Scale-Shift and FFT over Finite Holographic Substrate

The fractional Fourier transform and the reversible scale-shift, or zoom, are exhibited as two facets of one finite cyclic rotation in representation space, exact over the arithmetic symmetry shells defined over finite fields. The shells are holographic in a definite encoding sense: the capacity $\kap$ is the primary datum, the prime cardinality $\p=4\kap+1$ and the $4\kap$-step meridian cycle are derived from it, and the full rotation group of the $\p^{2}$-point phase plane is exactly this cycle, realized on a state space of dimension $\p$, the square root of the plane’s count. Three results share the shell’s meridian cycle.

Preprint: preprints202606.0127.v1. Validation notebook: Open in Colab (36/36 checks passing).

The paper’s dependency structure is collected here as its checklist: one predicate per row, one status tag per row, the source column naming the body statement and, for machine-verified rows, the check identifiers of the validation package (the package’s records cite these rows in return). The blocks follow the body: A the inputs, B the shell and its Fourier operator (Sections 34), C the fractional family (Section 5), D the representation domains and the coordinate-side zoom (Sections 67), E the Weil dictionary and the operator-level comparison (Section 8), F the cyclotomic observer readout (Section 9.1), V the machine verification, O the open front. Every row of blocks B–E is exact finite-field arithmetic; the floating-point figures of block F are declared [approx] and the local scale chart of D3 and D5 is a continuum reading of a finite object, declared [chart], as in the body. The corpus master ledger carries B5, C3 and D4 under its row 00:C2, B2 under its row 00:C14, and C9 as the transform-layer content of its row 00:C7.

Tags

I
Import. A standard result, a corpus result, or a convention used here without reproof.
D
Definition. A naming, a declared dictionary, or a set-up move, carrying no empirical content.
T
Theorem. Derived within this paper from the rows above it and machine-verified in exact arithmetic by the named witness, or observed numerically and reproduced by it to the stated tolerance.
O
Open. Genuinely unresolved.
#DescriptionStatusSource
A. Inputs: imported, not derived here
A1p06001The framed substrate: the Subject $\Fp(\chron;0,1,\gen)$ with $\p=4\kap+1$, its register $\pi=2\kap$, $\im=-\gen^{\kap}=\gen^{-\kap}$, $e=\gen^{\im}$; the frame-relative labels and the atlas of presentations $\gen\mapsto\gen^{u}$; time as scale-dilation, the generator as the observer’s own advance.I
A2p06002The Weil representation $\omega_\p$ of $\SL(2,\Fp)$ and its Schrödinger model, the finite Fourier transform representing the rotation $w$, the finite harmonic oscillator; the scalar convention $\omega_\p(w)^{2}=\omega_\p(-I)$, $\omega_\p(w)^{4}=I$.I
[Weil 1964; Gurevich & Hadani 2006; Gurevich et al. 2008]
A3p06003The classical evaluation of the twisted quadratic Gauss sum for $4\mid n$, $\sum_k\zeta_n^{uk^{2}}=\bigl(\tfrac{\kap}{u}\bigr)(1\pm i)\sqrt n$; the eigenvalue quartet of prime-modulus number-theoretic transforms; the multiplicity counts of the discrete Fourier eigenvalues.I
[Berndt et al. 1998; Birtwistle 1982; McClellan & Parks 1972]
A4p06004The entropic uncertainty relation for a pair of bases, $H_{B}+H_{B'}\ge-2\log c$, $c$ the maximal overlap, $c=n^{-1/2}$ for mutually unbiased bases, saturated by basis-localized states.I
A5p06005The framed-rational zoom: the grids $G_n$ and their $(\p-1)$-periodicity $G_{n+(\p-1)}=G_n$, the meridian shift $m\mapsto m-1$ as the refinement step.I
