Wednesday, January 1, 2025
Square Triangles for Doctor Faustus
Tuesday, December 15, 2015
Square Triangles
Click image for some background.
Exercise: Note that, modulo color-interchange, the set of 15 two-color
patterns above is invariant under the group of six symmetries of the
equilateral triangle. Are there any other such sets of 15 two-color triangular
patterns that are closed as sets , modulo color-interchange, under the six
triangle symmetries and under the 322,560 permutations of the 16
subtriangles induced by actions of the affine group AGL(4,2)
on the 16 subtriangles' centers , given a suitable coordinatization?
Thursday, January 19, 2012
Square Triangles
MathWorld.Wolfram.com has an article titled "Square-Triangle Theorem."
An article of my own, whose HTML title was previously "Triangles are Square," has been retitled accordingly.
Friday, May 20, 2022
Squares to Triangles
Thursday, January 12, 2012
Triangles Are Square
Coming across John H. Conway's 1991*
pinwheel triangle decomposition this morning—
— suggested a review of a triangle decomposition result from 1984:

Figure A
(Click the below image to enlarge.)
The above 1985 note immediately suggests a problem—
What mappings of a square with c 2 congruent parts
to a triangle with c 2 congruent parts are "natural"?**
(In Figure A above, whether the 322,560 natural transformations
of the 16-part square map in any natural way to transformations
of the 16-part triangle is not immediately apparent.)
* Communicated to Charles Radin in January 1991. The Conway
decomposition may, of course, have been discovered much earlier.
** Update of Jan. 18, 2012— For a trial solution to the inverse
problem, see the "Triangles are Square" page at finitegeometry.org.
Saturday, April 25, 2026
Finite Geometry of the Square and Triangle
|
Two facts from figurate geometry . . .
Taken together, these imply that a geometric object
(Of course, for S (5, 8, 24), a hexagonal arrangement of six |
Saturday, September 10, 2022
Orthogonal Latin Triangles
From a 1964 recreational-mathematics essay —
Note that the first two triangle-dissections above are analogous to
mutually orthogonal Latin squares . This implies a connection to
affine transformations within Galois geometry. See triangle graphics
in this journal.
Update of 4:40 AM ET —
Other mystical figures —
"Before time began, there was the Cube."
— Optimus Prime in "Transformers" (Paramount, 2007)
Friday, August 13, 2021
Thursday, February 13, 2020
Square-Triangle Mappings: The Continuous Case
On Feb. 11, Christian Lawson-Perfect posed an interesting question
about mappings between square and triangular grids:
For the same question posed about non -continuous bijections,
see "Triangles are Square."
I posed the related non– continuous question in correspondence in
the 1980's, and later online in 2012. Naturally, I wondered in the
1980's about the continuous question and conformal mappings,
but didn't follow up that line of thought.
Perfect last appeared in this journal on May 20, 2014,
in the HTML title line for the link "offensive."
Sunday, July 15, 2012
Squares Are Triangular
"A figurate number… is a number
that can be represented by
a regular geometrical arrangement
of equally spaced points."
— Eric W. Weisstein at Wolfram MathWorld
For example—
Call a convex polytope P an n-replica if P consists of n
mutually congruent polytopes similar to P packed together.
The square-triangle theorem (or lemma) says that
"Every triangle is an n-replica"
is true if and only if n is a square.
Equivalently,
The positive integer n is a square
if and only if every triangle is an n-replica.
(I.e., squares are triangular.)
This supplies the converse to the saying that
Thursday, March 22, 2012
Square-Triangle Theorem continued
Last night's post described a book by Alexander Soifer
on questions closely related to— and possibly
suggested by— a Miscellanea item and a letter to
the editor in the American Mathematical Monthly ,
June-July issues of 1984 and 1985.
Further search yields a series of three papers by
Michael Beeson on the same questions. These papers are
more mathematically presentable than Soifer's book.
Triangle Tiling I —
http://www.michaelbeeson.com/research/papers/TriangleTiling1.pdf
March 2, 2012
Triangle Tiling II —
http://www.michaelbeeson.com/research/papers/TriangleTiling2.pdf
February 18, 2012
Triangle Tiling III —
http://www.michaelbeeson.com/research/papers/TriangleTiling3.pdf
March 11, 2012
These three recent preprints replace some 2010 drafts not now available.
