Guy Gur-Ari
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 Aug 9 comment Change in appearance of liquid drop due to gravity Their shape depends on their size. Small drops are spherical, larger ones look sort of like pancakes (this is what I mean by 'flat', perhaps this was not clear), yet larger ones look like parachutes. I don't know at which size (if any) they become elongated, but the shape is due to the flow of air and not gravity. I will try to clarify... Aug 9 answered Change in appearance of liquid drop due to gravity Aug 8 comment What is the fundamental differences between bound and entangled states Sorry, but I do not understand what you are asking. Specifically the phrases "the particle and the energy are bound to the process of entanglement" and "energy is determined to stay bound ..." make no sense to me. The photons do not exist before the decay. They are created when the particle decays. Aug 8 revised Possibility of making dark energy equivalent with dark matter Corrected title (energy -> matter) Aug 8 suggested approved edit on Possibility of making dark energy equivalent with dark matter Aug 8 comment What is the fundamental differences between bound and entangled states Here is a toy example. Let's say we have a massive particle with spin 0, at rest, that decays into two photons. The two photons fly out back-to-back due to momentum conservation. Due to angular momentum conservation, the total angular momentum in the photon axis is zero. So if we measure the helicity of photon 1, the helicity of photon 2 must be opposite. Thus the state after the decay is an entangled state. I am not sure what you mean by the second question, since in this example (and in many others) the entangled particles do not exist before the decay. Aug 8 comment Ghosts in Pauli Villars Regularization I think your propagator is missing a $-i$ (from $e^{iS}$), no? Aug 8 revised What is the fundamental differences between bound and entangled states edited body Aug 8 answered What is the fundamental differences between bound and entangled states Aug 7 answered Relating angular and linear kinematics Aug 7 comment How do I find work done by friction over a curve represented by a polynomial? @user1220376 The normal force you wrote down is for a body that is at rest. When a body moves on a curve the normal force is different because there is acceleration in the normal direction (as you get in circular motion). Beyond that, see Qmechanic's answer below. Aug 6 awarded Citizen Patrol Aug 6 comment “Time” by epistemic subdivision of a closed system Okay, thanks for letting me know. Aug 6 comment Derivation of the enhancement of U(1)$_L$ x U(1)$_R$ to SU(2)$_L$ x SU(2)$_R$ at the self-dual radius Yes, Polchinski section 8.3 (volume 1). Aug 5 answered Why are there two ways to solve for energy of a spring? Aug 5 comment “Time” by epistemic subdivision of a closed system I'm sorry but I don't think this is a question in physics. Aug 5 comment Does String theory say that spacetime is not fundamental but should be considered an emergent phenomenon? @RonMaimon As for AdS/CFT, I think that just by matching the symmetries it is clear that only one dimension is emergent in the CFT description. The non-commutativity you are referring to happens for example with D-brane coordinates but not with bulk coordinates, so I don't see how it changes the answer. Aug 5 comment Does String theory say that spacetime is not fundamental but should be considered an emergent phenomenon? @RonMaimon I agree that the nature of spacetime in string theory is not as simple as it appears in the worldsheet action, because of what you say. But the question was whether spacetime is emergent. In the usual (i.e. modern, textbook) treatment that everyone uses today, spacetime points are there from the start as fundamental variables, and therefore I think that spacetime is clearly not emergent. Aug 5 comment Does String theory say that spacetime is not fundamental but should be considered an emergent phenomenon? @NickKidman in the usual formulation, where you start e.g. with the Nambu-Goto action, you also have a spacetime metric as part of the string background. Aug 4 revised First Postulate of Special Relativity: What does it mean? added 2 characters in body