[Akhtman 2025, §4.3, Lemma 2]
A6p06006The measurement layer: probabilities are structural weights of the cyclotomic stratum, the finite-field module carries no Born magnitude, and the readout is an observer-side declaration; the shell dynamics a bijection, entropy attaching to the readout.I
[Akhtman & Voether 2026; Akhtman 2025]
A7p06007The continuum fractional Fourier transform and the finite constructions the family is separated from: the eigenbasis and matrix-function transforms, the harmonic-oscillator propagator reading.I
[Namias 1980; Ozaktas et al. 2001; Lima & Campello de Souza 2012; Pei et al. 2011; Lima et al. 2017]
B. The shell: the frame datum and the Fourier operator
B1p06008Shell data, capacity-first: $\kap$ primary, $\p=4\kap+1$, the meridian cycle $\Phit=\Z_{4\kap}$, the oriented quarter-turn $\im=-\gen^{\kap}$ (clockwise phase convention), $\pi=2\kap$, $e=\gen^{\im}$; the meridians $M_s=\{a\gen^{s}:a\in I_\p\}$; the six shells of Table 1 with their generators and quarter-turns.D
§ 3, (3.1), (3.2); A1
1/1
B2p06009The Euler identity is a property of the chart class: $e^{\im\pi}=\gen^{2\kap(\im\bmod2)}\equiv-1$ exactly when the quarter-turn residue is odd; the conjugate reframing $(\gen,\im)\mapsto(\gen^{-1},-\im)$ toggles the parity, so one member of each conjugate pair carries it; on $\F_{13}(\chron;0,1,2)$, $\im=5$ and $6^{6}=-1$. Every primitive frame of the six shells.T
§ 3; A2
1/1
master: 00:C14
B3p06010Chart covariance: under $\gen'=\gen^{u}$, $u\in\Zp^{\times}$, the quarter-turn name flips exactly on $u\equiv3\pmod4$ and the exponential-unit name moves already at $u\equiv1\pmod4$ whenever $\im(u-1)\not\equiv0\pmod{4\kap}$ ($\p=13$, $u=5$: $e'=2\neq6$); the registered objects (C3, C4, C9, F3) are invariant.T
Rem. 3.2; A3
1/1
B4p06011The shell Fourier matrix $\Wt_{kj}=\gen^{jk}$ on $\Vt=\Fp^{\Phit}$, the reversal $J$, the normalized shell Fourier operator $\Ft=\im\Wt$.D
(4.2), (4.1), (4.3)
B5p06012$\Wt^{2}=-J$, $\Ft^{2}=J$, $\Ft^{4}=I$: the normalized operator generates the four-cycle, on the six shells of Table 1.T
Lem. 4.2, Prop. 4.5; A4
1/1
master: 00:C2
B6p06013The normalization is the unitary constant read in the field: $1/n\equiv-1$, its square roots in $\Fp$ are exactly $\pm\im$, and $(c\Wt)^{2}=J$ if and only if $c=\pm\im$.T
Rem. 4.4; A5
1/1
B7p06014$\Wt J=J\Wt$, hence $\Ft J=J\Ft$; $\Vt=V^{+}\oplus V^{-}$ with $\dim V^{+}=2\kap+1$, $\dim V^{-}=2\kap-1$.T
Lem. 5.5; A6
1/1
C. The fractional family
C1p06015The projectors $\Pi_\ell=\tfrac14\sum_{r=0}^{3}\im^{-\ell r}\Ft^{r}$ and the principal framed character lift $\Ft^{[s]}=\sum_\ell\gen^{-\ell s}\Pi_\ell$, $s\in\Phit$: the refinement base is the inverse generator, $(\gen^{-1})^{\kap}=\im$, each projector’s character the $\ell$-th power of the meridian phase $z_s=\gen^{-s}$.D
(5.2), (5.3), Rem. 5.3
C2p06016$\Pi_\ell^{2}=\Pi_\ell$, $\Pi_\ell\Pi_m=0$ for $\ell\neq m$, $\sum_\ell\Pi_\ell=I$, $\Ft\Pi_\ell=\im^{\ell}\Pi_\ell$.T
Lem. 5.1; B1
1/1
C3p06017The exact finite-field FrFT: $s\mapsto\Ft^{[s]}$ is a representation of $\Phit$, $\Ft^{[s+r]}=\Ft^{[s]}\Ft^{[r]}$ on every pair of the six shells, with the cardinal values $\Ft^{[0]}=I$, $\Ft^{[\kap]}=\Ft$, $\Ft^{[2\kap]}=J$, $\Ft^{[3\kap]}=\Ft^{-1}$, and $(\Ft^{[1]})^{\kap}=\Ft$.T
Thm. 5.4; B2, B3
2/2
master: 00:C2
C4p06018Faithfulness: $s\mapsto\Ft^{[s]}$ is injective on $\Z_{4\kap}$ for every $\kap\ge1$; at $\p=5$ the surviving odd projector carries the faithful character.T
Thm. 5.9; B4
1/1
