1,188 reputation
139
bio website
location
age
visits member for 2 years, 9 months
seen yesterday

Aug
27
comment Euclidean derivation of the black hole temperature; conical singularities
G. F. R. Ellis and B. G. Schmidt. Singular space-times. General Relativity and Gravitation, 8(11):915, 1977 has more details about conical (conelike) singularities.
Jul
30
comment Gedanken experiment: Does it collapse to a black hole or not?
The mass of a Schwarzschild black hole depends on the force exerted on a test particle at infinity, which does not change in your example.
Jul
16
comment Why does locking the rear tires on a vehicle cause it to spin?
When the tyres lock, static friction decreases significantly. This is the reason cars have ABS.
Jul
15
comment Are (active vs. passive) and (covariant vs. contravariant) related?
Active/passive transformation is related to whether we effect a change on the function and preserve the coordinate system, as opposed to the change on the coordinate system, while the function remains the same. A tensor can be covariant or contravariant regardless of whether the transformation is active or not.
Jul
12
comment Generalised velocities enough to be deterministic in Lagrangian mechanics?
Where does the dependence of $\ddot{q}$ on $(q, \dot{q})$ come from? This is not valid in the general case.
Jul
8
comment Classical models with unbounded particle number
The Boltzmann equation is about the distribution of particles in phase space. It allows for different kinds of particles that change from one form into another, which implies particle creation and destruction. It has applications in plasma physics.
Jun
20
comment How do you take the derivative with respect to a rank two tensor?
Every index combination indicates a different function. The derivative of a function w.r.t another functionally independent function, which is the case for functions with different indices, is zero and the only non-zero case is when the function to be derived and the one to be derived with are the same.
Jun
11
comment Is there a scientific term for the right-hand-(grip-)rule?
This is known as orientation. There are two orientations depending on the order of the basis vectors and only one of them can be used to define the volume element with positive sign.
May
10
comment If the electrostatic potential is zero, why doesn't the electric field have to be zero?
Do you mean $V$ is zero identically or that there's a value of $\vec{x}$, so that $V=0$?
May
7
revised Why more Fe-56 than Ni-62 as fusion product in heavy stars?
deleted 5 characters in body
May
7
revised Why more Fe-56 than Ni-62 as fusion product in heavy stars?
added 181 characters in body
May
6
answered Why more Fe-56 than Ni-62 as fusion product in heavy stars?
Apr
26
awarded  Nice Answer
Apr
6
awarded  Tumbleweed
Mar
30
revised Ernst potential from Kaluza-Klein reduction of axisymmetric space-time
added 126 characters in body
Mar
30
asked Ernst potential from Kaluza-Klein reduction of axisymmetric space-time
Nov
23
awarded  Yearling
Oct
27
comment Why to write the Navier-Stokes equation with dimensionless quantities?
Dimensionless quantities make it easier to define scales in some cases, such as this one, which allows us to derive physical meaning more easily. Also, they are especially suited for numerical simulations if the quantities have extreme values, because fast computer arithmetic has finite precision.
Oct
18
revised Why does gravitational collapse occur suddenly in a supernova progenitor?
edited body
Oct
18
comment Why does gravitational collapse occur suddenly in a supernova progenitor?
I'm not arguing whether electron degeneracy is essential for stellar equilibrium or not, I'm just claiming that one needs to decide at what depth to extend an answer and assume certain knowledge by the OP, otherwise answering becomes a very time-consuming process. The core consists of Fe mainly (not Ni), because it has the maximum binding energy per nucleon. The model with a second shock wave is known as delayed hydrodynamic explosion. You're right about the free-fall time-scale; what I wrote is correct about the outer layers of the core.