Michael Kinyon
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profkinyon.bsky.social
Michael Kinyon
@profkinyon.bsky.social
1.5K followers 720 following 970 posts
Mathematics professor at the University of Denver. Quasigroups, Semigroups, Automated Deduction. He/Him. Occasionally drop in at Mathstodon, but not as much as I used to.
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profkinyon.bsky.social
Poof by (electrostatic) induction
Blue-eyed cat whose hair is standing up in all directions because of static electricity
February 7, 2026 at 6:24 PM
profkinyon.bsky.social
Nah
Front cover of the original 2016 edition of the book "Are Numbers Real?" by Brian Clegg, subtitled "The Uncanny Relationship of Mathematics and the Physical World". There is also a review blurb at the bottom of the cover; I will spare you and myself from that.
February 3, 2026 at 10:15 PM
profkinyon.bsky.social
The associate dean just sent around a message asking if anyone still uses clickers in classrooms. My brain immediately went to one particular kind of clicker, briefly wondering how anyone would use one in a mathematics class.
An image of a clicker from _The Last of Us_ games. A clicker is a particular type of infected enemy in the game. They find their way by echolocation, hence their name.
January 29, 2026 at 11:08 PM
profkinyon.bsky.social
Elmo from Sesame Street saying "Rocco's just a rock!"
January 28, 2026 at 10:44 PM
profkinyon.bsky.social
I'll let someone else write verses for analysis, topology, etc.
A Math Major's Lament Groups and rings and finite fields The dizzy dancing way I feel When I consider prime ideals Algebra seems like play But now the term is almost done I'll go outside and see the sun And forget all the math I've done It will all drift away I've looked at math from both sides now Compute and prove But still somehow There is no theorem I recall I really don't know math at all
January 27, 2026 at 12:40 AM
profkinyon.bsky.social
Neugebauer on the purpose of historical studies
I do not consider it as the goal of historical writing to condense the complexity of historical processes into some kind of ``digest" or ``synthesis". On the contrary, I see the main purpose of historical studies in the unfolding of the stupendous wealth of phenomena which are connected with any phase of human history and thus to counteract the natural tendency toward oversimplification and philosophical constructions which are the faithful companions of ignorance. -- Otto Neugebauer, \emph{The Exact Sciences in Antiquity}, 2nd ed., Appendix II, {\S}84
January 26, 2026 at 6:58 PM
profkinyon.bsky.social
A parody of Michaelangelo's "Creation of Adam" where Adam is holding a coffee pot and pouring coffee into a cup held by God.
January 5, 2026 at 8:33 PM
profkinyon.bsky.social
I really wanted a French monic baguette, but they were all out
A piece of a receipt that says "French Epi Baguette"
December 25, 2025 at 4:46 PM
profkinyon.bsky.social
For the homologically minded, another Elf on a Shelf thing.
(attn @courtneygibbons.phd )
An Introduction to Homological Algebra by Charles Weibel sitting on top of the New English Bible on top of a red tablecloth with a floral pattern
December 18, 2025 at 9:16 PM
profkinyon.bsky.social
You've heard of Elf on a Shelf. Now get ready for
A golden shield with "GF(p^n)" in the center of it in black
December 18, 2025 at 4:42 AM
profkinyon.bsky.social
What I've learned from AI is that if you are going to be wrong, do so with an authoritative tone.
search prompt: centralizer of an element of a symmetric group snippet of response: Example: g = (1,2)(3,4,5) in S_5 * Cycle Type: 2^1 3^1 (one 2-cycle, one 3-cycle) * Z Factors: Z_1 (for the single 2-cycle) x Z_1 (for the single 3-cycle) * S factors: S_1 (for the single 2-cycle) x S_1 (for the single 3-cycle) * Result: C_{S_5}(g)\equiv Z_1 x Z_1 x S_1 x S_1 = {e}, the trivial group (only the identity) because there are no cycles to permute or power. Example: g = (1,2)(3,4) in S_4 * Cycle Type: 2^2 (two 2-cycles) * Z Factors: Z_2 (for the two 2-cycle, think powers of (1,2) and (3,4) * S factors: S_2 (permuting the two 2-cycles, e.g., swapping (1,2) and (3,4)) * Result: C_{S_4}(g)\equiv Z_2 x S_2 (order 2x2=4), which includes e,(1,2),(3,4),(1,2)(3,4) and elements like (1,3)(2,4)
December 17, 2025 at 10:46 PM
profkinyon.bsky.social
One Ring to rule them all,
One Ring to find them,
One Ring to bring them all and in the darkness bind them
\[ \mathbb{Z}[x_1,\ldots,x_n] \]
December 16, 2025 at 9:56 PM
profkinyon.bsky.social
Twins
A unbelievably handsome man with unkempt silver hair and glasses, next to a merle Australian shepherd
December 14, 2025 at 8:40 PM
profkinyon.bsky.social
Universal horror
Picture of classic Universal Studios monsters: the Mummy, the Invisible Man, Dracula, Creature from the Black Lagoon, the Phantom of the Opera, Frankenstein's monster, the Bride of Frankenstein, the Wolfman. On Dracula's chest, there is an upside down A.
