Recent content by klpskp

I found the source of my confusion: Of course all observers who are at rest with respect to each other can agree on the volume of a given object, because the metric allows them to agree on the length of spacetime intervals. Then the density is the mass of the object, divided by this common...

Unfortunately I still don't understand the answer, maybe I clarify my problem: Suppose we have observer 1, who is at rest relative to the fluid. Now suppose we have observer 2, whose worldline is the same as that of observer 1. In particular, observer 2 is also at rest relative to the fluid...

Dear Ordruin, what do you mean by physical density? I understand that we mean the density in some frame in which the fluid is at rest, i.e ##u^0=1## and ##u^i=0##. However, such a frame is not unique, the coordinate transformation from my original post takes one rest frame to another rest...

The energy momentum tensor of a perfect relativistic fluid is given by $$T^{\mu\nu} = (\rho + p)u^\mu u^\nu + p g^{\mu\nu}$$ I don't understand why this is a tensor, i.e. why it transforms properly under coordinate changes. ##u^\mu u^\nu## and ##g^{\mu\nu}## are tensors, so for ##T^{\mu\nu}##...

Suppose we have a classical system described by a Lagrangien \mathscr{L}(x,t). The same system can be described by the Lagrangien \mathscr{L'}(x,t)=\mathscr{L}(x,t)+\frac{\mathrm{d}F(x,t)}{\mathrm{d}t}. where F(x,t) can be any function. If we now quantize the system by calculating the...

Hello everyone, I was trying to develop a sort of generalized version of the Fourier Transform. My question in particular is: Given a function f(x,u), is there a function g(x,u) with \int_{-\infty}^\infty f(x,u)g(x,u')\mathrm{d}x=\delta(u-u') For f(x,u)=e^{2\pi ixu} the solution would be...

Suppose we have a Spin-1/2-Particle with no charge, like a Silver Atom, fixed at the origin. The magnetic dipole moment is \mathbf{\mu}=\gamma\mathbf{S}, where \gamma ist the gyromagnetic ration and \mathbf{S} is the spin angular momentum. The magnetic moment creates the magnetic field...

Hi everyone, I tried to find the Eigenstate of the angular momentum operator myself, more specifically I tried to find a Function Y_{lm}(\theta,\phi) with L_zY_{lm}=mħY_{lm} and L^2Y_{lm}=l(l+1)ħ^2Y_{lm} where L_z=-iħ\frac{\partial}{\partial \phi} and...