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A duck walks into a bar. Animal control is promptly called and the duck is released into a near by park.


Mar
12
comment Can Somebody give me Questions
You misinterpreted the Q&A concept.
Mar
10
comment Why quantising gravity necessarily give us gravitons?
Do you know if there is any hypotetical way of tweaking the spin degrees of freedom and make the graviton a fermion? Are there physical arguments against that?
Mar
9
revised Tensor product of Hadamard Operators
suggestion to make it parsable
Mar
9
suggested suggested edit on Tensor product of Hadamard Operators
Mar
8
revised What is an effective and efficient way to read research papers?
added 134 characters in body
Mar
8
answered What is an effective and efficient way to read research papers?
Mar
7
comment How to find different operator representations in QM?
@DepeHb: i.imgur.com/IchgG0c.png Momentum is that which is conserved if you translate the system. Turns out the operator $T_d$ which shifts a function $f(x)$ by $d$ can be written as $\exp\left(i\hbar\,d\,\left(\frac{1}{i\hbar}\frac{\partial}{\partial x}\right)\right)$. The generator is the momentum operator $\propto\frac{\partial}{\partial x}$ and so as function of $x$, the eigenstates $\left|p\right\rangle$ of that operator must be $\mathrm{e}^{cpx}$.
Mar
7
revised Naive visualization of space-time curvature
added 5 characters in body
Mar
7
comment Naive visualization of space-time curvature
@StanLiou: Then you are assuming you can explain the notion of a local interial frame to a layman.
Mar
7
answered Naive visualization of space-time curvature
Mar
5
answered Do Dirac Gamma Matrices act like Tensors?
Mar
5
comment Is there a limit to acceleration?
@Carterini: Not that a factor of 2 is of any relevance if we're already speaking of $10^{51}$, but no, $2.2$ is the value you get if you plug in "(speed of light)^(7/2)/((Plancks constant)*(Gravitational constant))^(1/2)" into wolframapha and so here I bet against your back of the envelope calculuation. And I say it again, I'd just sit down and see how fast momentum can translate between two particles, say with a $\left|r_1(t)-r_2(t)\right|^{-2}$.
Mar
4
comment Is there a limit to acceleration?
Afaik, there is no slogan about maximal acceleration. You could cook up a Planckian acceleration $c^{3.5}/(\hbar G)^{0.5}\approx 2.2\,10^{51}m^2/s$, but I don't see the use for that here. Seems the latter must ask for r'' vs. W. We should maybe make it a little more concrete. Consider a particle at rest with $r_1=0$ at some time and set up a potential $V(|r_1-r_2|)$ with another particle. You can consider a) a free collision (where total momentum is constant) and compute $r_1''(t)$. b) try to compute the energy cost it takes to move the second particle in some way to push the other one.
Feb
27
revised Group of translations in two dimensions - A weird treatment
check it out
Feb
27
suggested suggested edit on Group of translations in two dimensions - A weird treatment
Feb
27
comment What's the real fundamental definition of energy?
...and call this the Lagrangian, for the map $t\mapsto q(t)$ it should read action there, alternatively you can speak about the image of that map.
Feb
26
comment Why do we use $\psi$ instead of a straightforward probability?
This thread should answer the question.
Feb
25
comment Quantum frequency vs classical frequency and Energy dependence
From the point of view that a QFT starts by setting up the states and the Hamiltonian $H\sim \nu\ a^Ta$, the QED energy is given like this and is responsible for both of course $\nu$'s. I.e. $\langle H\rangle\propto \nu$ and "$\mathrm{e}^{-itH}\sim>\sin{(t\nu)}$".
Feb
24
comment Discrete sum over a gaussian function
@EmilioPisanty: ListPlot3D
Feb
24
revised Discrete sum over a gaussian function
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