Algebraic structure by Ciro Santilli 37 Updated 2025-07-16
A set plus any number of functions , such that each satisfies some properties of choice.
Key examples:
  • group: one function
  • field: two functions
  • ring: also two functions, but with less restrictive properties
Order (algebra) by Ciro Santilli 37 Updated 2025-07-16
The order of a algebraic structure is just its cardinality.
Sometimes, especially in the case of structures with an infinite number of elements, it is often more convenient to talk in terms of some parameter that characterizes the structure, and that parameter is usually called the degree.
Degree (algebra) by Ciro Santilli 37 Updated 2025-07-16
The degree of some algebraic structure is some parameter that describes the structure. There is no universal definition valid for all structures, it is a per structure type thing.
This is particularly useful when talking about structures with an infinite number of elements, but it is sometimes also used for finite structures.
Examples:
Linear map by Ciro Santilli 37 Updated 2025-07-16
A linear map is a function where and are two vector spaces over underlying fields such that:
A common case is , and .
One thing that makes such functions particularly simple is that they can be fully specified by specifyin how they act on all possible combinations of input basis vectors: they are therefore specified by only a finite number of elements of .
Every linear map in finite dimension can be represented by a matrix, the points of the domain being represented as vectors.
As such, when we say "linear map", we can think of a generalization of matrix multiplication that makes sense in infinite dimensional spaces like Hilbert spaces, since calling such infinite dimensional maps "matrices" is stretching it a bit, since we would need to specify infinitely many rows and columns.
The prototypical building block of infinite dimensional linear map is the derivative. In that case, the vectors being operated upon are functions, which cannot therefore be specified by a finite number of parameters, e.g.
For example, the left side of the time-independent Schrödinger equation is a linear map. And the time-independent Schrödinger equation can be seen as a eigenvalue problem.
For the typical case of a linear form over , the form can be seen just as a row vector with n elements, the full form being specified by the value of each of the basis vectors.
Packet Clearing House (PCH) is a non-profit organization that focuses on improving the performance and reliability of the Internet through the development and deployment of various network infrastructure solutions. PCH is known for providing services such as Internet exchange points, route servers, and DNS infrastructure to enhance connectivity among networks and facilitate the efficient exchange of Internet traffic. PCH plays a key role in increasing the resilience of global Internet infrastructure, particularly in regions that may be underserved or have less-developed telecommunications networks.
The term "public opinion brigades" is not a widely recognized or standard concept, so its meaning can vary based on context. However, it seems to refer to organized groups or initiatives aimed at influencing public opinion or collecting and analyzing public sentiment on various issues. Such organizations may work in the fields of politics, marketing, social movements, or research.
ZA Central Registry (ZACR) is the organization responsible for managing the registration of domain names under the .za (South Africa) country code top-level domain (ccTLD). Founded in 1995, ZACR oversees the infrastructure and policies related to domain registrations in South Africa, ensuring the stability and security of these domains. ZACR offers various services related to domain name registration, including support for second-level domains like .co.za, .net.za, .org.
French Internet celebrities, often referred to as "influenceurs" or "influenceuses" in French, are individuals who have gained significant popularity and a large following on various online platforms, such as YouTube, Instagram, TikTok, and Twitter. These personalities can span across different niches, including fashion, beauty, gaming, travel, food, and lifestyle.
The Service for French Internet Exchange (SFINX) refers to a network exchange point in France designed to facilitate the exchange of internet traffic between different networks, also known as Internet Service Providers (ISPs) and other organizations. SFINX is operated by the French National Institute for Research in Computer Science and Automation (Inria) and is located in Paris.
The World Internet Conference (WIC) is an annual event held in China that focuses on discussing the development and governance of the internet. The conference was first convened in 2014 and is organized by the Cyberspace Administration of China. It brings together leaders from government, business, academia, and civil society to share insights, exchange ideas, and address global internet-related issues.
The Conseil national du numérique (CNNum) is a French advisory body dedicated to digital issues and transformation. Established in 2011, it aims to provide recommendations and insights to the French government and other stakeholders on various aspects of the digital economy, technology, and digital policy. The CNNum's mission includes analyzing the impact of digital technology on society, the economy, and public policy, as well as promoting the development of digital skills, enhancing innovation, and fostering inclusivity in the digital realm.
France is home to a variety of internet technology companies that operate in different sectors, including software development, e-commerce, digital services, and more. Here are some notable internet technology companies based in France: 1. **Orange S.A.** - One of the largest telecommunications operators in the world, providing a range of internet and mobile services. 2. **Atos** - A multinational IT services company that offers consulting, digital services, and technology solutions to various industries.
Internet censorship in the United Kingdom refers to the regulation and restriction of online content and activities by the government, internet service providers (ISPs), or other entities. While the UK generally upholds free speech and access to information, various measures are in place that can restrict certain types of content.
As of my last knowledge update in October 2023, I cannot provide real-time data or the latest rankings for YouTube videos, including the most-viewed French music videos. However, some French music videos that have historically received a high number of views and could be included in such a list are: 1. **"Despacito" (Remix) - Luis Fonsi ft.

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