question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>Why graviton is spin 2 instead of spin 1?
Is it because the traceless symmetric tensor has rank 2?
In many articles, they say the graviton is spin 2 particles, but they don't mention why.
I find some interesting article in the following sites
<a href="http://nige.wordpress.com/2010/01/21/woit-and-the-spin-2-gravi... | g458 | [
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<p>Consider two Bogoliubov - de Gennes Hamiltonians with equations for excitation energy,
$$\left(\begin{array}{cc}
H_{0} - E_{F} & \Delta \\
\Delta^{*} & E_{F} - \sigma_{y}H_{0}^{*} \sigma_{y}
\end{array}
\right) \Psi_{0} = \mathcal{E}_{0} \Psi_{0}
$$
and with $H_{0}$ replaced by $H = UH_{0}U^{\dagger}$, wit... | g14819 | [
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<p>A conductor's area is reduced by half or possibly more. I calculated the induced-emf based on the original area unreduced, does it make sense to divide the induced-emf value to the reduction factor?</p>
<p>Say the area was reduced by half,therefore, diving the induced-emf value by /2?
I assume by reducing the area ... | g14820 | [
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<p>For example, the displacement R(r,t) of the single charge q is given by</p>
<p>$$R = R_0\cos(\omega t)$$</p>
<p>In the view of multipole expansion, what is the monopole moment and the dipole moment for this configuration? Why the monopole does not contribute to the final EM field?</p> | g14821 | [
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<p>On <a href="http://en.wikipedia.org/wiki/Weak_localization" rel="nofollow">Wikipedia</a> (pretty much the only place I can find an explanation of what weak anti-localization actually is) it is explained as:</p>
<blockquote>
<p>In a system with spin-orbit coupling the spin of a carrier is coupled to its momentum. ... | g14822 | [
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<p>In the diagonal terms of the <a href="http://en.wikipedia.org/wiki/Stress%E2%80%93energy_tensor" rel="nofollow">energy-momentum tensor</a>, the flow of $x$-momentum in the $x$-direction is the $x$-pressure. Why the flow of momentum is pressure? </p> | g14823 | [
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<p>Say:</p>
<ol>
<li>I have a gyroscope that is spinning in the xy plane along the z axis.</li>
<li>I then roll its spinning axis by some angle theta</li>
</ol>
<p>Now I know the gyroscope will resist my attempting to change its axis of rotation.</p>
<p>The question is:</p>
<ol>
<li>When I perform work to change th... | g14824 | [
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<p>Consider the Earth (mass $M$, radius $R$, rotating about its own axis at $\Omega$) and the moon (mass $m$, radius $r$, with axial rotation equal to $\omega_m$), whose centre of masses are $d$ apart. They rotate around their barycentre at $\omega_e$ and $\omega_m$ radians/second respectively (I believe $\omega_m=\ome... | g14825 | [
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<p>I don't understand the meaning of the expression "trivial topology" or "non-trivial topology" for an <a href="http://en.wikipedia.org/wiki/Electronic_band_structure">electronic band structure</a>. Does anybody have a good explanation?</p> | g14826 | [
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<p>I know that air can be under water if there is something to contain it that prevents its escape. But can a place such as buildings or ancient ruins submerged totally under water hold air pockets as bigger as a room?
I recently saw a home-made-video-of-sorts that claimed to have discovered a underwater ruin and showe... | g459 | [
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<p>I have a given a density matrix by $\rho:=\frac{1}{2} |\psi_1 \rangle \langle \psi_1|+\frac{1}{8} |\psi_2 \rangle \langle \psi_2|+\frac{3}{8} |\psi_3 \rangle \langle \psi_3|.$</p>
<p>Where $|\psi_1\rangle := \frac{1}{\sqrt{2}}(|0. \rangle -i |1. \rangle )$</p>
<p>$|\psi_2\rangle := \frac{1}{\sqrt{3}}(|0. \rangle -... | g14827 | [
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<p>On the second page of this <a href="http://arxiv.org/abs/quant-ph/0111032v2" rel="nofollow">paper</a> a term 'fundamental energy scale' is used while talking about a Hamiltonian. The context is implementing Deutsch's algorithm using Adiabatic Quantum Computation.</p>
<p>What is the fundamental energy scale of a Ham... | g14828 | [
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<p>Which atoms can slow down high energy neutrinos?
