math -- elements of Z_p[x] which permute Z_p



The following is easily proved:

If p is prime, then for every function F: Z_p --> Z_p, there exists a
unique polynomial f in Z_p[x], with deg(f) < p, such that, regarding f
as a function from Z_p to Z_p, we have F = f.

In particular, every element of the permutation group S_p is uniquely
represented by a polynomial in Z_p[x] with degree < p.

The simplest examples are the linear polynomials, which form a
subgroup (under composition) of order p^2 - p.

With that as background, here's a conjecture ...

Conjecture:

If p is prime, p > 2, there does not exist f in Z_p[x], with deg(f) =
p - 1, which permutes Z_p.

Remarks:

While I've verified the conjecture for p = 3, 5, 7, 11, I don't have a
lot of confidence that it holds for all primes p > 2. I would estimate
my degree of belief as only about 60-40, based on what I know at this
point.

quasi
.



Relevant Pages

  • Re: math -- elements of Z_p[x] which permute Z_p
    ... every element of the permutation group S_p is uniquely ... The simplest examples are the linear polynomials, ... With that as background, here's a conjecture ... ... I'll leave it as a challenge problem for whoever wants to try it. ...
    (sci.math)
  • Re: math -- values of f(x) (mod p)
    ... quasi wrote: ... Conjecture: ... If n is a positive integer, then for all sufficiently large primes p, ...
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  • Re: math -- values of f(x) (mod p)
    ... quasi wrote: ... If n is a positive integer, then for all sufficiently large primes p, ... I'll repost the conjectire with a revised statement to avoid that. ... The revised conjecture includes the above constraint on deg. ...
    (sci.math)
  • Re: isprime of flattened primes...
    ... Let a_n be the concatenation of the first n primes. ... Conjecture 1: a_n is composite for all sufficiently large n. ...
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  • Re: isprime of flattened primes...
    ... Once you get "past" the single digit primes, ... Conjecture 1: a_n is composite for all sufficiently large n. ...
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