>> >> >> >>> For those interested, James' result in the paper was shown to be >>> false in general by Arturo in October '02 and a specific >>> demonstration was given by Dale in September of '03, both in this >>> ng. >>> >> >> In my post in October (the only when where I've found the explicit >> statement of the observation) I already give the result by saying >> "here it is again". As for Dale's numerical calculation, in early >> August 2003 he was already repeating it, and Keith Ramsay rejoinded >> that he had "lost count" of how many times an explicit common >> factor had been given. >> > > Dale has remarked here that his first calculations along those lines > appeared on 21 June 2003. > > >> http://groups.google.com/groups?selm=20030811015606.10078.00001234%4- >> 0mb-m26.aol.com >> >> http://groups.google.com/groups?selm=3F37D13C.40008%40farir.com >> > > > Unless anyone objects, I'll send a polite heads-up to SWJPAM. They of > course will do with it what they want. > > > > > Regards, > > Rick > > >
I have done just that. Here is the text of my note:
> Dear Sirs, > > The December 2003 issue of your journal, Southwest Journal of Pure > and Applied Mathematics, publishes the article "Advanced Polynomial > Factorization" by James Harris. This note is to inform you that the > article's main result, the claim that the factorization of the > polynomial > > 65 x^3 - 12 x + 1 = (a_1 x + 1)(a_2 x + 1)(a_3 x + 1) > > one of the a's is coprime to 5, is in error. > > I'll expand on the proof of this error in my postscript. > > My sole intent in this note is one of information. I have no > expectations one way or the other regarding how you treat this > information, but you are certainly welcome to determine its > correctness. > > If you check the Usenet record (via Google, for instance), you'll > quickly get the picture that this has been a topic of no small amount > of heated discussion on sci.math over the past year, at least (and if > extended to ancillary topics, over the past several years. I would > not, for instance, recommend becoming entangled in this by now > fruitless discussion on sci.math > > Kindest regards, > > W. Dale Hall (wdh...@alum.mit.edu) > > PS. > > Several proofs of this error have appeared online in the Usenet > newsgroup sci.math. > > One such article was written by me in the following article: > > > http://groups.google.com/groups?selm=3F1C3F01.7010501%40farir.com&oe=- > UTF-8&output=gplain > > I will apologize in advance for whatever intemperate language appears > in various articles written by me and others in this and related > threads. > > The gist of the demonstration is the explicit factorization of the > a's in the following fashion: > > Let > > r(a) = 8 a^2 - 4 a - 45 > > Note first that r(a) is (1) an algebraic integer for any algebraic > integer "a", (2) a divisor of both "a" and 5 for a = -(any of the > ai's in the above factorization of 65x^3 - 12x + 1) > > The relevant factorizations claimed in (2) follow: > > q(a) = 8 a^2 - 76 a - 185 > r(a) = 8 a^2 - 4 a - 45 > s(a) = 4 a^2 - 37 a - 104 > > Whenever a is a root of x^3 - 12 x^2 + 65 (that is, a is the > *negative* of any of the ai's of the above factorization of > 65x^3 - 12x + 1), the following factorizations hold: > > q(a) r(a) = 5 (*) > r(a) s(a) = a. > > These factorizations can be established by elementary methods: for > instance, multiplying the above polynomials in the variable x, and > dividing the result by the polynomial p(x) = x3 - 12 x2 + 65 will > yield the remainders given on the right sides of the above equations > (*). > > First, here are the products that I'm making claims about: > > q(x)*r(x) = 64 x^4 - 640 x^3 - 1536 x^2 + 4160 x + 8325 > r(x)*s(x) = 32 x^4 - 312 x^3 - 864 x^2 + 2081 x + 4680 > > Next, a couple of products of p(x) = x^3 - 12 x^2 + 65 with > polynomials of degree 1: > > (64 x + 128)*(x^3 - 12 x^2 + 65) = > 64 x^4 - 640 x^3 - 1536 x^2 + 4160 x + 8320 > > (32 x + 72)*(x^3 - 12 x^2 + 65) = > 32 x^4 - 312 x^3 - 864 x^2 + 2080 x + 4680 > > Finally, we compare the results and see this: > > q(x)*r(x) = (64 x + 128)*p(x) + 5 > r(x)*s(x) = (32 x + 72)*p(x) + x, > > Note that, for any value xo that makes p(xo) = 0, that same value xo > will make q(xo)r(xo) = 5, so r(xo) is a factor of 5. > > That value of xo also makes r(xo)*s(xo) = xo, so r(xo) is a factor of > xo. > > In short, r(xo) becomes a factor of *both* xo and 5. > > Since r(x) is a polynomial with integral coefficients, r(xo) is an > algebraic integer whenever xo is. > > In fact, the minimal polynomial of this number (r(a) for -a = any of > the above ai's) is given as: > > MinPoly(r) = x^3 - 969 x^2 + 315 x + 5 > > The above facts prove that this "a" has a non-unit algebraic integer > as a factor, and thus cannot be a unit in the ring of algebraic > integers. > >