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luke naylor latex documents
research
Max Destabilizer Rank
Commits
1a27cd54
Commit
1a27cd54
authored
5 months ago
by
Luke Naylor
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Add some texlab directives to ignore erroneous diagnostics
parent
806b2648
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#48221
failed
4 months ago
Stage: test
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tex/bounds-on-semistabilisers.tex
+507
-506
507 additions, 506 deletions
tex/bounds-on-semistabilisers.tex
tex/computing-solutions.tex
+32
-27
32 additions, 27 deletions
tex/computing-solutions.tex
with
539 additions
and
533 deletions
tex/bounds-on-semistabilisers.tex
+
507
−
506
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1a27cd54
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tex/computing-solutions.tex
+
32
−
27
View file @
1a27cd54
...
...
@@ -13,7 +13,7 @@ a different algorithm will be presented making use of theorems from Section
with the goal of cutting down the run time.
\subsubsection
{
Finding possible
\texorpdfstring
{$
r
$}{
r
}
and
\texorpdfstring
{$
c
$}{
c
}}
\texorpdfstring
{$
c
$}{
c
}}
To do this, first calculate the upper bound
$
r
_{
\mathrm
{
max
}}$
on the ranks of tilt
semistabilisers, as given by Theorem
\ref
{
thm:loose-bound-on-r
}
.
...
...
@@ -36,7 +36,7 @@ the Bogomolov inequalities and Consequence 3 of Lemma
(
$
\chern
_
2
^{
\beta
_{
-
}}
(
u
)
>
0
$
).
\subsubsection
{
Finding
\texorpdfstring
{$
d
$}{
d
}
for fixed
\texorpdfstring
{$
r
$}{
r
}
and
\texorpdfstring
{$
c
$}{
c
}}
and
\texorpdfstring
{$
c
$}{
c
}}
$
\Delta
(
u
)
\geq
0
$
induces an upper bound
$
\frac
{
c
^
2
}{
2
r
}$
on
$
d
$
, and the
$
\chern
_
2
^{
\beta
_{
-
}}
(
u
)
>
0
$
condition induces a lower bound on
$
d
$
.
...
...
@@ -51,8 +51,8 @@ end up not yielding any solutions for the problem.
In fact, solutions
$
u
$
to our problem with high rank must have
$
\mu
(
u
)
$
close to
$
\beta
_{
-
}
(
v
)
$
:
\begin{align*}
0
&
\leq
\chern
_
1
^{
\beta
_{
-
}}
(u)
\leq
\chern
_
1
^{
\beta
_{
-
}}
(u)
\\
0
&
\leq
\mu
(u) -
\beta
_{
-
}
\leq
\frac
{
\chern
_
1
^{
\beta
_{
-
}}
(v)
}{
r
}
0
&
\leq
\chern
_
1
^{
\beta
_{
-
}}
(u)
\leq
\chern
_
1
^{
\beta
_{
-
}}
(u)
\\
0
&
\leq
\mu
(u) -
\beta
_{
-
}
\leq
\frac
{
\chern
_
1
^{
\beta
_{
-
}}
(v)
}{
r
}
\end{align*}
In particular, it is the
$
\chern
_
1
^{
\beta
_{
-
}}
(
v
-
u
)
\geq
0
$
condition which
fails for
$
r
$
,
$
c
$
pairs with large
$
r
$
and
$
\frac
{
c
}{
r
}$
too far from
$
\beta
_{
-
}$
.
...
...
@@ -66,17 +66,17 @@ alternative algorithm which will later be described in Section
\ref
{
sect:prob2-algorithm
}
.
\begin{center}
\label
{
table:bench-schmidt-vs-nay
}
\begin{tabular}
{
|r|l|l|
}
\hline
Choice of
$
v
$
on
$
\mathbb
{
P
}^
2
$
&
$
(
3
,
2
\ell
,
-
2
)
$
&
$
(
3
,
2
\ell
,
-
\frac
{
15
}{
2
}
)
$
\\
\hline
\cite
[\texttt{tilt.walls_left}]
{
SchmidtGithub2020
}
exec time
&
\sim
20s
&
>1hr
\\
\cite
{
NaylorRust2023
}
exec time
&
\sim
50ms
&
\sim
50ms
\\
\hline
\end{tabular}
\label
{
table:bench-schmidt-vs-nay
}
\begin{tabular}
{
|r|l|l|
}
\hline
Choice of
$
v
$
on
$
\mathbb
{
P
}^
2
$
&
$
(
3
,
2
\ell
,
-
2
)
$
&
$
(
3
,
2
\ell
,
-
\frac
{
15
}{
2
}
)
$
\\
\hline
\cite
[\texttt{tilt.walls_left}]
{
SchmidtGithub2020
}
exec time
&
\sim
20s
&
>1hr
\\
\cite
{
NaylorRust2023
}
exec time
&
\sim
50ms
&
\sim
50ms
\\
\hline
\end{tabular}
\end{center}
\section
{
Computing Solutions to Problem
\ref
{
problem:problem-statement-2
}}
...
...
@@ -94,7 +94,7 @@ The algorithm yields solutions
$
u
=(
r,c
\ell
,d
\ell
^
2
)
$
to the problem as follows.
