diff --git a/src/qmc-loop-algorithm-report.tex b/src/qmc-loop-algorithm-report.tex index a7064a38522fa01faa15e959a9d0528276fb3722..1c4f3f37d578087d5bbc02dad0d0550271660b98 100644 --- a/src/qmc-loop-algorithm-report.tex +++ b/src/qmc-loop-algorithm-report.tex @@ -162,7 +162,7 @@ \die{} = \num{0.63} > \num{0.45} \Rightarrow \text{decline} \end{align*} } -\only<5>{\Centering\includegraphics[width=0.56\linewidth]{bttf.jpg}} +\only<5| handout:0>{\Centering\includegraphics[width=0.56\linewidth]{bttf.jpg}} \only<1-4,6->{ \visible<7->{ Suggest to flip third site \(\vec{\sigma}_3 \overset{?}{=} \uparrow\uparrow\uparrow\uparrow\) @@ -253,14 +253,48 @@ Always accept the new configuration \blfootnote{\cite{Gubernatis2016}} \blfootnote{\cite{gehrbachelor}} \end{frame} +\begin{frame}{Interim Summary} +\begin{minipage}{0.48\linewidth} +\begin{block}{Problem} + \begin{itemize} + \item Exponential configuration space + \item Most configurations have \(\approx 0\) contribution + \end{itemize} +\end{block} +\begin{block}{Monte Carlo} + \begin{itemize} + \item Create Markov Chain with detailed-balance algorithm + \begin{itemize} + \item Metropolis + \item Heat-Bath + \end{itemize} + \item Calculate observable for each configuration in chain + \item Average of observable is expectation value + \item Use blocking analysis to get independent values + \end{itemize} +\end{block} +\end{minipage} +\hfill +\begin{minipage}{0.48\linewidth} +\begin{block}{Metropolis} + \begin{itemize} + \item Suggest a change to the last configuration \(C \to C'\) + \item Accept it with certain probability + \item If declined that means the old configuration \(C\) was re-sampled + \end{itemize} +\end{block} +\begin{block}{Heat-Bath} + \begin{itemize} + \item Local change in energy, by setting local values in the configuration + \item Set local value according to local Boltzmann distribution + \end{itemize} +\end{block} +\end{minipage} +\end{frame} \section{Quantum Monte Carlo} -\subsection{XXZ Quantum Spin Chain} -\subsection{Trotter Decomposition} -\subsection{Updating Schemes} -\subsection{Loop Updates} -\subsection{Sign Problem} \begin{frame}{Quantum Monte Carlo} \begin{minipage}{0.45\linewidth} +\subsection{XXZ Quantum Spin Chain} \begin{block}{XXZ Quantum Spin Chain} \begin{align*} H &= J_x \sum_i (S_i^xS_{i+1}^x + S_i^yS_{i+1}^y) + J_z\sum_i S_i^z S_{i+1}^z \\ @@ -295,6 +329,7 @@ Always accept the new configuration \end{minipage} \blfootnote{\cite{Assaad}} \end{frame} +\subsection{Trotter Decomposition} \begin{frame}{Trotter Decomposition} \begin{minipage}{0.5\linewidth} \begin{small} @@ -327,6 +362,7 @@ Always accept the new configuration \blfootnote{\cite{bchformula}} \blfootnote{\cite{Sandvik2010}} \end{frame} +\subsection{Updating Schemes} \begin{frame}{Updating Schemes} \begin{minipage}{0.48\linewidth} \begin{block}{Local Update} @@ -342,12 +378,13 @@ Always accept the new configuration \end{minipage} \hfill \begin{minipage}{0.48\linewidth} -\begin{block}{Single Loop Update} +\begin{block}{Local Loop Update} \includegraphics[width=0.98\linewidth]{singleloopupdate.pdf} \end{block} \end{minipage} \blfootnote{\cite{Assaad}} \end{frame} +\subsection{Loop Updates} \begin{frame}{Loop Updates} \begin{minipage}{0.48\linewidth} \includegraphics[width=\linewidth]{graphmap.pdf} @@ -364,6 +401,7 @@ Always accept the new configuration \end{minipage} \blfootnote{\cite{Assaad}} \end{frame} +\subsection{Sign Problem} \begin{frame}{Sign Problem} \begin{minipage}{0.48\linewidth} \begin{block}{Partition Sum} @@ -381,7 +419,7 @@ Always accept the new configuration \begin{block}{New Expectation Value} \begin{align*} \expval{O} - &= \tr\left(e^{-\beta H}O\right) \\ + &= \frac{1}{Z}\tr\left(e^{-\beta H}O\right) \\ &\overset{!}{=} \frac{\sum_Cw_CO_C}{\sum_Cw_C} = \frac{\sum_C\abs{w_C}\text{sign}_CO_C}{\sum_C\abs{w_C}\text{sign}_C} \\ &\approx \frac{\sum_{i=1}^{N} \text{sign}_{C_i}O_{C_i}}{\sum_{i=1}^{N} \text{sign}_{C_i}} @@ -390,9 +428,61 @@ Always accept the new configuration \end{minipage} \blfootnote{\cite{werner}} \end{frame} +\begin{frame}{Summary} +\begin{minipage}{0.48\linewidth} +\begin{block}{Problem} + \begin{itemize} + \item Exponential configuration space + \item Most configurations have \(\approx 0\) contribution + \end{itemize} +\end{block} +\begin{block}{Monte Carlo} + \begin{itemize} + \item Create Markov Chain with detailed-balance algorithm + \begin{itemize} + \item Metropolis + \item Heat-Bath + \end{itemize} + \item Calculate observable for each configuration in chain + \item Average of observable is expectation value + \item Use blocking analysis to get independent values + \end{itemize} +\end{block} +\end{minipage} +\hfill +\begin{minipage}{0.48\linewidth} +\begin{block}{Quantum Monte Carlo} +\begin{itemize} + \item Rewrite partition sum as sum of weights + \begin{align*} + Z = \tr(e^{-\beta H}) \overset{!}{=} \sum_C w_C + \end{align*} + \begin{itemize} + \item Maybe apply path integral + \begin{small} + \begin{align*} + Z = \sum_{C=(\vec{\sigma}_1,\hdots,\vec{\sigma}_N)}\bra{\vec{\sigma}_1}e^{-\Delta\tau H}\ket{\vec{\sigma}_2}\cdots\bra{\vec{\sigma}_N}e^{-\Delta\tau H}\ket{\vec{\sigma}_1} + \end{align*} + \end{small} + \item Apply Trotter decomposition if possible + \end{itemize} + \item Find corresponding formula for observables + \begin{align*} + \expval{O} = \frac{1}{Z}\tr(e^{-\beta H}O) \overset{!}{=} \frac{\sum_C w_CO_C}{\sum_Cw_C} + \end{align*} + \item Sample with classical Monte Carlo using \(\abs{w_C}\) + \item Pray to god that the sign problem is not too big +\end{itemize} +\end{block} +\end{minipage} +\end{frame} +\begin{frame}{The End} + \Centering + \Large{Thank you for your attention} +\end{frame} { - \nocite{*} + %\nocite{*} \printbibliography }