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Aug
26
revised Is there any difference between massless Dirac fermions and Weyl fermions?
changed unbounded to uncoupled
Aug
26
suggested approved edit on Is there any difference between massless Dirac fermions and Weyl fermions?
May
19
revised Time derivative of the state vector as expressed in abstract Hilbert space vs. as a wavefunction
Changed scalar product to norm.
May
18
suggested approved edit on Time derivative of the state vector as expressed in abstract Hilbert space vs. as a wavefunction
May
18
comment Time derivative of the state vector as expressed in abstract Hilbert space vs. as a wavefunction
I don't understand why there should be any difference, because in both cases we speak of mappings from a subset of R to basically the same Hilbert space (the abstract space and its realization as L^2 are isomorphic). The x (or p) variable is 'frozen' when discussing the partial derivative in the case of the wavefunction and is 'hidden' and also 'frozen' when the abstract space is considered...
May
18
comment solution of pendulum equation
I think you can solve that non-linear ODE through elliptic functions/integrals.
May
9
revised Is there any relationship between gauge field and spin connection?
Corrected some formulas
May
8
suggested approved edit on Is there any relationship between gauge field and spin connection?
May
6
comment Why fermions have a first order (Dirac) equation and bosons a second order one?
The natural occurence of spin (as per the analysis of Dirac 1928 and Levy Leblond 1967) stems from departing from the 2nd order differential equations of classical physics. Remember that Newton's equations are second order in time, the wave equation is second order in both time and space. We 'build' Lagrangian (densitites) to lead us to 2nd order DEs. Classical physics as a whole (apart frpm some freaky equations in linear elasticity) is built on 2nd order differential equations. The cornerstone is the probabilistic interpretation of the wave function of Born 1927.
May
4
answered What is the precise definition of state of a quantum system?
Apr
8
awarded  Critic
Mar
30
comment Hilbert space in quantum mechanics
Actually, the Hilbert space is unique in a mathematical sense: any 2 infinite-dimensional separable Hilbert spaces are isomorphic.
Feb
25
revised Representations of the Poincare group
Reformulated the first question so that it's logically connected to the second
Feb
25
suggested approved edit on Representations of the Poincare group
Feb
23
answered Is there any time-dependent hydrogen atom Schrödinger equation, solvable analytically?
Feb
18
revised What's the physical intuition for symplectic structures?
'symplectic' is the proper term
Feb
18
suggested approved edit on What's the physical intuition for symplectic structures?
Feb
17
answered Is the Lorentz group compact (and if not, is U(1)?)
Feb
17
comment Is the Lorentz group compact (and if not, is U(1)?)
@GiuseppeNegro, the unit operator on a TVS is trivially unitary, hence non-compact groups also have finite dimensional unitary representations, albeit only 1, the so-called trivial representation which takes any element of the group to the unit operator on the TVS in which you build the representation.
Feb
17
revised Is Einstein-Hilbert action the unique action whose variation gives Einstein's field equations?
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