Theoretical approaches to nucleation in the gas phase. With a glimpse at experiments and dust formation in astrophysics

An overview of the physics of homogeneous nucleation is presented, focusing on the main theoretical approaches that are currently available. We review the microscopic assumptions behind classical nucleation theory, as well as several improvements with various degrees of empiricism. The increasing role played by molecular simulations in testing and correcting nucleation theories is discussed. Typical laboratory experiments on homogeneous nucleation are also reviewed, emphasizing how experimental observables can be compared with theoretical predictions. Finally, the more specific challenges of nucleation in astrophysical media are discussed