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Apr
3
comment Mass-energy conversion mechanism in supernovas
I see. My question was related to the underlying mechanism, I know that gravitational collapse is what provides the energy/density/pressure/temperature for it to happen. Do we know what pressures/temperatures are required to trigger this unknown mechanism?
Apr
3
comment Mass-energy conversion mechanism in supernovas
where do I get 1% of neutrino absorption? from that same article: "A process that is not clearly understood is necessary to allow the outer layers of the core to reabsorb around $10^{44}$ joules[78] (1 foe) from the neutrino pulse, producing the visible explosion, although there are also other theories on how to power the explosion.[75]"
Apr
3
comment Mass-energy conversion mechanism in supernovas
the wiki article: (en.wikipedia.org/wiki/Supernova#Core_collapse) says that up to 10% of the rest-mass is converted during core collapse, but still 5% is 5 times more than nuclear fusion. Although if only 1% of that 5% energy in form of neutrinos interacts with matter and electromagnetism, so only $5 \times 10^{-4}$ of the star's mass is used to build heavy isotopes and power the explosion, it seems quite a low number
Apr
3
asked Mass-energy conversion mechanism in supernovas
Mar
16
awarded  Notable Question
Feb
16
comment What makes General Relativity conformal variant?
notice that I did not say 'conformal transformation in 3+1', what I was suggesting is a coordinate transformation that only changes two coordinates out of 4, with a Weyl rescaling
Feb
16
comment What makes General Relativity conformal variant?
when you say on two dimensions, does this include coordinate transformations in Minkowski space (3+1) that leave two coordinates invariant?
Feb
16
accepted Are diffeomorphisms a proper subgroup of conformal transformations?
Feb
13
comment How can laser interferometry be used to measure path difference smaller than wavelength of laser light?
not $10^{-22}$ meters, but $10^{-22} L$ with $L$ total arm length, including all round trips
Dec
29
awarded  Popular Question
Dec
24
comment Proof that fixed points of a null field are zero
I should add that the DC term of the Fourier expansion must be zero, since to synthetise a finite waveform with the Kirchhoff theorem, you need nonzero frequencies
Dec
22
comment Proof that fixed points of a null field are zero
I thought about it, but since it is related to holophony and wavefield synthesis, I thought it would find more expertise on Physics.SE
Dec
19
revised Proof that fixed points of a null field are zero
added 226 characters in body
Dec
19
revised Proof that fixed points of a null field are zero
added 65 characters in body
Dec
19
asked Proof that fixed points of a null field are zero
Dec
16
awarded  Popular Question
Dec
8
comment Why does no physical energy-momentum tensor exist for the gravitational field?
put in other words, to compute the energy carried by a gravitational wave, the energy depends on the shape of the gravitational wave in the whole compact support of the metric perturbation. However, this dependence cannot be put as a simple spacetime integral over a density. The question would be: over what variables must be integrated what, in order to obtain the non-local energy of the wave?
Dec
6
accepted Null geodesic equations
Dec
5
comment Null geodesic equations
I made an edit, please review. Also, when you say "Moreover the null vector $\dot{\gamma}$ must be proportional to either $n_+$ or $n_-$." I think this is the part that I cannot follow. In the $xt$ plane, the $n_+$ would be $(-1,1,0,0)$ and $n_-$ would be $(-1,-1,0,0)$. The step (B) does not seem to be giving much information, since both the colineal component along $\dot{\gamma}$ and the orthogonal component $n_-$ will satisfy $g(n_- , \dot{\gamma})=0$. So is still possible for $\nabla_{\dot{\gamma}}\dot{\gamma}$ to have non-zero components along both directions
Dec
5
suggested rejected edit on Null geodesic equations