**0**

votes

**0**answers

2 views

### Functions of form $f(z)/f(z^*)$

I am doing my research in mathematical physics, and in the process I am getting functions of complex variable $z$ of form
$F(z) = \frac{f(z)}{f(z^*)}$
In my case $f$ doesn't have any interesting ...

**4**

votes

**0**answers

55 views

### Complex Stone-Weierstrass Type problem

I have come across this problem which resembles complex Stone-Weierstrass theorem except for a problem that the conjugate of the functions are not necessarily in the sub algebra.
Suppose $\Omega$ is ...

**2**

votes

**1**answer

105 views

### The spectrum and the tangent space of the algebra of holomorphic functions on a Stein manifold

Let $A$ be a Fréchet algebra over ${\mathbb C}$, and let us call the spectrum ${\tt Spec}[A]$ of $A$ the set of all characters, i.e. continuous multiplicative linear functionals $s:A\to{\mathbb C}$, ...

**1**

vote

**0**answers

31 views

### Product of associated Legendre Functions with Large order

I have problems in determining the behaviour of $\vert f(z) \vert$ for $\vert z \vert \rightarrow\infty$, $\Re(z)\geq 0$, where
$$f(z):=P^{-z}_{\nu}(\cosh(\alpha))\cdot Q^{z}_{\nu}(\cosh(\beta))\cdot ...

**8**

votes

**3**answers

479 views

### Can the topological algebra of analytic functions be endowed with a norm that defines the natural topology?

Right, so in my research in complex analysis I was puzzled by this question which may have a simple approachable answer that eludes me, but I am truly itching to find out and in need of it so I am ...

**1**

vote

**0**answers

34 views

### explicit conformal map of sinus-shaped region

I wonder weather an explicit conformal map of a sinus-shaped region given by $\Re(z) \in [0, 1+\delta \sin(\Im(z)) ]$ onto say a strip or a ball is known (of course $0<\delta < 1$). Thank you.

**2**

votes

**1**answer

82 views

### On some curves of real values of a rational function

For given parameters $a_{1},\dots,a_{k}\in\mathbb{R}$, define the rational function $\phi:\mathbb{C}\to\mathbb{C}$ as
$$\phi(z)=\frac{1}{z}-a_{1}z-a_{2}z^{2}-\dots-a_{k}z^{k}.$$
The domain of its real ...

**2**

votes

**2**answers

86 views

### Analytic continuation of a specific integral with respect to a parameter

The following integral absolutely converges for $Re(z)<0$ and is analytic in this domain:
$$F(z):=\int_{0}^{+\infty}\frac{\sin r}{r}e^{\sqrt{r^2+m^2}z}dr ,$$
where $m>0$ is fixed.
Question. To ...

**0**

votes

**0**answers

101 views

### Contour integral of non holomorphic but continuous functions [closed]

Let us consider two functions $f(z)$ and $g(z)$, both holomorphic on a domain $U$ (a simply connected subset of $\mathbb{C}$).
Thus, because of Cauchy's integral theorem, along any closed rectifiable ...

**0**

votes

**1**answer

104 views

### adjoint of the operator rotation [closed]

I need to calculate the adjoint of the operator
$T_{a}=a i(x\frac{\partial}{\partial y}- y\frac{\partial}{\partial x})$ with $i^{2}=-1, \quad a\in \mathbb{C}$ and domain
$D=\{\varphi\in L^{2}(R), ...

**1**

vote

**0**answers

73 views

### Poincaré inequality for holomorphic line bundles

Let $M$ be a Riemann surface of genus >1, $g$ be an Hermitian metric on $M$. Let $E$ is a holomorphic negative line bundle over $M$, for example, the holomorhic tangent bundle of $M$. Let $h$ be an ...

**2**

votes

**0**answers

36 views

### Estimates for hyperbolic metrics on nested surfaces

Suppose that $X$ and $Y$ are connected hyperbolic Riemann surfaces, with $X\subsetneq Y$. Let $\rho_{X,Y}$ be the density of the hyperbolic metric of $X$ with respect to that of $Y$; then $\rho_{X,Y} ...

