Bibliographic record
Abstract
We introduce the primitive Eulerian polynomial \(P_{\mathcal{A}}(z)\) of a central hyperplane arrangement \(\mathcal{A}\). It is a reparametrization of its cocharacteristic polynomial. Previous work by the first author implicitly shows that for simplicial arrangements, \(P_{\mathcal{A}}(z)\) has nonnegative coefficients. For reflection arrangements of types A and B, the same work interprets the coefficients of \(P_{\mathcal{A}}(z)\) using the (flag) excedance statistic on (signed) permutations.The main result of this article is to provide an interpretation of the coefficients of \(P_{\mathcal{A}}(z)\) for all simplicial arrangements using only the geometry and combinatorics of \(\mathcal{A}\). This new interpretation sheds more light to the case of reflection arrangements and, for the first time, gives combinatorial significance to the coefficients of the primitive Eulerian polynomial of the reflection arrangement of type D, for which no well-behaved excedance statistic is known. In type B, we establish a link between the primitive Eulerian polynomial and the \(1/2\)-Eulerian polynomial of Savage and Viswanathan (2012). We present some results and conjectures regarding the real-rootedness of \(P_{\mathcal{A}}(z)\).Mathematics Subject Classifications: 52C35, 05A05Keywords: Hyperplane arrangement, Eulerian polynomial, Tits product, permutation statistics
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.001 | 0.002 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.011 | 0.002 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".