The Jacobi–Madden equation is a Diophantine equation
proposed by the physicist Lee W. Jacobi and the mathematician Daniel J. Madden in 2008. The variables a, b, c, and d can be any integers, positive, negative or 0. (In fact, any nontrivial solution must include both a positive and negative value.)
Jacobi and Madden showed that there are an infinitude of solutions of this equation with all variables non-zero.
The Jacobi–Madden equation represents a particular case of the equation
first proposed in 1772 by Leonhard Euler who conjectured that four is the minimum number (greater than one) of fourth powers of non-zero integers that can sum up to another fourth power. This conjecture, now known as Euler's sum of powers conjecture, was a natural generalization of the Fermat's Last Theorem, the latter having been proved for the fourth power by Pierre de Fermat himself.
However, until Jacobi and Madden's publication, it was not known whether there exist infinitely many solutions to Euler's equation with all variables non-zero. Only a finite number of such solutions was known. One of these solutions, discovered by Simcha Brudno in 1964, yielded a solution to the Jacobi–Madden equation:
Jacobi and Madden started with,
and the identity,
Adding to both sides of the equation,
it can be seen it is a special Pythagorean triple,
They then used Brudno's solution and a certain elliptic curve to construct an infinite series of solutions to both the Jacobi–Madden equation and Euler's equation. In contrast to Elkies' method, this involves non-zero values of the variables.
Jacobi and Madden also noticed that a different starting value, such as,
- Beal's conjecture
- Prouhet–Tarry–Escott problem
- Taxicab number
- Pythagorean quadruple
- Lander, Parkin, and Selfridge conjecture
- Sums of powers, a list of related conjectures and theorems
- Jacobi, Lee W.; Madden, Daniel J. (2008). "On ". American Mathematical Monthly 115 (3): 220–236.
- Mathematicians find new solutions to an ancient puzzle
- Noam Elkies (1988). "On A4 + B4 + C4 = D4". Mathematics of Computation 51 (184): 825–835. doi:10.2307/2008781. MR 0930224.
- Weisstein, Eric W., "Diophantine Equation–4th Powers", MathWorld.
- Jaroslaw Wroblewski Database of solutions to the Euler's equation
- Simcha Brudno (1964). "A further example of A4 + B4 + C4 + D4 = E4". Mathematical Proceedings of the Cambridge Philosophical Society 60 (04): 1027–1028. doi:10.1017/S0305004100038470. MR 0166151.
- Seiji Tomita Solutions of a^4 + b^4 + c^4 + d^4 = (a+b+c+d)^4