December 12, 2025 at 8:20 PM
profkinyon.bsky.social
Existential horror
Pennywise with a backwards E on his forehead
December 12, 2025 at 8:05 PM
profkinyon.bsky.social
Brazil, where hearts were entertaining June
We stood beneath an amber moon
And softly murmured "someday soon."
Snippet of a google search The question was: is i^i real Google's response (under "All", not the AI's response): (i^i) Brazil real = 0.2.7879576 Brazil reais
December 12, 2025 at 3:42 AM
profkinyon.bsky.social
I hope my coauthor shares my optimism.
Abstract. I think this idea will work.
November 22, 2025 at 7:02 PM
profkinyon.bsky.social
skircle versus skycle
Image generated by skircle.me consisting of the avatars of those with whom I have had some interaction. It has some overlap with the skycle version, but they are not identical. Image generated by skycle.app consisting of the avatars of those with whom I have had some interaction. It has some overlap with the skircle version, but they are not identical.
October 5, 2025 at 4:58 PM
profkinyon.bsky.social
One of these things is not like the others, WolframAlpha
(In response to "plot arcsec(|x|)") Related Queries plot ln|sec^(-1)(abs(x))| plot 1/sec^(-1)(abs(x)) invert colors image of sec^(-1)(abs(x)) how many people die every day vs how many people are born every day series sec^(-1)(abs(x))
September 8, 2025 at 3:18 PM
profkinyon.bsky.social
I just hope it's also injectivtive so then it would be bijectivtive.

(I probably made this typo, but I'm still going to blame my coauthor.)
Hence $\phi$ is surjectivtive [sic]
June 21, 2025 at 3:58 PM
profkinyon.bsky.social
It's also fun to discuss nonconvex quadrilaterals. Showing them to students and pointing out that they still satisfy the definition of quadrilateral can be mind opening for them. We had an especially good discussion of how one precisely defines "convex".
A nonconvex quadrilateral which roughly has a V-shape. (Created with GeoGebra)
June 9, 2025 at 11:39 PM
profkinyon.bsky.social
If you're the type of mathematics teacher who likes to give exercises requiring exact values of trig functions, but is bored with the old 30°-45°-60° grind, then the Ailles rectangle may be for you!

(Seriously, this thing is why I can write down sin(15°), cos(75°) etc without using identities.)
The Ailles rectangle, a drawing of a rectangle with a 45°-45°-90° triangle inscribed in it. All sides are labeled with their lengths. Besides the "usual" values of trig functions, one can see the values of, for example, sin(15°) just by taking ratios. For more information, see: https://en.wikipedia.org/wiki/Ailles_rectangle
June 4, 2025 at 8:14 PM
profkinyon.bsky.social
One reason my back often hurts is that someone won't allow me to push my chair closer to my desk
A top view of my blue merle Australian shepherd Rusalka sleeping on the floor in front of my chair
May 31, 2025 at 1:01 AM
profkinyon.bsky.social
My students have accused me of having boring title slides so here is what I am using today.
Title: Ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn MATH 3400 29 May 2025
May 29, 2025 at 4:39 PM
profkinyon.bsky.social
"If you like, it is magic."
At this point, I can just hear someone asking, ``What is the geometrical significance of the cross-ratio?'' ... I must say frankly that I cannot visualize a cross-ratio geometrically. If you like, it is magic.... You might say it was a triumph of algebra to invent this quantity that turns out to be so valuable and could not be imagined geometrically. Or if you are a geometer at heart, you may say that it is an invention of the devil and hate it all your life. -- Robin Hartshorne, Geometry: Euclid and Beyond (2000), p.341.
May 27, 2025 at 6:43 PM