Back to the theory of 6/9 patterns

Complete D4 classification

Six square entries: 16 orbits

Every pattern specifies six guaranteed square values and three independent quadrics after E,x,y are eliminated. The atlas separates the canonical system from the level of solution attained for it.

The number 6 is a lower guarantee, not a prohibition on additional square-valued entries. Colors in a card belong to the chosen independent equations; several shades of red denote several arithmetic progressions of squares.

Each card records the strongest proved result. A title followed by an arrow opens the full derivation: an individual surface article for a nonparallel pattern, and the common tfmn, F4+, F7+, and F9+ series for ABDFHJ and ABEFGJ.

Proof of classification completeness and sufficiency of the three quadrics

Proof atlas

All 16 orbits and triples of quadrics for 6/9

Every card contains the original system and three preferred independent relations. Shades of one color distinguish separate conditions of the same mathematical type.

progression of squaresGaussian normx²+2y² normStatus shows the strongest proved result, not isolated examples.
01
ABCDEF

complement: GHJ

red(DEF)yellow(ACDE)blue(BCDE)
{E+x=a2Ex+y=b2Ey=c2Exy=d2E=e2E+x+y=f2\left\{\begin{aligned}E+x&=a^2\\E-x+y&=b^2\\E-y&=c^2\\E-x-y&=d^2\\E&=e^2\\E+x+y&=f^2\end{aligned}\right.
d2+f2=2e2d^2+f^2=2e^2
a2+d2=c2+e2a^2+d^2=c^2+e^2
b2+2c2=d2+2e2b^2+2c^2=d^2+2e^2

One progression and two quadrics on the shared C,D,E block.

Canonical system
02
ABCDEG

complement: FHJ

red(CEG)yellow(ACDE)yellow(ABEG)
{E+x=a2Ex+y=b2Ey=c2Exy=d2E=e2E+y=g2\left\{\begin{aligned}E+x&=a^2\\E-x+y&=b^2\\E-y&=c^2\\E-x-y&=d^2\\E&=e^2\\E+y&=g^2\end{aligned}\right.
c2+g2=2e2c^2+g^2=2e^2
a2+d2=c2+e2a^2+d^2=c^2+e^2
a2+b2=e2+g2a^2+b^2=e^2+g^2

The CEG progression and two independent Gaussian norms.

Canonical system
03
ABCDEH

complement: FGJ

red(CDH)red(BEH)yellow(ACEH)
{E+x=a2Ex+y=b2Ey=c2Exy=d2E=e2E+xy=h2\left\{\begin{aligned}E+x&=a^2\\E-x+y&=b^2\\E-y&=c^2\\E-x-y&=d^2\\E&=e^2\\E+x-y&=h^2\end{aligned}\right.
d2+h2=2c2d^2+h^2=2c^2
b2+h2=2e2b^2+h^2=2e^2
a2+c2=e2+h2a^2+c^2=e^2+h^2

An intersecting red-red-yellow type with shared entry H.

RectangularK3: 2I₄+8I₂; 2≤rank≤4
04
ABCDEJ

complement: FGH

red(BDJ)red(AEJ)yellow(ACDE)
{E+x=a2Ex+y=b2Ey=c2Exy=d2E=e2Ex=j2\left\{\begin{aligned}E+x&=a^2\\E-x+y&=b^2\\E-y&=c^2\\E-x-y&=d^2\\E&=e^2\\E-x&=j^2\end{aligned}\right.
b2+d2=2j2b^2+d^2=2j^2
a2+j2=2e2a^2+j^2=2e^2
a2+d2=c2+e2a^2+d^2=c^2+e^2

Two intersecting progressions and a yellow compatibility relation.

