68,548 reputation
348180
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location Greece
age 75
visits member for 4 years, 7 months
seen 2 hours ago

Retired experimental particle physicist.

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


2h
answered Is the cosmic microwave background radiation red shifted?
4h
answered How to determine the observables rigorously?
5h
answered With respect to the Casimir effect, why can't the wavelengths of the virtual particles between two plates just “pass through” the plates themselves?
13h
revised Quantum hadrodynamics
corrected reference as user left and the id was lost
13h
comment Quantum hadrodynamics
Sorry, it is not my field. Check in a library the link given by user74893 . It may have references to standard texts there.
17h
comment Why do people wear black in the Middle East?
You should give a link. The dress has to be very loose. Look at my answer here with some photos physics.stackexchange.com/…
21h
comment Why do electric shocks send you flying?
I was taught when working in the lab with electricity to approach any possible live wire with the back of the hand. That is because the body goes into spasm with electricity and if the finger are around the wire the spasm closes the hand and one cannot let go. Most of the effect is spasms from the body, not the energy of electricity , imo, though I have no links
1d
comment Could a civilisation contact us by laser from 50 light years away?
@AcidJazz nothing can go faster than light. higher frequency might allow for more information but not faster.
1d
comment Kayaking against the wind is faster than with wind in my back?
You could try an experiment with a buoy with a hanging weight that has some surface.
1d
comment Kayaking against the wind is faster than with wind in my back?
on the other side of the lake to what? perpendicular to what? Is there a river flowin in or aout? The currents follow contours of the sides and bottom and one would need a topology of the lake.
2d
comment Why don't photons split up into multiple lower energy versions of themselves?
The answer by dexter kim is relevant for collinear photons One needs an odd number of collinear photons, one to carry the spin of the incoming and two to cancel each other . For the non collinear case it is not important since energy and momentum violations do not allow it.
2d
answered Kayaking against the wind is faster than with wind in my back?
2d
comment Upsilon full decay width? (and reference request)
There is great interplay between theory and experimental measurement to extract widths, since they are convoluted with the accuracy of the measurements. Maybe reading this will help arxiv.org/pdf/hep-ex/0308020v1.pdf
2d
comment Photons have a property from the matter they interact with?
It is a theoretical statement; is it retrievable, should be the question. The photon did disturb the cones on the retina and the information of its existence was transferred, maybe of its energy if the color was noted , but spin and polarization information is dispersed as far as perception of one photon goes. As the other answer states, light emerging from zillions of photons is a different matter.
2d
answered Photons have a property from the matter they interact with?
2d
answered Why, fundamentally, are particles charged?
Sep
1
comment What is Quantum Mechanics really about?
I found the pdf for the lectures, page 81 :) cds.cern.ch/record/276704/files/CERN-64-13-V-3.pdf
Sep
1
comment What is Quantum Mechanics really about?
IMO it is the way that the many body problem is solved, that any quantum mechanical calculation on measurable quantities has to face to get at numbers (except simple potential well approximations). One writes the Feynman diagrams, follows the one to one rules for vertices and propagators and ends up with an integral which will give a number to compare with measurement.
Sep
1
awarded  quantum-spin
Sep
1
comment What is Quantum Mechanics really about?
I am an experimentalist. Way back in the 1960's I had the same problem as you. I was taking a field theory course following the book of Bogoliubov and became quite expert at working with creation and annihilation operators in solving exercises and quite bewildered with what that had to do with real physics. Then I went to the 1964 summer school of Physics of CERN where Veltman gave a series of lectures on how to calculate crossections using the creation and annihilation formalism, and the scales fell from my eyes :). Yes, the wavefunction formalism is underlying all those bras and kets.