question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
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<p>In class I got given a diagram like this: (albeit without the Electrostatic force line)</p>
<p><img src="http://www.boredofstudies.org/wiki/images/b/bb/Sci_phys_quanta_strong_force.png" alt=""></p>
<p>However the teacher told us the nucleons are typically separated when the force is zero. So as the string force cr... | g13412 | [
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<p>Consider a cube of mass M resting on a rough surface such that the coefficient of friction between the cube and the surface is K. So in order to just slide the cube I need to apply a minimum force of KMg, g= acceleration due to gravity.
Now IF I apply a force, F which is very small as compared to KMg in magnitude th... | g13413 | [
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<p>I see that many papers written on fundamentals of thermodynamics(theory) nowadays are by some old professors somewhere(there may be exceptions). Most active young faculty don't seem to be seriously interested in reinterpreting thermodynamics like nonequlibrium thermodynamics i.e. continuing the work of Ilya Prigogin... | g13414 | [
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<p>At least if $\vec v$ is really only a one dimensional parameter, measuring all the moments $\langle v^n \rangle_f$ seems to give me all the information to compute $\langle A \rangle_f$ with $A(v)$ being a function of $v$. So integer powers of the generator of the function algebra $v$ are special functions. </p>
<p>... | g13415 | [
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<blockquote>
<p>Question: Find the relationship between angles $\theta$ and $\phi$
using the equations of equilibrium and solve for $\theta$.</p>
<p>Express your equation for $\theta$ in terms of $\phi$.</p>
<p><em>Hint: To derive the relationship between angles $\theta$ and $\phi$,
you first must write... | g13416 | [
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<p>I'd like to numerically simulate the magnetic field due to a cylindrical rare earth magnet of known dimensions at a bunch of points $\vec{r}=(x,y,z)$ from its origin. My goal is to be as accurate as possible up to some global normalization which ultimately doesn't matter for my application.</p>
<p>My approach is to... | g13417 | [
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<p>Why do wave functions spread out over time? Where in the math does quantum mechanics state this? As far as I've seen, the waves are not required to spread, and what does this mean if they do?</p> | g13418 | [
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<p>Suppose that two masses with different mass are connected by a string in horizontal frictionless table. Then when there is equal acceleration for two masses, string force would extend in some direction. My question here, why don't two boxes create canceling effect for string's stretching? (Often, in we just calculat... | g13419 | [
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<p>My book is incredibly scarce on insulator based Gauss law questions. Conductors seem to handle themselves pretty simply.</p>
<p>Here's a question I'm working on that isn't part of my book.
<img src="http://i.imgur.com/y2cDZdl.png" alt="question">
where the radii are $a,b,c,d$ from smallest to largest and gray regio... | g13420 | [
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<p>I was often told by my professor, using the following example, to demonstrate the relationship of conservation of energy and <a href="http://en.wikipedia.org/wiki/Lenz%27s_law" rel="nofollow">Lenz's Law</a>.</p>
<p>If you push a conductor into a constant magnetic field. By <a href="http://simple.wikipedia.org/wiki/... | g13421 | [
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<p>If there were extra compact dimensions,and at the big bang all dimensions were compact,my question is why the big bang failed to expand those presumed extra dimensions like it did with the 3 spatial classical dimensions and time?Moreover the expansion is still ongoing so why the presumed extra dimensions are fixed i... | g418 | [
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<p>Looking at the <a href="http://en.wikipedia.org/wiki/Nakajima-Zwanzig_equation" rel="nofollow">Nakajima-Zwanzig equation</a>, wich gives the time evolution of a projection $\cal {P} \rho$ of a full density matrix $\rho$, I am wondering if the trace of $\cal P \rho$ is preserved under time evolution.</p>
<p>The t... | g13422 | [
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<p>I have a conceputal question regarding the following problem:</p>
<p>A round massive stone disk with diameter $0.600 m$ has a mass of $50.0 kg$. The stone rotates at an angular velocity of $115.2 rad/s$, around an axis located at the center of the disk. An axe pressed against the disk applies a tangential frictio... | g13423 | [
