Explicit Riemann Hilbert correspondenceTerminology of “covariant derivative” and various...



Explicit Riemann Hilbert correspondence


Terminology of “covariant derivative” and various “connections”regular singularitiesKernel of an integrable holomorphic dee-bar connection is a holomorphic vector bundleAnalogy between connections and $ell$-adic sheaves: what happens with the residue?Existence of flat connections via characteristic classes, for nice groupsDo we have classical Riemann-Hilbert correspondence for infinite dimensional flat vector bundles?Kernel of a non-integrable connectionRiemann-Hilbert correspondence for non-flat connectionsConnection 1-form of the frame bundle associated to a vector bundle with a connectionInducing linear connections via functors













3












$begingroup$


For simplicity, we assume that $X=mathbb P_{mathbb C}^1-{s_1, s_2, dots, s_k}$ and $infty in X$.
Consider the trivial bundle $E=mathcal O_X^r$ with the connection $nabla$ induced by a Fushcian system on $X$, i.e.
$$nabla:= d+sum_{i=1}^k frac{A_i}{z-s_i},$$
where $A_i$'s are $rtimes r$ constant matrices over $mathbb C$.
Then we have a flat bundle with connection (or a logarithmic connection).
My question is that what is the corresponding monodromy representation to $(E,nabla)$ via the Riemann Hilbert correspondence?
The known part is that locally at each $z=s_i$, the monodromy $T_i$ can be obtained by the residue map: $T_i=exp(2pi i A_i)$, but this seems not to admit a unique representation up to isomorphism.
Is there any more properties/facts around the question?










share|cite|improve this question









$endgroup$








  • 1




    $begingroup$
    You cannot solve ode "explicitly" - so cannot find explicit monodromies. Rare exceptions like Knizhnik-Zamolodchikov equation are due some hidden Lie group symmetry inside.
    $endgroup$
    – Alexander Chervov
    3 hours ago


















3












$begingroup$


For simplicity, we assume that $X=mathbb P_{mathbb C}^1-{s_1, s_2, dots, s_k}$ and $infty in X$.
Consider the trivial bundle $E=mathcal O_X^r$ with the connection $nabla$ induced by a Fushcian system on $X$, i.e.
$$nabla:= d+sum_{i=1}^k frac{A_i}{z-s_i},$$
where $A_i$'s are $rtimes r$ constant matrices over $mathbb C$.
Then we have a flat bundle with connection (or a logarithmic connection).
My question is that what is the corresponding monodromy representation to $(E,nabla)$ via the Riemann Hilbert correspondence?
The known part is that locally at each $z=s_i$, the monodromy $T_i$ can be obtained by the residue map: $T_i=exp(2pi i A_i)$, but this seems not to admit a unique representation up to isomorphism.
Is there any more properties/facts around the question?










share|cite|improve this question









$endgroup$








  • 1




    $begingroup$
    You cannot solve ode "explicitly" - so cannot find explicit monodromies. Rare exceptions like Knizhnik-Zamolodchikov equation are due some hidden Lie group symmetry inside.
    $endgroup$
    – Alexander Chervov
    3 hours ago
















3












3








3


1



$begingroup$


For simplicity, we assume that $X=mathbb P_{mathbb C}^1-{s_1, s_2, dots, s_k}$ and $infty in X$.
Consider the trivial bundle $E=mathcal O_X^r$ with the connection $nabla$ induced by a Fushcian system on $X$, i.e.
$$nabla:= d+sum_{i=1}^k frac{A_i}{z-s_i},$$
where $A_i$'s are $rtimes r$ constant matrices over $mathbb C$.
Then we have a flat bundle with connection (or a logarithmic connection).
My question is that what is the corresponding monodromy representation to $(E,nabla)$ via the Riemann Hilbert correspondence?
The known part is that locally at each $z=s_i$, the monodromy $T_i$ can be obtained by the residue map: $T_i=exp(2pi i A_i)$, but this seems not to admit a unique representation up to isomorphism.
Is there any more properties/facts around the question?










share|cite|improve this question









$endgroup$




For simplicity, we assume that $X=mathbb P_{mathbb C}^1-{s_1, s_2, dots, s_k}$ and $infty in X$.
Consider the trivial bundle $E=mathcal O_X^r$ with the connection $nabla$ induced by a Fushcian system on $X$, i.e.
$$nabla:= d+sum_{i=1}^k frac{A_i}{z-s_i},$$
where $A_i$'s are $rtimes r$ constant matrices over $mathbb C$.
Then we have a flat bundle with connection (or a logarithmic connection).
My question is that what is the corresponding monodromy representation to $(E,nabla)$ via the Riemann Hilbert correspondence?
The known part is that locally at each $z=s_i$, the monodromy $T_i$ can be obtained by the residue map: $T_i=exp(2pi i A_i)$, but this seems not to admit a unique representation up to isomorphism.
Is there any more properties/facts around the question?







connections d-modules monodromy local-systems






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share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked 5 hours ago









