Questions on special functions, useful functions that frequently appear in pure and applied mathematics (usually not including "elementary" functions).

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1
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1answer
47 views

Equailty involving Elliptic integrals and hypergeometric function

How to prove the following $$\,_2F_1\left(-1/2,-1/2,1,k^2 \right)=\frac{2}{\pi}\left(2E+(k^2-1)K \right)$$ where we define The complete integral of first kind $$K=K(k) = \int^1_0 ...
3
votes
1answer
69 views

Expressing upper incomplete gamma function of half-integer order in terms of gamma function?

N. M. Temme, "Special Functions" (Wiley 1996) gives the following expression that expresses the upper incomplete gamma function in terms of the ordinary gamma function, for integer orders: $$ ...
2
votes
1answer
25 views

Inequality with Bessel Functions of the first kind

How can be proven the following inequality: $$\int_0^1dx|J_k(x)'J_k(x)|\lt\frac{1}{2}\int_0^1dx|J_k(x)'^2|$$ where obviously: $J_k(x)'=\frac{d}{dx}J(k,x)$? Thanks.
25
votes
9answers
7k views

Why is $\Gamma\left(\frac{1}{2}\right)=\sqrt{\pi}$ ?

It seems as if no one has asked this here before, unless I don't know how to search. The Gamma function is $$ \Gamma(\alpha)=\int_0^\infty x^{\alpha-1} e^{-x}\,dx. $$ Why is $$ ...
4
votes
1answer
58 views

Infinite sum of Bessel Functions

I came across the following sum in my work involving the infinite sum of a product of Bessel functions. Does anyone have any idea of how to express this in a simpler form? 'a' and 'b' are positive ...
3
votes
0answers
69 views

Log Log Integrals III

The integrals \begin{align} I_{7} = \int_{0}^{1} \ln(x) \ \ln^{2}\left( \ln \left(\frac{1}{x}\right) \right) \ \frac{dx}{1-x} \end{align} and \begin{align} I_{8} = \int_{0}^{1} \ln(x) \ \ln^{2}\left( ...
2
votes
0answers
41 views

Log Log Integrals II

The integral \begin{align} I_{4} = \int_{0}^{1} \ln(1-x) \ \ln^{2}\left( \ln\left(\frac{1}{x}\right) \right) \ \frac{dx}{x} \end{align} can be expressed as \begin{align} I_{4} = \zeta^{''}(2) - ...
6
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0answers
216 views

Integral $\int_0^1 dx \frac{\ln x \ln^2(1-x)\ln(1+x)}{x}$

Hi I am trying to calculate $$ I:=\int_0^1 dx \frac{\ln x \ln^2(1-x)\ln(1+x)}{x}$$ Note, the closed form is beautiful (yes Beautiful) and is given by $$ I=−\frac{3}{8}\zeta_2\zeta_3 ...
18
votes
1answer
624 views

Integral $\int_{-\infty}^\infty J^3_0(x) e^{i\omega x}dx $

Hi I am trying to evaluate the integral $$ \mathcal{I}(\omega)=\int_{-\infty}^\infty J^3_0(x) e^{i\omega x}dx $$ analytically. We can also write $$ \mathcal{I}(\omega)=\mathcal{FT}\big(J^3_0(x)\big) ...
3
votes
0answers
26 views

integral involving hypergeometric function $\int^1_0\frac{_2F_1(p,p;p+1;-\frac{1}{y})}{y}\,dy$

I arrived at the following result $$\tag{1}\int^\infty_0 z^{p-1} E^2(z)\,dz=\frac{\Gamma(p)}{p}\int^1_0\frac{_2F_1(p,p;p+1;-\frac{1}{z})}{z}\,dz$$ where the exponential integral $E(z)$ is defined ...
0
votes
1answer
25 views

Reduction of DEs to Bessel equation

A question in my textbook asks me to write down the general solution to: $\frac{d}{dx}(x^2\frac{dR(x)}{dx}) + [k^2x^2 - n(n+1)]R(x) = 0$ in terms of Bessel functions. Now two similar questions ...
3
votes
2answers
53 views

