What are really helpful math resources out there on the web?
Please don't only post a link but a short description of what it does and why it is helpful.
Please only one resource per answer and let the votes decide which are the best!
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Sign up to join this communityWhat are really helpful math resources out there on the web?
Please don't only post a link but a short description of what it does and why it is helpful.
Please only one resource per answer and let the votes decide which are the best!
edit by jc: As of May 11, 2010, the work has been completed!
This is a reference that is not yet complete, but it should be very useful when it finally does arrive:
Digital Library of Mathematical Functions (DLMF)
(book and associated website;
will replace Abramowitz & Stegun's Handbook of Mathematical Functions)
NIST / Cambridge University Press
expected 2009/2010
http://dlmf.nist.gov/
This will contain diagrams, tables, properties of, principal values of, and relationships between many important mathematical functions. For example, the trigonometric and other elementary functions are described, with very many formulae relating them.
The Handbook is very good; the Digital Library will be even better.
http://maths-magic.ac.uk/index.php
Apparently UK has been building a depository/interactive system for graduate math courses. Click on "courses" to access archives. Many have lecture notes and other materials.
I found this recently. Have not actually personally used it, but potentially very useful.
From website: Project Euler is a series of challenging mathematical/computer programming problems that will require more than just mathematical insights to solve. Although mathematics will help you arrive at elegant and efficient methods, the use of a computer and programming skills will be required to solve most problems.
From me: I have personally found it beneficial to go through these to help work at how I think about math problems.
Sci-Hub is pretty helpful in accessing articles, even for those researchers who already have access to several journals. The interface is great, the site is pretty fast, and the database is huge. See this article and other linked articles there for a nice overview of who all are downloading pirated papers.
Edit: as pointed out in the comments, it should be noted that there is an ongoing lawsuit against the website.
While not as comprehensive as wikipedia, if you find an article on the scholarpedia on a topic, it should be the first place to look:
I recommend archive.org. Books from Fourier, Lagrange, Euler... old stuff.
Hosts high-level maths discussions, forums have inline LaTeX rendering.
Alexandre Stefanov keeps an extensive list of free math books / lecture notes. The list is divided according to subject and updated frequently. I have found some very nice books there.
It seems this link hasn't appeared above http://www.ams.org/mathweb/index.html The resources there are too rich to describe.
Resource for books is book.fi - select English from upper right.
Resource for (mostly free) papers is projecteuclid.org
http://citeseer.ist.psu.edu/ caches a lot of papers that has been posted online. It often comes up within the first few search results in Google. (But you cannot view the cached documents online, since they are directly downloaded.)
All math.[institution].edu/~[professor]/ sites are great with, in of themselves, many links to the favorites of the page's professor.
It is like walking up to the professor at coffee and asking him about the tools he uses (resources) and how it applies to his research . A big cafeteria with the world's professors ressembled and willing to answer any questions... or at least those who keep their site up to date.
An example: http://www.math.ucla.edu/~tao/
Professor Tao's page is mostly blue (links).
The manifold atlas is pretty cool. I haven't spent enough time on it though... It seems like a different type of mathematical venture. Hopefully, it will inspire other similar projects. http://www.map.mpim-bonn.mpg.de/index.php/Main_Page
Overleaf.com is an excellent online LaTeX platform that allows you to collaborate with others, track changes, etc.
It also has many helpful pages on how to use Latex.
The optimization community seems to prefer this specific online repository instead of the more broad one arxiv.
Since someone mentioned The Digital Library of Mathematical Functions, we better also include The Wolfram function site: http://functions.wolfram.com/
It's really useful for special function identities - especially since they are also available in Mathematica input form that you can copy straight into your code.
Quite impressive is this site:
"PlanetMath is a virtual community which aims to help make mathematical knowledge more accessible" - or how they put it: "Math for the people, by the people":
LMFDB has been officially launched yesterday (10th May of 2016).
It is an integrated knowledge database of L-functions and modular forms with a nice web interface that helps visualize the connections between these mathematical objects.
Topology Atlas at York University is a great site with an awesome Q&A board (it of course, was not just restricted to Topology) and has been around for years.
I use
https://groupprops.subwiki.org/wiki/Main_Page
e.g. for looking up less well-known definitions in group theory.
I don't know if this reference is of sufficient generality:
Finite Calculus: A Tutorial for Solving Nasty Sums
by David Gleich
https://www.cs.purdue.edu/homes/dgleich/publications/Gleich%202005%20-%20finite%20calculus.pdf
(The original link at http://www.stanford.edu/ no longer exists.)
It is only a paper, but it describes the methods of the so-called "umbral calculus": a really useful technique to know.
There are some great things here at the small but fine Clay Institute Online Library
People: consider http://www.digizeitschriften.de/ tons of classical papers in english...
I think it is worth to check the 39 journals collection on world class referee-ed mathwork.
One paper on Mathematische Annalen (which is the very amusing): "On the holymorphic flow with an isolated singularity", is the famous GSV, gives you an index formula...
Two sites created by my former wonderful A level Mathematics teacher: www.whitegroupmaths.com www.a-levelmaths.com
He has generously written tons of topic summaries, worked revision problem sets and other learning material made mostly free to us students. Felt he deserves a mention for all his efforts :) Thanx n hope u will benefit from them!
Estella
Jahrbuch Database
A sort of Mathscinet and Zentralblatt for the period 1868-1942. Most of the reviews are in German. It is interesting to read the reviews written by mathematicians like Frobenius, Hilbert, Minkowski, Hasse, E. Noether, Artin, Mittag-Leffler, Landau, Van der Waerden, ...