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  1. S

    I Can someone expand (curlA.del)(curlA)

    is there a simpler expansion of ((∇xA).∇)(∇xA). This is a common term in fluid equations.
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    I Quantum Entanglement-Susskind-lecture 4&5

    In Lecture 5 on quantum entanglement, Susskind calculates the Bell's inequality terms using projection operator (a difficult concept and a tedious derivation). However, I believe the following I obtained the result on the Bell's inequality using the probability of spin of an electron prepared...
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    A Nonlinear first order Differential equation

    Good questions. My present mesh sizes are about 5% of the variation length of the driving term A. The driving term is sinusoidal in theta and phi with a mild radial dependence. (180,50,50) mesh. There is a sharper variation in one area and I have remeshed there 5 times. It is quite possible...
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    I Descriptiveness of this term

    One way to look at it is that it is the momentum imparted through the electromagnetic force, Momentum wikipedia - The classical Hamiltonian ℋ for a particle in any field equals the total energy of the system – the kinetic energy T = p2/2m (where p2 = p · p, see dot product) plus the potential...
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    A Nonlinear first order Differential equation

    I will try this, but that is only one term in (v.∇)v. The parameters have 3 components and the components of the equation have other component terms such as vr∂vθ/∂r.
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    A Nonlinear first order Differential equation

    The theta and phi coordinates are cyclic (v(0)=v(2*pi)), v=0, dv/dr=0 at v=0 and a.
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    A Nonlinear first order Differential equation

    I need to solve the well known momentum equation in 3D cylindrical coordinates: ρ(∂v/∂t +(v.∇)v)=A where A and the velocity v are both local vector variables. I am actually looking for the stationary solution to the equation, i.e. no ∂/∂t term) I have tried evolving the velocity and tried...
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    Flux surface average for a tokamak

    I am trying to figure out the flux surface average of a 3D perturbation in a tokamak. For example what is the flux surface average of cos(m*theta+n*phi) at a given flux surface. (Theta and phi being poloidal and toroidal angles respectively?
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    Don't quite Understand the terminology -- Local gauge

    I hope someone with a deep conceptual understanding of terminologies would help me out here. I am having starting problems in understanding the approach of gauge theories. I have read suggested threads and I am still at a loss. I am an experimental physicist and know basics of electrodynamics...
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    Hard Science Fiction

    Ditto on the Martian. Did you know that it was a manuscript rejected by publishers and the author published on the web and became an instant hit and in a year or so, the moviee is going to be out soon. Hilarious, serious, "down to Mars" movie with everything in it from present day NASA science.
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    Consequence of Making a Higgs particle

    I am still puzzled by this question. I admit that the Higgs decays, but only in a finite time such that, for example, energy has to be conserved. In the case of creating quarks etc., there are clear conservation laws. In the case of Higgs production there must be a consequence,a ripple and...
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    Consequence of Making a Higgs particle

    I apologize, I did mean Higgs Field but also a boson associated with it. Yes, I am wondering if the appearance of the Higgs boson changes the Higgs field locally and what is the consequence.
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    Consequence of Making a Higgs particle

    Now we are presumably creating (?) Higgs Bosons in the collider. But the universe is permeated already by the Higgs field and Higgs bosons. When the colliders make an "artificial" Higgs, what conservation laws (in addition to energy, momentum, charge, isospin, baryon number etc.)are obeyed? In...
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    Velocity Cone in expanding universe

    Thanks. I do see the figures and see the agreement with Jorrie's calculator. Great!
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    Velocity Cone in expanding universe

    The figures in http://www.astro.virginia.edu/class/whittle/astr553/Topic16/t16_light_cones.html are very useful in understanding the various world lines in concordant diagrams. Is there any easy way to see how a velocity cone (at the observer's worldline) from a later time than the Big Bang...
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    Early Universe scalar field, inflaton and analogies in electric field

    Excellent! Thanks Some give the analogy of a line of soldiers marching and then falling. An initial undulation in the line amplifies the end non-uniformity.
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    Early Universe scalar field, inflaton and analogies in electric field

    Thanks for the kind explanation. I do realize that the analogy is poor because the electric field is a vector, while phi (the field quantity) is a scalar. I guess that makes all the difference. As you point out, the terminology has been the same as that of a particle. Yes, that is very...
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    Early Universe scalar field, inflaton and analogies in electric field

    I have been trying to get my head around this topic for a while. As I go through the description of scalar fields, the inflation and the potential inflaton, (in description as in ned.ipac.caltech.edu), I constantly miss a concept. There must be a fundamental difference between the type of...
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    Flat Universe, dark energy and accelerating expansion

    Apologize for giving that link on Penrose. But there seem to be other allusions to big crunch and big bounce of Penrose in several places. You can google it if you like. No matter. You answered that question. But my main question is does an accelerating expansion imply negative curvature?
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    Flat Universe, dark energy and accelerating expansion

    Roger Penrose - http://unveiledsecretsandmessagesoflight.blogspot.com/2009/05/big-crunch-theory.html
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    Flat Universe, dark energy and accelerating expansion

    The CMB data suggests that the Universe is flat with in 0.4%. CMB data also shows that the expansion of the Universe is accelerating (from the sum of angles of triangle formed by distant hot spots- Saul Perlmutter, Brian P. Schmidt, and Adam G. Riess). The pushing out dark energy is about 74% of...
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    Parallel transporting of a vector in curved space

    Thanks. I was actually going from the other way about the dot product and the geodesic. I understood that the dot product remains constant (also zero) along a geodesic. Now, I see it. At other latitudes the north vector which is tangential to the constant latitude line is not perpendicular to...
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    Parallel transporting of a vector in curved space

    I got the case of travelling to the pole and returning to the starting point, that is a triangular path, but does this explanation work when working it out on a trapezoidal path, say west along equator then north to 30 deg latitude and then return? Would you not keep pointing the vector in the...
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    Parallel transporting of a vector in curved space

    True! I do see that slicing the sphere in one dimension opens up in that dimension, but the other remains curved, like peeled orange skin remains spherical.
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    Parallel transporting of a vector in curved space

    Thanks for the clarifications. The key thing seems to be that in order to measure the curvature, one has to transport in two or more directions. (Orienting a vector to the north at Arctic circle and transporting it around a longitude circle does not rotate the vector, except for great circles...
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    Parallel transporting of a vector in curved space

    I guess I can flatten the surface (as in Lambert Conformal conic ??) with a missing piece just like in a cone. The edge of the missing pie will not be straight, but vary sinusoidally (90 to latitude of the circle drawn). Am I right?
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    Parallel transporting of a vector in curved space

    Am I correct in saying that the angular deficit (change in angle) of a vector transported around a closed surface on a curved surface can only be observed by flattening the surface? Actually a further problem- I understand it from the flat sheet to a cone: Cut out a pie from a sheet, Draw a...
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    Confused-Aharanov-Bohm Effect

    Thanks. I believe the experiment implies that the phase shift is proportional to the change in the vector potential when the solenoid is turned on. One may add an arbitrary value to the vector potential everywhere, including inside and outside the solenoid before the solenoid is turned on...
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    Angular Momentum conserved but not energy?

    Thanks Guys/Girls!
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