Here are the abstracts of those drafts—
"Tiling triangle ABC with congruent triangles similar to ABC"
(March 13, 2010),
"Tiling a triangle with congruent triangles"
(July 1, 2010).
Beeson, like Soifer, omits any reference to the "Triangles are square" item
of 1984 and the followup letter of 1985 in the Monthly .
Wednesday, March 21, 2012
Square-Triangle Theorem
(Continued from March 18, 2012)
Found in a search this evening—
How Does One Cut a Triangle? by Alexander Soifer
(Second edition, Springer, 2009. First edition published
by Soifer's Center for Excellence in Mathematical Education,
Colorado Springs, CO, in 1990.)
This book, of xxx + 174 pages, covers questions closely related
to the "square-triangle" result I published in a letter to the
editor of the June-July 1985 American Mathematical Monthly
(Vol. 92, No. 6, p. 443). See Square-Triangle Theorem.
Soifer's four pages of references include neither that letter
nor the Monthly item, "Miscellaneum 129: Triangles are square"
of a year earlier that prompted the letter.
Sunday, March 18, 2012
Square-Triangle Diamond
The diamond shape of yesterday's noon post
is not wholly without mathematical interest …
"Every triangle is an n -replica" is true
if and only if n is a square.

The 16 subdiamonds of the above figure clearly
may be mapped by an affine transformation
to 16 subsquares of a square array.
(See the diamond lattice in Weyl's Symmetry .)
Similarly for any square n , not just 16.
There is a group of 322,560 natural transformations
that permute the centers of the 16 subsquares
in a 16-part square array. The same group may be
viewed as permuting the centers of the 16 subtriangles
in a 16-part triangular array.
(Updated March 29, 2012, to correct wording and add Weyl link.)
Thursday, February 13, 2025
The Exploitation of Symmetry . . . Continues.
Illustration of a July 1980 title by George Mackey —
Exploitation of Symmetry in 1981 . . .
See also the tetrahedra* in my "square triangles" letter
(1985), as well as "Senechal" in this journal.
"And we both know what memories can bring…" Do we?
Saturday, November 2, 2024
For Julia Cicero: Ex Fano Apollinis
Cicero, In Verrem II. 1. 46 —
He reached Delos. There one night he secretly 46 carried off, from the much-revered sanctuary of Apollo, several ancient and beautiful statues, and had them put on board his own transport. Next day, when the inhabitants of Delos saw their sanc- tuary stripped of its treasures, they were much distressed . . . .
Delum venit. Ibi ex fano Apollinis religiosissimo noctu clam sustulit signa pulcherrima atque anti- quissima, eaque in onerariam navem suam conicienda curavit. Postridie cum fanum spoliatum viderent ii
See also "Ex Fano" in this journal.
For more crazed gravitas, vide . . .
Addendum:
The above New Yorker passage is dated Sept. 26, 2024.
Also on that date . . .

Tuesday, May 31, 2022
Tuesday, September 10, 2019
Sunday, April 15, 2018
Colorado Olympiad
Or: Personalities Before Principles
Personalities —
Principles —
This journal on April 28, 2004 at 7:00 AM.
Backstory —
Square Triangles in this journal.
Friday, May 15, 2026
Bar Wars . . . Boogie Night AI
Wednesday, April 29, 2026
The AI in the Pyramid —
Brutalist Verhexung
"Die Philosophie ist ein Kampf gegen die Verhexung
unsres Verstandes durch die Mittel unserer Sprache."
— Wittgenstein, Philosophical Investigations (1953),
Section 109
Google AI Mode, April 28, 2026 —
"An equilateral triangle subdivided into n 2 congruent triangles
has a central sub-triangle if and only if n is a multiple of 3
(n ≡ 0 (mod 3))."
Refutation —

Brutalist Verhexung
Tuesday, April 28, 2026
Saturday, April 25, 2026
The Verhexung Confrontation*
"Die Philosophie ist ein Kampf gegen die Verhexung
unsres Verstandes durch die Mittel unserer Sprache."