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<p>Does anyone have a (semi-)intuitive explanation of why momentum is the Fourier transform variable of position?</p>
<p>(By semi-intuitive I mean, I already have intuition on Fourier transform between time/frequency domains in general, but I don't see why momentum would be the Fourier transform variable of position. ... | g8 | [
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://physics.stackexchange.com/questions/24548/is-the-portal-feasible-in-real-life">Is the Portal feasible in real life?</a> </p>
</blockquote>
<p>I'm designing a plausible faster-than-light (FTL) drive for a SF universe. Here's what I have so ... | g419 | [
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<p>When some smooth surface (like that of a steel or glass plate) is brought in contact with steam (over e.g. boiling milk) then water is usually seen to condense on that surface not uniformly but as droplets. What are the equations which govern the formation and growth of these droplets ? In particular what role does... | g13424 | [
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<p>Or, why is QFT "better" than QM?</p>
<p>There may be many answers.</p>
<p>For one example of an answer to a parallel question, GR is better than Newtonian gravity (NG) because it gets the perihelion advance of Mercury right.</p>
<p>You could also say that GR predicts a better black hole than NG, but that's a hard... | g13425 | [
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<p>I need to show that Green Function:</p>
<p>$\displaystyle G(\vec{r},t;\vec{r}^{\prime},t^{\prime}) = \frac{\delta(t-t^{\prime}\pm |\vec{r}-\vec{r}^{\prime}|\,/c)}{|\vec{r}-\vec{r}^{\prime}|}$</p>
<p>Obeys</p>
<p>$\displaystyle \nabla^2 G -\frac{1}{c^2}\frac{\partial^2 G}{\partial t^2} = -4\pi \delta(\vec{r}-\vec{... | g13426 | [
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<p>In the image, it looks like the tangential direction is always 45 degrees away from the string, not 90 degrees. Is it not the circular path that the solution is talking about?</p>
<p><img src="http://i.stack.imgur.com/dyjFb.png" alt="enter image description here"></p> | g13427 | [
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<p>Consider a zero-temperature, one-dimensional crystal with allowed electron momenta $k_n = \frac{2\pi n}{L}$.</p>
<p><strong>Question:</strong> Which is the more correct way to think about the Fermi sea? </p>
<ol>
<li><p>Sharp plane waves --</p>
<p>$$ \prod_{\epsilon_k<\epsilon_f} c_{k\uparrow}^\dagger c_{k\do... | g13428 | [
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<p>This regards the following problem:</p>
<p>A ray of light is traveling in glass and strikes a glass/liquid interface. The angle of incidence is $58.0^\circ$ and the index of refraction of the glass is $n = 1.50$. What is the largest index of refraction that the liquid can have, such that none of the light is transm... | g13429 | [
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<p>The following is the solution to the 1D diffusion equation with diffusion coefficient D, initial particle position $x_0$, and a perfectly absorbing boundary at $x=0$ (s.t. $P(x=0)=0$).</p>
<p>$$
P(x;t)=\frac{1}{\sqrt{4 \pi D t}}e^{-\frac{(x-x_0)^2}{4 D t}} - \frac{1}{\sqrt{4 \pi D t}}e^{-\frac{(x+x_0)^2}{4 D t}}
$$... | g13430 | [
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<p>I'm learning about the 2D ferromagnetic Ising model in zero field and trying to verify what I know by calculating the ground-state energy for the state with all 'up' spins in a 3x3 lattice.</p>
<p>$$H = -J\sum_{<i,j>}s_{i}s_{j}$$</p>
<p>where the sum is over nearest neighbors.</p>
<p>My question is, how do ... | g13431 | [
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<p>Let's make the question easier by considering two-level atoms(with spin states, i.e. spin up $|\uparrow\rangle$ and spin down $|\downarrow\rangle$). An article I recently read claims that atoms do not have dipole moments when they are in energy eigenstates (i.e. when you put it into a magnetic field in z direction).... | g13432 | [
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<p>As the title says, does a particle lose its location wavefunction if its location is measured exactly (I know this would be impossible in reality)?</p>
<p>Also, in reality, if one measures a particle, does the wavefunction of a particle become something different from original afterwards?</p> | g13433 | [
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<p>I was always curious how scientists achieve a particle with particular wavefunction (of location and spins etc.) </p>
<p>So how do they achieve it? Or is this impossible?</p> | g13434 | [
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<p>The relation</p>
<p>$$\psi=Ce^{i/\hbar(Et-\mathbf{p}\cdot\mathbf{x})}\tag{1}$$</p>
<p>satisfies the Klein Gordon equation on the mass shell, i.e. for $E^2=p^2+m^2$.</p>
<p>Now let's think in the reverse direction.
