question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>What does it mean if a body has <a href="http://en.wikipedia.org/wiki/Kinetic_energy" rel="nofollow">kinetic energy</a>?</p>
<p>Does it mean that the momentum vectors of each particle of that body has the same direction?</p>
<p>What about <a href="http://en.wikipedia.org/wiki/Angular_momentum" rel="nofollow">angul... | g17748 | [
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<p>I know that the maximum (useful) magnification is limited by the diffraction limit, but I was not able to find numbers for the highest useful magnification factors using modern large telescopes.</p>
<p>How much magnification is possible, e.g. using the E-ELT?</p> | g17749 | [
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<p>In the experiment, gases are put at low pressure inside the discharge tube. Now the issue that arises is a very simple one.
<a href="http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::100%::100%::/sites/dl/free/0072512644/117354/01_Cathode_Ray_Tube.swf::Cathode%20Ray%20Tube" rel="nofollow">http://high... | g17750 | [
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<p>Flow rates of liquids could be easily measured with a stopwatch and a known volume container. But gases, if entrapped in a container will create a back pressure, and may lead to decreased flow.</p>
<p>I wonder how they measure the quantity of gases generated by a reaction or flow rate of fluids in turbines, etc., w... | g17751 | [
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<p>I'm studying Chiral Perturbation Theory ($\chi PT$) from Scherer's <a href="http://arxiv.org/abs/hep-ph/0210398" rel="nofollow"><em>Introduction to Chiral Perturbation Theory</em></a>. </p>
<p>What I am currently having some trouble understanding are two things:</p>
<ol>
<li>The quark condensate. What is this and ... | g17752 | [
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<p>Working on electrical engineering but thus far, the physics stack has proven to be a better place to read and ask questions in order to develop a better overall understanding. </p>
<p>I am currently waist deep in <em>semi-conductor theory</em>. I am not confused about how a conductor gains the same potential as the... | g17753 | [
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<p>Cyclotron radiation is radiation emitted by a charged particle being bent by a magnetic field. The only difference between cyclotron and synchrotron radiation is that the latter occurs at relativistic speeds. Is this right?</p>
<p>Now, AFAIK, synchrotron radiation is artificially produced by channeling the accelera... | g17754 | [
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<p>In a <a href="http://www.theguardian.com/science/2014/may/18/matter-light-photons-electrons-positrons" rel="nofollow">recent article</a> about creating electron-positron pairs by colliding photons in a laboratory, <a href="http://www2.physics.ox.ac.uk/contacts/people/seryi" rel="nofollow">Andrei Seryi</a>, director ... | g17755 | [
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<p>I can't find the precise definition of what is the orientation of a GaAs lattice. Being the superposition of two fcc lattices (one of Ga, the other of As), I would think that it is the direction of the closest Ga atom to any As atom of the structure. Is it right?</p> | g17756 | [
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<p>So I know:
$$[\sigma_{I},\sigma{j}] = 2i \epsilon_{ijk} \sigma_{k}$$
So two products of this should give us the Lorentz group:
$SO(4) = SU(2) \times SU(2)$</p>
<p>Where $SO(4)$ has 3 Lie algebra which can be expressed as one by denoting:
$$J_{I}^{\pm} = \frac{1}{2} (J_{I} \pm ik_{I})$$</p>
<p>This gives two Lie al... | g17757 | [
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<p>Look at this image:</p>
<p><img src="http://i.stack.imgur.com/3i6dy.png" alt="Electromagnetic wave"></p>
<p>I wonder if the electric field is from the induction field from a vibrating electron or the radiation field? If it is from the radiation field, as I suppose, than can someone explain why they are perpendicul... | g17758 | [
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<p>1-Why the antenna of the radio of cars is located outside the car and not inside?</p>
<p>2-If the answer to 1 is because that cars are like Faraday cages then how come my cell phone can receive signal inside the car?</p>
<p>3-To receive a strong tv/radio signal the antenna must be oriented in a specific way. Why t... | g17759 | [
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<p>I am quite familiar with use of Wick rotations in QFT, but one thing annoys me: let's say we perform it for treating more conveniently (ie. making converge) a functional integral containing spinors; when we perform this Wick rotation, in a way we change the metric to (-,+,+,+) to (+,+,+,+), so the invariant group is... | g17760 | [
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<p>The light source: 190 high power LEDs in <a href="http://en.wikipedia.org/wiki/Near_Infrared" rel="nofollow">NIR</a>.
