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Questions that are about research in mathematics, or about the job of a research mathematician, without being mathematical problems or statements in the strictest sense. Do not use this tag for easy or supposedly easy mathematical questions.

263 votes

What are the most misleading alternate definitions in taught mathematics?

Many topics in linear algebra suffer from the issue in the question. For example: In linear algebra, one often sees the determinant of a matrix defined by some ungodly formula, often even with specia …
105 votes
Accepted

Have you solved problems in your sleep?

On several occasions it has happened that I have made a key insight while sleeping or drifting in and out of sleep. For example, one of the critical ideas in my paper Joel David Hamkins, Gap forcing, …
104 votes

Theorems with unexpected conclusions

My favorite example of this phenomenon is Goodstein's Theorem. Take any positive number $a_2$, such as the number $73$, and write it in complete base $2$, which means write it as a sum of powers of $2 …
98 votes
Accepted

Adapting arguments and plagiarism

What you describe seems to me to be a normal mode of mathematical progress, and I would urge you simply to carry on! Ride that train as far as you can. It often happens that someone's mathematical re …
94 votes

Mistakes in mathematics, false illusions about conjectures

Computer designers and programmers dreamed, from the earliest days of the computer, of a computer that could play chess and win. Even Alan Turing had that dream, and designed turochamp, the first ches …
86 votes

Has incorrect notation ever led to a mistaken proof?

Here is an example from set theory. Set theorists commonly study not only the theory $\newcommand\ZFC{\text{ZFC}}\ZFC$ and its models, but also various fragments of this theory, such as the theory o …
82 votes

Value of "of course" in the mathematical literature

I don't agree that if something is obvious, then it is obvious that it is obvious. When an author declares in a mathematical exposition that a fact is obvious, or says "of course" or something with a …
80 votes

Which mathematical ideas have done most to change history?

Turing's work on computability, extending those of Goedel and the other early logicians, paved the way for the development of modern computers. Before Turing and Goedel, the concept of computability w …
74 votes
Accepted

What's wrong with the surreals?

At a recent conference in Paris on Philosophy and Model Theory (at which I also spoke), Philip Ehrlich gave a fascinating talk on the surreal numbers and new developments, showcasing it as unifying ma …
Joel David Hamkins's user avatar
73 votes

Jokes in the sense of Littlewood: examples?

The fundamental axioms of mathematics are inconsistent if and only if we can prove that they are consistent. (Because, you know, it follows from "logic." See Second Incompleteness theorem)
68 votes
Accepted

Capitalization of theorem names

In English, proper nouns are capitalized. The numbered instances you mention are all usages as proper nouns, but merely refering to a lemma or corollary not by its name is not using a proper noun, and …
67 votes

How has "what every mathematician should know" changed?

As mathematics grows and diversifies beyond belief, surely the collection of topics that every mathematician must know is shrinking fast. One can carry out serious mathematical research in one area wh …
61 votes

Naming in math: from red herrings to very long names

Let me mention as a counterpoint that there is less need for new terminology than one might expect. Mathematical exposition is often more successful and clearer without new terminology, and one should …
60 votes
Accepted

How do you select an interesting and reasonable problem for a student?

Let me first answer a slightly different question, how to organize one's thoughts about such problems. I simply maintain a list of suitable projects, with ideas on how to approach them, and put them i …
48 votes

Awfully sophisticated proof for simple facts

There is no largest natural number. The reason is that by Cantor's theorem, the power set of a finite set is a strictly larger set, and one can prove inductively that the power set of a finite set is …

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