<p>In this work we introduce the concept of <i>generalized exponential</i> <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="245_2025_10330_Article_IEq1.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="29" /> </InlineMediaObject> <EquationSource Format="TEX">\({\mathfrak {D}}_{\mathcal {C}^*}\)</EquationSource> </InlineEquation><i>–pullback attractors</i> for evolution processes, which are compact and positively invariant families that pullback attract all elements of a universe of families <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="245_2025_10330_Article_IEq1.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="29" /> </InlineMediaObject> <EquationSource Format="TEX">\({\mathfrak {D}}_{\mathcal {C}^*}\)</EquationSource> </InlineEquation>, with an <i>exponential rate</i>. Such concept, within the pullback framework for nonautonomous problems, was introduced in Bortolan et al. (Appl Math Optim 89(62):1–52, 2024) for more general <i> decay functions</i> (which include the exponential decay), but for fixed bounded sets rather than for a universe of families, and was inspired by Zhao et al. (Estimate of the attractive velocity of attractors for some dynamical systems, <a href="http://arxiv.org/abs/2108.07410">http://arxiv.org/abs/2108.07410</a>, 2021), which dealt with the autonomous case. We prove a result that ensures the existence of a generalized exponential <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="245_2025_10330_Article_IEq1.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="29" /> </InlineMediaObject> <EquationSource Format="TEX">\({\mathfrak {D}}_{\mathcal {C}^*}\)</EquationSource> </InlineEquation>–pullback attractor for an evolution process, using the concept of <i>pullback</i> <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="245_2025_10330_Article_IEq6.gif" Format="GIF" Height="10" Rendition="HTML" Resolution="72" Type="Linedraw" Width="13" /> </InlineMediaObject> <EquationSource Format="TEX">\(\kappa \)</EquationSource> </InlineEquation><i>–dissipativity</i> for evolution processes with respect to a general universe <InlineEquation ID="IEq7"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="245_2025_10330_Article_IEq7.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="16" /> </InlineMediaObject> <EquationSource Format="TEX">\({\mathfrak {D}}\)</EquationSource> </InlineEquation>. This required an adaptation of the results presented in Bortolan et al. (Appl Math Optim 89(62):1–52, 2024), which only covered the case of a polynomial rate of attraction for fixed bounded sets. Later, we prove that a nonautonomous wave equation has a generalized exponential <InlineEquation ID="IEq8"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="245_2025_10330_Article_IEq1.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="29" /> </InlineMediaObject> <EquationSource Format="TEX">\({\mathfrak {D}}_{\mathcal {C}^*}\)</EquationSource> </InlineEquation>–pullback attractor. This, in turn, also implies the existence of the <InlineEquation ID="IEq9"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="245_2025_10330_Article_IEq1.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="29" /> </InlineMediaObject> <EquationSource Format="TEX">\({\mathfrak {D}}_{\mathcal {C}^*}\)</EquationSource> </InlineEquation>–pullback attractor for such problem.</p>

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Generalized exponential \({\mathfrak {D}}_{\mathcal {C}^*}\)–pullback attractor for a nonautonomous wave equation

  • Matheus C. Bortolan,
  • Tomás Caraballo,
  • Carlos Pecorari Neto

摘要

In this work we introduce the concept of generalized exponential \({\mathfrak {D}}_{\mathcal {C}^*}\) –pullback attractors for evolution processes, which are compact and positively invariant families that pullback attract all elements of a universe of families \({\mathfrak {D}}_{\mathcal {C}^*}\) , with an exponential rate. Such concept, within the pullback framework for nonautonomous problems, was introduced in Bortolan et al. (Appl Math Optim 89(62):1–52, 2024) for more general decay functions (which include the exponential decay), but for fixed bounded sets rather than for a universe of families, and was inspired by Zhao et al. (Estimate of the attractive velocity of attractors for some dynamical systems, http://arxiv.org/abs/2108.07410, 2021), which dealt with the autonomous case. We prove a result that ensures the existence of a generalized exponential \({\mathfrak {D}}_{\mathcal {C}^*}\) –pullback attractor for an evolution process, using the concept of pullback \(\kappa \) –dissipativity for evolution processes with respect to a general universe \({\mathfrak {D}}\) . This required an adaptation of the results presented in Bortolan et al. (Appl Math Optim 89(62):1–52, 2024), which only covered the case of a polynomial rate of attraction for fixed bounded sets. Later, we prove that a nonautonomous wave equation has a generalized exponential \({\mathfrak {D}}_{\mathcal {C}^*}\) –pullback attractor. This, in turn, also implies the existence of the \({\mathfrak {D}}_{\mathcal {C}^*}\) –pullback attractor for such problem.