question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>Anyone care trying to explain how there is supposedly no center to the universe? Quantum Holography implies a center. Any flowery language of proto atoms or cosmic eggs does as well too. Even water droplet-like fission computer simulations of inflation can mathematically assign a center point. Plainly speaking, Q... | g16572 | [
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<p>Is there any foreseeable technology which would facilitate the direct observation of the cosmic neutrino background?</p>
<p>Would the ability to warp spacetime have any application here?</p> | g16573 | [
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<p>Often when I am learning physics I start to think about whether the laws I'm learning are mere definitions or experimentally determined, and usually the textbook does not make this clear. As Thomas Kuhn writes in <em>The Structure of Scientific Revolutions</em>,</p>
<blockquote>
<p>These generalizations look like... | g16574 | [
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<p>What I am really asking is are there other functions that, like $\sin()$ and $\cos()$ are <strong>bounded</strong> from above and below, and <strong>periodic</strong>?</p>
<p>If there are, why are they never used to describe oscillations in Physics?</p>
<p>EDIT:</p>
<p>Actually I have just thought of a <em>cycloi... | g16575 | [
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<p>The problems is as follows:</p>
<blockquote>
<p>A 2000kg Ford was travelling south when it collided with your 1000kg sports car
travelling west. The two badly-damaged cars became entangled in the collision and
leave a skid mark that is 20 meters long in a direction 14◦ to the west of the
original directio... | g16576 | [
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<p>I have seen everywhere that where on road, on railway track when there is a turn then one side of that road or railway track is below the surface or some what down then actual surface. </p>
<p>Any one tell me why this type of mechanism is used on turn ?</p> | g16577 | [
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<p>I think I'm missing something with torques. I seem to have gotten myself confused.</p>
<p>I have a box that's centered at ( 0 , 0 , 0 ) with length ( $x$ dimension ) = 1 , width ( $y$ dimension ) = 0.25, and height ( $z$ dimension ) = 0.5. The edges are parallel to the axes. The $x$ axis is left(-) and right(+), th... | g16578 | [
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<p><strong>Motivation.</strong></p>
<p>I was recently reviewing the section 3.10 in Sakurai's quantum mechanics in which he discusses tensor operators, and I was left desiring a more mathematically general/precise discussion. I then skimmed the Wikipedia page on tensor operators, and felt similarly dissatisfied. Her... | g16579 | [
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<p>I read an interesting article</p>
<p><a href="http://m.machinedesign.com/news/motor-sizing-made-easy" rel="nofollow">http://m.machinedesign.com/news/motor-sizing-made-easy</a></p>
<p>It is very interesting, but I can not follow the 2nd last paragraph. I don't understand why it is true.</p>
<p><em><strong>Gearboxe... | g16580 | [
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<p>I've been having a bit of trouble wrapping my mind around this. </p>
<p>If I were in a ship going 77% the speed of light (enough to experience reasonable time dilation) would I see earth going in fast forward? Would people on earth see my ship moving very slowly?</p>
<p>I have this question because I was reading P... | g16581 | [
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<p>From the cosmic microwave background, one can extract the scalar spectral index $n_s$. It is measured to be smaller than 1 by several standard deviations. <a href="https://en.wikipedia.org/wiki/Lambda-CDM_model" rel="nofollow">Wikipedia</a> says that it is a parameter of the Λ-CDM model. This is puzzling me. I thoug... | g16582 | [
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<p>In text "<a href="http://arxiv.org/abs/hep-th/0111246" rel="nofollow">Covariant theory of asymptotic symmetries, conservation laws and central charges</a>" is given an example of finding central charges and superpotential (among other things). </p>
<p>I am interested in $AdS_3$ case, since there is a lot of literat... | g16583 | [
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<p>I am much interested in physics. I have been caught up with one serious question related to speed of light. Hearing about Large Hadron Collider (LHC), it is said that protons in there are accelerated to almost the speed of light, i.e., $3\times10^8$ metre per second. One can be sure that the length in which the abov... | g16584 | [
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<p>Here is a strange test question I really don't get:</p>
<blockquote>
<p>A ball falls freely from a certain height, and due to air resistance it will reach a certain terminal velocity (assuming there is a normal gravitational acceleration going on all the time). Then it hits the ground, and bounces back without lo... | g16585 | [
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<p>On page 116 of <a href="http://rads.stackoverflow.com/amzn/click/0521880327" rel="nofollow">this</a> book it is said, that reparameterization invariance of the string action is analogous to the gauge invariance in electrodynamices.</p>