— Wittgenstein, Philosophical Investigations (1953),
Section 109
The "Tetragrammaton of Pythagoras" —
"Duck Soup" fans may recall the war between Freedonia and Sylvania.
For some images more in the spirit of Sylvania, see "Triangles Are Square."
* The word "confrontation" was suggested by the previous post.
ABC Art
On the Netflix series "Maniac" —
"The treatment Owen and Annie sign up for promises to fix
its subjects’ brains with just three little pills—A, B, and C—
administered one after another over the span of three days.
The first forces you to relive your trauma;
the second exposes your blind spots; and
the third pill forces a confrontation."
— Kara Weisenstein at vice.com, Sept. 26, 2018, 12:19 PM
|
Two facts from figurate geometry . . .
Taken together, these imply that a geometric object
(Of course, for S (5, 8, 24), a hexagonal arrangement of six |

Monday, April 20, 2026
NotebookLM Report: Grid as Portal
Mapping the Infinite: A Visual Guide
|
|
Primary Transformation Rule |
Description |
|
Permutations of Rows |
Any of the four rows may be swapped or rearranged in any of the 4! possible ways. |
|
Permutations of Columns |
Any of the four columns may be swapped or rearranged in any of the 4! possible ways. |
|
Permutations of Quadrants |
The grid's four 2×2 blocks (quadrants) can be swapped or permuted as independent units. |
The "So What?" of the Diamond Theorem The revelation of Steven Cullinane’s theorem is its absolute Symmetry Invariance. No matter which of the 322,560 scrambles you apply, the resulting image always retains a discernible structure. It is never a random mess. Specifically, every G-image of D exhibits either:
- Ordinary Geometric Symmetry: Standard rotational or reflectional symmetry.
- Color-Interchange Symmetry: A property where the pattern remains identical if you swap all black sections for white and vice versa.
These 2D shuffles are actually the "shadows" of a higher-dimensional origin, acting as a flat projection of a four-dimensional world.
——————————————————————————–
3. Dimensional Collapse: From 3D Cubes to 2D Arrays
To truly "grok" the Diamond Theorem, we must view the 16 cells of the grid as witnesses to 4-dimensional symmetry. The 4×4 grid is a "dimensional collapse" of a tesseract (a 4D hypercube) onto a flat surface.
The Steps of Dimensional Mapping:
- Labeling with Affine 4-Space: We label each cell with a point from the affine 4-space over the finite field GF(2).
- Binary Positioning: Coordinates (0 and 1) are assigned to represent positions across four dimensions.
- The Hypercube Map: The 16 vertices of a tesseract are mapped directly onto the 16 cells of the square array.
The Parallelogram Rule of Vector Addition In this 4×4 space, geometry and algebra become one through the Parallelogram Rule. In a standard 3D space, if you have two vectors u and v, their sum w = u + v forms the diagonal of a parallelogram. On our 4×4 grid, this manifests visually: picking any two "direction" vectors automatically defines a third vertex. This means that vector addition in 4D space is performed directly on the grid; the "sum" of two cells is always another specific cell, maintaining a perfect triangular closure within the array.
This mapping turns a difficult-to-visualize 4D space into a visual "calculator" where geometric intuition replaces complex calculation.
——————————————————————————–
4. The Visual Language of Finite Fields: GF(16) and Binary XOR
The grid functions as a map of the finite field GF(16). Operations here utilize "Binary Addition," better known to computer scientists as the XOR operation (where 1 + 1 = 0).
The Zero-Sum Property and Closure Every pattern in this system can be decomposed into three "line diagrams." When these diagrams (D_1, D_2, D_3) are combined, they follow a strict "Zero-Sum" rule: D_1 + D_2 + D_3 = 0. In finite geometry, this represents the : if you have two points of a line, the third point is "forced" into existence to complete the set. The symmetry of the final pattern is inevitable because the algebra is perfectly balanced.
This visual language reveals the structure of the projective space PG(3,2):
- The 15 Points: There are 15 possible basic line diagrams, representing the 15 points of the projective space.
