numerical methods

Calculating the Hermite functions

The Hermite functions appear as the solutions of the quantum mechanical harmonic oscillator. But they have applications in many other fields and applications, e.g., pseudospectral methods. The Hermite functions $h_n(x)$ are defined as\begin{equation}\label{eq:h}h_n(x) = \frac{1}{\sqrt{\sqrt{\pi} 2^n n!}} \mathrm{e}^{-x^2/2} H_n(x) \,,\end{equation} where $H_n(x)$ denotes the $n$th Hermite polynomial defined via the recurrence relation\begin{equation}H_{n}(x) = 2xH_{n-1}(x)-2(n-1)H_{n-2}(x)\end{equation} with… Continue reading Calculating the Hermite functions

numerical methods

The Lanczos algorithm

Finding the eigenvalues and eigenvectors of large hermitian matrices is a key problem of (numerical) quantum mechanics. Often, however, the matrices of interest are much too large to employ exact methods. A popular and powerful approximation method is based on the Lanczos algorithm. The Lanczos algorithm determines an orthonormal basis of the Kyrlov sub-space $\mathcal{K}_k(\Psi,… Continue reading The Lanczos algorithm

TRNG

New TRNG release

A new version of TRNG (Tina’s Random Number Generator Library) has been released. TRNG may be utilized in sequential as well as in parallel Monte Carlo simulations. It does not depend on a specific parallelization technique, e.g., POSIX threads, MPI and others. The new version 4.17 is a bug fix and maintenance release.