diff --git a/main.tex b/main.tex index 8205f8693e8f18c4f8d15fa06bf36549f1e2da95..bda37b37c5fc99d08cb5af09a8a7d5ca4ff79510 100644 --- a/main.tex +++ b/main.tex @@ -27,6 +27,7 @@ \newtheorem{corrolary}{Corrolary}[section] \newtheorem{lemmadfn}{Lemma/Definition}[section] \newtheorem{dfn}{Definition}[section] +\newtheorem{lemma}{Lemma}[section] \begin{document} @@ -199,7 +200,7 @@ If $(\alpha,\beta)$, is on the hyperbola $\chern_2^{\alpha, \beta}(v)=0$, then for any $u$, $u$ is a pseudo-semistabilizer of $v$ iff $\mu_{\alpha,\beta}(u)=0$, and hence $\chern_2^{\alpha, \beta}(u)=0$. In fact, this allows us to use the characteristic curves of some $v$ and $u$ -(with $\Delta(v)\geq 0$, $\Delta(u)\geq 0$ and positive ranks) to determine the +(with $\Delta(v), \Delta(u)\geq 0$ and positive ranks) to determine the location of the pseudo-wall where $u$ pseudo-semistabilizes $v$. %TODO ref forwards @@ -209,8 +210,48 @@ consequence of $\Delta(v)\geq 0$. Furthermore the assymptotes are angled at $\pm 45^\circ$, crossing through the base of the first characteristic curve $\chern_1^{\alpha,\beta}=0$ (vertical line). +\subsection{Bertram's nested wall theorem} +Although Bertram's nested wall theorem can be proved more directly, it's also +important for the content of this document to understand the connection with +these characteristic curves. +Emanuele Macri noticed in (TODO ref) that any circular wall of $v$ reaches a critical +point on the second critical curve for $v$ ($\chern_2^{\alpha, \beta}(v)=0$), +this is a consequence of +$\frac{\delta}{\delta\beta} \chern_2^{\alpha,\beta} = -\chern_1^{\alpha,\beta}$. +This fact, along with the hindsight knowledge that non-vertical walls are +circles with centers on the $\beta$-axis, gives an alternative view to see that +the circular walls must be nested and non-intersecting. +\subsection{Characteristic curves for pseudo-semistabilizers} + +\begin{lemma}[Numerical tests for left-wall pseudo-semistabilizers] +Let $v$ and $u$ be Chern characters with $\Delta(v), \Delta(u)\geq 0$ and +positive ranks. + +Suppose that $u$ gives rise to a pseudo-wall for $v$, left of the characteristic +vertical line $\chern_1^{\alpha,\beta}(v)=0$ and containing a fixed point $p$ in +it's interior. +To target all left-walls, $p$ can be chosen as the base of the left branch of +the hyperbola $\chern_2^{\alpha,\beta}(v)=0$. +Suppose further that this happens in a way such that $u$ destabilizes $v$ going +`inwards', that is, +$\nu_{\alpha,\beta}(u)<\nu_{\alpha,\beta}(v)$ outside the pseudo-wall, and +$\nu_{\alpha,\beta}(u)>\nu_{\alpha,\beta}(v)$ inside. + + +\noindent +Then we have the following: +\begin{itemize} + \item The pseudo-wall is left of $u$'s vertical characteristic line + (if this is a real wall then $v$ is being semistabilized by a positive rank object) + \item $\mu(u)<\mu(v)$, i.e., $u$'s vertical characteristic line is left of $v$'s vertical + characteristic line + \item $\chern_2^{p}(u)>0$ +\end{itemize} +Furthermore, only the last two of these consequences are sufficient to recover +all of the suppositions above. +\end{lemma}