Questions on the special mathematical functions implemented in Mathematica.
-1
votes
0answers
46 views
Numerical Integration With a Singularity
I am trying to solve a differential equation using wavelets and got stuck to find the numerical values:
Here is the code I wrote:
...
0
votes
1answer
48 views
Plot $ g(r) = \int_0^\pi J_0(w\ r)\ \mathrm dw $
I want to plot $g(r)$ as a function of $r$ but $g(r)$ at each value of $r$ is an integral of the Bessel function over the the limits of $w$.
0
votes
0answers
33 views
Numerically integrating a highly oscillatory multi-dimensional Bessel function with good precision
This is a follow up question to Numerically integrating a highly oscillatory Bessel function with good precision.
Now I am considering a three dimensional integral,
...
1
vote
2answers
84 views
Numerically integrating a highly oscillatory Bessel function with good precision
I am trying to evaluate the following integral
Integrate[Csch[w]^2 (w BesselJ[1, w Sqrt[y]/π]^2), {w, 0, Infinity}]
in an asymptotic large ...
0
votes
0answers
40 views
Indefinite integration of products of Bessel functions [on hold]
Is there any way to solve any of the following indefinite integrals in Mathematica?
...
0
votes
0answers
35 views
Strange result for rapidly converging series for $\zeta(4)$ [closed]
Denote by $\zeta$ the Riemann Zeta function for positive integers defined by its usual formula:
$$
\zeta(n)=\sum_{m=1}^{\infty}m^{-n}.
$$
It is well known that
$$ {\displaystyle {\begin{aligned}\...
9
votes
5answers
224 views
NDEigenvalues vs. FindRoot for finding the eigenvalues of Airy equation?
Say I am trying to find the first 5 eigenvalues of the differential equation $f''(x)=\lambda x f(x)$, on the interval [-1,0], with boundary conditions $f(-1)=f(0)=0$.
I will try to do this 3 ways, ...
0
votes
1answer
44 views
Numerical Approximation of erfc
I have a crazy output. I already tried the N[] function. All it does is condense the inputs. Any idea of how to have a numerical output from the code?
0
votes
1answer
62 views
Solving two nonlinear equations in two unknowns
This is my code defining two nonlinear equations. I want to solve them simultaneously.
...
1
vote
2answers
119 views
Numerical integration with Dirac delta
I have some complicated function depending on many arguments $x,y,z$ and parameter $a$ multiplied by Dirac delta of another function,
$$
\tag 1 f(a,x,y,z) = g(a,x,y,z)\delta(t(a,x,y,z))
$$
I want ...
1
vote
0answers
34 views
3
votes
0answers
71 views
Summation of the multipole expansions [closed]
Let $ \vec\Omega, \vec\Omega' $ be two unit vectors in $ \mathbb R^3 $ such that $ \vec\Omega\cdot\vec\Omega' = t $ and let $ r > 0 $. The multipole expansion for the exponential reads:
$$
\...
1
vote
0answers
21 views
Inverse of Normal Distribution CDF incorrect for large value?
I have a function F which is the CDF of the standard normal distribution. The inverse of F should be infinity at 1. However, I ...
14
votes
4answers
247 views
Terrible accuracy of DawsonF
DawsonF[30.] returns 0. The correct value is 0.016676...
At least it prints a warning message,
...
2
votes
2answers
78 views
Integration with Bessel function as result
When I try to calculate this integral,
1/(2*Pi)*Integrate[ Exp[I*2*θ]*Cos[1/2 (7 + Cos[θ])], {θ, 0, 2*Pi}]
Mathematica is unable to compute it. But the result ...
3
votes
2answers
112 views
0
votes
0answers
38 views
Analytic derivatives of LegendreP[a, z] w.r.t. a at a = 0?
I am interested in finding analytic expressions for various derivatives of the LegendreP[a,z] w.r.t. a at ...
4
votes
1answer
78 views
Tips for Complicated Indefinite Integrals
I would like to have an analytical expression for some complicated indefinite integrals (example below). I am able to solve these integrals numerically, and I am able to plot them in Mathematica, ...
