diff --git a/latex/sections/methods.tex b/latex/sections/methods.tex index 0b4bc61..9376258 100644 --- a/latex/sections/methods.tex +++ b/latex/sections/methods.tex @@ -3,62 +3,65 @@ \begin{document} \section{Methods}\label{sec:methods} \subsection{The Ising model}\label{sec:ising_model} +% Add definitions + +We will assume a $2 \times 2$ lattice to study the possible system states, and +to find analytical expressions necessary in the Markov Chain Monte Carlo method. +These results are used to test our code during implementation. % Problem 1 -\begin{align*} - Z &= \sum_{all \ s_{i}}^{N} e^{-\beta E(\mathbf{s})} \\ - &= \dots \\ - &= 4 \cosh (8 \beta J) + 12 \\ -\end{align*} + +\begin{equation}\label{eq:partition_function} + Z = 4 \cosh (8 \beta J) + 12, +\end{equation} % -\begin{align*} - \langle \epsilon \rangle &= \frac{-2J \sinh(8 \beta J)}{ \cosh(8 \beta J) + 3} -\end{align*} +\begin{equation}\label{eq:energy_spin_first} + \langle \epsilon \rangle = \frac{-2J \sinh(8 \beta J)}{ \cosh(8 \beta J) + 3} +\end{equation} % -\begin{align*} - \langle \epsilon^{2} \rangle &= \frac{4 J^{2} \cosh(8 \beta J)}{\cosh(8 \beta J) + 3} -\end{align*} +\begin{equation}\label{eq:energy_spin_second} + \langle \epsilon^{2} \rangle = \frac{4 J^{2} \cosh(8 \beta J)}{\cosh(8 \beta J) + 3} +\end{equation} % -\begin{align*} - \langle |m| \rangle &= \frac{e^{8 \beta J} + 1}{2( \cosh(8 \beta J) + 3)} -\end{align*} -\begin{align*} - \langle |m|^{2} \rangle &= \frac{e^{8 \beta J} + 1}{2( \cosh(8 \beta J) + 3)} -\end{align*} +\begin{equation}\label{eq:magnetization_spin_first} + \langle |m| \rangle = \frac{e^{8 \beta J} + 1}{2( \cosh(8 \beta J) + 3)} +\end{equation} % -\begin{align*} - \langle E \rangle &= \frac{-8 J \sinh(8 \beta J)}{\cosh(8 \beta J) + 3} -\end{align*} +\begin{equation}\label{eq:magnetization_spin_second} + \langle |m|^{2} \rangle = \frac{e^{8 \beta J} + 1}{2( \cosh(8 \beta J) + 3)} +\end{equation} % -\begin{align*} - \langle E \rangle^{2} &= \frac{64 J^{2} \sinh(8 \beta J)}{(\cosh(8 \beta J) + 3)^{2}} -\end{align*} +\begin{equation}\label{eq:energy_total_first} + \langle E \rangle = \frac{-8 J \sinh(8 \beta J)}{\cosh(8 \beta J) + 3} +\end{equation} % -\begin{align*} - \langle E^{2} \rangle &= \frac{64 J^{2} \cosh(8 \beta J)}{\cosh(8 \beta J) + 3} -\end{align*} +\begin{equation}\label{eq:energy_total_first_squared} + \langle E \rangle^{2} = \frac{64 J^{2} \sinh(8 \beta J)}{(\cosh(8 \beta J) + 3)^{2}} +\end{equation} % -\begin{align*} - \langle M \rangle &= \frac{2 e^{8 \beta J}}{\cosh(8 \beta J) + 3} -\end{align*} +\begin{equation}\label{eq:energy_total_second} + \langle E^{2} \rangle = \frac{64 J^{2} \cosh(8 \beta J)}{\cosh(8 \beta J) + 3} +\end{equation} % -\begin{align*} - \langle M \rangle^{2} &= \frac{4e^{16 \beta J} + 16e^{8 \beta J} + 16}{(\cosh(8 \beta J) + 3)^{2}} -\end{align*} +\begin{equation}\label{eq:magnetization_total_first} + \langle |M| \rangle = \frac{2 e^{8 \beta J}}{\cosh(8 \beta J) + 3} +\end{equation} % -\begin{align*} - \langle M^{2} \rangle &= \frac{8e^{8 \beta J} + 8}{\cosh(8 \beta J) + 3} -\end{align*} +\begin{equation}\label{eq:magnetization_total_first_squared} + \langle |M| \rangle^{2} = \frac{4e^{16 \beta J} + 16e^{8 \beta J} + 16}{(\cosh(8 \beta J) + 3)^{2}} +\end{equation} % -\begin{align*} - C_{V} &= \frac{64 J^{2}}{N k_{\text{B}} T^{2}} \Big( \frac{3 \cosh(8 \beta J) + \cosh^{2}(8 \beta J) - \sinh^{2}(8 \beta J)}{(\cosh(8 \beta J) + 3)^{2}} \Big) -\end{align*} +\begin{equation}\label{eq:magnetization_total_second} + \langle M^{2} \rangle = \frac{8e^{8 \beta J} + 8}{\cosh(8 \beta J) + 3} +\end{equation} % -\begin{align*} - \chi &= \frac{1}{N} \frac{1}{k_{\text{B}} T^{2}} (\langle M^{2} \rangle - \langle M \rangle^{2}) \\ - &= \frac{1}{N k_{\text{B}} T} \Big( \frac{12e^{8 \beta J} + 4 e^{-8 \beta J} + 12}{(\cosh(8 \beta J) + 3)^{2}} \Big) -\end{align*} -The derivation of analytical expressions can be found in appendix -\ref{sec:analytical_expressions} +\begin{equation}\label{eq:specific_heat_capacity} + C_{V} = \frac{64 J^{2}}{N k_{\text{B}} T^{2}} \Big( \frac{3 \cosh(8 \beta J) + \cosh^{2}(8 \beta J) - \sinh^{2}(8 \beta J)}{(\cosh(8 \beta J) + 3)^{2}} \Big) +\end{equation} +% +\begin{equation}\label{eq:sesceptibility} + \chi = \frac{1}{N k_{\text{B}} T} \Big( \frac{12e^{8 \beta J} + 4 e^{-8 \beta J} + 12}{(\cosh(8 \beta J) + 3)^{2}} \Big) +\end{equation} +The derivation of analytical expressions can be found in appendix \ref{sec:analytical_expressions}. \subsection{Markov Chain Monte Carlo methods}\label{sec:mcmc_methods}