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235133
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location Greece
age 74
visits member for 4 years
seen 3 hours ago

Retired experimental particle physicist.

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


3h
comment How does semiconductor work at a very small scale?
technique: look up nanotechnology. same theory of semiconductors will hold: hyperphysics.phy-astr.gsu.edu/hbase/solids/band.html
15h
answered Doesn't the collisions of the particles in a gas affect the temperature of the gas?
21h
answered Do we know where newly formed quark-antiquark pairs come from in the process of hadronization?
1d
comment How to use quantized version of Maxwell equation in photonic entanglement experiment?
How old are you? what is your physics education?
2d
comment One photon and two electrons
"can a pair of distinct electrons emit in common a single photon?" electrons within a potential well cannot be "distinct", it is a single quantum mechanical solution giving the probability of observing one photon emitted while two electrons change energy levels. If the probability is not zero, it can happen.
2d
comment How to infer the wave function $\psi$ of a EM wave?
this is not a simple matter. duplicate maybe here physics.stackexchange.com/questions/437/… . a form is given here cft.edu.pl/~birula/publ/CQO7.pdf
2d
comment Why do particles have spins such as $1/2$, $3/2$, $5/2$?
@ChrisWhite the other question is not particularly about the half integer, so not exact duplicate?
2d
comment Why do particles have spins such as $1/2$, $3/2$, $5/2$?
Lets put it this way: physics is about observations/measurements and the mathematical theories that can fit the observations measurements. Generally to get a new theory come first observations that disagree with the established ones, then new theoretical models are suggested, predicting observations that had not yet been seen, then a new established theory is accepted because it was validated by the data. Intrinsic spins were an observed/measured anomaly for the first models of QM which disappeared with the postulation of intrinsic spin.
2d
comment Why do particles have spins such as $1/2$, $3/2$, $5/2$?
@RayKay from the experimental values of the experiments linked above. From measurements it was found that an intrinsic angular momentum should be assigned to electrons, for example, equal to 1/2*h_bar to fit the measurements.
2d
revised Why do particles have spins such as $1/2$, $3/2$, $5/2$?
added 97 characters in body
2d
answered Why do particles have spins such as $1/2$, $3/2$, $5/2$?
2d
answered Do unmeasured particles function the same as when measured?
2d
comment I open the fridge - do I let the heat in or the cold out?
Thermodynamics is not a matter of convention. It is an elegant mathematical theory that describes centuries of observations which has been shown to emerge from statistical mechanics and quantum statistical mechanics. Temperature emerges as proportional to the average kinetic energy of the constituent atoms/molecules in a gas. Its sign is not a convention.
2d
comment I open the fridge - do I let the heat in or the cold out?
This last has no meaning for physics.
2d
comment I open the fridge - do I let the heat in or the cold out?
There does not exist cold radiation. Radiation has a spectrum characterized by the temperature of the body emitting it and is always positive. Only in comparison one body has a higher or lower temperature.
2d
revised I open the fridge - do I let the heat in or the cold out?
link added to clarification
2d
answered I open the fridge - do I let the heat in or the cold out?
Jan
26
comment How much energy is needed to create an electron?
Yes, if you delve into the calculations that is the way it is solved. At conceptual level though the group structure assignment of charge ,+/- 1/3 and +/-2/3 for quarks and -1 for electron contain the problem at a postulated level.
Jan
25
comment Distribution and detection of dark matter
On Earth we expect that our experiments with particle physics will find new particles which will only,(or overwhelmingly) interact through their mass with gravitation . These will be candidates for dark matter constituents.
Jan
25
comment How much energy is needed to create an electron?
It is a classical physics based paper. The problem is "solved" in quantum physics by postulating the quantized nature of charge and charged elementary particles and ignoring the classical construction arguments. Similar to solving the 1/r potential problem with the quantized solutions of the Schrodinger equation, the r=0 is meaningless. In the standard model the charges are identified with the group representation parameters describing mathematically the set of particles ( observed experimentally).