I mean in which medium high energy neutrinos will tend to slow?</p> | g14829 | [
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<p>What is this physical phenomenon and when it's happen ?</p>
<p>Please take a look at this picture:</p>
<p><img src="http://i.stack.imgur.com/k2hId.gif" alt="enter image description here"></p>
<p><a href="http://i.stack.imgur.com/k2hId.gif">Link to picture</a></p>
<p>Notice: This is a cork ball attracted to sides... | g500 | [
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<p><a href="http://scitation.aip.org/content/aip/journal/jcp/139/11/10.1063/1.4821161" rel="nofollow">http://scitation.aip.org/content/aip/journal/jcp/139/11/10.1063/1.4821161</a></p>
<p>The article states that the graphene filter has a much lower electrical resistance than existing ion exchange membranes, giving the ... | g14830 | [
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<p>I am studying through the book Thermodynamics and Statistical Mechanics by Walter Greiner and I’ve got a couple of doubts when I was reading about the classical ensembles, specially the Canonical ensemble (chapter 7, pages 159-160, Springer, 2004).</p>
<p>In the case of the canonical ensemble it is considered that ... | g14831 | [
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<p>I find that often times I'll be tripped up by questioning whether or not I can do something mathematically, and be unable to come up with a satisfying answer. This is, unfortunately, one of those times. </p>
<p>I'm told:</p>
<blockquote>
<p>A uniform electric field, $\vec{E} = E_0\hat{x}$. What is the potential,... | g14832 | [
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<p>Can you provide biographical information for R. Dolen, known for <a href="http://www.google.com/search?as_q=dolen+horn+schmid+duality" rel="nofollow">Dolen-Horn-Schmid duality</a>?</p> | g14833 | [
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<p>Is $\langle\psi_1|p\psi_1\rangle$ necessarily 0 for harmonic oscillator eigenstates?</p>
<p>If $\Psi(x,t)= c_0\psi_0(x)e^{-iE_0t/\hbar}+c_1\psi_1(x)e^{-iE_1t/\hbar}$,</p>
<p>is the following true? Where $p$ is the momentum operator,</p>
<p>$$\langle\psi_1|p\psi_1\rangle = \langle\psi_0|p\psi_0\rangle=0.$$</p>
<p... | g14834 | [
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<p>Humour me for a minute here and let's imagine that all interesting and plausible supersymmetry models have been "cornered" out by the experimental data;</p>
<p>what sort of alternatives are there for having quantum field theories with Poincare symmetry that are allowed to have nontrivial internal symmetries? i.e: t... | g14835 | [
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<p><a href="http://en.wikipedia.org/wiki/CHSH_inequality" rel="nofollow">CHSH inequality</a> requires both <em>locality</em> and <em>realism</em>. I will equate here realism with counterfactual definiteness.</p>
<p>Now counterfactual definiteness tells us that given two different measurements on the same object, descr... | g14836 | [
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<p>Obtaining the propagator for the <a href="http://en.wikipedia.org/wiki/Faddeev-Popov_ghosts" rel="nofollow">Faddeev-Popov (FP) ghosts</a> from the path integral language is straightforward. It is simply </p>
<p>$$\langle T(c(x) \bar c(y))\rangle~=~\int\frac{d^4 p}{(2\pi)^4}\frac{i e^{-ip.(x-y)}}{p^2-\xi m^2+i\epsil... | g14837 | [
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<p>I tested two electric scooters with almost same power (1500 W), but very different performances:
A "Zem Star 45" (1500 W, 60 Nm) can reach 50 km/h in "a few seconds" (not measured actually),
An "Ingaeta Ingo" (1500 W, ??? Nm) took more than 10 seconds to reach 50 km/h.</p>
<p>How much does torque affect accelerati... | g14838 | [
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://physics.stackexchange.com/questions/12559/what-conservation-law-corresponds-to-lorentz-boosts">What conservation law corresponds to Lorentz boosts?</a> </p>
</blockquote>
<p>For a relativistic free particle, What is the Noether charge gene... | g252 | [
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<p>Below are two drawn diagrams of the problem with some explanation. Note: I think my notation for the force that the block exerts on the plane in the horizontal direction is not the standard notation. I chose $F_{bx}$ but I think it might have been better to say something like $F_{px}$. Hopefully this isn't a pro... | g14839 | [
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<p>Can someone point me to the papers detailing when/where/how heavy fermion superconductors were first synthesized, tested and documented?</p> | g14840 | [
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<p>Two people falling with the same parachute will gain different speeds if their masses are different. The upward air drag will needed to be bigger for a heavier person, since gravitational force is bigger in his/hers case. <br>
