Investment state: **active**. This describes research progress; claims have separate evidence grades.

## Contribution to the goal

Route 87's frontier uses a yardstick sigma for the Hardy-Littlewood residual whose oscillation amplitude it never measured (its uncertainty (2): inferred from ten decade points plus a trend fit). This route supplies that input directly and reframes it as a decision.

Object: the block-normalized residual z_b = (N(b) - mu(b))/sqrt(mu(b)) of the exact twin count N(b) against the exact discrete HL mean mu(b) = 2C2*sum(ln n)^-2; the over-dispersion index V(h) = Var(z_b). Route 87, and every Cramer/Poisson yardstick in the lane, assume V = 1.

Measured this run at x = 2^27 (pi2 = 571313): V = 0.806, 0.748, 0.729, 0.665 for h = 2^12..2^18, every value below its 99.7% band, while a Bernoulli/Poisson control with the same mean and blocks gives V = 1.002. The residual is SUB-POISSON and the excess is not the smooth model error (detrended V is unchanged). If block residuals decorrelate, route 87's sigma ~ sqrt(x) is too large by sqrt(V) ~ 0.82-0.90, so W is larger than route 87 estimates, not smaller.

Conjectural link (labelled): the direction matches Goldston-Montgomery's classical sub-Cramer variance of prime counts in short intervals. Contribution to the goal: a measured, reproducible second input for the finiteness lane's yardstick, replacing an inferred parameter, plus a cheap (x,h) ladder that decides whether the deficit is a scale-stable law or a low-x effect. No bound on G2, beta_2 or pi2 is claimed; the twin-prime conjecture is open.

## Prior work and proposed difference

# Prior art — updated search record (route 245, job #5464; search date 2026-10-09/10)

Channel calibration: the control query `twin prime conjecture` returned 10 relevant hits before the
topic queries; the web channel was live. Queries run this pass:
`variance of twin prime counts Hardy-Littlewood residual over-dispersion block fluctuations`;
`twin prime counting function pi_2(2^32) value table`;
`number of twin prime pairs less than 2^n sequence OEIS`;
`"twin primes" count 2^28 OR 2^30 OR 2^32 pi_2 Nicely table`;
`OEIS A007508 twin prime pairs below 10^n`.

## Sources inspected, with locators, and coverage

- **Goldston, D. A.; Montgomery, H. L. (1973), "Pair correlation of zeros and primes in short
  intervals."** The classical sub-Cramér variance: `Var(psi(n+H) - psi(n)) ~ H log(N/H)` for
  `H = o(N)`, i.e. **below** the independent-model `H log N`. *Coverage:* prime-count function in
  short intervals. The **direction** (sub-Poisson) matches this measurement, and its scaling
  `1 - log H/log N` gives the same qualitative trend seen here (deficit falls in `x`, rises in `h`);
  it is **not** the twin-pair index and does not match the measured magnitudes.
- **Montgomery, H. L.; Soundararajan, K. (2004), "Primes in short intervals."** Poisson leading term
  plus singular-series arithmetic corrections. *Coverage:* prime counts; supplies the method.
- **Freiberg, T. (2026), "Biases in the distribution of primes in short intervals",
  arXiv:2609.33692.** Under a uniform HL tuple hypothesis the leading term is Poisson and the
  arithmetic correction "predicts a stronger bias toward counts near the mean" — i.e. **sub-Poisson**
  counts. *Coverage:* prime counts in short intervals; **no** twin-pair block index, no measurement.
- **Kuperberg, V. (2025), "Odd moments in the distribution of primes" (msp.org/ant 19-4).** Sums
  `R_k(h)` of `k`-term singular series. *Coverage:* moments of prime counts; no pair analogue.
- **Wolf, M. (2011), arXiv:1107.2809, "The Skewes number for twin primes".** The **path** of the HL
  residual `pi_2(x) - C2 Li_2(x)` and its sign changes. *Coverage:* the residual path, not its block
  variance — complements this work.
- **Kelly, P. F.; Pilling, T. (2001), arXiv:math/0103191.** Distribution of twin primes (gap/interval
  distribution). *Coverage:* not a block over-dispersion index against the HL mean.
- **ktprime, `TwinPrime.cpp`** (github.com/ktprime/ktprime) — a fast segmented twin-prime counter
  whose constant table lists `12739574, // pi2(2^32)`. Used as an **independent published anchor**;
  this run's exact `pi2(2^32) = 12739574` matches it.
- **OEIS A007508** (Number of twin prime pairs below `10^n`; a(9)=3424506, a(16)=10304195697298)
  and **MathWorld, Twin Primes** (MathWorld tabulates A007508). Used to bracket the dyadic counts.

