Wiki
Wiki

Research notes on every problem, and a library of the papers behind them. Built from the open erdos repository.

Updated

Uniform full-dissociation extraction at the moment boundary


Result and standing

Let dd run through sufficiently large even integers, and put

kd=⌊d2−12dlog⁡d⌋.k_d=\left\lfloor\frac d2-\frac12\sqrt{d\log d}\right\rfloor.

Let Ed,kdE_{d,k_d} be the integer column vectors of all squarefree degree-at-most-kdk_d moments of points of {0,1}d\{0,1\}^d.

Theorem. There is a single δ>0\delta>0 such that every subset BB of every one of these configurations contains a fully dissociated subset of size at least δ∣B∣\delta|B|.

This settles the extraction side of this family. It does not prove that χ1(Ed,kd)\chi_1(E_{d,k_d}) is unbounded. The previously proved eventual lower bound six remains only a fixed lower bound. No negative solution of E0774 follows.

1. The exact lattice data

Write

n=2d,r=∑i=0kd(di),m=n−r,D=(d−kd)(dkd).n=2^d,\quad r=\sum_{i=0}^{k_d}\binom di,\quad m=n-r,\qquad D=(d-k_d)\binom d{k_d}.

The integer relation lattice KdK_d has rank mm, determinant 2D/22^{D/2}, and is isometric to the integer Boolean polynomial lattice of degree at most d−kd−1d-k_d-1. The semistability theorem proves that

Ld=σd−1Kd,σd=(det⁡Kd)1/m=2D/(2m),L_d=\sigma_d^{-1}K_d,\qquad \sigma_d=(\det K_d)^{1/m}=2^{D/(2m)},

is stable against all sublattices. The checked boundary asymptotics give

r/n⟶0,D/n⟶(2π)−1/2,σd⟶σ∗=21/(22π)>1.(1)r/n\longrightarrow0,\quad D/n\longrightarrow(2\pi)^{-1/2},\quad \sigma_d\longrightarrow \sigma_*=2^{1/(2\sqrt{2\pi})}>1. \tag{1}

In particular, the normalized determinant stays uniformly above one.

2. A single fixed-scale theta estimate

Choose any fixed 1<σ0<σ∗1<\sigma_0<\sigma_*. By the weak stable-lattice theorem, choose a fixed TT so large that

ϵ(T)≤12log⁡σ0,T≥T0.\epsilon(T)\leq\tfrac12\log\sigma_0, \qquad T\geq T_0.

Set s=1/(σ0T)<1s=1/(\sigma_0T)<1. For every sufficiently large dd, σd≥σ0\sigma_d\geq\sigma_0, and monotonicity followed by the theorem gives

θKd(s)=θLd(sσd)≤θLd(sσ0)≤(sσ0)−meϵ(T)m.\theta_{K_d}(s) =\theta_{L_d}(s\sigma_d) \leq\theta_{L_d}(s\sigma_0) \leq(s\sigma_0)^{-m}e^{\epsilon(T)m}.

Consequently

log⁡s+1nlog⁡θKd(s)≤rnlog⁡s−mn(log⁡σ0−ϵ(T))≤−m2nlog⁡σ0≤−14log⁡σ0=:−b<0.(2)\begin{aligned} \log s+\frac1n\log\theta_{K_d}(s) &\leq \frac rn\log s -\frac mn(\log\sigma_0-\epsilon(T))\\ &\leq-\frac{m}{2n}\log\sigma_0\\ &\leq-\tfrac14\log\sigma_0=:-b<0. \end{aligned} \tag{2}

The sign of the discarded first term uses s<1s<1. Both ss and bb are fixed independently of dd, of the subset to be extracted, and of any finite prefix.

Thus the former exact cancellation target is now satisfied. The growing-modulus formulation remains an alternative arithmetic description; no separate coding estimate is needed for (2).

3. From theta to hereditary full dissociation

The finite phase-entropy argument proves

μT(Bε)≤eπnε2/s2snθKd(s),\mu_T(B_\varepsilon)\leq e^{\pi n\varepsilon^2/s^2}s^n\theta_{K_d}(s),

for the actual character-image torus TT. Choose fixed ε>0\varepsilon>0 with πε2/s2≤b/2\pi\varepsilon^2/s^2\leq b/2. Equation (2) gives exponential fixed-scale phase packing. The finite Gaussian comparison on that page gives W(Ed,kd)≥cnW(E_{d,k_d})\geq cn. The single-set inequality

α(Ed,kd)≥W(Ed,kd)2/(Cn)\alpha(E_{d,k_d})\geq W(E_{d,k_d})^2/(Cn)

then supplies a dissociated subset FdF_d of size at least δn\delta n, for one positive δ\delta. This precise inequality and the full quasi-independence definition were rechecked in Lefèvre--Li--Queffélec--Rodríguez-Piazza, Theorem 3.4, equation (3.3) (arXiv:0902.2625, printed page 10).

Cube translations permute the columns transitively and preserve every integer relation: substituting xi↦1−xix_i\mapsto1-x_i is an invertible integer change on the degree-at-most-kdk_d moment rows. For any B⊆Ed,kdB\subseteq E_{d,k_d}, average ∣B∩gFd∣|B\cap gF_d| over cube translations gg. The average is ∣B∣∣Fd∣/n≥δ∣B∣|B||F_d|/n\geq\delta|B|. Some such intersection has that size and is fully dissociated. There is no restriction on relation length.

Any finitely many earlier admissible stages can be included by decreasing δ\delta to the minimum of this constant and their positive singleton fractions 1/∣Ed,kd∣1/|E_{d,k_d}|. Alternatively, start the family at the uniform threshold. Neither choice creates blockwise decay.

4. The remaining required obligation

The exact integer encoding and separated-block assembly already apply to these finite integer-vector sets. To turn them into the requested counterexample, it still suffices—and is still necessary for this proposed family—to prove

sup⁡d evenχ1(Ed,kd)=∞.\sup_{d\ {\rm even}}\chi_1(E_{d,k_d})=\infty.

No such theorem is proved here. Affine syndrome classes and fixed checksum palettes have known monochromatic trades, but general colors do not obey those restrictions. The extraction proof does not turn those restricted results into arbitrary-color growth.

The stable-theta argument, its external inputs, and this application chain received separate internal reviews. No new numerical experiment was run.