diff --git a/main.tex b/main.tex index e456eadc90bc86d369595262e0b9ff098103ba06..32b58237c3354d56072d12b7ca7dcbeb1c0d8326 100644 --- a/main.tex +++ b/main.tex @@ -589,7 +589,7 @@ finding all pseudo-walls when $\beta_{-}\in\QQ$. In section [ref], a different algorithm will be presented making use of the later theorems in this article, with the goal of cutting down the run time. -\subsection{Strategy} +\subsection*{Problem statement} Goals: \begin{itemize} @@ -600,6 +600,7 @@ Goals: \item Stop when conditions fail \item method works same way for both rational beta_{-} but also for walls larger than certain amount +\end{itemize} Fix a Chern character $v$ with positive rank, $\Delta(v) \geq 0$, and $\beta_{-}(v) \in \QQ$. @@ -615,6 +616,9 @@ semistabilizers of actual sheaves. The Chern characters which destabilize `outwards' can be recovered as $v-u$ for each solution $u$ to the current problem. +\subsection*{Algorithm} + +\subsubsection*{Finding possible $r$ and $c$} To do this, first calculate the upper bound $r_{max}$ on the ranks of tilt semistabilizers, as given by theorem \ref{thm:loose-bound-on-r}. @@ -625,16 +629,27 @@ are no large than $r_{max}$ (giving a finite sequence). This can be done with Fa which there exist formulae to generate. These $\mu(u)$ values determine pairs $r,c$ up to multiples, we can then take -all multiples which satisy $0<r\geq r_{max}$. +all multiples which satisy $0<r\leq r_{max}$. We now have a finite sequence of pairs $r,c$ for which there might be a solution -to our problem. In particular, any $(r,c\ell,d\ell^2)$ satisfies consequence 2 -of lemma \ref{lem:pseudo_wall_numerical_tests}, and the positive rank condition. +$(r,c\ell,d\ell^2)$ to our problem. In particular, any $(r,c\ell,d\ell^2)$ +satisfies consequence 2 of lemma \ref{lem:pseudo_wall_numerical_tests}, and the +positive rank condition. What remains is to find the $d$ values which satisfy +the Bogomolov inequalities and consequence 3 of lemma +\ref{lem:pseudo_wall_numerical_tests} +($\chern_2^{\beta_{-}}(u)>0$). + + +\subsubsection*{Finding $d$ for fixed $r$ and $c$} + +$\Delta(u) \geq 0$ induces an upper bound $\frac{c^2}{2r}$ on $d$, and the +$\chern_2^{\beta_{-}}(u)>0$ condition induces a lower bound on $d$. +The values in the range can be tested individually, to check that +the rest of the conditions are satisfied. -\end{itemize} -\subsection{Limitations} +\subsection*{Limitations} Goals: \begin{itemize}