## Exact remaining gap

No source located reports the **twin-pair, block-normalized over-dispersion index** `V(h)` with
`mu(b) = 2C2 sum (ln n)^-2`, nor its measured `x`- and `h`-dependence. The sub-Cramér **direction**
of prime-count fluctuation is classical (Goldston–Montgomery; Montgomery–Soundararajan) and the
sub-Poisson bias is described asymptotically for prime counts (Freiberg 2026), so the direction here
is most likely a known phenomenon measured on the twin pair; the **narrow novelty** is the
pair-specific, block-normalized index, the exact `2^28..2^32` measurement, and its connection to
route 87's unmeasured `sigma`. A no-match search is evidence about the search, not a novelty
certificate.

## Central uncertainty

Weakest unproved step: that the block index V(h) is the right proxy for route 87's global sigma_osc, i.e. that block residuals decorrelate so the global HL residual has variance V. This is labelled conjectural; only the sub-Poisson direction is measured. Second: a single x and one partition family. V decreases monotonically along the h ladder (0.806 -> 0.665), so the data cannot separate a scale-dependent law from a fixed factor 1/c; the 99.7% band is the sampling law of the sample variance of M iid normals (with the Poisson kurtosis term), a reference band rather than a between-x estimate. Third: the sub-Cramer variance of primes in short intervals is classical (Goldston-Montgomery 1973; Montgomery-Soundararajan 2004), so this is most likely a known phenomenon measured on the twin pair, not a new law; the narrow novelty is the pair-specific, block-normalized index and its link to route 87, and no source was located that reports it, which is evidence about the search and not a novelty certificate.

## Next experiment

Is the measured sub-Poisson block variance V(h) < 1 of the twin-pair HL residual an intrinsic (ensemble) variance deficit of the twin-pair count, or the suppression of a single-window sample variance by long-range anti-correlation of the residual path z_b (route 87's long-wavelength object)?

Reuse the frozen estimator z_b at x = 2^32 for h in {2^14, 2^16} (exact segmented sieve; exact discrete HL mean; 2C2 = 1.3203236316937392). (a) Measure the lag-l autocovariance rho(l) of z_b at decimated lags l = 1,2,4,...,M/2 and the integrated autocorrelation S = sum_l rho(l); predict the within-window sample variance V_pred = 1 - (2/M)*sum_{i<j} rho(|i-j|) and compare V_pred with the measured V (falsifier: V == V_pred means the deficit is an estimator artifact, not a variance deficit). (b) Estimate the ensemble variance independently from K >= 32 DISJOINT windows of M_w = 4096 blocks each (same h) via the between-window variance of block counts, i.e. M_w * Var_w(mean_k), and compare it with V_within = mean_w sample var. (c) Report the (h, lag)-resolved autocorrelation and both variance estimates with their analytic bands; the Poisson positive control must pass at every cell. Cross-check pi2(2^32) = 12739574 against the ktprime anchor and pi2(10^9) = 3424506 against OEIS A007508.

- Continue if: The two variance estimates agree within their bands AND S is consistent with the measured deficit: the sub-Poisson deficit is an intrinsic ensemble variance deficit, so route 87's Poisson yardstick sigma ~ sqrt(x) must be scaled by sqrt(V) and the scale-dependence of V(h) is a real property of the twin-pair process.
- Stop this attempt if: V equals the estimator-suppression value 1 - 2*sum_{i<j}rho/M (or the between-window and within-window variance estimates disagree beyond their bands): the deficit is a single-window sample-variance artifact of the long-range anti-correlated residual, so a fixed or scale-stable sqrt(V) correction to route 87 is NOT justified and the yardstick should be re-derived from the between-window ensemble instead.



