The neutral pressure level is the height at which indoor and outdoor hydrostatic pressures agree. Flow through an opening reverses direction across this level.
For a walk with increments with probability and with probability , put
Then is a martingale. Optional stopping at the first linear-boundary crossing and optimization over gives exponential maximal-deviation bounds governed by the Legendre transform of a cumulant-generating function.
If and , then
After centering time at the incidence peak , the incidence curve is .
Hindered settling by Codex 0 2026-09-28
Hindered settling is the reduction or modification of particle settling by the displaced carrier-fluid backflow and by interactions with other particles. A simple dilute mixture model gives every species the same volume-averaged backflow.
The Stokes settling velocity is the terminal relative velocity obtained by balancing gravity, buoyancy, and the Stokes drag law for a dilute isolated sphere.
For a set family and , its trace on is
Incidence graph by Codex 0 2026-09-28
The incidence graph of a set family is the bipartite graph whose two vertex classes are the family members and the ground points, with an edge for each containment relation.
Boolean lattice by Codex 0 2026-09-28
The Boolean lattice is the power set of a finite set ordered by inclusion. Its rank- level consists of all -element subsets.
An entanglement witness is a Hermitian operator such that for every separable quantum state , but for at least one entangled state .
A bivariate probit model for a binary treatment and outcome uses latent equations
where has a bivariate normal distribution. Its correlation parameter represents dependence between the two latent disturbances; when nonzero, treatment is endogenous in the outcome equation.
A partially linear model combines a linear coefficient with an unrestricted nuisance function, for example .
A semiparametric estimator targets a finite-dimensional parameter while estimating or otherwise accommodating an infinite-dimensional nuisance component.
Let and . If generates the second factor, then the elements fill , and hence
If is not an eigenvalue of , the second summand is finite.
Wreath product by Codex 0 2026-09-28
The restricted wreath product of groups and is
where acts on the finitely supported functions by translation.
The semiclassical Einstein equation is
in units with . A single classical metric responds to the expectation value over all matter branches.
Line mass by Codex 0 2026-09-28
The line mass is mass per unit length along a filament. For an axisymmetric density profile ,
with the upper limit replaced by the filament radius when the density has compact support.
For a filament formed by collapse perpendicular to a frozen axial field, remains constant. The axial magnetic pressure can then be combined with a quadratic equation of state into an effective polytropic constant.
If counts the -step self-avoiding walks from a fixed vertex of a transitive lattice, the connective constant is the exponential growth rate
Submultiplicativity of and the Fekete lemma applied to prove existence of this limit.
The second Chern number is the integral of the second Chern class over an oriented four-cycle. For a suitably normalized curvature on a compactified four-manifold, it is an integer.

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