Problems
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Zhi-Wei Sun conjectured a closed evaluation of a truncated Legendre-symbol determinant. For every prime p ≡ 3 pmod 4 it equals ⌊ (p-2)/3 ⌋^2 x, proved by reducing to inverse data for Chapman's full Legendre-symbol matrix and evaluating…
For an irreducible crystallographic root system of rank r with Coxeter number h, the paper proves that Au's normalized Witten zeta function has a simple pole at 2/h and evaluates its residue in closed form in terms of the Cartan…
For deterministically minimizing a convex 1-Lipschitz function on the d-dimensional ball using only exact function values, the query complexity sat between Ω(d) and O(d^2 log^2 d) since 1996. The paper proves a near-quadratic lower bound…
Can the k-distinct language - words over [n] of length at most k with no repeated symbol - be recognized by an acyclic NFA of size c^k n^O(1) for some c < 4? A construction of size 2^1.96992k n^O(1) < 3.918^k n^O(1) answers yes.
A subset A of the pointwise-ordered cube [0,1]^n is a k-antichain when it meets every chain in at most k points. The conjecture concerns the largest possible (n-1)-dimensional Hausdorff measure of such a set; it is settled here, following…
How many nondegenerate equilibrium points can the potential of three positive point charges have? Gabrielov, Novikov and Shapiro had proved at most 12, and observed that their method would give 6 if an auxiliary polynomial system had at…
Does every instance of indivisible goods with additive valuations admit a balanced allocation (any two bundles differing in size by at most one) that is simultaneously envy-free up to one good (EF1) and fractionally Pareto optimal (fPO)?…
Englert and Rehacek conjectured which measurement is globally information-optimal for an ensemble of equiangular equiprobable pure states. Their conjecture holds, via the remaining entropy inequalities of Holevo and Utkin.
A tournament orients every pair in a round-robin (winner → loser). The score sequence is the sorted win-count list. Reversing a directed 3-cycle never changes scores, so score-equivalent tournaments can look structurally different.…
Godara and Sarkar proved d(H_27)=6 for the exponent-p Heisenberg group and posed d(H_p^3)=3p-3 for every odd prime p, leaving p≥5 open. The paper settles the first open case, d(H_125)=12, the upper bound reducing to a finite spread bound…
We prove that every PPT linear map has finite entanglement-breaking index, thereby establishing the eventual entanglement-breaking property of PPT channels in full generality. Furthermore, by utilizing completely positive maps with low…
Energy measures of any two nonconstant harmonic functions on the standard Sierpinski gasket are mutually absolutely continuous. Strichartz and Tse reported numerical evidence that the Radon-Nikodym densities are L^p-integrable for 1 < p <…
Does planarity help approximate counting? The paper gives an FPRAS for the planar hard-core partition function at small activity, proves that approximately counting q-colourings on planar graphs is NP-hard for every constant q ≥ 4, and…
Sampling a nearly uniform Eulerian tour of a directed Eulerian multigraph was stuck at mn-type running times coming from arborescence sampling. A randomized algorithm achieves widetildeO(m^3/2) worst case, breaking that barrier on sparse…
Let H(n) be the largest number of vertices in a hypergraph with no isolated vertices and no partition of size greater than n. With k_1 = 1 and k_n = ⌊ n/2 ⌋ + k_⌊ n/2 ⌋ + k_⌈ n/2 ⌉, prove H(n) ≥ c k_n for some constant c > 1, already for n…
A t-(v,k,λ) covering is a family of k-subsets of a v-set meeting every t-subset at least λ times, and C(v,k,t) is the least number of blocks. The recorded bounds for C(12,6,4) were 40 ≤ C(12,6,4) ≤ 41. No 4-(12,6,1) covering with 40 blocks…
For a positive projection P on a Dedekind complete Banach lattice whose largest central operator below P is α id, Wickstead conjectured α must be 0 or 1/n for some natural n, and proved the finite-dimensional case. The paper proves the…
Escobar, Klein and Weigandt proved that gradedness of an ASM weak order interval, constancy of Coxeter length across its fibres, and equidimensionality of the associated ASM varieties are mutually equivalent, and conjectured (Conjecture…
Does every synchronizing one-cluster automaton on n states admit a reset word of length at most (n-1)^2? The new bound (m-1)(n-1) + mℓ ≤ (n-1)^2 settles the one-cluster case of the Černý conjecture.
The classes of SOP_2 and SOP_3 first-order theories coincide. This answers a question of Džamonja and Shelah from 2004.