I have the datasheet of the LED.</p>
<p>I want to make a graph showing the spatial distribution, and to measure the intensity of the beam on the whole field of view.</p>
<p>Actually, I used to work... | g17761 | [
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<p>According to Noether's theorem, global invariance under $SU(N)$ leads to $N^2-1$ conserved charges. But in QCD gluons are not conserved; color is. There are N colors, not $N^2-1$ colors. Am I misunderstanding Noether's theorem?</p>
<p><strike>My only guess (which is not made clear anywhere I can find) is that there... | g17762 | [
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<p>The motivation for this question comes directly from <a href="http://physics.stackexchange.com/a/56831/8521">this thread</a>. The proposition is that the color of something changes how fast it cools (note: specifically the rate of cooling, not taking into account the change in heat absorption). For example: <stron... | g17763 | [
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<p>Let the pure states be in superposition of horizontal and vertically polarized basis states. They are arriving at the point detector one at a time. So, a pure state is $|\Psi\rangle = \alpha|V\rangle + \beta|H\rangle$. The formula for counting rate is as follows, $$G({\bf r},t) \propto \langle \Psi_F^{(0)}|\hat{E}^... | g17764 | [
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<p>Suppose the state of the particle is given as follows:</p>
<p>$$ |\psi_{(t)}\rangle = \frac{1}{\sqrt2} \left( e^{-\frac{i\omega t}{2}} |0\rangle + e^{-\frac{3i\omega t}{2}} |1\rangle \right) $$</p>
<p>Where the wavefunctions are: $\phi_0 = \left( \frac{1}{a^2\pi} \right)^{\frac{1}{4}} e^{-\frac{x^2}{2a^2}} $ and $... | g17765 | [
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<p>So this is a rather simplistic understanding but I want to know if it's fundamentally correct:</p>
<p>We have nothing which we'll represent as $0$.</p>
<p>Then we need a Universe which we can represent as any number of parts that sum to $0$</p>
<p>$$ 0 = -1 + 1 $$</p>
<p>In this way we can take $0$ and make a "U... | g17766 | [
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<p>I dont undestand how to apply a phase shift gate to a qubit. By example how to map $|\psi_0\rangle = \cos (30^\circ) |0\rangle + \sin (30^\circ) |1\rangle$ to $|\psi_1\rangle = \cos(-15^\circ) |0\rangle + \sin(-15^\circ) |1\rangle$</p> | g17767 | [
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<p>I wanted to know, if particles turn out to be excitions in quantum fields, does that mean path intergrals is how nature really works in reality as in the Hawking/Stenger interpretation? or can particles still be field quanta i.e excitions/ ripples in fields and yet nature not be how hawking and stenger describe it?<... | g549 | [
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<p>Suppose there are N non-interacting classical particles in a box, so their state can be described by the $\{\mathbf{x}_i(t), \mathbf{p}_i(t) \}$. If the particles are initially at the left of the box, they can eventually occupy the whole box according to the Newtons law. In this case, we call the gas expand and this... | g17768 | [
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<p>I have a doubt regarding whether the trace of the vector heat kernel on a product space factorizes into the corresponding heat kernel traces on each manifold in the product space. I know this holds for the spin-0 as well as spin-1/2 cases, but I am not sure about the spin-1 case. Can somebody please help me out in t... | g17769 | [
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<p>From my understanding objects do not fall but are pulled to the earth from gravity.</p>
<p>With this in mind, I can't understand why if helium filled balloons are not pulled by gravity then shouldn't they float in place (or drift like objects in space with no gravity) rather than actively move away from the earth?<... | g17770 | [
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<p>Conceivably it expands with the speed of light. I do not know, but curious, if there is an answer. At what velocity, does our universe expand?</p> | g719 | [
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<p>I'd like to know how a linear Gaussian conditional probability distribution can be represented to a canonical form. </p>
<p>For example, let X and Y be two sets of continuous variables, with |X| = n and |Y| = m. Let</p>
<p>p(Y | X) = <em>N</em>(Y | <em>a</em> + BX; C)</p>
<p>where <em>a</em> is a vector of dimens... | g17771 | [
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<p>The community college where I teach has some nice old Michelson interferometers. There appear to be a bunch of versions of these that used to be sold (may still be sold?) which were all probably knock-offs of some manufacturer's original model. Ours are Cenco 71990-549, and are identical to the one in the photo <a h... | g17772 | [
