman’s Lemma holds.

We investigate the uniqueness problem of entire functions that share two polynomials with their $k$th derivatives and obtain some results which improve and generalize the recent result due to Lü and Yi (2011). Also, we exhibit some examples to show that the conditions of our results are the best possible.

We obtain the basic analytic properties, i.e. meromorphic continuation, polar structure and bounds for the order of growth, of all the nonlinear twists with exponents $\le 1/d$ of the $L$-functions of any degree $d\ge 1$ in the extended Selberg class. In particular, this solves the resonance problem in all such cases.

With the idea of normal family we study the uniqueness of meromorphic functions $f$ and $g$ when $f^n{\left(f^{\left(k\right)}\right)}^m-p$ and $g^n{\left(g^{\left(k\right)}\right)}^m-p$ share two values, where $p$ is any nonzero polynomial. The result of this paper significantly improves and generalizes the result due to A. Banerjee and S. Majumder (2018).

Let $X$ and $Y$ be compact Kähler manifolds, and let $f:X\to Y$ be a dominant meromorphic map. Based upon a regularization theorem of Dinh and Sibony for DSH currents, we define a pullback operator $f^{♯}$ for currents of bidegrees $(p,p)$ of finite order on $Y$ (and thus forcurrent, since $Y$ is compact). This operator has good properties as may be expected. Our definition and results are compatible to those of various previous works of Meo, Russakovskii and Shiffman, Alessandrini and Bassanelli, Dinh and Sibony,...

Let f be a transcendental meromorphic function and $g\left(z\right)=f(z+c₁)+\cdots +f(z+c_k)-kf\left(z\right)$ and $g_k\left(z\right)=f(z+c₁)\cdots f(z+c_k)-f^k\left(z\right)$. A number of results are obtained concerning the exponents of convergence of the zeros of g(z), $g_k\left(z\right)$, g(z)/f(z), and $g_k\left(z\right)/f^k\left(z\right)$.

Let $F$ be a class of entire functions represented by Dirichlet series with complex frequencies $\sum a_k{\mathrm{e}}^{\langle {\lambda }^k,z\rangle }$ for which $\left(\right|{\lambda }^k{|/\mathrm{e})}^{|{\lambda }^k|}k!\left|a_k\right|$ is bounded. Then $F$ is proved to be a commutative Banach algebra with identity and it fails to become a division algebra. $F$ is also proved to be a total set. Conditions for the existence of inverse, topological zero divisor and continuous linear functional for any element belonging to $F$ have also been established.

In the present paper the author discusses certain multiple integrals $I(u)$ of the calculus of variations satisfying convexity conditions, and no growth property, and the corresponding Serrin integrals $\Im (u)$, to which the existence theorems in [3,4,5] do not apply. However, in the present paper, the integrals $I(u)$ and $\Im (u)$ are reduced to simpler form $H(v)$ and $\mathscr{H}(v)$ to which the existence theorems above apply. Thus, we derive that $I(u)\le \Im (u)$, $H(v)\le \mathscr{H}(v)$, we obtain the existence of the absolute minimum for the Serrin forms $\Im (u)$...