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comment Is the Legendre transformation a unique choice in analytical mechanics?
I wonder if there is a typo in the following sentence: "... does not happen for field theories and interacting particles theories (it does happen for the point particle, though)". Its seems a bit unclear as obviously point particles can also be interacting.
Jun
29
answered Single field vs single clock inflation?
Jun
29
answered Possible values of an observable are the eigenvalues of an operator
Jun
18
awarded  Yearling
Jun
7
comment How many particles in $\phi_0(x)^2|0\rangle$?
One more question: shouldn't $$N{\phi^+}^2(x)|0\rangle = 2 {\phi^+}^2(x)|0\rangle$$ be $$N{\phi^-}^2(x)|0\rangle = 2 {\phi^-}^2(x)|0\rangle$$ ?
Jun
7
accepted How many particles in $\phi_0(x)^2|0\rangle$?
Jun
7
comment How many particles in $\phi_0(x)^2|0\rangle$?
Thanks again for your help.
Jun
7
comment How many particles in $\phi_0(x)^2|0\rangle$?
Thanks, that's very helpful. Should the + and - be swapped around in that last line?
Jun
7
asked How many particles in $\phi_0(x)^2|0\rangle$?
Jun
6
accepted Order of index in Lorentz transform
Jun
6
comment Order of index in Lorentz transform
@bechira I think it would be interesting to know as its otherwise such a good qft textbook. I think the answer is by $\Lambda^\mu_\nu$ he means $\Lambda^\mu{}_\nu$.
Jun
6
revised Order of index in Lorentz transform
more detail added
Jun
6
asked Order of index in Lorentz transform
May
30
comment Cosmological Constant on the LHS of Einstein's Field Equation
@Conifold I disagree with your ether analogy. The ether is disfavored observationally and theoretically compared to relativity. While in the CC case there is no strong experimental or physical argument that favors the term being on the LHS or RHS of the equation.
May
29
comment Cosmological Constant on the LHS of Einstein's Field Equation
Einstein did originally see it as a modification to the LHS. If you think of the GR Lagrangian as a series in R, the cosmological constant is just the first term in the series $R^0$. The physics is the same if its put on the LHS or RHS.
May
28
comment Calculating curvature of spacetime when energy is present
You need to work out the energy momentum tensor $T^{\mu\nu}$ that goes on the RHS of Einstein's eq.
May
18
comment Entropy of a system of gravitationally interacting particles
Gravitationally collapsed systems are not in thermodynamic equilibrium, see pg 378 of Binney and Tremaine, "Galactic Dynamics", 2nd ed.
May
11
answered Cosmology: collisionless vs collisional fluids?
May
7
comment Could there be a dark matter planet?
The minimum halo mass of dark matter is model dependent with some dark matter models allowing earth mass halos and other requiring the minimum halo size to be much larger.
Apr
24
comment Could the missing antimatter lie outside the observable universe?
This is related to the idea of a multi-verse. It would need some way of the asymmetry to vary during inflation. I'm guessing there are some models that could do this, but haven't looked into it in too much detail.