RectangularK3: 2I₄+8I₂; 1≤rank≤4
05
ABCDFG

complement: EHJ

red(BFG)yellow(BCDG)blue(ACFG)
{E+x=a2Ex+y=b2Ey=c2Exy=d2E+x+y=f2E+y=g2\left\{\begin{aligned}E+x&=a^2\\E-x+y&=b^2\\E-y&=c^2\\E-x-y&=d^2\\E+x+y&=f^2\\E+y&=g^2\end{aligned}\right.
b2+f2=2g2b^2+f^2=2g^2
b2+c2=d2+g2b^2+c^2=d^2+g^2
2a2+g2=c2+2f22a^2+g^2=c^2+2f^2

A progression, a Gaussian norm, and an x²+2y² norm without the center.

Canonical system
06
ABCDFH

complement: EGJ

red(AFH)red(CDH)yellow(BDFH)
{E+x=a2Ex+y=b2Ey=c2Exy=d2E+x+y=f2E+xy=h2\left\{\begin{aligned}E+x&=a^2\\E-x+y&=b^2\\E-y&=c^2\\E-x-y&=d^2\\E+x+y&=f^2\\E+x-y&=h^2\end{aligned}\right.
f2+h2=2a2f^2+h^2=2a^2
d2+h2=2c2d^2+h^2=2c^2
b2+h2=d2+f2b^2+h^2=d^2+f^2

An intersecting red-red-yellow type with shared entry H.

RectangularK3: 2I₄+8I₂; 1≤rank≤4
07
ABCDGJ

complement: EFH

red(BDJ)yellow(ACGJ)yellow(BCDG)
{E+x=a2Ex+y=b2Ey=c2Exy=d2E+y=g2Ex=j2\left\{\begin{aligned}E+x&=a^2\\E-x+y&=b^2\\E-y&=c^2\\E-x-y&=d^2\\E+y&=g^2\\E-x&=j^2\end{aligned}\right.
b2+d2=2j2b^2+d^2=2j^2
a2+j2=c2+g2a^2+j^2=c^2+g^2
b2+c2=d2+g2b^2+c^2=d^2+g^2

One progression and two independent Gaussian norms.

Canonical system
08
ABCDHJ

complement: EFG

red(BDJ)red(CDH)yellow(ABHJ)
{E+x=a2Ex+y=b2Ey=c2Exy=d2E+xy=h2Ex=j2\left\{\begin{aligned}E+x&=a^2\\E-x+y&=b^2\\E-y&=c^2\\E-x-y&=d^2\\E+x-y&=h^2\\E-x&=j^2\end{aligned}\right.
b2+d2=2j2b^2+d^2=2j^2
d2+h2=2c2d^2+h^2=2c^2
a2+j2=b2+h2a^2+j^2=b^2+h^2

An intersecting pair of progressions with shared entry D.

RectangularK3: 2I₄+8I₂; 1≤rank≤4
09
ABCEGH

complement: DFJ

red(CEG)red(BEH)yellow(ACEH)
{E+x=a2Ex+y=b2Ey=c2E=e2E+y=g2E+xy=h2\left\{\begin{aligned}E+x&=a^2\\E-x+y&=b^2\\E-y&=c^2\\E&=e^2\\E+y&=g^2\\E+x-y&=h^2\end{aligned}\right.
c2+g2=2e2c^2+g^2=2e^2
b2+h2=2e2b^2+h^2=2e^2
a2+c2=e2+h2a^2+c^2=e^2+h^2

The same K3 quartic as ABCEGJ, with a different cell interpretation.

RectangularK3: 2I₄+8I₂; 2≤rank≤4
10
ABCEGJ

complement: DFH

red(CEG)red(AEJ)yellow(BEGJ)
{E+x=a2Ex+y=b2Ey=c2E=e2E+y=g2Ex=j2\left\{\begin{aligned}E+x&=a^2\\E-x+y&=b^2\\E-y&=c^2\\E&=e^2\\E+y&=g^2\\E-x&=j^2\end{aligned}\right.
c2+g2=2e2c^2+g^2=2e^2
a2+j2=2e2a^2+j^2=2e^2
b2+e2=g2+j2b^2+e^2=g^2+j^2

The same K3 quartic as ABCEGH, with a different cell interpretation.

