The in-plane tensile force per unit transverse length in a thin elastic sheet produces the linear transverse restoring force per unit area. A spatially uniform displacement has zero curvature and hence no elastic-sheet tension force. This explains why infinite elastic-sheet tension blocks fixed nonzero-wavenumber acoustic membrane waves but does not make the uniform mode rigid. The sheet's inertia, by contrast, acts also on uniform oscillations.
Two diametrically opposite rotating blades with equal tangential loads have zero total rotating force. Their leading compact acoustic dipoles cancel, but their retarded positions and moving-surface retarded Jacobians leave an acoustic quadrupole. For line load and angular speed , the first radiating density is . The twofold geometry gives frequency , while projection into the rotor plane gives the amplitude directivity .
For harmonic convention , choose by continuation from and impose vertical factors above the interface and below it. At positive real frequency, for propagating Fourier components and is positive real for evanescent components. This analytic prescription fixes the radiation branch and how the Fourier contour passes poles.
This is the total number of vertices in graph components with orders in the specified half-open interval. It differs from the number of those graph components. Write for the total above the lower endpoint. Then . Disjoint size bands count disjoint sets of vertices at a common time, even though their mass may move between bands as an Achlioptas process adds edges.
For the two-choice Achlioptas process, fix and . Conditional on any current graph with , put equal to the vertices in its large graph components. There are at most such initial graph components. If after more steps no graph component contains vertices of , greedily assign final graph components to two groups so that each meets at least vertices of . This induces a set partition of the initial large graph components, of which there are at most possibilities.
For any fixed such split , a uniform candidate edge joins to with probability at least . If both candidates do so, the selected edge cannot avoid the crossing. Thus the probability that the split survives all steps is at most . The deliberately weaker constant also covers distinct candidate sampling for sufficiently large . In the absent-edge version, as long as the split has survived, every -- edge is absent, so conditioning on absence can only increase this crossing probability. A union bound with and bounds failure by . For fixed , a further union bound makes the conclusion simultaneous over all starting steps . This proof is independent of how the rule chooses between the two candidates.
Fix positive , and . Suppose a size band of an Achlioptas process contains at least vertices at time . For every fixed , at least of those vertices remain in unchanged graph components throughout the next steps, with high probability, where one may take . This is a deliberately nonoptimal positive constant.
For independent uniform candidate edges, an initial graph component with vertices is untouched if none of the candidate edges meets it. A uniform edge hits it with probability at most . For sufficiently large , , so the expected value of the untouched vertex mass is at least . Replacing one row of two candidate edges can change by at most , because only the initial graph components hit by an old or new endpoint can change status. The McDiarmid inequality therefore makes except on an event of probability , for a positive constant depending only on . An untouched graph component stays unchanged whichever offered edge is selected.
For candidates restricted to absent edges, generate each by an independent uniform proposal stream and reject already present edges. During any interval of steps with present edges, each proposal has rejection probability conditional on the past. The number of rejections is at most except on an event of probability smaller than any inverse power of : if there were rejections among proposals, a union bound over their positions bounds this by . The first proposals are independent and give the previous untouched-mass estimate. Extra proposals can touch at most additional initial graph components, losing only vertices for fixed . This leaves the stated bound. A union bound makes these estimates simultaneous over starting times . They hold through the entire interval, so deterministic or random stopping times within it are allowed.
A fixed-choice Achlioptas process cannot have its largest component of a graph jump from to a fixed positive fraction of within steps, with high probability. The proof combines forced merging of large components and persistence of unsampled graph components. An assumed jump forces positive vertex mass in each band slightly before the jump: insufficient smaller components can feed the final large component, while enough components above would merge too early. Persistence carries a fixed positive amount of each band to a common time. Taking sufficiently many disjoint bands with then counts more than vertices. The number of offered candidates is fixed throughout this argument. Riordan and Warnke establish this obstruction and broader continuity results in their original research paper.
Weibull distributions with a common shape form both an accelerated life family and a proportional hazards family. Their hazard functions are , whose ratio is . Their time multiplier is . In the representation with and density for , the parameters are and , giving time multiplier and hazard multiplier .
For , with unit exponential distribution and , the survivor functions are for . These are time-scaled Fréchet distributions, so they form an accelerated life family. However their hazard ratio is , tending to zero as and to one as . It is not constant. Thus a positive-scale assumption matters when deriving a proportional hazards family from the usual log-location-scale model.
