question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
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<p>I am struggling with the following affirmation found in Ryder's QFT book, <a href="http://books.google.com.br/books?id=nnuW_kVJ500C&pg=PA177&lpg=PA177&dq=%22a%20small%20negative%20imaginary%20part%20to%20the%20Hamiltonian%22&source=bl&ots=vpxodARK1V&sig=gFZ9WUfgKBMAPy4olDusYEyRdoU&hl=en&a... | g9822 | [
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<p>Strings always have a dilaton in their spectrum. Its a scalar field (so presumably no spin), and so far a hypothetical particle. What is its physical significance?</p> | g9823 | [
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<p>Einstein postulated that gravity bends the geometry of space-time then what does magnetism do in to the geometry of space-time, or is there even a correlation between space-time geometry and magnetism?</p> | g9824 | [
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<p>How is theoretical computer science getting united with physics? Phenomena like Quantum Computing uses Quantum Mechanics to be able to compute things, how are computers helping not just to model our equations but actually predict new equations, helping us to see the computational aspect of nature and how various thi... | g9825 | [
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<p>I'm watching an episode of Mythbusters where they show aircraft saving 3-5% fuel when flying in a tight V formation. Interestingly, this also applies for the lead airplane. </p>
<p>How is that possible for the lead plane, too? Does the same apply for cars as well, or is it a flying phenomenon?</p> | g9826 | [
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<p>Can the findings of the Physics Nobel Laureates of 2011, namely the overpowering existence of dark energy (vacuum energy) have any implications in the quest the combine Quantum Mechanics and General Relativity? Maybe toward a theory of Quantum Gravitation?</p> | g9827 | [
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<p>Suppose a device or object were traveling at or near the speed of light, and fission or fusion occurred while in this state of motion, creating an enormous blast, what would occur? Would this cause an acceleration of the objects or particles immediately in front of this blast? Or would some other event occur that I ... | g9828 | [
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<p>Looking at <a href="http://www.tcm.phy.cam.ac.uk/~bds10/phase/scaling.pdf" rel="nofollow">this paper on page 1</a> how is the first limit obtained? That is, if I have some homogeneous function $g_f(h/t^{\Delta})$, how does setting the gap exponent $\Delta$ to $3/2$ ensure that $$\lim_{x \to 0} g_f(x) = -1/u?$$</p> | g9829 | [
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<p>The potential for the Higgs field is standard a quartic one (Mexican hat). Is this done for simplicity or are there fundamental reasons for this choice? I can imagine further contributions to this potential without altering the essentials. But this may lead to differences in the derived particle masses.</p> | g9830 | [
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<p>About one year ago I attended a pretty interesting seminar of <a href="http://www.ge.infn.it/~zanghi/" rel="nofollow">Nino Zanghì</a> on the actual state of <a href="http://en.wikipedia.org/wiki/Bohmian_quantum_mechanics" rel="nofollow">Bohmian mechanics</a>.</p>
<p>Now, during my undergraduate studies, I didn't ha... | g9831 | [
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<p>If I was to pass a metal object through a magnetic field would there be any friction?</p> | g9832 | [
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<p>I just learned some introductory quantum meachnics, but not statistical mechanics, so I am curious how partition functions would be used in the following case:</p>
<p>Suppose there are three particles in x-axis. These particles all have spin 1/2. Neighboring two particles interact with interaction energy of U. (par... | g9833 | [
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<p>I'm just a student of grade 11 but, I was interested in knowing about Physics much deeper. In order to start my interest in Physics, I watched this video of Quantum Physics NOVA : <a href="http://www.youtube.com/watch?v=QVPIGtGcYE0" rel="nofollow">Quantum Physics(NOVA)</a></p>
<p>I have some questions in mind : </p... | g9834 | [
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<p>Einstein said that gravity can be looked at as curvature in space- time and not as a force that is acting between bodies. (Actually what Einstein said was that gravity was curvature in space-time and not a force, but the question what gravity really is, is a philosophic question, not a physical one)</p> | g9835 | [
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<p>I want to model liquid lead swirling in a sphere. This is connected to General Fusion’s fusion machine. <a href="http://www.ted.com/talks/michel_laberge_how_synchronized_hammer_strikes_could_generate_nuclear_fusion" rel="nofollow">A 55 million dollar, Jeff Bezos funded, 60 person company trying to change the world... | g9836 | [
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<p><em>Why there is no stable nuclei with
$$A=5$$
in nuclide the chart and so in nature like we know it?</em></p> | g9837 | [
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<p>I recently watched the documentary miniseries "How the Universe Works" and few things can't stop bothering me. I am not an astronomer nor a physicist so those may be dummy questions.
