Are simple Lie algebras complete? Announcing the arrival of Valued Associate #679: Cesar Manara Planned maintenance scheduled April 23, 2019 at 00:00UTC (8:00pm US/Eastern)Are there finite-dimensional Lie algebras which are not defined over the integers?Semisimple Lie algebras are perfect.Why, for nilpotent Lie Algebras, is the inclusion to the derivations $x mapsto ad_x$ not surjective?Whitehead's lemma (Lie algebras) for reductive Lie algebras.Solvable Lie algebra with non-characteristic nilradicalMost general definition of Borel and parabolic Lie algebras?Is the theorem of complete reducibility or the abstract Jordan decomposition needed for structure theory of semisimple Lie algebras?Conditions for lie algebras to be semi direct products of lie algebrasIndecomposable Lie algebrasThe opposite of Weyl's theorem on Lie algebras

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Are simple Lie algebras complete?



Announcing the arrival of Valued Associate #679: Cesar Manara
Planned maintenance scheduled April 23, 2019 at 00:00UTC (8:00pm US/Eastern)Are there finite-dimensional Lie algebras which are not defined over the integers?Semisimple Lie algebras are perfect.Why, for nilpotent Lie Algebras, is the inclusion to the derivations $x mapsto ad_x$ not surjective?Whitehead's lemma (Lie algebras) for reductive Lie algebras.Solvable Lie algebra with non-characteristic nilradicalMost general definition of Borel and parabolic Lie algebras?Is the theorem of complete reducibility or the abstract Jordan decomposition needed for structure theory of semisimple Lie algebras?Conditions for lie algebras to be semi direct products of lie algebrasIndecomposable Lie algebrasThe opposite of Weyl's theorem on Lie algebras










1












$begingroup$


Let $mathfrakg$ be a finite dimensional simple Lie algebra over a field of characteristic $p >0$.
Is $mathfrakg$ complete?
If not, under what conditions is $mathfrakg$ complete?



A Lie algebra is complete if its center is zero and all its derivations are inner.










share|cite|improve this question











$endgroup$











  • $begingroup$
    One sufficient condition is that $dim(mathfrakg)<p$, as it ensures that the Killing form is nondegenerate.
    $endgroup$
    – YCor
    Mar 29 at 8:54















1












$begingroup$


Let $mathfrakg$ be a finite dimensional simple Lie algebra over a field of characteristic $p >0$.
Is $mathfrakg$ complete?
If not, under what conditions is $mathfrakg$ complete?



A Lie algebra is complete if its center is zero and all its derivations are inner.










share|cite|improve this question











$endgroup$











  • $begingroup$
    One sufficient condition is that $dim(mathfrakg)<p$, as it ensures that the Killing form is nondegenerate.
    $endgroup$
    – YCor
    Mar 29 at 8:54













1












1








1





$begingroup$


Let $mathfrakg$ be a finite dimensional simple Lie algebra over a field of characteristic $p >0$.
Is $mathfrakg$ complete?
If not, under what conditions is $mathfrakg$ complete?



A Lie algebra is complete if its center is zero and all its derivations are inner.










share|cite|improve this question











$endgroup$




Let $mathfrakg$ be a finite dimensional simple Lie algebra over a field of characteristic $p >0$.
Is $mathfrakg$ complete?
If not, under what conditions is $mathfrakg$ complete?



A Lie algebra is complete if its center is zero and all its derivations are inner.







lie-algebras positive-characteristic






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Mar 27 at 19:00







key

















asked Mar 27 at 15:42









keykey

85




85











  • $begingroup$
    One sufficient condition is that $dim(mathfrakg)<p$, as it ensures that the Killing form is nondegenerate.
    $endgroup$
    – YCor
    Mar 29 at 8:54
















  • $begingroup$
    One sufficient condition is that $dim(mathfrakg)<p$, as it ensures that the Killing form is nondegenerate.
    $endgroup$
    – YCor
    Mar 29 at 8:54















$begingroup$
One sufficient condition is that $dim(mathfrakg)<p$, as it ensures that the Killing form is nondegenerate.
$endgroup$
– YCor
Mar 29 at 8:54




$begingroup$
One sufficient condition is that $dim(mathfrakg)<p$, as it ensures that the Killing form is nondegenerate.
$endgroup$
– YCor
Mar 29 at 8:54










2 Answers
2






active

oldest

votes


















2












$begingroup$

Examples of simple modular Lie algebras in characteristic $p>2$ having outer derivations are, among others, the Block algebras and Frank algebras, see Seligman. Other examples are certain restricted simple modular Lie algebras of Cartan-type, given in the book by Strade and Farnsteiner.



