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3h
comment How does the inclusion of vacuum energy modify Newtonian gravity equation of motion?
I'm not sure I agree with this. When finding the cosmological constant's contribution, what makes the point $r=0$ special? The equation $\nabla^2 \phi = \Lambda$ is inconsistent with the usual boundary condition that the potential goes to zero at infinity.
Apr
26
comment Using symmetry to determine a hydrogen electron's decay route from $|300\rangle$ to $|100\rangle$
I'm tempted to say that $m$ doesn't matter by rotational symmetry, but I don't know if that can be turned into a rigorous argument.
Apr
18
comment Integrated Ward Identity
I don't see why Stokes' theorem wouldn't work. There would be a problem if the $\partial_\mu$ was inside the time ordering, but it's not, so you have $\langle j_\mu(x)O(y)\rangle$ which just a regular function.
Apr
15
comment Why different substances have different specific heat capacities?
Temperature is not defined as the average kinetic energy of molecules. That's only the case for an ideal gas.
Apr
11
comment Why not measure the velocity of a quantum particle by $\frac{\Delta \vec{x}}{\Delta t}$
I don't know about Bohr's quote, but this is covered in Landau & Lifshitz, and it's very simple: because measuring the position collapses the state to one with no definite velocity, your expression doesn't have a limit as $t_2 \to t_1$.
Apr
10
comment A wall-outlet's hot-slot pulses energy in only ONE direction…toward the ground. How can this be considered ALTERNATING?
It's the current that goes back and forth, not the energy.
Apr
9
awarded  Necromancer
Apr
8
comment Why can't I use conservation of energy to find ratio of final velocities on different planets?
@TheGhostOfPerdition: The only possible relation between $v$, $g$ and $h$ is $v \propto \sqrt{gh}$.
Apr
8
comment Why can't I use conservation of energy to find ratio of final velocities on different planets?
As far as I can see your analysis is correct. It even follows by dimensional analysis, without doing any math.
Apr
5
comment The Theoretical Minimum: Confusion Over Susskind's Reasoning for mutually orthogonal states
How much linear algebra do you know? Do you know what a vector space is? A basis? Representation of a vector in a basis? Inner products?
Mar
29
comment Energy eigenfunctions of particle on a ring
On a ring there's only one angular coordinate. Otherwise, what you're doing is fine.
Mar
21
revised The Theoretical Minimum: Confusion Over Susskind's Reasoning for mutually orthogonal states
added 1301 characters in body
Mar
21
comment The Theoretical Minimum: Confusion Over Susskind's Reasoning for mutually orthogonal states
@MonaLisaOverdrive: Remember that kets are abstract vectors. If we take $\{|u\rangle, |d\rangle\}$ as a basis, that means that $|u\rangle$ is the x-axis and that $|d\rangle$ is the y-axis. Draw $|r\rangle$ in a plane and figure out a vector orthogonal to it.
Mar
20
answered The Theoretical Minimum: Confusion Over Susskind's Reasoning for mutually orthogonal states
Mar
20
answered Is Keplers First Law a consequence of the conservation of angular momentum?
Mar
19
comment A twin-like paradox, with no acceleration and no 3rd reference point. What would happen?
If the velocity changes, there is still acceleration. If it changes instantaneously, then the acceleration is infinite.
Mar
18
answered Change in energy during orbital decay
Mar
18
reviewed Reject How many states does a qubit have?
Mar
15
comment Lorentz Invariants and Time dilation/Distance contraction?
Because they are defined as the mass and time as measured in the rest frame. They're invariant by definition.
Mar
15
comment Computing the pole mass from a given $\overline{MS}$ mass?
@JakobH: You can use whatever $\mu$ you want, because the pole mass must be independent of it. $m_R$ depends on $\mu$ in just the right way so that at each order in $\alpha$, $m_P$ is independent of $\mu$.