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location Greece
age 75
visits member for 4 years, 3 months
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Retired experimental particle physicist.

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


Feb
18
comment Do photons and cosmic rays radiate energy through gravitational waves? If not, why not?
@MattReece Thanks for the link
Feb
17
comment Do photons and cosmic rays radiate energy through gravitational waves? If not, why not?
@MattReece Can you give a readable link for these claims. ?
Feb
17
comment Do photons and cosmic rays radiate energy through gravitational waves? If not, why not?
@MattReece Gneral Relativity is not a quantum theory at unified level including photons etc. Photons as elementary particles are put in by hand if one hand waves a quantization of gravity.An interaction of photons and gravitons requires a unified consistent theory to be valid, a vertex in a Feynman type diagram, imo
Feb
17
answered Do photons and cosmic rays radiate energy through gravitational waves? If not, why not?
Feb
16
comment Continuum limit for solid mechanics
This needs a solid state expert for an answer. For example stresses and strains that you ask about have to be related with the lattice dimensions through the electromagnetic forces which are finally responsible. Hand waving: a simulation should use much higher distances than the lattice distance for continuum, a classical idea because if you simulate the em forces the discreteness will be important combined with the size of the force. lets say the effective momentum of the exchanged virtual photons times the dimensions in space in the simulation should be larger than h_bar/2
Feb
16
answered Continuum limit for solid mechanics
Feb
16
comment Continuum limit for solid mechanics
I will make an answer out of it.
Feb
16
comment Continuum limit for solid mechanics
@Danu Sorry sorry, it is the Planck constant n (en.wikipedia.org/wiki/Planck_constant )Some linguistic confusion with the uncertainty principle which depends on it and is denoted by h.
Feb
16
comment Is energy lost in an elastic tunneling process?
can you give a link for P=IV ? I suspect it comes from classical considerations. Quantum mechanically there is no energy loss in the tunneling. There may be in the rest of the circuit which has to exist for a current to form and which is adequately described by classical formulae with resistances etc where the power will be lost..
Feb
16
answered Why meet at the center of mass?
Feb
16
comment Is uncertainty principle a technical difficulty in measurement?
@Gotaquestion What a nice way to start the day with complements :) . thanks
Feb
16
comment Ideal gas law problems
Yes, the neglect is the part in the link that talks of "no interactions" .Tiny spheres act as point particles through their center of mass and the only interaction is scattering and sharing kinetic energy. Think a bit, if they were only a point there would be no geometrical cross section for scattering and scattering would have very small probability.
Feb
15
answered Ideal gas law problems
Feb
15
comment Is energy lost in an elastic tunneling process?
if it is quantum mechanical tunneling you are talking about energy should not be lost. have a look at hyperphysics.phy-astr.gsu.edu/hbase/quantum/barr.html .
Feb
15
comment Is there any place for teleology in physics?
according to the definition in your link the increase in entropy second law of thermodynamics sounds teleological to me.
Feb
15
revised Does physics have some division schema which divide physical amounts into these two classes?
added a paragraph to correspond to last questions
Feb
15
answered Does physics have some division schema which divide physical amounts into these two classes?
Feb
14
answered Can entropy of a system decrease if we wait long enough?
Feb
14
comment Angular momenta of photon
The angular momentum of individual photons has a meaning only with respect to the vortex axis or any other axis as spin axis. It can only be seen within an ensemble of photons because as everything quantum mechanical it is a probability distribution which one gets from many repeats of the same experiment.In the case of photons the ensemble gives the repeats.
Feb
13
comment Angular momenta of photon
if you could get the nuclei spins oriented all in the same direction then you would see the quadrupole or whatever pattern in the classical ensemble of photons coming out