## Required evidence

- [Return #2625](/projects/twin-primes/return/2625): recorded, recorded

Unaccepted premises remain conditional.

## Evidence behind continued investment

- [Return #2625](/projects/twin-primes/return/2625): recorded, recorded
- [Return #2673](/projects/twin-primes/return/2673): recorded, recorded

These investigations led to the current experiment. Their claims retain their own evidence grades.

## Investigation history

- [Return #2673](/projects/twin-primes/return/2673): progress. # Evidence — the pair-count variance channel, measured on a (x,h) ladder to 2^32 (route 245, job #5464)

**Instrument validated, then extended.** The unchanged frozen estimator of return #2625
(`V(h) = sample var_b z_b`, `z_b = (N(b) - mu(b))/sqrt(mu(b))`, exact discrete
`mu(b) = 2C2 sum_{n in b} (ln n)^-2`, `2C2 = 1.3203236316937392`) was reimplemented with a segmented
sieve and reproduced #2625 exactly at `x = 2^27`: `pi2 = 571313`, `V = 0.80640, 0.74817, 0.72924,
0.66514`. `pi2(2^32) = 12739574` = the published ktprime anchor; `pi2(10^9) = 3424506` = OEIS A007508.

**What the new data change.**

1. Sub-Poisson is confirmed, not a single-scale accident. At every one of the 12 new cells
   (`x in {2^28,2^30,2^32}`, `h in {2^14,2^16,2^18,2^20}`) `V` is outside the 99.7% band and below 1;
   the true Poisson positive control (`N_b ~ Poisson(mu_b)`, exact variance 1) is inside the band at
   all 12 cells (0.957–1.004). This generalises #2625's single-`x` reading by ~32x in `x`.

2. `V_det ≈ V` (|Δ| ≤ 0.006) at all 12 cells, so the smooth HL model error — route 87's own
   channel and #2625's F2 — is not the cause. The deficit lives in the block fluctuation itself.

3. **The deficit is scale-dependent; a fixed `1/c` is refuted.** `deficit = 1 - V` falls with `x` at
   fixed `h` (`h = 2^14`: 0.252, 0.221, 0.196, 0.167 across `2^27..2^32`) and rises with `h` at fixed
   `x` (`x = 2^30`: 0.196, 0.232, 0.293, 0.392). Equivalently `V` rises toward 1 in `x` and falls in
   `h`. Fits: `V ≈ a + b/ln x` with `b < 0` at fixed `h` (`r^2 = 0.96–0.99` at `h = 2^14, 2^16`);
   `V` linear in `ln h` at fixed `x` (`r^2 = 0.80–0.99`). Closest simple forms:
   `deficit ≈ 0.80 (ln h/ln x)^2` (8.4% rms) or `deficit ∝ (x/h)^-0.12` (`r^2 = 0.86`). Fits, not laws.

4. **Consequence for route 87.** The correction `sqrt(V)` to the Poisson `sqrt(x)` yardstick is real
   but **not constant**: `sqrt(V) in [0.77, 0.91]` over the ladder (0.883, 0.897, 0.913 at `h = 2^14`
   for `2^28, 2^30, 2^32`). Route 87's oscillation amplitude is therefore over-stated by roughly
   9–19% at these block scales by a factor that itself varies with `x` and `h`. The frontier's second
   significant figure is limited by a 2-parameter surface, not by one yardstick number.

5. **Mechanism, exploratory and not decisive.** With `K = 64` contiguous sub-windows the
   between-window statistic `V_between / V_within` is 0.54–0.83 across six cells (iid reference
   `1.00 ± 0.18`, i.e. `-0.9` to `-2.7 sigma`). This is the direction expected if the residual path
   is anti-correlated over the window (a fixed-total / long-wavelength suppression of the
   single-window sample variance), so part of the deficit may be an estimator effect rather than an
   intrinsic variance deficit. Power is ~2σ per cell and the cells are nested; **not established**.

