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= The Erdos-Woods Problem =
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= The Erdös-Woods Problem=
  
This page introduces a problem considered by Erdos and Woods.  
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The Erdös-Woods problem is a surprisingly far reaching question about integers. I has implications for mathematical logic, [[ABC triples]], [[elliptic curves]], and can be generalized to (affine) [[schemes]]. This generalization provides links between number theory and Nevanlinna's value distribution theory in complex analysis. Connections between Nevanlinna theory and number theory have already been emphasized by Lang and Vojta in connections with Roth's theorem.  
  
'''Defintion (Radical)''': The radical of a positive integer n is simply the product of all those prime numbers p which divide n.
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This completely independent connection suggests that the ABC conjecture could stated for the ring of entire functions. I seems plausible that it could even be proven by one of our friendly neighborhood Nevanlinna theorists.  
  
'''Remark''': There are no prime numbers which divide 1, so rad(1) is the product of all the elements in the empty set. The only reasonable value to choose for this number is 1.
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'''UPDATE:''' Apparently ABC conjecture has already been proven for the field of meromorphic functions. This was the topic of a recent Séminaire Bourbaki, documented [http://arxiv.org/pdf/0811.3153v1 here].
  
To compute rad(n) in sage, define the following simple function.
 
  
sage: def rad(n):<br>....: return prod(n.prime_divisors())<br>....: <br>sage: rad(256)<br>2<br>sage: rad(210)<br>210<br><br>
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= Algorithm =
  
The rad(n) is a function with some very nice properties. It also behaves well with respect to the function gcd(A,B).
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One way to think about the Erdös-Woods problem for integers is as follows. You are confronted by an Evil Wizard who tells you that he is thinking of an integer $n$. He will tell you the primes dividing $n$, $n+1$, and $n+2$ respectively. You are asked to determine $n$. Given $V(n)$ and $V(n+1)$ we can prove, by invoking a theorem of Shafarevich, that there are only finitely many possible values of $n$.  
  
'''Exercise 1:''' Suppose that A and B are positive integers. Show that:
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A reasonable computational task is to compute this finite set. This involves computing the set of all elliptic curves with full two-torsion with good reduction outside a finite set of primes. Noam Elkies has suggested that the best way to do this might be to compute the set of all possible [[Lambda Invariants]] by solving an [[S-Unit Equation]]. These equations can be solved using Baker's method of [[Linear Forms in Logarithms]].
 
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gcd(rad(A),rad(B)) = rad(gcd(A,B))
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and
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rad(AB) = rad(A)rad(B)/rad(gcd(A,B))
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== The Evil Wizard  ==
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Suppose you are confronted by an evil wizard who presents you with the following challenge:
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"'''I'm going to pick a positive integer $n &gt; 1$ and then I shall tell you the radical of each integer from $n$ to $n+k$. Then you must tell me what $n$ is.'''"
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For which $k$ should you accept this challenge? Discuss...
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Latest revision as of 16:48, 5 August 2010

The Erdös-Woods Problem

The Erdös-Woods problem is a surprisingly far reaching question about integers. I has implications for mathematical logic, ABC triples, elliptic curves, and can be generalized to (affine) schemes. This generalization provides links between number theory and Nevanlinna's value distribution theory in complex analysis. Connections between Nevanlinna theory and number theory have already been emphasized by Lang and Vojta in connections with Roth's theorem.

This completely independent connection suggests that the ABC conjecture could stated for the ring of entire functions. I seems plausible that it could even be proven by one of our friendly neighborhood Nevanlinna theorists.

UPDATE: Apparently ABC conjecture has already been proven for the field of meromorphic functions. This was the topic of a recent Séminaire Bourbaki, documented here.


Algorithm

One way to think about the Erdös-Woods problem for integers is as follows. You are confronted by an Evil Wizard who tells you that he is thinking of an integer $n$. He will tell you the primes dividing $n$, $n+1$, and $n+2$ respectively. You are asked to determine $n$. Given $V(n)$ and $V(n+1)$ we can prove, by invoking a theorem of Shafarevich, that there are only finitely many possible values of $n$.

A reasonable computational task is to compute this finite set. This involves computing the set of all elliptic curves with full two-torsion with good reduction outside a finite set of primes. Noam Elkies has suggested that the best way to do this might be to compute the set of all possible Lambda Invariants by solving an S-Unit Equation. These equations can be solved using Baker's method of Linear Forms in Logarithms.

Alumni Liaison

has a message for current ECE438 students.

Sean Hu, ECE PhD 2009