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182 changes: 182 additions & 0 deletions research/permutation-slack-workspace/PROOF.md
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# Inversion-weighted spectator reduction

This contribution is produced by Nick Petalas. Apache-2.0.

This is a scoped algebraic proof. Its finite controls are corroboration,
not a proof of the universal quantifiers or a complete multiplication theorem.

## Statement

Let F be any field, n>=2, and R=A direct-sum S a finite-dimensional scalar
role space, with dim A=w. Work in M_R(F[S_n]). For a nonidentity permutation g
and scalar column u and row v with vu=1, define

G_g(u,v) = I + ([g]-[e])uv.

The inverse is G_(g^-1)(u,v). Consider a nonempty normalized written word

T = G_(g_1)(u_1,v_1) ... G_(g_m)(u_m,v_m) = Q_A direct-sum I_S.

The endpoint equality is coefficientwise in the full group algebra. It
includes arbitrary dirty inputs, every off-diagonal coefficient, and complete
spectator restoration. No restriction to diagonal active endpoints is made.
Put d_i=inv(g_i)>0 and d_*=min_i d_i. Let permutations act on ordered distinct
pairs, let H be the increasing-pair subspace tensored with R, and K the
decreasing-pair subspace. For the represented endpoint set

L = rank(projection_K T restricted_to H).

**Theorem.** A single spectator-only scalar basis change, fixing the original
active coordinates, puts every original paid factor on at most

w + floor((sum_i d_i - L)/d_*)

total roles. Restricting those same factors preserves their labels, order,
rank-one idempotents and full formal endpoint. The retained extra roles remain
arbitrary dirty inputs and are restored. In particular sum_i d_i>=L.

When all labels have inversion count d, the bound is
w+m-ceil(L/d). At d=1 this recovers Brian/JoyboyBrian's #4783 simple-label
bound. The new statement admits non-simple and non-involutive labels, varying
inversion counts, arbitrary symmetric groups, and every scalar field.

The empty word needs no dirty roles and is treated separately. Identity
labels can be deleted before defining d_*. This theorem does not price a label
as inv(g) physical calls; d_i is a geometric quantity used to bound workspace.

## The crossing decomposition

Write U_+ for the span of increasing pairs and U_- for decreasing pairs.
For any permutation h let C be the coordinate intersection U_+ intersect hU_+,
let X be the coordinate complement of C in U_+, and Y the negative coordinate
part of hU_+. Thus

U_+ = C direct-sum X, hU_+ = C direct-sum Y,
dim X = dim Y = inv(h) = d.

This holds because the ordered-pair action is a permutation action. An inversion
is precisely an increasing pair sent to a decreasing one. No involution
assumption is used. Since R=ker(v) direct-sum span(u), the represented gate is
identity on ker(v) and h on span(u). Consequently

G_h H = (R tensor C) direct-sum (ker(v) tensor X)
direct-sum (span(u) tensor Y). (1)

In particular d(H,G_h H)=d, where d(B,C)=dim B-dim(B intersect C) is the
Grassmann distance for subspaces of the same dimension. Also

H intersect G_h H = ker(ell),

where ell:H -> F^d applies v to each X-coordinate. Its quotient in G_h H
has dimension d. Formula (1) is the new replacement for the predecessor's
one-crossing decomposition.

## The local charge

Suppose the current residual P has full formal form P_A0 direct-sum I_S0.
Define phi(P)=rank(projection_K P restricted_to H). Equivalently
phi(P)=d(H,P^-1 H). Put Z=P^-1 H and D=H intersect Z.

Peel a rightmost factor G_g by multiplying P on the right by its inverse.
Set h=g^-1 and Y0=G_(g^-1) H. Invariance of Grassmann distance gives

phi(P G_g^-1) - phi(P)
= dim D - dim(Y0 intersect Z). (2)

Indeed phi(PG_g^-1)=d(H,G_g P^-1 H)=d(G_g^-1 H,P^-1 H).
In (1) use h=g^-1 throughout this local step. Both h and g have
inversion count d.

Write a for the S0 component of u, b for the restriction of v to S0, and
eta=1[a!=0]+1[b!=0]. Then

d eta <= d + phi(P G_g^-1) - phi(P). (3)

To prove this, note that Z contains S0 tensor U_+ and has no negative
spectator component. If b!=0, ell restricted to D has rank exactly d,
because D contains S0 tensor X and b is a nonzero functional there.
Thus dim(D intersect ker ell)=dim D-d.

