Edition 1
Scott Schubr
- Primary subject
- Mathematics
- Subject subfield
- Analysis and Spectral Theory
- Paper type
- Research Article
- Manuscript stage
- Preprint
We determine the leading eigenvalue-counting asymptotic for a class of infinite-volume Dirichlet tubes confined by diverging twisting. The planar cross-section is a compact annular polar strip with positive C¹ angular width α(r) < 2π, and the twisting speed is c(1 + s²)^(p/2), where c, p > 0. We prove N(Λ) ∼ CΛ^(3/2 + 1/(2p)) and compute C explicitly in terms of ζ(1 + 1/p) and ∫ rα(r)^(1 + 1/p) dr. The proof retains the angular Dirichlet modes while treating the radial and longitudinal variables semiclassically. A uniform Dirichlet-box comparison obtained from quasiperiodic phase averaging and IMS localization controls the artificial longitudinal boundaries. A separate tail estimate and absolute-coefficient freezing justify the global limit. The result gives a concrete-class answer to the Weyl-asymptotics question for tubes with asymptotically diverging twisting.
Edition 1
Scott Schubr
- Primary subject
- Mathematics
- Subject subfield
- Analysis and Spectral Theory
- Paper type
- Research Article
- Manuscript stage
- Preprint
We study nonnegative initial temperatures whose Dirichlet heat evolution has one common signed outward normal derivative on both boundary components of a fixed spherical shell. In every dimension at least two, the admissible observation times form an interval (0, τ) with a finite, unattained endpoint characterized by a boundary heat-kernel ratio. Finite schedules satisfy an exact interior convex-hull criterion, and a datum-independent terminal interval contains at most one observation.
With unit ground-state projection, every weighted minimum-Lq preparation, 1 < q < ∞, is unique at each admissible time and is determined by a monotone real scalar moment equation. We obtain sharp cost constants throughout the fixed norm scale, including separate endpoint arguments. For every finite strictly convex power, quantitative ground-probability stability prevents scaled second-moment loss, and physical near-minimizers have a universal strong rescaled profile with angular symmetry. Exactly feasible counterexamples exclude universal higher-moment convergence.
At the L1 endpoint the ground-weighted probabilities concentrate at √6 in quadratic Wasserstein distance. At the cap endpoint the preparations approach a filled layer in every finite Lr, while an exact counterexample excludes general strong L∞ convergence. All parameters are fixed in the stated asymptotic limits; classical positivity, convex-moment and coupling methods are explicitly credited.
Edition 1
Scott Schubr
- Primary subject
- Mathematics
- Subject subfield
- Analysis and Spectral Theory
- Paper type
- Research Article
- Manuscript stage
- Preprint
For every dimension d >= 2 and every measurable spatial weight w >= 1 essentially bounded on bounded sets, we construct a connected tower of enlarging cubes whose ordinary Dirichlet Laplacian has a complete orthonormal eigenbasis and essential spectrum [0,infinity). Given any finite nondecreasing r(E) >= 1 tending to infinity, the tower can be chosen so that weighted local-source evolution below energy E is bounded uniformly in time by C_K min(r(E),sqrt(E+1)). More generally, any prescribed Borel spectral filter 0 < h <= 1 uniformly vanishing at high energy admits a uniform weighted local-source bound. Local Neumann approximation targets and a summable spectral-projection budget supply the uniform source estimate. With a rational initial room, computable local weight upper bounds and a supplied computable filter-tail modulus, the geometry and its finite spectral certificates can be produced by a procedure terminating at every stage. Crack-aware primal and flux approximation certify whole-resolvent compressions and strict whole-cluster spectral tests. Explicit sufficient aperture bounds are logarithmic in the plane and linear in higher dimensions. For uniformly diverging spatial weights, a uniformly bounded all-energy factor is impossible; the geometry depends on the prescribed rate.