- The 35 Lines: The 840 distinct images produced by Group G fall into 35 families of patterns. Each family represents a "line" in the projective space—a set of three points that XOR to zero.
These abstract "lines" are not straight paths but families of symmetry, representing physical alignment and orthogonality in a finite world.
——————————————————————————–
5. Advanced Correspondences: Latin Squares and Skew Lines [Table rewritten from NotebookLM version]
One of the most revolutionary aspects of the Diamond Theorem is how it bridges combinatorial puzzles and abstract geometry. Specifically, it provides a dictionary for "seeing" algebraic independence.
Within the 35 families of patterns, we find that exactly six special order-4 Latin squares have orthogonal mates. The theorem shows that the combinatorial "orthogonality" of these squares is actually a geometric property in disguise.
|
Combinatorial Term Orthogonal Latin Squares Superimposed grids showing every ordered pair of symbols exactly once. |
Geometric Translation Skew Lines in PG(3,2) |
The Visual Outcome
Disjoint sets of line |
When a student sees that two patterns are "orthogonal," they are literally looking at skew lines—lines that exist in the same 3D projective space but never meet. Algebraic independence has never been more visible.
——————————————————————————–
6. The Tapestry of Application: From Quilts to Deep Space
The Cullinane Diamond Theorem proves that symmetry is not a decorative choice, but a mathematical inevitability found in everything from folk art to the stars.
- Quilt Design: Ancient artisans unintentionally utilized finite geometry. The theorem explains why traditional quilt blocks (like the "diamond" and "chevron") possess pervasive symmetry—they were tapping into the AGL(4,2) group without knowing it.
- The MOG & M24: The theorem is a visual sister to the Miracle Octad Generator (MOG). The symmetry group G is isomorphic to the octad stabilizer subgroup of the Mathieu group M_{24}, one of the mysterious sporadic simple groups.
- The Leech Lattice: These patterns serve as a visual bridge to the Leech Lattice, the most efficient way to pack spheres in 24 dimensions. The lattice is essentially a "blown-up" version of the Steiner system S(5,8,24) that governs these 4×4 symmetries.
- Coding Theory & Uninterrupted Cuts: The theorem is deeply linked to the Golay code, used by the Voyager probes to send clear images from deep space. Within the "Diamond Ring" of patterns, there exists an ideal of 1024 patterns characterized by "uninterrupted cuts" (where all horizontal or vertical lines remain unbroken). These patterns represent the peak of structural stability used in error-correcting codes.
——————————————————————————–
7. Summary Checklist for the Aspiring Learner
As you gaze upon the next 4×4 pattern you encounter, use this checklist to verify your understanding of the secrets "hidden in plain sight":
- [ ] I understand that the 4×4 grid is a visual map of a 4-dimensional vector space.
- [ ] I recognize that symmetry is preserved because the transformations are governed by the full affine group AGL(4,2).
- [ ] I see that a "line" in this geometry is actually a family of three patterns that XOR to zero.
- [ ] I can visualize the Parallelogram Rule, where adding two positions on the grid "forces" the third into existence.
- [ ] I recognize the 1024 patterns with uninterrupted cuts as the mathematical "ideal" within the diamond ring.
- [ ] I understand that orthogonal Latin squares are simply the visual manifestation of skew lines in projective space.
Keep your eyes open, for the infinite is often mapped onto the smallest of canvases.
Saturday, September 28, 2024
Architectural Singularity
Embedded in the Sept. 26 New Yorker review of Coppola's
Megalopolis is a ghostly transparent pyramidal figure . . .
