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luke naylor latex documents
research
Max Destabilizer Rank
Commits
33b1ac28
Commit
33b1ac28
authored
1 year ago
by
Luke Naylor
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Correct beta vs beta_{-} in loose bound theorem
parent
96ca695e
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!1
Draft: Resolve "Running example (3, 2l, -4)"
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33b1ac28
...
...
@@ -248,6 +248,7 @@ the circular walls must be nested and non-intersecting.
\subsection
{
Characteristic curves for pseudo-semistabilizers
}
\begin{lemma}
[Numerical tests for left-wall pseudo-semistabilizers]
\label
{
lem:pseudo
_
wall
_
numerical
_
tests
}
Let
$
v
$
and
$
u
$
be Chern characters with positive ranks and
$
\Delta
(
v
)
,
\Delta
(
u
)
\geq
0
$
. Let
$
P
$
be a point on
$
\Theta
_
v
^
-
$
.
...
...
@@ -470,18 +471,18 @@ normal one. So $0 \leq \Delta(E)$ yields:
\end{equation}
\begin{theorem}
[Bound on
$
r
$
- Benjamin Schmidt]
Given a Chern character
$
v
$
such that
$
\beta
_{
-
}
(
v
)
\in\QQ
$
, the rank
$
r
$
of
any semistabilizer
$
E
$
of some
$
F
\in
\firsttilt\beta
$
with
$
\chern
(
F
)=
v
$
is
Given a Chern character
$
v
$
such that
$
\beta
_
-
:
=
\beta
_
{
-
}
(
v
)
\in\QQ
$
, the rank
$
r
$
of
any semistabilizer
$
E
$
of some
$
F
\in
\firsttilt
{
\beta
_
-
}
$
with
$
\chern
(
F
)=
v
$
is
bounded above by:
\begin{equation*}
r
\leq
\frac
{
mn
^
2
\chern
^
\beta
_
1(v)
^
2
}{
\gcd
(m,2n
^
2)
}
r
\leq
\frac
{
mn
^
2
\chern
^
{
\beta
_
-
}_
1(v)
^
2
}{
\gcd
(m,2n
^
2)
}
\end{equation*}
\end{theorem}
\begin{proof}
The restrictions on
$
\chern
^
\beta
_
0
(
E
)
$
and
$
\chern
^
\beta
_
2
(
E
)
$
The restrictions on
$
\chern
^
{
\beta
_
-
}_
0
(
E
)
$
and
$
\chern
^
{
\beta
_
-
}_
2
(
E
)
$
is best seen with the following graph:
% TODO: hyperbola restriction graph (shaded)
...
...
@@ -489,18 +490,19 @@ is best seen with the following graph:
var("m") # Initialize symbol for variety parameter
\end{sagesilent}
This is where the rationality of
$
\beta
_{
-
}$
comes in. If
$
\beta
_{
-
}
=
\frac
{
*
}{
n
}$
for some
$
*
,n
\in
\ZZ
$
.
Then
$
\chern
^
\beta
_
2
(
E
)
\in
\frac
{
1
}{
\lcm
(
m,
2
n
^
2
)
}
\ZZ
$
where
$
m
$
is the integer
This is where the rationality of
$
\beta
_{
-
}$
comes in. If
$
\beta
_{
-
}
=
\frac
{
*
}{
n
}$
for some
$
*
,n
\in
\ZZ
$
.
Then
$
\chern
^
{
\beta
_
-
}_
2
(
E
)
\in
\frac
{
1
}{
\lcm
(
m,
2
n
^
2
)
}
\ZZ
$
where
$
m
$
is the integer
which guarantees
$
\chern
_
2
(
E
)
\in
\frac
{
1
}{
m
}
\ZZ
$
(determined by the variety).
In particular, since
$
\chern
_
2
(
E
)
>
0
$
we must also have
$
\chern
^
\beta
_
2
(
E
)
\geq
\frac
{
1
}{
\lcm
(
m,
2
n
^
2
)
}$
, which then in turn gives a bound
for the rank of
$
E
$
:
In particular, since
$
\chern
_
2
^{
\beta
_
-
}
(
E
)
>
0
$
(by using
$
P
=(
\beta
_
-
,
0
)
$
in
lemma
\ref
{
lem:pseudo
_
wall
_
numerical
_
tests
}
) we must also have
$
\chern
^{
\beta
_
-
}_
2
(
E
)
\geq
\frac
{
1
}{
\lcm
(
m,
2
n
^
2
)
}$
, which then in turn gives a
bound for the rank of
$
E
$
:
\begin{align}
\chern
_
0(E)
&
=
\chern
^
\beta
_
0(E)
\\
&
\leq
\frac
{
\lcm
(m,2n
^
2)
\chern
^
\beta
_
1(E)
^
2
}{
2
}
\\
&
\leq
\frac
{
mn
^
2
\chern
^
\beta
_
1(F)
^
2
}{
\gcd
(m,2n
^
2)
}
\chern
_
0(E)
&
=
\chern
^
{
\beta
_
-
}_
0(E)
\\
&
\leq
\frac
{
\lcm
(m,2n
^
2)
\chern
^
{
\beta
_
-
}_
1(E)
^
2
}{
2
}
\\
&
=
\frac
{
mn
^
2
\chern
^
{
\beta
_
-
}_
1(F)
^
2
}{
\gcd
(m,2n
^
2)
}
\end{align}
\end{proof}
...
...
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