LongmaLongma

282




282








  • 1




    $begingroup$
    You cannot solve ode "explicitly" - so cannot find explicit monodromies. Rare exceptions like Knizhnik-Zamolodchikov equation are due some hidden Lie group symmetry inside.
    $endgroup$
    – Alexander Chervov
    3 hours ago
















  • 1




    $begingroup$
    You cannot solve ode "explicitly" - so cannot find explicit monodromies. Rare exceptions like Knizhnik-Zamolodchikov equation are due some hidden Lie group symmetry inside.
    $endgroup$
    – Alexander Chervov
    3 hours ago










1




1




$begingroup$
You cannot solve ode "explicitly" - so cannot find explicit monodromies. Rare exceptions like Knizhnik-Zamolodchikov equation are due some hidden Lie group symmetry inside.
$endgroup$
– Alexander Chervov
3 hours ago






$begingroup$
You cannot solve ode "explicitly" - so cannot find explicit monodromies. Rare exceptions like Knizhnik-Zamolodchikov equation are due some hidden Lie group symmetry inside.
$endgroup$
– Alexander Chervov
3 hours ago












1 Answer
1






active

oldest

votes


















3












$begingroup$

It depends on what is called "explicit". If $k>2$, monodromy representation is a transcendental function of the $A_j$ and $s_j$. When $d=0$, it was expressed as an everywhere convergent power series in
the $A_j$ whose coefficients are explicit (rational) functions in $s_j$ by Lappo-Danilevski:



Lappo-Danilevsky, J. A. Mémoires sur la théorie des systèmes des équations différentielles linéaires. (French) Chelsea Publishing Co., New York, N. Y., 1953.



If $dneq 0$, the system is not Fuchsian: singularity at $infty$ is irregular. If $k=2, dneq 0$ your system already contains the
"prolate/oblate spheroid equations", which were studied much and no reasonable explicit formula for the monodromy
is known. There are asymptotics, of course. A recent paper about this special case, with a good reference list is



Richard-Jung, F.; Ramis, J.-P.; Thomann, J.; Fauvet, F. New characterizations for the eigenvalues of the prolate spheroidal wave equation. Stud. Appl. Math. 138 (2017), no. 1, 3–42.



The case $d=0$, $k=3$ was also much studied. The papers usually refer to "Heun's equation".






share|cite|improve this answer











$endgroup$









  • 1




    $begingroup$
    In physics they call it 'time ordered exponent' en.m.wikipedia.org/wiki/Ordered_exponential
    $endgroup$
    – Alexander Chervov
    1 hour ago










  • $begingroup$
    @Alexander Chervov: good remark! This gives many references which are more modern than the original papers of Lappo-Danilevsky.
    $endgroup$
    – Alexandre Eremenko
    1 hour ago











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1 Answer
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1 Answer
1






active

oldest

votes









active

oldest

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active

oldest

votes









3












$begingroup$

It depends on what is called "explicit". If $k>2$, monodromy representation is a transcendental function of the $A_j$ and $s_j$. When $d=0$, it was expressed as an everywhere convergent power series in
the $A_j$ whose coefficients are explicit (rational) functions in $s_j$ by Lappo-Danilevski:



Lappo-Danilevsky, J. A. Mémoires sur la théorie des systèmes des équations différentielles linéaires. (French) Chelsea Publishing Co., New York, N. Y., 1953.



If $dneq 0$, the system is not Fuchsian: singularity at $infty$ is irregular. If $k=2, dneq 0$ your system already contains the
"prolate/oblate spheroid equations", which were studied much and no reasonable explicit formula for the monodromy
is known. There are asymptotics, of course. A recent paper about this special case, with a good reference list is



Richard-Jung, F.; Ramis, J.-P.; Thomann, J.; Fauvet, F. New characterizations for the eigenvalues of the prolate spheroidal wave equation. Stud. Appl. Math. 138 (2017), no. 1, 3–42.



The case $d=0$, $k=3$ was also much studied. The papers usually refer to "Heun's equation".






share|cite|improve this answer











$endgroup$









  • 1




    $begingroup$
    In physics they call it 'time ordered exponent' en.m.wikipedia.org/wiki/Ordered_exponential
    $endgroup$
    – Alexander Chervov
    1 hour ago










  • $begingroup$
    @Alexander Chervov: good remark! This gives many references which are more modern than the original papers of Lappo-Danilevsky.
    $endgroup$
    – Alexandre Eremenko
    1 hour ago
















3












$begingroup$

It depends on what is called "explicit". If $k>2$, monodromy representation is a transcendental function of the $A_j$ and $s_j$. When $d=0$, it was expressed as an everywhere convergent power series in
the $A_j$ whose coefficients are explicit (rational) functions in $s_j$ by Lappo-Danilevski:



Lappo-Danilevsky, J. A. Mémoires sur la théorie des systèmes des équations différentielles linéaires. (French) Chelsea Publishing Co., New York, N. Y., 1953.