In parachute case, the shape is almost the same. But what about two iron balls, one with w... | g14841 | [
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<p>Firstly, how is "density" of wave formulated as?</p>
<p>Secondly, when wave, travelling in less density medium, meets with the boundary that has higher density medium next to, reflected parts of the wave changes phase by 180 degrees. If then, how does the amplitude change?</p> | g14842 | [
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<p>I'm trying to join two ends of co-axial cables. I've managed to connect the two ends of copper wires but still the signal response is very low. When I try to stretch the cable signal gets good. Why does this occur? Is there a reason some sort of special procedure is needed to join the two ends of co-axial cables?</p... | g14843 | [
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<p>Photon has momentum and energy.assume i am creating a nuclear fusion by fusing hydrogen nuclei into helium and a photon is created.Now which direction does it(single photon) moves or travel?can we direct that single photon to any specific direction?</p>
<p>i am not a physics student,but please help me understand.</... | g14844 | [
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<p>Start without general relativity. Consider a metastable vacuum over good ol'-fashioned Minkowski space. It decays. A bubble forms and the domain wall expands. The domain wall is timelike, and accelerates, driven by the difference in pressure between both phases. Its speed approaches the speed of light asymptotically... | g14845 | [
0.0017269013915210962,
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0.03477342054247856,
0.02114679664373398,
0.02235... |
<p>How do you evaluate the canonical ensemble average of a product of spins, e.g.:</p>
<p>$$[S_zS_x]$$</p>
<p>Where:</p>
<p>$$S_x = \frac{\hbar}{2}
\begin{pmatrix}
0 & 1\\
1 & 0\\
\end{pmatrix}$$
$$S_y = \frac{\hbar}{2}
\begin{pmatrix}
0 & -i\\
i & 0\\
\end{pmatrix}$$
$$S_z = \frac{\hbar}... | g14846 | [
-0.02532123029232025,
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0.022831853479146957,
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0.045309849083423615,
0.027237245813012123,
0.... |
<p>Consider a system of point particles , where the mass of particle $i$ is $μ_i$ and its position vector is $\vec{r}_i$. Let $\vec{r}_\text{cm}$ is the position vector of the center of mass of the system. Considering the system from a reference frame attached to the center of mass, the system may have a spin about the... | g14847 | [
0.06415177881717682,
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<p>I have an interesting problem. A disk travels in air at velocity v1. It travels in glass (assuming that the disk can enter the glass without breaking it) at velocity v2. v1 is greater than v2. The disk has radius r.</p>
<p>Lets say that it hits the glass at a particular angle a. Then the part of the disk that enter... | g14848 | [
0.048700228333473206,
0.008672516793012619,
0.007742244750261307,
0.0402735210955143,
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0.02417929470539093,
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0.000037686895666411147,
-0.0... |
<p>There have been several questions about whether time is continuous or not and it seems like the answer isn't currently known. I know quantum mechanics treats time as continuous and any mathematics that involves integrating over some time interval treats time as continuous too.</p>
<p>Surely though there are experi... | g14849 | [
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0.00847439095377922,
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<p>In case of semiconductor the intrinsic charge carrier concentration N, always remains constant. This explains the decrease in number of holes when donor impurities are added to an intrinsic semiconductor and the decrease in number of free electrons when the no. of holes when acceptor impurities are added . Is there ... | g14850 | [
0.05908536538481712,
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0.005793350283056498,
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0.03861748427152634,
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0.01... |
<p>Imagine I have a (Lorentzian) manifold with a metric</p>
<p>$\left[ {\begin{array}{cc}
g_{\mu\nu} &0\\
0&g_{mn}\\
\end{array} } \right]$</p>
<p>Will the Ricci tensor be also block diagonal without any mixing of the two manifolds?</p> | g14851 | [
-0.004490184132009745,
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0.033885762095451355,
0.003200970124453306,
... |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://physics.stackexchange.com/questions/29903/why-do-people-recommend-wider-tyres-in-car-for-better-road-grip">Why do people recommend wider tyres in car for better road grip?</a> </p>
</blockquote>
<p>Static/kinetic friction says that the fri... | g460 | [
0.07350010424852371,
0.01701424829661846,
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0.06205189973115921,
0.022816166281700134,
