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I'm a physics Ph.D student studying nonequilibrium quantum field theory with applications to phase transitions in the early universe. A particular application is baryogenesis: the question of why there more matter than antimatter in the universe.


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Nov
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reviewed Leave Closed Can a photon survive a collision? If so, is it at rest during the process?
Nov
2
reviewed Reopen Steady state of diffusion current in semiconductors
Nov
2
reviewed Reopen Why are we living in the $q$ part of the phase space?
Nov
2
reviewed Close Under what conditions a person can lift a car alone?
Nov
2
reviewed Close Determing time to complete known distance with constant acceleration
Nov
2
comment What if a probably non wave equation, satisfies the wave equation?
It is hard to tell what you are asking here. I think the first time you say "equation" you mean "function," and what do you mean by "Does it necessarily mean that it is a wave equation?" And what is a "potential wave"? A function of the form you describe obeys a certain kind of wave equation (describing waves with velocity $-a/b$), but whether it is physical or not depends entirely on the context of what you're trying to describe.
Nov
1
comment Is the “Doctor Who” spacetime affected by Hawking's chronology protection mechanism?
Note the paper [1] itself is completely classical. Your question is mentioned towards the end under "Questions for Future Consideration," along with other serious pathologies which would possibly (probably) turn up. Also the paper is not in a journal and has no cites on INSPIRE yet, so these would still be open questions. But everytime someone invents a metric that violates the energy conditions like this bad things invariably happen to it. I'm 99% certain this geometry will turn out to be semiclassically unstable.
Nov
1
comment Why isn't dark matter just matter?
@JohnFx and McGarnagle: At one time neutrinos would have seemed like a last ditch attempt to prop up an old theoretical idea (conservation of energy/momentum) that many at the time were actually considering giving up, despite a complete lack of positive evidence for their existence. Then they were found experimentally. Just because something looks vaguely like a previous episode from the history of science doesn't mean it will play out the same way. We are in new territory that hasn't been seen before. Only new experiments will settle the question once and for all.
Nov
1
comment How do we know Dark Matter is non baryonic?
If you have doubts about CDM (and we all do) it's far more constructive to propose a concrete alternative and try to constrain it. This is what has already been happening for years. If you actually read the literature it's not like nobody is talking about modified gravity or other such things. It's just not working as well as CDM (yet).
Nov
1
comment How do we know Dark Matter is non baryonic?
"If CDM existed as particles, they would have been found by now." Not necessarily true, as even a basic grasp of weak scale physics will tell you. Direct detection experiments are only just beginning to eat into the interesting parameter space of the usual models.
Oct
31
comment Reduction in gravity from photon exchange
There is no net energy decrease. The energy lost by the photons goes into increasing the kinetic energy of bodies (i.e., they absorb momentum and energy from the photons and accelerate away from each other).
Oct
31
comment Does someone falling into a black hole see the end of the universe?
@TerryBollinger It's a general fact of differential geometry that any two dimensional space is (locally) conformally flat, so if you suppress the angles and just look at the $r-t$ space you can always find a coordinate transformation that makes (radial) null rays 45 degree diagonals, and bring the metric to the form $\omega^2 (u,v)(-dv^2 + du^2) + r^2 (u,v) d\Omega_2^2$ for some suitable functions $\omega(u,v)$ and $r(u,v)$. Radial light rays becomes $v=\pm u+\text{const}$. You can't always do the same trick in $>2$ dimensions - too many degrees of freedom in the metric.
Oct
31
comment Does someone falling into a black hole see the end of the universe?
You may also be interested in Gullstrand–Painlevé coordinates which have a clearer physical interpretation than Kruskal-Szekeres in that they are adapted to a radially free-falling observer, but remain regular at the horizon. The price to pay is off diagonal terms in the metric.
Oct
30
comment Does someone falling into a black hole see the end of the universe?
Looks good!....