what I get know from the movie is cluster's stars are not orbiting but they are bond by the gravity so:</p>
<ul>
<li>Does the stars i... | g9838 | [
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<p>If a container filled with pure oxygen and fitted with leak-proof valves were to be dumped into the exosphere at night, would the contained oxygen condense?</p> | g9839 | [
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<p>Thermal conductivity are often used for surfaces between the computer chip and the heat sink to increase heat transfer and they want high thermal conductivity to decrease the thermal resistance. By $$\Delta T=RQ$$ and $Q$ is constant by the chip. When we decrease R, and keep Q constant from the chip, we decrease $\D... | g9840 | [
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<p>The <a href="http://ncatlab.org/nlab/show/G2-MSSM" rel="nofollow">G2-MSSM</a> is supposed to be the low-energy theory of a hypothetical class of M-theory compactifications studied by some phenomenologists. It is just the <a href="http://en.wikipedia.org/wiki/Minimal_Supersymmetric_Standard_Model" rel="nofollow">MSSM... | g9841 | [
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<p>While the moon is certainly not a good reflector of solar radiation, surely the radiation it reflects back heats the Earth (even if it is a terribly small amount).</p>
<p>How would one go about calculating (or estimating) this heating contribution on a night with a Full Moon?</p> | g9842 | [
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<p>I'm trying to explain the behaviour of a geostationary satellite using different frames of reference.</p>
<ol>
<li><p><strong>Inertial frame:</strong> The satellite has a circular motion with angular velocity $\omega$. The centripetal force $F$ required for this motion is created by the gravitational pull of Earth.... | g9843 | [
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<p>In Randall Munroe's <em>What If?</em> He is calculating the <a href="http://what-if.xkcd.com/73/">Lethal Neutrinos</a> dose.</p>
<blockquote>
<p>If you observed a supernova from 1 AU away—and you somehow avoided being being incinerated, vaporized, and converted to some type of exotic plasma—even the flood of gho... | g9844 | [
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<p>Imagine two locations with different amounts of gravity. I carry up a weight in low gravity, move it on this height over to the other place, and let it fall down there with higher gravity.</p>
<p><img src="http://i.stack.imgur.com/pWNNf.png" alt="experiment setup"></p>
<p>Wouldn't falling down release more energy ... | g9845 | [
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<p>From my point of view, high gas pressure input creates air rotation inside the tube. Due to the rotation, the kinetic energy in the air change to internal energy. The internal energy release as heat energy. The heat energy goes out and the cold air stay. The cold air flows back to the other end to create the cold ai... | g316 | [
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<p>Explain the Physical implications behind the exchange antisymmetry condition of fermions. This condition forms the basis of the pauli principle but I can't find/understand what happens physically that requires then the presence of a minus sign upon particle interchange.</p> | g9846 | [
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<blockquote>
<p>Material scientists have discovered a new fluid property called "radost" that is carried along with a fluid as it moves from one place to the next (just like a fluid's mass or momentum). Let $r(x,y,z,t)$ be the amount of radost/unit mass in a fluid. Let $\rho(x,y,z,t)$ be the mass density of the fluid... | g9847 | [
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<p>Are there any ideas of explaining the time dilatation as limits in "computing power"? What I mean is basically that the greater is a concentrated mass, the harder is to "compute" what happens in such system, because more data needs processing (because e.g. more near positioned mass –> more interactions). The same is... | g9848 | [
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<p>A unitary matrix U is a matrix such that the conjugate transpose of U, when multiplied on the right with U, yields identity. My question is, is it possible to obtain the transpose of any density matrix using some unitary operation? (I read somewhere that the transpose operation is an 'anti-unitary' operation, but I ... | g9849 | [
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<p>I am a bit confused by the description of Halbach arrays. It is said that the line of magnets aligned in certain way results in cancellation of magnetic field on one side of the array, and amplification on the other side.
