Conway’s Big Picture
In this note we briefly describe the combinatorial/diagrammatic “big picture” framework introduced by J.H. Conway in his paper Understanding groups like \(\...
Recent Posts
The Rational Projective Determinant
For even \(n\), the rational projective determinant is a canonically defined function \(\mathrm{Pdet} : \mathrm{Mat}(n;\mathbb{Q}) \to \mathbb{Z}\) introduc...
The Friedrichs Extension of an Unbounded Operator
Definition 1. Let \(\mathcal{H}_0\) and \(\mathcal{H}_1\) be Hilbert spaces. An unbounded operator \(\mathcal{H}_0 \to \mathcal{H}_1\) is a linear map \begin...
Delay Differential Equations I
Consider a differential equation of the form \begin{equation} \label{eq:dde} \frac{\mathrm{d}x}{\mathrm{d}t} = f(t, x(t), x(t - \tau)) \end{equation} for ...
Delay Differential Equations II
In the note Delay Differential Equations I we introduced a simple algorithm for solving delay equations of the form \begin{equation} \label{eq:dde-std} \f...