C5p06019The multiplicities $m_\ell=\operatorname{rank}\Pi_\ell=\dim\ker(\Ft-\im^{\ell}I)$: $m_0+m_2=2\kap+1$, $m_1+m_3=2\kap-1$; $m_0,m_2\ge1$; $m_1,m_3\ge1$ for $\kap\ge2$; at $\p=5$ exactly one of $\Pi_1,\Pi_3$ vanishes.T
Lem. 5.6; B5
1/1
C6p06020Multiplicities are chart data: the vertex relabelling $m\mapsto um$ carries $\Ft(\gen)$ to $\Ft(\gen^{u^{2}})$ by a coordinate permutation; at $\p=13$ the frames $\gen=2$ and $\gen=6$ give $(3,3,4,2)$ and $(4,2,3,3)$, traces $4$ and $9$.T
Rem. 5.7; B6
1/1
C7p06021The multiplicity dichotomy: $G=\sum_{k}\gen^{k^{2}}=\varepsilon(1+\im)$; the tuple is $(\kap,\kap,\kap+1,\kap-1)$ for $\varepsilon=+1$ and $(\kap+1,\kap-1,\kap,\kap)$ for $\varepsilon=-1$; $\varepsilon(\gen^{-1})=-\varepsilon(\gen)$, $\varepsilon(\gen^{u})=\bigl(\tfrac{\kap}{u}\bigr)\varepsilon(\gen)$ for $u\equiv1\pmod4$, the two classes equally populated; the proof’s identities $GG^{*}=-2$, $G^{2}=2\im$, $\operatorname{Tr}\Ft=\im G$, $\operatorname{Tr}\Ft^{2}=2$, $\operatorname{Tr}\Ft^{3}=\im G^{*}$. Exact on the $38$ primitive frames of $\p\in\{5,13,17,29,37\}$ and the $16$ of $\p=41$.T
Thm. 5.8; B7, B8
2/2
C8p06022Classification: every exponent lift $a_\ell\equiv\ell\pmod4$ is additive with the same cardinal skeleton; a family canonical in the chart $\gen^{u}$ with $u^{2}\not\equiv1\pmod{4\kap}$ does not commute with $\Ft$ ($\p=29$, $u=5$, and every such chart of the six shells); the principal lift is the unique power-tower member.T
Rem. 5.3; B9
1/1
C9p06023The conjugate reframing $(\gen,\im)\mapsto(\gen^{-1},-\im)$: exactly $\Ft'=-\Ft^{-1}$ and $\Pi'_\ell=\Pi_{\ell+2}$; the operator relations, cardinal values, additivity and faithfulness hold on the conjugate frame, and its multiplicity tuple is the other pattern of C7.T
Rem. 3.2, Thm. 5.8; B10
1/1
master: 00:C7
D. Representation domains and the coordinate-side zoom
D1p06024The meridional representation domain $D_s=(\Vt,\mathcal B_s)$, $\mathcal B_s=\Ft^{[s]}\mathcal B_0$, every $\Ft^{[s]}$ invertible; the cardinal domains spatial, spectral, parity, inverse-spectral.D
Def. 6.1, Cor. 6.2; C1
1/1
D2p06025The $4\kap$ framed domains are pairwise distinct; read as unordered measurement bases $B_{s+2\kap}=B_s$, since $\Ft^{[s+2\kap]}=\Ft^{[s]}J$ and $J$ permutes the standard basis, and the cycle carries exactly $2\kap$ of them.T
Cor. 6.3, Rem. 6.4; C2, C3
2/2
D3p06026The meridian-step interval $I_\p=\{0,1,\dots,\pi\}$, the meridian-scale map $S_r(x)=\gen^{r}x$, and the local scale chart $\gen\mapsto\lambda>1$ reading the effective step $\gen^{m}$ as $\lambda^{m}$ [chart].D
(7.1), Def. 7.1, Def. 7.5
D4p06027Meridian-scale covariance: $S_r(M_m)=M_{m+r}$ for every $(m,r)$, as ordered lists; consecutive entries of $M_m$ differ by the effective step $\gen^{m}$; $S_{r+(\p-1)}=S_r$, the periodicity of A5 in meridian form.T
Prop. 7.2, Cor. 7.4, Rem. 7.3; C4, C5
2/2
master: 00:C2
D5p06028Meridian zoom [chart]: $M_m$ reads the meridian-coordinate vector at step $\lambda^{\tilde m}$, the forward shift zoom-out and the inverse shift zoom-in, the seam an aliasing return; at $\p=13$, $\gen=2$ the ladder $M_0,\dots,M_3$ at steps $1,2,4,8$, unwrapped within $w\gen^{r}<\p$ ($w=\pi=6$: $r\le1$) and wrapping from $M_2$.T
Thm. 7.6, Ex. 7.8, Rem. 7.9; C6
1/1
D6p06029Scope of the unification: the representation-side rotation and the coordinate-side scale shift act on carriers of different dimension and are not equal as operators; they share the index group $\Phit$ and the cardinal labels, and the operator-level relation is E5E7.D
Rem. 7.9
E. The Weil dictionary and the operator-level comparison