**4**

votes

**1**answer

257 views

### Two similar integrals

Let $n$ be a given even positive integer. We have the following integral
\begin{align}
...

**1**

vote

**1**answer

53 views

### Can I apply Lagrange inversion theorem? [closed]

I want to invert the equation
$$\eta = g(x)\sqrt{1+g'(x)^2}$$
to get $x$ as a function of $\eta$. Assume $g(0)=0$, $g'(0)=0$ and $g'(x)>0$ for $x>0$ (Think $g(x) = x^p$ for $p\geq 2$ integer).
...

**1**

vote

**0**answers

48 views

### Complex integration over 1-singular chain

Let $f$ be a continuous function on $\mathbb{C}$ and assume that $\lim_{z\to \infty} zf(z) = \lambda.$ Let us note for all natural $n$ $$C_n = \{z \in \mathbb{C} : |z|=n\}.$$ Then, a usual fact of ...

**1**

vote

**1**answer

149 views

### find solution of complex number recurrence equation

I have the following recurrence equation:
$$(\mu\ n + \nu) f_{n} + J\Phi^{*} \sqrt{n+1}f_{n+1} + J\Phi\ \sqrt{n}f_{n-1} = 0$$
for complex numbers $f_{n}$ where $n = 0,1,2,3,...,\infty$ and complex ...

**0**

votes

**0**answers

31 views

### Normality criterion based on Brownian motion

Consider analytic family $\mathcal{F}$ btw domains $U,V\subset \mathbb{C}$. For any $f\in \mathcal{F}$ we have time-changed Brownian motion $f(B_{t})=\widetilde{B}_{\int_{0}^{t}|f(B_{s})|^{2}ds}$. So ...

**2**

votes

**1**answer

129 views

### Proof of Euler's reflection formula via rapidly decreasing Fourier series

Story
I want to prove Euler's reflection formula by showing that
\begin{equation*}
f(s) = \sin(\pi s) \Gamma(s) \Gamma(1 - s)
\end{equation*}
is constant, where $s = \sigma + it$. It's easy to see ...

**0**

votes

**0**answers

41 views

### How to get Wiener-Hopf decomposition of this matrix function

I met a matrix function $M(z)$ that I need to get its Wiener-Hopf decomposition that $M(z) = M_+(z) M_-(z)$ with $M_+(z)$ and $M_-(z)$ being analytic inside and outside the unit circle respectively. ...

**-1**

votes

**0**answers

34 views

### How to prove that arc segment vanishes

I have this integral:
$$iNx^a\int_{-\frac{\pi}{2}}^{\frac{\pi}{2}} \frac{x^{Ne^{i\theta}}e^{i\theta}}{\Gamma(Ne^{i\theta}+a-m)\zeta(2Ne^{i\theta}+2a+n)\sin (\pi \left(a+Ne^{i\theta}\right))} ...

**1**

vote

**2**answers

77 views

### Nonlinear PDE for a 2D foliation

I am trying to solve a 4th order nonlinear PDE for a real function $u(x,y)$ of two variables. It is too complicated to reproduce here but it exhibits the following two very nice properties:
1) if ...

**1**

vote

**0**answers

40 views

### Modulus of Continuity for an Analytic Function on an Ellipse

This is a question which I stumbled upon while working on Legendre Polynomials, but it is actually a question in complex analysis.
Consider: Given $f\in C^{\infty} (E)$, where $E_{\rho} \subseteq ...

**4**

votes

**1**answer

160 views

### Embed a bordered Riemann surface into punctured Riemann surfaces?

Let $U$ be a bordered Riemann surface of genus $g$ with $n -1$ punctures and one hole (i.e., the border has one connected component). For any punctured Riemann surface $\Sigma$ of genus $g$ with $n$ ...

**3**

votes

**1**answer

82 views

### Wiener-Hopf factorization of matrices

Given a $2\times2$ matrix, which entries are functions in the complex plane $$\hat{A}(z)=\left(\begin{array}{cc}a(z)&b(z)\\c(z)&d(z)\end{array}\right)$$Where $a(z),b(z),c(z)$ and $d(z)$ are ...