Relation (1) should satisfy the PDE:</p>
<p>$$\frac{\partial^2 \psi}{\partial E^2}-\frac{\partial^2... | g13435 | [
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<p>I was solving a practice Physics GRE and there was a question about springs connected in series and parallel. I was too lazy to derive the way the spring constants add in each case. But I knew how capacitances and resistances add when they are connected in series/parallel. So I reasoned that spring constants should ... | g13436 | [
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<p><strong>PART 1</strong>:<br>
I was reading the article <a href="http://en.wikipedia.org/wiki/Relativity_of_simultaneity" rel="nofollow">Relativity of simultaneity</a> Wikipedia. I couldn't understand this line: </p>
<blockquote>
<p>"if the two events are causally connected ("event A causes event B"), the causal ... | g13437 | [
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<p>I was wondering if it is possible to move the atom nucleus and leave behind the electrons? I can imagine that the electrons will follow the nucleus. But what if the speed of the nucleus is almost the same as the speed of the electrons or faster. where will the electrons go?</p>
<p>If it is not possible, do we have ... | g13438 | [
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<p>I have completely no idea and I am inquiring about this as it is an interesting question that popped in my head while doing physics homework.</p> | g13439 | [
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0.005510146263986826,
0.07253515720367432,
0.03411264717578888,
-0.0018962965114042163,
0.03129943832755089,
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-0.06190139427781105,
0.001201152103021741,
-0.036805201321840286,
-0.... |
<ol>
<li><p>If I wanted to solve the <a href="http://en.wikipedia.org/wiki/Einstein_field_equations" rel="nofollow">Einstein equations</a> for the solar system, which choice of $g_{\mu\nu}$ and $T_{\mu\nu}$ is more suitable? </p></li>
<li><p>I thought about using a <a href="http://en.wikipedia.org/wiki/Schwarzschild_m... | g13440 | [
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0.05828256160020828,
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0.05314645916223526,
-0.... |
<p>In a conformal field theory, is it possible to construct a machine that shrinks or expands objects?</p> | g13441 | [
0.016794882714748383,
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<p>I heard from my lecturer that electron has dual nature. For that instance in young's double slit experiment electron exhibits as a particle at ends but it acts as a wave in between the ends. It under goes diffraction and bends. But we don't see a rise in energy. It has to produce 500kev of energy (please correct if ... | g13442 | [
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0.018009118735790253,
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<p>I have been reading Young's book called: <em>University physics with modern physics</em> and on page 1284 author states that we can derive Lorenz time transformation by eliminating two equations for Lorentz space transformation along the vector of relative speed $u$. First we eliminate them for $x$ and then for $x'$... | g13443 | [
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0.03901379182934761,
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0.0... |
<p>Relative to the following</p>
<blockquote>
<p>Indeed, the modern point of view is that the operator of electric charge is the generator of a U(1) group. The charge quantization condition arises in models of unification if the electromagnetic subgroup is embedded into a semi-simple non-Abelian gauge group of highe... | g13444 | [
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0.02005661092698574,
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0.02460... |
<p>Let's say that we have two canister first bigger (metal canister 2l) with 1l of water at 100C, and second smaller (metal canister 1l) with 1l of ice. And we want to cool down boiled water to 50C. So we will insert ice (only ice not hole canister) into boiled water and after some time get wanted water (50C). </p>
<p... | g13445 | [
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0.06982023268938065,
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0.... |
<p>I've been told that an electron is somewhere within the space of $10^{-10}m$ and am supposed to find the uncertainty in its velocity.</p>
<p>Simply applying $m\Delta x \Delta v \geq \frac{h}{4\pi}$ results in $\Delta v \geq 5.79\times10^{10} m/s$. Now, this velocity is not approaching the speed of light, but I want... | g13446 | [
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0.04789179563522339,
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0.001811... |
