# All Questions

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### All geodesics are inextendable?

I think the title is true, because geodesics has a tangent vector with a constant length parametrized by an affine parameter. Probably, it is easier to think about timelike or spacelike geodesics. ...
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### Is global gauge symmetry really a symmetry and local conserved current in gauge theories?

One way to define a gauge theory is that whenever the Lagrangian is invariant under some local transformations, we say these local transformations are local gauge transformations and the theory is a ...
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### What is a good book describing the major experiments in Quantum mechanics? [on hold]

I need some book suggestions on few of the major experiments done in Quantum Mechanics which are important in terms of what they imply, how they prove or disprove any theory that still exists or was ...
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### How does the second law of thermodynamics follow from low entropy of early universe?

One of the explanations of the second law of thermodynamics is that it goes back to the low entropy in the early universe (How do you prove the second law of thermodynamics from statistical ...
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### Quantum Entanglement Versus Inflation in the Early Universe?

Quantum entanglement is one of the most fascinating and mysterious phenomena in nature. It needs no interactions, or any sort of exchange for it to take place. It is possible, not against any rules of ...
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### Why is quantum entanglement considered to be an active link between particles?

From everything I've read about quantum mechanics and quantum entanglement phenomena, it's not obvious to me why quantum entanglement is considered to be an active link. That is, it's stated every ...
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### Rare earth minerals in solarcell production

When I was looking at photovoltaic solar cell production I saw that there was some difficulty with rare earth minerals used in the production but i can't find which rare earth minerals. I have tried ...