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<p>Ok, need a little help for part (b) of the following <a href="http://books.google.com/books?id=hZWVEPgFM5kC&pg=PA364&lpg=PA364&dq=%22a%20gyroscope%20in%20the%20form%20of%20a%20symmetric%22&source=bl&ots=-p2AJ8O7Fx&sig=Som1zPbambx7KIYaz5rCxxw15Ww&hl=en&sa=X&ei=l15fUquJI6zi4AO0tYH4B... | g17773 | [
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<p>Back in 1993 I derived the following equations to calculate projectile velocity and barrel pressure. Recently, I have noticed that I need to <strong>double</strong> the calculated results in order to obtain real word results.</p>
<p>I need some help to find out why I have to <strong>double</strong> the derived resu... | g17774 | [
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<p>Very simple question, and frankly quite a silly one, but I'm currently writing a lecture for secondary school kids and I'd love to tell them how far the Large Hadron Collider could fire a proton.</p>
<p>The talk is actually about space, so what I'd really like to know is how would the velocity of the proton would c... | g17775 | [
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0.016916679218411446,
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0.0... |
<p>The double-slit experiment shows fringes on a screen. Closing one of the slits there is still an interference pattern on the screen behind the slit. Making the slit wider we still see fringes between the shadow and the exposed area. Even with single photons or electrons.</p>
<p>On the other hand, using a polarisati... | g17776 | [
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<p>Is there a formula or equation relating $\langle E\rangle$ and $\langle M\rangle$ (average spin per site) and $\langle E^2\rangle$ to temperature $T$ for the square lattice Ising model at zero magnetic field? I have done some simulations and know what the graphs are supposed to look like approximately, but is there ... | g17777 | [
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<p><a href="https://en.wikipedia.org/wiki/Internal_combustion_engine#Measures_of_engine_performance" rel="nofollow">This</a> Wikipedia article states that:</p>
<blockquote>
<p>Most steel engines have a thermodynamic limit of 37%.</p>
</blockquote>
<p>Is it correct? If so then it is not clear where this number comes... | g17778 | [
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<p>thanks to the answers I received to my previous questions, I could derive correctly an elegant partition function for my problem which <em>resembles</em> a second quantized model taking the particles to be Bosons. The related Hamiltonian for every $i$th ensemble is there:
$$H_i=\sum_{q=1}^\infty \gamma_{q,i} \; \lam... | g17779 | [
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<p>The objective is to derive the gravitational redshift ONLY from the Einstein's equivalence principle (E.E.P.), without using the whole theory of Relativity.</p>
<p><strong>This is the standard "informal" derivation of the gravitational redshift</strong>
(For example Carroll in his book follows this way): </p>
<p>C... | g17780 | [
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<p>I have a very naive question : given a tight-binding model (with nearest-neighbor hoping) on a lattice defined by a Bravais lattice with a number of sublattices (for instance the honeycomb lattice is a triangular lattice with two sublattices), why is there a band associated with each sublattice ? For instance when a... | g17781 | [
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<p>How are planets positions described in the space and in respect to what? </p>
<p>For example is Sun the origo and right now at this moment Earth has [coord_X, coord_Y, coord_Z]? or maybe [lng, lat]? </p>
<p>Edit1:
I found out that the universe has no center point. Any chose point in the universe can be a center p... | g17782 | [
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<p><em>Random matrix theory</em> pops up regularly in the context of dynamical systems.</p>
<p>I was, however, so far not able to grasp the basic idea of this formalism. Could someone please provide an instructive example or a basic introduction to the topic?</p>
<p>I would also appreciate hints on relevant literatur... | g17783 | [
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<p>The Berry curvature of the $n^{\mathrm{th}}$ eigenstate of Hamiltonian $H$ for the vector of external parameters $\vec{R}$ can be derived in part by writing the following two lines:</p>
<p>$B^n(\vec{R}) \equiv \nabla \times A^n(\vec{R}) = -Im \left[ \left< \nabla n(\vec{R}) | \nabla n (\vec{R}) \right> \right... | g17784 | [
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<p><img src="http://i.stack.imgur.com/VwmZU.png" alt="enter image description here">Suppose we are in a satelite revolving around the earth with a velocity equal to orbital velocity. Now if we release a spoon from the satelite then will it reach the earth or will it just revolve around the earth like the satelite with... | g17785 | [
