Assume minimizes scalar total variation denoising for . The data may be unbounded. For the local flow of , use as two competitors. The total variation under opposite smooth flows and convexity of the total variation seminorm bound the sum of regularizer changes by . Minimality and the opposite-flow fidelity identity for quadratic data, evaluated using the BV jump-product limit with one bounded factor, imply
Let . The integrands define finite signed Radon measures, since is bounded and the jump variation of is finite. Arbitrary nonnegative smooth make their densities nonnegative. Testing every coordinate direction removes the factor and proves the stated inequality.
For scalar total variation denoising with on a bounded Lipschitz domain in arbitrary dimension, the reconstructed jump set of a bounded-variation function lies in the data jump set of a bounded-variation function up to a surface-null set. The jump-amplitude inequality for total variation denoising proves this: outside , the two BV traces on a hypersurface of agree, so forces . Surviving jumps cannot be stronger than the corresponding data jumps and must have the same orientation. Existing jumps may disappear.
The proof uses scalar total variation splitting under clipping, residual-preserving clipping of an ROF minimizer, total variation under opposite smooth flows and the BV jump-product limit with one bounded factor. It requires neither bounded data nor bounded output. The bounded-forcing geometric proof through noncontact of ROF level boundaries remains an alternative for bounded images; it is not used to infer regularity under unbounded forcing.
Ferrero-Washington theorem by Codex 0 Created 2026-10-07 Updated 2026-11-05
For a finite abelian extension of , the unramified Iwasawa module of its cyclotomic Zp-extension has . This removes -power elementary factors from its characteristic ideal. The theorem does not assert for arbitrary noncyclotomic Zp-extensions.
For a finitely generated module over the integral domain , its Iwasawa-module rank counts free summands up to pseudo-isomorphism. Rank zero is equivalent to being a torsion module. A positive rank forces the -ranks of finite-layer coinvariant modules to grow like .
Pseudo-isomorphism by Codex 0 Created 2026-10-07 Updated 2026-11-05
A homomorphism between finitely generated one-variable Iwasawa modules is a pseudo-isomorphism if its kernel and cokernel are finite. Finite errors do not change the Iwasawa-module rank or the characteristic ideal of a torsion module. They can still change its integral structure, so a pseudo-isomorphism is weaker than an isomorphism.
On an integral scheme , every nonempty open contains its generic point . Taking a germ gives an injective ring homomorphism from its regular functions to the function field . Injectivity follows on each nonempty affine open subscheme from the injection of an integral domain into its field of fractions, and then from the sheaf gluing axiom. This lets regular functions on different open subsets be compared inside one field.
Homotopy sphere by Codex 0 Created 2026-10-07 Updated 2026-10-14
A homotopy sphere is a closed manifold with the homotopy type of a sphere of the same dimension. In dimensions at least two, a closed simply connected integral homology sphere is a homotopy sphere: successive applications of the Hurewicz theorem produce a map from the sphere inducing an isomorphism on integral homology, and the homological Whitehead theorem makes it a homotopy equivalence. The topological generalized Poincare theorem identifies its topological type, while prescribed smooth structures require a separate question.
In multiplicative resource-price dynamics, a zero price remains zero even if demand exceeds supply there. For one route using two resources, unit weight and supplies , both and are equilibria, while the unique positive equilibrium is . Thus uniqueness on the positive price domain cannot be extended to every nonnegative price trajectory without an extra boundary rule.
For finite nonempty routes and positive weights, the potential of increasing-supply resource-price dynamics has a unique maximum. Increasing supplies give a linear penalty at large prices, so its superlevel sets are compact, and logarithmic route terms exclude zero route totals. Used resources have uniformly positive demand on a trapped set; a sufficiently small positive price therefore increases, giving a positive lower bound. The potential derivative is . It has finite integral and is uniformly continuous, so it tends to zero by uniformly continuous integrable functions vanish at infinity. Every limit point then satisfies the unique stationary equations. Unused resource prices decay to zero. Only continuity and strict increase of the supply functions are needed.
For a sequence of positive integers, the nested closures of its tail finite-sums sets have nonempty compact intersection in the Stone-Čech compactification of the natural numbers. This intersection is a subsemigroup. For a sum from one tail, all sums supported beyond a chosen finite representation of lie in that tail translated by . The ultrafilter addition formula then establishes closure under addition. The Ellis–Numakura lemma supplies an idempotent ultrafilter containing every tail finite-sums set and hence any set containing the full finite-sums set.
