{"id":{"repo_id":"mit","oai_identifier":"oai:dspace.mit.edu:1721.1/112909"},"canonical_url":"https://search.dev.ndltd.org/etd/mit/oai:dspace.mit.edu:1721.1/112909","repository":{"repo_id":"mit","name":"MIT","base_url":"https://dspace.mit.edu/oai/request"},"display":{"title":"Rational matrix differential operators and integrable systems of PDEs","abstract":"A key feature of integrability for systems of evolution PDEs ut = F(u), where F lies in a differential algebra of functionals V and u = (U1, ... , ul) depends on one space variable x and time t, is to be part of an infinite hierarchy of generalized symmetries. Recall that V carries a Lie algebra bracket {F, G} = XF(G) - XG(F), where XF denotes the evolutionnary vector field attached to F. In all known examples, these hierarchies are constructed by means of Lenard-Magri sequences: one can find a pair of matrix differential operators (A(a), B(a)) and a sequence (G.n)>n>0,[epsilon] Vl such that ** F = B(GN) for some N >/= 0, ** {B(Gn), B(Gm)} = 0 for all n, m >/= 0, ** B(G,+1 ) = A(G) for all n,m >/= 0. We show that in the scalar case l = 1 a necessary condition for a pair of differential operators (A, B) to generate a Lenard-Magri sequence is that for all constants [lambda], the family C[lambda] = A + [lambda]B must satisfy for all F, G [epsilon]V {C[lambda](F), C[lambda](G)} [epsilon] ImC[lambda]. We call such pairs integrable. We give a sufficient condition on an integrable pair of matrix differential operators (A, B) to generate an infinite Lenard- Magri sequence when the rational matrix differential operator L = AB-1 is weakly non-local and the algebra of differential functions V is either Z or Z/2Z-graded. This is applied to many systems of evolution PDEs to prove their integrability.","abstract_html":"A key feature of integrability for systems of evolution PDEs ut = F(u), where F lies in a differential algebra of functionals V and u = (U1, ... , ul) depends on one space variable x and time t, is to be part of an infinite hierarchy of generalized symmetries. Recall that V carries a Lie algebra bracket {F, G} = XF(G) - XG(F), where XF denotes the evolutionnary vector field attached to F. In all known examples, these hierarchies are constructed by means of Lenard-Magri sequences: one can find a pair of matrix differential operators (A(a), B(a)) and a sequence (G.n)>n>0,[epsilon] Vl such that ** F = B(GN) for some N >/= 0, ** {B(Gn), B(Gm)} = 0 for all n, m >/= 0, ** B(G,+1 ) = A(G) for all n,m >/= 0. We show that in the scalar case l = 1 a necessary condition for a pair of differential operators (A, B) to generate a Lenard-Magri sequence is that for all constants [lambda], the family C[lambda] = A + [lambda]B must satisfy for all F, G [epsilon]V {C[lambda](F), C[lambda](G)} [epsilon] ImC[lambda]. We call such pairs integrable. We give a sufficient condition on an integrable pair of matrix differential operators (A, B) to generate an infinite Lenard- Magri sequence when the rational matrix differential operator L = AB-1 is weakly non-local and the algebra of differential functions V is either Z or Z/2Z-graded. This is applied to many systems of evolution PDEs to prove their integrability.","abstract_has_math":false,"creators":["Carpentier, Sylvain,Ph. D.Massachusetts Institute of Technology."],"institution":"Massachusetts Institute of Technology","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":"Massachusetts Institute of Technology. Department of Mathematics","school":null,"contributors":[],"advisors":["Victor G. Kac."],"committee_chairs":[],"committee_members":[],"year":2017,"date_issued":"2017","date_published":"2017","updated_at":"2026-07-22T22:21:20Z","subjects":["Mathematics."],"languages":["eng"],"rights":["MIT theses are protected by copyright. They may be viewed, downloaded, or printed from this source but further reproduction or distribution in any format is prohibited without written permission."],"rights_urls":["http://dspace.mit.edu/handle/1721.1/7582"],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/1721.1/112909","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Victor G. Kac."]},{"key":"dc:contributor.department","label":"Department","values":["Massachusetts Institute of Technology. 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They may be viewed, downloaded, or printed from this source but further reproduction or distribution in any format is prohibited without written permission."]