<p>Whereas Maxwell's equations are symmetric under a gauge transformation which ... | g16586 | [
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<p>I have a question regarding the four-potential and its gauge symmetry.</p>
<p>We have a gauge freedom:
$A_{\mu} \rightarrow A_{\mu} + \partial_{\mu}\chi$ <br/><br/>
Such a transformation does not alter the EM field.</p>
<p>Now my questions are:</p>
<p>How do I find the gauge invariant components of $A_{\mu}$? I ... | g16587 | [
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<p>Two twins are identical in every way, including their widget production.</p>
<p>One twin goes on a long space trip at near the speed of light to produce widgets during the trip.</p>
<p>When space-twin returns he has aged less than earth-twin. But, who produced more widgets?</p> | g16588 | [
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<p>Several bodies in the Solar System are possessed of a magnetosphere - Sol, Jupiter, Saturn, Earth to name a few. With these we have the proof of spacecraft/readings from Earth. For exoplanets being discovered lately magnetosphere is apparently reported to exist by virtue of a bow-shock observed from Earth/Earth Orbi... | g16589 | [
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<p>Having some free time, I've begun a mini-project attempting to understand how music works in more detail, which has so far only involved music theory and a bit of set theory. I'm now trying to get my head around the physics of sound waves, and in particular, I'm trying to understand how any sound can be analysed as ... | g16590 | [
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<p>If we take the analogy that in an empty space the space is just a flat sheet then if there is a single planet or a star then the flat sheet will curve below the planet leaving a curvature shaped like a hemisphere below the object, my question is, Does this curvature change as space expands?</p> | g56 | [
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<p>The conceptual model of multidimensional vibrating strings provides an incredibly rich and diverse "language" that almost certainly is encompassing all of known physics as a singular point somewhere within its almost unfathomably large parameter space; e.g. see <a href="http://physics.stackexchange.com/q/15/7670">Wh... | g16591 | [
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<p>I want to take liquid nitrogen in a pressurized container and spray it through a hose onto objects in a room. </p>
<p>The container has a pressure regulator so I can adjust pressure as desired. The requirement is that a particular temperature is reached on exit from the hose. </p>
<p>I understand that the final... | g16592 | [
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<p>If a giant stone sphere was sitting on the earths surface, would it experience a later force due to the earths rotation? For example my intuition tells me that if there was a sphere a mile high outside my window I would see it moving very slowly, rolling along the ground as the earth rotated in the opposite directio... | g16593 | [
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<p>I'm looking for contemporary reviews on neutron stars. Seems like this area is pretty active, so even reviews from five or ten years ago are somewhat lacking, though certainly not worthless. Does anyone have recommendations? Newer is better.</p>
<p>Books are okay too, but I'd prefer one of those 70-ish page reviews... | g16594 | [
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<p>If magnetic field is conservative, then why not the magnetic force?</p>
<p>My professor thinks it is non conservative but he couldn't explain to me why?</p> | g212 | [
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<p>EDIT: Thanks to the first answer, I may see that there is differences between a giant solenoid and a completely uniform magnetic field. Therefore it would be great if one can explain to me both the case.</p>
<p>Let's say there is an uniform magnetic field inside a very long and large solenoid. The magnetic field is... | g16595 | [
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<p>Two small wire loops, each with radius b, are placed a distance $d >> b$ apart. The loops are oriented as shown below; i.e., both loops lie in the x-y plane. Each loop carries the same current I. How would your answer change if the loops carried the same magnitude current, but were oppositely directed? <img ... | g16596 | [
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<p>Consider a flexible free conductor which is placed near a strong long bar magnet. How will the the conductor arrange itself if current is passed through it? I asked my professor: he gave me a hint that always a system has tendency to be in a state such that its potential energy is minimum. Why is this so?</p>
<p>PS... | g16597 | [
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<p>We all know the basic rules for <a href="http://en.wikipedia.org/wiki/Y-%CE%94_transform" rel="nofollow">conversion</a> of $"Delta"$ circuits to $"Star"$ circuits and vice versa. We also know that this is needed for simplification of circuits in complex cases. Can anyone please explain HOW the concept of such conver... | g16598 | [
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<p>I seem to have misunderstood something in velocity. There is a path from point A to point B, that gap between is 100 meters.