Prove: $\sin (3\pi/2 - x) = -\cos(x)$

I know the sine of $3\pi/2$ is $-1$. So i plug it in the function making it. $\sin(-1-x) = -\cos x$. However, I don't know where to go from here.
1
vote
1answer
36 views

BesselJ function on negative real numbers

I have evaluated Bessel$J_v(x)$ with some real $v$ and negative real $x$ in MATHEMATICA. I cannot understand how the result is complex (non-real). I look at the series definition of BesselJ and I ...
6
votes
2answers
134 views

Infinite Series :$ \sum_{n=0}^\infty \frac{\Gamma \left(n+\frac{1}{2} \right)\psi \left(n+\frac{1}{2} \right)}{n! \left(n+\frac{3}{2}\right)^2}$

Prove that: $$\sum_{n=0}^\infty \frac{\Gamma \left(n+\frac{1}{2} \right)\psi \left(n+\frac{1}{2} \right)}{n! \left(n+\frac{3}{2}\right)^2} = \frac{-\pi^{\frac{3}{2}}}{12}\left( \pi^2+6\gamma(1-2\log ...
2
votes
1answer
133 views

How can I express such function as known functions or power series?

$$\int_0^x \cfrac{1}{1+\int_0^t \cfrac{1}{2+\int_0^{t_1} \cfrac{1}{3+\int_0^{t_2} \cfrac{1}{\cdots} dt_3} dt_2} dt_1} dt =f(x)$$ $$\int_{0}^{x} \frac{1}{n+h_{n+1}(t)}{d} t=h_n(x)$$ ...
8
votes
1answer
190 views

How find this value of $A$?

Question: Let $z\in C$ Find this value $A$,such $$\lim_{k\to +\infty}\left(k-\dfrac{W_{k^2}(z)}{W_{k}(z)}\right)= A\cdot i$$ where $i^2=-1$,and $w_{k}(z)$ is Lambert $W$ function:see ...
4
votes
0answers
163 views

Integral $=\int_0^\infty x^{\alpha -1}Li_n (-\sigma x) Li_m(-\omega x^r)dx$.

I am trying to calculate an integral that can be expressed in terms of infinite hypergeometric series by using transforms and Residue method, the integral is $$ ...
0
votes
0answers
47 views

Is $2\delta(x) \neq \delta(x)$?

$2\delta(x) \neq \delta(x)$ since, by definition, Can this been seen graphically though? If so, how? If not, why is it that they are mathematically different but graphically the same? Btw, I ...
0
votes
1answer
16 views

Solutions in terms of Bessel functions

I came across this question that asked to express solutions to: $$x^2y'' + xy' + (4x^2 - v^2)y = 0,\quad 0\le x<\infty$$ in terms of Bessel functions subject to the boundary conditions y(x) is ...
0
votes
1answer
16 views

Integral Bessel recurrence relation

I want to show that $\int x^vJ_{v-1}(x)dx = x^vJ_v(x) + C$. Now I know the recurrence relations of the Bessel equation/function and the one I need to use is $x^vJ_v(x) = x^vJ_{v-1}(x)$ I'm just ...
0
votes
1answer
15 views

What is the value of bessel functions at 0?

I would like to know what the value of the bessel functions of the first kind and the modified bessel of the first kind is at 0. I think for order 0 they are 1 and for orders greater than 0 they are ...
3
votes
0answers
51 views

Bessel J function problem

Let $\xi_{0k}$ be the k-th positive zero of $J_{0}$ Bessel function. Determine the coefficients $c_k$, so that $1 = \sum^{\infty}_{k=1} c_kJ_0(\frac{x \xi_{0k}}{2})$. I don't see what to do, is ...
1
vote
0answers
31 views

How to solve this infinte series related to bessel integral?

$$\int_0^z t^{\rho} J_{\mu}(at) J_{\nu}(bt) dt = \frac{(\frac 1 2 a z)^{\mu} (\frac 1 2 bz)^{\nu} z^{\rho + 1}}{\Gamma(\mu + 1)\Gamma(\nu + 1)} \times \sum_{k = 0}^{\infty} \frac{(-1)^k (\frac 1 2 a ...
0
votes
1answer
18 views

