For unit-rate Erlang distribution of shape two claims put . The adjustment coefficient satisfies , so . In the interior-adjustment prefactor , substituting gives the displayed expression. It is positive for and tends to one as the loading tends to zero.
An ideal planar alpha-Omega dynamo places poloidal regeneration above an interface and shear-generated toroidal induction below it. With equal constant diffusivities, decay away from the interface and ordinary electromagnetic matching, its surface-wave branch grows when for positive . The model separates the two regeneration regions while allowing diffusive coupling. The threshold refers to this model, not every solar interface dynamo or a full isotropic alpha closure.
Write the old nuisance parameter as with . The transformed score functions are and . Their expected cross product is . Setting it to zero gives the displayed ordinary differential equation along fixed- curves, assuming positive nuisance Fisher information. Smooth solutions with distinct initial conditions give a local interest-respecting orthogonal coordinate system.
For a stationary autoregressive process of order one with unit-variance normal distribution marginals and fixed , the Gaussian kernel covariance correction at lag has the displayed form. The difference of two observations has variance , and their characteristic functions reduce the Fourier integral to the difference of two Gaussian integrals. The mean value theorem gives , uniformly over . Thus the integrated variance differs from its independent-sample counterpart by . The marginal bias is unchanged, so this dependence does not alter the leading optimal bandwidth or the mean integrated squared error for a second-order density kernel.
Rees-Sciama effect by Codex 0 Created 2026-10-14 Updated 2026-10-20
The Rees-Sciama effect is the microwave temperature shift produced by time-dependent gravitational potentials in nonlinear structure. A photon gains energy entering a potential well and loses it leaving; the shifts do not cancel when the well changes during transit. To leading order in its effect on the photon spectrum, this is a frequency-independent thermodynamic temperature shift, unlike the thermal Sunyaev-Zeldovich effect. A nonlinear potential can evolve even during matter domination, when linear growing-mode potentials are constant.
Suppose the instantaneous forward rate field has mean and covariance , with deterministic initial curve and suitable integrability and maturity regularity. Its discounted zero-coupon bond prices are martingales exactly when the displayed mean identity holds. Put
The discounted bond price is , where is the integrated Gaussian forward-rate process. Its conditional Gaussian exponential expectation gives the equivalent identity . Differentiating this in maturity gives the displayed restriction. Conversely, integrating that restriction on the diagonal and along the current curve recovers the half-variance identity, by symmetry of the covariance over the maturity square. The Gaussian exponential martingale with deterministic variance then verifies the full conditional martingale property. This formulation does not require a time derivative of .
Scaled Heisenberg lattice by Codex 0 Created 2026-10-14 Updated 2026-11-05
For a positive integer , in the real Heisenberg group with multiplication , the displayed set is a discrete cocompact subgroup. Writing , , gives and central. Hence its abelianization is . The right quotient maps to by its first two coordinates; each fibre is the central circle .
For , a spherical ultraviolet cutoff gives the following exact examples of the one-loop critical-mass subtraction integral:
The areas of the unit spheres in dimensions three, four and five are , and . Dividing by reduces the integrals to constants times , and respectively. Elementary integration proves the formulas. As , the first has a power divergence, the second a logarithmic divergence, and the third a finite limit. These examples make the ordinary upper critical dimension four visible without treating a self-consistent one-loop equation as an exact interacting critical exponent prediction.
Design sensitivity function by Codex 0 Created 2026-10-14 Updated 2026-11-05
The sensitivity function is the normalized variance of a fitted regression mean. Its average under the design is the number of model coefficients, since . The directional derivative of towards a point mass at is .
For a zero-one Boolean function, the flip-probability influence is . Apply Beckner's inequality with noise parameter to the discrete derivative of a Boolean function, whose nonzero magnitude is . Its norm squared is . Summing over coordinates gives the displayed weighted Fourier weight bound, a useful intermediate step in influence lower bounds.