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<p>I understand that water flows because of height difference and current flows because of potential dfference. Now, in this analogy, I can understand height but I fail to realise what potential is. Is it the number of electrons? Say, A has 10 electrons, B has 20 and C has 100 electrons. So, can I say AC has more poten... | g17786 | [
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<p>In the Twin Paradox two twins initially at rest in the same reference frame are separated and take different journeys through spacetime. Eventually they are reunited. What is the condition for the reunion?</p>
<p>In Newtonian physics, they are reunited when they have the same spacetime coordinates. From a Special R... | g17787 | [
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<p>Let's assume an averaged sized man (1.8 meters height 80 kg) who's sky-diving from a 5000 m height.</p>
<p>Let's also assume he's using tight clothes and no parachute.</p>
<p>The idea is:</p>
<p>Is it possible for him to survive the fall if he tries to get the maximum velocity he can get by free falling and later... | g17788 | [
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<p>I need the dielectric constant of water from $10^{-2}$ Hz to $10^4$ Hz. As stupid as it may seem, I cannot find much info. I've googled for days. All I can find is close to GHz. And the only info close to Hz, ($100$ Hz) shows a great variation. A relative dielectric constant at $100$ Hz of about $4000$. So, I cannot... | g17789 | [
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0.002931... |
<p>In non-relativistic mechanics, the conserved quantities found using Noethers theorem in Lagrangian mechanics are the same as those quantities which are conserved under canonical commutation with the Hamiltonian in Hamiltonian mechanics.</p>
<p>Does this carry over straight-forwardly to relativistic mechanics?</p> | g17790 | [
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<p>I'm interested in learning about the classical coupling of the Higgs Field to Electromagnetism. There are numerous sources explaining the Higgs mechanism quantum mechanically, i.e. <a href="http://physics.stackexchange.com/questions/17944/how-does-the-higgs-mechanism-work/17964#17964">How does the Higgs mechanism wo... | g17791 | [
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<p>I am having hard time understanding how the charge carriers (electrons and holes) are able to move thermal energy.
I am on a high school physics level, so I will probably have a hard time understanding it if there are advanced quantum physics involved. </p> | g17792 | [
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<p>I typically listen to NPR in the morning from a clock radio next to my bed. There are days when just moving my body, even my arm or leg, is enough to cause interference with the radio to dramatically decrease the volume, or it appears as if I lost the radio station altogether. I know that my body acts like an antenn... | g17793 | [
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<p>In $\mathrm{AdS}_5$/$\mathrm{CFT}_4$ the AdS radius $R$ is determined in terms of the string length by the gauge theory t'Hooft parameter as follows
\begin{equation}
\frac{R}{l_{\rm s}} \sim \lambda^{1/4}
\end{equation}
Consequently large t'Hooft parameter corresponds to dropping derivative corrections to the space... | g17794 | [
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<p>A while back I read about the super Kamiokande detector detected a large neutrino flux and then several hours later a supernova was seen. Anyone know of this with sources? I don't recall the source at the moment. </p> | g17795 | [
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<p>My Question is how do electrons get energy/lose energy to jump up or down an orbital as in a stationary orbit they do not gain energy and their energy is finite?</p> | g17796 | [
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<p><strong>Background</strong>: </p>
<p>It is my understanding that the <a href="http://en.wikipedia.org/wiki/Higgs_boson" rel="nofollow">Higgs Boson</a> is a fluctuation of the Higgs field. It also is not very stable and decays into a plethora of other particles. If all other particles interact with the Higgs field "... | g17797 | [
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<p>A point charge $q$ of mass $m$ is released from rest at a distance $d$ from an infinite grounded conducting plane. Show that the charge hits the plane after an amount of time given by:</p>
<p>$ \Delta t= \frac{\pi d} {q} \sqrt{2\pi\epsilon_0md} $</p>
<p>I can't seem to start this one. I'm assuming I need to start ... | g17798 | [
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<p>Referring to unidimensional motion, it is obvious that it doesn't always make sense to write the speed as a function of position. Seems to me that this is a necessary condition to derive formulas like:</p>
<p>$$v^2=v_0 ^2 +2\int_{x_0}^{x}a\cdot dx$$</p>
