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| bio | website | motls.blogspot.com |
|---|---|---|
| location | Czech Republic | |
| age | 39 | |
| visits | member for | 2 years, 4 months |
| seen | 3 hours ago | |
| stats | profile views | 24,191 |
Hi, I am a string theorist and a publicist.
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Jan 22 |
answered | How to mathematically formulate the Two Slit Experiment in Special Relativity? |
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Jan 22 |
comment |
What is the difference between complex field and two scalar fields? It's not true that the two ways to describe the complex field differ in the ability to interfere. The two expressions are fully equivalent. Charged particles have to be excitations of complex fields but that's an entirely different question than interference. Much like $\phi_1$ and $\phi_2$ don't interfere with each other, $\phi$ and $\phi^\dagger$ don't interfere with one another. It's the same thing, just a different basis. |
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Jan 22 |
comment |
What is the difference between complex field and two scalar fields? Well, it doesn't matter when one discusses the equivalence of theories. But it does matter if you want to find a particular field redefinition that makes two expressions equal. |
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Jan 22 |
answered | Temperature of a System of molecules |
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Jan 22 |
revised |
What is time teleportation? added 57 characters in body |
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Jan 21 |
comment |
Understanding boundary conditions on slices of AdS5 I kind of agree even though moduli (scalar fields with no potential) could have any value of the constant, too. And on the contrary, the translational symmetry in string theory may also be broken, and even branes could perhaps be stabilized at some points. So to summarize, I kind of disagree that there is any difference. $X(\sigma,\tau)$ is just a field in a quantum field theory - a rather general two-dimensional CFT - so you can't possibly find any universal "qualitative difference" from other QFTs. |
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Jan 21 |
answered | Understanding boundary conditions on slices of AdS5 |
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Jan 21 |
answered | How can a photon have no mass and still travel at the speed of light? |
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Jan 21 |
revised |
Photon wave packets from distant stars added 171 characters in body |
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Jan 21 |
answered | Photon wave packets from distant stars |
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Jan 21 |
revised |
Newton's cradle added 395 characters in body |
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Jan 21 |
answered | Newton's cradle |
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Jan 21 |
answered | Special relativity version of Feynman's “Space-Time Approach to Non-Relativistic Quantum Mechanics” |
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Jan 21 |
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Does decoherence need non-determinism? I would answer the same thing, so plus one point. ;-) |
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Jan 21 |
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What are the main differences between these quantum theories? Dear Amir, I am not sure whether a full-fledged answer is appropriate here. But all "quantum" things are quantum while the classical physics is not. Quantum physics has all the special things. Quantum field theory and quantum gravity are two special cases of quantum mechanics; quantum gravity may also be viewed as a "slightly modified" special case of quantum field theory. Quantum field theory is quantum mechanics with special relativity included while quantum gravity is any quantum mechanical theory with general relativity included - string/M-theory is the only known example. |
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Jan 21 |
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How general is the Lagrangian quantization approach to field theory? Perfect answer, Moshe, +1. |
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Jan 21 |
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What is the difference between complex field and two scalar fields? Kostya: the charge conjugation exchanges $\phi$ with $\phi^\dagger$. Because $\phi=(\phi_1+i\phi_2)/\sqrt{2}$ and $\phi^\dagger=(\phi_1-i\phi_2)/\sqrt{2}$, it follows that the exchanging of $\phi$ and $\phi^\dagger$ in this case is simply $\phi_2\to-\phi_2$ while $\phi_1$ is kept fixed. We say that $\phi_1$ is C-even while $\phi_2$ is C-odd. However, if $\phi$ is charged under any continuous symmetry, such as $U(1)$, it would be silly to decompose it into two parts. However, the message that the C-conjugation may look ad hoc is completely valid. C is not a God-given symmetry. |
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Jan 21 |
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What is the difference between complex field and two scalar fields? Dear Moshe, QGR was not telling you another solution. He was correcting your normalization. ;-) Kostya asked the question and listed two Lagrangians that are directly mapped to one another by QGR's redefinition, not yours. :-) |
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Jan 21 |
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Has the black hole information loss paradox been settled? A plus one point, Moshe. ;-) In 1) I would probably also add Matrix theory as a system with black holes and evaporation that is - even more - manifestly unitary. I agree with you that the "quasi-local description" explaining why the Hawking's original argument has a loophole is not known. And I agree that Hawking's later proof that the information works is not at the same level of robustness - or meaningfulness - as Maldacena's eternal BH paper. Cheers, LM |
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Jan 21 |
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What is quantum entanglement? Dear Anthony, OK, so the objects in entanglement swapping didn't have to interact with one another, but they had to interact with some other objects that interacted with each other :-). I just want to say that you can't create entanglement in the first place out of nothing. |
