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  • 9 votes cast
Apr
7
comment Is it possible that an heavier object is attracted with a higher speed than a lighter by a magnet?
True, but the residual magnetic field is I guess beyond the scope of this question as the author suggests that the only feature differentiating the balls is their mass, not the initial magnetization.
Apr
7
answered Lowest energy product state of a local hamiltonian
Apr
7
comment Is it possible that an heavier object is attracted with a higher speed than a lighter by a magnet?
I do not agree, magnetization is the magnetic moment per volume... it is trivially the same as both balls are made of iron.
Apr
7
comment Capture the entire light field of a 3D scene and construct a virtual scene
Take a following point of view: if you put a newspaper close to a wall, and lood from behind the newspaper at the wall, the wall changes color to a "grayish" tone. What is written does not matter, what matters is the % of the black ink on the frontpage. To capture the image from the wall and even roughtl reconstruct the newspaper look based on that seems impossible (the sensor data is noisy, and the diffusive reflection is essentially an estremely strong "gaussian blur" filter applied to the input data - see in photoshop: unsharp mask cannot reverse a big radius gaussian blur filter ).
Apr
7
comment Capture the entire light field of a 3D scene and construct a virtual scene
I think the answer is no, at several levels: - capturing all light = no cloning thorem prohibits determination of a quantum state - However the quantum state knowledge may not be necessary - maybe computing based on large sensor input would be sufficient. Unfortunately to move around and see behind objects one would have to capture photons emitted by a back surface of a object reflected off other objects. If the wall would be a mirror then this could be possible, but walls are diffusive surfaces reflecting rays in all directions. I believe the reconstruction in hampered by a "butterfly effect"
Mar
18
awarded  Yearling
Mar
9
comment Expectation value of position operator $X$ in momentum space
what do you mean: "there is some neat results like zero or one." ??
Feb
18
comment How come lenses alter the path of photons?
It is, but the material, glass, though transparent from the point of view of a photon, is able to alter the average speed of a photon (instantaneous speed of a photon is of course c all the time). Photon is a mediator of EM interaction in the QED sense, and it interacts electromagnetically with charged particles, say electrons of atoms. As photon scatters elastically (keeping energy) from atom it may change the direction of movement. This means that on average it propagates slower though the medium.
Feb
17
comment Time evolution of the universal wave function
I think these consideration go beyond the scope of Quantum Mechanics. They are purely academic considerations. Having said so, why would the wavefunction of the universe (or any isolated system) be an eigenfunction?
Feb
17
answered What does Liouville's Theorem actually mean?
Nov
5
comment Probability of splitting nucleus
distance between two hydrogen atoms is approximately 1.2 Angstroms, and their radius is 0.5 Angstroms. The atomic distance is such because atoms have effect on each other - wan der Waals interaction. Do you mean nuclei again?
Nov
5
comment Probability of splitting nucleus
What do you mean by "atoms" touch? The atoms can touch, or ever overlap each other. What you say is true for nuclei, not for "atoms"
Nov
5
answered Probability of splitting nucleus
Jul
19
awarded  Commentator
Jul
19
comment Addition of two spins
How exactly it is important the two spins are being added? In the first question, indeed it is sufficient to consider the commutativity of the two operators. But for the second point, we are given two commuting operators spin operators S1 and S2, and total spin operator Si sirely commutes with its spin-z projection. So the last point seems rather trivial - just consider product basis of spin eigenbasis for each of S1 and S2 operators - there the addition does not play a role, as you are looking for eigenbasis for Si, not S.
Sep
19
comment Equation of everything
@Dimension10 - ok. thanks
Sep
17
comment Equation of everything
I do not like the "i" in the third term in the exponent. It seems incompatible with the i/hbar in front of the integral. Some terms seem to be taken in real time, some in the imaginary time. Also it does not specify over which fields the variables are taken.
Jan
12
answered Estimating atmospheric friction by measuring the change in velocity of a ball thrown straight upwards
Jan
11
comment equivalence of wave equations
yes, my argument is only applicable to functions. Nevertheless what sort of behaviour is to expect around $t=0$? I think that this is just a "step" of height $s(\vec r)$, then $t$-derivative gives $\delta(t) s(r)$, second derivative gives $\delta'(t)s(r)$. The second equation would give the same if we assumed additionally that $\psi(t<0,\vec r)=0$. I guess then the solution may in fact be just a discontinous function around $t=0$ (and of course a distribution by local integrability). The problem is the second equation does not gieanything special about $t<0$
Jan
9
comment equivalence of wave equations
how is it possible that $\psi(vec r, t)$ can be both equal to $s(\vec r)$ and on the other hand to zero? Except for $s=0$ that is...