Let $f(z)$ be an analytic function on $C^+=\{\Re z>0\}$, and we have the following (weaker) estimates $$ |f(re^{i\theta},a)|\leq C (r\cos\theta)^{-n}, ~~~r>0,-\frac{\pi}{2}<\theta<\frac{\pi}{2}, $$ for some constant $C$ and $n>0$. Furthermore, on the positive real line, and for any fixed $a>0$, we have the following (stronger) estimates $$ |f(r,a)|\leq C \frac{r}{a^{n+1}},~~~0<r\leq a, $$ where $C$ is a constant independent with $a$. My question is can we also get the following improved estimates of $f$ $$ |f(re^{i\theta},a)|\leq C \frac{r}{a^{n+1}},~~~0<r< a,~~-\frac{\pi}{2}<\theta<\frac{\pi}{2}? $$ If not, can you give a counterexample to this? The motivation of this question comes from estimating the Poisson semigroup $e^{-z\sqrt{-\Delta}}$ for small $|z|$ With $\Re z>0$.To be more precise, if we let $K(z,x,y)$ be its kernel, then $K$ satisfies the estimates above with $a=|x-y|$. Although we can compute the kernel explicitly (for all $\Re z>0$ ) by using Fourier transform ($K(z,x,y)=\frac{z}{(z^2+a^2)^{n+1}}$,a=|x-y|), I think one may also obtain this by combining the kernel estimates on the positive real line (the second estimate above) with a weaker estimates on the right half plane (the first estimate above) and some analytic function theory. I don't know theorems like Hadamard's Three line lemma or its variants would be useful here. Thanks in advance for any comment.
2026-03-29 22:25:21.1774823121
estimating a particular analytic function on a bounded sector.
237 Views Asked by Bumbble Comm https://math.techqa.club/user/bumbble-comm/detail AtRelated Questions in COMPLEX-ANALYSIS
- Minkowski functional of balanced domain with smooth boundary
- conformal mapping and rational function
- orientation of circle in complex plane
- If $u+v = \frac{2 \sin 2x}{e^{2y}+e^{-2y}-2 \cos 2x}$ then find corresponding analytical function $f(z)=u+iv$
- Is there a trigonometric identity that implies the Riemann Hypothesis?
- order of zero of modular form from it's expansion at infinity
- How to get to $\frac{1}{2\pi i} \oint_C \frac{f'(z)}{f(z)} \, dz =n_0-n_p$ from Cauchy's residue theorem?
- If $g(z)$ is analytic function, and $g(z)=O(|z|)$ and g(z) is never zero then show that g(z) is constant.
- Radius of convergence of Taylor series of a function of real variable
- contour integral involving the Gamma function
Related Questions in ANALYSIS
- Analytical solution of a nonlinear ordinary differential equation
- Finding radius of convergence $\sum _{n=0}^{}(2+(-1)^n)^nz^n$
- Show that $d:\mathbb{C}\times\mathbb{C}\rightarrow[0,\infty[$ is a metric on $\mathbb{C}$.
- conformal mapping and rational function
- What are the functions satisfying $f\left(2\sum_{i=0}^{\infty}\frac{a_i}{3^i}\right)=\sum_{i=0}^{\infty}\frac{a_i}{2^i}$
- Elementary question on continuity and locally square integrability of a function
- Proving smoothness for a sequence of functions.
- How to prove that $E_P(\frac{dQ}{dP}|\mathcal{G})$ is not equal to $0$
- Integral of ratio of polynomial
- What do I miss on this function? $f(t) = (t-1)^{s/2}-t^{s/2}+1$
Related Questions in INTERPOLATION
- Almost locality of cubic spline interpolation
- Reverse Riesz-Thorin inequality
- How to construct a B-spline from nodal point in Matlab?
- Show that there is a unique polynomial of degree at most $2n+1$ such that $q^{[k]}(x_1)=a_k,$ $q^{[k]}(x_2)=b_k$ for $k=0, \dots, n$.
- Show that there is a unique polynomial of degree at most $2k+1$ such that $p^{[j]}(x_1)=a_j \text{ and } p^{[j]}(x_2)=b_j \text{ for } j=0,\dots, k.$
- How to find x intercept for a polynomial regression curve(order 7)
- How to obtain generalized barycentric coordinates for n-sided polygon?
- the highest degree of the polynomial, for which the above formula is exact?
- Interpolation method that gives the least arc lenght of the curve.
- Find the maximum absolute interpolation error
Trending Questions
- Induction on the number of equations
- How to convince a math teacher of this simple and obvious fact?
- Find $E[XY|Y+Z=1 ]$
- Refuting the Anti-Cantor Cranks
- What are imaginary numbers?
- Determine the adjoint of $\tilde Q(x)$ for $\tilde Q(x)u:=(Qu)(x)$ where $Q:U→L^2(Ω,ℝ^d$ is a Hilbert-Schmidt operator and $U$ is a Hilbert space
- Why does this innovative method of subtraction from a third grader always work?
- How do we know that the number $1$ is not equal to the number $-1$?
- What are the Implications of having VΩ as a model for a theory?
- Defining a Galois Field based on primitive element versus polynomial?
- Can't find the relationship between two columns of numbers. Please Help
- Is computer science a branch of mathematics?
- Is there a bijection of $\mathbb{R}^n$ with itself such that the forward map is connected but the inverse is not?
- Identification of a quadrilateral as a trapezoid, rectangle, or square
- Generator of inertia group in function field extension
Popular # Hahtags
second-order-logic
numerical-methods
puzzle
logic
probability
number-theory
winding-number
real-analysis
integration
calculus
complex-analysis
sequences-and-series
proof-writing
set-theory
functions
homotopy-theory
elementary-number-theory
ordinary-differential-equations
circles
derivatives
game-theory
definite-integrals
elementary-set-theory
limits
multivariable-calculus
geometry
algebraic-number-theory
proof-verification
partial-derivative
algebra-precalculus
Popular Questions
- What is the integral of 1/x?
- How many squares actually ARE in this picture? Is this a trick question with no right answer?
- Is a matrix multiplied with its transpose something special?
- What is the difference between independent and mutually exclusive events?
- Visually stunning math concepts which are easy to explain
- taylor series of $\ln(1+x)$?
- How to tell if a set of vectors spans a space?
- Calculus question taking derivative to find horizontal tangent line
- How to determine if a function is one-to-one?
- Determine if vectors are linearly independent
- What does it mean to have a determinant equal to zero?
- Is this Batman equation for real?
- How to find perpendicular vector to another vector?
- How to find mean and median from histogram
- How many sides does a circle have?