If $dneq 0$, the system is not Fuchsian: singularity at $infty$ is irregular. If $k=2, dneq 0$ your system already contains the
"prolate/oblate spheroid equations", which were studied much and no reasonable explicit formula for the monodromy
is known. There are asymptotics, of course. A recent paper about this special case, with a good reference list is



Richard-Jung, F.; Ramis, J.-P.; Thomann, J.; Fauvet, F. New characterizations for the eigenvalues of the prolate spheroidal wave equation. Stud. Appl. Math. 138 (2017), no. 1, 3–42.



The case $d=0$, $k=3$ was also much studied. The papers usually refer to "Heun's equation".






share|cite|improve this answer











$endgroup$









  • 1




    $begingroup$
    In physics they call it 'time ordered exponent' en.m.wikipedia.org/wiki/Ordered_exponential
    $endgroup$
    – Alexander Chervov
    1 hour ago










  • $begingroup$
    @Alexander Chervov: good remark! This gives many references which are more modern than the original papers of Lappo-Danilevsky.
    $endgroup$
    – Alexandre Eremenko
    1 hour ago














3












3








3





$begingroup$

It depends on what is called "explicit". If $k>2$, monodromy representation is a transcendental function of the $A_j$ and $s_j$. When $d=0$, it was expressed as an everywhere convergent power series in
the $A_j$ whose coefficients are explicit (rational) functions in $s_j$ by Lappo-Danilevski:



Lappo-Danilevsky, J. A. Mémoires sur la théorie des systèmes des équations différentielles linéaires. (French) Chelsea Publishing Co., New York, N. Y., 1953.



If $dneq 0$, the system is not Fuchsian: singularity at $infty$ is irregular. If $k=2, dneq 0$ your system already contains the
"prolate/oblate spheroid equations", which were studied much and no reasonable explicit formula for the monodromy
is known. There are asymptotics, of course. A recent paper about this special case, with a good reference list is



Richard-Jung, F.; Ramis, J.-P.; Thomann, J.; Fauvet, F. New characterizations for the eigenvalues of the prolate spheroidal wave equation. Stud. Appl. Math. 138 (2017), no. 1, 3–42.



The case $d=0$, $k=3$ was also much studied. The papers usually refer to "Heun's equation".






share|cite|improve this answer











$endgroup$



It depends on what is called "explicit". If $k>2$, monodromy representation is a transcendental function of the $A_j$ and $s_j$. When $d=0$, it was expressed as an everywhere convergent power series in
the $A_j$ whose coefficients are explicit (rational) functions in $s_j$ by Lappo-Danilevski:



Lappo-Danilevsky, J. A. Mémoires sur la théorie des systèmes des équations différentielles linéaires. (French) Chelsea Publishing Co., New York, N. Y., 1953.



If $dneq 0$, the system is not Fuchsian: singularity at $infty$ is irregular. If $k=2, dneq 0$ your system already contains the
"prolate/oblate spheroid equations", which were studied much and no reasonable explicit formula for the monodromy
is known. There are asymptotics, of course. A recent paper about this special case, with a good reference list is



Richard-Jung, F.; Ramis, J.-P.; Thomann, J.; Fauvet, F. New characterizations for the eigenvalues of the prolate spheroidal wave equation. Stud. Appl. Math. 138 (2017), no. 1, 3–42.



The case $d=0$, $k=3$ was also much studied. The papers usually refer to "Heun's equation".







share|cite|improve this answer














share|cite|improve this answer



share|cite|improve this answer








edited 52 mins ago

























answered 1 hour ago









Alexandre EremenkoAlexandre Eremenko

50.5k6139257




50.5k6139257








  • 1




    $begingroup$
    In physics they call it 'time ordered exponent' en.m.wikipedia.org/wiki/Ordered_exponential
    $endgroup$
    – Alexander Chervov
    1 hour ago










  • $begingroup$
    @Alexander Chervov: good remark! This gives many references which are more modern than the original papers of Lappo-Danilevsky.
    $endgroup$
    – Alexandre Eremenko
    1 hour ago














  • 1




    $begingroup$
    In physics they call it 'time ordered exponent' en.m.wikipedia.org/wiki/Ordered_exponential
    $endgroup$
    – Alexander Chervov
    1 hour ago










  • $begingroup$
    @Alexander Chervov: good remark! This gives many references which are more modern than the original papers of Lappo-Danilevsky.
    $endgroup$
    – Alexandre Eremenko
    1 hour ago








1




1




$begingroup$
In physics they call it 'time ordered exponent' en.m.wikipedia.org/wiki/Ordered_exponential
$endgroup$
– Alexander Chervov
1 hour ago




$begingroup$
In physics they call it 'time ordered exponent' en.m.wikipedia.org/wiki/Ordered_exponential
$endgroup$
– Alexander Chervov
1 hour ago












$begingroup$
@Alexander Chervov: good remark! This gives many references which are more modern than the original papers of Lappo-Danilevsky.
$endgroup$
– Alexandre Eremenko
1 hour ago




$begingroup$
@Alexander Chervov: good remark! This gives many references which are more modern than the original papers of Lappo-Danilevsky.
$endgroup$
– Alexandre Eremenko
1 hour ago


















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