jsfisher
ETcorngods survivor
- Joined
- Dec 23, 2005
- Messages
- 24,532
- Each function Fi maps S to P(S). (The function has three indexes, the first is the number of the matrix, the second is the number of the column (or row, if the matrices are flipped and then rotated ccw by 90o) and the third is the number of the place in a given column (or row))
You actually mean two indices. I.e., iFj: S -> P(S), where i would be the "matrix index" and identifies a plane of the cube and j would be a column index within a plane. The column is then the codomain of the function.
As a matter of precision, too, the indices are not numbers, since that would restrict them to being countably. Each index is better thought of as an element of S. So, for example, for S = {a,b,c,...}, aFb(c) would be the third element in the second column of the first plane. (I'm using the ordinals in an imprecise, colloquial sense.)
Everything is unordered, too. If you want to impose an order, than your argument takes on serious damaged.
- The cardinality of the set of functions is the same as that of S. (yes)
- The functions are injective. (no, they are bijective in terms of infinite composition of functions)
The question was about each function individually. Given the other constraints, they each better be injective. We will revisit your bijective claim later.
- The functions are constructed such at {} is not in the codomain of any function. (the functions are constructed such that exactly some one member of P(S) is not in the codomain of any function)
Again, I was referring to the functions individually. I believe you are referring to the composite of all the functions. And by "some one member" you must mean "exactly one member".
Functions being what they are, without loss of generality we can assume that exactly one member is {}.
- For i <> j, the intersection of the codomains of Fi and Fj is empty (three indexes are needed (as explained in (1)) so this question is not well articulated)
Two indices, as explained earlier. And even at that, the second index is purely for convenience of identifying location in the cube. One index is sufficient to distinguish among the |S| functions.
- Every element of P(S) except {} appears n the codomain of Fi for some i. (Every element of P(S) (except exactly some one particular element of P(S)) appears in the codomain of F where each place in the codomain is indexed by three numbers, as explaines in question number 1)
Ok, so we have |S| functions whose codomains populate the columns in a cube. And there are |S| codomains of |S| members each, so there is a total of at most |S| x |S| = |S| members in the union of all those codomains.
How, exactly, are all the members of P(S) (except for exactly one member) all supposed to appear among the |S| members of the codomain union if |S| < |P(S)|?
|S| x |S| x |S| x ... x |S| = |S|, so go to any higher dimension cube you like. You'll still be short for covering all (except one) members of P(S).