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visits member for 2 years, 4 months
seen Jul 9 at 14:51

Mar
29
comment Is space unending?
It is possible to describe a sphere intrinsically, without thinking of it as embedded in three dimensional space. Perhaps a better example would be the torus: The game world of some arcade video games like snake has that shape: If you leave the screen on one side, you reappear on the other side. This gives the example of a finite but unbounded two dimensional space.
Mar
10
awarded  Yearling
Dec
19
answered Is there a simple way to compute some physical constant from Feynman diagram statistics?
Dec
6
answered Why is the world sheet of an open string a cylinder?
Dec
3
answered Why do we study the scalar field in QFT when there is no such thing in nature?
Nov
30
awarded  Caucus
Nov
24
awarded  Scholar
Nov
24
accepted Spectrum of Free Strings
Oct
29
answered Is it possible to recover Classical Mechanics from Schrödinger's equation?
Oct
10
answered Differences between the gravitational constants $G$ and $g$?
Sep
6
comment Why is the $\langle v_{x}^{2} \rangle=\frac{1}{3} \langle v^2 \rangle$?
Generally $\langle A + B \rangle = \langle A \rangle + \langle B \rangle$, this is more or less build into the setup. After all expectation values are computed by evaluating certain sums or integrals.
Jul
27
comment Can physics get rid of the continuum?
@RonMaimon You are right, I am not terribly satisfied with my answer myself. The idea I tried to convey was that numerical analysis has been very successful in simulating classical physics, because they deal with differentiable functions, those functions look boring locally and differential equations can therefore be discretized successfully. The "therefore" sweeps the whole field of numerical analysis under the rug and you are right that there are many subtle problems, energy conservation for example.
Jul
26
comment Can physics get rid of the continuum?
@NickKidman I modified the last sentence, hopefully that is not bad form.
Jul
26
revised Can physics get rid of the continuum?
deleted 35 characters in body
Jul
26
answered Can physics get rid of the continuum?
Jul
6
comment Why is ${\partial^i}{\partial_i\phi}$ = ${\partial^i {\phi}}{\partial_i{\phi}}$?
Where did you see that? One thing you can do is partial integration, but then you are missing at least one $\phi$. In deriving the Euler-Lagrange equations, you use partial integration.
Jul
1
comment What is Supersymmetry (SuSy)?
Each of those terms have a rather technical meaning. To explain them usually takes several lectures each, at least. That you ask about them in one question indicates that you have no, or little prior knowledge. I think you should at least indicate why you are interested in those questions.
Jun
27
comment Snooker/billiards cueing
@CaptainGiraffe Sommerfeld treats side queing in his Lectures on Mechanics, if I remember correctly. He certainly treats unver/over cueing.
Jun
27
answered Exercise QFT and CFT
Jun
26
revised What's the distinctions between Yang-Mills theory and QCD?
edited body