If a!=0, any nonzero Y-coordinate in (1) has a nonzero negative spectator
component, so cannot lie in Z. Therefore
Y0 intersect Z=D intersect ker ell. If both a,b are nonzero, (2) is exactly
d, proving (3) with eta=2. If a!=0 and b=0, (2) is nonnegative, proving
(3) with eta=1.

If a=0 and b!=0, the quotient of Y0 intersect Z by D intersect ker ell
injects into Y0/(Y0 intersect H), a space of dimension d. Hence its dimension
is at most dim D, so (2) is nonnegative and again eta=1 is charged.
If a=b=0, the distance triangle gives (2)>=-d, completing the four cases.

The nonnegative local slack s=d+phi(PG_g^-1)-phi(P) therefore pays
eta<=s/d<=s/d_* dirty directions. This step is valid for arbitrary invertible
active represented maps. It does not use faithfulness to admit an endpoint.

## Nested splits and the global word

For a vector a in S0 and functional b on S0, choose S0=V direct-sum S1,
with a in V and b annihilating S1. Such a V has dimension at most eta.
If a=b=0 take V=0. If just one is nonzero, retain its vector or a vector
t with b(t)=1, respectively. If both are nonzero and b(a)!=0, take V=span(a)
and S1=ker b. If both are nonzero and b(a)=0, choose b(t)=1 and take
V=span(a,t), with S1 a complement to span(a) in ker b. These constructions
work over every field.

Enlarge A0 to A1=A0 direct-sum V. The peeled factor has u in A1 and v
annihilates S1. Both the old residual and its peeled successor preserve A1
and are identity on S1 in the full formal algebra. Repeat, starting at T
and peeling factors from right to left. The final residual is identity.
All retained V spaces lie inside the original spectator space. Telescoping
the local nonnegative slacks gives

retained_dirty <= sum_i s_i/d_*
= (sum_i d_i + phi(I) - phi(T))/d_*
= (sum_i d_i - L)/d_*.

The retained dimension is an integer, giving the floor in the theorem.
The distance triangle also directly gives sum_i d_i>=L.

Take a basis of the retained V spaces in peeling order, followed by a basis
of the final discarded spectator space. This is one scalar basis of S, with
the original active basis fixed. Let J include the retained role space and
E project onto it along the discarded space. Every original factor satisfies
u_i=J u_i' and v_i=v_i' E, with EJ=I. Thus

v_i' u_i'=1, G_i J=J G_i', E G_i=G_i' E,
G_i = G_i' direct-sum I_discarded.

These identities hold coefficientwise in F[S_n], not just in the ordered-pair
representation. Multiplication gives the original complete endpoint on the
retained roles. Labels, order and every label-dependent tariff are preserved.

## Sharpness and scope

For any nonidentity g with d inversions, take one active axis e0 and two dirty
axes e1,e2. Let u=e0+e1 and v=e0*+e2*, so vu=1. The written word

G_g(e0,e0*) G_g(u,v) G_(g^-1)(u,v)

has endpoint diag([g],1,1), total inversion mass 3d, L=d and d_*=d.
The theorem retains at most two dirty roles. Both are necessary if the actual
factors must survive one spectator-only basis change: their nonzero dirty
image and dirty functional have zero pairing. On a one-dimensional space,
a nonzero vector and functional have nonzero pairing. This proves sharpness
of the coefficient for this reduction, over every field, including a genuinely
non-involutive 3-cycle. The canceling pair makes no endpoint-optimal-workspace
or shortest-word claim.

The result answers #4783's non-simple-label charge question. Brian's nested
splits, positive-slack framework and preserved-factor sharpness mechanism
remain predecessor credit. Ross Richardson #1989 supplies the ordered-pair
inversion cut, following Adam Gall #1941 and Ross Richardson #1966. Credit
Sagar Thakrar #3888, Arham Tahir #2998 and Nick Petalas #2583/#3408 for the
retained weighted-register context. The proof is self-contained and imports
no pending executable or finite-exclusion receipt.

This is a fixed-word algebraic workspace reduction. It gives no physical
basis-conversion algorithm or native tariff, and permits neither nilpotent
couplings, unreturned spectators nor free address operations. Scalar mixing
is normalized into the given rank-one idempotents; augmentation forces any
remaining free scalar endpoint to be identity. Precision, tape, ownership,
hosting, complete supplier admission and all-size multiplication transfer
remain separate obligations. No new kappa is claimed.
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# Dirty workspace from inversion-weighted permutation slack

A fixed formal word with arbitrary nonidentity permutation labels can be
restricted to at most

```text
active roles + floor((sum label inversions - endpoint crossing rank)
/ smallest label inversion count).
```

This is a scoped all-field algebraic proof with exact finite corroboration.
The restriction preserves every original rank-one idempotent, paid label,
written order and full arbitrary-dirty-input endpoint. When every label has
the same inversion count d, the bound is `w+m-ceil(L/d)` total roles.
There is no new kappa or complete multiplication theorem.

