# Tag Info

### A question about superconductor from path integral

The minus sign doesn't matter, because you're dealing with Grassmann variables ($\Psi$ describes the fermionic degrees of freedom.) As such, the Gaussian (Grassmann) integral always converges. ...
• 81

### Is a superconductor 'perfect' ? i.e. does current flow forever without decaying?

You say "temperature above 0K", however any superconductor losses the superconductivity properties above a certain temperature. If the material is a superconductor and you induce a current ...

### Is a superconductor 'perfect' ? i.e. does current flow forever without decaying?

The basic idea is that for a superconductor the state of least energy can have a non-zero current. If this is already a state of least energy then there is no further lower-lying state for it to decay ...
• 47.5k

### Superconducting electromagnets?

Any work done by a supercooled magnet would dissipate energy. An electric induction motor using supercooled state and field would simply have nearly zero internal resistive loses, resulting a motor ...

### On the optical properties of quadrupolar magnets

The power of a lens is 1/f. Also sometimes called the strength of the lens. Stronger lenses bend the light more. The focus closer to the geometric optics lens. So I think that he is just saying a ...
• 1,531

Top 50 recent answers are included