Tunnelling effect from a Vaidya--de Sitter black hole

In this paper, we extend Parikh' recent work to the Vaidya--de Sitter black hole which is non-stationary. We view Hawking radiation as a tunnelling process across the event horizon and calculate the tunnelling probability when the particle crosses the event horizon. From the tunnelling probability we also find a leading correction to the semiclassical emission rate.