Given a problem, is it possible to prove what the best worst-case efficiency of an algorithm to solve this problem would be?
For example, lets take the problem of sorting an array.
Many of the simpler sort algorithms have a worst-case efficiency of O(n^2)
$O(n^2)$ such as Quick Sort and Bubble Sort. However, there are other algorithms such as Timsort and Smoothsort that have O(n log n)
$O(n \log n)$, which is more efficient.
No other algorithm (to my knowledge) has been able to sort an array more efficiently thatthan O(n log n)
$\Theta(n\log n)$. Is it possible to prove that no other algorithm exists that is more efficient?
If there is a way to prove for sorting algorithms if an algorithm exists that is more efficient, does this apply to other problems as well?