Back to Sign tutorialAIfrontier →
MONOGRAPH COMPANIONPLATE I · EN EDITIONSIGN · SURFACEOLOGY

Surfaces&Signs — an isomorphism between positive geometry and static verification —

Surfaceology reads scattering amplitudes from curves on a 2-dimensional surface.
Sign reads a program's meaning from its pre-execution structure.
Both share one gesture: discard the dynamics, keep only the combinatorial positivity.

PLATE I / III
1400 × 2380
REV. 2026-09-22
POLE A · PHYSICS

Surfaceology

amplitudes as surface combinatorics

Spacetime and Feynman diagrams are dismissed at the outset.
What remains is a punctured disk, non-crossing curves upon it, and their edge-length coordinates uij.
The amplitude arises at once as an integral over the combinatorial polytope carved by u ≥ 0 — no diagram sum, no perturbative expansion.

  • discard: spacetime, loops, gauge
  • keep   : curves on Σg,n
  • read   : from positivity of u ≥ 0
≅
POLE B · LANGUAGE

Sign, compile-time

semantics as tree combinatorics

Runtime state and evaluation order are dismissed at the outset.
What remains is an expression tree, signs + / − / 0 pinned to its nodes, and the combinatorial relations of coproduct ⊙ and product ,.
The program's meaning is read out before execution: 2629 → 2205 instructions, 2 min → a few milliseconds — established by proof, not by run.

  • discard: runtime state, order
  • keep   : expression tree with signs
  • read   : from positivity of terms
§ 01

The Correspondence — ten pairings

one gesture, spoken in two vocabularies
#
Surfaceology vocabulary
≅
Sign vocabulary
shared gesture
01
punctured disk Σ0,n
↔
expression tree (AST) with n leaves
a finite, discrete combinatorial support
02
non-crossing curves γi
↔
subterm identification
unique parse via non-crossing decomposition
03
triangulation T
↔
left-associated evaluation ((a,b),c)
a maximal simplicial refinement
04
mutation (flip)
↔
associativity rewrite (a,b),c ↦ a,(b,c)
transition between covers of one structure
05
u-variables uij
↔
node signs + / − / 0
local coordinate = local index
06
u-equations uij = ∏ (1−ukl)
↔
sign propagation sign(f g) = sign f · sign g
local law enforcing global consistency
07
positivity uij ≥ 0
↔
well-signedness (type soundness)
the admissibility criterion for a configuration
08
co-product of curves
↔
primitive ⊙ (interpunct)
selective composition (either / or)
09
product (concatenation)
↔
comma ,
parallel composition (both)
10
amplitude An = ∫u≥0 Ω
↔
static semantics ⟦e⟧ (fixed before run)
the observable, read without dynamics
§ 02

The Bridge Diagram — from curves to trees

5-point disk triangulation ↔ 5-leaf Sign tree
FIG. 2A · Σ0,5
1 2 3 4 5 u₁₃ u₁₄ u₂₄ u₂₅ solid: current T  ·  dashed: after flip (mutation)
The 5-punctured disk is triangulated by the diagonals u₁₃, u₁₄. A flip to the dashed diagonals is a combinatorial transition between covers of the same structure — not a time evolution.
STATIC READ
⇌
SAME GESTURE
FIG. 2B · SIGN AST
!s ⊙ s ' 0 ⊙ null , x source (5 leaves) , ⊙ , ⊙ !s s 0 null x + − 0 0 + green ⊙ ↔ curve co-product · gold , ↔ concatenation · red ± / 0 ↔ uij boundary
The same 5 vertices become 5 leaves on the Sign side. Green ⊙ nodes are the curve coproduct; gold , nodes are the product; the leaf signs + / − / 0 correspond to the boundary values of uij.

The shared invariant: positivity, read without dynamics.

Surfaceology extracts the scattering amplitude from the positive region of a combinatorial polytope of non-crossing curves on a disk — bypassing spacetime, propagators, and loop summation. Gauge choices and perturbative expansions are not paths that constitute the answer; they are maps that merely cover it.

Sign extracts a program's meaning from the consistent region of combinatorial relations between the signs + / − / 0 pinned on its expression tree — bypassing evaluation order, runtime branching, and garbage collection. Test runs and iterative type-inference are not paths that constitute the answer; they are maps that merely cover it.

What is common to both is the demand itself: the reading is static. Under two vocabularies — physics and language — the same single epistemology is being repeated.

REFS · Arkani-Hamed et al., Surfaceology (2023–24) · Sign language specification (α, 2024–26) · this monograph §§ 4–6, §§ 9–11
Surfaceology · scope
All-loop, all-multiplicity Tr φ³
no Feynman expansion — a single polytope integral
Sign · optimization
2629 → 2205 instructions
16% reduction from static sign propagation alone (measured)
Sign · latency
2 min → < 5 ms
verification completed before execution (same input)
Shared cost
Combinatorial, polynomial
no dynamical simulation is invoked