# Browsing category dome

## Dictionary of Mathematical Eponymy: Hoberman Sphere

What are they? I thought, until I looked closely, that we had a Hoberman sphere in the children’s toybox. We don’t: we have something closely related to it, though. The Hoberman mechanism comprises a series of pairs of pivoted struts arranged end to end. Each pair looks a little like

## The Dictionary of Mathematical Eponymy: Sophie Germain primes

What are they? A Sophie Germain prime is a prime such that $2p+1$ is also prime - for example, 23 is a Sophie Germain prime since 47 is also prime. The largest known Sophie Germain prime has close to 400,000 digits; it is conjectured that there are infinitely many such

## The Dictionary of Mathematical Eponymy: The Fermat Cubic

So far in the Dictionary of Mathematical Eponymy, I’ve not picked anyone properly famous. I mean, if you’re a keen recreational mathematician, you’ll have heard of Collatz or Banach; a serious mathematician might know about Daubechies, and a chess enthusiast would conceivably have come across Elo. But everyone has heard

## Dictionary of Mathematical Eponymy: Elo ratings

As I write this, classical chess’s top two players are Magnus Carlsen of Norway (rated 2835) and the USA’s Fabiano Caruana, who has a rating of 2832. Very close! But what do the rankings mean? FIDE1 uses the Elo rating system, a methodical - and mathematical - system for distilling

## The Dictionary of Mathematical Eponymy: Daubechies Wavelets

Before I dive in to Daubechies wavelets, a confession: at university, Fourier series were the bane of my existence. I could do them, under duress, but in the same way as I set up the audio for Wrong, But Useful1: I had a recipe of steps I needed to follow,

## Dictionary of Mathematical Eponymy: The Collatz Conjecture

What it is Every so often, one comes across a teacher who is Properly Evil. I’ll spare names here, but I have a clear, strong memory of being introduced to the Collatz conjecture on a school trip. “Take a number, let’s say 3. If it’s odd, you treble it and

## The Dictionary of Mathematical Eponymy: Banach’s Matchbox Problem

Stefan Banach was one of the early 20th century’s most important mathematicians - if you’re at all interested in popular maths, you’ll have heard of the Banach-Tarski paradox; if you’ve done any serious linera algebra, you’ll know about Banach spaces; if you’ve read Cracking Mathematics (available wherever good books are

## The Dictionary of Mathematical Eponymy: Ackermann’s function

For 2019, I'm trying an experiment: every couple of weeks, writing a post about a mathematical object that a) I don't know much about and b) is named after somebody. These posts are a trial run - let me know how you find them! The chief use of the Ackermann