# Recent content by betelgeuse91

1. ### I Wave conventions: E(x,t) and E(t), E(x) confusion

Ahh... right. Thank you for clarification. In literature, people confusingly use E(x) and E(t) and take derivatives with respect x and t which drives me crazy....
2. ### I Wave conventions: E(x,t) and E(t), E(x) confusion

I understand that waves are function of space and time in nature, so E(x,t) will be fundamental description of a wave. I notice that often people denote a wave as E(t) for instance, an envelop function of a pulse. For this case, E is an oscillation at a fixed spatial point x? So that the point x...
3. ### Textbook for calculus of variations? Hamiltonian mechanics?

I need to learn about Hamiltonian mechanics involving functional and functional derivative... Also, I need to learn about generalized real and imaginary Hamiltonian... I only learned the basics of Hamiltonian mechanics during undergrad and now those papers I read show very generalized version...
4. ### I Work done on the system through a piston?

This solved the mystery for me... Thank you so much.
5. ### I Work done on the system through a piston?

Then either case I am doing positive work. But the above and other text says when volume expands, external work done on the system is negative and vice versa (so the signs of work I do for compression and expansion of gas are opposite). How does this work?
6. ### I Work done on the system through a piston?

If I consider a piston in equilibrium with atmosphere such that it won't move unless I push it or pull it. This case, whichever way I do, won't I be doing positive work? From above formula for work.
7. ### I Work done on the system through a piston?

I am stuck on like the first page of thermal physics. It seems like the signs of the work done on the system are opposite when the volume is expanded and compressed. But when I imagine myself pushing or pulling the piston, I get confused from W = \textbf{F}\cdot \textbf{d} This work will be...
8. ### A Laser beam represented with complex conjugate?

I see. Thank you!
9. ### A Laser beam represented with complex conjugate?

Boyd - Nonlinear Optics page 5, there says 'Here a laser beam whose electric field strength is represented as $$\widetilde{E}(t) = Ee^{-iwt} + c.c$$But why is it written like this? Is it because the strength is the real part of the complex electric field? Then why doesn't he divide it by 2 after...
10. ### How do I write a report about my 4th year physics research?

Hi, I am a fourth year physics student currently enrolled in a research project course with a supervisor. It's a research in optics and I need to learn about some nonlinear optics. For the report, I want to write about what I have learned during the term, for instance, Rayleigh and Raman...
11. ### I About general solutions to Schrodinger equation

! I see. So the set of solutions we found as above is indeed the set of all the possible solutions by uniqueness. Thank you very much, now I understand what was going on!
12. ### I About general solutions to Schrodinger equation

It looks like that what you showed here is that the time evolution of linear combination of separable solutions is ##\Psi(x,t) = \sum c_n\psi_n(x)\phi_n(t)##. But this only states about evolution of separable solutions, not evolution of general solutions. Can you state the PDE theorem here...
13. ### I About general solutions to Schrodinger equation

I apologize that I forgot to mention that the Hamiltonian concerned here is time-independent, as PeroK pointed out.
14. ### I About general solutions to Schrodinger equation

I see that the eigenfunctions of the Hamiltonian indeed form a complete set such that any function that satisfies time-independent Schrodinger equation ##H\psi=E\psi## can be written as linear combination of them. I also see that the time evolution of that function corresponds to the time...
15. ### I About general solutions to Schrodinger equation

I found this on Griffiths page 25, "Moreover (as is typically the case with separation of variables) we will be able at the end to patch together the separable solutions in such a way as to construct the most general solution."