Discover Feynman's path integral formulation of quantum mechanics! 📝 Get the notes for free here: https://courses.physicswithelliot.com...

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   • But why wavefunctions? A practical ap...  

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⚛️ Additional links:
- Feynman's 1964 lecture on quantum mechanics:
https://www.feynmanlectures.caltech.e...

- Feynman's PhD dissertation can be found in this book:
https://www.worldscientific.com/world...

- Feynman's original paper on the path integral:
https://authors.library.caltech.edu/r...

- Dirac's 1932 paper that inspired Feynman:
https://www.worldscientific.com/doi/1...

- Feynman's Nobel lecture, including the origin story of the path integral:
https://www.nobelprize.org/prizes/phy...

- Feynman and Hibbs's textbook "Quantum Mechanics and Path Integrals" from the 1960s:
https://books.google.com/books/about/...

📖 Video summary:

If you've learned some quantum mechanics before, you've probably seen it described using wavefunctions, and the Schrödinger equation, and so on. That's how quantum mechanics was originally constructed by people like Schrödinger, Born, Heisenberg, and many others in the 1920s.

In the 1940s, though, a 20-something-year-old grad student named Richard Feynman discovered another approach. He found that the motion of a quantum particle can be described by taking a sum over ALL the possible trajectories that the particle could conceivably follow. That sum over all quantum paths is what's nowadays called the Feynman path integral, and it's central to our modern understanding of quantum physics.

One of the most important lessons Feynman's perspective reveals is how the usual laws of classical mechanics emerge from this more fundamental, but seemingly very different, quantum mechanical description of nature. In the video, you'll see why a single, special path emerges from the sea of all possible quantum paths when we consider the motion of a big object like a baseball--called the path of stationary action. And that of course is the path that obeys F = ma!

0:00 Introduction
3:12 Quick overview of the path integral
5:46 Review of the double-slit experiment
8:32 Intuitive idea of Feynman's sum over paths
13:27 Why exp(iS/hbar)?
15:00 How F = ma emerges from quantum mechanics
23:15 Lagrangian mechanics
24:34 Feynman's story
25:22 Next time: how to compute the path integral?

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About me:
I’m Dr. Elliot Schneider. I love physics, and I want to help others learn (and learn to love) physics, too. Whether you’re a beginner just starting out with your physics studies, a more advanced student, or a lifelong learner, I hope you’ll find resources here that enable you to deepen your understanding of the laws of nature. For more cool physics stuff, visit me at https://www.physicswithelliot.com.