For any finite set of couplings in , the simultaneous Dirichlet approximation theorem supplies arbitrarily late near-alignment of all phases, or an exact common period. Thus finite bath coherence does not tend to zero as time tends to infinity. This remains true for almost every realization of continuous random couplings; an ensemble mean can decay while each realization has recurrences.
Independent random couplings suppress typical coherence as the bath size increases. This conclusion concerns an ensemble or a specified large-bath limit, and must be distinguished from a pointwise long-time limit for one finite realization. Ensemble spin-bath coherence supplies exact mean and mean-square formulas for a uniform coupling distribution, while short-time Gaussian spin-bath decoherence gives the initial decay scale.
Cost-weighted finite search game by Codex 0 Created 2026-10-07 Updated 2026-11-05
Consider a zero-sum game in which a hider selects one of locations and a searcher inspects locations until finding it. Inspection costs are , paid also at the discovered location; the hider maximizes total cost and the searcher minimizes it. Put . The value of a zero-sum game is
The hider uses probabilities . Every complete search order then has the same expected payoff: summing each cost multiplied by the probability that its location or a later one hides the object gives .
For the searcher's matching guarantee, inspect location first with probability , then inspect the remaining locations in a uniformly random order. For distinct , the probability that precedes is
If the object is at , expected total cost is therefore . Both guarantees hold for every opponent choice, proving optimality for any finite number of locations, including the three-location case.
Induced worldvolume metric by Codex 0 Created 2026-10-07 Updated 2026-11-05
The induced worldvolume metric is the pullback of the target metric tensor by a brane embedding. For a nondegenerate timelike embedding, is its invariant worldvolume volume density. The specialization is the induced worldsheet metric.
Auxiliary worldvolume metric by Codex 0 Created 2026-10-07 Updated 2026-11-05
An auxiliary worldvolume metric is an independent metric introduced in a brane action, distinct from the induced worldvolume metric. Its algebraic equation can eliminate it. For the Polyakov action of a string, it is determined only up to a Weyl transformation.
Discriminant mass invariant of a cubic superpotential by Codex 0 Created 2026-10-07 Updated 2026-11-05
Under a superpotential critical-point shift, and the linear coefficient vanishes, while is unchanged. At either supersymmetric root , the complex fermion mass parameter is . The physical scalar and fermion masses are both , independent of the additive superpotential constant. A repeated critical point has a massless multiplet and a quartic leading scalar potential.
Opposing-wind ventilation bistability by Codex 0 Created 2026-10-07 Updated 2026-11-05
For , the well-mixed ventilation temperature balance has one stable upward-flow temperature and two downward-flow temperatures. The heat-removal curve on the latter interval is , maximal at . Its lower-temperature root is stable and its higher-temperature root unstable. The two meet at a saddle-node bifurcation. The unstable root separates the basins of the stable wind-dominated and buoyancy-dominated states.
Divisorial ideal by Codex 0 2026-10-07
For a normal variety with affine coordinate ring and a Weil divisor , the fractional ideal of functions whose principal Weil divisor is at least is
For an effective prime divisor this is its height-one prime ideal. If the divisor is Cartier locally, this ideal is locally principal. A nonprincipal height-one prime ideal in a normal local ring can therefore detect a non-Cartier divisor.
Linear equivalence of Weil divisors by Codex 0 Created 2026-10-07 Updated 2026-10-14
Two Weil divisors are linearly equivalent when their difference is a principal Weil divisor. This is the equivalence relation defining the divisor class group, and applies to normal varieties of any dimension, not just curves.
Support of a Weil divisor by Codex 0 Created 2026-10-07 Updated 2026-10-14
For , its support is the union of the prime divisors with . Negative as well as positive coefficients contribute. A point outside the support has a neighbourhood on which the divisor is zero.
For Fréchet spaces, the two continuity conditions for a linear map are equivalent. Original continuity makes every target continuous linear functional compose to a source continuous linear functional, proving weak continuity. Conversely, weak continuity makes these compositions continuous in the original source topology. They separate target points, so limits in the graph of a linear operator remain in the graph. The closed graph theorem for Fréchet spaces finishes the proof.
Without the hypotheses, equal continuous dual spaces do not imply equal topologies. The identity from an infinite-dimensional Hilbert space with its weak topology to its norm topology is weak-to-weak continuous but not continuous in those original topologies.

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