<p>We provide criteria for Itô integration to behave continuously with respect to Skorokhod’s <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(J_1\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>J</mi> <mn>1</mn> </msub> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\(M_1\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>M</mi> <mn>1</mn> </msub> </math></EquationSource> </InlineEquation> topologies, when the integrands and integrators converge weakly or in probability. The results are novel in the <InlineEquation ID="IEq7"> <EquationSource Format="TEX">\(M_1\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>M</mi> <mn>1</mn> </msub> </math></EquationSource> </InlineEquation> setting and unify existing theories in the <InlineEquation ID="IEq8"> <EquationSource Format="TEX">\(J_1\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>J</mi> <mn>1</mn> </msub> </math></EquationSource> </InlineEquation> case. Beyond sufficient criteria, we present an example of uniformly convergent martingale integrators for which the continuity breaks down. Moreover, we show that, for families of local martingales, <InlineEquation ID="IEq9"> <EquationSource Format="TEX">\(M_1\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>M</mi> <mn>1</mn> </msub> </math></EquationSource> </InlineEquation> tightness in fact implies <InlineEquation ID="IEq10"> <EquationSource Format="TEX">\(J_1\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>J</mi> <mn>1</mn> </msub> </math></EquationSource> </InlineEquation> tightness under a mild localised uniform integrability condition. Finally, we apply our results to study scaling limits of models of anomalous diffusion driven by continuous-time random walks. This yields new results on weak <InlineEquation ID="IEq11"> <EquationSource Format="TEX">\(M_1\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>M</mi> <mn>1</mn> </msub> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq12"> <EquationSource Format="TEX">\(J_1\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>J</mi> <mn>1</mn> </msub> </math></EquationSource> </InlineEquation> convergence to stochastic integrals against subordinated stable processes. In the case of superdiffusive scaling, an interesting counterexample is obtained.</p>

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Weak convergence of stochastic integrals on Skorokhod space in Skorokhod’s \(J_1\) and \(M_1\) topologies

  • Andreas Søjmark,
  • Fabrice Wunderlich

摘要

We provide criteria for Itô integration to behave continuously with respect to Skorokhod’s \(J_1\) J 1 and \(M_1\) M 1 topologies, when the integrands and integrators converge weakly or in probability. The results are novel in the \(M_1\) M 1 setting and unify existing theories in the \(J_1\) J 1 case. Beyond sufficient criteria, we present an example of uniformly convergent martingale integrators for which the continuity breaks down. Moreover, we show that, for families of local martingales, \(M_1\) M 1 tightness in fact implies \(J_1\) J 1 tightness under a mild localised uniform integrability condition. Finally, we apply our results to study scaling limits of models of anomalous diffusion driven by continuous-time random walks. This yields new results on weak \(M_1\) M 1 and \(J_1\) J 1 convergence to stochastic integrals against subordinated stable processes. In the case of superdiffusive scaling, an interesting counterexample is obtained.