And there is a schematic distribution of magnetic flux - <img src="http://i.stack.imgur.com/Gq... | g9850 | [
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<p><a href="https://www.google.com/search?hl=en&gl=us&tbm=nws&q=tornado%20thiel">Peter Thiel just paid $300,000</a> to Canadian inventor <a href="http://vortexengine.ca/index.shtml">Louis Michaud</a> who is working to construct useful "man-made tornadoes" or "atmospheric <a href="http://en.wikipedia.org/wik... | g9851 | [
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<p>I am interested in the linear absorption of 762nm light near a transition of molecular oxygen. I need to find some experimental numbers that will tell us how far the 762nm light will propagate before getting absorbed. Specifically, I want to know the e-folding length, $\gamma^{-1}$ (the length over which the intensi... | g9852 | [
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0.01916438527405262,
0.0015361768892034888,
0.02028534561395645,
0.01850871741771698,
-0.0... |
<p>In <a href="http://en.wikipedia.org/wiki/Mathematical_formulation_of_quantum_mechanics" rel="nofollow">Quantum Mechanics</a>, why is it that a self-adjoint operator is linked to an observable? What makes it measureable? And why isn't a non-Hermitian operator linked to an observable?</p>
<p>Also, what type of observ... | g9853 | [
0.0034232495818287134,
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... |
<p>Are neutrinos affected by gravity?</p>
<p>If not, could that be a plausible reason for a neutrino taking a shorter path than light, since light is affected by gravity?</p> | g925 | [
0.01782229356467724,
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<p><strong>I would like to know if any epistemologist or science popularizer has ever think about a better/simpler name for <em>exotic</em> or <em>non-baryonic cold dark matter</em> like <em>black matter</em>.</strong></p>
<p>That would be interesting in my opinion to stress: </p>
<ul>
<li>the change of paradigm that... | g9854 | [
0.02423533983528614,
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<p>I know that static friction isn't the cause of deceleration of a rolling body. But if static friction is the only force in the horizontal direction, then shouldn't there be some acceleration produced in this direction? The body should decelerate or accelerate. So how come in this case, a force does not produce accel... | g9855 | [
0.08646228909492493,
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0.03584635257720947,
0.005777784... |
<p>Imagine a ladder leaning against a wall. All surfaces are smooth. Hence the ladder will slip and fall. While falling it rotates because there are external torques acting on it. My question is about which axis does the ladder rotate?</p> | g9856 | [
0.053213827311992645,
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<p>We are mostly all familiar with a microscope, and know that it helps to see MICRO components, like stuff that is photolithographically etched on silicon semiconductor die.</p>
<p>(The latter can also be nano, but let's bide that.)</p>
<p>Anyways, we rarely hear of <a href="http://www.google.com/#q=nanoscope" rel="... | g9857 | [
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<p>A common analogy for gravity is the ball-on-a-rubber-sheet model. In this model, mass distorts spacetime and creates a 'valley' into which other mass can fall. Is this same principal valid for magnetic fields as well (proton-electron)? If so, then how is the repulsion effect modelled?</p>
<p>I ask because the under... | g9858 | [
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0.04508357495069504,
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<p>A spin is created in a superposition of up and down states. A magnet is moved very slowly, towards the spin. What is the work done by the magnet. It may be helpful to imagine that the magnet is connected to a spring that expands or contracts depending on work done by the magnet. </p> | g9859 | [
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<p>Suppose I have something like $ f = g_{\mu \nu} x^{\mu} x^{\nu} $, where the Einstein summation convention is implied. Now suppose I want to to take the derivative $ \partial_{\mu}f = \frac{\partial f}{\partial x^{\mu}} $. How would I go about doing this? I figure it's not just going to be $ \partial_{\mu} f = g_... | g9860 | [
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<p>Is the following assertion sufficiently unique to merit a paper? <em>Every absolute conservation law implies a corresponding form of entanglement</em>, not just spin (angular momentum). Linear momentum conservation would for example entangle originating equipment with wave packets and help determine packet dispersio... | g9861 | [
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<p>Let's say I have two <a href="http://en.wikipedia.org/wiki/Probability_amplitude" rel="nofollow">probability amplitude</a> functions given by $\psi_1$ and $\psi_2$. That is, $\psi_i:\Sigma\rightarrow\mathbb{C}$ for some domain $\Sigma$ with $\int_\Sigma|\psi_i|^2=1$ for $i\in\{1,2\}$. Is there a canonical distance... | g9862 | [
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<p>It is well-known that quantum mechanics does not admit a noncontextual ontological model, and there are countless different proofs of it. I'm interested in the simplest proofs that can be cast as an inequality, and bonus points if there's a proof that a simpler one can't be found.</p>
<p>The definition of contextua... | g9863 | [
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<p>What is the most essential reason that actually leads to the quantization. I am reading the book on quantum mechanics by Griffiths. The quanta in the infinite potential well for e.g. arise due to the boundary conditions, and the quanta in harmonic oscillator arise due to the commutation relations of the ladder opera... | g9864 | [
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<p>Is the Higgs mechanism a fundamental interaction of the same standing as the strong, weak and electromagnetic interactions? If not, is it mediated by the weak interaction? It seems that all the massive particles participate in the weak interaction, and the massless ones do not, but this might just be a coincidence.<... | g9865 | [
