2:43 AM
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There is an innumerable number of questions and answers on this site about spatial, spacetime and temporal curvature. None of these answer my question. Unfortunately, many use the terms in different, sometimes confusing ways, that make it unclear what we exactly mean by our universe's spatial cur...

13 hours later…
3:17 PM
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Peskin & Schroeder's expression of the Noether current If a (quasi-)symmetry is defined as a transformation that changes the action by a surface term i.e. $$S\to S'=S+\int d^4x \partial_\mu K^\mu(\phi_a),\tag{1}$$ or equivalently, the Lagrangian changes by a 4-divergence, $$\mathscr{L}\to\mathscr... 6 hours later… 9:33 PM 1 I’ve read that short circuiting means that a huge amount of current flows through the conductor in an extremely small period of time. Also, resistance increases with temperature for conductors, right? So if temperature increases, resistance increases. Which would mean the current doesn’t have an ... 9:58 PM 2$$The~question~is~as~follows$$Figure shows a light rod of length l rigidly attached to a small heavy block at one end and a hook at the other end. The system is released from rest with the rod in a horizontal position. There is a fixed smooth ring at a depth h below the initial position of the ... 1 hour later… 11:13 PM 2 What will be the sensible extension of the 2D Ising to some curved surface - for instance, for a sphere or even something non-orientable? For the flat space energy is given by well-known expression:$$ E = \sum_{i, j} J s_i s_j + \sum_ih_i s_i  What would make sense for the curved surface, shou...