{"title":"On linear stochastic flows","authors":"Beniamin Goldys, Szymon Peszat","doi":"10.1090/tran/8782","DOIUrl":null,"url":null,"abstract":"We study the existence of the stochastic flow associated to a linear stochastic evolution equation <disp-formula content-type=\"math/mathml\"> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" alttext=\"normal d upper X equals upper A upper X normal d t plus sigma-summation Underscript k Endscripts upper B Subscript k Baseline upper X normal d upper W Subscript k Baseline comma\"> <mml:semantics> <mml:mrow> <mml:mi mathvariant=\"normal\">d</mml:mi> <mml:mo><!-- --></mml:mo> <mml:mi>X</mml:mi> <mml:mo>=</mml:mo> <mml:mi>A</mml:mi> <mml:mi>X</mml:mi> <mml:mi mathvariant=\"normal\">d</mml:mi> <mml:mo><!-- --></mml:mo> <mml:mi>t</mml:mi> <mml:mo>+</mml:mo> <mml:munder> <mml:mo>∑<!-- ∑ --></mml:mo> <mml:mrow class=\"MJX-TeXAtom-ORD\"> <mml:mi>k</mml:mi> </mml:mrow> </mml:munder> <mml:msub> <mml:mi>B</mml:mi> <mml:mi>k</mml:mi> </mml:msub> <mml:mi>X</mml:mi> <mml:mi mathvariant=\"normal\">d</mml:mi> <mml:mo><!-- --></mml:mo> <mml:msub> <mml:mi>W</mml:mi> <mml:mi>k</mml:mi> </mml:msub> <mml:mo>,</mml:mo> </mml:mrow> <mml:annotation encoding=\"application/x-tex\">\\begin{equation*} \\operatorname {d} X= AX\\operatorname {d} t +\\sum _{k} B_k X\\operatorname {d} W_k, \\end{equation*}</mml:annotation> </mml:semantics> </mml:math> </disp-formula> on a Hilbert space. Our first result covers the case where <inline-formula content-type=\"math/mathml\"> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" alttext=\"upper A\"> <mml:semantics> <mml:mi>A</mml:mi> <mml:annotation encoding=\"application/x-tex\">A</mml:annotation> </mml:semantics> </mml:math> </inline-formula> is the generator of a <inline-formula content-type=\"math/mathml\"> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" alttext=\"upper C 0\"> <mml:semantics> <mml:msub> <mml:mi>C</mml:mi> <mml:mn>0</mml:mn> </mml:msub> <mml:annotation encoding=\"application/x-tex\">C_0</mml:annotation> </mml:semantics> </mml:math> </inline-formula>-semigroup, and <inline-formula content-type=\"math/mathml\"> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" alttext=\"left-parenthesis upper B Subscript k Baseline right-parenthesis\"> <mml:semantics> <mml:mrow> <mml:mo stretchy=\"false\">(</mml:mo> <mml:msub> <mml:mi>B</mml:mi> <mml:mi>k</mml:mi> </mml:msub> <mml:mo stretchy=\"false\">)</mml:mo> </mml:mrow> <mml:annotation encoding=\"application/x-tex\">(B_k)</mml:annotation> </mml:semantics> </mml:math> </inline-formula> is a sequence of bounded linear operators such that <inline-formula content-type=\"math/mathml\"> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" alttext=\"sigma-summation Underscript k Endscripts double-vertical-bar upper B Subscript k Baseline double-vertical-bar greater-than plus normal infinity\"> <mml:semantics> <mml:mrow> <mml:munder> <mml:mo>∑<!-- ∑ --></mml:mo> <mml:mi>k</mml:mi> </mml:munder> <mml:mo fence=\"false\" stretchy=\"false\">‖<!-- ‖ --></mml:mo> <mml:msub> <mml:mi>B</mml:mi> <mml:mi>k</mml:mi> </mml:msub> <mml:mo fence=\"false\" stretchy=\"false\">‖<!-- ‖ --></mml:mo> <mml:mo>></mml:mo> <mml:mo>+</mml:mo> <mml:mi mathvariant=\"normal\">∞<!-- ∞ --></mml:mi> </mml:mrow> <mml:annotation encoding=\"application/x-tex\">\\sum _k\\|B_k\\|>+\\infty</mml:annotation> </mml:semantics> </mml:math> </inline-formula>. We also provide sufficient conditions for the existence of stochastic flows in the Schatten classes beyond the space of Hilbert–Schmidt operators. Some new results and examples concerning the so-called commutative case are presented as well.","PeriodicalId":23209,"journal":{"name":"Transactions of the American Mathematical Society","volume":null,"pages":null},"PeriodicalIF":1.2000,"publicationDate":"2023-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Transactions of the American Mathematical Society","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.1090/tran/8782","RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"MATHEMATICS","Score":null,"Total":0}
引用次数: 0
Abstract
We study the existence of the stochastic flow associated to a linear stochastic evolution equation dX=AXdt+∑kBkXdWk,\begin{equation*} \operatorname {d} X= AX\operatorname {d} t +\sum _{k} B_k X\operatorname {d} W_k, \end{equation*} on a Hilbert space. Our first result covers the case where AA is the generator of a C0C_0-semigroup, and (Bk)(B_k) is a sequence of bounded linear operators such that ∑k‖Bk‖>+∞\sum _k\|B_k\|>+\infty. We also provide sufficient conditions for the existence of stochastic flows in the Schatten classes beyond the space of Hilbert–Schmidt operators. Some new results and examples concerning the so-called commutative case are presented as well.
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