E1p06030The Weil-side data: $z_s=\gen^{-s}$, $c_s=(z_s+z_s^{-1})/2$, $d_s=(z_s-z_s^{-1})/(2\im)$, the rotation $R_s$; the pulled-back family $\operatorname{FrFT}^{\rm Weil}_\kap(s)=\omega_\p(R_s)$; cardinal Weil correspondence of two families.D
(8.1)–(8.3), (8.5), Def. 8.4
E2p06031$R_s\in SO(2,\Fp)$, and $s\mapsto R_s$ is an isomorphism $\Phit\simeq SO(2,\Fp)$ with $|SO(2,\Fp)|=\p-1=4\kap$: the full rotation group of the $\p^{2}$-point plane is the meridian cycle.T
Lem. 8.1, Prop. 8.2; D1, D2
2/2
E3p06032The cardinal-skeleton dictionary $M_s\leftrightarrow s\leftrightarrow z_s\leftrightarrow R_s$ with $R_0=I$, $R_\kap=w$, $R_{2\kap}=-I$, $R_{3\kap}=w^{-1}$ (the $R_\kap$ column of Table 1), $z_\kap=\im$; the FRC-native and Weil families stand in cardinal Weil correspondence, the Weil side by the normalization of A2.T
Thm. 8.5; D3
1/1
E4p06033Scope and reading of the dictionary: agreement on the four cardinal indices only, the two families acting on spaces of different dimension over different coefficient rings; the holographic reading, the rotation symmetry of the $\p^{2}$-point plane carried by a cycle of the size of its square root, the state side of dimension $\p$.D
Rem. 8.6, Rem. 8.7
E5p06034Spectral obstruction: the exponent shift $\sigma$ has the $4\kap$ simple eigenvalues $\Fpx$, every $\Ft^{[s]}$ at most four; for $\kap\ge2$ the cyclic groups $\langle\sigma\rangle$ and $\langle\Ft^{[1]}\rangle$ are not conjugate.T
Prop. 8.8; D4
1/1
E6p06035Common character sector: on $E_1=\operatorname{im}\Pi_1\neq0$ ($\kap\ge2$) $\Ft^{[s]}=\gen^{-s}I$, the intertwiner $\Ft^{[s]}T_v=T_vS_{-s}$ on every $x\in\Fp$ and $s$, and $R_s(1,-\im)^{\mathsf T}=\gen^{-s}(1,-\im)^{\mathsf T}$.T
Prop. 8.9; D5
1/1
E7p06036Cardinal Heisenberg covariance: $\Ft\sigma\Ft^{-1}=D_1$, $\Ft D_1\Ft^{-1}=\sigma^{-1}$; $\Ft^{r}\sigma=\sigma_r\Ft^{r}$ with $(\sigma,D_1,\sigma^{-1},D_1^{-1})$; the expansion (8.7); $\Ft^{[s]}\sigma\Ft^{[s]-1}$ monomial exactly at the four cardinal indices and non-monomial at every one of the $112$ intermediate indices of $\p\in\{13,17,29,37,41\}$.T
Prop. 8.10, § 8.1; D6, D7
2/2
F. The cyclotomic observer readout and the entropy cycle
F1p06037The readout algebra $A=\Z[\tfrac{1}{4n},X,Y,Y^{-1}]/(\Phi_n(X),Y^{2}-n)$ with the continuum chart $\sigma_\C$ ($X\mapsto\zeta_n$, $Y\mapsto+\sqrt n$) and the framed reduction $\rho$ ($X\mapsto\gen$, $Y\mapsto-\im$); the readout of a shell state as the Born vector of a selected lift, its Shannon entropy in nats, not thermodynamic.D
Def. 9.1
F2p06038$\widehat G^{2}=2n\,X^{\kap}$ in $A$, exact modulo $\Phi_n(X)$; under $\sigma_\C$, $(\sum_k\zeta_n^{k^{2}})^{2}=2n\,i$; under $\rho$, $G^{2}=2\im$, the reduction the proof of C7 uses.T
Def. 9.1, Thm. 5.8; E1
1/1
F3p06039Entropic cardinal values $H(0)=H(2\kap)=0$, $H(\kap)=H(3\kap)=\log n$ for every site-localized input; $B_0$ and $B_\kap$ mutually unbiased, $H_{B_0}+H_{B_\kap}\ge\log n$ saturated by the localized states and by the comb $(\delta_0+\delta_6)/\sqrt2$ at $n=12$, $\log2+\log6=\log12$ [approx].T
Prop. 9.2; E2, E3
2/2
F4p06040The closed form for $\delta_0$: $p_0=1-\tfrac{n-1}{n}t_s$, $p_{j\neq0}=t_s/n$, $t_s=(2-\zeta_n^{2s}-\zeta_n^{-2s})/4$, read as $\sin^{2}(\pi s/2\kap)$; $H(s)$ strictly increasing on $[0,\kap]$, two oscillations per cycle, strictly intermediate off the cardinal indices [approx].T
Prop. 9.3; E4
1/1
F5p06041$\p=13$: $H(s)/\log n=0,\,.44,\,.91,\,1,\,.91,\,.44$ over each half-cycle; Figure 2 regenerated [approx].T
§ 9.1; E5
1/1
F6p06042Input dependence: $\delta_1$ gives $H(1)/\log n=0.55$ against $0.44$ for $\delta_0$; $\delta_j$ meets the odd projectors exactly for $j\notin\{0,2\kap\}$, and $\delta_{2\kap}$ reproduces the $\delta_0$ curve [approx].T