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<p>Standard Model is advanced (lorentz invariant) version of Quantum physics. It tried to include everything which came in the way while understanding quantum world. It even didn't bother to include even Higgs Boson which was hypothetical at that time. Did they never find gravitation in the way of other quantum in... | g9866 | [
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<p>According to the knowledge I have, there are routers, switches etc. Therefore, packets would have to be "measured" before continuing on. (If not, how will anyone know the damn IP address?)</p>
<p>But this effectively ends any advantage of quantum channel..</p>
<p>So how is quantum network working theoretically?</p... | g9867 | [
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<p>Rockets separate from the launch pad and supporting structures very early in flight. It seems like they should tip over once that happens. </p>
<p>Why don't they tip over? Is it due to a well designed center of gravity or do they somehow achieve aerodynamic stabilization?</p> | g9868 | [
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<p>I'm preparing for entry into a Physics degree course, and was planning on a double major in Physics (with a specialization in Quantum Information later) but am now considering a minor in Astrophysics/Astronomy. How useful would Astrophysics be? I have an interest in that area also.</p> | g9869 | [
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<p>For a pure state $\rho_{AB}$, the entropy of entanglement of subsystem $A$ is</p>
<p>\begin{equation}
S( \rho_A) = -tr (\rho_A \log \rho_A)
\end{equation}</p>
<p>where $\rho_A$ is the reduced density matrix of A. </p>
<p>For a single site of a spin chain, $\rho_A$ can be written in terms of single site correlatio... | g9870 | [
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<p>The imprint of gravitational waves created shortly after the big bang may offer direct evidence for inflation theory, according to a discovery by the BICEP2 experiment at the South Pole and released today. What this means for those alternatives theories to inflation such as string gas cosmology and the ekpyrotic uni... | g9871 | [
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<p>Honestly though, is the Earth considered air-tight in the sense that its gases don't escape? </p>
<p>I'm sure every physicist who reads this is going to tear their hairs out, but the extent of my knowledge in this area is that you need to travel a certain speed to break Earth's gravitational pull and that has me wo... | g9872 | [
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<p>The recent results of the BICEP 2 experiment published on March 17th 2014, has generated a lot of media attention, with the general consensus being that "this is a major discovery" perhaps leading to a Nobel Prize for some. </p>
<p>But for those that are still skeptical, what are the competitors to this experiment,... | g9873 | [
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<p>I have seen people counter the problem of big box and small weighing machine by stepping on the machine while carrying the box in arms and subtract the body weight. Do you think it'll give accurate result (not counting negligible difference of course)? </p>
<p>It seems like a DUH kind of question, but I wanted to a... | g9874 | [
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<p>I have 2 rigid-bodies (b1,b2) if i linked one to the other (as if they are conjoined together) , how to represent b1 effect on b2 and b2 effect on b1</p>
<p><img src="http://i.stack.imgur.com/E0XOV.png" alt="enter image description here"></p>
<p>Is there any LAW that affect the position/orientation of the other bo... | g9875 | [
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<p>Yes, you all talk about neutrinos and spins, but I came out with this basic s**t :D</p>
<p>All of us learnt the basic equations of collisions, elastic (everything bounces and energy remains the same), or non-elastic (the classic example where objects remain stick together). What if objects don't remain together and... | g9876 | [
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<p>If a body with mass $m$ begins at position $x_0$ with velocity $v_0$ and experiences a force that varies as a function of time $f(t)$ (and we ignore gravity, friction, and everything else that might complicate matters), then we can compute the position and velocity of the body at any time:</p>
<p>$$v(t) ~= ~\int\li... | g9877 | [
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<p>Suppose we have an asymptotically flat, globally hyperbolic spacetime $M$ endowed with two one-parameter isometry groups $\sigma_t$ and $\chi_{\phi}$ which commute (i.e. $\sigma_t \circ \chi_{\phi}= \chi_{\phi} \circ \sigma_t.$)</p>
<p>Assume moreover that the orbits of $\sigma_t$ are timelike curves generated by t... | g9878 | [
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<p>If We put a small floating object (penoplast granule) on a surface of water it performs spiral like movements and eventually sticks to a side of a vial. </p>
<p>What physical forces are involved? I'm particularly interested what causes spiral like movements. Would be grateful if you can suggest also some literature... | g9879 | [
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<p>To find the Higgs boson, we had to build the biggest machine mankind has ever built: the LHC with a collision energy of up to 14 TeV. Inside the sun there is a huge pressure and temperature, but is the energy density high enough for Higgs bosons to be created?</p> | g9880 | [
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<p>Why is the Boltzmann distribution used over the Maxwell distribution in many cases such as the derivation of Plancks law of thermal radiation, derivation of Einstein A and B coefficients, Langevin theory of paramagnetism etc.?</p> | g9881 | [
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<p>The circuit breaker at the electrical mains trips at home when there is a thunderstorm outside.
