Algebraic structure by Ciro Santilli 40 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
María del Pilar Díaz could refer to various individuals or contexts, as it is a relatively common name in Spanish-speaking countries. Without additional context, it's difficult to provide a specific answer. The name could refer to a public figure, academic, artist, or someone else in a specific field.
Order (algebra) by Ciro Santilli 40 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.
Linear function by Ciro Santilli 40 Updated 2025-07-16
The term is not very clear, as it could either mean:
Linear map by Ciro Santilli 40 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.
Hybrid mail is a service that combines traditional postal mail and digital communication technologies. It allows users to prepare and send mail through digital means that are then printed, processed, and delivered by a postal service. Here's how it typically works: 1. **Digital Document Creation**: Users create a document, letter, or mail item using digital tools, such as word processors or specific hybrid mail software.
IMail is an email server software developed by IMail Communications (now a part of the team at Cypoint). It provides email hosting capabilities and features for businesses and organizations. IMail offers functionalities such as: 1. **Email Hosting**: It can host email for domains and provide services like sending, receiving, and managing emails.
The London Action Plan is a strategic framework aimed at addressing issues related to international crime, particularly in the context of online fraud and scams. While there are different initiatives and frameworks with similar names, the term is most commonly associated with efforts to enhance cooperation among law enforcement agencies, industry stakeholders, and governments to combat the growing threat of cybercrime through coordinated action.
A suppression list is a compilation of contacts or identifiers that should be excluded from certain communications or marketing efforts. These lists are typically used in email marketing, advertising, and other forms of outreach to prevent messages from being sent to recipients who have opted out, unsubscribed, or should not be included for various reasons.
RelayOne is a platform designed to enhance communication and workflow efficiency, particularly in business settings. It focuses on integrating various communication channels, such as messaging, emails, and calls, into a single interface. By doing so, RelayOne aims to streamline operations and improve collaboration among teams. The platform often includes features like task management, real-time collaboration tools, and analytics to help organizations monitor performance and communication effectiveness.
SpamBayes is an open-source statistical email classifier that is designed to filter out unwanted email, commonly known as spam. Developed using the Python programming language, SpamBayes employs a Bayesian filtering algorithm to analyze the content of incoming emails and determine the likelihood that a message is spam based on statistical probabilities derived from previously classified emails.

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