REVIEW
Certified Collision Exclusion and an Unconditional Upper Bound $\Lambda<0.156821$ for the de Bruijn--Newman Constant
Number Theory · Submitted 4 Nov 2026 · 21 references
Pith's verdict: Ambitious but fragile: the collision-exclusion method is new and the bound improves the record, but the proof's narrow feasibility margin and extreme complexity mean it needs careful independent validation.
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Referee report
The paper
The paper claims
An unconditional upper bound Λ < 0.156821 for the de Bruijn–Newman constant is proved via a certified collision-exclusion method that replaces the canopy criterion with a real double-zero exclusion.
The reading
What carries the argument
The central mechanism is the collision-exclusion framework: replacing the canopy criterion (which prohibits nonreal zeros crossing a complex boundary) with the global exclusion of real double zeros (H_t, H'_t) = (0,0) on a closed time interval. This is reduced, after a balanced real gauge, to a positivity statement for a Hermitian form in a pair of analytic prime-polynomial coordinates. The five stable Gram source polynomials (MA1) – each defined on a specific index interval with a synthetic fibre δ_j and weight ϑ_j – satisfy a strict torus inequality (G) that ensures, via Lemma 4.3 (ordinary weighted recovery), that the full source polynomial never vanishes on the closed unit polydisc and has modulus > δ_j. The balanced real-jet transfer (Theorem 3.1 and Corollary 3.2) converts this polynomial lower bound into a nonvanishing lower bound for the physical pair (H_t, H'_t) over the finite exterior. For the infinite exterior, a uniform Euler-product barrier (Section 8) yields a positive lower bound for u² + u_x² through a differential inequality on the completed resultant matrix. The stationary separator (Section 6) and compact interior theorem (Theorem 7.2) handle the remaining regions.
Extended reading notes
Core claim
The paper establishes that Λ < 156821/1000000 = 0.156821, and does so by excluding the possibility of a multiple real zero at any point in the time band [0.156821, 0.2] and spatial region |x| ≥ 6000000185827 ∪ [X,W] ∪ [W,∞) (with explicit constants). The argument separates three regions: a stationary separator at x = X, a compact interior where all zeros are real and simple by propagation, a finite exterior where five Gram sources guarantee a stable polynomial modulus > 1/790, and an infinite exterior where a differential inequality gives u² + u_x² > 3/10000. A critical-time compactness lemma shows that if Λ lies in the band, H_Λ would have a finite multiple real zero; the regional exclusions contradict that, forcing Λ below the band. The proof does not assume any new zero-free half-plane or unverified analytic hypotheses beyond the published Polymath approximations and Platt–Trudgian finite-RH result.
Load-bearing premise
The five prime-polynomial Gram sources (MA1) must satisfy the strict positivity conditions of the torus inequality (G) and the ordinary weighted recovery inequality (OR1) with exact, outward-rounded rational coefficients; if any single source certificate is invalid due to rounding, a missed term, or a narrow feasibility margin, the finite-exterior exclusion could fail and the bound might not hold.
Editorial extensions
If this is right
- The unconditional upper bound for Λ is lowered from 0.2 to 0.156821, providing the sharpest published unconditional bound in the Polymath normalisation.
- The collision-exclusion method offers a new global framework for bounding Λ that, unlike the canopy approach, does not require a nonzero imaginary part of the zero-free region, and thus may be more amenable to further refinement with stronger finite-RH data.
- The proof demonstrates that the Platt–Trudgian verification up to 3 trillion is sufficient to support a substantially better bound than the previously published 0.2, showing the power of the method over a simple barrier estimate.
- The public certificate archive (with 44,182 torus boxes, 17,385 separator rectangles, etc.) sets a high standard for reproducibility; an independent re-execution would either confirm the bound or reveal a flaw, making the result auditable.
- If the bound is accepted, the gap between the best conditional bounds (≈0.107965 under H₇/₈) and the best unconditional bound is narrowed, highlighting the remaining distance to Λ=0 needed for the Riemann hypothesis.
Reading between the lines
- The narrow feasibility margin (≈5.8×10⁻⁷ below the endpoint) observed for the four-prime Gram family suggests that any further improvement with the same polynomial architecture may require either a different weight distribution or the inclusion of a fifth prime in the smooth fibre, as the authors acknowledge.
- The collision-exclusion method separates the global problem into independent regional certificates; therefore, future improvements in the finite-RH height or in the source polynomial construction can be plugged in directly without re-proving the entire assembly, making incremental progress on Λ a modular task.
