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Quantumwhisp
  • Member for 8 years, 6 months
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37 votes
6 answers
3k views

Must observables be Hermitian only because we want real eigenvalues, or is more to that?

14 votes
1 answer
3k views

Is the usage of the Fock space a postulate in QFT?

14 votes
3 answers
1k views

Justification of the Least Action Principle using conservation of information

13 votes
3 answers
3k views

Is the vacuum state a coherent state?

13 votes
5 answers
954 views

Does an Operator that neither commutes with $\hat{X}$ or $\hat{P}$, nor can be expressed as a "function" of $\hat{X}$ and $\hat{P}$ make sense?

10 votes
2 answers
935 views

Can we always express the EM-Field Hamiltonian as (possibly time dependent) pair of annihilation and creation operators?

10 votes
3 answers
2k views

Is a canonical transformation equivalent to a transformation that preserves volume and orientation?

8 votes
1 answer
698 views

Can any symplectomorphism (1 Definition of canonical transformation) be represented by the flow of a vectorfield?

8 votes
2 answers
2k views

Derive canonical commutation relations from Schwinger's principle

8 votes
2 answers
2k views

Contradiction between Rabi oscillation and energy shifts in AC Stark effect

8 votes
3 answers
828 views

(Coming from Wigner's Theorem): What is a Symmetry in QFT?

8 votes
1 answer
565 views

Where does it become apparent in real scalar QFT that the field has to be an operator-valued distribution, as opposed to an operator-valued function?

7 votes
3 answers
1k views

Rigorous mathematical definition of vector operator?

7 votes
0 answers
591 views

Hamiltonian formulation of the semiclassical Model of electrons

7 votes
2 answers
823 views

Ehrenfest Theorem and boundary Conditions

6 votes
0 answers
410 views

Is there a modified Least Action Principle for nonholonomic systems?

6 votes
1 answer
932 views

Definition of matrix elements of an operator in the path integral formalism wrong?

6 votes
1 answer
856 views

Entropy of subsystem maximized?

6 votes
2 answers
730 views

Formulation of an Action-Principle in a general Phase Space (No Cotangent-Bundle)

6 votes
1 answer
334 views

Locality in the coulomb gauge of classical electrodynamics

6 votes
1 answer
186 views

Spectral theorem in QFT

6 votes
2 answers
277 views

Are Grassmann numbers always "under the hood" if we deal with fermionic ladder / field operators?

6 votes
1 answer
542 views

Definition of the $S$-Matrix in Schwartz QFT-Book: Why is $\langle f, t_f | i, t_i \rangle$ in the Schroedinger picture, and not Heisenberg-picture?

6 votes
1 answer
894 views

Does the LSZ-Reduction Formula work for Photons?

6 votes
2 answers
485 views

Why is time-evolution unitary? - The Heisenberg-picture Version

6 votes
1 answer
453 views

Momentum operator ambiguous?

6 votes
1 answer
836 views

Does Haags Theorem forbid Time-Evolution?

5 votes
1 answer
105 views

Can we assign an Entropy-value to physical systems without modelling them by an ensemble / classical probabilities?

5 votes
3 answers
578 views

Why is it said that it takes more energy to let a house cool down and heat up again, compared to keeping the temperature constant? [duplicate]

5 votes
2 answers
356 views

Derivation of Schwingers action principle from Heisenberg Equation and CCR - Why does it work with Anticommuting variations?

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