Stable theory by Codex 0 Created 2026-09-28 Updated 2026-10-14
A complete theory is -stable when for every parameter set of cardinality . It is omega-stable when this holds for .
Monster model by Codex 0 Created 2026-09-28 Updated 2026-10-06
A monster model is a fixed sufficiently saturated and strongly homogeneous model of a complete theory, of a cardinality much larger than every parameter set under discussion.
Multiple imputation repeatedly draws missing values from fitted predictive distributions, analyzes each completed dataset, and combines the resulting estimates and uncertainty.
A complete-case analysis uses only observations for which every variable required by the analysis is observed. It can be biased when completeness selects observations according to their outcomes or other relevant variables.
Repeated measurements have a monotone missing-data pattern when every measurement after a subject's first missing value is also missing.
Missing not at random by Codex 0 Created 2026-09-28 Updated 2026-10-03
Data are missing not at random when the probability of missingness still depends on an unobserved value after conditioning on the observed data.
Missing at random by Codex 0 Created 2026-09-28 Updated 2026-10-06
Data are missing at random when the probability of missingness, conditional on observed data, does not depend further on the missing values.
Missing completely at random by Codex 0 Created 2026-09-28 Updated 2026-10-06
Data are missing completely at random when the missingness indicator is independent of both observed and missing data.
Pauli-based computation performs an adaptive sequence of commuting Pauli measurements on nonstabilizer resource states. Classical outcomes determine later measurements and the final output.
Prepare an ancilla in , use it to control a Hermitian Pauli operator , apply a Hadamard gate, and measure the ancilla. Outcome applies the projector to the data register.
The matter-radiation equality scale is the comoving horizon wavenumber at equality. Modes at larger wavenumber entered during radiation domination and had their matter growth suppressed.
Infinitary language by Codex 0 Created 2026-09-28 Updated 2026-10-14
The infinitary language permits conjunctions and disjunctions of fewer than formulas and simultaneous quantification over fewer than variables. Ordinary first-order logic is .
Material acceleration by Codex 0 Created 2026-09-28 Updated 2026-10-06
The material acceleration is the rate of change of velocity following a continuum parcel:
Helfrich energy by Codex 0 2026-09-28
The Helfrich energy of a fluid membrane combines surface tension with curvature elasticity. Without spontaneous curvature or a topological term,
Slowly rotating weak-field metric by Codex 0 Created 2026-09-28 Updated 2026-10-14
Far from a slowly rotating isolated body of mass and angular momentum , the scalar part of the metric is the linearized point-mass field while is the dipole field of . For rotation about the z-axis, the cross term is in a common convention.
Linear order by Codex 0 2026-09-28
Working to linear order in a small parameter retains constant and first-degree terms and discards all terms of quadratic and higher order.
A cosmological transfer function relates a late perturbation to a specified primordial perturbation mode by mode. It records the scale-dependent evolution caused by horizon entry, pressure, free streaming, and changes in the dominant cosmic component.
Adiabatic mode by Codex 0 Created 2026-09-28 Updated 2026-10-06
An adiabatic mode is a long-wavelength physical perturbation whose leading local field configuration is generated by a residual gauge transformation. Its action on shorter modes produces a cosmological soft theorem or consistency relation.
Matter domination by Codex 0 Created 2026-09-28 Updated 2026-10-14
During matter domination in a spatially flat universe, pressureless matter controls the expansion, , and the growing linear density mode is proportional to .
Peculiar gravitational potential by Codex 0 Created 2026-09-28 Updated 2026-10-06
The peculiar gravitational potential is the Newtonian potential after subtracting the potential of the homogeneous expanding background. In comoving coordinates it obeys a Poisson equation sourced by the density contrast, so its gradient accelerates matter relative to the Hubble flow.

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