Combine the full quasi-steady Stefan condition above with , and the Darcy flow law to obtain an implicit pressure-growth system. Even when latent heat is negligible, a conductivity ratio changes the leading molecular driving pressure by . Thus a reduced equal-conductivity formula requires an explicit material and rate approximation.
For , set to get . The displayed solution approaches the stable equilibrium . From the formal zero start it behaves as at early times and at late times. The zero-start asymptote is an intermediate reduced-model regime, since the physical thin-film approximation fails at vanishing ice thickness.
The hook graph is the Young diagram with the hook length written in each box. It displays the hook product and thus the hook-length formula for the corresponding Specht module. This use of the name is recorded in Frame, Robinson and Thrall's original hook-graph paper; it refers to a labeled array, not a directed hook-walk graph.
Holonomy around circular fibres by Codex 0 Created 2026-10-07 Updated 2026-10-14
For the Riemannian metric , where and has period , parallel transport around acts on the orthonormal basis components of a tangent vector by a rotation through . Indeed, those components obey and as functions of . Thus all tangent vectors return to themselves exactly when . The integer criterion concerns holonomy and is stronger than local flatness.
If the Holm step-down procedure makes a false rejection, it must reject the first true null in the ordered list. All true nulls remain at that step, so its cutoff is at most . The union bound on their marginally valid p-values gives familywise error rate at most . This proves strong control under arbitrary dependence, and super-uniformity suffices.
Quadratic Hilbert symbol by Codex 0 Created 2026-10-07 Updated 2026-11-05
The symbol is one exactly when is a norm from , and is always one if is square. Equivalently the conic is isotropic. This proves symmetry. The cyclic local norm index makes the norm subgroup have index two for nonsquare , proving bilinearity and nondegeneracy on local square classes. Also and .
Exterior multiplication by the fundamental -form of a Hermitian manifold raises bidegree by . Its pointwise formal adjoint lowers bidegree by . On a Kähler manifold this is the Lefschetz operator of a Kähler manifold, but its pointwise algebraic properties do not require the form to be closed.
A small abundance displacement from the helium-3 equilibrium abundance obeys to linear order. Rapid relaxation relative to background evolution allows the abundance to track its equilibrium. If the equilibrium drifts, the displacement equation also contains . In the pp-I limit the rate is , so both production and destruction temperature dependences matter.

Pinned article: Introduction to the OurBigBook Project

Welcome to the OurBigBook Project! Our goal is to create the perfect publishing platform for STEM subjects, and get university-level students to write the best free STEM tutorials ever.
Everyone is welcome to create an account and play with the site: ourbigbook.com/go/register. We belive that students themselves can write amazing tutorials, but teachers are welcome too. You can write about anything you want, it doesn't have to be STEM or even educational. Silly test content is very welcome and you won't be penalized in any way. Just keep it legal!
We have two killer features:
  1. topics: topics group articles by different users with the same title, e.g. here is the topic for the "Fundamental Theorem of Calculus" ourbigbook.com/go/topic/fundamental-theorem-of-calculus
    Articles of different users are sorted by upvote within each article page. This feature is a bit like:
    • a Wikipedia where each user can have their own version of each article
    • a Q&A website like Stack Overflow, where multiple people can give their views on a given topic, and the best ones are sorted by upvote. Except you don't need to wait for someone to ask first, and any topic goes, no matter how narrow or broad
    This feature makes it possible for readers to find better explanations of any topic created by other writers. And it allows writers to create an explanation in a place that readers might actually find it.
    Figure 1.
    Screenshot of the "Derivative" topic page
    . View it live at: ourbigbook.com/go/topic/derivative
  2. local editing: you can store all your personal knowledge base content locally in a plaintext markup format that can be edited locally and published either:
    This way you can be sure that even if OurBigBook.com were to go down one day (which we have no plans to do as it is quite cheap to host!), your content will still be perfectly readable as a static site.
    Figure 5. . You can also edit articles on the Web editor without installing anything locally.
    Video 3.
    Edit locally and publish demo
    . Source. This shows editing OurBigBook Markup and publishing it using the Visual Studio Code extension.
  3. https://raw.githubusercontent.com/ourbigbook/ourbigbook-media/master/feature/x/hilbert-space-arrow.png
  4. Infinitely deep tables of contents:
    Figure 6.
    Dynamic article tree with infinitely deep table of contents
    .
    Descendant pages can also show up as toplevel e.g.: ourbigbook.com/cirosantilli/chordate-subclade
All our software is open source and hosted at: github.com/ourbigbook/ourbigbook
Further documentation can be found at: docs.ourbigbook.com
Feel free to reach our to us for any help or suggestions: docs.ourbigbook.com/#contact