Ever since my accidental ‘discovery’ of the word CEILIDH written on a numb3rs blackboard, I keep an eye on their blackboards whenever I watch a new episode, and try to detect terms I might know. Here’s todays screen-shot

I had to choose one frame from a minute long shot (the ‘link’ on the left hand side is more recognizable in other frames). Anyway, here’s what I thought to recognize : a link, a quaternion-algebra over a number field,

to be precise, and a in it. So did someone construct link-invariants from maximal orders in quaternion algebras? I surely didn’t know, but when in doubt there is always… google. I searched for ‘link invariant quaternion algebra maximal order’ and the third hit on page 2 gave me a pdf-file of a paper which seemed to have the relevant terms in it.

The paper is Automorphic forms and rational homology 3–spheres by Frank Calegari and Nathan Dunfield. Bingo! Their first figure is the ‘link’ drawn on the blackboard

which actually turns out to be a graph… This couldn’t be a coincidence, so as in the ceilidh-story, there had to be a connection with one of the authors. ‘Calegari+numb3rs’ didnt look promising but ‘Dunfield+numb3rs’ returned the hit Crime and Computation from CalTech News.

Krumholtz’s star turn as a math genius belies his dismal record as an algebra student. He explained that in preparation for his role he hung around Caltech last fall, “wandering the hallways and campus for two to three weeks,” to soak up the academic ambiance. To plumb character motivation he talked to a real-life youthful math guy, Caltech’s 30-year-old professor Dunfield.
In a phone interview shortly after the show’s television debut Dunfield recalled spending about an hour with Krumholtz, who plays 29-year-old Charlie. “He wanted to know what it’s like to do mathematics and work in academia, what types of things his character would likely be concerned about, like tenure or other issues.”
The professor, who was so un-starstruck that he hadn’t even made a point of watching the premiere, added, “He wanted to know, why would somebody choose to become a mathematics professor. Would they have to love math?” What was his response? The professor said he does not recall.

I couldn’t believe my eyes. I was watching an episode of numb3rs, ‘undercurrents’ to be precise, and there it was, circled in the middle of the blackboard, CEILIDH, together with some of the key-exchange maps around it…

Only, the plot doesn’t involve any tori-crypto… okay, there is an I-Ching-coded-tattoo which turns out to be a telephone number, but that’s all. Still, this couldn’t just be a coincidence. Googling for ‘ ceilidh+numbers‘ gives as top hit the pdf-file of an article Alice in NUMB3Rland written by … Alice Silverberg (of the Rubin-Silverberg paper starting tori-cryptography). Alice turns out to be one of the unpaid consultants to the series. The 2-page article gives some insight into how ’some math’ gets into the script

Typically, Andy emails a draft of the script to the consultants. The FBI plot is already in place, and the writers want mathematics to go with it. The placeholder “math” in the draft is often nonsense or jargon; the sort of things people with no mathematical background might find by Googling, and think was real math. Since there’s often no mathematics that makes sense in those parts of the script, the best the consultants can do is replace jargon that makes us cringe a lot with jargon that makes us cringe a little.
From then on, it’s the Telephone Game. The consultants email Andy our suggestions (”replace ‘our discrete universes’ with ‘our disjoint universes’”; “replace the nonsensical ‘we’ve tried everything -a full frequency analysis, a Vignere deconstruction- we even checked for a Lucas sequence’ with the slightly less nonsensical ‘It’s much too short to try any cryptanalysis on. If it were longer we could try frequency analyses, or try to guess what kind of cryptosystem it is and use a specialized technique. For example, if it were a long enough Vigenere cipher we could try a Kasiski test or an index-of-coincidence analysis’). Andy chooses about a quarter of my sugges- tions and forwards his interpretation of them to the writers and producers. The script gets changed, and then the actors ad lib something completely dif- ferent (’disjointed universes’: cute, but loses the mathematical allusion; ‘Kasiski exam’ : I didn’t mean that kind of ‘test’).

She ends her article with :

I have mixed feelings about NUMB3RS. I still have concerns about the violence, the depiction of women, and the pretense that the math is accurate. However, if NUMB3RS could interest people in the power of mathematics enough for society to greater value and support mathematics teaching, learning, and research, and motivate more students to learnthat would be a positive step.

Further, there is a whole blog dedicated to some of the maths featuring in NUMB3RS, the numb3rs blog. And it was the first time I had to take a screenshot of a DVD, something usually off limits to the grab.app, but there is a simple hack to do it…