RectangularK3: 2I₄+8I₂; 2≤rank≤4
11
ABCGHJ

complement: DEF

yellow(ACGJ)yellow(ABHJ)blue(ACHJ)
{E+x=a2Ex+y=b2Ey=c2E+y=g2E+xy=h2Ex=j2\left\{\begin{aligned}E+x&=a^2\\E-x+y&=b^2\\E-y&=c^2\\E+y&=g^2\\E+x-y&=h^2\\E-x&=j^2\end{aligned}\right.
a2+j2=c2+g2a^2+j^2=c^2+g^2
a2+j2=b2+h2a^2+j^2=b^2+h^2
a2+2c2=2h2+j2a^2+2c^2=2h^2+j^2

The unique pattern without a red progression: two Gaussian and one blue norm.

Canonical system
12
ABDEFH

complement: CGJ

red(AFH)red(DEF)red(BEH)
{E+x=a2Ex+y=b2Exy=d2E=e2E+x+y=f2E+xy=h2\left\{\begin{aligned}E+x&=a^2\\E-x+y&=b^2\\E-x-y&=d^2\\E&=e^2\\E+x+y&=f^2\\E+x-y&=h^2\end{aligned}\right.
f2+h2=2a2f^2+h^2=2a^2
d2+f2=2e2d^2+f^2=2e^2
b2+h2=2e2b^2+h^2=2e^2

Three red conditions with two shared centers.

TriangularK3: 4I₄+4I₂; 1≤rank≤2
13
ABDEFJ

complement: CGH

red(BDJ)red(DEF)red(AEJ)
{E+x=a2Ex+y=b2Exy=d2E=e2E+x+y=f2Ex=j2\left\{\begin{aligned}E+x&=a^2\\E-x+y&=b^2\\E-x-y&=d^2\\E&=e^2\\E+x+y&=f^2\\E-x&=j^2\end{aligned}\right.
b2+d2=2j2b^2+d^2=2j^2
d2+f2=2e2d^2+f^2=2e^2
a2+j2=2e2a^2+j^2=2e^2

A different topology of three red conditions.

TriangularK3: 4I₄+4I₂; 1≤rank≤2
14
ABDFHJ

complement: CEG

red(AFH)red(BDJ)yellow(BDFH)
{E+x=a2Ex+y=b2Exy=d2E+x+y=f2E+xy=h2Ex=j2\left\{\begin{aligned}E+x&=a^2\\E-x+y&=b^2\\E-x-y&=d^2\\E+x+y&=f^2\\E+x-y&=h^2\\E-x&=j^2\end{aligned}\right.
f2+h2=2a2f^2+h^2=2a^2
b2+d2=2j2b^2+d^2=2j^2
b2+h2=d2+f2b^2+h^2=d^2+f^2

A parallel red-red-yellow type without the central entry.

Rectangulartfmn parametrization
15
ABEFGH

complement: CDJ

red(AFH)red(BFG)red(BEH)
{E+x=a2Ex+y=b2E=e2E+x+y=f2E+y=g2E+xy=h2\left\{\begin{aligned}E+x&=a^2\\E-x+y&=b^2\\E&=e^2\\E+x+y&=f^2\\E+y&=g^2\\E+x-y&=h^2\end{aligned}\right.
f2+h2=2a2f^2+h^2=2a^2
b2+f2=2g2b^2+f^2=2g^2
b2+h2=2e2b^2+h^2=2e^2

A triangle of three pairwise square means.

TriangularK3: 4I₄+4I₂; 1≤rank≤2
16
ABEFGJ

complement: CDH

red(BFG)red(AEJ)yellow(ABFJ)
{E+x=a2Ex+y=b2E=e2E+x+y=f2E+y=g2Ex=j2\left\{\begin{aligned}E+x&=a^2\\E-x+y&=b^2\\E&=e^2\\E+x+y&=f^2\\E+y&=g^2\\E-x&=j^2\end{aligned}\right.
b2+f2=2g2b^2+f^2=2g^2
a2+j2=2e2a^2+j^2=2e^2
a2+b2=f2+j2a^2+b^2=f^2+j^2

A parallel red-red-yellow type containing the center.

Rectangulartfmn parametrization