All Questions

50 views

Lorentz Transformations in Minkowski space

If $\Lambda$ represents the Lorentz transformation matrix, then the transformation of contravariant components $x^\mu$ is given by $$x'^\mu=\Lambda^{\mu}{}_{\nu} x^\nu$$ and that of the covariant ...
198 views

Hidden momentum

I'm trying to learn about hidden momentum. After reading what I could find with a google search, I understand that it is equal to the momentum carried by radiation, calculated with the Poynting vector....
166 views

Why we do calculus of variation instead of finding maxima or miniama of function? [on hold]

Why we do calculus of variation instead of finding maxima or minima of function? What is the difference between finding maxima or mimima i.e. critical point of a function and calculus of variation?
29 views

34 views

“Simple” air resistance question

Two balls with exactly the same size and shape, but different mass, are launched at the same velocity 90 degrees to a flat plane. When air resistance is considered, the object with the larger mass ...
55 views

Two qubits system in polar co-ordinates

I know that I can write a single qubit state in terms of polar co-ordinates $(r,\theta,\phi)$ on a Bloch sphere. \rho = \begin{pmatrix} \frac{1+r \cos\theta}{2} &\frac{r \exp(-i\...
226 views

Tight binding Hamiltonian for 2D finite dimensional lattice and nanowire

The Hamiltonian of a 1D lattice having finite $N$ atoms, (if we consider one basis per atom) is given by the following $N\times N$ matrix- Here $E$ is the onsite energy and $t$ is the hopping ...
98 views

What is the significance of the Inverse-square law? [duplicate]

Considering its occurrences in various fields like Electrostatics, Gravitation, Acoustics etc. how does the law bind these topics together?
Two bodies of mass $M_1$ and $M_2$ are connected by a spring but are otherwise free to move along a horizontal line. A periodic force $F\cos\omega t$ is exerted on the body of mass $M_1$ along the ...