<p>Please can someone provided me with academic literature (Journals/Books, titles & links) which discuss the current view on space time i.e. that there is not Infinitely many points of space-time? </p> | g13447 | [
0.006941033061593771,
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0.034925639629364014,
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<p>I have ground-level radiation data of solar incoming radiation from a radiometer (cosine collector) measured along the day. In the following plot you can see PAR irradiance (ie visible light) in Watts per square meter versus time of day (local time). AS usual for this type of sensor, radiation intensity varies with ... | g13448 | [
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0.021837912499904633,
0.08023223280906677,
0.02201106585562229,
0.06399568915367126,
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<p>Classical mechanics is a good approximation to special relativity, which is a good approximation to general relativity etc. I have heard that if <a href="http://en.wikipedia.org/wiki/String_theory" rel="nofollow">string theory</a>/<a href="http://en.wikipedia.org/wiki/M-theory" rel="nofollow">M-theory</a> is right, ... | g13449 | [
0.05414441227912903,
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0.023067878559231758,
-0.015432959422469139,
0.02616199105978012,... |
<p>I am reading Griffiths QM textbook and I got confused by the following identity:</p>
<p>How to prove from $$\frac{\partial \Psi}{\partial t} = \frac{i\hbar}{2m} \frac{\partial^2 \Psi}{\partial x^2} - \frac{i}{\hbar}V\Psi$$ to $$\frac{\partial \Psi^*}{\partial t} = -\frac{i\hbar}{2m} \frac{\partial^2 \Psi^*}{\part... | g13450 | [
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0.008355348370969296,
-0.0... |
<p>Is there the formula (if someone already has discovered it) or what is the algorithm (if a particular formula was not deduced), to calculate the critical pressure of thick-walled spherical shell $−$ the pressure which provokes buckling?</p> | g13451 | [
0.06614130735397339,
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0.12444654107093811,
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<p>The Yang-Mills action are usually given by $$S= \int\text{d}^{10}\sigma\,\text{Tr}\left(-\frac{1}{4}F_{\mu\nu}F^{\mu\nu}-\theta^{T}\gamma^{\mu}D_{\mu}\theta\right)$$</p>
<p>with the field strength defined as $F_{\mu\nu}=\partial_{\mu}A_{\nu}-\partial_{\nu}A_{\mu}-ig\left[A_{\mu},A_{\nu}\right]$
, $A_{\mu}$
being... | g13452 | [
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-... |
<p>Let us consider the following <a href="http://en.wikipedia.org/wiki/Thought_experiment">Gedankenexperiment</a>:</p>
<p>A cylinder <strong>rotates</strong> symmetric around the $z$ axis with <a href="http://en.wikipedia.org/wiki/Angular_velocity">angular velocity</a> $\Omega$ and a plane wave with $\mathbf{E}\text{,... | g13453 | [
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<p>I haven't seen any reference which explains these things and I am not sure of all the steps of the argument or the equations. I am trying to reproduce here a sequence of arguments that I have mostly picked up from discussions and I would like to know of references for the background details and explanations. </p>
<... | g13454 | [
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<p>Dirac once said that he was mainly guided by mathematical beauty more than anything else in his discovery of the famous Dirac equation. Most of the deepest equations of physics are also the most beautiful ones e.g. Maxwell's equations of classical electrodynamics, Einstein's equations of general relativity. Beauty i... | g13455 | [
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<p>In page 32 of Peskin & Schroeder, it is written: </p>
<blockquote>
<p>But if $j(x)$ is turned on for only a finite time, it is easiest to solve the problem using the field equation directly.</p>
</blockquote>
<p>I am wondering:</p>
<ol>
<li>How is it possible to "solve" the field equation at all? I thought ... | g13456 | [
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0... |
<p>The Hamiltonian for m(atrix) theory is given by
$$H=\frac{1}{2\lambda}\text{Tr}\left(P^{a}P_{a}+\frac{1}{2}\left[X^{a},X^{b}\right]^{2}+\theta^{T}\gamma_{a}\left[X^{a},\theta\right]\right).$$
Where $X^a$ are the $9$ bosonic $N\times N$ matrices and $\theta$ are a $16$-component matrix-valued spinor of $SO(9)$. (Give... | g13457 | [
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<p>Apologies in advance for what may be a stupid question from a layman. In reading recently about <a href="http://en.wikipedia.org/wiki/Quantum_entanglement" rel="nofollow">quantum entanglement</a>, I understood there to be a direct link between entangled particles, even at arbitrarily large distances. I'm wondering... | g13458 | [
