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243165
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location Greece
age 75
visits member for 4 years, 5 months
seen 48 mins ago

Retired experimental particle physicist.

The picture is a fayum . It looks like aunts and cousins of mine :).


1d
comment Why do particles and antiparticles annihilate?
please look at physics.stackexchange.com/questions/190463/… where I have recently answered the same question
1d
comment A confusion regarding a paragraph in The Feynman Lectures
I have the impression that one should add a little weight on the left pan to get it started to lift the right pan, as we look at the page. If we take a bit off the left the right will sink , not lift. It is probably a confusion between left and right.
1d
comment How is quantum superposition different from mixed state?
particle A from particle N will control whether the superposition of the individual wave functions is entangled/coherent or not. If it is coherent, it is called mixed. If it is incoherent it is just a superposition of independent wavefunctions which is the classical limit.
1d
comment How is quantum superposition different from mixed state?
In my view a pure state is a state with a single wave function solution of the boundary conditions. This is feasible with few particles entering the equation . From then on one has to use approximations. One type of approximation is to assume all the external interactions to the system under consideration can be replaced by a potential . Then again one can have a pure solution, to approximate the situation. Mixed solutions come when one takes individual wave functions representing the particles and approximates the solution of the total state with the density matrix. Here the "distance" of
1d
comment In atomic bomb tests under ground, where does the volume of the rocks go?
The point to stress is the "vapor turned to liquid lava" . Lava cools to a very dense state, much denser than the original soil. This will have the smallest volume for the matter in the hole, and that is why cavities that turn into craters can form.
1d
comment How is quantum superposition different from mixed state?
@user36790 above was for your question. I edited my answer and changed it because it was confusing the issues
1d
comment How is quantum superposition different from mixed state?
have a look en.wikipedia.org/wiki/Phase_%28waves%29 . The wave function gets its name because it has mainly sinusoidal expressions.
2d
comment Can you depict the electron's electromagetic field?
the electromagnetic field of radiation is relatively simple en.wikipedia.org/wiki/File:Electromagneticwave3Dfromside.gif
Jun
26
comment Does photon have size measurement because of its particle nature
@danielAzuelos Photons are quantum mechanical entities. They are not waves of energy as classical EM waves. They are described by a probability which depends on a wave function squared, i.e. has a sinusoidal form but it is a PROBABILITY to be at (x,y,z,t) and a point can describe it. The link I gave shows how these probability waves build up the classical wave which is an energy wave traveling in space.
Jun
26
comment Why doesn't atmospheric pressure crush thick walled structures?
Yes, larger area sums up to more force, except inside and outside is balanced dA in dA out to zero. Only if there is a vacuum or extra pressure as in pressure vessels the inside force is larger than the outside and if the walls are not rigid enough to withstand the force there will be an explosion as in in overblown balloon. The area is not a variable in the problem of balancing in and out forces
Jun
26
comment Does photon have size measurement because of its particle nature
@danielAzuelos Yes, the electromagnetic wave needs space , but it is composed out of zillions of elementary particles/photons see motls.blogspot.com/2011/11/…
Jun
26
comment The magnetic field of a magnetic monopole
by mistake a minus was hit. I am editing so I can reverse it.
Jun
26
comment How many human cells will get affected at the prick of a pin?
a cosmic muon traversing the human body is like an infinitely thin needle for the order of magnitude of the cell.
Jun
26
comment In a CMCS 2-body system, why does the speed of the particles after collision stay the same?
It is the definition of "elastic " after all. If the kinetic energies of the particles change ( deformation for a classical example) it is called inelastic.
Jun
26
comment How many human cells will get affected at the prick of a pin?
it is a biology question
Jun
26
comment Why doesn't atmospheric pressure crush thick walled structures?
The area cannot but be the same, by the definition, only P and F are variable.
Jun
25
comment Heisenberg uncertainty principle clarification
Have a look at youtube.com/v/…
Jun
24
comment Why doesn't atmospheric pressure crush thick walled structures?
Your atmospheric pressure guarantees that the forces balance . That is what atmospheric pressure means, no matter how thin the material. After all you can imagine a box, no material, and if there is no wind there is no motion inside outside. When a wall intervenes it transfers the forces with its rigidity structure, and as long as the inside and outside pressure is equal nothing happens.
Jun
24
comment Can we have physical quantities which have magnitude and direction but are not vectors?
@Mew see additon above. Physical quantities with amplitude and direction can be measured but do not follow simple vector algebra as the tensor has nine components.
Jun
23
comment What's the significance of neutrino oscillations?
That is why string theory is fascinating me, because the groups emerge from the mathematics naturally, and the data can be slotted in. The same reason gives rise to the fascination with strings because supersummetry appears mathematically in a set of theories. Supesymmetry was invoked to solve infinity problems with the calculations of the standard model and in some string theories is is there mathematically. Ad hoc mathematical models, though correct, if they cannot fit the measured group structures are just irrelevant. That should be 1963, I had started with F centers in graduate school