0.054716598242521286,
0.013427185826003551,
-0.04043954238295555,
-0.05223066359758377,
0.039734747260808945,
-0.031917594373226166,
0.03214463219046593,
-0.035... |
<p>You have likely heard those sounds, science museums sometimes sell Flexible plastic tubes you can whirl like a lasso. The air rushing by the end of the tube causes these sounds, which are admitted in discrete "notes".</p>
<p>What physical process causes that strange segmenting of the sound into a discrete "scale"? ... | g14852 | [
0.009866176173090935,
0.022950200363993645,
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-0.08321765810251236,
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0.045140720903873444,
... |
<p>The most recent set of experiments sent to the ISS included 32 fish which are going to be studied in a space aquarium called the Aquatic Habitat. On Earth, an air pump pushes air which flows out of an airstone and travels, in the form of bubbles, up to the surface of the tank. What happens in space? How do they aer... | g14853 | [
-0.0019016896840184927,
0.047791607677936554,
-0.010490831919014454,
0.016939712688326836,
0.001415383187122643,
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0.03647922724485397,
0.0821443647146225,
0.03415454551577568,
0.00... |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://physics.stackexchange.com/questions/40829/from-how-high-could-have-felix-baumgartner-jumped-without-disintegrating-like-a">From how high could have Felix Baumgartner jumped without disintegrating like a shooting star?</a> </p>
</blockquote>
... | g461 | [
-0.0016926235985010862,
0.056293997913599014,
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0.06780900806188583,
-0.037914592772722244,
0.048599254339933395,
-0.03155772015452385,
0.004108346998691559,
-0.038205258548259735,
-0.02761811763048172,
-0.01625959947705269,
0.001359888119623065,
0.03157999366521835,
... |
<p>What exactly is happening in a laser's gain cell when the irradiance is greater than the saturation irradiance? </p>
<p>Also can someone offer a clear conceptual treatment of the gain-coefficient and its connection to the effective pump rate densities. </p>
<p>I apologize if my question is vague, I'm just having t... | g14854 | [
-0.024692494422197342,
0.013252492994070053,
-0.014514521695673466,
0.02184724435210228,
0.05289625748991966,
0.009257621131837368,
0.04209714010357857,
0.03404243290424347,
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0.02458052523434162,
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0.06091690808534622,
0.08508321642875671,
-0.0171... |
<p>What he is talking about sounds interesting to me, and I would like to know more. But I need to know the name first.</p>
<p><a href="http://www.youtube.com/watch?v=Ogn5FrVGtAg&hd=1" rel="nofollow">http://www.youtube.com/watch?v=Ogn5FrVGtAg&hd=1</a></p> | g14855 | [
-0.012308109551668167,
0.046689603477716446,
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0.00849646981805563,
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0... |
<p>I want to show that an arbitrary wavefunction $f$ in a one dimensional harmonic potential reproduces itself after a period T up to a phase factor: $f(x,t+T)=Af(x,t)$, $|A|=1$</p>
<p>I am not sure if this is the correct way to begin, i googled the following, I do not know how to obtain it algebraically:</p>
<p>$$f... | g14856 | [
-0.00028071418637409806,
-0.03408294916152954,
0.00895869079977274,
-0.04500000551342964,
0.027654798701405525,
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0.044850755482912064,
0.0279389638453722,
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0.0013408084632828832,
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0.04697138071060181,
0.012146084569394588,
0.0... |
<p>Could someone explain to me the physical meaning of vector Laplacian of Electric field intensity?</p>
<p>Where vector Laplacian means: $$\nabla^2 \mathbf{E} = \nabla(\nabla \cdot \mathbf{E}) - \nabla \times (\nabla \times \mathbf{E})$$
Thanks!</p> | g14857 | [
0.03536170348525047,
0.0253666490316391,
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0.026510115712881088,
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0.011544118635356426,
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0.03342537581920624,
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-0.04072... |
<p>I'm trying to understand to find my homework problem. Its a simple concept of finding force. I wonder if you have two formulas then is the total Force = force from x + force from y. Or $\sqrt{forceX^2+forceY^2}$. And why. It would make sense to me for it to be the sum of two forces if its not so why not??</p>
<p>I ... | g14858 | [
0.05671491473913193,
0.02628885582089424,
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0.00040628641727380455,
0.007590099237859249,
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-0... |
<p>I remember reading somewhere:</p>
<blockquote>
<p>when you sleep in a way subjecting your body to cut the geomagnetic