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<p>As I have been studying electromagnetic theory, I have always been lead to confusion when trying to visualise the fields. Fortunately, the electric and magnetic fields are vector fields and also along the propagation direction they provide a 3-Dimensional Coordinate system. </p>
<p>However, in general to visualise ... | g13459 | [
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0.0439729169011116,
0.012221231125295162,
0.0275920107960701,
0.015... |
<p>Why should two sub-atomic (or elementary particle) - say electrons need to have identical static properties - identical mass, identical charge? Why can't they differ between each other by a very slight degree? Is there a theory which proves that?</p>
<p>Imagine an alien of size of order of Milky-way galaxy examinin... | g13460 | [
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<p>Firstly, sorry for any silly mistakes or improper use of this website - this is my first time using it! </p>
<p>I am trying to use Excel to model the flight of the Apollo 11 Saturn V rocket using the real values from the mission evaluation report.
However, I can't seem to get the right acceleration. It is always t... | g13461 | [
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0.013104042038321495,
0.04539470747113228,
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<p>In a dc circuit work done by battery=QV while energy stored in capacitor =(QV)/2 loss in energy=(QV)/2
While a capacitor in ac circuit has a no power loss.why is it so? Shouldn't heat be lost in ac circuit capacitor too while charging.</p> | g13462 | [
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<p>This just blew my mind away! I was watching a video about imagining the fourth dimension and the narrator said that little line. Can some people elaborate on this. Also please keep it simple not too complicated. Thank you!</p> | g420 | [
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<p>How can I find the magnetic interference a stationary 35000 kg block of 100% pure iron would have on a magnetic compass and what the drop off rate of the interference would be. </p>
<p>So if said 35000 kg block of iron was 1 meter away from the compass, 100 meters away, or 1000 kilometers way I would like to calcu... | g13463 | [
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<p>If we have a Hilbert space of $\mathbb{C}^3$ so that a wave function is a 3-component column vector
$$\psi_t=(\psi_1(t),\psi_2(t),\psi_3(t))$$
With Hamiltonian $H$ given by
$$H=\hbar\omega
\begin{pmatrix}
1 & 2 & 0 \\
2 & 0 & 2 \\
0 & 2 & -1
\end{pmatrix}$$
With
$$\psi_t(0)=(1,0,0)^T$$... | g13464 | [
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0.013684763573110104,
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... |
<p><strong>BACKGROUND</strong></p>
<p>So far I understood that the <a href="http://en.wikipedia.org/wiki/Hierarchy_problem" rel="nofollow">hierarchy problem</a> was the large difference between the gravitational scale, $M_{pl}\sim 10^{18}\; [GeV]$, compared with the electroweak scale, $M_{ew}\sim 10^3\;[GeV]$.</p>
<p... | g13465 | [
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0.010392392985522747,
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0.014820861630141735,
0.012038356624543667,
0.0373704... |
<p>A massless rod of length $L$ attached to mass $m$ and with axle to cart of mass $M$. The cart has a shape of equilateral triangle (edge $L$). the cart is at rest and its center of mass is above $x=0$ and a rod is perpendicular to the ground. the cart is free to move without friction. at time t=0 the mass $m$ is rele... | g13466 | [
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0.0006167091778479517,
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0.06377444416284561,
-0.... |
<p>In <em>M. Veltman's Diagrammatica</em>, appendix E, one can find the full Standard Model lagrangian. Some sectors (e.g fermion-Higgs and weak sectors) contain so-called Higgs ghosts $\phi^+,\phi^-$ and $\phi^0$. </p>
<blockquote>
<p>Are Higgs ghosts Faddeev-Popov ghosts? </p>
</blockquote>
<p>If so, </p>
<bloc... | g13467 | [
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<p>Suppose a projectile is launched from the Earth's surface with initial velocity $v_0$ well below speed of light and initial angle $\theta_0$ with respect to the vertical line perpendicular to the Earth's surface. Omitting Earth's rotation, but knowing that Earth is not flat (as in the real world), what is the maximu... | g13468 | [
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<p>This is the problem from our Physics textbook : </p>
<blockquote>
<p><em>A player throws a ball upwards with an initial speed of 29.4 m s–1.
