Pub Date : 2025-11-03DOI: 10.1016/j.jfa.2025.111249
Leo Brauner , Georg C. Hofstätter , Oscar Ortega-Moreno
We show an analogue of the Klain–Schneider theorem for valuations that are invariant under rotations around a fixed axis, called zonal. Using this, we establish a new integral representation of zonal valuations involving mixed area measures with a disk. In our argument, we introduce an easy way to translate between this representation and the one involving area measures, yielding a shorter proof of a recent characterization by Knoerr.
As applications, we obtain various integral geometric formulas for : an additive kinematic, a Kubota-, and a Crofton-type formula. This extends results by Hug, Mussnig, and Ulivelli. Finally, we provide a simpler proof of the integral representation of the mean section operators by Goodey and Weil.
{"title":"The Klain approach to zonal valuations","authors":"Leo Brauner , Georg C. Hofstätter , Oscar Ortega-Moreno","doi":"10.1016/j.jfa.2025.111249","DOIUrl":"10.1016/j.jfa.2025.111249","url":null,"abstract":"<div><div>We show an analogue of the Klain–Schneider theorem for valuations that are invariant under rotations around a fixed axis, called zonal. Using this, we establish a new integral representation of zonal valuations involving mixed area measures with a disk. In our argument, we introduce an easy way to translate between this representation and the one involving area measures, yielding a shorter proof of a recent characterization by Knoerr.</div><div>As applications, we obtain various integral geometric formulas for <span><math><mrow><mi>SO</mi></mrow><mo>(</mo><mi>n</mi><mo>−</mo><mn>1</mn><mo>)</mo></math></span>: an additive kinematic, a Kubota-, and a Crofton-type formula. This extends results by Hug, Mussnig, and Ulivelli. Finally, we provide a simpler proof of the integral representation of the mean section operators by Goodey and Weil.</div></div>","PeriodicalId":15750,"journal":{"name":"Journal of Functional Analysis","volume":"290 3","pages":"Article 111249"},"PeriodicalIF":1.6,"publicationDate":"2025-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145474827","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-13DOI: 10.1016/j.jfa.2025.111231
André Pedroso Kowacs, Alexandre Kirilov
This paper provides a complete characterization of global hypoellipticity and solvability with loss of derivatives for Fourier multiplier operators on the n-dimensional torus. We establish necessary and sufficient conditions for these properties and examine their connections with classical notions of global hypoellipticity and solvability, particularly in relation to the closedness of the operator's range.
As an application, we explore the interplay between these properties and number theory in the context of differential operators on the two-torus. Specifically, we prove that the loss of derivatives in the solvability of the vector field is precisely determined by the well-known irrationality measure of its coefficient α. Furthermore, we analyze the wave operator and show how the loss of derivatives depends explicitly on the parameter .
{"title":"Global hypoellipticity and solvability with loss of derivatives on the torus","authors":"André Pedroso Kowacs, Alexandre Kirilov","doi":"10.1016/j.jfa.2025.111231","DOIUrl":"10.1016/j.jfa.2025.111231","url":null,"abstract":"<div><div>This paper provides a complete characterization of global hypoellipticity and solvability with loss of derivatives for Fourier multiplier operators on the <em>n</em>-dimensional torus. We establish necessary and sufficient conditions for these properties and examine their connections with classical notions of global hypoellipticity and solvability, particularly in relation to the closedness of the operator's range.</div><div>As an application, we explore the interplay between these properties and number theory in the context of differential operators on the two-torus. Specifically, we prove that the loss of derivatives in the solvability of the vector field <span><math><msub><mrow><mo>∂</mo></mrow><mrow><msub><mrow><mi>x</mi></mrow><mrow><mn>1</mn></mrow></msub></mrow></msub><mo>−</mo><mi>α</mi><msub><mrow><mo>∂</mo></mrow><mrow><msub><mrow><mi>x</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></msub></math></span> is precisely determined by the well-known irrationality measure <span><math><mi>μ</mi><mo>(</mo><mi>α</mi><mo>)</mo></math></span> of its coefficient <em>α</em>. Furthermore, we analyze the wave operator <span><math><msubsup><mrow><mo>∂</mo></mrow><mrow><msub><mrow><mi>x</mi></mrow><mrow><mn>1</mn></mrow></msub></mrow><mrow><mn>2</mn></mrow></msubsup><mo>−</mo><msup><mrow><mi>η</mi></mrow><mrow><mn>2</mn></mrow></msup><msub><mrow><mi>Δ</mi></mrow><mrow><msup><mrow><mi>T</mi></mrow><mrow><mi>n</mi></mrow></msup></mrow></msub></math></span> and show how the loss of derivatives depends explicitly on the parameter <span><math><mi>η</mi><mo>></mo><mn>0</mn></math></span>.</div></div>","PeriodicalId":15750,"journal":{"name":"Journal of Functional Analysis","volume":"290 2","pages":"Article 111231"},"PeriodicalIF":1.6,"publicationDate":"2025-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145325845","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-10DOI: 10.1016/j.jfa.2025.111237
Hidetaka Hamada , Gabriela Kohr , Mirela Kohr
In the first part of this paper, we obtain a covering theorem for biholomorphic mappings on bounded domains in a complex Banach space. Next, as an application of this covering theorem, we obtain the Koebe one-quarter theorem for normal Loewner chains on the unit ball of a complex Banach space. We give also several applications of this result. Finally, as another application of the covering theorem obtained in this paper, we obtain a covering theorem for nonlinear resolvents on the unit ball of a complex Banach space.