Why does this occur?</p> | g9882 | [
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<p>I know it's not economically feasible, but is there a simple equation telling you the ellipse earth would follow if you theoretically launch all of the landfills, i.e. garbage, beyond our orbit, thus decreasing mass by X.</p> | g9883 | [
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0.006927309092134237,
0.11989112943410873,
0.... |
<p>Fairly straightforward question. If not, why not?</p>
<p>I suspect that if they do, it is not perceived due to the regions of highest dispersion being in one's region of lowest visual acuity.</p> | g9884 | [
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<p>Let the amount of energy in one pulse of (laser) light be $E$, and the wavelength be $\lambda$.</p>
<p>This pulse goes straight to the mirror, and it is reflected by the mirror.</p>
<p>Let the reflectivity of this mirror be $r_{\lambda}$.</p>
<p><img src="http://i.stack.imgur.com/APbUi.jpg" alt="enter image descr... | g9885 | [
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<p>I'm looking at two papers in particular: <a href="http://www.wiley-vch.de/vch/journals/2231/pss40/167_177.pdf" rel="nofollow">A. L. Efros and B. I. Shklovskii, Critical Behaviour of Conductivity and Dielectric Constant near the Metal-Non-Metal Transition Threshold, Phys. Status Solidi B 76, 475 (1976)</a> and <a hre... | g9886 | [
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<p>It seems to me that special relativity has a weird definition of the causality relation. In that theory, the only thing that matters is the space-time distance between events. But I don't think this is the case. It seems to me that if I am pressing a few keys on my keyboard and then causing this question to appear o... | g9887 | [
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<p>I've recently been looking into performance figures for various auto mobiles, and I see the terms <a href="http://en.wikipedia.org/wiki/Horsepower#Brake_horsepower" rel="nofollow">BHP</a> and <a href="http://en.wikipedia.org/wiki/Torque" rel="nofollow">Torque</a> used quite often, but I can't say I really understand... | g9888 | [
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<p>How do scientists place satellites into orbit? How do they calculate the gravity acting on the spacecraft in order to generate exact opposite force by means of Kinetic energy to keep the satellite stable?</p> | g9889 | [
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<p>I would like to know how to calculate the temperature change of a moving object. For example if I throw a ball that is warmer than the surrounding air, how much would it lose form it's temperature in every second? I searched for two days now, but I have only partial solutions :(. I would need a formula that takes in... | g9890 | [
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<p>Lets say we take the standard configuration when $x'y'$ is moving away from system $xy$ (image 1). By knowing that the phase is constant in all frames $\phi=\phi'$ we can derive the Lorenz transformations for a standard configuration.</p>
<p><img src="http://shrani.si/f/18/R5/2pJr7UXu/1.png" alt="image 1"></p>
<p>... | g9891 | [
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... |
<p>Sometimes I see comments about <a href="http://arxiv.org/abs/1209.5056" rel="nofollow">the big desert hypothesis</a> that I don't understand. For instance <a href="http://www.math.columbia.edu/~woit/wordpress/?p=5569" rel="nofollow">in a famous blog</a> :</p>
<blockquote>
<p><em>...This is based on a renormalizat... | g9892 | [
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<p>I wonder how to properly write the motion equations for the inverted pendulum on a cart in case of overdamped dynamics. Imagine the system <a href="http://en.wikipedia.org/wiki/Inverted_pendulum#Inverted_pendulum_on_a_cart" rel="nofollow">illustrated in Wikipedia</a> placed in a liquid with high viscosity $\beta$. I... | g9893 | [
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<p>How will a light source with a specific $\lambda$ positioned right at the nth order maximum pointing towards a diffraction grating be affected? Will it come out "directed"?<img src="http://i.stack.imgur.com/hhWJn.png" alt="enter image description here"></p> | g9894 | [
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<p>Is the double slit experiment an example of entanglement when it seems as if the photon is going through both slits? Or put another way, is it at this stage when we attempt measurement we see a photon on one side affect the photon on the other side? Do entangled particles have to be made first to show entanglement o... | g9895 | [