<p>In fact, in the first step of the demonstration (the one I... | g946 | [
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<p>I am using Mathematica to construct a matrix for the Hamiltonian of some system. I have built this matrix already, and I have found the eigenvalues and the eigenvectors, I am uncertain if what I did next is correct: I took the normalized eigenvectors, placed them in matrix form, and did matrix multiplication with th... | g17799 | [
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<p>What are the experimental (indirect) evidence for the cosmic neutrino background? Where can I read more about this?</p>
<p>The discussion on the <a href="http://en.wikipedia.org/wiki/Cosmic_neutrino_background" rel="nofollow">wikipedia page</a> about the C$\nu$B seems to me to be more about the evidence of the num... | g17800 | [
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<p>I've been watching Susskind's lectures on Quantum Entanglement, and something he said regarding (non-)commuting projection operators confused me.</p>
<p>Consider two subspaces {$|a>$} and {$|b>$} of Hilbert space, with operators $K$ and $L$ for which:</p>
<ul>
<li>$K |a> = \lambda |a> (1)$</li>
<li>$L ... | g17801 | [
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0.00908849760890007,
0.036... |
<p>Heisenberg's uncertainty principle is one of the most fundamental principles on which quantum mechanics is based on. But it is also one of the most confusing laws we encounter. My doubt is whether the uncertainty is due to observation error or due to dual nature of matter ?</p>
<p>Dual nature of matter states that ... | g17802 | [
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<p>I have had this question for some time now. Hopefully someone can answer it.</p>
<p>I know that the <a href="http://en.wikipedia.org/wiki/Boltzmann_equation" rel="nofollow">Boltzmann equation</a> is widely regarded as a cornerstone of statistical mechanics and many applications have been explored with a linearized ... | g17803 | [
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<p>Reading about bands dispersion, I came across the following (<a href="http://books.google.com.sa/books?id=NEEX9JLtdVkC&pg=PA172&lpg=PA172&dq=dispersion%20of%20oxygen%202p%20bands%20which%20is%20less%20than%203%20ev&source=bl&ots=Ubfc5oaqYJ&sig=4J42-57viUbpd-IDB-9oGthuyQ8&hl=en&sa=X&am... | g17804 | [
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<p>In Peskin and Schroeder's chapter 12 about the renormalization group, it is stated that the parameter $\rho_m=m^2/M^2$, where $m$ is the mass and $M$ is the renormalization scale, is proportional to $T-T_c$. But this assertion is not derived in any detail, except for a handwaving one-line explanation "$\rho_m$ is ju... | g17805 | [
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<p>As a student in a highschool physics class, my teacher has repeatedly told me that photons are massless. Yet, I have also heard from other sources that photons have momentum. If photons were to have momementum, that would mean that they have mass as according to p = mv.</p>
<p>Do photons really have mass?</p>
<p>A... | g195 | [
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<p>Can the <a href="http://www.nature.com/nphys/journal/v6/n4/full/nphys1629.html" rel="nofollow">gamma ray bursts connected to a new supernova</a>
prevent the black hole from forming?</p>
<blockquote>
<p>Quoting the abstract of the linked reference "...has become clear that probably all long GRBs are associated wi... | g17806 | [
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<p>Let $|\Psi_0\rangle$ be an eigenstate of $H_0$ with energy $E_0$ and let the 'interacting' Hamiltonian be $H=H_0 + gV$, where $g$ is a coupling constant and $V$ the interaction term. We define a Hamiltonian $H_\epsilon=H_0 + e^{-\epsilon |t|}gV$ which effectively interpolates between $H$ and $H_0$ in the limit $\eps... | g17807 | [
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<p>I have been looking, unsuccessfully, online for academic problems involving the <a href="http://www.google.com/search?as_q=Nilsson+nuclear+hamiltonian" rel="nofollow">Nilsson nuclear hamiltonian</a>. I understand the nature of the terms in the equation, but have never seen actual calculations from given data. Does a... | g17808 | [
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<p>This is intended to be a fun question. Calorimetry used for calculating the heat generated from chemical changes has been around for centuries, however, I suspect the process for calculating food calories is much more complicated. Can anybody provide a clear succinct, knowledgable answer? Although I will accept a... | g17809 | [
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<p>The question is: How to calculate the energy of electrostatic field of a newly created particle.</p>
<p>The <a href="http://en.wikipedia.org/wiki/Electric_potential_energy#Energy_stored_in_an_electrostatic_field_distribution" rel="nofollow">usual formula</a> involves integration <em>'all over space'</em>.