{"title":"Koebe one-quarter theorem in infinite dimensions","authors":"Hidetaka Hamada , Gabriela Kohr , Mirela Kohr","doi":"10.1016/j.jfa.2025.111237","DOIUrl":"10.1016/j.jfa.2025.111237","url":null,"abstract":"<div><div>In the first part of this paper, we obtain a covering theorem for biholomorphic mappings on bounded domains in a complex Banach space. Next, as an application of this covering theorem, we obtain the Koebe one-quarter theorem for normal Loewner chains on the unit ball of a complex Banach space. We give also several applications of this result. Finally, as another application of the covering theorem obtained in this paper, we obtain a covering theorem for nonlinear resolvents on the unit ball of a complex Banach space.</div></div>","PeriodicalId":15750,"journal":{"name":"Journal of Functional Analysis","volume":"290 2","pages":"Article 111237"},"PeriodicalIF":1.6,"publicationDate":"2025-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145363692","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-10DOI: 10.1016/j.jfa.2025.111233
Zhijie Fan , Michael Lacey , Ji Li , Xiao Xiong
Let be the Bessel operator on the upper half space with and , and be the j-th Bessel Riesz transform, . We demonstrate that the Schatten–Lorentz norm (, , ) of the commutator can be characterized in terms of the oscillation space norm of the symbol b. In particular, for the case , the Schatten norm of can be further characterized in terms of the Besov norm of the symbol. Moreover, the critical index is also studied, which is , the lower dimension of the Bessel measure (but not the upper dimension). Our approach relies on martingale and dyadic analysis, which enables us to bypass the use of Fourier analysis effectively.
{"title":"Schatten–Lorentz characterization of Riesz transform commutator associated with Bessel operators","authors":"Zhijie Fan , Michael Lacey , Ji Li , Xiao Xiong","doi":"10.1016/j.jfa.2025.111233","DOIUrl":"10.1016/j.jfa.2025.111233","url":null,"abstract":"<div><div>Let <span><math><msub><mrow><mi>Δ</mi></mrow><mrow><mi>λ</mi></mrow></msub></math></span> be the Bessel operator on the upper half space <span><math><msubsup><mrow><mi>R</mi></mrow><mrow><mo>+</mo></mrow><mrow><mi>n</mi><mo>+</mo><mn>1</mn></mrow></msubsup></math></span> with <span><math><mi>n</mi><mo>≥</mo><mn>0</mn></math></span> and <span><math><mi>λ</mi><mo>></mo><mn>0</mn></math></span>, and <span><math><msub><mrow><mi>R</mi></mrow><mrow><mi>λ</mi><mo>,</mo><mi>j</mi></mrow></msub></math></span> be the <em>j</em>-th Bessel Riesz transform, <span><math><mi>j</mi><mo>=</mo><mn>1</mn><mo>,</mo><mo>…</mo><mo>,</mo><mi>n</mi><mo>+</mo><mn>1</mn></math></span>. We demonstrate that the Schatten–Lorentz norm (<span><math><msup><mrow><mi>S</mi></mrow><mrow><mi>p</mi><mo>,</mo><mi>q</mi></mrow></msup></math></span>, <span><math><mn>1</mn><mo><</mo><mi>p</mi><mo><</mo><mo>∞</mo></math></span>, <span><math><mn>1</mn><mo>≤</mo><mi>q</mi><mo>≤</mo><mo>∞</mo></math></span>) of the commutator <span><math><mo>[</mo><mi>b</mi><mo>,</mo><msub><mrow><mi>R</mi></mrow><mrow><mi>λ</mi><mo>,</mo><mi>j</mi></mrow></msub><mo>]</mo></math></span> can be characterized in terms of the oscillation space norm of the symbol <em>b</em>. In particular, for the case <span><math><mi>p</mi><mo>=</mo><mi>q</mi></math></span>, the Schatten norm of <span><math><mo>[</mo><mi>b</mi><mo>,</mo><msub><mrow><mi>R</mi></mrow><mrow><mi>λ</mi><mo>,</mo><mi>j</mi></mrow></msub><mo>]</mo></math></span> can be further characterized in terms of the Besov norm of the symbol. Moreover, the critical index is also studied, which is <span><math><mi>p</mi><mo>=</mo><mi>n</mi><mo>+</mo><mn>1</mn></math></span>, the lower dimension of the Bessel measure (but not the upper dimension). Our approach relies on martingale and dyadic analysis, which enables us to bypass the use of Fourier analysis effectively.</div></div>","PeriodicalId":15750,"journal":{"name":"Journal of Functional Analysis","volume":"290 2","pages":"Article 111233"},"PeriodicalIF":1.6,"publicationDate":"2025-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145325847","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-10DOI: 10.1016/j.jfa.2025.111235
