diff --git a/content/essays/ball-occupation-under-coarse-projections.md b/content/essays/ball-occupation-under-coarse-projections.md index 27a23de..a90f9c6 100644 --- a/content/essays/ball-occupation-under-coarse-projections.md +++ b/content/essays/ball-occupation-under-coarse-projections.md @@ -3,28 +3,21 @@ title: "Ball-Occupation Certificates under Coarse Graph Projections" subtitle: "Degree Reduction, Square-Root Hard Families, and Toroidal Barriers" date: 2026-07-27 abstract: > - We isolate an abstract strategy-transfer principle for Cops and Robber: if a - surjection from H onto G has fibers of bounded order P and distances - between distinct fibers stretched by a scale factor lambda with bounded - additive slack, then a Hall-type assignment occupies a lifted macro-ball - before the robber can leave it, giving cop number O(P(d^3 + log(ePN)) - sqrt(N)) and capture time at most lambda R -- independent of the tower - depth lambda itself. Applied to the iterated degree-reduction construction - of Hosseini-Mohar-Gonzalez Hermosillo de la Maza, this shows the known - polylog-degree hard family for Meyniel's conjecture already meets the - square-root exponent up to polylogarithmic factors, sharper than the - M^{1/2+o(1)} notation suggests. A separate counting argument then proves a - sharp limitation of the one-shot occupation strategy class itself: for - every fixed k, Cartesian tori of k cycles have bounded metric doubling, - exact cop number k+1, and linear one-shot occupation cost at every radius, - so polynomially weak expansion alone cannot certify a universal robustness - theorem -- the obstruction in the universal problem is adaptive reuse - across many weak-growth layers, not degree reduction itself. + We isolate an abstract strategy-transfer principle for Cops and Robber: a + coarse graph projection with bounded fibers and bounded distance distortion + lets cops occupy a lifted macro-ball before the robber escapes, giving cop + number O(sqrt N) up to polylogarithmic factors. Applied to the + Hosseini-Mohar-Gonzalez Hermosillo de la Maza degree-reduction + construction, this shows the known hard family for Meyniel's conjecture + already meets the square-root exponent, sharper than the usual notation + suggests. A counting argument then proves a sharp limit on the strategy + class itself: Cartesian tori of cycles have bounded doubling and constant + cop number but linear occupation cost at every radius, so weak expansion + alone cannot certify a universal robustness theorem. tags: - research - research/mathematics - research/graph-theory -keywords: [cops and robber, meyniel's conjecture, graph products, degree reduction, coarse graph projections, expansion, occupation certificates] authors: - "Levi Neuwirth | /me.html" affiliation: diff --git a/content/essays/near-critical-growing-radius-domination.md b/content/essays/near-critical-growing-radius-domination.md index bc56953..fa7c391 100644 --- a/content/essays/near-critical-growing-radius-domination.md +++ b/content/essays/near-critical-growing-radius-domination.md @@ -197,7 +197,7 @@ with $0\log 0=0$; for a scalar $a\in[0,1]$, $H(a)$ denotes the binary entropy $H | $z=e^\theta$ | grand-canonical activity | | $b=d-1,\ D=d/(d-2)$ | recurring degree constants | -::: {#def-two-path .exhibit .exhibit--definition data-exhibit-type="definition" data-exhibit-name="Definition 1 (Internally two-path $(h,2)$ domination)"} +::: {#def-two-path .exhibit .exhibit--definition data-exhibit-type="definition" data-exhibit-name="Definition 1 (Internally two-path (h,2) domination)"} **Definition 1** (Internally two-path $(h,2)$ domination). A set $S\subseteq V(G)$ is *internally two-path $(h,2)$ dominating* if every vertex $v\notin S$ has two $v$–$S$ paths of length at most $h$ whose only common vertex is $v$. In particular, the paths begin through distinct neighbors of $v$. Let $\gamma_{h,2}^{\mathrm{int}}(G)$ denote the minimum size of such a set. :::