Title: Carleman estimates for higher order partial differential operators and its applications

Abstract: In this paper, we obtain a Carleman estimate for the higher order partial differential operator. In the process of establishing this estimate, we developed a new method, which is called the back-propagation method (the BPM, for short). This method can also be used to build up Carleman estimates for some other partial differential operators, and might provide assistance with corresponding numerical analyses. As an application of the above-mentioned Carleman estimate, we proved the conditional stability of a Cauchy problem for a time fractional diffusion equation.