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Commit c65b2e91 authored by Luke Naylor's avatar Luke Naylor
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Be more specific in definition of pseudo-semistabilizer

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......@@ -113,12 +113,27 @@ bounds on $\chern_0(E)$ of potential destabilizers $E$ of $F$.
Characters}
\begin{dfn}[Pseudo-semistabilizers]
Given a Chern Character $v$, and a given stability condition $\sigma$,
Given a Chern Character $v$ on a Picard rank 1 surface, and a given stability
condition $\sigma_{\alpha,\beta}$,
a pseudo-semistabilizing $u$ is a `potential' Chern character:
\[
u = \left(r, c\ell, d \frac{1}{2} \ell^2\right)
\]
which has the same tilt slope as $v$: $\mu_{\sigma}(u) = \mu_{\sigma}(v)$.
which has the same tilt slope as $v$: $\nu_{\alpha,\beta}(u) = \nu_{\alpha,\beta}(v)$.
\noindent
Furthermore the following Bogomolov-Gieseker inequalities are satisfied:
\begin{itemize}
\item $\Delta(u) \geq 0$
\item $\Delta(v-u) \geq 0$
\item $\Delta(u) + \Delta(v-u) \leq \Delta(v)$
\end{itemize}
\noindent
And finally these two conditions are satisfied:
\begin{itemize}
\item $\chern_1^{\beta}(u) \geq 0$
\item $\chern_1^{\beta}(v-u) \geq 0$
\end{itemize}
Note $u$ does not need to be a Chern character of an actual sub-object of some
object in the stability condition's heart with Chern character $v$.
......@@ -128,6 +143,14 @@ At this point, and in this document, we do not care about whether
pseudo-semistabilizers are even Chern characters of actual elements of
$\bddderived(X)$, some other sources may have this extra restriction too.
\begin{lemma}[ Sanity check for Pseudo-semistabilizers ]
Given a Picard rank 1 surface, and a given stability
condition $\sigma_{\alpha,\beta}$,
if $E\hookrightarrow F\twoheadrightarrow G$ is a semistabilizing sequence in
$\firsttilt\beta$ for $F$.
Then $\chern(E)$ is a pseudo-semistabilizer of $\chern(F)$
\end{lemma}
Considering the stability conditions with two parameters $\alpha, \beta$ on
Picard rank 1 surfaces.
We can draw 2 characteristic curves for any given Chern character $v$ with
......@@ -606,7 +629,7 @@ Fix a Chern character $v$ with positive rank, $\Delta(v) \geq 0$,
and $\beta_{-}(v) \in \QQ$.
The goal is to find all Chern characters $u=(r,c\ell,d\ell^2)$ which satisfy the
conditions of lemma \ref{lem:pseudo_wall_numerical_tests} using
$P=(\beta_{-},0)$, as well as the Bogomolov inequalities:
$P=(\beta_{-},0)$, $\chern_1^{\beta_{-}}(v-u)\geq 0$, as well as the Bogomolov inequalities:
$\Delta(u),\Delta(v-u) \geq 0$ and $\Delta(u)+\Delta(v-u) \leq \Delta(v)$.
We want to restrict our attention to pseudo-walls left of $V_v$ (condition (a) of
lemma), because this is the side of $V_v$ containing the chamber for Gieseker
......
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