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location Princeton, NJ
age 25
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I am a graduate student studying astrophysics at Princeton. I received my bachelor's in physics and mathematics from Caltech (2011).

My primary interest is in general relativistic magnetohydrodynamics simulations of black hole accretion.


19h
comment Numerical eigenbasis for a unitary
For the record Computational Science might have been the best place to ask this originally.
1d
comment What is the average mass of galaxies according to Hubble Deep and Ultra Deep field observations?
@AbanobEbrahim Your (1) could be quite difficult. Where do you make the low-end cutoff? For a warmup, how many satellite galaxies orbit the Milky Way? This number was revised not long ago, and is still debated. And what is a galaxy anyway? Do you count globular clusters?
1d
comment What is the temperature of the clear night sky from the surface of Earth?
Indeed, "2K73" could reasonably be untypod to "273 K" or "2.73 K." I never before realized how close the freezing point of water was to 100 times the CMB temperature.
1d
comment What is the most compelling evidence of General Relativity in the presence of matter and energy?
@Bridgeburners Wikipedia has a derivation. As for getting masses and radii for the same objects -- that has proven rather difficult. There aren't any particularly good datapoints in that parameter space... yet. Also, predictions for such data points are influenced not only by pure GR, but also by your assumed equation of state.
1d
comment What is the most compelling evidence of General Relativity in the presence of matter and energy?
Good question, not a duplicate, and as the OP is right to note all suggestions in the comments are tests only of the vacuum field equation.
2d
comment Relativistic Kill Vehicle
Obligatory xkcd: what-if.xkcd.com/1
Dec
14
comment How can we be Certain that Dark Matter Exists if we Cannot See it or Directly Detect It?
I feel like this should be a duplicate of something, but not the linked question. In fact, almost none of the evidence we have for dark matter comes from our own galaxy.
Dec
14
comment What does this stellar mass distribution mean?
This agrees with my comments on the question, where I used Chabrier for the high-mass end.
Dec
14
comment What does this stellar mass distribution mean?
Similar with 8+ $M_\odot$ stars (if these are what your diagram calls "supergiants"): Chabrier says out of 1+ $M_\odot$ stars they should be 0.03% by number, 0.3% by mass, and your diagram has them at 3%. Again, Chabrier is way off from your diagram, but the mass interpretation is less off. It's also entirely possible I'm making a computational mistake...
Dec
14
comment What does this stellar mass distribution mean?
Hmm... Two answers say numbers, but the numbers I gave in answering another question of yours don't agree. For example, the PDMF I gave predicts (number of 1-2 $M_\odot$ stars) / (number of 1+ $M_\odot$) stars to be 95%, while it predicts the same ratio but for mass to be 90%. The figure you have has the fraction at 66%, more in line with the mass interpretation. I'm reluctant to make this an answer, though, without a source that extends the PDMF below 1 $M_\odot$.
Dec
13
comment Where did the energy released due to gravitational binding energy of the Earth go?
Not that this helps, but Wikipedia claims the binding energy is actually more like $2.5\times10^{32}\ \mathrm{J}$. (A centrally concentrated distribution will always be more bound than a uniform sphere.) I can confirm that I get the same answer numerically integrating the model given in the referenced paper.
Dec
13
comment Where did the energy released due to gravitational binding energy of the Earth go?
"the current internal energy contributes positive mass-energy to the Earth" -- sure, but since the rest-mass energy of Earth is over $5\times10^{41}\ \mathrm{J}$, I'd say this is pretty negligible.
Dec
13
comment Solar spectrum units
Something to ponder: what would the area under the curve represent in the two cases? (Hint: only one case makes any sense.)
Dec
13
comment Greiner or Landau for Math major student?
Are you looking to understand physical principles, or are you looking to have exposure to useful equations in physics? These are different things.
Dec
12
comment Would it be possible to “recycle” nuclear warheads into nuclear energy?
The world isn't powered by nuclear energy because (1) people are ignorantly afraid of the safest power source known to humanity, and (2) it's not overwhelmingly price competitive to operate nuclear plants as opposed to other plants. The availability of fuel has little to do with the politics and economics of the situation, especially since there's plenty of fuel that doesn't come from nation-states voluntarily surrendering their military investment.
Dec
12
comment How would night sky look like if the speed of light was infinite?
@pentane solid angle goes down as the square, which is what Tim S. surely meant.
Dec
12
comment How would night sky look like if the speed of light was infinite?
@Peteris Opaque things would block light, but then they would heat up until they were the same temperature as stellar surfaces and thus they would glow just as bright. In such a universe opaque objects essentially delay the inevitable, slowing down the effective speed of light (even if it is infinite otherwise). So I'm assuming either the age of the universe is larger than the thermal equilibrium time, or simply that we refer to the effective $c$ when we say it is infinite.
Dec
12
comment How would night sky look like if the speed of light was infinite?
@DavidRose It doesn't. The two bullets together are necessary and sufficient for Olbers paradox to manifest. The speed of light only enters the second bullet.
Dec
12
comment How would night sky look like if the speed of light was infinite?
@RobJeffries I don't think that's really even a valid question. Of course no "actual" physics works with infinite $c$. For any scenario, I can find a reference frame where finite $c$ and infinite $c$ differ arbitrarily much in their predictions. But at the same time, we don't tell students "don't bother with classical mechanics, since the errors in your results are unboundedly large in appropriately chosen formulations of the problem." Exploring the implications of a working theory that doesn't try to consistently explain everything in the universe is still physics.
Dec
12
comment How would night sky look like if the speed of light was infinite?
To everyone voting to close as non-mainstream, I remind that this is exactly the cosmology of Newton's time.