(a) Choose the x = 0 m and t = 0 s to be the location and time of the ball at its highest point, vertically downward direction to be the positive direction of
x-axis, an... | g13469 | [
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<p>From this <a href="http://physics.stackexchange.com/questions/19632/how-much-electric-charge-do-electromagnetic-waves-carry"><strong>question</strong></a>, I've noted that an electromagnetic field carries <em>no electric charge</em> but it has two components:</p>
<ul>
<li>Electric field</li>
<li>Magnetic field</li>... | g13470 | [
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<p>I have been learning gauss's law in capacitor recently, recently I come up with this problem that I couldn't solve myself. If we have a capacitor,and a dielectric medium with half the volume between the plates, the permittivity of the dielectric is epsilon.Find the electric field inside the dielectric.
The second o... | g13471 | [
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... |
<p>To the best of my knowledge thermal fluctuations are responsible for washing out any effective magnetization, once the external field is switched off. Since thermal fluctuations need some time to drive the system back to random orientation, what would be the time scale for this process? Is it of the order of 200 ps?... | g13472 | [
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<p>I was discussing with my colleagues why it feels easier to walk up an escalator when it is moving. My natural assumption was that the movement of the escalator imparts some extra acceleration on the rider that helps to move up the stairs. But my colleagues insisted that this was nonsense, and that the affect is pure... | g13473 | [
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<p>If you balance a pencil of length $d$ on its tip, and let it fall, how do you compute the final velocity of its other end just before it touches the ground?</p>
<p>(Assume the pencil is a uniform one dimensional rod)</p> | g13474 | [
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<p>When I learned classical Markov process, I noticed some similarity of quantum process and Markov process, and the only difference of them is between probability and probability amplitude whose modulus square represents a probability.</p>
<p>I show the some similarity here. The Schordinger's equation gives us the re... | g13475 | [
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<p>Suppose I put a pendulum of metal ball and very thin rope in highest achievable vacuum. What would keep it from not swinging forever?</p> | g301 | [
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<p>I have just started learning optics at school and my teacher derived the lens and mirror formulas. While doing so, she applied the sign convention for u,v and f and arrived at the final expression. However, while solving problems using the mirror formula why do we again apply sign convention for the given values of ... | g702 | [
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<p>With respect to waves traveling through a diffraction grating, we have an equation like this one: $$d_s\sin(\theta) = m\lambda.$$</p>
<p>Where $d_s$ is the distance between slits in the grating, $\theta$ is an approximate angle at which the waves bend through each slit of the grating, $\lambda$ is the wavelength of... | g13476 | [
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<p>The real question was: <strong>A proton is trapped in an infinitely deep well of 1*10^-14m.</strong> I suppose that is unimportant as that should only help us decided the limits of our integration. What I'm worried about is the second part of the question. <strong>"The proton is in the first excited state."</strong>... | g13477 | [
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<p>It is given that the angular size of the Sun as viewed from Earth is $0.533^\circ$, the distance of the Moon from Earth at perigee is $3.633\times 10^5$ km, and the mean radius of the Moon is $1737.1$ km. </p>
<p>Suppose that the perigee of the Moon is receding from Earth at a uniform rate of $4$ cm/year. Estimate ... | g13478 | [
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<p>That I could create as a classical mechanics class project? Other than the classical examples that we see in textbooks (catenary, brachistochrone, Fermat, etc..)</p> | g13479 | [
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<p>I am wondering whether the five$^1$ units of the natural unit system really is dictated by nature, or invented to satisfy the limited mind of man?
