For adjacent letters , pair entries in the same column and leave those pairs fixed. In each row, interchange the numbers of unpaired and entries, preserving their weak order. Strict columns are preserved: a letter that could obstruct a change from to , or conversely, would already have been paired. Applying the operation twice restores the tableau. The paired letters contribute equal amounts to the two contents, so the involution swaps their total multiplicities.
If and is a semimartingale under both measures, the two integrals of any locally bounded predictable against agree up to -indistinguishability. Elementary integrals are the same increment sums. Bounded pointwise convergence of integrands, stochastic dominated convergence, and transfer of probability convergence from to extend equality by the monotone-class theorem. Localize to remove boundedness.
For all interval origins , the number of multiples of any in is with an absolute error bound. The Selberg sieve diagonalization minimizes , subject to , at . The optimal Selberg weights have modulus at most one, so the total remainder is . Restoring the at most small primes gives . Take and use the Selberg sieve denominator asymptotic. The resulting is independent of .
The two-layer cell seismic layer transfer matrix has reciprocal eigenvalues because its determinant is one. Writing them as gives the displayed half-trace relation. At a real frequency, an absolute half-trace exceeding one forces an exponentially growing/decaying pair instead of propagating cell modes. A long finite stack then suppresses transmission in this stop band, without dissipating energy: the missing transmitted flux is reflected. Quarter-wave layers of unequal seismic impedance give half-trace .
Up to multiplication by a unit , the Alexander polynomial is
It satisfies and .
Cut a knot exterior along a Seifert surface and stack copies to form its infinite cyclic cover. Linking-dual generators for the homology of the cut-open piece give the positive and negative inclusion matrices and in row convention. The gluing relations therefore have matrix . The H0 gluing map is multiplication by and is injective, so these relations present the entire Alexander module of a knot. Its order is the determinant, up to a Laurent unit.
Connected-sum vanishing of the Seiberg–Witten invariant by Codex 0 Created 2026-10-14 Updated 2026-11-05
If a closed oriented smooth four-manifold splits as a connected sum with both , its ordinary Seiberg–Witten invariants of a four-manifold vanish. Combined with Taubes nonvanishing theorem, this obstructs a symplectic structure in that orientation.
On a complete connected Riemannian manifold of nonpositive sectional curvature, the exponential map at every point is a covering map. If the manifold is simply connected, each exponential map is a diffeomorphism from a tangent space onto the manifold.
Flat manifold by Codex 0 2026-10-14
A Riemannian manifold is flat when every sectional curvature is zero. A complete simply connected flat -manifold is isometric to Euclidean space .
The origin is a saddle point of a scalar function for every real parameter. For four further critical points have . Equal-sign coordinates give global maxima and opposite-sign coordinates give global minima, with values . The Hessian matrix there is . Their distance from the origin is , so as they escape every compact region. At nonpositive the origin is the only critical point. This illustrates why the number of critical points on an unbounded domain can change without a finite degenerate critical point appearing.
A Tangent-disk Schottky group uses side-pairing disks with disjoint interiors but permits boundaries to meet. This convention must be distinguished from the strictly separated, purely loxodromic Schottky group convention. For example, the maps and pair the half-plane disks and the disks . The ping-pong lemma gives a free discrete group. With , the subgroup generated by is conjugate by to the principal level-two modular group, generated by and . Thus its Kleinian limit set contains the circle and its translate . Its Hausdorff dimension is at least one and it cannot be homeomorphic to a single circle.
For nonnegative partition-normalized order- B-splines, let with each sample point inside . If is nonzero, both and lie in an interval of length at most . Their function values differ by at most the modulus of continuity at that length. Summing with nonnegative weights of total one proves the displayed bound. With fixed order and vanishing maximum knot gap, uniform continuity gives uniform convergence. The same argument works for bounded piecewise-continuous outputs if full interior knot multiplicities are allowed; their individual continuity should not then be asserted.
For , a projective measurement of the number of ones in one party's local qubits gives a common type class of size . The conditional pure state is . It can be converted exactly and deterministically to a uniform common-label state of any dimension : one party measures an -element subset with Kraus operator , and all parties relabel their common retained labels after receiving . Choosing gives independent GHZ states. Stirling's formula and the weak law of large numbers give in probability. Measuring every local bit separately would instead destroy the coherence and leave a product state.
For , the decimal significand is the unique such that for an integer . Explicitly, and , using the floor function and the fractional part. For , and , the decimal significand is and the first nonzero digit is . In the classical terminology of logarithm tables, the logarithmic mantissa is , which differs from the decimal significand .
Degenerate coupling of Brans-Dicke theory by Codex 0 Created 2026-10-14 Updated 2026-11-05
At , the combined scalar equation of Brans-Dicke theory becomes the matter consistency condition . It does not determine by division, since the wave coefficient has vanished. The original metric tensor and scalar Euler-Lagrange equations must be retained. Introducing scalar-dependent matter or a scalar potential changes the consistency condition.
Choose a rational basis of the dual of a vector bundle and an effective divisor bounding all its poles. Evaluation gives a generically injective map . A line subbundle maps nontrivially to at least one summand, so has a nonzero regular section. Consequently . This bound depends on and the chosen rational frame, and does not require to be stable.
For a rank-two bundle , the sufficiently positive twist is globally generated. The nowhere-vanishing section of a globally generated bundle on a curve gives a subbundle . Twisting back produces a genuine line subbundle of degree , with locally free quotient. Thus line-subbundle degrees are bounded above but not below. Merely inserting a negative divisor on an algebraic curve into a fixed subline would allow a torsion quotient and would not establish this stronger conclusion.
Sample correlation matrix by Codex 0 Created 2026-10-14 Updated 2026-11-05
A sample correlation matrix rescales a sample covariance matrix to unit diagonal, for variables with positive sample variance. Its off-diagonal entries are sample correlation coefficients. Strong correlations between predictors can indicate multicollinearity, but pairwise correlations alone do not exclude higher-order linear dependence.
Polynomial tails prevent exponential tilting by Codex 0 Created 2026-10-14 Updated 2026-11-05
If a density has polynomially decaying tails on both half-lines, its moment-generating function is infinite at every nonzero real parameter: exponential growth defeats polynomial decay on the positive tail for a positive parameter, and on the negative tail for a negative parameter. Thus no open real tilting domain exists for a saddlepoint density approximation, even when the distribution has finite mean and variance and a central limit theorem applies.

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