\subsubsection
{
Iterating Over Possible
\texorpdfstring
{$
q
=
\chern
^{
\beta
_{
-
}}
(
u
)
$}{
q
}}
\texorpdfstring
{$
q
=
\chern
^{
\beta
_{
-
}}
(
u
)
$}{
q
}}
Given a Chern character
$
v
$
, the domain of the problem are first verified: that
$
v
$
has positive rank, that it satisfies
$
\Delta
(
v
)
\geq
0
$
, and that
...
...
@@ -102,6 +102,7 @@ $\beta_{-}(v)$ is rational.
Take
$
\beta
_{
-
}
(
v
)=
\frac
{
a
_
v
}{
n
}$
in simplest terms.
Iterate over
$
q
=
\frac
{
b
_
q
}{
n
}
\in
(
0
,
\chern
_
1
^{
\beta
_{
-
}}
(
v
))
\cap\frac
{
1
}{
n
}
\ZZ
$
.
The code used to generate the corresponding values for
$
b
_
q
$
is shown in Listing
% texlab: ignore
\ref
{
fig:code:consideredb
}
.
\lstinputlisting
[
...
...
@@ -118,6 +119,7 @@ We can therefore reduce the problem of finding solutions to the more specialised
problem of finding the solutions
$
u
$
with each fixed possible
$
q
=
\chern
_
1
^
\beta
(
u
)
$
(i.e. choice of
$
b
$
).
The code representing this appears in Listing
% texlab: ignore
\ref
{
fig:code:reducingtoeachb
}
.
Line 16 refers to creating an objects representing the context the specialised
problem for the fixed
$
q
$
value, with the next line `solving' the specialised
...
...
@@ -133,9 +135,9 @@ and collect up the results.
]
{
../tilt.rs/src/tilt
_
stability/find
_
all.git-untrack.rs.tex.git-untrack
}
\subsubsection
{
Iterating Over Possible
\texorpdfstring
{$
r
=
\chern
_
0
(
u
)
$}{
r
}
for Fixed
\texorpdfstring
{$
q
=
\chern
^{
\beta
_{
-
}}
(
u
)
$}{
q
}
\texorpdfstring
{$
r
=
\chern
_
0
(
u
)
$}{
r
}
for Fixed
\texorpdfstring
{$
q
=
\chern
^{
\beta
_{
-
}}
(
u
)
$}{
q
}
}
Let
$
q
=
\frac
{
b
_
q
}{
n
}$
, for which we are now solving the more specialised problem of finding
...
...
@@ -159,6 +161,7 @@ Fixing $r$ and $q$ also determines $c\coloneqq\chern_1(u)$, and so we can genera
the corresponding values of
$
c
$
, as we generate the
$
r
$
values.
It now remains to solve the problem for each of the combinations of fixed values
for
$
q
$
and
$
r
$
(and consequently
$
c
$
) considered.
% texlab: ignore
This is shown in Listing
\ref
{
fig:code:reducingtoeachr
}
.
\lstinputlisting
[
...
...
@@ -170,11 +173,11 @@ This is shown in Listing \ref{fig:code:reducingtoeachr}.
\subsubsection
{
Iterating Over Possible
\texorpdfstring
{$
d
=
\chern
_
2
(
u
)/
\ell
^
2
$}{
d
}
for Fixed
\texorpdfstring
{$
r
=
\chern
_
0
(
u
)
$}{
r
}
and
\texorpdfstring
{$
q
=
\chern
^{
\beta
_{
-
}}
(
u
)
$}{
q
}
\texorpdfstring
{$
d
=
\chern
_
2
(
u
)/
\ell
^
2
$}{
d
}
for Fixed
\texorpdfstring
{$
r
=
\chern
_
0
(
u
)
$}{
r
}
and
\texorpdfstring
{$
q
=
\chern
^{
\beta
_{
-
}}
(
u
)
$}{
q
}
}
At this point we are considering a specialisation of the problem
...
...
@@ -198,8 +201,10 @@ equivalent to bounds on $d$ given by the equations
in Subsubsection
\ref
{
subsubsect:all-bounds-on-d-prob2
}
It therefore remains to just pick values
$
d
\in\frac
{
1
}{
\lcm
(
m,
2
n
^
2
)
}
\ZZ
$
within the bounds.
% texlab: ignore
Listing
\ref
{
fig:code:solveforfixedr
}
is the code for solving this
specialisation of the problem, where the possible
$
d
$
values are computed in
% texlab: ignore
Listing
\ref
{
fig:code:possible
_
chern2
}
.
The explicit code for the bounds can be found in Appendix
\ref
{
appendix:subsubsec:fixed-r
}
.
...
...
@@ -232,11 +237,11 @@ decrease in computational time to find the solutions to the problem.
This could be due to a range of potential reasons:
\begin{itemize}
\item
Unexpected optimisations from the compiler for a certain form of the
program.
program.
\item
Increased complexity to computing the formulae for the tighter bounds.
\item
Modern CPU architecture such as branch predictors
\cite
{
BranchPredictor2024
}
may offset the overhead of considering ranks that
turn out to be too large to have any solutions.
\cite
{
BranchPredictor2024
}
may offset the overhead of considering ranks that
turn out to be too large to have any solutions.
\end{itemize}
For relatively small Chern characters (as those appearing in examples so far),
...
...
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