6
votes
1answer
270 views
What is wrong with this code? (Usage of FunctionInterpolation and how to make code efficient)
I am trying to create an interpolation out of a function that comes from an improper integral. The end goal is to make a 3d plot over a specific region. Specifically, I have the following code:
...
5
votes
2answers
55 views
How to force DSolve to return ODE solution in terms of BesselK instead of BesselY
I'm trying to solve the following problem:
...
1
vote
2answers
122 views
Why Mathematica does nothing with the expression Gamma[2 z]? [closed]
Could someone tell me why Mathematica just returns the input with this expression:
Gamma[2z]
Gamma[2 z]
?
I expected this result:
$Γ(2z)=\frac{2^{2z-1}Γ(z)Γ(...
0
votes
1answer
83 views
Analytical form of the answer of a definite integral
I am trying to find out the analytical form of the answer of the following integration,
$$I=\int_0^l r \, dr \int_0^{2\pi} \, d\phi (iks)[ \frac{\exp [ikx_0(N+r^2)^{1/2}]}{[x_0(N+r^2)^{1/2}]}\frac{\...
-1
votes
1answer
62 views
Numerical Inversion of an incomplete beta function expressed as gauss hypergeometric function using Mathematica
I am currently working with this hypergeometric function ${_2}F_1$,
$\rho(r)=\frac{2b}{1-q}(1-(\frac{b}{r})^{1-q})^{\frac{1}{2}}{_2}F_1(\frac{1}{2},1-\frac{1}{q-1},\frac{3}{2},1-(\frac{b}{r})^{1-q})$
...
0
votes
2answers
83 views
Product of large number with a very small number returns zero because Mathematica sets the very small number equal to zero [closed]
I have a product Exp[-I*Pi*x]*BesselK[-1, 2.43*Ix]. Now, Exp[-I*Pi*x] grows larger and larger as $x$ increases for imaginary ...
1
vote
1answer
72 views
Integral of modified Bessel function is wrong
A simple integration of a modified Bessel function gives:
...
1
vote
0answers
128 views
Approximate the relationship between 6 nonlinear functions involving elliptic integrals
I am trying to solve a physics-related problem, which results in approximating a relationship between 6 symbolic functions $F_1(\alpha,\beta ,x_0,y_0),F_2(\alpha,\beta ,x_0,y_0),...,F_6(\alpha,\beta ,...
3
votes
1answer
36 views
Strange automatic Hypergeometric2F1 simplification
On this Wolfram Functions page we can find the following identity:
...
3
votes
1answer
86 views
Problem with the function N with second argument
I was asked to look at a complicated definite integral that could be integrated analytically, but numerically did not behave as expected. After a lot of simplifications I arrived at the following:
<...
1
vote
0answers
38 views
Inverse Laplace transform of powers with an arbitrary index
Tried for Inverse Laplace transform (ILT) for the following:
L[s] = (L /(L + s) w + Q /(Q + s) (1 - w))^n
$L[s]$ can also be written as
$$L[s]=\sum_{k=0}^n\...
4
votes
3answers
144 views
Finding Root of BesselJ [closed]
When I work on some physical problem I needed to know how to get all of first 100 roots of BesselJ[n,x] function -which is a quasi periodic function-, as a List. I ...
2
votes
0answers
39 views
Expansion of HypergeometricU
I try to get the first three terms of expansion of HypergeometricU in Mathematica.
My input is ...
0
votes
0answers
52 views
Question regarding multidimensional integral
I would like to compute the following iterated integral in 3 dimesions:
$$
\int_{-\infty}^\infty \int_{-\infty}^\infty \left|\int_{-\infty}^\infty f(y)f(y-t)e^{-i 2 \pi t \xi} dy\right|dt d\xi
$$
...
4
votes
0answers
59 views
Series of LegendreP[a,b,x] takes ages in Mathematica 11
My institution just upgraded to Mathematica 11.3 (from v10) and I'm experiencing a problem that is absent in Mathematica 10. Namely,
...
2
votes
0answers
41 views
How does one generically expand the argument of a gamma function? [closed]
I have expressions of the form
Gamma[2 (56 + k)]
which I would like to convert to
Gamma[112 + 2 k]
But
...
