Large-data global solutions to a quasilinear model for viscuos acoustic wave propagation in a non-isothermal setting

The manuscript considers the model for conversion of mechanical energy into heat during acoustic wave propagation in the presence of temperature-dependent elastic parameters, as given by $$\left\{ \begin{array}{l} u_{tt} = (\gamma(\Theta) u_{xt})_x + a (\gamma(\Theta) u_x)_x, \\[1mm] \Theta_t = D\Theta_{xx} + \gamma(\Theta) u_{xt}^2. \end{array} \right. \qquad \qquad (\star)$$ It is firstly shown that when considered along with no-flux boundary conditions in an open bounded real interval $\Omega$, under the assumption that $\gamma\in C^2([0,\infty))$ is such that $\gamma>0$ and $\gamma'\ge 0$ on $[0,\infty)$ as well as $$D\cdot (\gamma+D) \cdot \gamma'' + 2\gamma \gamma'^2 \le 0 \qquad \mbox{on } [0,\infty),$$ for all suitably regular initial data this problem admits a globally defined classical solution. This complements recent findings in the literature, according to which ($\star$) may admit solutions blowing up in finite time whenever $\gamma$ is positive and nondecreasing on $[0,\infty)$ with $\int_0^\infty \frac{d\xi}{\gamma(\xi)} < \infty$. Apart from that, it is found that if the additional assumption $$a|\Omega|^2 \le \frac{\pi^2 \gamma(0)}{1+\sqrt{1+\frac{\gamma(0)}{D}}}$$ is satisfied, the all these solutions stabilize toward some spatially homogeneous equilibrium in the large time limit.