Rem. 9.4; E6
1/1
F7p06043The Galois twist $X\mapsto\zeta_n^{u}$ relabels the $\delta_0$ curve by $s\mapsto us$ for every unit $u$ and leaves the cardinal values of every $\delta_j$ invariant; the conjugate twist $u=-1$ relabels the curve of every $\delta_j$, while for $j\notin\{0,2\kap\}$ a twist $u\not\equiv\pm1$ changes the intermediate curve ($n=12$, $\delta_1$, $u=5$: $0.55\mapsto0.44$ at $s=1$) [approx].T
Def. 9.1; E7
1/1
V. Machine verification (the validation package finite-ring-space/src/6-fourier)
V1p06044Blocks A–D of the package: $29$ integer-exact checks of B1B3, B5B7, C2C9, D1D2, D4D5, E2E3 and E5E7 on the six shells of Table 1, every primitive frame where a statement ranges over frames ($54$), all $4096$ pairs for additivity and covariance, the $112$-index sweep.T
V2p06045Block E: the readout on $\C^{n}$, $n=4,12,16,28,36,40$: F2 exact in $\Z[X]$, F3F7 to $10^{-9}$, Figure 2 regenerated.T
V3p06046The driver: five block scripts, one notebook run in the browser, $36$ checks ($30$ exact, $6$ [approx]), a record per check written to results.json keyed to these rows; the corpus master ledger’s rows C2, C14 and, on the transform layer, C7 are witnessed by B5, C3, D4, by B2, and by C9.T
run_all; the notebook
O. The open front
O1p06047Cardinal exclusivity: for every $s\notin\{0,\kap,2\kap,3\kap\}$ the operator (8.7) is not monomial — sweep-verified on the $112$ intermediate indices of E7, the proof obstructed by the possible vanishing of sparse six-term Laurent polynomials on subgroup cosets.O
Conj. 8.11
Collecting the tags separates what a reader must grant from what is derived. Imported are the framed substrate (A1), the Weil representation with its scalar convention (A2), the Gauss-sum evaluation and the classical eigenvalue counts (A3), the entropic uncertainty relation (A4), the framed-rational zoom (A5), the measurement layer (A6) and the continuum transform with the finite constructions it is compared with (A7). Declared are the shell data (B1), the Fourier matrix and its normalization (B4), the projectors and the principal lift (C1), the domains (D1), the scale map and its chart (D3), the scope of the unification (D6), the Weil-side data (E1), the scope and holographic reading of the dictionary (E4) and the readout algebra (F1): no realisation row is claimed, since the paper makes no physical identification of its own. Theorems are the thirty rows tagged T: the shell arithmetic (B2, B3, B5B7), the fractional family (C2C9), the domains and the zoom (D2, D4, D5), the dictionary and the operator-level comparison (E2, E3, E5E7), the readout (F2F7) and the three verification rows (V1V3); of these, the readout rows carry their floating-point figures as declared [approx] and are theorems in the sense that the named witness reproduces them to the stated tolerance, and D5’s zoom reading is a declared chart of the exact covariance D4. Nothing is $\Omega$-hard: every value of the paper is read on the Subject shell. Open is one item, the cardinal-exclusivity conjecture (O1). The paper’s title — the fractional Fourier transform and the scale shift as one finite rotation — is C3 together with D4 and E2; the entropic reading is F3 and F4.

Ledger history

Ledger history. 2026-09-13: ledger added (the paper predates the corpus convention), formulated from the labelled statements of Sections 3–9 and the validation package of the same date. One open row, O1, the cardinal-exclusivity conjecture; when it closes its content is re-homed in block E and the row leaves. No row has been retired.