An object moves from point A to B with a velocity is 10 m/s.</p>
<p>$V=\frac{\Delta x}{\Delta t}$ </p>
<p>$ x = 100$ $meters$</p>
<p>$ t = 10$ $seconds$</p>
<p>Now, within that gap is <st... | g16599 | [
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<p>What is the symmetry factor for the following Feynman diagram if we assume that the external points are held fixed?<img src="http://i.stack.imgur.com/AyDGM.jpg" alt="enter image description here"></p>
<p>Please ignore the arrows in the diagram. I am referring to the second diagram on the third row of Figure 9.7, pa... | g16600 | [
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<p>For example let's have the hydrogen atom in its ground state and the electron gets excited by a photon. If we consider relativity the wave function cannot change instantly, right? The process has to be continous. What happens during this process....</p> | g16601 | [
0.02157416194677353,
0.03384901583194733,
0.008067207410931587,
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0.04416964575648308,
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0.0221771989017725,
0.05036146566271782,
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-0.022932903841137886,
-0.02200033888220787,
0.048840027302503586,
0.029149087145924568,
0.0057459... |
<p>I was wondering if there are demos of spin 1/2 systems that anyone knows of. Are there any classical systems that are symmetric under a rotation of $4\pi$ and not $2\pi$?</p> | g16602 | [
-0.03777848556637764,
-0.0036855563521385193,
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... |
<p>The question is about: </p>
<hr>
<p><strong>(1) whether giving a Lagrangian is sufficient enough to (uniquely) well-define a Hamiltonianian quantum theory with a Hilbert space?</strong></p>
<p>The answer should be Yes, or No.</p>
<p>If yes, then I suppose one can write any of its state function $|\Psi \rangle$ i... | g16603 | [
0.01871994137763977,
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0.005847370717674494,
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-0.030889341607689857,
0.003540779696777463,
0.02253904938697815,
-0.011786417104303837,
0.054... |
<p>I was thinking about how they have cans of compressed nitrogen for filling paint cans, and also that they sometimes will blow nitrogen in to food containers before sealing them, and that got me interested in extracting nitrogen for a nitrogen filled refrigerator. I read up on it and it appears the main way that nitr... | g16604 | [
0.032624658197164536,
0.014469979330897331,
0.03319139778614044,
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0.05934813991189003,
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0.025698160752654076,
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0.055... |
<p>The question is about defining <strong>``What is life?'' in the field of Physics</strong>.</p>
<p>Whether there is any (insightful) way of defining <a href="http://en.wikipedia.org/wiki/Life#Definitions" rel="nofollow">``What is life?''</a> from physicists. </p>
<p>There are pioneer works, including <a href="http:... | g16605 | [
0.021322807297110558,
-0.03253757581114769,
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0.041522249579429626,
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0.05676722154021263,
-... |
<p>I got a little puzzled when thinking about two entangled fermions.</p>
<p>Say that we have a Hilbert space in which we have two fermionic orbitals $a$ and $b$. Then the Hilbert space $H$'s dimension is just $4$, since it is spanned by
\begin{align}
\{ |0\rangle, c_a^\dagger |0\rangle, c_b^\dagger |0\rangle, c_a^\da... | g16606 | [
0.00039739449857734144,
-0.022569220513105392,
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0.05311891809105873,
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0.00778936268761754,
0.024661654606461525,
-0.0011593548115342855,
0.004043347667902708,
0.006675352342426777,... |
<p>This question cropped up while I was playing with the equation for time dilation. If I set the speed to be $i$ (imaginary unit) the answer from the equation still makes sense, but does that matter if the input data doesn't make sense? Or rather does the input data make sense?</p>
<p>Let $v=i$ and $c=2$ then $T' = T... | g16607 | [
0.036901868879795074,
0.04139550030231476,
0.007556802127510309,
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0.03495854511857033,
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0.06850628554821014,
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0.021803908050060272,
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0.03344549238681793,