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<p>What form does the discharge stream of a propeller take in a Herschel-Bulkley fluid, chracterised by having a certain yield stress, shear between layers only occurs beyond that stress.</p>
<p>This situation is known from biogas-plants, where the slurry is often mixed by propellers - Almost always in cylindrical tan... | g9896 | [
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<p>I am reading Leslie Ballentine's Quantum Mechanics, section 7.2, which is all about the explicit form of the Angular Momentum operators.</p>
<p>I understand how he gets the form for the single component state function, equation (7.18) which has the form $$\mathbf{R} \Psi(\mathbf{x}) = \Psi(R^{-1}(\mathbf{x})) $$ wh... | g9897 | [
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<p>I have heard of the invariant quantity $\Delta s$ in relativity for which I have stumbled upon an equation $\Delta s^2 = \Delta x^2 - c \Delta t^2$. This reminds me of hyperbola, which has general equation like this one: </p>
<p>$$\frac{x^2}{a^2}-\frac{y^2}{b^2} = 1$$</p>
<p>But i already know that in relativity t... | g9898 | [
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<p>Fundamental notions of QM have to do with observation, a major example being The Uncertainty Principle. </p>
<ol>
<li><p>What is the technical definition of an observation/<a href="http://en.wikipedia.org/wiki/Measurement_in_quantum_mechanics">measurement</a>? </p></li>
<li><p>If I look at a QM system, it will coll... | g805 | [
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<p>This question is directed mostly at people giving lectures on black holes, but input by other physicists or students is very much appreciated.</p>
<p><b>Do you know a good (home)-experiment with a black hole analog (such as water in a bathtub) that allows to discuss most of the pertinent concepts and features of a ... | g448 | [
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<p>Back in the day I learned that a few special thermodynamical processes have special names. </p>
<p>For example, if one keeps $P$ constant, the process is called isobaric, if one keeps $T, V$ or $S$ constant, one gets, correspondingly, isothermic, isochoric or isentropic processes. Similarly, if one keeps $\dfrac{\m... | g9899 | [
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<p>I am pretty sure, that during last 60 years of well-funded research a lot of ideas on nuclear fusion were already tried and ruled out. </p>
<p>Is there some summary describing all of them and why they didn't work? (I am looking something going way beyond just Tokamak / Stellarator / Laser ICF / Z-Pinch).</p> | g9900 | [
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<p>I wrote a first program that simulates a solar system. I was able to calculate the locations for every planet on its elliptical route for any given time.<br>
In a second program i managed to simulate newtonian gravitational behavior (n-body problem, time-step approach). </p>
<p>But i'm wondering how it is possible... | g9901 | [
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<p>If gravity is this "unexplainable force" that pulls everything to the center of a planet or stellar remnant you stand upon, why doesn't gravity pull itself?</p>
<p>If gravity effects anything with energy, why doesn't gravity effect itself?</p>
<p>Gravity is energy, right?</p> | g9902 | [
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<p>In quantum theory we have some principles that guides us, e.g. Pauli's principle. What I am after in this question is a list of fundamental results, be it equation or identities that must hold in a respectable QFT. I am thinking for instance of the Wards identities or Adler-Bell-Jackiw anomaly and similar things. </... | g9903 | [
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<p>I read this book here: <a href="http://tiny.cc/Gravity-Atom-Myth" rel="nofollow">http://tiny.cc/Gravity-Atom-Myth</a></p>
<p>It claims that while gravity does affect individual atoms, it's not quantified like molecular mass due to lack of binding proteins which render air-oxygen trajectories improbable.</p> | g9904 | [
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<p>My atomic physics lab is in a building that experiences huge swings in humidity levels during the year due to the <a href="http://en.wikipedia.org/wiki/North_American_Monsoon">monsoon season</a></p>
<p>Our building provides temperature, but not humidity control. Using just the building temperature control results ... | g9905 | [
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<p>I'm trying to solve a system of springs and masses that is confusing me.