Graph of a Sine Function Increased on One Side

If we want something looks like this sine wave, what is a function that will satisfy this: Further, how can we make this go both ways, meaning either 1) a sine wave staying the same at the bottom ...
0
votes
1answer
37 views

A definite integral in terms of Meijer G-function

I am trying to find some relevant functional identities involving Meijer G-functions in order to prove $$ \int_0^\infty\frac{\log(x+1)}{x}\mathrm{e}^{-zx}\,\mathrm{d}x = G^{3,1}_{2,3}\left(z \middle| ...
1
vote
1answer
287 views

Equation containing modified bessel functions and exponential function

I'm trying to find a approximation solution for the following equation: ${e^{ - x}}\left[ {{I_o}\left( x \right) + {I_1}\left( x \right)} \right] = C$ where $I_0$ and $I_1$ is the modified Bessel ...
1
vote
2answers
55 views

Determining if any general funtion u(x,y) makes f(z)=u(x,y)+iv(x,y) analytical

I have a question about Complex Analytical functions. I have some homework that asks: let $f(z) = u(x,y) + iv(x,y)$. Indicate the following functions for which u(x,y) may be analytic: $6(x^2-y^2)$ | ...
0
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0answers
18 views

Numerical evaluation of an infinite 3D sum of cosine?

Consider the following function: $$f\left(x, y, z\right) = \sum_{\left(n, m, l\right)\in \mathbb{N}_*^3}e^{-\alpha\left(n^2+m^2+l^2\right)}\frac{\cos\left(\omega nx\right)\cos\left(\omega ...
0
votes
0answers
20 views

how to solve this product of bessel integral?

$$W = \int_0^z r J_7(ar) J_0(br) dr$$ i would like to solve this integration. Any information regrading this helps me a lot. Thank you.
1
vote
1answer
34 views

Characterization of nowhere differentiable functions

Let $N:=\{f\in C([0,1])\vert \text{ f is nowhere differentiable } \}$ and $A_n = \{f\in C([0,1]) \vert \exists x\in [0,1]s.t. \forall y\in[0,1]: |f(x)-f(y)|\leq n |x-y|\}$. Now I have already ...
3
votes
2answers
340 views

expression for the sum involving digamma function

I got this answer from WolframAlpha. Does anyone know how even to approach it to obtain the solution using digamma function. Please don't solve it, just show me in the right direction! $$ ...
1
vote
1answer
69 views

Calculate the residue of $\cot\pi z$ at poles $z=n$

I'm having trouble calculating the residue of $f(z) =\cot\pi z$. The function has a simple pole for every integer n, and i'm, trying to find the residue at n. I know that by the residue theorem: ...
0
votes
1answer
49 views

Bessel function radius of convergence

Assuming the series representation of the Bessel function $J_v(x)$ I was given that the radius of convergence was ∞. I've tried using the ratio test but I dunno how the gamma function would ...
3
votes
1answer
51 views

Is there a simpler form for $\Re \frac{\Gamma(1/2-i)}{\Gamma(1-i)}$?

Is there a simpler (i.e. manifestly real) form for $\Re \frac{\Gamma(1/2-i)}{\Gamma(1-i)}$ or $\Im \frac{\Gamma(1/2-i)}{\Gamma(1-i)}$, or more generally for $\frac{\Gamma(1/2-ia)}{\Gamma(1-ia)}$ with ...
0
votes
1answer
29 views

Radius of Convergence ratio test

using the ratio test for the following sum from n = 0 to infinity of $$ \sum_{m=0}^{+\infty}\frac{(-1)^m}{(m!)^2} x^{2m +10} $$ I need to find the radius of convergence. I managed to get up to ...
5
votes
2answers
104 views

Integral $\int_0^1 \frac{x\log x+1-x}{x \log^2 x}\log(1+x)\, dx=\log\frac{4}{\pi}$

Hi I am trying to prove this $$ I:=\int_0^1 \frac{x\log x+1-x}{x \log^2 x}\log(1+x)\, dx=\log\frac{4}{\pi}. $$ Thanks. This is just a beautiful integral for many reasons. Logs are everywhere and an ...
0
votes
0answers
7 views

