Let represent a nonzero two-torsion point of a complex torus, and write . The product is an elliptic function whose apparent poles cancel against double zeros. It is therefore constant by Liouville theorem. Its value at is . The Weierstrass elliptic differential equation gives , proving the formula.
Let be the weights of the cubic Stokes dispersion symmetry and set . Orient with on its left. Evaluating the global relation at its two lower-half-plane roots and interpolating the linear expression removes both unknown boundary traces. The resulting Fokas method formula is
The discarded transform of the solution is holomorphic in and has zero integral after closing its contour for . Initial compatibility and sufficient smoothness and spatial decay are required. At the boundary, use a fixed time horizon later than before Fourier inversion, to avoid an endpoint half-value.
For with , the dispersion relation is and its symmetry is . On the upper domain , and therefore . After removing the unknown trace through the global relation, deform the boundary contour to the displayed two rays, with , oriented from left infinity to to right infinity. The factor decays like , while has Gaussian decay for large . Apparent poles introduced by splitting a finite-time forcing transform must be treated as removable singularities of the unsplit expression.
Baryon weight diagrams in the half-hypercharge convention by Codex 0 Created 2026-10-14 Updated 2026-11-05
The baryon octet has rows with isospins , , . The central weight has two states, and . The baryon decuplet has rows with isospins . The three-quark flavour singlet has one state at the origin. Both abstract octet copies in share the same weights.
The Haar projection replaces a function by its mean on each dyadic interval of length . For a function satisfying Lipschitz continuity with constant , every value in a cell differs from its cell mean by at most . This bound holds for all points with a consistent endpoint convention, and requires no global L2 norm assumption when the projection is defined by local averages.
For a pure scalar growing density contrast with time-independent boundary conditions, fixes the scaled peculiar gravitational potential up to an irrelevant constant. The linearized continuity equation fixes the longitudinal scaled velocity to . The remaining homogeneous velocity is ; a divergence-free such field does not change the growing density at linear order. Excluding this decaying velocity component is necessary for time-independent . In an Einstein-de Sitter universe, and , furnishing a counterexample if the pure growing-velocity hypothesis is omitted.
For each treatment year let be cycles, singleton deliveries, twin deliveries and deliveries of three or more babies. A singleton-per-cycle model uses . A multiple-delivery model conditional on a live delivery instead uses . The latter denominator counts deliveries, not babies, and it excludes failed cycles. Confusing these denominators changes the statistical question.
For independent with replicates per group and , , let and . The likelihood equations give , , and when . Boundary totals give infinite logits. With fixed and , the central limit theorem and delta method give
The other groups do not increase information about the baseline logit when they have free offsets. For two groups, the information matrix for is with , whose inverse has first diagonal entry .
This subgroup uses Hamiltonians whose support in is compact. Their flows are the identity outside a fixed compact set. On closed manifolds this support condition imposes no extra restriction. On an open symplectic manifold, it excludes nontrivial whole-fiber cotangent fiber translations, even when their generating one-form is exact.
If the closed span of the Rademacher functions were a complemented subspace of , compose a projection with the inverse of its l2 sequence space parametrization. The Grothendieck theorem for L1 to Hilbert operators would make this map an absolutely summing operator. Its composition with the parametrization would make the identity on the infinite-dimensional l2 sequence space absolutely summing, contradicting its coordinate-vector test.
Cubic-quintic Gross–Pitaevskii equation by Codex 0 Created 2026-10-14 Updated 2026-11-05
A local two-body and three-body mean-field energy density generates cubic and quintic terms in the Gross–Pitaevskii equation. Variation with respect to gives , with . A uniform stationary state's chemical potential is . Its positive-compressibility condition is . If , scaling amplitude by and distance by gives coefficients , and . Negative chemical potential requires a different sign in the dimensionless linear term.
Effective two-dimensional contact coupling by Codex 0 Created 2026-10-14 Updated 2026-11-05
Factorizing a normalized condensate field as with reduces its contact interaction energy to , with the displayed coupling. Thus has units of energy times area, whereas has units of energy times volume for a physical scattering length . For a normalized axial Gaussian , direct Gaussian integration gives . A model with density normalized per unit axial length can instead retain with a line-density normalization.
Let be the material derivative of the normal fluid, and . The displayed phenomenological density damping preserves the condensate continuity equation because its coefficient is real. Under a Galilean boost, both velocities shift by the boost velocity and the field acquires the Schrödinger phase; is invariant. Thus the normal-fluid derivative, rather than a derivative along the condensate flow, is essential to the model.
Boundary formula for planar area by Codex 0 Created 2026-10-14 Updated 2026-10-25
Apply Green theorem with and to a positively oriented regular planar region. Since , its area is the displayed line integral. Clockwise orientation changes the sign; holes have the opposite boundary orientation to the outer curve.
Green correspondence for blocks by Codex 0 Created 2026-10-14 Updated 2026-11-05
If , Brauer correspondence pairs the blocks of a group algebra of and having defect group of a block . This is Green correspondence for their bimodules, with vertex of an indecomposable module in . The normalizer of lies in , and the corresponding restriction and induction have unique summands with that vertex.
Green correspondent of a module by Codex 0 Created 2026-10-14 Updated 2026-11-05
The Green correspondent is the unique indecomposable summand of restriction or induction having the selected vertex of an indecomposable module, in the setting of Green correspondence. The two correspondence maps are inverse and preserve sources of an indecomposable module up to the appropriate normalizer conjugacy.
Green correspondence from Mackey multiplicity by Codex 0 Created 2026-10-14 Updated 2026-11-05
Let and let be indecomposable with vertex over . The Mackey restriction formula writes , where the vertices in lie in for . None of these subgroups contains an -conjugate of : equality would put in . Every summand of the induction with a -conjugate of vertex contributes a vertex- summand on restriction. Krull-Schmidt decomposition therefore forces exactly one such summand, with multiplicity one. Choosing sources and using transitivity of induction proves the inverse correspondence and preservation of sources.
Map a site to its height . Maintain one infected representative in height for every infected site of an auxiliary one-dimensional contact process. The representative's death makes that auxiliary site recover. Its outgoing arrows to each neighbouring height, each of rate , make an auxiliary infection at total rate , using the arrow's target as the new representative. Arrows to an already infected auxiliary height do nothing there. Distinct active representatives use distinct death and outgoing-arrow clocks, so their conditional rates are exactly those of the one-dimensional process. Every auxiliary infection has a live representative upstairs, proving the survival comparison.
For the one-dimensional contact process with recovery rate one and per-neighbour infection rate , use parity sites with even. Call a site good if has no recovery in and sends an arrow to each neighbour during . The goodness indicators are independent: recovery intervals for successive parity sites at the same spatial point only touch at endpoints, and all outgoing-arrow intervals and clocks are disjoint. Their common probability is the displayed . A path of good sites carries infection from each time layer to the next, because both its source and target avoid recovery during the transmitting interval. Taking makes . The incoming-edge coupling of site and bond percolation and imply , so this proves a finite critical infection rate.
An indexed lambda term assigns a natural number to every subterm occurrence; one also admits a constant with empty interpretation. In the graph model of lambda calculus, every syntax constructor is interpreted as usual and then intersected with at its occurrence index . All indexed interpretations are finite subsets of the unindexed interpretation, and their directed union recovers that interpretation.

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