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location Greece
age 74
visits member for 3 years, 7 months
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Retired experimental particle physicist.

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


8h
comment Does a high energy photon experience deceleration or direction-change when it impinge into water or something due to the change of refraction index?
since this came up to front again, I have to note that the photons are not absorbed and re-emitted. Absorption is a quantum effect for a photon. It either gives up all its energy and disappears, and if a photon is re emitted it will have a 2 pi angle to decay into, so the phases will be lost, or it scatters with the various ways photons can scatter elastically or inelastically.
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revised Can I throw a stone through my window without breaking the glass?
added 406 characters in body
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answered Can I throw a stone through my window without breaking the glass?
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comment How Exactly Does Linear Regge Trajectories Imply Stability?
thanks . you mean it is a second level string theory validation, validation by embedding more limited theories that themselves are validated by data. i.e. no direct line string theory which has not already been predicted by the minor ones. :(
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comment How Exactly Does Linear Regge Trajectories Imply Stability?
Ron, I was looking up strings and regge trajectories an this old question of yours came up.There have been some discussions of validation of string theory and I have been wondering whether you have unearthed any "predictions", checkable with the plethora of resonance data, that a string theory could give.
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comment What experiment would prove string theory?
I have been thinking if we could look at HEP data again in the framework of Regge trajectory exchanges we could get another handle on checking strings. It was fairly successful in describing resonances and the data arising from them. This would be another test then.
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revised Is the Big Bang defined as before or after Inflation?
clarification after comments
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comment Is the Big Bang defined as before or after Inflation?
classical BB. It will still emerge and apply at its region of validity . The various definitions you state are due to this confusion of trying to keep both the classical and QM frame at once .
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comment Is the Big Bang defined as before or after Inflation?
We actually live our everyday lives in a classical physics framework. That it is emergent and the underlying framework is quantum mechanical does not invalidate the theoretical models that describe so successfully our classical experience. It just limits their region of validity. The Big Bang model is successful in its region of validity and it is modeled as if there is a singularity at the very beginning. When the limits of the validity of classical GR are reached then QM has to be invoked and the data modeled with it, which is what the inflationary model does. That does not invalidate the
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comment Is the Big Bang defined as before or after Inflation?
@innisfree I am not talking about mysteries of quantum gravity. I am talking of mixing two frameworks that have different postulates and axioms and expect consistency. Generally in quantum mechanics singularities disappear. The classical frame is an emergent frame. When one is actually "handwaving" , mixing two frames, confusions will arise.
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awarded  Nice Answer
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answered Is the Big Bang defined as before or after Inflation?
Aug
27
comment How do you add temperatures?
I am curious, why do you want to add temperatures? To get an average temperature for a location?
Aug
27
comment How can blackbody radition be explained by quantization?
Funny. The black body spectrum IS electromagnetic radiation. Those oscillators ARE charged. What you are saying is a parallel projection of similar solutions for non existent matter. Mathematics that is.
Aug
26
answered Why should any physicist know, to some degree, experimental physics?
Aug
26
comment Why should any physicist know, to some degree, experimental physics?
I take exception with your " It has thus far turned out impossible to come up with a way to test string theory " . String theory is not developed in a vacuum, as mathematical toy. It is being tested for consistency with quantum field theory, the standard model, gravitational theories. It is a higher order theory whose experimental test ground are the lower theories that have been validated to date. It predicts supersymmetry, and this remains to be tested. The large extra dimensions model has not been validated at the LHC energies, but it was a string model that can be checked for validation.
Aug
26
answered The need for a 'particle description' of electrons
Aug
25
answered If atoms have specific energy levels, why do opaque solids absorb all visible light, not just some?
Aug
25
comment Photons to Represent a Wave
@firtree "Photons can be considered waves even if they don't make the classical wave" Important to stress they are Probability waves, not energy-intensity-in-space waves that the classical EM wave is (Poynting vector). The individual probabilities of the photons synergistically create the classical wave front with its phases in space.
Aug
25
comment Photons to Represent a Wave
@Anthony A classial wave composed by agreat number of photons can all be abosorbed impinging on a medium . There would be no reflection and the medium would look totaly blac. Evidently there must have been as many photon-atom interactions as there were photons. As matter consists of order 10^23 molecules per mole this is not impossible to happen, though most of the time there will be some reflection. The photon molecule interactions can be of various types and would be the content of another question.