field at right angles, you become highly emotional whereas when it
is Parallel, it cools your mind.</p>
</blockquote>
<p>Meaning, it's better to sleep with your body/bed aligned in north-sout... | g14859 | [
0.025953439995646477,
0.04312806949019432,
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0.014056767337024212,
0.035391613841056824,
-0.0... |
<p>I noticed a strange behavior of my experiment. I have a glass container with a fully saturated solution of CuSO4, which I use to grow CuSO4 crystals, by waiting for the water to evaporate. Recently I noticed that crystals were build above water surface and outside of the container. After some time I noticed that hal... | g14860 | [
0.010593961924314499,
0.054678406566381454,
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0.017767375335097313,
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0.048285990953445435,
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<p>Moons orbit planets, planets orbit stars, and stars orbit the center of a galaxy.</p>
<p>So, my question is what does a galaxy orbit? The center of universe? (I know that the universe has no center)</p> | g14861 | [
-0.028714677318930626,
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<p>In supergravity solutions, one sometimes encounters the case where the manifold may be a bundle over some base space, and one has to write down the explicit metric regarding such bundle. I would like to illustrate this with the following simplified example:</p>
<p>As is well known that the three sphere $S^3$ may be... | g14862 | [
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0.031196247786283493,
0.0313... |
<p><img src="http://i.stack.imgur.com/S5YRd.png" alt="enter image description here"></p>
<p>They seem to adopt a convention that delta x must always be positive. </p>
<p>Otherwise, there is no way to know what the phase difference of the sources actually means. </p>
<p>Does a 90° difference mean that source two has ... | g14863 | [
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-... |
<p>I am planning on doing a space simulation program with full physics and as part of a hack to avoid too many issues with number precision I was going to switch orbiting objects to a calculated orbit (rather than rely on accurate gravity effects to keep it in perfect orbit). For this, I need to know if an object is in... | g14864 | [
0.029401199892163277,
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0.004610694944858551,
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-... |
<p>I've been arguing with a friend about the whole "perfect vacuum" concept. He and I agree that the most powerful vacuum pump in the world couldn't pump water more than ~34 feet above the surface of a regular elevation lake. I changed the problem slightly, and I'm not sure what would happen.</p>
<ol>
<li>Submerge a h... | g14865 | [
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0.00628791144117713,
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0.001870659296400845,
0... |
<p>Its been stated in Wikipedia regarding Reynolds number(Re) that "laminar flow occurs when Re<2300 and turbulent flow occurs when Re>4000. In another wiki file related to Kármán vortex street it has been stated that "A vortex street will only be observed over a given range of Reynolds numbers (Re), typically above... | g14866 | [
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0.039... |
<p>In magnetohydrodynamics, the Richtmyer Meshkov instability is found to get suppressed by application of longitudinal magnetic field.
Exactly what happens at the interface? Why instability gets suppressed? (How one can get the physical intuition of what is happening?)</p> | g462 | [
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<p>There are books like Halliday Fundamental of Physics and there are books titled Classical Mechanics.</p>
<p>To me, these two types of books seem to cover the same thing.</p>
<p>Is there any difference?</p>
<p>(If anyone needs specific example, Halliday vs. Classical Mechanics by John R. Taylor.)</p>
<p>Edit:
Wh... | g14867 | [
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-0.... |
<p>And when they are paralleled, orbital angular momentum is 0. </p> | g463 | [
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<p>I am reading papers about solitons for my small reports, and i could not understand its physical meaning in detail. </p>
<p>I know soliton is solitary wave which behaves like particle. And many text they talk about kink, vortices, strings, monopoles, dyons....... </p>
<p>I read that solutions of Sine-Gordon equati... | g14868 | [
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<p>Let me put things into perspective by comparing with other applications of string theory. Nowadays review papers written by cosmologists about inflation models often discuss string theory scenarios such as brane inflation, among other non-stringy models. Also you often hear about heavy-ion theorists and experimental... | g14869 | [
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-0... |