Is the number of linearly independent units a property of the nature, or can we use any number we like? If it truly is a property of nature, what is the number? -five? ca... | g13480 | [
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<p>I fail to understand the true difference between EMR and electric and magnetic fields. When current flows, there is an electric field due to the electron flow and a magnetic field, however no EMR (Save blackbody radiation from the wire) is emitted. Then how can radio broadcasts function if magnetic fields only are e... | g13481 | [
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<p>How are Monte Carlo simulations used in experimental high energy physics? Particularly in studying detectors limitations (efficiencies?) and data analysis.</p>
<p>I will appreciate giving a simple example to clarify how MC is used if the question is too technical to have a simplified answer</p> | g13482 | [
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<p>I believe that no real objects are actually (<em>exactly</em>) 1 meter long, since for something to be 1.00000000... meters long, we would have to have the ability to measure with infinite precision. Obviously, this can be extended to any units of measurement. Am I wrong?</p> | g13483 | [
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<p>The Rayleigh-Lamb equations:</p>
<p>$$\frac{\tan (pd)}{\tan (qd)}=-\left[\frac{4k^2pq}{\left(k^2-q^2\right)^2}\right]^{\pm 1}$$</p>
<p>(two equations, one with the +1 exponent and the other with the -1 exponent) where</p>
<p>$$p^2=\frac{\omega ^2}{c_L^2}-k^2$$
and
$$q^2=\frac{\omega ^2}{c_T^2}-k^2$$</p>
<p>show ... | g13484 | [
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0.0... |
<p>in the formula </p>
<p>$$dB = \frac{\mu_0l ~|dl \times r|}{4 \pi r^3} $$</p>
<p>and the image<br>
<img src="http://i.stack.imgur.com/NVNYK.png" alt="enter image description here"></p>
<p>where dl is in y-z plane and dB is in x-y plane. the ring conductor is in y-z plane carrying current I in direction as mentio... | g13485 | [
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<p>Question:</p>
<blockquote>
<p>A wheel starts is spinning at $27\text{ rad/s}$ but is slowing with an angular
acceleration that has a magnitude given by $\alpha(t) = (3.0\;\mathrm{rad/s^4})t^2$. It stops in a time of: $\qquad$ ?</p>
</blockquote>
<p>I happened to guess $3.0\text{ s}$ and it turned out to be r... | g13486 | [
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<p>In dimensional regularization, we must shift the dimensionless coupling $g$ by the renormalization scale $\mu$ (which has unit mass dimension):
\begin{equation}
g \rightarrow \mu^{4-d} g \tag{1}
\end{equation}
This is done to ensure that the action will have the correct dimensions.</p>
<p>Apparently, $\mu$ will not... | g13487 | [
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<p>The smallest particles of the universe (or the smallest part of the smallest particles of the universe) must have infinity density. But if it have infinity density, you can calculate mass of one of these particles as infinity - so if any thing would composed of these particles, would it have infinity mass. How is it... | g13488 | [
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<p>We are told that they can only terminate on surfaces, grain boundaries or other dislocations but we are not told why they can't terminate inside the crystal.</p> | g13489 | [
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<p>I'm trying to follow the Feynman lectures and I'm stuck on a particular piece. Let me frame it for you before I ask my question. Nobody does it better than the author himself,</p>
<blockquote>
<p>we must find out how a particular particle moves when the angular velocity is such and such. To do this, let us take a... | g13490 | [
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<p>If Electricity and magnetism are the same viewed from a different reference frame (they are the same force as unified by maxwell) then is electricity medium dependant? I came to this question when trying some experiment with two wires close to each other where I place between them non-conductor mediums such as: pap... | g13491 | [
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<p>Or can they just be used as an interpolation points and use some other "transported property" which are just evolved and propagated from boundary conditions like for eg. heat conduction through a solid metal bar. It seems to be possible, but isn't clearly elaborated. The force computation step is always used for flu... | g13492 | [
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<ol>
<li><p>What is the <a href="http://en.wikipedia.org/wiki/Moduli_%28physics%29" rel="nofollow">moduli space</a> of a QFT? </p></li>
<li><p>What does it mean exactly that there are different inequivalent vacua? </p></li>
<li><p>Can someone give a precise definition of the moduli space, and some easy examples? </p></... | g13493 | [
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<p>I've just answered <a href="http://physics.stackexchange.com/questions/81896/dipping-a-dyson-ring-below-the-event-horizon">Dipping a Dyson Ring below the event horizon</a>, and while I'm confident my answer is correct I'm less certain about the exact consequences. To simplify the situation consider a diatomic molecu... | g13494 | [
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<p><strong>Update.</strong> As my previous figure had conceptual mistakes I decided to change the picture to another, more instructive.</p>
<p>After a long time I came back to try to understand an article on the Ising model.
