The #QRT maps (Quispel, Roberts & Thompson, 1988) are dynamical maps in two variables that preserve a bi-quadratic invariant. They have a simple construction as the composition of two involutions. /1 Each involution is given by intersecting a line with the graph of the invariant, taken to be a vertical and a horizontal line respectively. /2

My story on elliptic functions starts with planetary orbits img: commons.wikimedia.org/wiki/File:Orbi… In 1609, Kepler published two of his laws on planetary motion. The first law says: "The orbit of every planet is an ellipse with the Sun at one of the two foci." ☞ en.wikipedia.org/wiki/Kepler%27…

I have long thought of the Gamma function Γ(z) as a mathematical beauty, not only because of the utter simplicity of the equation it satisfies: Γ(z+1)= z Γ(z), but also because it is a transcendental function, known not to satisfy any (algebraic) differential equation. That simple equation is accompanied by the initial condition Γ(1)= 1.

Today, I finally arrived at a point where I will need to cite Ramanujan [img from G. E. Andrews and B. C. Berndt, Ramanujan’s Lost Notebook. Part I, Springer 2005] To clarify this image a little more, I should have explained that q is a given (complex) number, assumed to satisfy |q|<1 …

I am getting to like prime ideals 👉🏼 en.m.wikipedia.org/wiki/Prime_ide… Perhaps it’s more accurate to say I like all mathematical objects which reveal their secrets to me slowly…#mathematicallife

How many methods of proof do you know? 1. Proof by vigorous handwaving. 2. Proof by exhaustion ..