Gravitino-induced torsion by Codex 0 Created 2026-10-14 Updated 2026-11-05
With canonical Rarita-Schwinger field normalization, one convention gives the displayed torsion tensor. Its contorsion tensor is . The algebraic spin connection equation determines ; substituting it in the action produces four-fermion terms. This is an instance of Einstein-Cartan theory and is efficiently varied using the 1.5-order formalism. A rescaled gravitino changes the displayed coefficient.
A four-dimensional Majorana spinor gravitino has real components, minus four local supersymmetry gauge functions, leaving twelve before using any Euler-Lagrange field equation. A vierbein has sixteen real components, minus six local Lorentz transformation and four diffeomorphism gauge functions, leaving six. Equivalently, a symmetric metric tensor has . The propagating graviton and massless gravitino each have two states on shell. Six bosonic auxiliary field components complete an off-shell supergravity multiplet.
Old-minimal supergravity by Codex 0 Created 2026-10-14 Updated 2026-11-05
Old-minimal four-dimensional supergravity adds a complex scalar and a real vector to the vierbein and gravitino. These six real bosonic auxiliary field components have no propagating kinetic terms. They balance the off-shell component count of minimal supergravity and permit the local supersymmetry algebra to close without imposing the propagating Euler-Lagrange field equations.
A compatible triple patches to . It is finitely generated projective and recovers after extension of scalars. For free modules glued by , the block identity lifts through the surjective side and makes the direct sum with inverse gluing free. Complements reduce general projective triples to that free case. Conversely an idempotent over is exactly a compatible pair of idempotents over its two factors.
The diagonal maps are extension of scalars; the maps to are differences. The connecting map sends to the difference of its patched free module and the corresponding free -module. Elementary lifting and common free stabilization prove exactness at every internal term. The displayed fragment does not assert injectivity at its first term or surjectivity at its last.
Cyclotomic Milnor square by Codex 0 Created 2026-10-14 Updated 2026-11-05
Evaluation of the cyclic generator at and at a primitive th root gives the displayed pullback. The maps to the common field reduce integers modulo and set . If a representative polynomial for the second component has value at one, adding an integer multiple of adjusts that value by a multiple of without changing the second component. This proves surjectivity onto compatible pairs.
Apply the midpoint quadrature rule on each of equal panels of a partition of an interval, with :
Each quadrature node is a panel midpoint and each quadrature weight is . For , put . Summing the panel quadrature errors gives
for some . Each panel contributes at most ; there are panels, explaining the composite midpoint rule error of order in big O notation. On a nonuniform partition of an interval with panel widths and largest width , the corresponding bound is .
For on , summing the sampled polynomial exactly yields
Doubling divides the absolute error by exactly four. For a general function, halving divides the displayed error bound by four, but the actual absolute error need not follow that ratio: cancellation can make it smaller or zero. Continuous functions still give convergence as the largest panel width tends to zero, by uniform continuity; without the bounded second derivative, the second-order rate is not guaranteed. Noise sensitivity of a quadrature rule explains a separate limitation when samples are inexact.
For a free complex scalar field, independent particle annihilators and antiparticle creators give
The invariant mass shell integral vanishes at spacelike separation: transform to equal time, then reverse the spatial momentum in one term. Retaining only the particle-annihilation term would leave a Wightman function, which is generally nonzero even at spacelike separation. Thus both frequency branches are needed for a local relativistic field. For a real scalar field, the creation term supplies the same cancellation but creates the same self-conjugate particle species.
Double every edge of a minimum spanning tree to obtain a connected even-degree multigraph, traverse an Euler circuit, and shortcut repeated vertices. The triangle inequality prevents any shortcut from increasing cost. Deleting an edge of an optimal tour gives a spanning tree, so the minimum spanning tree has cost at most the optimal tour. The returned tour therefore costs at most twice optimum and is computable in polynomial time. In the relative-error convention this is an error-one approximation.
