Single impurity in the Totally Asymmetric Simple Exclusion Process

We examine the behavior of a single impurity particle embedded within a Totally Asymmetric Simple Exclusion Process (TASEP). By analyzing the impurity's dynamics, characterized by two arbitrary hopping parameters $\alpha$ and $\beta$, we investigate both its macroscopic impact on the system and its individual trajectory, providing new insights into the interaction between the impurity and the TASEP environment. We classify the induced hydrodynamic limit shapes based on the initial densities to the left and right of the impurity, along with the values of the parameters $\alpha$,$\beta$. We develop a new method that enables the analysis of the impurity's behavior within an arbitrary density field, thereby generalizing the traditional coupling technique used for second-class particles. With this tool, we extend to the impurity case under certain parameter conditions, Ferrari and Kipnis's results on the distribution of the asymptotic speed of a second-class particle within a rarefaction fan.