According... | g17810 | [
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<p>I am studying a book of quantum computing and the author gives an example of a four qubits separable! He writes: </p>
<blockquote>
<p>Let $\left|ψ\right> = \frac 1 2(\left|00\right> + \left|11\right> +
\left|22\right> + \left|33\right>) = 1/2 \, (\left|0000\right> +
\left|0101\right> + \l... | g17811 | [
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<p>So, I'm trying to find the largest radius of a needle before it ends up sinking, and I know that it's a balance of needle weight vs surface tension. However, I'm not really sure how the surface tension force is defined.</p>
<p>In a lot of resources, I see the surface tension force define as gamma, which is the for... | g17812 | [
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<p>I would like to ask what happens if an atom exposed to a very high temperature - say millions of degrees (Kelvin). Can we use heating to separate electrons from their nucleus? And what happens to the nucleus if its electrons are stripped off?</p>
<p>Thank you,</p> | g17813 | [
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<p>I'm going to start my graduate studies in theoretical physics. My supervisor wants me to work on quantum gravity. He gave me the liberty to chose a particular approach to Quantum gravity (Excluding string theory, he does not like string theory). </p>
<p>So I'm thinking which approach to Quantum gravity should I cho... | g17814 | [
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<p>Say a planet (mass $m$) is orbiting a star (mass $M$) in a perfect circle, so it is in circular motion.</p>
<p>$F=ma$ and the gravitational force between two masses $F=\frac{GMm}{r^2}$ so</p>
<p>$\frac{GMm}{r^2}=ma$</p>
<p>$\frac{GM}{r^2}=a$</p>
<p>And in circular motion $a=\frac{v^2}{r}$ so</p>
<p>$\frac{GM}{r... | g17815 | [
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<p>I apologize in advance if this question is deemed too general or too similar to <a href="http://physics.stackexchange.com/questions/4471/why-f-ma-and-not-f-ma">this</a> and <a href="http://physics.stackexchange.com/questions/4102/why-are-only-derivatives-to-the-first-order-relevant">this</a> question.</p>
<p>How wo... | g17816 | [
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<p>Calculate the rms speed of diatomic Nitrogen ($N_2$) at an altitude of $600$ km, where the temperature is $1500$ K.</p>
<p>I'm confused because only an altitude and a temperature is given, and I feel like I need the mass if the Nitrogen to complete the problem.</p>
<p>$v_{rms} = \sqrt{\frac{3K_bT}{m}}$</p> | g17817 | [
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<p>I read the answer to <a href="http://physics.stackexchange.com/questions/1984/why-does-holding-something-up-cost-energy-while-no-work-is-being-done">Why does holding something up cost energy while no work is being done?</a></p>
<p>and wanting to know more, I asked my teacher about it without telling him what I read... | g17818 | [
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<p>Big bang theory states that the universe began from a single point (which we may consider as a central frame of reference for the objects in the Universe). In 1929, Edwin Hubble confirmed that the Universe is expanding (consider that with respect to that reference point).</p>
<p>Does that imply that we cannot have ... | g17819 | [
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<p>I suspect that the $N$ factorial in the partition function for N indistinguishable particles
$$ Z = \frac{ Z_0^N } {N!} $$
is an approximation. Please someone correct me if I am wrong and why or why not. Thanks.</p>
<hr>
<p><strong>A simple case</strong>: </p>
<p>each particle has two states with energy $0$ and ... | g17820 | [
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<p>Well-known physics establishes that, compared to some reference frame (I'll denote as "stationary" here), one can do several things to start at rest, end at rest, and experience <em>less</em> time than objects in the stationary reference frame do, although one can not experience <em>more</em> time given the start an... | g17821 | [
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<p><img src="http://i.stack.imgur.com/cgdLI.png" alt="enter image description here"></p>