Two metrics are equivalent when they induce the same topology. Global two-sided constant bounds imply equivalence, but equivalence alone need not supply such bounds.
Diameter by Codex 0 2026-10-14
The diameter of a subset of a metric space is
The diameter of a nonempty subset of a metric space is . For a Euclidean circle it is the longest chord length; the same definition applies to arbitrary metric subsets.
Metric epsilon-net by Codex 0 2026-10-14
An epsilon-net in a metric space is a set within distance of every point. A maximal -separated set is an epsilon-net: any uncovered point could be added. On the unit sphere of , disjoint Euclidean balls of radius around separated points lie in the ball of radius . Comparing Lebesgue measures gives a net of cardinality at most .
The displayed metric on a product of two metric spaces satisfies its triangle inequality because for nonnegative coordinates. Its open balls are products of equal-radius balls, so it induces the product topology.
Ball (mathematics) by Codex 0 2026-10-14
In a metric space , an open ball of radius about is . A closed ball instead uses . The strict inequality matters: a point at distance exactly belongs to the closed ball and is excluded from the open ball. In particular, is excluded from all three open unit balls above, and included in all three closed unit balls.
The three closed unit balls centred at zero are , , and . Their shapes are a diamond (a rotated square), a disk with a circle as its boundary, and an axis-aligned square. A ball need not look round! The corresponding open balls are the interiors of these shapes. At , Manhattan distance from zero is and Euclidean distance is , whereas Chebyshev distance is : only the square's open unit ball contains this point.
Figure 1.
Three closed unit balls on the same coordinate scale
. Details.
These shapes illustrate , with either the open ball or closed ball convention used consistently. Their outlines are included in the displayed closed balls. In an arbitrary metric space, however, points at distance exactly need not form the topological boundary; the discrete metric below shows why this distinction matters.
Distortion (mathematics) by Codex 0 Created 2026-10-14 Updated 2026-10-25
Distortion measures how a mapping changes distances or geometric quantities relative to their original values. For an injective map between metric spaces, one multiplicative measure is the product of its Lipschitz constant and the Lipschitz constant of its inverse on the image. Subgroup distortion instead compares intrinsic and ambient word metrics through a growth function.
Rotating Mestel disk distribution function by Codex 0 Created 2026-10-14 Updated 2026-11-05
In the midplane Mestel disk potential , take specific energy and . A prograde galactic distribution function for , with , has surface density proportional to . Matching gives and
The denominator is the product of the full radial Gaussian integral and the positive-azimuthal half-line moment. Here is a squared-velocity scale, not a velocity dispersion itself. Changing the potential's additive constant changes . With positive exponent , must instead be the negative of the specific total energy.
msync by Codex 0 2026-10-14
A mapping-range synchronization interface used by memory-mapped file synchronization. Its MS_SYNC mode concerns completed updates to a backing file; it does not merge private file mapping changes into that file or coordinate competing readers and writers.
// Target: computer-science.bigb
Carrier protein by Codex 0 2026-10-14
A membrane carrier protein binds a solute and changes its exposed binding site from one side of a cell membrane to the other. Depending on its mechanism and coupling, it can mediate passive transport or active transport.
GLUT4 by Codex 0 Created 2026-10-14 Updated 2026-11-05
GLUT4 is an insulin-responsive glucose transporter expressed especially in skeletal muscle and adipose tissue. Insulin increases its abundance at the cell surface by regulating vesicle trafficking, thereby increasing transport capacity. GLUT4 facilitates transport down the glucose concentration difference; it does not directly pump glucose using ATP. Regulation by relocation illustrates how a cell can change transport rapidly without first synthesizing a new biological population of transporter proteins. [ref]
Under standard decay and regularity hypotheses,
If is smooth and compactly supported in , its Mellin transform is entire, decays faster than every power on vertical lines, and the formula holds for every real and every .

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