This answers the first Open next question in Brian/JoyboyBrian's
[PR #4783](https://github.com/CrocSwap/integer-mult-bounds/pull/4783), read at
`c46cf15df53f3dad2ce59faec9cdc54184e643e5`. That predecessor proves the
simple adjacent S4 case and leaves non-simple labels open. Its local-charge
method, nested spectator splits and fixed-word sharpness mechanism retain
predecessor credit. The new step replaces one crossing by the complete
inversion-sized coordinate crossing space. Non-involutive labels use their
literal inverse when peeling. The theorem covers all symmetric groups and
all scalar fields.

## Exact boundary and result

Let F be any field, `R=A direct-sum S` a finite scalar role space, `dim A=w`,
and `n>=2`. A paid factor in `M_R(F[S_n])` is

```text
G_g(u,v) = I + ([g]-[e])uv, vu=1, g != e.
```

A nonempty normalized word has full formal endpoint `Q_A direct-sum I_S`.
The active block may be non-diagonal. Every spectator input is arbitrary
and must be restored; every off-diagonal formal coefficient is constrained.
Define `d_i=inv(g_i)`, `d_*=min d_i`, and `L` as the endpoint's crossing rank
in the ordered-distinct-pair representation, increasing pairs to decreasing
pairs. Then one spectator-only scalar basis change fixing A supports every
original factor on at most `w+floor((sum d_i-L)/d_*)` roles.

The [proof](PROOF.md) gives the exact crossing decomposition and four-case
local inequality

```text
d_i * (1[dirty image != 0] + 1[dirty functional != 0])
<= d_i + phi(peeled residual) - phi(current residual).
```

Each right-hand side is nonnegative. Explicit nested splits and telescoping
prove the bound; full group-algebra intertwiners prove the retained endpoint.
The ordered-pair representation supplies a necessary geometric charge and
is never used as a full endpoint oracle.

The coefficient is sharp for preserving the given factors. A nonidentity
coordinate call followed by a canceling non-simple gate/inverse pair has
inversion slack `2d` and needs two dirty directions under the stated basis
restriction. Their nonzero image and functional have zero pairing, which
cannot happen on a one-dimensional retained dirty space. This says nothing
about the endpoint's minimum workspace after resynthesis: the pair cancels.

Identity labels can be removed first. The empty word needs no extra roles.
The inversion count is a geometric weight, not an asserted native-call tariff.

## Evidence and reproduction

Python 3.12 and the standard library suffice. From the repository root:

```sh
/Users/nick/git/integer-mult-bounds/.venv/bin/python3.12 -B scripts/research_package.py --package research/permutation-slack-workspace
/Users/nick/git/integer-mult-bounds/.venv/bin/python3.12 -I -W error -O -B research/permutation-slack-workspace/verify.py
/Users/nick/git/integer-mult-bounds/.venv/bin/python3.12 -I -W error -O -B research/permutation-slack-workspace/oracle.py
```

On another machine substitute its CPython 3.12 path. Normal replay writes
nothing. `verify.py --emit /absolute/new/path.json` explicitly generates a
receipt with every package source hash and the recomputed transcript. It
refuses an occupied output path. `--receipt /absolute/path.json` recomputes
and compares every receipt field. Default replay checks the mathematical
invariants directly; no generated output stays in the checkout. The source
hashes authenticate bytes, not mathematical truth or independent authorship.

The primary check covers 5,625 local peels. Every permutation label and
rank-one projector is enumerated within these six finite domains; active
maps are a declared deterministic sample of invertible maps on one active
role's ordered-pair space, not an exhaustive GL census.

| Permutations | Field | Total roles | Active maps per label/projector | Peels |
| --- | --- | ---: | ---: | ---: |
| S2 | F2 | 3 | 4 | 112 |
| S3 | F2 | 3 | 4 | 560 |
| S4 | F2 | 3 | 3 | 1,932 |
| S3 | F3 | 3 | 3 | 1,755 |
| S4 | F3 | 2 | 2 | 552 |
| S5 | F2 | 2 | 1 | 714 |

It also checks 576 literal crossing-space decompositions, four sharpness
words in the full formal algebra, 300 complete regular-action dirty-input
basis columns, and two constructive nested mixed-label compressions over
F2 and F3. The nested words reduce six roles to four by one computed scalar
basis, preserving every factor. Seven controls cover malformed permutations,
nilpotent couplings, unsupported fields, unreturned dirt, forward-for-inverse
substitution, unit crossing undercharge and the one-dimensional sharpness
boundary.