There is a short argument by Zassenhaus, that a Lie algebra with non-degenerate Killing form has only inner derivations, over a field of arbitrary characteristic.






share|cite|improve this answer









$endgroup$












  • $begingroup$
    A short argument of the latter fact (possibly the same) is given in Proposition 4.4 of these lecture notes: normalesup.org/~cornulier/Lie_cours.pdf
    $endgroup$
    – YCor
    Mar 29 at 8:51











  • $begingroup$
    Thank you Dietrich and YCor for your answer and comments. I am trying to figure out how best to proceed. Given the information that I have received (thank you all) I would change my original question. I think that probably means accepting an answer and then trying to formulate a better question. The examples in Dietrich's answer, answers the original question so I will accept it. Although all comments and answers were useful I can't upvote yet.
    $endgroup$
    – key
    Apr 2 at 8:32



















1












$begingroup$

Not necessarily. However, simple Lie algebras with non-degenerate Killing forms are always complete.






share|cite|improve this answer









$endgroup$












  • $begingroup$
    Thank you for your answer. I will check out what the Killing form is for a small dimensional case of a Lie algebra that I'm interested in.
    $endgroup$
    – key
    Mar 27 at 19:03










  • $begingroup$
    @key Which Lie algebra of low dimension are you interested then?
    $endgroup$
    – Dietrich Burde
    Mar 30 at 9:31











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2 Answers
2






active

oldest

votes








2 Answers
2






active

oldest

votes









active

oldest

votes






active

oldest

votes









2












$begingroup$

Examples of simple modular Lie algebras in characteristic $p>2$ having outer derivations are, among others, the Block algebras and Frank algebras, see Seligman. Other examples are certain restricted simple modular Lie algebras of Cartan-type, given in the book by Strade and Farnsteiner.



There is a short argument by Zassenhaus, that a Lie algebra with non-degenerate Killing form has only inner derivations, over a field of arbitrary characteristic.






share|cite|improve this answer









$endgroup$












  • $begingroup$
    A short argument of the latter fact (possibly the same) is given in Proposition 4.4 of these lecture notes: normalesup.org/~cornulier/Lie_cours.pdf
    $endgroup$
    – YCor
    Mar 29 at 8:51











  • $begingroup$
    Thank you Dietrich and YCor for your answer and comments. I am trying to figure out how best to proceed. Given the information that I have received (thank you all) I would change my original question. I think that probably means accepting an answer and then trying to formulate a better question. The examples in Dietrich's answer, answers the original question so I will accept it. Although all comments and answers were useful I can't upvote yet.
    $endgroup$
    – key
    Apr 2 at 8:32
















2












$begingroup$

Examples of simple modular Lie algebras in characteristic $p>2$ having outer derivations are, among others, the Block algebras and Frank algebras, see Seligman. Other examples are certain restricted simple modular Lie algebras of Cartan-type, given in the book by Strade and Farnsteiner.



There is a short argument by Zassenhaus, that a Lie algebra with non-degenerate Killing form has only inner derivations, over a field of arbitrary characteristic.






share|cite|improve this answer









$endgroup$












  • $begingroup$
    A short argument of the latter fact (possibly the same) is given in Proposition 4.4 of these lecture notes: normalesup.org/~cornulier/Lie_cours.pdf
    $endgroup$
    – YCor
    Mar 29 at 8:51











  • $begingroup$
    Thank you Dietrich and YCor for your answer and comments. I am trying to figure out how best to proceed. Given the information that I have received (thank you all) I would change my original question. I think that probably means accepting an answer and then trying to formulate a better question. The examples in Dietrich's answer, answers the original question so I will accept it. Although all comments and answers were useful I can't upvote yet.
    $endgroup$
    – key
    Apr 2 at 8:32














2












2








2





$begingroup$

Examples of simple modular Lie algebras in characteristic $p>2$ having outer derivations are, among others, the Block algebras and Frank algebras, see Seligman. Other examples are certain restricted simple modular Lie algebras of Cartan-type, given in the book by Strade and Farnsteiner.



There is a short argument by Zassenhaus, that a Lie algebra with non-degenerate Killing form has only inner derivations, over a field of arbitrary characteristic.






share|cite|improve this answer









$endgroup$



Examples of simple modular Lie algebras in characteristic $p>2$ having outer derivations are, among others, the Block algebras and Frank algebras, see Seligman. Other examples are certain restricted simple modular Lie algebras of Cartan-type, given in the book by Strade and Farnsteiner.



