A Hurwitz surface is a specific type of mathematical object in the field of algebraic geometry and topology. It is a smooth (or complex) surface that arises in the study of branched covers of Riemann surfaces. More specifically, Hurwitz surfaces are associated with the study of coverings of the Riemann sphere (the complex projective line) and are tied to the Hurwitz problem, which deals with the enumeration of branched covers of a surface.
A constructive dilemma is a valid logical argument form that involves a disjunction (an "either-or" statement) followed by conditional statements leading to a conclusion. It is used in propositional logic and typically follows a specific structure. The general form of a constructive dilemma can be expressed as follows: 1. \( P \lor Q \) (Either P or Q is true) 2. \( P \rightarrow R \) (If P is true, then R is true) 3.
Double negation is a logical principle stating that a proposition that is negated twice is equivalent to the proposition itself. In simpler terms, if you say "not not P," you are effectively affirming P. In formal logic, if "P" is a statement, then the double negation can be expressed as: ¬(¬P) ≡ P This principle is used in various fields, including mathematics, philosophy, and computer science.
The term "hexagon" can refer to a couple of different concepts depending on the context: 1. **Geometric Shape**: A hexagon is a polygon with six sides and six angles. In a regular hexagon, all sides are of equal length and all interior angles are equal, measuring 120 degrees each. The shape can be found in various natural and man-made structures, such as honeycomb patterns in beehives.
In logic, "exportation" is a valid rule of inference that deals with implications. It states that if you have a conditional statement of the form: 1.
In logic, a **tautology** is a statement or formula that is true in every possible interpretation, regardless of the truth values of its components. In other words, it is a logical expression that cannot be false. Tautologies are important in propositional logic and are often used as the basis for proving other statements. One common example of a tautology is the expression \( p \lor \neg p \) (where \( p \) is any proposition).
Refinement types are a type system feature that extends traditional type systems by allowing types to express more specific properties or constraints about values. They enable programmers to specify not just what type a value is, but also certain predicates that must hold true for values of that type. In a typical type system, a type like `Integer` simply describes integers without any additional constraints. Refinement types allow for the expression of constraints like "positive integers" or "even integers".
Jacques Herbrand was a French mathematician and logician, known for his significant contributions to mathematical logic, particularly in the areas of proof theory, model theory, and the foundations of mathematics. He was born on December 20, 1908, and died tragically young at the age of 27 in a car accident in 1931. Herbrand is especially recognized for Herbrand's theorem and Herbrand's universes, which are crucial in the context of first-order logic.
In music theory, a **pitch class** refers to a group of all pitches that are a whole number of octaves apart from each other. In other words, all the notes that have the same name, regardless of which octave they are in, belong to the same pitch class. For example, the pitch classes for C include all Cs, such as C4 (middle C), C5, C3, and so on. Each pitch class can be represented by a note name (e.
Endophora is a linguistic term that refers to a type of reference where a word or phrase relies on something mentioned within the same context, particularly within a text or discourse. It contrasts with exophora, which refers to references that draw on external contexts or knowledge outside of the discourse. In endophoric references, terms such as pronouns or definite descriptions refer back to previously mentioned entities or ideas within the same text. For example, in the sentence "The cat is on the roof.
X-FEN, or Extended Forsyth-Edwards Notation, is a notation system used to represent the state of a chess game, similar to the standard Forsyth-Edwards Notation (FEN).
Chinook is a computer program designed to play the game of checkers (draughts). It is particularly notable for being one of the first programs to reach a level of play that could effectively compete against human experts.
The Chess Engines Grand Tournament (CEGT) is an event that features various chess engines competing against each other in a structured format. These tournaments provide a platform for testing and comparing the strength of different chess engines, offering insights into their playing styles, strengths, and weaknesses. The competitions often involve engines running on high-performance hardware, and the results contribute to rankings and evaluations of the engines' abilities. Typically, the format involves several rounds of matches where engines play against each other in different time controls.
"Game Over: Kasparov and the Machine" is a documentary film that was released in 2003. It focuses on the famous chess match between world champion Garry Kasparov and IBM's chess-playing computer, Deep Blue, in 1997. The film explores the historical context of the match, the significance of artificial intelligence in the realm of chess, and the broader implications of humanity's relationship with technology.
A geo-fence is a virtual boundary that is set up around a specific geographical area. It uses GPS, RFID, Wi-Fi, or cellular data to define the perimeter of the area. When a device, such as a smartphone or a GPS-enabled asset, enters or exits this area, it triggers a predefined response or action, such as sending notifications, alerts, or enabling certain functionalities.
"Zero: The Biography of a Dangerous Idea" is a book written by Charles Seife, published in 2000. The book explores the history, philosophy, and implications of the concept of zero in mathematics and beyond. Seife discusses how the idea of zero has influenced various fields, including mathematics, science, and even theology, and he highlights the cultural and historical resistance to the acceptance of zero in different societies.
Pakistani poetics refers to the unique literary and artistic principles, themes, and styles found in poetry produced in Pakistan. It encompasses a rich tapestry of influences, given the country's diverse cultural, linguistic, and historical contexts. Here are some key elements of Pakistani poetics: 1. **Linguistic Diversity**: Pakistan is home to several languages, including Urdu, Punjabi, Sindhi, Pashto, Balochi, and English.
Poetic forms refer to the various structures and conventions that define the arrangement and composition of poetry. These forms often dictate aspects such as rhyme schemes, meter, line length, and overall organization. Different poetic forms can convey different emotions, themes, and styles. Here are some common types of poetic forms: 1. **Sonnet**: A 14-line poem typically written in iambic pentameter.
"Afflatus" is a noun that refers to a divine creative impulse or inspiration, often associated with artistic or poetic creation. The term originates from the Latin word "afflatus," which means "inspiration" or "breath." It suggests a sudden influx of creativity or ideas that can feel almost transcendent or otherworldly.
In the context of literature, "genius" refers to an exceptional intellectual or creative power or an individual endowed with such ability. This concept often encompasses extraordinary talent in writing, creativity, and insight that sets a literary figure apart from their peers. The term has been used to describe authors and poets who produce works that reflect profound understanding, innovation, and artistry.

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