1,526 reputation
1713
bio website code.google.com/p/notebk
location Los Angeles, CA
age
visits member for 3 years
seen 11 mins ago

A mathematician, a programmer, etc. etc.

My interests are limited to classical general relativity, quantum gravity, mathematical aspects of quantum field theory, and related fields.


May
18
awarded  Yearling
May
9
comment One-body General Relativity
"However, I have not looked deeply into the case of the 1 body gravitational problem myself." Google Schwaraschild metric...
Apr
19
comment Phenomena in the intersection of general relativity and quantum mechanics
You mean, something like this?
Apr
9
answered What does the “UV” in “UV completion” stand for?
Apr
1
comment Covariance of the Dirac Equation
Well, also remember that if $S_{\mu\nu}$ is symmetric and $A^{\mu\nu}$ is antisymmetric, then $A^{\mu\nu}S_{\mu\nu}=0$ identically...which should simplify considering $\omega_{\mu\nu}[\gamma^{\mu},\gamma^{\nu}]$ if you plug in the metric tensor plus term quadratic in $\gamma$...recalling that the metric tensor is symmetric...and $\omega$ antisymmetric...
Mar
31
comment Formulating a symplectic integrator for a non-local Hamiltonian
I had an answer which I realized was irrelevant; the problem appears to be that you have a field theory and do not realize it. (Hence why functional derivatives are used, the Hamiltonian is an integral expression, etc.)
Mar
12
comment Kerr metric Christoffel symbols
Two thoughts: (i) take the $J\to0$ limit should recover the Schwarzschild results, (ii) Exact Solutions of Einstein's Field Equations should contain the relevant information, if I recall correctly...
Feb
10
comment Propagator for massless spin 2 particle
Something like this?
Jan
24
comment Why does $\frac{d\tau}{d\sigma} = L$?
@Prahar well, $\mathrm{d}\tau = -g_{\mu\nu}(x)\mathrm{d}x^{\mu}\,\mathrm{d}x^{\nu}$, you jumped a step (parametrizing $x^{\mu}=x^{\mu}(\sigma)$)...
Jan
16
answered Is it in general true that $\nabla_\mu T^{\mu\nu}=0$ implies the matter equations of motion?
Jan
15
comment What besides the metric do you need to set up the EFEs and the geodesic equation?
Fun fact: for electrically charged dust, the conservation of the stress-energy tensor gives the Lorentz force law in curved space.
Jan
10
comment What is the largest subgroup of the Galilean group and the Lorentz group?
Well, can you show the Euclidean group is a subgroup of both the Lorentz and Galilean groups? Can you show time translation is also a subgroup? Is there any other subgroup they both have in common?
Jan
10
comment QFT question, scalar field and so on
Huh, funny, at Caltech there's a homework problem that looks almost exactly like this for Mark Wise's class...you wouldn't happen to be in it, @Henry, would you?
Jan
2
revised What's wrong with the square root version of the Klein-Gordon equation?
Added some references
Jan
2
comment What's wrong with the square root version of the Klein-Gordon equation?
@CuriousOne, "they say" the functional Schrodinger equation is useful for certain perturbative calculations, but -- as you hint -- its usefulness may be dubious (see, e.g., Brian Hatfield's Quantum Field Theory of Point Particles and Strings chapter on the functional Schrodinger picture for when it's useful in perturbative calculations).
Jan
2
comment What's wrong with the square root version of the Klein-Gordon equation?
@Nick, in some sense, I suppose you could think of the unitary time evolution as "nonlocal in time" relating the state at time $t_{0}$ with the state at time $t+t_{0}$. This is not terrible, it's allowed by physics. The problem is when you have nonlocality violate the condition $[\varphi(\mathbf{x}), \varphi(\mathbf{y})]=0$ for spacelike $\mathbf{x}$, $\mathbf{y}$.
Jan
2
answered What's wrong with the square root version of the Klein-Gordon equation?
Dec
30
comment Determining the geometry of the phase space of a system
I'm just rather shocked to hear it for mechanical systems. I know in $2+1$-dimensional GR, for example, you can end up with a phase space that's non-Hausdorff...but I assumed it was always just field theories that had such peculiarities. (I may be mistaken, which is why I ask about such things)
Dec
30
comment Determining the geometry of the phase space of a system
Wait, don't you mean $\Gamma$ IS Hausdorff? A non-Hausdorff phase space would be problematical...
Dec
28
comment In Quantum mechanics, what is realism?
@CuriousOne I'm not going to debate you on something you're clearly emotional about; although it is amusingly ironic, you appeal to philosophy (Popper's criteria for science) to pathologically decry philosophy. Since you cannot rationally form a coherent position, nor are you contributing anything constructive to the question, perhaps you should just get off your soap box and stop...yes yes, you believe interpretations of QM should belong to philosophy, blah blah, duly noted.