There is a short argument by Zassenhaus, that a Lie algebra with non-degenerate Killing form has only inner derivations, over a field of arbitrary characteristic.







share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered Mar 27 at 19:37









Dietrich BurdeDietrich Burde

82.3k649107




82.3k649107











  • $begingroup$
    A short argument of the latter fact (possibly the same) is given in Proposition 4.4 of these lecture notes: normalesup.org/~cornulier/Lie_cours.pdf
    $endgroup$
    – YCor
    Mar 29 at 8:51











  • $begingroup$
    Thank you Dietrich and YCor for your answer and comments. I am trying to figure out how best to proceed. Given the information that I have received (thank you all) I would change my original question. I think that probably means accepting an answer and then trying to formulate a better question. The examples in Dietrich's answer, answers the original question so I will accept it. Although all comments and answers were useful I can't upvote yet.
    $endgroup$
    – key
    Apr 2 at 8:32

















  • $begingroup$
    A short argument of the latter fact (possibly the same) is given in Proposition 4.4 of these lecture notes: normalesup.org/~cornulier/Lie_cours.pdf
    $endgroup$
    – YCor
    Mar 29 at 8:51











  • $begingroup$
    Thank you Dietrich and YCor for your answer and comments. I am trying to figure out how best to proceed. Given the information that I have received (thank you all) I would change my original question. I think that probably means accepting an answer and then trying to formulate a better question. The examples in Dietrich's answer, answers the original question so I will accept it. Although all comments and answers were useful I can't upvote yet.
    $endgroup$
    – key
    Apr 2 at 8:32
















$begingroup$
A short argument of the latter fact (possibly the same) is given in Proposition 4.4 of these lecture notes: normalesup.org/~cornulier/Lie_cours.pdf
$endgroup$
– YCor
Mar 29 at 8:51





$begingroup$
A short argument of the latter fact (possibly the same) is given in Proposition 4.4 of these lecture notes: normalesup.org/~cornulier/Lie_cours.pdf
$endgroup$
– YCor
Mar 29 at 8:51













$begingroup$
Thank you Dietrich and YCor for your answer and comments. I am trying to figure out how best to proceed. Given the information that I have received (thank you all) I would change my original question. I think that probably means accepting an answer and then trying to formulate a better question. The examples in Dietrich's answer, answers the original question so I will accept it. Although all comments and answers were useful I can't upvote yet.
$endgroup$
– key
Apr 2 at 8:32





$begingroup$
Thank you Dietrich and YCor for your answer and comments. I am trying to figure out how best to proceed. Given the information that I have received (thank you all) I would change my original question. I think that probably means accepting an answer and then trying to formulate a better question. The examples in Dietrich's answer, answers the original question so I will accept it. Although all comments and answers were useful I can't upvote yet.
$endgroup$
– key
Apr 2 at 8:32












1












$begingroup$

Not necessarily. However, simple Lie algebras with non-degenerate Killing forms are always complete.






share|cite|improve this answer









$endgroup$












  • $begingroup$
    Thank you for your answer. I will check out what the Killing form is for a small dimensional case of a Lie algebra that I'm interested in.
    $endgroup$
    – key
    Mar 27 at 19:03










  • $begingroup$
    @key Which Lie algebra of low dimension are you interested then?
    $endgroup$
    – Dietrich Burde
    Mar 30 at 9:31















1












$begingroup$

Not necessarily. However, simple Lie algebras with non-degenerate Killing forms are always complete.






share|cite|improve this answer









$endgroup$












  • $begingroup$
    Thank you for your answer. I will check out what the Killing form is for a small dimensional case of a Lie algebra that I'm interested in.
    $endgroup$
    – key
    Mar 27 at 19:03










  • $begingroup$
    @key Which Lie algebra of low dimension are you interested then?
    $endgroup$
    – Dietrich Burde
    Mar 30 at 9:31













1












1








1





$begingroup$

Not necessarily. However, simple Lie algebras with non-degenerate Killing forms are always complete.






share|cite|improve this answer









$endgroup$



Not necessarily. However, simple Lie algebras with non-degenerate Killing forms are always complete.







share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered Mar 27 at 15:47









José Carlos SantosJosé Carlos Santos

176k24134243




176k24134243











  • $begingroup$
    Thank you for your answer. I will check out what the Killing form is for a small dimensional case of a Lie algebra that I'm interested in.
    $endgroup$
    – key
    Mar 27 at 19:03










  • $begingroup$
    @key Which Lie algebra of low dimension are you interested then?
    $endgroup$
    – Dietrich Burde
    Mar 30 at 9:31
















  • $begingroup$
    Thank you for your answer. I will check out what the Killing form is for a small dimensional case of a Lie algebra that I'm interested in.
    $endgroup$
    – key
    Mar 27 at 19:03










  • $begingroup$
    @key Which Lie algebra of low dimension are you interested then?
    $endgroup$
    – Dietrich Burde
    Mar 30 at 9:31















$begingroup$
Thank you for your answer. I will check out what the Killing form is for a small dimensional case of a Lie algebra that I'm interested in.
$endgroup$
– key
Mar 27 at 19:03




$begingroup$
Thank you for your answer. I will check out what the Killing form is for a small dimensional case of a Lie algebra that I'm interested in.
$endgroup$
– key
Mar 27 at 19:03












$begingroup$
@key Which Lie algebra of low dimension are you interested then?
$endgroup$
– Dietrich Burde
Mar 30 at 9:31




$begingroup$
@key Which Lie algebra of low dimension are you interested then?
$endgroup$
– Dietrich Burde
Mar 30 at 9:31

















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