# Dear Dirichlet, Issue 11

Grant applications, musical media and last-minute Olympics training are the topics readers have sent in to the professor’s postbox this issue

Moonlighting agony uncle Professor Dirichlet answers your personal problems. Want the prof’s help? Send your problems to deardirichlet@chalkdustmagazine.com.

### Dear Dirichlet,

You’ll be pleased to hear I’ve just finished my PhD in abstract algebra, but now I’m stressed about jobs. I need to write this grant application for a big postdoc position studying a set combined with two binary operations, but all I want to do is curl up and read my favourite book: JRR Tolkein’s The Two Towers. What should I do?

— Elven Safety, Birmingham

Dirichlet says:

Congraduations on completing your degree! I know you just want to get to the fun bits, but before you can read The Two Towers, you must complete The Fellowship Application of the Ring. May the Force be with you.

### Dear Dirichlet,

My journey to work is getting worse. I’m sure the Waterloo & City line is down more than it’s up. Do you have any suggestions to send to TfL? For your perusal, I attach a diagram of the route which I have helpfully mocked up in TikZ.

— Marcus McMacDaniel, St Leonard’s Warrior Square

Dirichlet says:

I have performed some analysis on your linear map. First note that since it is embedded in a finite-dimensional sub(way)space, your commute can be represented by $\left(\begin{smallmatrix}0 & 1 \\ -1 & 0\end{smallmatrix}\right)$. Could you save yourself time by just leaving the house and turning clockwise 90° instead? I attempted to shine a beam of light through your map to observe its spectrum, $σ($$)$, but only saw a pair of faint green circles. Alas… sigmal failure.

I wouldn’t start a war of nerves with TfL exclusively, though: I think you would see much the same for any operator.

### Dear Dirichlet,

recently I finished Finnegans Wake, and have been inspired to create a similarly infinitely looping stream of consciousness… but in musical form! I’m thinking of pressing an LP: one track, one side only, which once you press play, would never end! Now I just need to get a few mates together to record it. Would you promote it for us? I ask because

— Rejames! Rejoyce!, Riverrun

Dirichlet says:

An interesting twist! I offer you the best of luck putting together your Möbius band. Although if you tried to play this inevitable trash in my pub (The Boisterous Badger, no entry fee), it’d be your vinyl visit: you’d be Möbius banned.

### Dear Dirichlet,

I enjoyed your advice regarding the Winter Olympics in issue 07. Now that this year’s Games have been postponed, I have time to train to enter them. Any suggestions for events I could enter?

— Emily Al-Jabr, Tokyo

Dirichlet says:
Test your three-dimensional trigonometric skills with the hery–1. Don’t get caught using Cauchy’s residue theorem in the pole vault. Get expanding those brackets of yours by fencing with FOIL! The modern pentagon . W8lifting. 10nis. The fifty-metre 3style. ϱing, χak, ψcling. Scorpion wrestling.

### Dear Dirichlet,

I’m throwing a maths-themed seminar and am looking for some suitable maths-themed biscuits. Perhaps there are some out there which share their names with famous mathematicians?

— Chuck O’Lye, Biarritz

Dirichlet says:

Can’t think of any.

## Heed Professor Dirichlet’s previous advice:

• ### Chalkdust issue 11 puzzle hunt #4

Humbug sets the fourth puzzle. Can you solve it?
• ### Read Issue 11 now!

Space-filling curves, cheating at cards and automated joke generation feature in our latest edition. Plus all your favourite puzzles & columns.
• ### Launch day puzzle hunt

Celebrate the launch of issue 11 by taking part in our puzzle hunt
• ### Prize crossnumber, Issue 11

£100 of MathsGear goodies to be won if you can solve it
• ### What is the shape of you?

Are you a torus? A cone? Ed Spheran? Find out by answering a maximum of five easy questions
• ### Top ten vote issue 11

Vote for your favourite maths-themed day out