What is the best notation for this set? - MathOverflow most recent 30 from http://mathoverflow.net 2013-06-20T02:11:01Z http://mathoverflow.net/feeds/question/13536 http://www.creativecommons.org/licenses/by-nc/2.5/rdf http://mathoverflow.net/questions/13536/what-is-the-best-notation-for-this-set What is the best notation for this set? Frank 2010-01-31T04:02:36Z 2010-01-31T11:07:28Z <p>I have variables that are indexed by $x$ and $y$: $V_{xy}$. What is the best notation for "all $V_{x1}$ variables, for $x=1,\dots,X$"? </p> <p>I'd like to write something like "I set all variables $\{V_{x1}, x=1,\dots,X\}$ to zero."</p> http://mathoverflow.net/questions/13536/what-is-the-best-notation-for-this-set/13552#13552 Answer by Francesco Turco for What is the best notation for this set? Francesco Turco 2010-01-31T09:26:55Z 2010-01-31T09:26:55Z <p>Morse-Kelley class theory would allow such a class: $\{z:\exists(x,y)(z=V_{xy};x\in\{1,\ldots,X\};y=1)\}$; in Zermelo-Fraenkel set theory you should also specify from which set $Z$ you choose $z$: this of course depends on what you mean by $V_{xy}$.</p> http://mathoverflow.net/questions/13536/what-is-the-best-notation-for-this-set/13554#13554 Answer by Jon Yard for What is the best notation for this set? Jon Yard 2010-01-31T11:07:28Z 2010-01-31T11:07:28Z <p>Set the variables $V_{11}, V_{21}, \ldots, V_{X1}$ equal to zero.</p>