Shahaboddin Shaabani
For a symmetric convex body and , we define the space to be the tent generalization of , i.e., the space of all continuous functions f on the upper-half space such that where, in the above, the supremum is taken over all finite disjoint collections of homothetic copies of K. It is then shown that the dual of , the closure of the space of continuous functions with compact support in , consists of all Radon measures on with uniformly bounded total variation on cones with base K and vertex in . In addition, a similar scale of spaces is defined in the dyadic setting, and for , a complete characterization of their duals is given. We apply our results to study dyadic spaces.
{"title":"A view from above on JNp(Rn)","authors":"Shahaboddin Shaabani","doi":"10.1016/j.jfa.2025.111235","DOIUrl":"10.1016/j.jfa.2025.111235","url":null,"abstract":"<div><div>For a symmetric convex body <span><math><mi>K</mi><mo>⊂</mo><msup><mrow><mi>R</mi></mrow><mrow><mi>n</mi></mrow></msup></math></span> and <span><math><mn>1</mn><mo>≤</mo><mi>p</mi><mo><</mo><mo>∞</mo></math></span>, we define the space <span><math><msup><mrow><mi>S</mi></mrow><mrow><mi>p</mi></mrow></msup><mo>(</mo><mi>K</mi><mo>)</mo></math></span> to be the tent generalization of <span><math><msub><mrow><mtext>JN</mtext></mrow><mrow><mi>p</mi></mrow></msub><mo>(</mo><msup><mrow><mi>R</mi></mrow><mrow><mi>n</mi></mrow></msup><mo>)</mo></math></span>, i.e., the space of all continuous functions <em>f</em> on the upper-half space <span><math><msubsup><mrow><mi>R</mi></mrow><mrow><mo>+</mo></mrow><mrow><mi>n</mi><mo>+</mo><mn>1</mn></mrow></msubsup></math></span> such that<span><span><span><math><msub><mrow><mo>‖</mo><mi>f</mi><mo>‖</mo></mrow><mrow><msup><mrow><mi>S</mi></mrow><mrow><mi>p</mi></mrow></msup><mo>(</mo><mi>K</mi><mo>)</mo></mrow></msub><mo>:</mo><mo>=</mo><msup><mrow><mo>(</mo><munder><mi>sup</mi><mrow><mi>C</mi></mrow></munder><mo></mo><munder><mo>∑</mo><mrow><mi>B</mi><mo>∈</mo><mi>C</mi></mrow></munder><mo>|</mo><msub><mrow><mi>f</mi></mrow><mrow><mi>B</mi></mrow></msub><msup><mrow><mo>|</mo></mrow><mrow><mi>p</mi></mrow></msup><mo>)</mo></mrow><mrow><mfrac><mrow><mn>1</mn></mrow><mrow><mi>p</mi></mrow></mfrac></mrow></msup><mo><</mo><mo>∞</mo><mo>,</mo></math></span></span></span> where, in the above, the supremum is taken over all finite disjoint collections of homothetic copies of <em>K</em>. It is then shown that the dual of <span><math><msubsup><mrow><mi>S</mi></mrow><mrow><mn>0</mn></mrow><mrow><mn>1</mn></mrow></msubsup><mo>(</mo><mi>K</mi><mo>)</mo></math></span>, the closure of the space of continuous functions with compact support in <span><math><msup><mrow><mi>S</mi></mrow><mrow><mn>1</mn></mrow></msup><mo>(</mo><mi>K</mi><mo>)</mo></math></span>, consists of all Radon measures on <span><math><msubsup><mrow><mi>R</mi></mrow><mrow><mo>+</mo></mrow><mrow><mi>n</mi><mo>+</mo><mn>1</mn></mrow></msubsup></math></span> with uniformly bounded total variation on cones with base <em>K</em> and vertex in <span><math><msup><mrow><mi>R</mi></mrow><mrow><mi>n</mi></mrow></msup></math></span>. In addition, a similar scale of spaces is defined in the dyadic setting, and for <span><math><mn>1</mn><mo>≤</mo><mi>p</mi><mo><</mo><mo>∞</mo></math></span>, a complete characterization of their duals is given. We apply our results to study dyadic <span><math><msub><mrow><mtext>JN</mtext></mrow><mrow><mi>p</mi></mrow></msub></math></span> spaces.</div></div>","PeriodicalId":15750,"journal":{"name":"Journal of Functional Analysis","volume":"290 3","pages":"Article 111235"},"PeriodicalIF":1.6,"publicationDate":"2025-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145290177","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-10DOI: 10.1016/j.jfa.2025.111236
Grzegorz Plebanek , Jakub Rondoš , Damian Sobota
