# All Questions

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### Invariance of states under local unitary transformations [on hold]

How can I show explicitly that the bell state $$|\psi^{-}>=\frac{1}{\sqrt{2}}(|0>|1>-|1>|0>)$$ is invariant under local unitary transformations $U_{1}\otimes U_{2}$ ?
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### Do superpartners occur in nature if and only if nature is infinite? [on hold]

I have attempted to convince string theorists that the main problem with string theory is that string theorists fail to realize that Milgrom is the Kepler of contemporary cosmology. My impression is ...
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### What do we see - continuation

So far, the only answer to my question is that I must track every light beam in order to establish what do we see. I need help for this, and I give some arguments to volunteers. If we need to ...
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### A list of inconveniences between quantum mechanics and (general) relativity?

It is well known that quantum mechanics and (general) relativity do not fit well. I am wondering whether it is possible to make a list of contradictions or problems between them? E.g. relativity ...
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### How are anyons possible?

If $|ψ\rangle$ is the state of a system of two indistinguishable particles, then we have an exchange operator P which switches the states of the two particles. Since the two particles are ...
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### Prove the average quantum mechanical energy [on hold]

Prove that taking the limit as $h\rightarrow 0$ for the average quantum mechanical energy $h\nu/(e^{h\nu/k_BT}−1)$ yields the average classical energy, $k_BT$. Do you use l'Hôpital's rule for ...
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### Understanding Weinberg's soft-photon theorem

The soft-photon theorem is the following statement due to Weinberg: Consider an amplitude ${\cal M}$ involving some incoming and some outgoing particles. Now, consider the same amplitude with an ...
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### Theory behind patterns formed on Chladni plates?

In this video of vibrating Chladni plates we can see small sand particles align themselves into different interesting patterns which correspond to some particular vibrations. What is the theory ...
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### Why is the following gauge transformation singular?

Suppose I have a single particle Hamiltonian: $H=\frac{p^2}{2m}+\frac{\hbar k_0}{m}\vec{\sigma}\cdot\vec{p}$, either for boson or fermion. I do a gauge transformation ...
604 views

### Physics the Why vs. How question?

I've been told that a physicist never asks why and must always ask how. Is this true? Have all discoveries in physics been due to asking how? or have some been discovered by asking why?
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### Hubble's law for the Kasner solution

I'm puzzled with the following question: find an analog of the Hubble's law for the Kasner solution. Kasner metric is a solution to the vacuum Einstein equations ...
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### Why is Standard Model + Loop Quantum Gravity usually not listed as a theory of everything

I have often seeen statements on physics.SE such as, The only consistent theory of everything which we know of to date (2013) is string theory. Why exactly is this so? Adding the Loop Quantum ...
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### Frequency dependence of permittivity — why not monotonic?

I naively thought that most materials were transparent to radiation of frequencies above their plasma frequency, and opaque to radiation below it. The most intuitive (and analyzed lightly in ...
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### Time evolution of symmetrical mechanical systems

I asked this previously in an earlier question, although admittedly my question was hard to find in the slew of info I provided there, so hopefully this will clarify things. Suppose there's a typical ...
1k views

### Does a charged particle accelerating in a gravitational field radiate?

A charged particle undergoing an acceleration radiates photons. Let's consider a charge in a freely falling frame of reference. In such a frame, the local gravitational field is necessarily zero, ...
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### What is the relationship between kinetic energy and momentum?

I can't seem to figure out the relationship between $E_k$ and $p$ or $F$. I understand that the units are pretty different. But for example: A bullet with a mass of 10.0g is moving at the speed of ...
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### Are there any “Neutrinian” standard candles?

Are there any theoretical models/investigations of object far away that could act as some type of neutrinian standard candles? That is, they spew out neutrinos of with some know characteristics that ...
1k views

### Amount of energy required to hover.

I've noticed a motionless kingfisher over a lake looking for prey and wondered what amount of energy does a bird, weighing 0.15kg, require to hover for 15s?
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### Is optical-illusion responsible for Loch Ness monster? [on hold]

When you look out at the white-caps on a wind-swept lake, you can see a dark, undulating pattern under the crests of the white-caps. Could this shadow-like area explain the sightings? Edit First of ...
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### Small angle approximation for coupled pendulum

I am looking at a coupled plane pendulum problem where the pendula are identical with mass $m$ and length $r$, and connected by a spring with spring constant $k$ and an equilibrium seperation $d_0$. ...
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### Will Earth clock be slower than aeroplane clock when viewed from another planet?

I know that a clock placed on an aeroplane will have slowed with respect to a clock placed on earth because the more our velocities are, compared to the speed of light, the more the time slows down. ...
2k views

### What sustains the rotation of earth's core (faster than surface)?

I recently read that the earth's core rotates faster than the surface. Well, firstly, it's easier to digest the concept of planetary bodies, stars, galaxies in rotation and/or orbital motion. But, ...
1k views

### What are the calculations for Vacuum Energy?

In wiki the Vacuum Energy in a cubic meter of free space ranges from $10^{-9}$ from the cosmological constant to $10^{113}$ due to calculations in Quantum Electrodynamics (QED) and Stochastic ...
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### Spin Glass Prince Rupert's Drop

Spin Glass is known to converge to its ground state under Simulated Annealing. The word choice is especially interesting since annealing is also the name of a process performed on actual glass. ...