0.00425788015127182,
-0.0363838... |
<p>To the question "What is the electric field outside a cylindrical solenoid when inside is turned on a magnetic field" the <a href="http://physics.stackexchange.com/questions/128002/what-is-the-electric-field-outside-a-cylindrical-solenoid">answer</a> is that outside exists a electric field. Does that mean that the f... | g16608 | [
0.03191888704895973,
0.05507175624370575,
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<p>I am starting to read many papers on electron beam physics; more specifically its motion in a magnet i.e. curved motion.</p>
<p>The term $R/\gamma^3$ comes up a lot, but I don't know where they are coming up with it. Any help or guidance would be very appreciated!</p>
<p><a href="http://www-ssrl.slac.stanford.edu/... | g16609 | [
0.03197465464472771,
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0.03170597925782204,
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-0.01261... |
<p>I am reading this paper where the definition of the bosonic state is mentioned on page 2 here :- <a href="http://arxiv.org/pdf/0806.1625.pdf" rel="nofollow">http://arxiv.org/pdf/0806.1625.pdf</a> . From a general definition of any density operator in terms of Wigner functions, it reduces to a Bosonic Gaussian for Ga... | g16610 | [
0.001123343245126307,
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... |
<p>We already have an answer why physically traveling faster than light would violate causality (the clock on board our hypothetical FTL spaceship would tick backwards to some outside observers).</p>
<p>However, would a wormhole-based FTL violate causality? In this case, never does an object actually move faster than ... | g16611 | [
0.04964730516076088,
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<p>In a recent paper (<a href="http://link.springer.com/chapter/10.1007/978-3-642-30870-3_53#page-1" rel="nofollow">http://link.springer.com/chapter/10.1007/978-3-642-30870-3_53#page-1</a>), G. Szekely and P.Nemeti wrote the following.
Let us consider two reference frames <em>A</em> and <em>B</em> initially, at event I... | g16612 | [
0.020244749262928963,
0.028716135770082474,
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0... |
<p>More an astronomy question, but Physics is the closest stack exchange category I could find and Google doesn't have the answer.</p>
<p>Granted, the sun's elevation changes for a given time of day throughout the year, easily explained by the earth's axial tilt.</p>
<p>Does it's bearing vary, by how much, and by wha... | g16613 | [
0.04126839339733124,
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0.028164628893136978,
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0.06401192396879196,
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-0.0007337798597291112,
0.024065565317869186,
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-0.0... |
<p>Note, my formal physics education ended over ten years ago so I may be missing some obvious piece of understanding.</p>
<p>The relationship between space-time and matter/energy distribution is described by Einstein's field equations:</p>
<p>$$G_{\mu\nu}=8\pi T_{\mu\nu}$$</p>
<p>G is a tensor that describes the ge... | g16614 | [
0.05263006314635277,
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-0.... |
<p><a href="http://en.wikipedia.org/wiki/F-theory" rel="nofollow">F-Theory</a>, as I understand it, is a realisation of Type IIB String Theory as a 12-dimensional theory in such a way that the $SL(2,\mathbb Z)$ symmetry becomes natural because Type IIB String Theory is F-Theory compactified on a torus. </p>... | g16615 | [
0.02106829173862934,
0.0528164841234684,
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0.044929616153240204,
-0.006... |
<p>First i'd like to apologize for both my writting skills (i'm not english) and for my physics knowledge (being them very basic and/or naive).</p>
<ul>
<li>With general relativity from Einstein, gravity is no longer labeled as a froce. However, i find it hard to understand what gravity is if it's not a force. I mean,... | g16616 | [
0.026352476328611374,
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0.020437246188521385,
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0.0216... |
<p>In deriving Euler's equations for fluid mechanics, in particular </p>
<p>$$f=\rho \partial_t v +\rho v\cdot \nabla v$$</p>
<p>for some body force $f$ (e.g Landau & Lifschitz 2.3) one assumes the continuity equation $\partial_t\rho=-\nabla\cdot\left(\rho v\right)$ and Newton's second law in the form $F=ma$ so $... | g16617 | [
0.07076043635606766,
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-0.009213116019964218,
