Why when an analytic function has poles which are outside the domain of integration but lie very close to it, its numerical integration by means of a quadrature rule can give very poor? Why the function should be also defined outside the interval of the integration?
2026-04-23 18:27:47.1776968867
Why when we approximate an analytic function has poles outside the interval of the integration give poor accuracy?
88 Views Asked by Bumbble Comm https://math.techqa.club/user/bumbble-comm/detail At
1
There are 1 best solutions below
Related Questions in INTEGRATION
- How can I prove that $\int_0^{\frac{\pi}{2}}\frac{\ln(1+\cos(\alpha)\cos(x))}{\cos(x)}dx=\frac{1}{2}\left(\frac{\pi^2}{4}-\alpha^2\right)$?
- How to integrate $\int_{0}^{t}{\frac{\cos u}{\cosh^2 u}du}$?
- Show that $x\longmapsto \int_{\mathbb R^n}\frac{f(y)}{|x-y|^{n-\alpha }}dy$ is integrable.
- How to find the unit tangent vector of a curve in R^3
- multiplying the integrands in an inequality of integrals with same limits
- Closed form of integration
- Proving smoothness for a sequence of functions.
- Random variables in integrals, how to analyze?
- derive the expectation of exponential function $e^{-\left\Vert \mathbf{x} - V\mathbf{x}+\mathbf{a}\right\Vert^2}$ or its upper bound
- Which type of Riemann Sum is the most accurate?
Related Questions in APPROXIMATION
- Does approximation usually exclude equality?
- Approximate spline equation with Wolfram Mathematica
- Solving Equation with Euler's Number
- Approximate derivative in midpoint rule error with notation of Big O
- An inequality involving $\int_0^{\frac{\pi}{2}}\sqrt{\sin x}\:dx $
- On the rate of convergence of the central limit theorem
- Is there any exponential function that can approximate $\frac{1}{x}$?
- Gamma distribution to normal approximation
- Product and Quotient Rule proof using linearisation
- Best approximation of a function out of a closed subset
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?
The question asked about poor performance of numerical integration of analytic functions with poles near the interval of integration. The Wikipedia article Runge's phenomenon gives a good example of this where a rational function with poles is evaluated at equidistant points and approximated with a polynomial. Integrating the polynomial is easy but the polynomial to be integrated is a poor fit for the function and hence yields a poor integration result. The article suggest some alternative ways to approximate the function to give better fit.
The question also asked
is not clear to me. In general we are dealing with Meromorphic functions. The Wikipedia article states
Notice the use of "open subset $D$ of the complex plane". The behavior of the function is very closely related to the topology of the complex plane. Its natural domain is open subsets of the complex plane. Thus, while the interval of integration is of primary importance, a real interval is not an open domain in the complex plane. The behavior of the function on open domains containing the interval has an impact on the behavior in the interval itself and vice versa. That is why poles outside the real interval can have a substantial effect on fitting by polynomials. A much better fit could be found if rational functions are allowed to better account for poles.