**2**

votes

**0**answers

108 views

### The boundedness of an entire function along the imaginary axis

I am looking for an answer in the affirmative or the negative concerning the asymptotics of an entire function. The question, relatively simple to state, has proven very taxing to solve and requires ...

**7**

votes

**0**answers

159 views

### Biholomorphic neighborhoods of the boundary of Stein domains

Let $(X_1,J_1)$ and $(X_2,J_2)$ be Stein domains with the same contact boundary $(Y,\xi)$. Under what conditions does there exist a biholomorphism between a neighborhood of their respective boundaries ...

**3**

votes

**1**answer

89 views

### $L^p$ norm of boundary values of holomorphic function

I am looking for an estimate of the following form:
Suppose that $D\subset \mathbb{C}$ is a simply connected domain. Suppose that $F$ is holomorphic and bounded on $D$ and can be holomorphically ...

**1**

vote

**0**answers

62 views

### Explicit formula of biholomorphism between the rectangle and unit disk [closed]

From the Riemann mapping theorem we know that there exists a biholomorphism between the rectangle $R$ and the unit disk $D$, can we write this biholomorphic map explicitly?

**0**

votes

**1**answer

100 views

### How to calculate the expected value of complex-valued random variable? [closed]

Suppose $\theta_1,\theta_2,\cdots, \theta_n$ are independent and identically distributed (i.i.d.) real-valued random variables and here we specifically consider the uniform distribution in the ...

**3**

votes

**0**answers

98 views

### Siegel's article “The volume of the fundamental domain for some infinite groups”: trouble with understanding computations

This is the article I mentioned. While the idea of what Siegel is doing in order to compute the volume of the fundamental domain described in the article (the very first one, for there are discussed ...

**6**

votes

**1**answer

111 views

### Convex Hull of univalent functions and Bieberbach Conjecture

Consider the class $S$ of univalent functions on the unit disk $D$ normalized so that $f(0)=0$ and $f'(0)=1$.
Each function in $S$ satisfy the Bieberbach conjecture, that is the $n$-th coefficient in ...

**-4**

votes

**1**answer

175 views

### Proof of formula for $\pi$ in terms of infinite number [closed]

What is the shortest proof of the formula $\pi=\frac{\infty\sqrt[\infty]{-1}-\infty}{\sqrt{-1}}$? Here we choose the principal branch of the root. Hopefully a fairly elementary proof can be provided ...

**3**

votes

**0**answers

83 views

### State of the art for univariate complex polynomials factorization with algebraic coefficients

Let $\mathbb{K}:=\overline{\mathbb{Q}}$ be the field of algebraic numbers. We choose to represent an element of $\mathbb{K}$ as its minimal monic polynomial, which is a vector in some $\mathbb{Q}^n$.
...

**6**

votes

**2**answers

158 views

### Criterion for deciding the conformal class of a metric on a complete surface

For orientable closed Riemannian surfaces $(S,g)$, there is a constant curvature metric $\overline{g}$ on $S$ that is conformal to $g$ in the sense that $\overline{g} = e^ug$ for some smooth function ...

**2**

votes

**0**answers

100 views

### Asymptotic analysis of generating functions

Let $a_d\!\in\!{\mathbb R}^+$ with $d\!\in\!{\mathbb Z^+}$ be a sequence such that
$$\limsup \sqrt[d]{a_d}=1\,.$$
Define
$$F(z)=\sum_{d=1}^{\infty}a_d\,{\text{e}}^{d z}\,.$$
Suppose $F(z)$ admits an ...

**2**

votes

**0**answers

104 views

### Extension to real number system [closed]

Suppose you have equation involving a number $s$
$s^2+ 1 = 0$,
to solve it one needs to treat $s$ as complex number $s = \pm i$, and introduce $i$ as imaginary unit.
Now suppose you have equation ...

