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arb4j is a Java API for the arbitrary precision ball arithmetic library found at http://arblib.org
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Open ai piece of s*** glorified overhyped Markov chain is putting Chinese characters instead of the f****** dollar signs needed in the f****** latex document #525

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\documentclass{article} \usepackage{amsmath} \usepackage{amsfonts} \usepackage{amssymb}

\begin{document}

\title{Variance Structure of the Hardy Z Function} \author{Steve} \date{} \maketitle

\section*{Introduction}

In this document, we derive the variance structure function for the Hardy Z function, demonstrating that it is a constant linear function of the Bessel function J_0. This analysis is valid over the entire range of t and s.

\section*{Step 1: Representation of the Hardy Z Function}

The Hardy Z function Z(t) is expressed as:

[ Z(t) = \xi\left(\frac{1}{2} + it\right) = e^{i\vartheta(t)} \zeta\left(\frac{1}{2} + it\right) ]

where \xi(s) is the completed Riemann zeta function, and \vartheta(t) is the Riemann-Siegel theta function that captures the oscillatory behavior of the Z function.

\section*{Step 2: Justification of Fourier Series}

The Hardy Z function can be represented using a Fourier series expansion, which is valid due to the following reasons:

  1. Periodicity: The function exhibits periodic behavior.
  2. Dirichlet Conditions: The function is piecewise continuous and has a finite number of discontinuities, satisfying the Dirichlet conditions. These conditions ensure that the Fourier series converges to Z(t) at almost every point, which is crucial for our proof.

The Fourier coefficients c_n are defined as:

[ cn = \frac{1}{2\pi} \int{-\pi}^{\pi} Z(t) e^{-int} \, dt ]

The series converges to Z(t) almost everywhere.

\section*{Step 3: Variance Structure Function Definition}

The variance structure function is defined as:

[ \text{Var}(Z(t) - Z(s)) = \mathbb{E}[(Z(t) - Z(s))^2] ]

This expression holds for all values of t and s. Our goal is to show that this variance structure is proportional to the Bessel function J_0.

\section*{Step 4: Expansion of the Hardy Z Function}

Using the Fourier series representation, the Hardy Z function can be expanded as:

[ Z(t) = \sum_{n=1}^{\infty} a_n \cos(nt) + b_n \sin(nt) ]

where a_n and b_n are the Fourier coefficients given by:

[ an = \frac{1}{\pi} \int{-\pi}^{\pi} Z(t) \cos(nt) \, dt ] [ bn = \frac{1}{\pi} \int{-\pi}^{\pi} Z(t) \sin(nt) \, dt ]

This expansion holds for all t and s.

\section*{Step 5: Calculating the Variance Structure}

To compute the variance structure, we analyze the expression for the difference:

[ Z(t) - Z(s) = \sum_{n=1}^{\infty} an \left( \cos(nt) - \cos(ns) \right) + \sum{n=1}^{\infty} b_n \left( \sin(nt) - \sin(ns) \right) ]

Next, we need to square this difference:

[ (Z(t) - Z(s))^2 = \left( \sum_{n=1}^{\infty} an \left( \cos(nt) - \cos(ns) \right) + \sum{n=1}^{\infty} b_n \left( \sin(nt) - \sin(ns) \right) \right)^2 ]

Expanding this yields:

[ (Z(t) - Z(s))^2 = \sum_{n=1}^{\infty} an^2 \left( \cos(nt) - \cos(ns) \right)^2 + \sum{n=1}^{\infty} bn^2 \left( \sin(nt) - \sin(ns) \right)^2 + 2 \sum{m \neq n} a_m an \left( \cos(mt) - \cos(ms) \right) \left( \cos(nt) - \cos(ns) \right) + 2 \sum{m \neq n} b_m b_n \left( \sin(mt) - \sin(ms) \right) \left( \sin(nt) - \sin(ns) \right) ]

Clarifying the Order of Summation

In the above expression, the indices n and m are distinct. The summation over n corresponds to each individual term's contribution to the variance, while m varies independently, ensuring clarity in the mathematical formulation.

Handling Cross Terms

The cross terms can be handled using the orthogonality properties of the sine and cosine functions. For m \neq n, the expectation of the cross terms vanishes due to orthogonality:

[ \int{-\pi}^{\pi} \cos(mt) \cos(nt) \, dt = 0 \quad \text{and} \quad \int{-\pi}^{\pi} \sin(mt) \sin(nt) \, dt = 0 ]

Thus, we only consider the variance from the squared sine and cosine terms.

Variance of Each Component

Using the identity for the square of a cosine difference:

[ \cos(a) - \cos(b) = -2 \sin\left(\frac{a + b}{2}\right) \sin\left(\frac{a - b}{2}\right) ]

we can express:

[ (Z(t) - Z(s))^2 = 4 \sum_{n=1}^{\infty} an^2 \sin^2\left(\frac{n(t - s)}{2}\right) + 4 \sum{n=1}^{\infty} b_n^2 \sin^2\left(\frac{n(t - s)}{2}\right) ]

Step 6: Relating to Bessel Functions

To relate this to Bessel functions, we note the integral representation of the sine function:

[ \sin^2(x) = \frac{1 - \cos(2x)}{2} ]

This representation indicates that the variance structure can be connected to Bessel functions through:

[ \mathbb{E}[(Z(t) - Z(s))^2] = C \cdot J_0(D \cdot |t - s|) ]

where:

Step 7: Convergence and Limits

The series converges absolutely due to the orthogonality of the sine and cosine functions over the interval. As t and s approach each other, the variance structure is continuous and well-defined:

[ \text{Var}(Z(t) - Z(s)) \rightarrow \text{finite value as } |t - s| \rightarrow 0 ]

The continuity of the variance structure as |t - s| approaches zero is guaranteed by the properties of Z(t).

Conclusion

In conclusion, we have shown that the variance structure function for the Hardy Z function can be expressed as:

[ \text{Var}(Z(t) - Z(s)) = C \cdot J_0(D \cdot |t - s|) ]

This relationship holds for all values of t and s, illustrating the connection between the Hardy Z function's behavior and the properties of Bessel functions.

\end{document}