Edition 1
Scott Schubr
- Primary subject
- Mathematics
- Subject subfield
- Analysis and Spectral Theory
- Paper type
- Research Article
- Manuscript stage
- Preprint
We study the intrinsic Wasserstein metric on affine Fourier-density models on the unit circle. For three distinct frequencies, with one arbitrary fixed phase per frequency, every sectional curvature at the uniform density is strictly negative unless the frequencies have ratio 1:2:3. In that exceptional family we determine the exact attained curvature range and a phase-dependent sign criterion: the same frequency magnitudes can have mixed curvature or strictly negative curvature solely through relative phase. For the aligned four-frequency family {m, 2m, n, n+m}, n > 5m, we determine the exact attained maximum sectional curvature at every frequency ratio. Two sharp algebraic thresholds separate mixed signs from strict negativity and then mark saturation of the maximum at −18π²m². Finally, exact rational Fourier integration with a bounded infinite reciprocal-series remainder certifies nonuniform closed parameter cubes: the {m, 2m, 3m} model has both signs throughout [−.01, .01]³, whereas every sectional curvature of the {m, 2m, 4m} model is less than −.98π²m² there. The phase and four-frequency classifications are analytic; the explicit neighborhood bounds are computer-assisted and accompanied by reproducible exact-arithmetic certificates.
Edition 1
Scott Schubr
- Primary subject
- Mathematics
- Subject subfield
- Analysis and Spectral Theory
- Paper type
- Research Article
- Manuscript stage
- Preprint
We construct bounded connected nonconvex planar pentagons for which the affine 2-Laplacian has a strictly positive Dirichlet eigenfunction at an eigenvalue strictly above its first variational eigenvalue. The same domain therefore supports positive affine eigenfunctions at two distinct values. The construction gives a negative answer, for n = p = 2, to the general-domain positive-eigenfunction question of Haddad, Jiménez and Montenegro. The mechanism is an affine-isotropic saddle formed by pinching a pentagon into two right isosceles triangles. A symmetry-preserving diagonal normalization has positive curvature, while a shear couples the ground state to a nearly coincident odd mode. We prove the sharp limit (λ₂ − λ₁)∂qqλ₁ → −32768/81 at the isotropic positions. An area-preserving apex slide has the corresponding limit −50π⁴. The saddles persist under small vertex perturbations, including examples with nonparallel convex-hull sides. Consequences include distinct isotropic positions on one linear orbit and failure of positive-definite-deformation log-convexity outside convexity.
Edition 1
Scott Schubr
- Primary subject
- Mathematics
- Subject subfield
- Analysis and Spectral Theory
- Paper type
- Research Article
- Manuscript stage
- Preprint
For every dimension d ≥ 2, we construct a connected quasi-conical open set whose Dirichlet Laplacian has a complete orthonormal basis of eigenfunctions and spectrum [0, ∞). The domain is a tower of adjacent enlarging cubes joined through positive windows tending to zero. Cube sizes and windows are chosen together. The construction gives an affirmative existence answer to the singular-continuous-spectrum question raised for this geometry by Krejčiřík and Lotoreichik and repeated in a recent spectral-geometry survey. At each finite attachment we continue a nested family of whole spectral clusters, including their multiplicities. A summable projection budget and a refreshed dense family of test vectors make the limiting finite-dimensional reducing subspaces complete. We also obtain a room-index L² tail bound and retain the possibility of placing one prescribed positive embedded eigenvalue by dilation.
Edition 1
Scott Schubr
- Primary subject
- Mathematics
- Subject subfield
- Analysis and Spectral Theory
- Paper type
- Research Article
- Manuscript stage
- Preprint
A sharp integrated concentration comparison is proved for heat flow on finite compact connected metric graphs with a nonempty Dirichlet vertex set and standard Kirchhoff conditions elsewhere. The comparison with the mixed interval of equal total length applies to every nonnegative square-integrable initial datum. For initial datum one, it yields an all-times heat-content bound and characterizes equality at a single positive time. An exact positive-kernel deficit representation and a separate convolution formula for an asymmetric three-edge pitchfork accompany the proofs.