**5**

votes

**2**answers

489 views

### Holomorphy of a function with values in a Hilbert space

I asked the same question on MathStackExchange. EDIT: This question has now a open bounty worth +50 reputation on MSE.
Denote by $\mathbb C^\infty $ the Hilbert space $\ell^2 (\mathbb C)$. Fix $1\leq ...

**5**

votes

**0**answers

86 views

### Complex L^1 spaces; reference request

I have been doing a fair amount of research into a complex analytic modified version of the Mellin transform. I have hit a few roadblocks, and am hoping there may already be literature on the subject. ...

**3**

votes

**1**answer

139 views

### Do some kind of maximum principle exist on complex manifold?

Consider a holomorphic function $u:C\to C^n$, as $|u|^2 $is sub-harmonic, it satifies a maximum principle.
Do some general kind of complex manifold enjoy such property? Say, square of some distance ...

**2**

votes

**0**answers

43 views

### Interpolation polynomial smaller than its function?

Let $q$ be a real number such that $q>1$ and $f$ be an entire function on $\mathbb C$ such that $\overline{\lim}_{r\to+\infty}\limits\frac{\ln|f|_r}{\ln^2r}<\frac{1}{2\ln q}$, where ...

**3**

votes

**0**answers

112 views

### Automorphism groups of elliptic bundles

This is a question in complex geometry, but even for algebraic varieties I don't know the answer:
Let $S$ be a smooth compact Kähler surface (for example a smooth complex projective surface) that is ...

**3**

votes

**1**answer

129 views

### Growth comparision between an entire function and a related function

Let $p$ be a prime number, $\mathbb C_p$ be the completion of an algebraic closure of $\mathbb F_q\left(\left(\frac1T\right)\right)$ for the valution $v(x)=-\deg(x)$. Let $\sum_{n\ge0}a_nz^n$ be a ...

**2**

votes

**1**answer

100 views

### The motivation and application of Nevanlinna second main theorem for small functions

I once read some books about Nevanlinna theory, most of them will discuss the Nevanlinna main theorem small function theorem under some conditions. While, I know little motivation of small function ...

**3**

votes

**0**answers

204 views

### Funk-Hecke theorem on the complex sphere

I am interested in paper " Sharp constants in several inequalities on the Heisenberg group " of Rupert L.Frank and Elliott H.Lieb " http://arxiv.org/pdf/1009.1410v2.pdf. In this paper ( page 17 ), ...

**0**

votes

**0**answers

44 views

### Explicit solution of a Cauchy-type singular integral equation with regular part

I am doing research on the Riemann boundary value problem for bi-half-planes, and in a certain case I was able to reduce this problem to a linear singular integral equation of the form
...

**0**

votes

**1**answer

71 views

### a sum of ratios of quadratic forms

I have the following function that I would like to optimize over the value A
$$f(A)=\sum_k \frac{\mathbf{y}_k^H\left[\begin{array}{cc} 1&0\\ 0& A \end{array} ...

**1**

vote

**1**answer

84 views

### Visualization of non-Smirnov domains

Can one provide a graph of a non-chord arc(non-Lavrentiev) Jordan curve in the plane? That is, more of less, equivalent to a Jordan curve whose interior domain is a non-Smirnov domain.

**3**

votes

**2**answers

167 views

### Sampling Theorem for non-bandlimited Functions

The classical Shannon sampling theorem states that
a bandlimited function with $\mbox{supp } \hat f\subset [-1/2,1/2]$ can be uniquely determined by its samples $(f(i))_{i\in \mathbb{Z}}$ (The symbol ...

**5**

votes

**1**answer

283 views

### About the logarithmic derivative of the Riemann zeta function

Let $\rho=\beta+i\gamma$ a non-trivial zeros of the Riemann zeta function and $s=\sigma+it$ a complex number. It is possible to prove that ...

**1**

vote

**0**answers

61 views

### summability and analytic continuation

Let $d_n=LCM(1,\cdots,n)$. It is well-known that $d_n=e^{\Psi(n)}$ where $\Psi$ est the second Chebyshev function. One knows that $\Psi(x)=\sum_{k\le x}\Lambda(k)$ where $\Lambda$ is the Von Mangold ...