<p>We're finding forces (and whether they're in tension or compression) using the Method of Joints and Method of Sections. I don't understand why sometimes it's necessary to find the support reactions, but sometimes it's not. Please help. Thank you!</p> | g14870 | [
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0... |
<p>Starting with a pot of cold tap water, I want to cook a hard-boiled egg using the minimum amount of energy. Is it more energy efficient to bring a pot to boil first and then put the egg in it, or to put the egg in the pot of cold water first and let it heat up with the water?</p> | g14871 | [
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0.0037460552994161844,
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0.... |
<p>I read that the ionosphere can be defined as plasma.</p>
<ul>
<li>it has its plasma frequency</li>
<li>it has its Debye length</li>
<li>it is overall neutral</li>
</ul>
<p>As it is overall neutral it <strong>does not produce any electric field</strong>.</p>
<hr>
<p>However, as far as I know, a <strong>force fiel... | g14872 | [
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<p>I'm working through my old notes on QFT (cf. Ref 1) and I'm not quite sure how to approach the derivation of the Hamiltonian density for a free scalar field (<a href="http://www.stfc.ac.uk/PPD/resources/pdf/QuantumFieldTheory09.pdf" rel="nofollow">question 2.3 on page 19</a>) and the subsequent derivation of the com... | g14873 | [
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<p>I am trying to formulate the wave function that describes two entangled electons having the same position but opposite spin. According to the Pauli exclusion principle this should be possible. And when their spin would be equal, the wave function would cancel out and become 0.</p>
<p>I tried:
$\psi({r}_1,r_2,s_1,s_... | g14874 | [
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0.07790976762771606,
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<p>Recently, I was reading about Hawking Radiation in <em>A Brief History of Time</em>. It says that at no point can all the fields be zero and so there's nothing like empty space(quantum fluctuation etc.). Now, the reason mentioned was that virtual(force-carrier) particles cannot have both a precise rate of change and... | g14875 | [
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<p>Let's imagine a asteroid that travels with 0.99999999999999999c.</p>
<p>(I know it's impossible).</p>
<p>Anyway... Relativistic mass of such object would be almost equal to earth's stationary mass. </p>
<p>Now let's imagine that such object passes closely to me (assuming I'm immortal etc.). According to $F_g=GMm/... | g112 | [
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<p>This is a serious question from someone engaged in evaporating large quantities of water to turn sap into syrup at this time of year.</p>
<p>Probably some background will help. When sap boils vigorously it creates quite a bit of foam, which will overflow the evaporator (incidentally filling the building with a plea... | g14876 | [
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<p>I'm trying to explain to someone learning elementary physics (16 year old) that linear momentum and energy are conserved independently. I'm not a professional physicist and haven't tried to explain this stuff for years, and I can't think of any convincing elementary argument to show that this is the case. Does anyon... | g14877 | [
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<p>Not a boost straight up to escape velocity, just sufficient added momentum to make a significant economic saving on fuel cost, mass and complexity of a standard launch. It seems ludicrous to me how much fuel in a standard launch appears to be wasted pushing thousands of tonnes of rocket fuel in a vertical direction ... | g464 | [
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<p>When I was a boy I used to daydream about building a tower so tall that the top of it would <strike>stick out of the top of Earth's atmosphere</strike> project into near space.</p>
<p>There would perhaps be a zero gravity area in the penthouse where my friends and I could bounce around and play space versions of va... | g14878 | [
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<p>I know that coordinate system shifting can be represented using matrices. But how exactly are similarity transformations related to coordinate shifts ? </p> | g14879 | [
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<p>I was watching a BBC documentary on space last night. It was talking about gravity, and it said that the reason we only ever see one side of the moon, is because the earths gravity is strong enough to actually stretch the moon into a longer shape, creating a 7m bulge on the moon.</p>
<p>This bulge travelled around... | g14880 | [
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<p>I understand that coercivity is the field/force required to demagnetize/magnetize a ferromagnetic material.
