34,556 reputation
347119
bio website inspirehep.net/…
location Duchy of Grand Fenwick
age 43
visits member for 3 years, 11 months
seen 2 hours ago

Experimental nuclear and particle physicist. These days I'm teaching, but I've spent a lot of time on nucleon structure in fixed target electron scattering and neutrino oscillations using reactors and beam sources.


Feb
26
revised Can low temperature plasma exist?
Fix speling in the title
Feb
25
comment How can we know the time frames for events in the early universe?
The short--short version is that particle physicists have measured the physics that applies under certain temperature and density conditions and can extrapolate to a certain degree and then you can just roll the physics backward. How far back you can go depends on exactly what theories you trust, but we can certainly go back to the weak freeze out (temperatures around the Z mass) and can say something about the physics of quark--gluon plasmas.
Feb
25
comment EPR-type experiments and faster-than-light communication using interference effects as signaling mechanism
That example is incomplete. You have to describe the whole experiment. What would you do to each particle and how would you arrange the timing (and from what POV)?
Feb
25
comment EPR-type experiments and faster-than-light communication using interference effects as signaling mechanism
@user1247 There is no point in waving your hands at a vaguely described situation. Like Luboš said "You would have to describe your experiment in detail if you wanted the interference and its disappearance to be discussed seriously": you have to tell us what measurements you propose in order to analyze the situation.
Feb
25
reviewed Approve suggested edit on Crystal magnetic response only skin deep?
Feb
24
comment Surely space-time Curvature does not explain gravity, it just describe its effects?
Physics often offers answers to "how" or "why" questions, but those come when we find a more fundamental underling theory. Following a chain of "Why?"s will eventually lead to a answer in the form of "Because that is the observed behavior of the universe." Later on, a new theory could replace that with a more detailed answer, but then you can ask why the new theory and the answer will be "Because the world works that way." At the lowest level physics is descriptive. Finding those more fundamental theories is what we do, but don't kid yourself about there being a final insight there.
Feb
24
revised Light coming from a object travelling at speed of light?
fix wrong sized brackets, use \tag{} for equation labels
Feb
24
comment Can a black hole collapse in itself?
To decay "quickly" by the Hawkings process an black hole would have to have a mass around that of a smallish asteroid. One with a more than a solar mass would not be in any danger of going away any time soon, and in any case that process would not be described as "collapse".
Feb
23
comment Strong decays of baryons via quark-antiquark pairs
BTW The quark masses you are using there are for the "constituent quark" model, which is a very rough approximation. The real quark masses are known to make up a very small fraction of the baryon mass (up and down each less than 10 MeV) the rest being binding energy. That doesn't make the constituent quark model bad, but you should probably say when you are using it.
Feb
23
comment Faster than the speed of light and future travel
"Ye he will burn out" It is not clear what "burn out" is means here, but high relative velocity in and of itself has no biological effect whatsoever; that is implicit in the principle of relativity. Now high speed relative the local interstellar medium will require shielding as would very high speeds relative the CMB.
Feb
23
revised Where do electrons get the energy to remain in orbit?
edited tags
Feb
23
comment Faster than the speed of light and future travel
At the moment this question is suffering from at least two bad premises. Also, we've done pop-sci level faster than light questions before. And pop-sci level nearly as fast as light questions. See the "Linked" sidebar on physics.stackexchange.com/questions/7446/…
Feb
22
revised Does a Photon leave trace in a silicon tracker?
added 133 characters in body
Feb
22
comment Strong decays of baryons via quark-antiquark pairs
The proposed decay lost a up and gained a strange. Flavor change (and the consequent change of charge) indicates a weak interaction as well as the pair production (and what became of the W?). Are you sure that's what you mean?
Feb
22
answered Does a Photon leave trace in a silicon tracker?
Feb
22
comment Does gravitational redshift imply gravitation time dilation?
"The EEP is used to justify that if an observer on the ground shoots a beam of light towards a tower, then when the light reaches the tower, it will be red shifted." This phenomenon has also been measured. The first time in 1959.
Feb
22
answered What is the highest speed time dilation has been tested?
Feb
22
comment What is the highest speed time dilation has been tested?
Despite the lower energy (only 45 GeV per beam) LEP holds the beam speed record with a $\gamma$ on order of 200000 in the same tunnel as the LHC. Unless you want to count neutrino beams, but their speeds have not actually been measured to the precision needed to assign a $\gamma$.
Feb
22
comment Why must the eigenvalue of the number operator be an integer?
You should not say "energy eigenvalue of the number operator", the energy eigenvalue is associated with the energy operator. You just want "eigenvalue of the number operator" of "number eigenvalue".
Feb
21
revised Is the speed of sound almost as high as the speed of light in neutron stars?
fix a latex error, put the units in roman type