We prove that, for every compact spaces and compact group G, if both and map continuously onto G, then the Banach space contains a complemented subspace isometric to the Banach space . Consequently, contains a complemented copy of for every non-scattered . Also, answering a question of Alspach and Galego, we get that contains a complemented copy of for every cardinal number and hence a complemented copy of for every metric compact space K. On the other hand, for the pointwise topology, we show that contains no complemented copy of .
{"title":"Complemented subspaces of Banach spaces C(K×L)","authors":"Grzegorz Plebanek , Jakub Rondoš , Damian Sobota","doi":"10.1016/j.jfa.2025.111236","DOIUrl":"10.1016/j.jfa.2025.111236","url":null,"abstract":"<div><div>We prove that, for every compact spaces <span><math><msub><mrow><mi>K</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>,</mo><msub><mrow><mi>K</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span> and compact group <em>G</em>, if both <span><math><msub><mrow><mi>K</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span> and <span><math><msub><mrow><mi>K</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span> map continuously onto <em>G</em>, then the Banach space <span><math><mi>C</mi><mo>(</mo><msub><mrow><mi>K</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>×</mo><msub><mrow><mi>K</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>)</mo></math></span> contains a complemented subspace isometric to the Banach space <span><math><mi>C</mi><mo>(</mo><mi>G</mi><mo>)</mo></math></span>. Consequently, <span><math><mi>C</mi><mo>(</mo><msub><mrow><mi>K</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>×</mo><msub><mrow><mi>K</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>)</mo></math></span> contains a complemented copy of <span><math><mi>C</mi><mo>(</mo><mo>[</mo><mn>0</mn><mo>,</mo><mn>1</mn><mo>]</mo><mo>)</mo></math></span> for every non-scattered <span><math><msub><mrow><mi>K</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>,</mo><msub><mrow><mi>K</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>. Also, answering a question of Alspach and Galego, we get that <span><math><mi>C</mi><mo>(</mo><mi>β</mi><mi>ω</mi><mo>×</mo><mi>β</mi><mi>ω</mi><mo>)</mo></math></span> contains a complemented copy of <span><math><mi>C</mi><mo>(</mo><msup><mrow><mo>[</mo><mn>0</mn><mo>,</mo><mn>1</mn><mo>]</mo></mrow><mrow><mi>κ</mi></mrow></msup><mo>)</mo></math></span> for every cardinal number <span><math><mn>1</mn><mo>≤</mo><mi>κ</mi><mo>≤</mo><mi>c</mi></math></span> and hence a complemented copy of <span><math><mi>C</mi><mo>(</mo><mi>K</mi><mo>)</mo></math></span> for every metric compact space <em>K</em>. On the other hand, for the pointwise topology, we show that <span><math><msub><mrow><mi>C</mi></mrow><mrow><mi>p</mi></mrow></msub><mo>(</mo><mi>β</mi><mi>ω</mi><mo>×</mo><mi>β</mi><mi>ω</mi><mo>)</mo></math></span> contains no complemented copy of <span><math><msub><mrow><mi>C</mi></mrow><mrow><mi>p</mi></mrow></msub><mo>(</mo><msup><mrow><mn>2</mn></mrow><mrow><mi>ω</mi></mrow></msup><mo>)</mo></math></span>.</div></div>","PeriodicalId":15750,"journal":{"name":"Journal of Functional Analysis","volume":"290 2","pages":"Article 111236"},"PeriodicalIF":1.6,"publicationDate":"2025-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145325848","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-10DOI: 10.1016/j.jfa.2025.111240
Songbo Wang
We study a system of N diffusive particles with mean field interaction and establish local propagation of chaos estimates as , measured in relative entropy and in weighted distance. These results extend the work of Lacker (2023) [20] to singular interactions. The entropy bound follows from a hierarchy of relative entropies and Fisher informations, and applies to the 2D viscous vortex model in the weak interaction regime, yielding a uniform-in-time estimate. The bound is obtained through a hierarchy of divergences and Dirichlet energies, leading to sharp short-time estimates for the same model without constraints on the interaction strength.
