# Tag Info

### Location of an object in empty space

Your logic is faulty. If there is a Universe containing only a single object then you cannot specify its location relative to anything else- that is true. You can arbitrarily label its position with ...
• 22.4k

### Location of an object in empty space

Yes, you can define where the singular object is. You can always define a coordinate system. If you do that, the object is at $P$, and the origin is at $O$. For obvious reasons, one may choose $P=O$ (...
• 28.3k

### Location of an object in empty space

To make the question well-defined we need to specify first what is meant by "the void". The usual practice in physics is that anything called "the void" has symmetry with respect ...
• 52.2k

### Normal ordering and construction of the physical Hilbert space

Broadly speaking I'd say your interpretation is basically right. Consider a system of spinless, non-interacting fermions in a box with volume $V$. The vacuum state $|0\rangle$ is annihilated by all of ...
• 61.7k

### What is the minimum voltage required to make electrons flow in a vacuum diode?

In a vacuum diode, the cathode exhibits thermionic emission: heat supplies the energy to liberate the electrons. A current flows even without any bias on the plate. It'll charge the plate to ~-1V if ...
• 13.3k
1 vote

### How do projective representations act on the QFT vacuum?

Yes, OP is right. More generally, one could consider a projective (not necessarily unitary) representation $\rho:G\to {\rm End }(V)$ where $$\rho(g)\rho(h)~=~c(g,h)\rho(gh),\tag{1}$$ and where \$c(g,h)...
• 185k
1 vote

### How do you account for all the photons and plethora of quantum particles in the box between the double slits and the back wall?

When you say "account for", I'm interpreting that as asking why doesn't the interaction between the photons/electrons and the environment destroy the interference pattern or lead to ...
• 357

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