Long-Run Aggregate Supply
The Long-Run Aggregate Supply (LAS) represents the relationship between the price level and output in the long-run. It differs from the Short-Run Aggregate Supply (SAS) in that no input prices are assumed to be constant. Thus, LAS is a representation of potential output.
The LAS curve is vertical because it shows potential output and when this happens all prices, even input prices, rise when a rise in price level occurs.