“…Motivated by the fundamental works [10,17] and the subsequent ones [3,6,7,11,19], the frequency domain approach has become a very useful tool to analyze the long-time behaviors (including exponential/polynomial/logarithmic stability) of many autonomous systems in infinite dimensions. This approach leads to not only a relatively concise and elementary argument, but also an optimal decay rate estimate for the problem under consideration at least for some relatively simple geometrical configurations, such as one-dimensional or rectangular domains (e.g., [4,5,13,15]). Meanwhile, compared to the arguments based on micro-local analysis, this approach requires considerably weaker smoothness conditions on the data (including particularly the boundaries of the space domains in which the systems evolve).…”