The pyramidal figure is not unrelated to Scandia.tech —
|
American Mathematical Monthly, Vol. 92, No. 6 LETTERS TO THE EDITOR Material for this department should be prepared exactly the same way as submitted manuscripts (see the inside front cover) and sent to Professor P. R. Halmos, Department of Mathematics, University of Santa Clara, Santa Clara, CA 95053 Editor: Miscellaneum 129 ("Triangles are square," June-July 1984 Monthly ) may have misled many readers. Here is some background on the item. That n2 points fall naturally into a triangular array is a not-quite-obvious fact which may have applications (e.g., to symmetries of Latin-square "k-nets") and seems worth stating more formally. To this end, call a convex polytope P an n-replica if P consists of n mutually congruent polytopes similar to P packed together. Thus, for n ∈ ℕ, (A) An equilateral triangle is an n-replica if and only if n is a square. Does this generalize to tetrahedra, or to other triangles? A regular tetrahedron is not a (23)-replica, but a tetrahedron ABCD with edges AB, BC, and CD equal and mutually orthogonal is an n-replica if and only if n is a cube. Every triangle satisfies the "if" in (A), so, letting T be the set of triangles, one might surmise that (B) ∀ t ∈ T (t is an n-replica if and only if n is a square). This, however, is false. A. J. Schwenk has pointed out that for any m ∈ ℕ, the 30°-60°-90° triangle is a (3m2)-replica, and that a right triangle with legs of integer lengths a and b is an ((a2 + b2)m2)-replica. As Schwenk notes, it does not seem obvious which other values of n can occur in counterexamples to (B). Shifting parentheses to fix (B), we get a "square-triangle" lemma:
(C) (∀ t ∈ T, t is an n-replica) if and only if n is a square.
Steven H. Cullinane
501 Follett Run Road Warren, PA 16365 |
Wednesday, July 31, 2024
My Links — Steven H. Cullinane
Main webpage of record . . .
Encyclopedia of Mathematics https://encyclopediaofmath.org/wiki/Cullinane_diamond_theorem
(A maintainable copy of that webpage was made by the Encyclopedia in 2026 at
https://handwiki.org/wiki/Cullinane_diamond_theorem.)
Supplementary PDF from Jan. 6, 2006 https://encyclopediaofmath.org/images/3/37/Dtheorem.pdf
Originally published in paper version . . .
Computer Graphics and Art, 1978 http://finitegeometry.org/sc/gen/Diamond_Theory_Article.pdf
AMS abstract, 1979: "Symmetry Invariance in a Diamond Ring" https://www.cullinane.design/
American Mathematical Monthly, 1984 and 1985: "Triangles Are Square" http://finitegeometry.org/sc/16/trisquare.html
Personal sites . . .
Primary —
Personal journal http://m759.net/wordpress/
Mathematics website http://finitegeometry.org/sc/
Mathematics Images Gallery http://m759.net/piwigo/index.php?/category/2
Secondary —
Portfoliobox https://cullinane.pb.design/
Substack https://stevenhcullinane.substack.com/
Symmetry Summary https://shc759.wordpress.com
Diamond Theory Cover Structure https://shc7596.wixsite.com/website
3dthis.com https://3dthis.com/profile.htm?owner=Cullinane
Latin Square Structure https://shc7596.wixsite.com/website
SOCIAL:
Pinterest https://www.pinterest.com/stevenhcullinane/ (many mathematics notes)
Flickr https://www.flickr.com/photos/m759/ (backup account for images of mathematics notes)
Bluesky https://bsky.app/profile/m759.bsky.social
Instagram https://www.instagram.com/stevencullinane
TikTok https://www.tiktok.com/@stevenhcullinane
X.com https://x.com/shc759
OTHER:
Replit viewer/download https://replit.com/@m759/View-4x4x4?v=1
dSourceForge download https://sourceforge.net/projects/finitegeometry/
Academia.edu https://stevenhcullinane.academia.edu/
GitHub https://github.com/m759 (finite geometry site download)
Internet Archive: Notes on Groups and Geometry https://archive.org/details/NotesOnGroupsAndGeometry1978-1986/mode/2up
Cited at . . .