0
votes
0answers
85 views
Plotting a function with Dirac delta function and its derivative
I am trying to plot the following expression which is a function of delta and its derivative:
\begin{equation}
y(t)=sin[\alpha t]+\frac{1}{\alpha^2}f(t)[(1-cos[\alpha t])+(\frac{t}{\alpha}-sin[\alpha ...
3
votes
0answers
95 views
Issues with the series expansion of Nielsen generalized polylogarithms in Mathematica 11.3
In Mathematica 9, 10.3 and 11.0 I can easily expand PolyLog[2, 2, x] around
$x=1$ using
...
2
votes
1answer
86 views
How to take the curl of a vector function involving hypergeometric functions?
I have a vector function involving a hypergeometric function as its inner constituent. I need to take the curl of this vector and when I do, Mathematica prompts this array of errors:
...
0
votes
1answer
74 views
Evaluate integral containing Erfc, Exp and Log [closed]
I'm trying to find the solution to the integral below. It runs in Mathematica but does not produce any output.
Every other part of the code works fine except the integral involving Exp, Erfc and Log ...
3
votes
2answers
75 views
Maximising a function by finding roots of the derivative is too slow
I have the function r11[t,k] defined as follows
...
3
votes
1answer
82 views
Incorrect Series with EllipticTheta under 11.3
The following program gives the correct coefficients under versions 7, 10.2 or 11.0
...
3
votes
1answer
95 views
How to make Mathematica substitute exact numerical values of (derivatives) 2F1
I have a long output that contains Taylor expansion of some function. Some of the coefficients are combinations of the (derivatives of) 2F1 at nice integer values of the coefficients. I can see that ...
0
votes
1answer
64 views
Is there an error pertaining to HypergeometricU function on functions.wolfram.com?
If one clicks on the last of the nine formulas on
http://functions.wolfram.com/HypergeometricFunctions/Hypergeometric2F1/17/02/07/
one obtains
Hypergeometric2F1[a, b, c, z] == HypergeometricU[a, b, a +...
0
votes
1answer
68 views
Reduce the product of two hypergeometric functions to a single hypergeometric function [closed]
I have this product of two hypergeometric functions
...
1
vote
1answer
38 views
Simplification of a JacobiCN Integral
Consider the following indefinite integral:
Assuming[A > 0 && B > 0 ,
Integrate[1/(1 - A JacobiCN[B x, k]^2), x] // FullSimplify]
-((...
2
votes
2answers
63 views
Problem while integrating bessel functions
I am trying to integrate various expressions with Bessel functions. In order to learn basics with Mathematica, I have decided to try a simple case to see what is going on.
I did :
...
2
votes
0answers
107 views
Is $\mathrm{EllipticPi}(n,\varphi, m)$ periodic for $n>1?$
The Wolfram function site lists the quasi-periodicity relation for the incomplete elliptic integral EllipticPi restricted to $-1\le n\le 1$
although actually it seems to work for $n<-1$ and $n \sin^...
0
votes
4answers
69 views
Solving an equation involving elliptic integral
Consider the following function:
f[θ_] =
Integrate[1/(Cot[θ]^2 - Sin[θ]^2)^(1/2), θ];
Now, I want to determine the value of $\theta$ for which say $f(θ)=1$. I ...
2
votes
2answers
73 views
Plot of partial derivative looks wrong and does not match the surface plot of the function
I have a function and I'm using Wolfram Cloud to analyze it.
F[p_, n_] := InverseBetaRegularized[0.1, p*n + 1, (1 - p)*n + 1]
When I plot the function, it looks ...
4
votes
2answers
133 views
Is Mathematica unaware of an integral representation of the modified Bessel function of the second kind BesselK[0, x]?
Mathematica is unable to produce a result for the following definite integral:
$$\int\limits_{0}^{\infty}\cos{(x \sinh{t})} \ dt$$
...
3
votes
3answers
83 views
Numerically evaluating and plotting functions involving complete Elliptic integrals
I have an equation like this
$$-K(y)-\frac{\pi J}{2 \sqrt{\lambda }}+\frac{E(y)}{1-y}=0$$
1/(1 - y) EllipticE[y] - EllipticK[y] - (J π /(2 Sqrt[λ])) == 0
...