<p>$\Delta V_{ABCDA} = - \int_A^A \vec{E} \dot{}d\vec{l}$</p>
<blockquote>
<p>The requirement that the round-trip potential difference be zero means that $E_1$ and $E_2$ have to be equal. Therefore the electric field
must... | g17822 | [
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<p>As only several thousands of particles are holding in the ion trap, how can we understand the temperature? </p> | g17823 | [
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<p>I have tried to search through the forums and the Internet, however I haven't been able to find a source I was able to understand fully. </p>
<p>I have a distance $r$, with an uncertainty of $\mathrm{±\ 0.003\ m}$, however in order to linearise my graph, I need to divide $1$ with $r$ squared ($1/r^2$), what would t... | g17824 | [
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<p>Why is it that the maximum sound coming from a Rijke tube happens only when heated wire gauze is placed at 1/4th the length of the tube from the bottom. According to Rayleigh:</p>
<blockquote>
<p>If heat be periodically communicated to, and abstracted from, a mass of air vibrating in a
cylinder bounded by a pi... | g17825 | [
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0... |
<p>Why is the <a href="http://en.wikipedia.org/wiki/Compton_wavelength" rel="nofollow">Compton wavelength</a> $\lambda_c=\frac{\hbar}{mc}$ used as a <em>sensible measure</em> for the range of an interaction, where m is the mass of the corresponding mediator? </p> | g17826 | [
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<p>In the Feynman Lectures Vol. 1, it says that the Synchrotron at the California Institute of Technology is capable of producing electromagnetic Radiations with a frequency of $10^{24}$ cycles per second. Since I'm not familiar with <em>cycles</em>, I'd like to know where this lies in the UV Spectrum. </p> | g17827 | [
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<p>What is the <a href="http://physics.stackexchange.com/questions/29310/what-is-code-in-toric-code">code</a> distance in quantum information theory?
Code distance seems to be a very important concept in fault tolerant
quantum computation and topological quantum computation.</p> | g17828 | [
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<p>In experiment, cold skillet with droplets of water was filled with layer of oil and heated. The droplets started exploding. Why water can not leave skillet less violently, like steady chain of steam bubbles ?</p> | g17829 | [
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<p>IN wald's GR book in chapter 3 This is stated behind the definition of affine connection :</p>
<p>First He showed that if we have two derivative operator $\nabla_a , \tilde\nabla_a$ (both of which consistent with the definition of derivative operator) then at point $p\in M$, for any dual vector field $\omega_b$</p>... | g17830 | [
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<p>It seems that if the coherence length of a laser is big enough, it is possible to observe a (moving) interference picture by combining them. Is it true? How fast should photo-detectors be for observing of the interference of beams from two of the "best available" lasers? What is the coherence length of the best-avai... | g17831 | [
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<p>As I understand, Dirac equation was first interpreted as a wave equation following the ideas of non relativistic quantum mechanics, but this lead to different problems.</p>
<p>The equation was then reinterpreted as a field equation and it is now a crucial part of quantum field theory.</p>
<p>My question is: could ... | g17832 | [
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... |
<p>Wikipedia says that the 'macroscopic' definition of <a href="http://en.wikipedia.org/wiki/Entropy" rel="nofollow">entropy</a> is:</p>
<p>$$ \Delta S = \displaystyle \int \dfrac{dQ_{\rm rev}}{T}$$</p>
<p>Where $T$ is the uniform absolute temperature of a closed system and $dQ_{\rm rev}$ is an incremental reversible... | g17833 | [
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<p>Consider the p-V diagrams of an ideal and real stirling cycle, as <a href="http://poisson.me.dal.ca/~dp_08_04/Theory.html" rel="nofollow">found here</a>
