diff --git a/main.tex b/main.tex index 40e3314c70dac6db0e29d035a80f5bd8ae75470e..9a969a21eabc92f5d8a636fb51bac4da603eded6 100644 --- a/main.tex +++ b/main.tex @@ -153,20 +153,23 @@ $\chern(E) = (r,c,d)$ of some semistabilizer $E$. v = Chern_Char(*var("R C D", domain="real")) u = Chern_Char(*var("r c d", domain="real")) - - ts = stability.Tilt - - beta_min = min(map(lambda sol: sol.rhs(), - solve(ts(alpha=0).degree(v), ts().beta) - )) \end{sagesilent} -Here, we have $\beta_{-} = \sage{beta_min}$. Recall [ref] that $\chern_1^{\beta_{-}}$ has fixed bounds in terms of $\chern(F)$, and so we can write: +\begin{sagesilent} + ts = stability.Tilt + beta_min = var("beta", domain="real") + c_lower_bound = -(ts(beta=beta_min).rank(u)/ts().alpha).expand() + c + + var("m", domain="real") + c_val = c_lower_bound + m +\end{sagesilent} + \begin{equation} - \chern_1(E) = r\beta_{-} + m + \label{eqn-cintermsofm} + c=\chern_1(E) = \sage{c_val} \qquad 0 \leq m \leq \chern_1^{\beta_{-}}(F) \end{equation} @@ -175,13 +178,46 @@ $m \in \frac{1}{n} \ZZ \cap [0, \chern_1^{\beta_{-}}(F)]$. For the next subsections, we consider $m$ to be fixed with one of these values, and we shall be varying $\chern_0(E) = r$ to see when certain inequalities fail. + +\subsection{$\Delta(E) + \Delta(G) \leq \Delta(F)$} + +This condition expressed in terms of $R,C,D,r,c,d$ looks as follows: + \begin{sagesilent} - c_lower_bound = -(ts(beta=beta_min).rank(u)/ts().alpha).expand() + c + positive_condition = - u.Q_tilt() - (v-u).Q_tilt() + v.Q_tilt() +\end{sagesilent} - var("m", domain="real") - c_val = c_lower_bound + m +\begin{equation} + \sage{(0 <= positive_condition.expand() )} +\end{equation} + +Expressing $c$ in terms of $m$ as defined in (eqn \ref{eqn-cintermsofm}) +we get the following: + +\begin{sagesilent} + positive_condition = positive_condition.expand().subs(c == c_val) +\end{sagesilent} + +\begin{equation} + \sage{(0 <= positive_condition) + 2*R*d - 4*d*r} +\end{equation} + +This can be rearranged to express a bound on $d$ as follows: + +\begin{sagesilent} + var("r_alt",domain="real") + nc = (positive_condition.subs(r == r_alt + R/2)/r_alt).expand() + nc = ((0 > -nc) + 4*d)/4 # rearrange for d + nc = nc.subs(r_alt == r - R/2).expand() # resubs r back in \end{sagesilent} +\begin{footnotesize} +\begin{equation} + \sage{nc} +\end{equation} +\end{footnotesize} + +In the case $\beta = \beta_{-}$ (or $\beta_{+}$) this can be simplified.