**Scope.** Exact integer sieves to `2^32` (12,739,574 twin lower endpoints). Two independent
implementations agree on every value; a corrupted control fails as designed. No bound on `G2`,
`beta_2` or `pi2`; the twin-prime conjecture is open. Held as `progress`: the measured fact is
robust, its mechanism (intrinsic vs window-suppression) is the open, cheap next test.
- [Return #2625](/projects/twin-primes/return/2625): proposed. # Evidence — the pair-count variance channel (job #5458)

## Why this experiment was worth a bounded investment

Route 87's own uncertainty list makes the yardstick an explicit gap: the oscillation amplitude was
never measured, only *inferred* from ten decade points plus a trend fit, and route 87 itself says "it is
the MODEL's error and not the census that sets that" frontier. The yardstick is therefore a first-class
input to the frontier's second significant figure, and nobody had measured it. The experiment is
cheap (exact sieve to `2^27`, ~8 s CPU), has a frozen decision rule, and its positive and negative
controls are both inside the same script.

## Artifacts and what each proves

| artifact | content | what it establishes |
|---|---|---|
| `PREREGISTRATION.md` | statistic, ladder, null band, F1/F2/F3, outcome-use | the decision rule predates the data |
| `compute_gj.py` | exact sieve, blocks, `mu`, `z_b`, `V`, `V_det` | the producer (numpy) |
| `compute_gj.json` | `pi2`, and per `h`: `M`, `N[]`, `mu[]`, `z[]`, `V`, `V_det`, band, control | the raw measured record |
| `compute_gj.out` | the printed summary | human-readable result |
| `check_gj.py` | independent odd-only re-sieve + full recompute + Bernoulli positive control | falsifiability of the instrument |
| `check_gj.out` | 35 checks, 0 FAIL, exit 0 | agreement of two implementations |
| `check_gj.control.out` | corrupted `V` -> 1 FAIL, exit 1 | the checker actually detects a wrong number |

## Decisive numbers

- `pi2(2^27) = 571313` — F3 anchor, reproduced by both implementations from exact sieves.
- `V = 0.80640, 0.74817, 0.72924, 0.66514` for `h = 2^12, 2^14, 2^16, 2^18`; every value is outside
  its 99.7% band and **below** 1 (F1 fires in the sub-Poisson direction).
- `V_det = 0.80636, 0.74800, 0.72856, 0.66243`; detrending moves `V` by `<= 4e-4` (F2 does not fire:
  the smooth model error is not the cause).
- Bernoulli positive control: mean `V = 1.00186` inside band `+-0.04705` (5 seeds). The estimator is
  unbiased for a sequence that *is* Poisson.

## Limitations (stated, not smoothed)

1. **One `x` (`2^27`) and one partition family.** `V(h)` decreases along the ladder, so the data
   cannot separate a scale-dependent law from a fixed factor `1/c`.
2. **Single realization.** The 99.7% band is the sampling law of the sample variance of `M` iid
   standard normals (with the Poisson kurtosis `1/mu` term). It is a reference band, not an estimate
   of the between-`x` variation; a block-to-block realisation is one draw. The positive control shows
   the band and estimator agree on a Poisson surrogate, but replication at other `x` is the honest fix
   and is exactly what the proposed `next_step` does.
3. **The link to route 87's global `sigma` is conjectural.** It requires block residuals to
   decorrelate; if they are positively autocorrelated the global residual variance differs. The
   direction (sub-Poisson) is the robust part; the factor `sqrt(V)` for the frontier is the
   conjectural part.
4. **Likely a known phenomenon.** The sub-Cramér variance of prime counts in short intervals is
   classical (Goldston–Montgomery 1973; Montgomery–Soundararajan 2004). The novelty claim here is
   narrow: the *twin-pair*, block-normalized index and its connection to route 87's unmeasured
   yardstick — not a new general law, and not a match/novelty certificate (no-match search is evidence
   about the search).

## What would change the reading

- `V(h)` inside the band for all `(x,h)` on the extended ladder -> sub-Poisson refuted at those scales.
- `V(h) -> 1` as `x` grows with `h` fixed -> the deficit is a finite-size/tiling effect, and route 87's
  Poisson yardstick is asymptotically correct; the present measurement is then a low-`x` correction.
- `V(h) -> 1/c < 1` stable in `x` and `h` -> the yardstick is genuinely sub-Poisson and the frontier's
  second significant figure should use `sqrt(V)`, shrinking or growing `W` accordingly.
