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| bio | website | sheerviscosity.net/blog |
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| location | ||
| age | ||
| visits | member for | 9 months |
| seen | Sep 27 '12 at 16:03 | |
| stats | profile views | 129 |
String theory grad student.
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Aug 4 |
comment |
Relativity - time dilation You have to be careful about simultaneity, which is not a frame-independent concept. In your original question, you defined simultaneous events in the frame of observer A (whether you intended to or not). As long as you stick with a frame you're fine. But now you launch the second chip in one frame, and want to discuss what it looks like in the first chip's frame, so you have to be careful. For example, in the first chip's frame the new launch does not happen when he is $10^{-6}$ months old, but after that! You have to work it out carefully. |
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Aug 4 |
awarded | Commentator |
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Aug 4 |
comment |
How is $\frac{dQ}{T}$ measure of randomness of system? A microscopic description (like statistical mechanics) considers the underlying degrees of freedom, and should explain how the observed 'macroscopic' phenomena emerge from the detailed model. If you derive the ideal gas law by postulating tiny atoms bouncing around -- that is a microscopic description. Of course a microscopic model at one level may become phenomenological once you go to more detailed observations, so this distinction depends on one's point of view. People who study optics would not call particle physicists 'phenomenologists' -- but strings theorists would. |
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Aug 4 |
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How is $\frac{dQ}{T}$ measure of randomness of system? I don't know about a 'formal' definition, but a phenomenological description is a description that is at the level of the observations. We observe that a system has certain properties that we can measure, like temperature, pressure, and so on. And we observe certain relations between these properties. When we combine these into a (hopefully simple) model -- that is a phenomenological description. For example, the ideal gas law and Ohm's law are both phenomenological models. |
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Aug 4 |
awarded | Revival |
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Aug 4 |
answered | How is dark energy consistent with conservation of mass and energy? |
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Aug 4 |
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Relativity - time dilation If you are down voting, it will be nice if you explain your reason for doing so. |
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Aug 4 |
revised |
Relativity - time dilation Clarified meaning of t(A),t(B),t(C) |
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Aug 4 |
answered | Relativity - time dilation |
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Aug 3 |
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How is $\frac{dQ}{T}$ measure of randomness of system? My advice to you, based on personal experience, is to accept these confusions until you learn about the definition of entropy in statistical mechanics (which is what Nathaniel refers to below). Entropy is defined for any system where the specific state is chosen from a probability distribution, and it directly measures our ignorance about which state the system is in ($S=0$ means we know the state exactly, $S$ maximal means all states have equal probability). I find it very confusing to try to understand it through $dQ/T$, since that is a phenomenological rather than microscopic description. |
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Aug 3 |
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Is the Higgs a quantum field or a particle? I understand; this is why I gave two additional definitions that explain why people think of Higgs excitations as particles. Sorry if this did more to confuse than to clarify. |
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Aug 3 |
awarded | Critic |
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Aug 3 |
answered | Is the Higgs a quantum field or a particle? |
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Aug 3 |
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Taking the continuum limit of $U(N)$ gauge theories I said it is similar, not the same. It seems to me this discussion has strayed from the original question. Why not post it as a new question? |
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Aug 2 |
awarded | Supporter |
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Aug 1 |
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Is spacetime discrete or continuous? I cannot access the full article because I do not have a scientific american subscription. I will say that statements like "If it works, it could rewrite the rules for 21st-century physics" are generally not indicative of interesting work. |
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Aug 1 |
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Taking the continuum limit of $U(N)$ gauge theories I don't have a reference but the story is similar to the multiplets in $d=4$, which are derived in any textbook on SUSY. You can repeat this exercise in $d=3$. |
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Aug 1 |
revised |
Is spacetime discrete or continuous? added 877 characters in body |
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Aug 1 |
revised |
Taking the continuum limit of $U(N)$ gauge theories Added caution |
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Aug 1 |
comment |
Taking the continuum limit of $U(N)$ gauge theories As they say, in the $N=3$ theory you can have hypermultiplets, and each hypermultiplet has two chiral multiplets: one in a rep $R$ and one in $\bar{R}$. It is not necessary that $R$ is the adjoint. A bit below the place you mention they consider various possibilities for $R$, only one of which is the adjoint. If you say that a hypermultiplet is 'fundamental' (which I think is not a precise statement although its meaning is clear), it means that you have one chiral multiplet in the fundamental and one in the anti-fundamental. |
