4,738 reputation
1527
bio website sites.google.com/site/…
location Cambridge, MA
age 26
visits member for 2 years, 7 months
seen 4 hours ago

Physics Graduate student at Harvard University.


4h
comment Computing the Ricci Tensor for a Spherically Symmetric Spacetime
This link might be of help - arxiv.org/abs/gr-qc/9602015
8h
comment If angular momentum is conserved, what's wrong with this scenario?
What about the torque from the sun?
15h
reviewed Approve suggested edit on What is (meant by) a non-compact $U(1)$ Lie group?
15h
reviewed Close Existence of a statistical biophysics study? (In Fitzhugh Nagumo diffusion system with non linear waves)
15h
reviewed Close Why are Rainbows always seen Horizontally or from Sideways?
15h
reviewed Close Wave Equation Variables and Interpretation
1d
reviewed Close Why aren't there spherical galaxies?
1d
reviewed Close Radially free falling observer
1d
reviewed Approve suggested edit on Why does the Sun always rise in the East?
1d
reviewed Close Finding the potential between two spherical shells
2d
comment 2 questions on 4-velocity
Let us continue this discussion in chat.
2d
comment 2 questions on 4-velocity
The correct formula is $\frac{dt}{d\tau} = \gamma$. It is most easily derived from the metric $c^2 d\tau^2 = c^2 dt^2 - d\vec{x}^2 = ( c^2 - v^2 ) dt^2$. This gives you the formula that you are looking for.
2d
comment 2 questions on 4-velocity
I presume you derived $t = \tau \gamma$ as the time-dilation formula. That formula relates the time measured in two frames and is therefore valid only for constant $v$.
2d
comment 2 questions on 4-velocity
Yes, but you have to be careful which $\gamma$ they are using. In special relativity, one talks about inertial frames and objects. Inertial frames have a constant velocity $v$ implying that their $\gamma$ is constant. Objects can have any $v$ and for them the $\gamma$ is not constant.
2d
comment Why aren't purely Dirac neutrinos ruled out?
The problem is that particles interact only with the left-handed component of the neutrino. Since interactions are the only way to "see" or measure particles, independent of whether neutrinos are Dirac or Majorana, only the left-handed component can be measured. Thus, nothing can be ruled out based on this data.
2d
comment 2 questions on 4-velocity
In special relativity, $\gamma = \frac{1}{\sqrt{1-v^2/c^2}}$ which is a constant, since we only consider inertial frames (which have constant $v$). In general relativity, $\frac{dt}{d\tau}$ is no longer equal to $\gamma$, but is more complicated and in general is not constant.
2d
comment Is $E^2=(mc^2)^2+(pc)^2$ correct, or is $E=mc^2$ the correct one?
I've used the equation $m = \gamma m_0$ which was written down before. Apart from that, the $p=mv$ part is the definition of momentum. Is that what you wanted clarified?
Nov
23
reviewed Approve suggested edit on Eigenvalues of Angular Momentum in Quantum Mechanics
Nov
23
reviewed Approve suggested edit on Do entangled particles lose entanglement after polarizing filters?
Nov
23
reviewed Leave Closed Hypothetical “superluminal cables”: discussion of the concept itself