Timeline for Examples of common false beliefs in mathematics
Current License: CC BY-SA 2.5
4 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Jan 5, 2018 at 21:07 | comment | added | LSpice | @roysmith, I remember how puzzled I was when first learning about algebraic groups to be forced to think of $\mathrm{GL}_n$ as a closed subvariety of an affine space, when it so manifestly wants to be open …. | |
| Apr 14, 2011 at 18:45 | comment | added | roy smith | this is another of the standard algebraic geometry examples from the "red book", whereby one shows the affine open set f(x) ≠ 0 is isomorphic to the closed set yf(x) = 1, in one dimension higher ambient space. | |
| May 5, 2010 at 12:44 | comment | added | David E Speyer | The standard counter-example is $\mathbb{R} \times \mathbb{R} \to \mathbb{R}$, with the closed hyperbola $xy = 1$ mapping to the open set $x \neq 0$. I remember making this mistake, but not what problem prompted me to do so. | |
| May 4, 2010 at 23:29 | history | answered | Matt | CC BY-SA 2.5 |