What if we had two opposite magnetic fields of different strengths values H acting on the same ferromagnet what would happen? </p>
<p><strong>H1</strong> = 50 Oe
<strong>H2</strong> = 10 Oe</p>
<p>The coerci... | g14881 | [
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0.03968573361635208,
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<p>In Peskin and Schroeder's QFT book, on page 219, there is the following equation:<img src="http://i.stack.imgur.com/nC46a.png" alt="enter image description here"></p>
<p>The heading to the equation is: "The Fourier transform of the two-point function can now be written as".</p>
<p>Could someone help me formally pr... | g14882 | [
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0.015962... |
<p>Let's say I fire a bus through space at (almost) the speed of light. If I'm inside the bus (sitting on the back seat) and I run up the aisle of the bus will I in fact be traveling faster than the speed of light? Relative to earth that I just took off from.</p> | g109 | [
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0.0333... |
<p>I am having a difficult time solving this. Say that electrons are emitted from a source S at a very slow rate. If both slits S1 and S2 are observed, we would have roughly 50% probability of detecting an electron at one of the two slits. The interference pattern is lost and the intensity distribution will appear as t... | g14883 | [
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0.03238970786333084,
0.047124672681093216,
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0.0025... |
<p>I'm a philosophy student (I, regrettably, don't know calculus or much physics). Last year I spent some time learning how work, power, speed, velocity, energy, force, and acceleration relate. But I was never able to fit my understanding of acceleration into my understanding of the world. I think my biggest challenge ... | g14884 | [
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0.023... |
<p>I am asked to find the wavefunction of the particle in a well subject to an additional potential
$$V(x,t)=\frac{\pi x \hbar}{L}\delta(t).$$
I have already solved that
$$\psi(x,t)=\exp\left(\frac{-i}{\hbar}\int^t_0H(t')dt'\right)\psi(x,0).$$
I understand this equation, but I am unsure of how to treat the delta poten... | g14885 | [
0.02934888005256653,
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0.011898456141352654,
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0.0... |
<p>Alright, I'm completely stuck on this and so is everyone else I've asked.</p>
<p>A freezer has a temperature Tc = -23℃. The air in the kitchen has a temperature Th = 27℃. The freezer in not perfectly insulated and heat leaks through the walls of the freezer at a rate of 50 W. Find the power of the motor that is ne... | g14886 | [
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0.00020149708143435419,
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0.0563078373670578,
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0.0... |
<p>I came upon the concept of irreducible vector-spinors while trying to simplify an expression involving the gravitino field.</p>
<p>It is claimed that an <em>irredicible</em> vector-spinor is gamma-traceless, i.e.
$$ \Gamma^M \psi_{\alpha M} = 0.$$</p>
<p>Are there conditions on the irreducibility besides the above... | g14887 | [
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0.050193000584840775,
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0.03625629097223282,
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<p>I have a particle with total energy $E$ confined in a potential
$$U(x) = -\frac{\cos^4x}{2} - m \cos x - f \sin x. $$
The constants $f$ and $m$ are both in the range (-2,2). The energy is such that the particle is in a bound state, with turning points $x_1$ and $x_2$ on either side of the origin.</p>
<p>I want to m... | g14888 | [
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0.034882333129644394,
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-0.0030365800485014915,
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0.06504163891077042,
-0.006582167465239763,
... |
<p><strong>NOTE.</strong> This is not a question about mathematics and in particular it's not a question about whether one can endow the torus with a symplectic structure.</p>
<p>In an answer to the question</p>
<p><a href="http://physics.stackexchange.com/questions/123725/what-kind-of-manifold-can-be-the-phase-space... | g14889 | [
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0.038320012390613556,
0.037640709429979324,
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... |
<p>If $r=0$ in the well know equation $F= G\dfrac{m_1\cdot m_2}{r^2}$, it will not follow that the force will be infinite?</p>
<p>May someone please clarify it to me?</p> | g465 | [
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-... |
<p>I'm talking about the maximum speed if let's say I have a car with the power $P = 1000 \text{W}$ and a force of friction of $5 \mbox{N}$ acting in the opposite direction. After some googling I found that the maximum speed is given by $P=Fv$, where $P$ is the power, $F$ is the force, and $v$ is the velocity.</p>
<p>... | g14890 | [
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0.05961894616484642,
0.0452120304107666,
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-0.017688902094960213,
0.01981939561665058,
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0.010707161389291286,
0.022766... |
<p>A while ago an experiment demonstrated that it is possible to stop a light pulse in a supercooled sodium cloud, store the data contained within it, and totally extinguish it, only to reincarnate the pulse in another cloud two-tenths of a
millimeter away.</p>
<p><img src="http://i.stack.imgur.com/MzZxz.gif" alt="lig... | g14891 | [
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-0.05477319285273552,
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0.03723744675517082,
0.018542246893048286,
-0.042... |
<p>Being able to slow down light to the speed of a bicicle as shown in <a href="http://www.youtube.com/watch?v=EK6HxdUQm5s" rel="nofollow">this vid</a>:</p>
<p><a href="http://www.youtube.com/watch?v=EK6HxdUQm5s" rel="nofollow">http://www.youtube.com/watch?v=EK6HxdUQm5s</a></p>
<p>Led to a question: Given a unit of s... | g14892 | [