Ratio of spherical Bessel functions $y_n(z)/j_n(z),\ z$ complex, $n$ large

Is there some way of calculating the ratio of the spherical Bessel function of the second kind to the Bessel function of the first kind of the same order, similar to the way there is for the ratio of ...
4
votes
3answers
226 views

Asymptotic expansion of $J(t) = \int^{\infty}_{0}{\exp(-t(x + 4/(x+1)))}\, dx$

I want to derive an asymptotic expansion for the following Bessel function. I think I need to rewrite it in another form, from which I can integrate it by parts. I am interested in obtaining the ...
0
votes
0answers
23 views

Incomplete gamma function in polar form

How can one write the incomplete gamma function in polar coordinates?
1
vote
2answers
54 views

Gamma Function Result

I want to know the way to prove that $$ \Gamma(n + 1/2)= \frac{(2n)! \sqrt{\pi}}{4^n n!}. $$ I tried writing term by term and it gives the result, but I want to know how to prove it without ...
0
votes
0answers
26 views

The representation of the Gaussian Q-function

The gaussian Q-function is well-known to be given in two famous forms, given as: $$ \mathcal{Q} = \frac{1}{\sqrt{2\pi}} \int_{x}^{\infty}\! \operatorname{exp}\left\{ -\frac{y^2}{2} \right\} ...
1
vote
1answer
25 views

Low bound of Dirichlet eta function

every one. Suppose that $\eta(s)$ is Dirichlet eta function, I may find a low bound of this function, namely $\eta(2n)>\frac{2^{2n-1}-2}{2^{2n-1}-1}$ with $n>1$ and $n$ is a integer. But is ...
0
votes
1answer
34 views

factorization of an expression involving gamma function

Does the equation $\Gamma(x+1/2)\Gamma(x-1/2)=\Gamma(x+iy)\Gamma(x-iy)$, where $\Gamma(z)$ is the Gamma function and $i=\sqrt{-1}$, have any solution assuming $x,y$ are both real and $x>1/2$? This ...
4
votes
2answers
142 views

Integral $\int_0^1 \log \Gamma(x)\cos (2\pi n x)\, dx=\frac{1}{4n}$

$$ I:=\int_0^1 \log \Gamma(x)\cos (2\pi n x)\, dx=\frac{1}{4n}. $$ Thank you. The Gamma function is given by $\Gamma(n)=(n-1)!$ and its integral representation is $$ \Gamma(x)=\int_0^\infty t^{x-1} ...
9
votes
1answer
163 views

The value of the trilogarithm at $\frac{1}{2}$

From the functional equation $$\text{Li}_{3}(z) + \text{Li}_{3}(1-z)+ \text{Li}_{3} \Big( 1 - \frac{1}{z} \Big) = \zeta(3) + \frac{\ln^{3} (z)}{6}+ \frac{\pi^{2} \ln (z) }{6}- \frac{\ln^{2} (z) ...
2
votes
2answers
84 views

Identity involving the rising factorial

I am reading a book about hypergeometric functions and in a proof of a transformation they use the supposedly obvious fact $$ \displaystyle\frac{(c-a-b)_{n-r}}{(n-r)!} = \frac{(c-a-b)_{n} ...
0
votes
0answers
38 views

What will the integration be ?

Using the orthogonality property of bessel function we have Now what will be the formula for the following
0
votes
1answer
37 views

Determine whether the functions are odd, even, or neither without using graphs

Determine whether the following functions are odd, even, or neither: $y=10(e^x+e^{-x})$ $y=e^{-x} \cos(2x)$ $y=x^8\sin (2x)$
4
votes
1answer
49 views

Fundamental period of the WeierstrassP elliptic function?

Consider the WeierstrassP elliptic function $\wp(z, g_2, g_3)$ with the invariants $g_2\in\mathbb{R}$ and $g_3\in\mathbb{R}$: $$\wp'(z)^2 = 4\wp(z)^3 - g_2 \wp(z) - g_3$$ According to Wikipedia when ...
2
votes
2answers
180 views

Dirac delta function divided by Dirac delta function

Is the following defined: (Dirac delta function divided by Dirac delta function) $$f = \frac{\delta}{\delta} = ?$$