`oracle.py` imports no primary code. It enumerates actual 512-element binary
subspace sets and computes intersection dimensions from their cardinalities.
All 840 cases cover every S3 active permutation, every nonidentity paid S3
label and every rank-one idempotent on three scalar roles. All crossing
lengths 1,2,3 and dirty-component counts 0,1,2 occur. This checks the local
charge without matrix Gaussian elimination or the predicted decomposition.
Both registered normal and optimized modes use explicit runtime checks.

The written proof establishes the quantified theorem. These finite domains
do not establish an arbitrary-word exclusion or audit a predecessor result.

## Scope, sources and credit

Scientific base `624de9dc66858af0945e5f8a0942488d62280d43`, priority revision 7.
[Advance claim](https://github.com/CrocSwap/integer-mult-bounds/discussions/1166#discussioncomment-19133755).
The original card was `formal-interface-lemma`; this is a declared scope
change to an elementary quantified proof of an explicitly open interface
question. The selected source-binding positive control passed. The historical
card command `research_baseline.py` raises `KeyError: 'bit_lower'` against the
current selected certificate schema; neither command is a scientific replay.

`SOURCES.json` pins the catalogue, selected record and merged predecessor
notes as Git provenance. The pending #4783 is an exact external citation,
not an imported executable or a source-history dependency. The proof is
self-contained. No predecessor checker or finite receipt was replayed.

The live overlap helper at 22:17-22:18 UTC on October 22 covered 380 open PRs
and 3,860 Discussion records with complete pagination. Its local sparse scan
covered 69 of 6,319 main notes. Distinctive `git grep origin/main` searches
separately searched main README objects, and live merged/open PR searches
and this account's last-hour claims were checked. No matching non-simple
slack theorem was found in that coverage. Arbitrary diffs, unretained closed
work and unpublished investigations remain outside coverage. This is not a
novelty certificate.

Related open work is #4783, the simple-label slack theorem; #4847, the exact
scalar minimum for a supplied factor list under the same basis restriction;
and #4851, shortest S3 word rigidity. This contribution proves a geometric
slack inequality for a changed label alphabet. It does not extend the scalar
classification or shortest-word result and compares no predecessor numbers.

Credit Brian/JoyboyBrian #4783/#4765, Ross Richardson #1989/#1966,
Adam Gall #1941, Sagar Thakrar #3888, Arham Tahir #2998,
Nick Petalas #2583/#3408 and their retained register-model predecessors.
The elementary Grassmann distance and linear complement arguments are
standard; no literature-priority claim is made.

This contribution is produced by Nick Petalas. Apache-2.0.
Independent human and formal proof-kernel review are unclaimed.

## Limits

This is a fixed-word formal reduction. Native realization, physical scalar
basis conversion, gauge restrictions, source access, ownership, hosting,
precision, tape and complete supplier/outer admission remain unknown here.
They are not zero-cost assumptions. No selected frontier changes.

## Open next questions

- Does a specified changed permutation-label target and paid budget make
this finite-role bound materially reduce a necessary search? First give
its full alphabet and endpoint crossing rank. A candidate with an actual
physical allowance is missing; this package does not justify a large census.
- Can higher-rank scalar idempotents support a corresponding workspace
charge? First derive their exact crossing subspace and split requirement.
The rank-one image/functional argument does not establish that extension.

## Implementation bounds

Both Python files use explicit finite domains. Control flow is
nonrecursive, functions are below 60 lines, and all domains are explicitly
bounded: n<=5, at most six roles, prime fields 2,3,5 and at most 120 group
labels. The largest regular-action fixture is 120 by 120. The nested split
enumerates at most 3^5 scalar candidates; the independent oracle holds
512-element sets in an 18-dimensional binary space. Python and standard-library
allocations are bounded by these finite domains. There is no dynamic code
generation or external process. Registered normal and optimized replays
treat warnings as errors.
30 changes: 30 additions & 0 deletions research/permutation-slack-workspace/SOURCES.json
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