{"title":"Sharp local propagation of chaos for mean field particles with W−1,∞ kernels","authors":"Songbo Wang","doi":"10.1016/j.jfa.2025.111240","DOIUrl":"10.1016/j.jfa.2025.111240","url":null,"abstract":"<div><div>We study a system of <em>N</em> diffusive particles with <span><math><msup><mrow><mi>W</mi></mrow><mrow><mo>−</mo><mn>1</mn><mo>,</mo><mo>∞</mo></mrow></msup></math></span> mean field interaction and establish <span><math><mi>O</mi><mo>(</mo><mn>1</mn><mo>/</mo><msup><mrow><mi>N</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>)</mo></math></span> local propagation of chaos estimates as <span><math><mi>N</mi><mo>→</mo><mo>∞</mo></math></span>, measured in relative entropy and in weighted <span><math><msup><mrow><mi>L</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span> distance. These results extend the work of Lacker (2023) <span><span>[20]</span></span> to singular interactions. The entropy bound follows from a hierarchy of relative entropies and Fisher informations, and applies to the 2D viscous vortex model in the weak interaction regime, yielding a uniform-in-time estimate. The <span><math><msup><mrow><mi>L</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span> bound is obtained through a hierarchy of <span><math><msup><mrow><mi>χ</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span> divergences and Dirichlet energies, leading to sharp short-time estimates for the same model without constraints on the interaction strength.</div></div>","PeriodicalId":15750,"journal":{"name":"Journal of Functional Analysis","volume":"290 3","pages":"Article 111240"},"PeriodicalIF":1.6,"publicationDate":"2025-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145323193","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-10DOI: 10.1016/j.jfa.2025.111227
Víctor Navarro-Fernández , Christian Seis
We study a passive scalar equation on the two-dimensional torus, where the advecting velocity field is given by a cellular flow with a randomly moving centre. We prove that the passive scalar undergoes mixing at a deterministic exponential rate, independent of any underlying diffusivity. Furthermore, we show that the velocity field enhances dissipation and we establish sharp decay rates that, for large times, are deterministic and remain uniform in the diffusivity constant. Our approach is purely Eulerian and relies on a suitable modification of Villani's hypocoercivity method, which incorporates a larger set of Hörmander commutators than Villani's original method.
{"title":"Exponential mixing by random cellular flows","authors":"Víctor Navarro-Fernández , Christian Seis","doi":"10.1016/j.jfa.2025.111227","DOIUrl":"10.1016/j.jfa.2025.111227","url":null,"abstract":"<div><div>We study a passive scalar equation on the two-dimensional torus, where the advecting velocity field is given by a cellular flow with a randomly moving centre. We prove that the passive scalar undergoes mixing at a deterministic exponential rate, independent of any underlying diffusivity. Furthermore, we show that the velocity field enhances dissipation and we establish sharp decay rates that, for large times, are deterministic and remain uniform in the diffusivity constant. Our approach is purely Eulerian and relies on a suitable modification of Villani's hypocoercivity method, which incorporates a larger set of Hörmander commutators than Villani's original method.</div></div>","PeriodicalId":15750,"journal":{"name":"Journal of Functional Analysis","volume":"290 2","pages":"Article 111227"},"PeriodicalIF":1.6,"publicationDate":"2025-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145325846","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-10DOI: 10.1016/j.jfa.2025.111234
Alessandro Bondi , Franco Flandoli
We consider a Volterra convolution equation in perturbed with an additive fractional Brownian motion of Riemann–Liouville type with Hurst parameter . We show that its solution solves an infinite–dimensional stochastic differential equation (SDE) in the Hilbert space of square–integrable functions. Such an equation motivates our study of an unconventional class of SDEs requiring an original extension of the drift operator and its Fréchet differentials. We prove that these infinite–dimensional SDEs generate a Markov stochastic flow which is twice Fréchet differentiable with respect to the initial data. This stochastic flow is then employed to solve, in the classical sense of infinite–dimensional calculus, the path–dependent Kolmogorov equation corresponding to the SDEs. In particular, we associate a time–dependent infinitesimal generator with the fractional Brownian motion. In the final section, we show some obstructions in the analysis of the mild formulation of the Kolmogorov equation for SDEs driven by the same infinite–dimensional noise. This problem, which is relevant to the theory of regularization by noise, remains open for future research.
