For with and , is equivalent to the displayed chance constraint, because the standard normal distribution function is continuous and strictly increasing. The coefficient is a standard normal quantile, which can be negative. If , equality is an atom and the exact condition becomes instead.
A deterministic demand has probability one of meeting or exceeding its mean. Thus replacing a positive-variance Gaussian chance constraint by its naive zero-variance limit with a non-strict capacity inequality loses the boundary condition. The example , , satisfies for finite , but violates the chance requirement.
Coreflexive pair by Codex 0 Created 2026-10-07 Updated 2026-10-14
A coreflexive pair has a common retraction with . It is the dual of a reflexive pair. Both and are split monomorphisms.
Gamma-convergence by Codex 0 Created 2026-10-07 Updated 2026-10-14
A sequence of functionals Gamma-converges in a specified topology when every convergent satisfies , and each has a recovery sequence with . With appropriate compactness of energy sublevels, limits of approximate global minimizers minimize , and the minimum values converge. This is suited to variational approximation such as the Ambrosio–Tortorelli approximation; it does not describe arbitrary local minima.
Worldvolume by Codex 0 2026-10-07
The worldvolume is the history of a brane. An embedding maps its local coordinates into target spacetime. A string worldvolume is a worldsheet.
Brane tension by Codex 0 Created 2026-10-07 Updated 2026-10-14
The brane tension is the energy per unit spatial brane volume and multiplies its geometric action. In units , a -brane tension has mass dimension . The case is the string tension.
For the normalized isotropic cutoff model, collisions redistribute the direction of relative velocity uniformly while keeping its length. With center and relative speed , outgoing velocities are . Momentum and kinetic energy are preserved, and the collision rate has no relative-speed factor. The displayed operator uses unit total angular rate. General Maxwell molecule kernels can have nonconstant angular dependence.
The integral uses when it is defined. For the Boltzmann equation, the Boltzmann H theorem makes it nonincreasing under suitable regularity and integrability. This functional is distinct from the microstate-counting Boltzmann entropy; the physical kinetic entropy has the opposite sign.
For equal-mass elastic collisions, one reflection parametrization is and . The fixed- transformation preserves pairwise momentum, kinetic energy and velocity-pair measure. A nonnegative kernel invariant under particle interchange and collision reversal yields a gain-loss operator. Its weak Boltzmann collision identity proves conservation and its entropy identity proves the Boltzmann H theorem. Unlike the Maxwell molecule collision operator, this general kernel may depend on relative speed.
When the velocity distribution is independent of position and there are no forces, the free transport equation contributes zero and only collisions evolve . For a bounded cutoff kernel, gives local existence and uniqueness by the Banach fixed-point theorem. Positivity and mass conservation bound the norm and permit global continuation in this particular model. Stronger kernels require moment or weighted estimates.
In a scaling with small Knudsen number, the leading collision balance formally forces a local Maxwellian. The conserved moments then give the Euler equations with a monatomic ideal-gas closure. The next nonequilibrium correction produces viscous and heat-conduction terms. These substitutions are formal: rigorous limits need uniform estimates, initial and boundary conditions, and sufficient convergence.
A weak solution framework in which a suitable nonlinear transform satisfies a transport equation with transformed collision source , interpreted with the required integrability and possible framework-dependent defect terms. Renormalization addresses distributions whose raw collision term is not integrable enough to support the ordinary weak formulation. This is different from a classical smooth solution and does not by itself imply smooth global well-posedness.
Generalized Bernoulli number by Codex 0 Created 2026-10-07 Updated 2026-10-13
For a Dirichlet character of conductor , define the generalized Bernoulli numbers by
They express special values of Dirichlet L-functions at nonpositive integers and occur in the interpolation formula for Kubota-Leopoldt p-adic L-functions.
Bell pair by Codex 0 Created 2026-10-07 Updated 2026-10-13
A Bell pair consists of two qubits prepared jointly in a Bell state. It is a maximally entangled two-qubit resource with Schmidt rank two. Two independent Bell pairs have resource Schmidt rank four across the same party partition.
This barotropic pressure potential obeys for a barotropic fluid. It gives the pressure contribution to a steady Bernoulli equation. In isentropic thermodynamics it agrees with specific enthalpy up to a constant; for an externally maintained isothermal ideal gas it is and is not the constant thermodynamic enthalpy at fixed temperature.
Barotropic spherical accretion equation by Codex 0 Created 2026-10-07 Updated 2026-10-13
Steady spherical continuity equation gives . Combining this with Euler equations for an inviscid fluid and gives the displayed equation. Smooth transonic passage requires and simultaneously. The barotropic enthalpy function gives the integral .
Large roots near tangent poles by Codex 0 Created 2026-10-07 Updated 2026-10-13
For fixed real , roots of tending to positive infinity approach tangent poles . Expanding gives
The expansion works for either sign of when , but is nonuniform at , where the roots lie at instead. The pole labeling need not equal the ordered root index at small .
Uniformly rotating barotropic star by Codex 0 Created 2026-10-07 Updated 2026-10-13
In a connected inviscid uniformly rotating barotropic fluid, momentum balance makes the displayed sum constant. The pressure term is the barotropic enthalpy function. Perturbations experience Coriolis acceleration, and their rotating-frame frequency depends on the chosen exponential sign convention.
Hankel representation of thin-disk gravity by Codex 0 Created 2026-10-07 Updated 2026-10-13
For an axisymmetric reflection-symmetric thin disk, the Laplace equation in cylindrical coordinates separates into regular radial Bessel functions and vertical decaying exponentials. The divergence theorem imposes . Hankel transform inversion gives . Its radial derivative gives the galaxy rotation curve. Infinite scale-free models may require subtracting an additive divergent constant.

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