Time-independent perturbation theory

Time-Independent Perturbation Theory is a method used in quantum mechanics to approximate the behavior of a system when it is subject to a small change or "perturbation." Imagine you have a well-understood music piece, and you make a slight adjustment to one instrument. Instead of rewriting the entire score, you analyze how that change affects the overall sound. Similarly, in quantum systems, this theory helps us understand how particles behave when influenced by minor changes in their environment, without needing to solve complex equations from scratch. It's essential for understanding real-world systems in physics and chemistry.