First, the balls are all lined up linearly. Secondly, the ball in the middle has a smaller mass $m$ while the first and last balls have a larger mass of $M$.
The larger balls are each connected to the middle ball with a spring with a spring co... | g9906 | [
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<p>If I poured water into my tea, would I see more or less of the bottom of the tea-cup?</p>
<p>Intuitively, there would be as many particles blocking as many photons, and so I'd see the bottom just as clearly as before.</p> | g9907 | [
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<p>After playing a game called "Kerbal Space Program" I got interested in orbital mechanics and started messing with <a href="https://www.dropbox.com/s/ha8dlboo6pjgc7s/KSPequations.pdf">simplified calculations</a> to determine $\Delta v$ requirements. In which I compared two trajectories to get into orbit/land from orb... | g9908 | [
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<p>I have some questions about this exercise:</p>
<blockquote>
<p><em>In an horizontal plane, a $OA$ bar with mass $m$ and length $a$ moves, with another bar $AB$ (same mass, double length) attached in the point A.
In the point B, there is a force $F=K\frac {K} {r^2} \frac {B-O} {r}$
Find the equations of motio... | g9909 | [
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... |
<p>In this question-</p>
<blockquote>
<p><em>A motorboat is racing towards north at 25km/h and the water current in that region is 10km/hr in the direction of 60 degree east of south. Find the resultant velocity of the boat.</em></p>
</blockquote>
<p>The first part is quite easy and we get 21.8 approx as the magnit... | g9910 | [
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<p>This is a question for anyone who is familiar with Di Francesco's book on Conformal Field theory. In particular, on P.108 when he is deriving the general form of the 2-point Schwinger function in two dimensions. He writes that the most general form of the tensor is $$S_{\mu \nu \rho \sigma} = (x^2)^{-4} \left\{ A_1 ... | g9911 | [
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0.0... |
<p>I read a book on pop sci book on quantum mechanics and the author said that electrons do not fall into the nucleus due to quantum mechanics- which principles suggest this (I think it was Heisenberg's Uncertainty and Pauli's Exclusion Principle) and why?</p>
<p>Also, I've heard that if Bohr's planetary model were co... | g9912 | [
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0.00... |
<p>In comments to <a href="http://physics.stackexchange.com/q/135212/5739">a Phys.SE question</a>, it has been written: </p>
<blockquote>
<p><em>'Tunneling' is perfectly real, even in classical physics. [...] For sufficiently large temperatures this can put the system above a hump in its potential energy.</em></p>
<... | g9913 | [
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<p>I am an newbie general relativistic learner and I learnt that gravity is bending of space-time and since objects move in straight-lines but since its curved they follow curved movement through space thus creating the effect we know as gravity.</p>
<p>That said, what if an object has velocity of 0 and since its not ... | g9914 | [
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0.06480687856674194,
0.0... |
<p>I am doing some self-study on photonics and have encountered the following question:</p>
<blockquote>
<p><em>We know that amorphous electronic crystals such as <a href="http://en.wikipedia.org/wiki/Amorphous_silicon" rel="nofollow">amorphous silicon</a> have a bandgap. Can amorphous photonic crystals also have a ... | g9915 | [
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<p>In an experiment we placed a long dielectric cylindrical shell (cylindrical tube)(with inner and outer radii r1 and r2, respectively) in a homogenous field such that its axis was orthogonal to the field. The medium elsewhere has a dielectric constant of unity. </p>
<p>How can I calculate the potentials and fields e... | g9916 | [
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<p>I'm working to solve the steady-state short circuit current of a solar cells, using the coupled continuity equations with a drift-diffusion expression and Poisson's equation:</p>
<pre><code>D[n[x, t], t] - (1 / q) D[Jn[x, t], x] == G - R;
D[p[x, t], t] + (1 / q) D[Jp[x, t], x] == G - R;
Jn[x, t] == q \[Mu]n (n F +... | g9917 | [
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0.048367939889431,
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0.0... |
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