What Are the Assumptions Behind the Model of a Perfectly Competitive Industry in Long-Run Equilibrium?

The firm is a profit maximized orientated market. They will do as much as they can to have their profits to super normal level (maximum profit is achieved). They cant all do this as all companies have a limited financial depot, and all have to realize where to stop, so that all levels of production are optimal and efficiency cannot be better. For a long-run situation, when there is supernormal profit, a lot of companies will enter the market, and visa versa.
In conclusion, the assumptions that economists make are realistic as to the part where it is still theoretical. Beyond theory the assumptions are no longer realistic as there is no company that will be a 100% identical to the next one, or there is no whole market of firms that can live um to the assumptions. This is why the economists have to be flexible and adjust the model for every case.
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