},{"key":"dc:rights.uri","label":"Rights URI","values":["http://dspace.mit.edu/handle/1721.1/7582"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://hdl.handle.net/1721.1/112909"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mathematics, 2017","Cataloged from PDF version of thesis.","Includes bibliographical references (pages 129-133)."]},{"key":"dc:description.abstract","label":"Abstract","values":["A key feature of integrability for systems of evolution PDEs ut = F(u), where F lies in a differential algebra of functionals V and u = (U1, ... , ul) depends on one space variable x and time t, is to be part of an infinite hierarchy of generalized symmetries. Recall that V carries a Lie algebra bracket {F, G} = XF(G) - XG(F), where XF denotes the evolutionnary vector field attached to F. In all known examples, these hierarchies are constructed by means of Lenard-Magri sequences: one can find a pair of matrix differential operators (A(a), B(a)) and a sequence (G.n)>n>0,[epsilon] Vl such that ** F = B(GN) for some N >/= 0, ** {B(Gn), B(Gm)} = 0 for all n, m >/= 0, ** B(G,+1 ) = A(G) for all n,m >/= 0. We show that in the scalar case l = 1 a necessary condition for a pair of differential operators (A, B) to generate a Lenard-Magri sequence is that for all constants [lambda], the family C[lambda] = A + [lambda]B must satisfy for all F, G [epsilon]V {C[lambda](F), C[lambda](G)} [epsilon] ImC[lambda]. We call such pairs integrable. We give a sufficient condition on an integrable pair of matrix differential operators (A, B) to generate an infinite Lenard- Magri sequence when the rational matrix differential operator L = AB-1 is weakly non-local and the algebra of differential functions V is either Z or Z/2Z-graded. This is applied to many systems of evolution PDEs to prove their integrability."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Ph. D."]},{"key":"dc:title","label":"Title","values":["Rational matrix differential operators and integrable systems of PDEs"]}]}],"canonical_facts":{"dc:contributor.advisor":["Victor G. Kac."],"dc:contributor.department":["Massachusetts Institute of Technology. Department of Mathematics"],"dc:contributor.other":["Massachusetts Institute of Technology. Department of Mathematics."],"dc:creator":["Carpentier, Sylvain,Ph. D.Massachusetts Institute of Technology."],"dc:date.accessioned":["2017-12-20T18:16:56Z"],"dc:date.available":["2017-12-20T18:16:56Z"],"dc:date.issued":["2017"],"dc:description":["Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mathematics, 2017","Cataloged from PDF version of thesis.","Includes bibliographical references (pages 129-133)."],"dc:description.abstract":["A key feature of integrability for systems of evolution PDEs ut = F(u), where F lies in a differential algebra of functionals V and u = (U1, ... , ul) depends on one space variable x and time t, is to be part of an infinite hierarchy of generalized symmetries. Recall that V carries a Lie algebra bracket {F, G} = XF(G) - XG(F), where XF denotes the evolutionnary vector field attached to F. In all known examples, these hierarchies are constructed by means of Lenard-Magri sequences: one can find a pair of matrix differential operators (A(a), B(a)) and a sequence (G.n)>n>0,[epsilon] Vl such that ** F = B(GN) for some N >/= 0, ** {B(Gn), B(Gm)} = 0 for all n, m >/= 0, ** B(G,+1 ) = A(G) for all n,m >/= 0. We show that in the scalar case l = 1 a necessary condition for a pair of differential operators (A, B) to generate a Lenard-Magri sequence is that for all constants [lambda], the family C[lambda] = A + [lambda]B must satisfy for all F, G [epsilon]V {C[lambda](F), C[lambda](G)} [epsilon] ImC[lambda]. We call such pairs integrable. We give a sufficient condition on an integrable pair of matrix differential operators (A, B) to generate an infinite Lenard- Magri sequence when the rational matrix differential operator L = AB-1 is weakly non-local and the algebra of differential functions V is either Z or Z/2Z-graded. This is applied to many systems of evolution PDEs to prove their integrability."],"dc:description.degree":["Ph. D."],"dc:identifier.uri":["http://hdl.handle.net/1721.1/112909"],"dc:language.iso":["eng"],"dc:publisher":["Massachusetts Institute of Technology"],"dc:rights":["MIT theses are protected by copyright. They may be viewed, downloaded, or printed from this source but further reproduction or distribution in any format is prohibited without written permission."],"dc:rights.uri":["http://dspace.mit.edu/handle/1721.1/7582"],"dc:subject":["Mathematics."],"dc:title":["Rational matrix differential operators and integrable systems of PDEs"],"dc:type":["Thesis"]},"updated_at":"2026-07-22T22:21:20Z"}