diff --git a/main.tex b/main.tex index 8d98fc7b54e43e4c5a170787a4a53ec6b9a690c1..727da0b4fb21298ea58680d313e8141c72a97116 100644 --- a/main.tex +++ b/main.tex @@ -8,10 +8,15 @@ \usepackage{hyperref} \usepackage{color} +\newcommand{\QQ}{\mathbb{Q}} +\newcommand{\chern}{\operatorname{ch}} +\newcommand{\firsttilt}[1]{\mathcal{B}^{#1}} +\newcommand{\bddderived}{\mathcal{D}^{b}} \begin{document} -\title{Explicit Formulae for Maximal Ranks of Tilt Destabilizers} +\title{Explicit Formulae for Bounds on the Ranks of Tilt Destabilizers and +Practical Methods for Finding Pseudowalls} \author{Luke Naylor} @@ -19,6 +24,39 @@ \section{Introduction} +There are theoretical results [ref] that show that for any $\beta_0 \in \QQ$, +the vertical line $\{\sigma_{\alpha,\beta_0} \colon \alpha \in \QQ_{>0}\}$ only +intersects finitely many walls. A consequence of this is that if +$\beta_{-} \in \QQ$, then there can only be finitely many circular walls to the +left of the vertical wall $\beta = \mu$. +On the other hand, when $\beta_{-} \not\in \QQ$, [ref] showed that there are +infinitely many walls. + +This dichotomy does not only hold for real walls, realised by actual objects in +$\bddderived(X)$, but also for pseudowalls. Here pseudowalls are defined as +`potential' walls, induced by hypothetical Chern characters of destabilizers +which satisfy certain numerical conditions which would be satisfied by any real +destabilizer, regardless of whether they are realised by actual elements of +$\bddderived(X)$. + +Since real walls are a subset of pseudowalls, the $\beta_{-} \not\in \QQ$ case +follows immediately from the corresponding case for real walls. +However, the $\beta_{-} \in \QQ$ case involves showing that the following +conditions only admit finitely many solutions (despite the fact that the same +conditions admit infinitely many solutions when $\beta_{-} \not\in \QQ$). + + +For a destabilizing sequence +$E \hookrightarrow F \twoheadrightarrow G$ in $\mathcal{B}^\beta$ +we have the following conditions. +There are some Bogomolov-Gieseker type inequalities: +$0 \leq \Delta(E), \Delta(G)$ and $\Delta(E) + \Delta(G) \leq \Delta(F)$. +We also have a condition relating to the tilt category $\firsttilt\beta$: +$0 \leq \chern^\beta_1(E) \leq \chern^\beta_1(F)$. +Finally, there's a condition ensuring that the radius of the circular wall is +strictly positive: $\chern^\beta_2(E) > 0$. + + \section{Section 1} \section{Section 2}