# Questions tagged [convergence]

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### Increase convergence near singular point

I have this integrand given by tinteg[z,zm,zh] where I want to integrate it in the range [0,zh]. However, the integrand is ...
64 views

### NSum complaining of being non-numerical

I am trying to evaluate the sum $\sum_{k,l=1}^{30}\frac{1}{(k^2+l^2+1)^{5/4}}$ so I write NSum[1/(1 + k^2 + l^2)^(5/4), {k, 1, 30}, {l, 1, 30}] but I get a message ...
46 views

### NDEigensystem convergence and comparison to DEigensystem

Consider the following eigenvalue differential equation $$-u_n''(x)+x^2u_n(x)=E_nu_n(x),\qquad x\in(-\infty,\infty).$$ If you know a little bit of physics, you would know that this is the ...
49 views

### NDEigensystem eigenvalue convergence problem

I am solving an eigenvalue equation (a time independent schrödinger equation) and want to find the eigenvalues ...
91 views

41 views

### Nintegrate providing results much smaller than what is expected

This is the first time I am posting something here. So, apologies if I make any mistake. I am dealing with a numerical integration in Mathematica-11.0 that has a Bessel function in it. In order to ...
767 views

### Bug in Integrate?

In v. 11.1.0.0 Mathematica for Linux Integrate[Sin[Cosh[t]], {t, 0, Infinity}] returns Integrate::idiv: Integral of Sin[Cosh[t]] does not converge on {0,[...
248 views

### Wolfram Language 12 says this absolutely convergent series does not converge. Is there any similar example?

I am reading "Lectures on complex function theory" by Takaaki Nomura. In this book, there is the following example: $\sum_{n=1}^{\infty} \sin(\pi(2+\sqrt{3})^n)$ converges absolutely. But ...
### Strange result for sum $\sum _{k=1}^{\infty } \frac{\sin (k (k-1))}{k}$
In this sum over $k$ Sum[Sin[k (k - 1)]/k, {k, 1, ∞}] the result still containes the summation index $k$. ...