Upper estimates of the lifespan for the fractional wave equations with time-dependent damping and a power nonlinearity of subcritical and critical Fujita exponent

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Main Authors: Lin, Jiayun, Ikeda, Masahiro
Format: Preprint
Published: 2024
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_version_ 1866917766835994624
author Lin, Jiayun
Ikeda, Masahiro
author_facet Lin, Jiayun
Ikeda, Masahiro
contents In this paper, we study the Cauchy problem of the fractional wave equation with time-dependent damping and the source nonlinearity $f(u)\approx |u|^p$: $$ \begin{cases} \partial_t^2u(t,x)+(-Δ)^{σ/2} u(t,x)+b(t) \partial_t u(t,x) =f(u(t,x)),\ &(t,x)\ \in [0,T)\times \mathbb{R}^N,\\ u(0,x)=u_0(x),\ \partial_tu(0,x)=u_1(x),\ &x\ \in\ \mathbb{R}^N, \end{cases} $$ where $b(t)\approx (1+t)^{-β}$. In the subcritical and critical cases $1<p\leq p_c:=1+\frac σN$, we derive the upper estimates of the lifespan for fractional Laplacian with $0<σ<2$ and time-dependent damping $β\in [-1, 1)$ by the framework of ordinary differential inequality. The blow-up results, with the global existence in the supercritical case $p_c<p<\frac{N}{N-σ}$ obtained in [19], shows that the critical exponent for the fractional wave quation is $p_c=1+\fracσ{N}$ for $0<σ<2$. Moreover, together with the lower estimate of lifespan derived in [19], we could conclude that the estimate in this paper is sharp. Note that the our result of the critical case is completely new even in the classical case $b(t)=1$. We also consider the case of $β=1$, and obtain the upper estimate of the lifespan.
format Preprint
id arxiv_https___arxiv_org_abs_2401_10552
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Upper estimates of the lifespan for the fractional wave equations with time-dependent damping and a power nonlinearity of subcritical and critical Fujita exponent
Lin, Jiayun
Ikeda, Masahiro
Analysis of PDEs
35B44, 35A01, 35L15, 35L05
In this paper, we study the Cauchy problem of the fractional wave equation with time-dependent damping and the source nonlinearity $f(u)\approx |u|^p$: $$ \begin{cases} \partial_t^2u(t,x)+(-Δ)^{σ/2} u(t,x)+b(t) \partial_t u(t,x) =f(u(t,x)),\ &(t,x)\ \in [0,T)\times \mathbb{R}^N,\\ u(0,x)=u_0(x),\ \partial_tu(0,x)=u_1(x),\ &x\ \in\ \mathbb{R}^N, \end{cases} $$ where $b(t)\approx (1+t)^{-β}$. In the subcritical and critical cases $1<p\leq p_c:=1+\frac σN$, we derive the upper estimates of the lifespan for fractional Laplacian with $0<σ<2$ and time-dependent damping $β\in [-1, 1)$ by the framework of ordinary differential inequality. The blow-up results, with the global existence in the supercritical case $p_c<p<\frac{N}{N-σ}$ obtained in [19], shows that the critical exponent for the fractional wave quation is $p_c=1+\fracσ{N}$ for $0<σ<2$. Moreover, together with the lower estimate of lifespan derived in [19], we could conclude that the estimate in this paper is sharp. Note that the our result of the critical case is completely new even in the classical case $b(t)=1$. We also consider the case of $β=1$, and obtain the upper estimate of the lifespan.
title Upper estimates of the lifespan for the fractional wave equations with time-dependent damping and a power nonlinearity of subcritical and critical Fujita exponent
topic Analysis of PDEs
35B44, 35A01, 35L15, 35L05
url https://arxiv.org/abs/2401.10552