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0.01142327394336462,
0.02627154067158699,
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-0.01... |
<p>Stimulated by my some recent calculations on edge states(ES) for time-reversal invariant(TRI) topological superconductors(TS) as well as many questions concerning the "edge states" in Physics StackExchange(e.g. <a href="http://physics.stackexchange.com/questions/57179/is-edge-state-of-topological-insulator-really-ro... | g14893 | [
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-0.... |
<p>To find magnetic or electrical moments in quantum theory we must calculate the expectation value of an appropriate operator. the dipoles operator are similar and is easy to find but the magnetic quarupole moment, I couldn't find.</p> | g14894 | [
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0.0023972496856004,
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0.005... |
<p>We know that there is uncertainty principle, so question: can we ever measure wavefunction of particles? I do not think this is possible, but I am not sure. I guess that everything is probabilistic. (that's why, I believe, we have sigma level when we say we discovered some particles...)</p> | g14895 | [
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0.011983710341155529,
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... |
<p>Theres a problem for intergalactic astronauts which is finding their way back to Earth. Combining all the rotational speeds, we are spinning and orbiting the sun, in our solar system which is spinning in the Milky Way, which is spinning in a large cluster, which in turn spins in a super cluster. Combining all the sp... | g14896 | [
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0.012020855210721493,
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<p>What is the magnetic quadruple moment of a nuclei in cylindrical coordinates?</p>
<p>The quadrupole moment of a nucleus is zero in spherical coordinates but in the cylindrical coordinates it can't be vanished. In cylindrical coordinates we are not able to use <code>jlms</code> and its very difficult to solve the in... | g14897 | [
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0.03712054714560509,
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0.012409253045916557,
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<p>I have learned in school regarding the relationship between speed,acceleration and distance is </p>
<p>$$v^2-u^2=2as $$</p>
<p>The initial velocity of India's Mars Orbiter Mission, MOM, is 32 km/s <a href="http://indiatoday.intoday.in/story/mars-orbiter-mission-india-leaves-earth-orbit-isro-china/1/327296.html" re... | g14898 | [
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0.04378093034029007,
0.047714... |
<p>Is there something intrinsic about the structure of space that gravity is proportional to 1/r^2 instead of, for example, 1/r^2.143 ? What makes the exponent turn out to be a nice even number? </p> | g466 | [
0.045743994414806366,
0.021147388964891434,
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0.00832817330956459,
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0.0201... |
<p>From the Earth If we observe two galaxies that are diametrically opposed and each 1000ly far from the earth. the separation distance between the galaxies will be 20000ly? really question is: if the galaxies were separated from Earth 10Gly. then the separation distance between galaxies would 20Gyr?</p> | g14899 | [
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<p>I'd like some suggestions for good reading materials on the Keldysh formalism in a condensed matter context. I'm familiar with the imaginary time, coherent state, and path integral formalisms, but lately I've been seeing Keldysh more and more in papers. My understanding is that it is superior to the imaginary time f... | g14900 | [
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0.013682598248124123,
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0.0349837951362133,
0.02803... |
<p>This may seem trivial, but I'm having some trouble deriving the finite difference form of the heat equation with a thermal conductivity function $a(x)$ depending on $x$:</p>
<p>$$\frac{\partial u(x, t)}{\partial t} = \frac{\partial }{\partial x}[a(x)\frac{\partial u(x, t)}{\partial x}]$$</p>
<p>I find some trouble... | g14901 | [
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0.05025810748338699,
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0.0... |
<p>How far apart do scientists estimate was/were the dying star(s) that supplied the elements that comprise our sun, planet, and us? With stars so far apart and expansion of space (as I understand it) carrying things further away still, it would seem to be a low probability occurrence for sufficient quantities of eleme... | g14902 | [
0.021547764539718628,
0.03780956566333771,
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0.020172815769910812,
0.06381503492593765,
-... |
<p>I have a good background in linear algebra, Topology and Differential geometry. I would like to understand the concept of supersymmetry in theoretical physics, and hopefully read Witten's landmark paper <em>Supersymmetry and Morse theory</em> sometime later. Please suggest suitable references. Thanks </p> | g467 | [
0.00962798297405243,
0.06341061741113663,
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0.05304234102368355,
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0.07159480452537537,
0.0... |
<p>Is there any theory that gets rid of gravitational wave and still matches with all correct predictions made by standard physics theories? (e.g. General Relativity)</p> | g14903 | [
0.06947716325521469,
0.027310287579894066,
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0.015572180040180683,
0.00786... |
<p>A ball is thrown from the top of a tower with a certain initial speed. It's downward acceleration is g. But why? the initial force makes no difference?
and, if not, if I get a revolver and shoot down, the bullet's downward acceleration equals g too?</p> | g14904 | [
0.08151455223560333,
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0.031022178009152412,
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-0.02567... |
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