# American Institute of Mathematical Sciences

September  2009, 2(3): 609-629. doi: 10.3934/dcdss.2009.2.609

## Higher order energy decay rates for damped wave equations with variable coefficients

 1 Department of Mathematics, University of Nebraska-Lincoln, Avery Hall 239, Lincoln, NE 68588, United States 2 Department of Mathematics, University of Tennessee, Knoxville, TN 37096-1300 3 Department of Mathematics, University of Tennessee-Knoxville, TN 37996, United States

Received  October 2008 Revised  February 2009 Published  June 2009

Under appropriate assumptions the energy of wave equations with damping and variable coefficients $c(x)$$u_{t t}$-div$(b(x)\nabla u)+a(x)u_t =h(x,t)$ has been shown to decay. Determining the decay rate for the higher order energies of the $k$th order spatial and time derivatives has been an open problem with the exception of some sparse results obtained for $k=1,2$. We establish the sharp gain in the decay rate for all higher order energies in terms of the first energy, and also obtain the sharp gain of decay rates for the $L^2$ norms of the higher order spatial derivatives. The results concern weighted (in time) and also pointwise (in time) energy decay estimates. We also obtain $L^\infty$ estimates for the solution $u$ in dimension $n=3$. As an application we compute explicit decay rates for all energies which involve the dimension $n$ and the bounds for the coefficients $a(x)$ and $b(x)$ in the case $c (x)=1$ and $h(x,t)=0.$
Citation: Petronela Radu, Grozdena Todorova, Borislav Yordanov. Higher order energy decay rates for damped wave equations with variable coefficients. Discrete & Continuous Dynamical Systems - S, 2009, 2 (3) : 609-629. doi: 10.3934/dcdss.2009.2.609
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