The Diamond Theorem and Truchet Tiles http://www.log24.com/log22/220429-Basque-DT-1.pdf
April 2024 UNION article in Spanish featuring the diamond theorem https://union.fespm.es/index.php/UNION/article/view/1608/1214
April 2024 UNION article in English http://log24.com/notes/240923-Ibanez-Torres-on-diamond-theorem-Union-April-2024-in-English.pdf
Cullinane in a 2020 Royal Holloway Ph.D. thesis https://pure.royalholloway.ac.uk/ws/portalfiles/portal/40176912/2020thomsonkphd.pdf
Squares, Chevrons, Pinwheels, and Bach https://www.yumpu.com/en/document/read/36444818/fugue-no-21-elements-of-finite-geometry
Observables programmed presentation of diamond theorem https://observablehq.com/@radames/diamond-theory-symmetry-in-binary-spaces
Josefine Lyche — Plato's Diamond https://web.archive.org/web/20240222064628/http://www.josefinelyche.com/index.php?/selected-exhibitions/platos-diamond/
Josefine Lyche — Diamond Theorem https://web.archive.org/web/20230921122049/http://josefinelyche.com/index.php?/selected-exhibitions/uten-ramme-nye-rom/
Professional sites . . .
Association for Computing Machinery https://member.acm.org/~scullinane
bio.site/cullinane … maintenance at https://biosites.com
ORCID bio page https://orcid.org/0000-0003-1135-419X
Google Scholar https://scholar.google.com/citations?view_op=list_works&hl=en&hl=en&user=NcjmFwQAAAAJ&sortby=pubdate
Academic repositories:
Harvard Dataverse https://dataverse.harvard.edu/dataset.xhtml?persistentId=doi:10.7910/DVN/KHMMVH
Harvard DASH article on PG(3,2) https://dash.harvard.edu/handle/1/37373777
Zenodo website download https://zenodo.org/records/1038121
Zenodo research notes https://zenodo.org/search?q=metadata.creators.person_or_org.name%3A%22Cullinane%2C%20Steven%20H.%22&l=list&p=1&s=10&sort=bestmatch
Figurate Geometry at Open Science Framework (OSF) https://osf.io/47fkd/
arXiv: "The Diamond Theorem" https://arxiv.org/abs/1308.1075
AI reports:
NotebookLM: Diamond Theory https://notebooklm.google.com/notebook/62ad8daa-277e-4fea-a680-9b209883f232?authuser=1
Microsoft Copilot Deep Research https://www.log24.com/log25/2025-08-10-Copilot-Report-Cullinane-Diamond-Theorem.html
Sunday, June 9, 2024
The Lo Shu Triangle (洛書 三角形)
Exercise: Show that Dürer's 1514 "magic" square is an affine automorphism.
For a solution, see other posts now tagged Affine Squares.
Monday, March 11, 2024
Wednesday, February 28, 2024
A Definite School of Thought…
“The Buck Starts Here”
https://theosophy.wiki/en/Jirah_Dewey_Buck —
" Dr. Jirah Dewey Buck (November 20, 1838 – December 13, 1916)
was a physician who worked to establish one of the first Theosophical
lodges in the United States, the Cincinnati Theosophical Society, and
the American Section of the international Theosophical Society in 1886 . . . ."
"Buck was born in Fredonia, New York
on November 20, 1838 . . . .
[He was] 'a recognized leader of a definite school
of Masonic thought and propaganda'."
The above metadata was suggested by an image I happened to see today,
the "Tetragrammaton of Pythagoras" —
"Duck Soup" fans may recall the war between Freedonia and Sylvania.
For some images more in the spirit of Sylvania, see "Triangles Are Square."
“The Buck Starts Here”
Friday, September 22, 2023
Figurate Space
For the purpose of defining figurate geometry , a figurate space might be
loosely described as any space consisting of finitely many congruent figures —
subsets of Euclidean space such as points, line segments, squares,
triangles, hexagons, cubes, etc., — that are permuted by some finite group
acting upon them.
Thus each of the five Platonic solids constructed at the end of Euclid's Elements
is itself a figurate space, considered as a collection of figures — vertices, edges,
faces — seen in the nineteenth century as acted upon by a group of symmetries .
More recently, the 4×6 array of points (or, equivalently, square cells) in the Miracle
Octad Generator of R. T. Curtis is also a figurate space . The relevant group of
symmetries is the large Mathieu group M24 . That group may be viewed as acting
on various subsets of a 24-set… for instance, the 759 octads that are analogous
to the faces of a Platonic solid. The geometry of the 4×6 array was shown by
Curtis to be very helpful in describing these 759 octads.


