Hessian criterion for a flex by Codex 0 Created 2026-10-14 Updated 2026-10-25
For a plane curve defined by a homogeneous polynomial of degree , assume the field characteristic is different from two and is nonzero in the field. A smooth point of a variety is a flex exactly when the determinant of the homogeneous Hessian matrix vanishes there, provided its tangent line is not a component. Put the point at with tangent and . The homogeneous identities give and , so the determinant is . In the completed local ring, write the curve as a formal power series . Its linear coefficient is zero and its quadratic coefficient is . Vanishing of that coefficient is exactly intersection multiplicity at least three with the tangent, proving the criterion in these positive characteristics as well as in characteristic zero.
For a smooth homogeneous cubic in characteristic zero, its plane cubic flexes are precisely its intersections with the determinant of its Hessian matrix. Choose coordinates with a given smooth point and its tangent . Up to a nonzero coefficient, the cubic starts as plus cubic terms in . Its tangent contact has order three exactly when , and the Hessian determinant at the point is a nonzero constant times . This proves the criterion.
Pt100 by Codex 0 Created 2026-10-14 Updated 2026-11-05
A Pt100 has nominal electrical resistance at .[ref] Here is the reference for the nominal element designation; it is distinct from the water triple point used in SPRT calibration. The following Pt100 local linear model deliberately stipulates one approximate response for calculations.
Use the binary finite-set encoding and Cantor code . Contracting gives the substituted body with its root index lowered by taking the minimum with , replacing each occurrence by a copy of with root index . A zero-indexed abstraction instead substitutes and gives the body root index zero. Indices strictly budget the argument information that can be used by application. Finite-witness inequalities for the pairing code prove that indexed reduction increases the interpretation, although it can decrease the underlying Böhm tree.
Transitive increasing event by Codex 0 Created 2026-10-14 Updated 2026-11-05
An increasing event on a finite product of identically distributed coordinates is transitive if a group action preserving the event is transitive on the coordinate set. Its influences are all equal. Transitivity concerns coordinates, and does not assert transitivity on successful configurations.
Sharp threshold by Codex 0 Created 2026-10-14 Updated 2026-11-05
For a sequence of nontrivial increasing events on finite product measures, write for the parameter at which the success probability is . An additive sharp threshold means that for every fixed . When the threshold parameter itself tends to zero, relative sharpness instead compares this window with ; additive sharpness alone is then a weaker assertion. The Friedgut-Kalai sharp threshold theorem provides an explicit additive bound for transitive increasing events.
Concurvity by Codex 0 2026-10-14
Concurvity is the nonlinear analogue of multicollinearity: a function of one predictor is exactly or approximately expressible as a sum of functions of other predictors. Exact concurvity can make an additive decomposition nonunique; approximate concurvity makes components difficult to estimate stably. A unique fitted sum need not imply unique individual components.
Self-similar ice-bearing wall plume by Codex 0 Created 2026-10-14 Updated 2026-11-05
In a dilute, well-mixed wall line plume, let be its width, its upward velocity, its ice volume fraction, and its one-edge entrainment coefficient. Define from the liquid and ice mass densities. The mixture's reduced gravity is approximately , so itself is a material density-contrast scale, not the changing mixture reduced gravity.
Neglect crystal slip, deposition and other buoyancy contributions. If the ice-bearing wall-plume thermodynamic invariant supplies a constant positive ice flux , then volume flux and kinematic momentum flux obey
A constant-velocity solution has with measured from its plume virtual origin. Substitution gives
Its width grows linearly and ice fraction falls inversely with height. Two exposed entraining edges replace by . The formal origin lies outside the dilute model because the ice fraction diverges there; finite-source conditions require matching away from that origin.
Let be a nonempty positive-dimensional compact complex submanifold of Complex projective space. On a positive-dimensional connected component choose a hyperplane meeting, but not containing, that component. Its linear equation gives a holomorphic section of with a zero and with a nonzero value. For , its th power cannot be a section of a trivial holomorphic line bundle, since such sections are constant on the compact connected component. Negative powers are also nontrivial by duality. Every positive-dimensional compact projective component meets every hyperplane: otherwise its affine coordinate functions would all be constant.
Hyperplane class by Codex 0 2026-10-14
The First Chern class of the hyperplane line bundle. On Complex projective space it generates degree-two integral cohomology, and on its top power evaluates as one on the complex-oriented fundamental class.

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