Fejér's theorem is a result in the theory of Fourier series, specifically concerning the convergence of the Fourier series of a periodic function. It states that if \( f \) is a piecewise continuous function on the interval \([-L, L]\), then the sequence of partial sums of its Fourier series converges uniformly to the average of the left-hand and right-hand limits of \( f \) at each point.
Wirtinger's representation theorem and projection theorem are fundamental results in mathematical analysis, particularly in the fields of functional analysis and the theory of Sobolev spaces. They are often applied in the study of harmonic functions, the solution of partial differential equations, and variational problems. ### Wirtinger's Representation Theorem: The Wirtinger representation theorem provides a way to connect the Dirichlet energy of functions to their boundary conditions.
The Friedlander–Iwaniec theorem is a result in number theory, specifically in the area of additive number theory concerning the distribution of prime numbers. It was established by the mathematicians J. Friedlander and H. Iwaniec in the early 1990s.
The Fundamental Theorem on Homomorphisms, often referred to in the context of group theory or algebra in general, states that there is a specific relationship between a group, a normal subgroup, and the quotient group formed by the subgroup. In summary, it describes how to relate the structure of a group to its quotient by a normal subgroup.
The Quillen–Suslin theorem, also known as the vanishing of the topological K-theory of the field of rational numbers, is a fundamental result in algebraic topology and the theory of vector bundles. It states that every vector bundle over a contractible space is trivial. More specifically, it can be expressed in the context of finite-dimensional vector bundles over real or complex spaces.
The Barban–Davenport–Halberstam theorem is a result in number theory, specifically in the area of additive number theory and the distribution of prime numbers. It provides a way to estimate the size of the prime numbers in certain ranges. More formally, the theorem deals with the distribution of prime numbers in arithmetic progressions and gives a bound on the number of primes in intervals of certain lengths.
Maier's theorem is a result in number theory related to the distribution of prime numbers. Specifically, it deals with the existence of certain arithmetic progressions among prime numbers. The theorem is typically discussed in the context of additive number theory and is named after the mathematician Helmut Maier, who contributed to the understanding of the distribution of primes.
Alspach's conjecture, proposed by Alspach in 1970, is a conjecture in the field of graph theory. It pertains to the existence of certain types of graphs known as 1-factorizations of complete graphs.
The Cook–Levin theorem, established by Stephen Cook in 1971 and independently by Leonid Levin, is a fundamental result in computational complexity theory. It states that the Boolean satisfiability problem (SAT) is NP-complete. This means that SAT is at least as hard as any problem in the complexity class NP (nondeterministic polynomial time), and any problem in NP can be reduced to SAT in polynomial time.
Height typically refers to the measurement of an object or individual from base to top, or the distance from the ground to the highest point. In a biological context, height often pertains to humans or animals and is measured from the feet to the top of the head when standing upright. Height can be expressed in various units, such as centimeters, meters, feet, or inches. In other contexts, such as geography, height might refer to the elevation of a location above sea level or another reference point.
Rita Zemach is a prominent figure in the field of linguistics, known particularly for her work on syntax and semantics. She has contributed to the understanding of various linguistic phenomena and theories.
A circular mil is a unit of area used primarily in the electrical industry to describe the cross-sectional area of a conductor, such as a wire. It is defined as the area of a circle with a diameter of one mil (one thousandth of an inch). To calculate the area in circular mils, the formula is: \[ \text{Area (circular mils)} = \frac{D^2}{0.
The term "water resistant" refers to a product's ability to resist the penetration of water to some degree, but it does not imply that the product is completely waterproof. The water resistance mark is typically used in relation to watches, electronics, clothing, and other items that may be exposed to moisture.
The term "cosmological decade" isn't an established scientific term, but it can refer to a period in cosmological research characterized by significant advancements or discoveries in our understanding of the universe. For instance, one might describe the period from the 2000s to the early 2010s as a cosmological decade due to breakthroughs in dark energy studies, the detection of exoplanets, and the further development of the Lambda Cold Dark Matter (ΛCDM) model of cosmology.
The unit of magnetic flux is the weber (Wb) in the International System of Units (SI). One weber is defined as the amount of magnetic flux that, when linking a circuit of one turn, produces an electromotive force of one volt when the flux is reduced to zero at a uniform rate in one second.
The unit of magnetic induction, also known as the magnetic flux density, is the tesla (symbol: T) in the International System of Units (SI). One tesla is defined as one weber per square meter (1 T = 1 Wb/m²). Another commonly used unit, especially in electromagnetic contexts, is the gauss (G), where 1 tesla is equal to 10,000 gauss (1 T = 10,000 G).
"Groatland" is not a widely recognized term or name in common usage. It may refer to a specific location, fictional setting, or concept depending on the context. For instance, it could be a name for a business, community, or creative work. Without further context, it’s difficult to provide a precise description.
The Baumé scale is a density-based scale used to measure the specific gravity of liquids, particularly in industrial and chemical applications. There are two versions of the Baumé scale, one for fluids lighter than water (typically used for liquids like alcohol) and one for fluids heavier than water (typically used for liquids such as acids and syrup). 1. **For liquids lighter than water:** A higher Baumé reading indicates a lower specific gravity.
A horsepower-hour (hph) is a unit of energy that represents the amount of work done by a horse using one horsepower over one hour. Horsepower is a unit of power that typically denotes the rate at which work is done. Specifically, one horsepower is commonly defined as equivalent to 550 foot-pounds of work done per second, or approximately 746 watts.
The miner's inch is a unit of measurement used primarily in the context of water flow and irrigation, particularly in the Western United States. It represents the flow of water through an opening or a pipeline, specifically how much water flows from a mine or irrigation ditch given a certain cross-sectional area. The term is derived from historical mining practices where water was crucial for certain mining operations.

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 2.
    You can publish local OurBigBook lightweight markup files to either https://OurBigBook.com or as a static website
    .
    Figure 3.
    Visual Studio Code extension installation
    .
    Figure 4.
    Visual Studio Code extension tree navigation
    .
    Figure 5.
    Web editor
    . 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.
    Video 4.
    OurBigBook Visual Studio Code extension editing and navigation demo
    . Source.
  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