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Bibliographic record
Abstract
The amplituhedron \(\mathcal{A}_{n,k,m}\) was introduced by Arkani-Hamed and Trnka (2014) in order to give a geometric basis for calculating scattering amplitudes in planar \(\mathcal{N}=4\) supersymmetric Yang-Mills theory. It is a projection inside the Grassmannian \(\text{Gr}_{k,k+m}\) of the totally nonnegative part of \(\text{Gr}_{k,n}\). Karp and Williams (2019) studied the \(m=1\) amplituhedron \(\mathcal{A}_{n,k,1}\), giving a regular CW decomposition of it. Its face poset \(R_{n,l}\) (with \(l := n-k-1\)) consists of all projective sign vectors of length \(n\) with exactly \(l\) sign changes. We show that \(R_{n,l}\) is EL-shellable, resolving a problem posed by Karp and Williams. This gives a new proof that \(\mathcal{A}_{n,k,1}\) is homeomorphic to a closed ball, which was originally proved by Karp and Williams. We also give explicit formulas for the \(f\)-vector and \(h\)-vector of \(R_{n,l}\), and show that it is rank-log-concave and strongly Sperner. Finally, we consider a related poset \(P_{n,l}\) introduced by Machacek (2019), consisting of all projective sign vectors of length \(n\) with at most \(l\) sign changes. We show that it is rank-log-concave, and conjecture that it is Sperner.Mathematics Subject Classifications: 06A07, 14M15, 81T60, 05A19Keywords: Amplituhedron, shellability, Eulerian number, log concavity, Sperner property
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
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 it