Let $A$ be the matrix:
$$A = \text{If } n \bmod k=0 \text{ then } 1\text{ else }0$$
Let $B$ be the matrix:
$$B=\text{If }k \bmod n=0\text{ then }\Im(\rho _n)\text{ else }0$$
where $\Im(\rho _n)$ is the imaginary part of the $n$-th Riemann zeta zero.
Consider the equation:
$$|A.B-A x|=0$$
which is almost as the eigenvalue equation (where || is the symbol for the determinant). The Hilbert-Polya conjecture is that the imaginary part of the Riemann zeta zeros are the eigenvalues of some unbounded self-adjoint operator.
I am not really sure what an unbounded self-adjoint operators is, but I have understood that a Hermitian matrix will do. Or in this case the infinite symmetric matrix $A.B$ starting:
$$A.B=\left( \begin{array}{ccccccc} 14.1347 & 14.1347 & 14.1347 & 14.1347 & 14.1347 & 14.1347 & \dots\\ 14.1347 & 35.1568 & 14.1347 & 35.1568 & 14.1347 & 35.1568 \\ 14.1347 & 14.1347 & 39.1456 & 14.1347 & 14.1347 & 39.1456 \\ 14.1347 & 35.1568 & 14.1347 & 65.5816 & 14.1347 & 35.1568 \\ 14.1347 & 14.1347 & 14.1347 & 14.1347 & 47.0698 & 14.1347 \\ 14.1347 & 35.1568 & 39.1456 & 35.1568 & 14.1347 & 97.7538 \\ \vdots & & & & & & \ddots \end{array} \right)$$
The solutions to the equation:
$$|A.B-A x|=0$$
are exactly the imaginary parts of the Riemann zeta zeros, as shown by this Mathematica program:
Clear[x, polynomial, A, B];
TableForm[polynomial = Table[
A = Table[Table[If[Mod[n, k] == 0, 1, 0], {k, 1, nn}], {n, 1, nn}];
B = Table[
Table[If[Mod[k, n] == 0, Im[ZetaZero[n]], 0], {k, 1, nn}], {n, 1,
nn}];
x /. Solve[Det[A.B - x*A] == 0, x], {nn, 1, 6}]]
MatrixForm[N[A.B]];
with the output:
{14.1347, 21.022, 25.0109, 30.4249, 32.9351, 37.5862}
But that is not very surprising because we have merely stated a way of doing Möbius inversion by finding the roots of the mentioned polynomial.
If you still are interested in zeta zeros as eigenvalues, then I say that it is the same matrix that comes closest, only the equation to solve becomes:
$$|A.B-xI|=0$$ or: $$|A.B-\lambda I|=0$$ with $\lambda$ instead of $x$, as more commonly seen.
My question is: What is meant by the unbounded self-adjoint operator in the Hilbert-Polya conjecture if not the associated determinant to the polynomials $p_1$ to $p_k$?:
$$\begin{array}{l} p_1 = \Im(\rho _1)-x \\ p_2 = (x-\Im(\rho _1)) (x-\Im(\rho _2)) \\ p_3 = -(x-\Im(\rho _1)) (x-\Im(\rho _2)) (x-\Im(\rho _3)) \\ p_4 = (x-\Im(\rho _1)) (x-\Im(\rho _2)) (x-\Im(\rho _3)) (x-\Im(\rho _4)) \\ p_5 = -(x-\Im(\rho _1)) (x-\Im(\rho _2)) (x-\Im(\rho _3)) (x-\Im(\rho _4)) (x-\Im(\rho _5)) \\ p_6 = (x-\Im(\rho _1)) (x-\Im(\rho _2)) (x-\Im(\rho _3)) (x-\Im(\rho _4)) (x-\Im(\rho _5)) (x-\Im(\rho _6)) \end{array}$$
with the simple definition:
$$p_k = (-1)^k \prod _{n=1}^k (x-\Im(\rho _n))$$
There is a factor $(-1)^k$ which I don't know where it comes from other than that it comes from this program:
Clear[x, polynomial, A, B];
TableForm[polynomial = Table[
A = Table[Table[If[Mod[n, k] == 0, 1, 0], {k, 1, nn}], {n, 1, nn}];
B = Table[
Table[If[Mod[k, n] == 0, Im[ZetaZero[n]], 0], {k, 1, nn}], {n, 1,
nn}];
Factor[Det[A.B - x*A]], {nn, 1, 6}]]
The zeros to the polynomials are the same, the Riemann zeta zeros, anyways.
I and others too can think of other determinants that are directly related to Riemann zeta zeros as eigenvalues, but they appear to be both tautological and degenerate.
This matrix $A.B$ is also tautological.
Also, can there be better determinants than the one shown here, and is this matrix $A.B$ degenerate?