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| visits | member for | 1 year, 3 months |
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1d |
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What happens with the force of gravity when the distance between two objects is 0? possible duplicate: physics.stackexchange.com/q/2481 |
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1d |
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What happens with the force of gravity when the distance between two objects is 0? $GmM$ is not constant along the path to the center of the Earth. $M$ starts to decrease once you are underground, and becomes zero right at the center of the Earth. |
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Jun 12 |
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How can Magnets be used to pick up pieces of metal when the force from a magnetic field does no work? related: physics.stackexchange.com/questions/10565 |
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Jun 9 |
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Bose gas with $T = 0$ and $\mu < 0$ You might interested in this: tex.stackexchange.com/q/47078 |
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Jun 9 |
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Friction acting on a particle on a rough place There is static friction even when the particle is not moving. Friction always acts in the direction to oppose motion. |
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Jun 9 |
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Newton's third law of motion, and the collapse of objects under heavier weight Newton's third law doesn't say anything about whether the table will collapse. It only says that if the truck exerts a force $W$ on the table, the table also exerts $-W$ on the truck. This is true regardless of whether the truck is in a stationary position. |
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Jun 8 |
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Constructive physics more important than colliders? Where would you get the bricks, sand, and cement from? |
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Jun 1 |
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1 dimensional Ising model Chapter 7 of Kardar's "Statistical Physics of Fields" explains the low and high temperature expansion of the Ising model. |
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May 27 |
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Non-Hermiticity when Fourier transforming onto a finite lattice Doesn't the discretized sum have both $k$ and $-k$? |
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May 22 |
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Precise statement of Mermin–Wagner theorem The discussion in relation to a random walker is insightful. Do you have a reference for further reading? Other references, such as the one suggested by @Norbert above, require the coupling constants to be isotropic. However, this condition seems to be absent in your discussion. Why is this so? |
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May 15 |
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Why does quantum cryptography give us uncrackable codes? Why do you find the claims questionable? |
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May 13 |
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$SU(N)$ Neel manifold What is $m$?$ $ |
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May 3 |
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Reachable area of cannonball given fixed initial speed Consider using $\frac{1}{\cos^2\theta}=1+\tan^2\theta$ to obtain a quadratic equation in $\tan\theta$, with coefficients dependent on $x,y,v_0$. |
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Apr 30 |
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Tension of rope in the gravitational field of earth Consider the acceleration of each ball in terms of the forces and tension. The two balls should have the same acceleration. |
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Apr 19 |
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$\hbar \rightarrow 0$ in quantum mechanics It is worth noting that when a dimensionful quantity like $\hbar$ is taken to be small, it means that it is small compared to some quantity of the same dimension in the system. |
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Feb 7 |
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Validity of Bogoliubov transformation For $A$ and $B$ real, using the parametrization given in the Wikipedia article on BT, we would end up with the condition $B[\cos(\theta_1-\theta_2)\cosh 2r+i\sin(\theta_1-\theta_2)]=A\sinh 2r$. This will lead to the same assumption on $A$ and $B$. |
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Jan 21 |
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Elastic strings 1. Apply Hooke's law to find the spring constants. 2. Equating the relevant forces gives an equation containing the tensions. 3. Considering the difference in extensions of the strings give another equation. 4. Solving the two equation yields the tensions. |
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Jan 17 |
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Energy spectrum of a tight-binding model @nervxxx To do so, we split the system into the two sublattices consisting of the even and odd sites. Then, expressing the operators in each of the sublattices in momentum space, we can write the Hamiltonian as a $2\times 2$ matrix coupling the two sublattices. Finally, diagonalizing the matrix yields the energy spectrum. |
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Jan 17 |
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Energy spectrum of a tight-binding model What would experiments say about the excitation spectrum then? Would the energy at zero momentum be $2t$ or $\pm 2t$? |
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Jan 4 |
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Intervals as infinitesimals of same order (Landau & Lifshitz) It would be useful to provide the context. |