- The explicit certification of the four-prime Cauchy–Schwarz obstruction (Proposition 4.1) gives a precise feasibility ceiling for that family, which could guide the search for alternative polynomial bases that avoid the obstruction and potentially push the bound toward 0.15 or lower.
- The paper's careful distinction between unconditional and conditional/unrefereed bounds (Table 1) clarifies the logical status of several recent claims, which may influence how the community evaluates progress on the de Bruijn–Newman constant.
Original abstract
The de Bruijn--Newman constant $\Lambda$ is the transition time beyond which all zeros of the heat-deformed Riemann $\xi$-function are real. We develop a computer-assisted collision-exclusion method and obtain the bound $\Lambda<156821/10^6=0.156821$, in the normalisation of Polymath. The proof combines the published finite-height verification and the starting inequality $\Lambda\leq1/5$ with a compact-interior continuation theorem, five stable prime-polynomial Gram sources, certified moving-index recovery, a balanced real-jet transfer and a uniform Euler-product barrier at infinity. The resulting closed time-band exclusion, together with uniform remote reality, forces strictness at the proposed endpoint. The finite certificate uses 664,505 structural Fourier coefficients, 44,182 closed torus boxes, 184 separator moments and 17,385 separator rectangles. We isolate a Cauchy--Schwarz obstruction intrinsic to the four-prime source family, explaining the narrow feasibility margin of the certified endpoint. We state the proof-to-certificate interface and distinguish the present unconditional logical claim from other recent, as yet unrefereed, computational bounds.
The compiled record
The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.
The abstract, sentence by sentence
The de Bruijn--Newman constant $\Lambda$ is the transition time beyond which all zeros of the heat-deformed Riemann $\xi$-function are real. We develop a computer-assisted collision-exclusion method and obtain the bound $\Lambda<156821/10^6=0.156821$, in the normalisation of Polymath. The proof combines the published finite-height verification and the starting inequality $\Lambda\leq1/5$ with a compact-interior continuation theorem, five stable prime-polynomial Gram sources, certified moving-index recovery, a balanced real-jet transfer and a uniform Euler-product barrier at infinity. The resulting closed time-band exclusion, together with uniform remote reality, forces strictness at the proposed endpoint. The finite certificate uses 664,505 structural Fourier coefficients, 44,182 closed torus boxes, 184 separator moments and 17,385 separator rectangles. We isolate a Cauchy--Schwarz obstruction intrinsic to the four-prime source family, explaining the narrow feasibility margin of the certified endpoint. We state the proof-to-certificate interface and distinguish the present unconditional logical claim from other recent, as yet unrefereed, computational bounds.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | The de Bruijn--Newman constant $\Lambda$ is the transition time beyond which all zeros of the heat-deformed Riemann $\xi$-function are real. | background 1.00 | 0.04 | 0.03 | asserted 1.00 |
| s1 | We develop a computer-assisted collision-exclusion method and obtain the bound $\Lambda<156821/10^6=0.156821$, in the normalisation of Polymath. | result 0.90 | 0.97 | 0.93 | asserted 1.00 |
| s2 | The proof combines the published finite-height verification and the starting inequality $\Lambda\leq1/5$ with a compact-interior continuation theorem, five stable prime-polynomial Gram sources, certified moving-index recovery, a balanced real-jet transfer and a uniform Euler-product barrier at infinity. | method 0.97 | 0.79 | 0.32 | asserted 1.00 |
| s3 | The resulting closed time-band exclusion, together with uniform remote reality, forces strictness at the proposed endpoint. | interpretation 0.90 | 0.64 | 0.08 | asserted 0.98 |
| s4 | The finite certificate uses 664,505 structural Fourier coefficients, 44,182 closed torus boxes, 184 separator moments and 17,385 separator rectangles. | method 0.93 | 0.84 | 0.02 | asserted 1.00 |
| s5 | We isolate a Cauchy--Schwarz obstruction intrinsic to the four-prime source family, explaining the narrow feasibility margin of the certified endpoint. | interpretation 0.46 | 0.91 | 0.03 | asserted 1.00 |
| s6 | We state the proof-to-certificate interface and distinguish the present unconditional logical claim from other recent, as yet unrefereed, computational bounds. | contribution 0.73 | 0.86 | 0.04 | asserted 0.89 |
What was examined, and what was not
- arXiv listing abstract v1
- full text
- figures and tables
- references and citing sentences
- relations to other papers
- P abstract
- S sections
- T body sentences
- C citations
- R cross-paper relations
References
Discussion
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