The review article is <a href="http://arxiv.org/pdf/math/9907186.pdf" rel="nofollow">Percolati... | g13495 | [
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<p>So I need to find the possible energies and the probabilities of these using the eigenvalues of a Hamiltonian.</p>
<p>Once I obtain the eigenvalues, are those the energies E_n in and of themselves?
Or do they simply give me the n values, i.e. n = 1, 2, 3, that I would then plug in to the equation</p>
<p><img src="... | g13496 | [
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... |
<p>I have heard that the Morse potential equation</p>
<p>$$\tag{1} -\frac{\hbar ^{2}}{2m} \frac{d^{2}}{dx^{2}}y(x)+ae^{bx}y(x)-E_{n}y(x)=0 $$ </p>
<p>is related to the two dimensional equation on the Poincare half plane with a constant magnetic field</p>
<p>$$\tag{2} -\frac{y^{2}}{2m}( \partial _{x}^{2}+\partial _{... | g13497 | [
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<p>At my university the second half of a year long sequence in basic calculus based physics focuses on electrodynamics and magnetism. I am wondering what is the significance of these topics to physics in general? How does it relate/prepare you to study the more advanced subjects like quantum mechanics and the like? </p... | g13498 | [
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<p>Application of mechanical stress to a piezo crystal generates a charge. </p>
<p>Quoting from wikipedia, a 1 cm3 cube of quartz with 2 kN (500 lbf) of correctly applied force can produce a voltage of 12500 V.</p>
<p>What happens when the crystal is exposed to a vacuum? Is the converse true? If the structural deform... | g13499 | [
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0.0625031515955925,
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<p><a href="https://en.wikipedia.org/wiki/Collision_frequency">Collision frequency</a> for particles in gases is well known, and <a href="https://en.wikipedia.org/wiki/Collision_theory">collision theory</a> is used to derive chemical reaction rates in gases, (and particles in liquid solutions as well). Using the mean v... | g13500 | [
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<p>If we have a harmonic oscillator and look at it on small scale the energy is quantized and we can calculate the different eigenstates. In general the energy eigenvalues are given by $$E_n = \left(\frac{1}{2}+n\right) \hbar \omega$$</p>
<p>Even if we can bring this system at $T=0$ into it's ground state, there will ... | g13501 | [
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0.02449186146259308,
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0.057... |
<p>What's the state of <a href="http://en.wikipedia.org/wiki/Star" rel="nofollow">stars</a>? I'm not pretty sure whether the stars are stationary or rotating. For instance, if they are not rotating what makes them to be stable?</p> | g13502 | [
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0.017631327733397484,
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<p>Say I build a perfect rectangle. Side lengths $l_1$ and $l_2$ and perfect right angles. I am on earth and the metric is given by the Schwarzschild metric. Setting $dt=0$ leads to the spatial Riemannian metric
$$\mathrm{d}s^2=\left(1-\frac{r_s}{r}\right)^{-1}\mathrm{d}r^2+r^2\left(\mathrm{d}\theta^2+\sin^2\theta \,\m... | g13503 | [
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-... |
<p>How could one charge a spherical capacitor with a battery or any other emf source?</p> | g13504 | [
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<p>I know that there are two different ways to write the Bragg condition namely
$k^2=(k+G)^2$ and $n\lambda=2d\sin \theta$ where $G$ is a reciprocal lattice vector, $\lambda$ is the wavelength and $d$ is the distance between planes. I am also familiar with the equivalence of both and the intuitive derivation of the sec... | g13505 | [
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0.012991986237466335,
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0.0730520486831665,
-0.03591114655137062,
... |
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