diff --git a/main.tex b/main.tex index 482ec559ebfbd664f3e338f0206e9e37e1a28f41..ab36005bab3e17ef93edb3258ec08c401e80e336 100644 --- a/main.tex +++ b/main.tex @@ -341,6 +341,100 @@ Notice that for $\beta = \beta_{-}$ (or $\beta_{+}$), that is when $\chern^{\beta}_2(F)=0$, the constant and linear terms match up with the ones for the bound found for $d$ in subsection \ref{subsect-d-bound-bgmlv1}. +\subsection{$\Delta(G) \geq 0$} +\label{subsect-d-bound-bgmlv3} + +This condition expressed in terms of $R,C,D,r,c,d$ looks as follows: + +\begin{sagesilent} + # Third Bogomolov-Gieseker form expression that must be non-negative: + bgmlv3 = Δ(v-u) +\end{sagesilent} + +\begin{equation} + \sage{0 <= bgmlv3.expand() } +\end{equation} + + +\noindent +Expressing $c$ in terms of $q$ as defined in (eqn \ref{eqn-cintermsofm}) +we get the following: + +\begin{sagesilent} + bgmlv3_with_q = bgmlv3.expand().subs(c == c_in_terms_of_q) +\end{sagesilent} + +\begin{equation} + \sage{0 <= bgmlv3_with_q} +\end{equation} + + +\noindent +This can be rearranged to express a bound on $d$ as follows: + +\begin{sagesilent} + var("r_alt",domain="real") # r_alt = r - R temporary substitution + + bgmlv3_with_q_reparam = ( + bgmlv3_with_q.subs(r == r_alt + R) + /r_alt # This operation assumes r_alt > 0 + ).expand() + bgmlv3_d_ineq = ( + ((0 <= bgmlv3_with_q_reparam)/2 + d) # Rearrange for d + .subs(r_alt == r - R) # Resubstitute r back in + .expand() + ) + # Check that this equation represents a bound for d + assert bgmlv3_d_ineq.lhs() == d, f"Inequality is of the form: {bgmlv3_d_ineq}" + bgmlv3_d_upperbound = bgmlv3_d_ineq.rhs() # Keep hold of lower bound for d +\end{sagesilent} + +\begin{dmath} + \label{eqn-bgmlv3_d_upperbound} + \sage{bgmlv3_d_ineq} +\end{dmath} + +\begin{sagesilent} + # Seperate out the terms of the lower bound for d + + bgmlv3_d_upperbound_without_hyp = bgmlv3_d_upperbound.subs(1/(R-r) == 0) + bgmlv3_d_upperbound_const_term = bgmlv3_d_upperbound_without_hyp.subs(r==0) + bgmlv3_d_upperbound_linear_term = ( + bgmlv3_d_upperbound_without_hyp + - bgmlv3_d_upperbound_const_term + ).expand() + bgmlv3_d_upperbound_exp_term = ( + bgmlv3_d_upperbound + - bgmlv3_d_upperbound_without_hyp + ).expand() + + # Verify the simplified forms of the terms that will be mentioned in text + assert bgmlv3_d_upperbound_const_term == ( + v.twist(beta_min).ch[2] + + beta_min*q + ).expand() +\end{sagesilent} + +Hyperbolic term: +\begin{equation} + \sage{bgmlv3_d_upperbound_exp_term} +\end{equation} + +\noindent +Viewing equation \ref{eqn-bgmlv3_d_upperbound} as an upper bound for $d$ give: +as a function of $r$, the terms can be rewritten as follows. +The constant term in $r$ is +$\chern^{\beta}_2(F) + \beta q$. +The linear term in $r$ is +$\sage{bgmlv3_d_upperbound_linear_term}$. +Finally, there's an hyperbolic term in $r$ which tends to 0 as $r \to \infty$, +and can be written: +$?$. +In the case $\beta = \beta_{-}$ (or $\beta_{+}$) we have +$\chern^{\beta}_2(F) = 0$, +so some of these expressions simplify, and in particular, the constant and +linear terms match those of the other bounds in the previous subsections. + \section{Conclusion} \newpage