{"title":"On the Kolmogorov equation associated with Volterra equations and fractional Brownian motion","authors":"Alessandro Bondi , Franco Flandoli","doi":"10.1016/j.jfa.2025.111234","DOIUrl":"10.1016/j.jfa.2025.111234","url":null,"abstract":"<div><div>We consider a Volterra convolution equation in <span><math><msup><mrow><mi>R</mi></mrow><mrow><mi>d</mi></mrow></msup></math></span> perturbed with an additive fractional Brownian motion of Riemann–Liouville type with Hurst parameter <span><math><mi>H</mi><mo>∈</mo><mo>(</mo><mn>0</mn><mo>,</mo><mn>1</mn><mo>)</mo></math></span>. We show that its solution solves an infinite–dimensional stochastic differential equation (SDE) in the Hilbert space of square–integrable functions. Such an equation motivates our study of an unconventional class of SDEs requiring an original extension of the drift operator and its Fréchet differentials. We prove that these infinite–dimensional SDEs generate a Markov stochastic flow which is twice Fréchet differentiable with respect to the initial data. This stochastic flow is then employed to solve, in the classical sense of infinite–dimensional calculus, the path–dependent Kolmogorov equation corresponding to the SDEs. In particular, we associate a time–dependent infinitesimal generator with the fractional Brownian motion. In the final section, we show some obstructions in the analysis of the mild formulation of the Kolmogorov equation for SDEs driven by the same infinite–dimensional noise. This problem, which is relevant to the theory of regularization by noise, remains open for future research.</div></div>","PeriodicalId":15750,"journal":{"name":"Journal of Functional Analysis","volume":"290 3","pages":"Article 111234"},"PeriodicalIF":1.6,"publicationDate":"2025-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145323192","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-09DOI: 10.1016/j.jfa.2025.111225
Andrea Galasso , Chin-Yu Hsiao
Consider a compact torsion free CR manifold X and assume that X admits a compact CR Lie group action G. Let L be a G-equivariant rigid CR line bundle over X. It seems natural to consider the space of G-invariant CR sections in the high tensor powers as quantization space, on which a certain weighted G-invariant Fourier–Szegő operator projects. Under certain natural assumptions, we show that the group invariant Fourier–Szegő projector admits a full asymptotic expansion. As an application, if the tensor power of the line bundle is large enough, we prove that quantization commutes with reduction.
{"title":"Quantization and reduction for torsion free CR manifolds","authors":"Andrea Galasso , Chin-Yu Hsiao","doi":"10.1016/j.jfa.2025.111225","DOIUrl":"10.1016/j.jfa.2025.111225","url":null,"abstract":"<div><div>Consider a compact torsion free CR manifold <em>X</em> and assume that <em>X</em> admits a compact CR Lie group action <em>G</em>. Let <em>L</em> be a <em>G</em>-equivariant rigid CR line bundle over <em>X</em>. It seems natural to consider the space of <em>G</em>-invariant CR sections in the high tensor powers as quantization space, on which a certain weighted <em>G</em>-invariant Fourier–Szegő operator projects. Under certain natural assumptions, we show that the group invariant Fourier–Szegő projector admits a full asymptotic expansion. As an application, if the tensor power of the line bundle is large enough, we prove that quantization commutes with reduction.</div></div>","PeriodicalId":15750,"journal":{"name":"Journal of Functional Analysis","volume":"290 2","pages":"Article 111225"},"PeriodicalIF":1.6,"publicationDate":"2025-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145269296","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}