The article suggests that dead volumes reduce the efficiency of a stirling engine. On the other hand, a simple thought experiment that comparas an ideal stilring en... | g17834 | [
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0.04382224753499031... |
<p>Many papers use <a href="http://en.wikipedia.org/wiki/Wyckoff_positions" rel="nofollow">Wyckoff positions</a> and Space Groups to report atom coordinates, making use of the structure's symmetries to save space in the notation (e.g. diamond = Fd-3m, only). </p>
<ol>
<li><p>How can I reconstruct the whole lattices gi... | g17835 | [
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-0.... |
<p>Under some atmospheric stability condition, over flat terrain, it has been observed for a while that the ratio between wind speed at height $h_1$ above the earth and the wind speed at height $h_0$ is $\log\frac{h_1}{h^*}/\log\frac{h_0}{h^*}$ where $h^*$ is related to the terrain (called roughness length). (see for e... | g17836 | [
0.06297098845243454,
0.008087890222668648,
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0.020445844158530235,
0.0032181469723582268,
0.05... |
<p>Consider a propeller plane with only one propeller in the front. If the propeller rotates, I would expect by conservation of angular momentum, that the body of the plane would spin in the opposite direction of the propeller but with much lower angular velocity because of the larger moment of inertia. However this do... | g17837 | [
-0.006648183800280094,
0.017351126298308372,
-0.009846975095570087,
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-0.04813024401664734,
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0.... |
<p>I am confused with the meaning of sink. What part of vehicle engine acts as reservoir and what does as sink? </p> | g17838 | [
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0.03677547350525856,
-0.0016405470669269562,
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-0.027186155319213867,
-0.016924496740102768,
0.028529493138194084,
0.06432276219129562,
... |
<p>I can not understand classical electrodynamics so well, maybe there is some book, video, lecture note can help me.</p> | g98 | [
-0.004372801631689072,
0.042332377284765244,
-0.008973981253802776,
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-0.035215772688388824,
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0.0207685399800539,
-0.017213016748428345,
0.0318... |
<p>A Wikipedia <a href="http://en.wikipedia.org/wiki/Power_engineering#Basics_of_electric_power" rel="nofollow">article</a> on Power engineering reads,</p>
<blockquote>
<p>Most refrigerators, air conditioners, pumps and industrial machinery use <strong>AC</strong> power whereas most computers and digital equipment u... | g17839 | [
0.021841127425432205,
0.02925407700240612,
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0.02801058627665043,
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-0.007114904932677746,
-0.019253097474575043,
0.0035747287329286337,
0.026533575728535652,
... |
<p>Why our universe is supposed to expand faster than light beyond the Hubble limit while a bubble nucleation of true vacuum is supposed tho expand asymptotically to the speed of light ?</p> | g17840 | [
0.037961628288030624,
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-0.06754354387521744,
0.06312184780836105,
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0.029187992215156555,
0.06... |
<p>Apparently all objects have wavelike properties, so, if we kick a football (soccer ball, if you must) through a pair of posts, does the ball in any sense diffract?</p>
<p>If this is ridiculous then let me know and I will delete the question.</p> | g17841 | [
0.0007352775428444147,
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0.01756032183766365,
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-0.0... |
<p>I know how and why we use this form of stationary Schrödinger equation for finding $\psi$ outside the finite square potential well:</p>
<p>$$\frac{d^2 \psi}{dx^2}=\kappa^2 \psi$$</p>
<p>I Also know that the general solution to this equation is:</p>
<p>$$\psi = Ae^{\kappa\, x} + Be^{-\kappa\, x}.$$</p>
<p>But why... | g17842 | [
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-0.020124902948737144,
0.03675925359129906,
0.009322930127382278,
-0.012902595102787018,
... |
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