0.02936305... |
<p>Let's consider</p>
<p>$$E_f^2=(mc^2)^2+(pc)^2$$</p>
<p>where the $mc^2$ is the rest energy due to the rest mass -- in Finnish "lepomassa". </p>
<p>$$ \sqrt{(mc^2)^2+(pc)^2} - mc^2~=~(\gamma-1)mc^2$$ </p>
<p>is the kinetic energy due to the movement because of momentum $p=\gamma mv$. </p>
<p>Now where is poten... | g16618 | [
0.03896099328994751,
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0.... |
<p>I'm working on a simple rocket flight simulation, and am trying to reproduce aspects of Goddard's first successful rocket flight. My sources put the empty weight at 5.75-6lbs, loaded weight 10.25-10.4 lbs, and thrust 9 lbs (40N), using a fuel-rich gasoline/LOX propellant with Isp of about 150. The rocket is supposed... | g16619 | [
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<p>My utility company charges me more for electricity in the summer. Is
there any way I could "save up" non-summer electricity (eg, a giant
battery?) and then use it during the summer, saving myself money?</p>
<p>Other power companies charge more for electricity during "peak hours"
daily, so even saving electricity fo... | g16620 | [
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<p>As today's <a href="http://en.wikipedia.org/wiki/1983_Soviet_nuclear_false_alarm_incident">the 29th anniversary of possible Armageddon</a>, had Mutual Assured Destruction taken place, with the USA and USSR exchanging most of their nuclear arsenal, what would someone</p>
<ol>
<li>In low earth orbit</li>
<li>On the m... | g16621 | [
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0.045620255172252655,
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0.044375449419021606,
0.01... |
<p>The Hubble constant, which roughly gauges the extent to which space is being stretched, can be determined from astronomical measurements of galactic velocities (via redshifts) and positions (via standard candles) relative to us. Recently a value of 67.80 ± 0.77 (km/s)/Mpc was published. On the scale of 1 A.U. the va... | g251 | [
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<p>I am reading the paper <a href="http://arxiv.org/abs/0807.4723">arXiv:0807.4723</a> by Gaiotto, Moore, and Neitzke on wall-crossing. I would like to understand whether if the Darboux coordinates in the mutually non-local case contain the information on the corrections to the N=2 Seiberg-Witten prepotential due to 4D... | g16622 | [
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0.... |
<p>If waves only move up and down, why is it that in the ocean you can move forward along a wave? I suppose it's a bit different then a normal wave because you have the action of the crest falling down, but I don't know how that happens either.
Where is the forward momentum coming from?</p> | g16623 | [
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0.0243... |
<p>The theory of general relativity tells me something about the global structure of space-time, eg simply connected ?</p> | g503 | [
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0.04173421859741211,
-0.006... |
<p>I.e., what properties of the spinors gives us a reason for using them for describing of wavefunctions of fermions?</p> | g16624 | [
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<p>Is there an elegant or easy way to derive the maximum distance from the origin to a point of the parabola created by projectile motion (assume initial position is the origin)? Other than differentiating with respect to $x$ and equate to zero the distance given by $\sqrt{x^{2}+y^{2}}$?</p> | g16625 | [
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... |
<p><img src="http://i.stack.imgur.com/ggTmN.png" alt="enter image description here"></p>
<p>I really wish someone could dissect this for me in the language of physics.</p>
<p>The system is that of two atoms that approximate each other along 'r' (or distance themselves apart). </p>
<p>My concerns are these: </p>
<ul... | g16626 | [
0.003752979217097163,
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-0.064547... |
<p>Simple question regarding pair production: Can a collision of an electron with a positron result in two photons? I have this problem to solve and I doubt this is even possible. Please provide some theoretical background (basics for start and if I need more explanation I will say so).</p>
<hr>
<p>EDIT:</p>
<p>Afte... | g16627 | [
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-... |
<p>I have the following sum of 10 terms:</p>
<p>$$
\delta^{ab}f^{cde} + \delta^{ac}f^{bde} + \delta^{ad}f^{bce} + \delta^{ae}f^{bcd} +
\delta^{bc}f^{ade} + \delta^{bd}f^{ace} + \delta^{be}f^{acd} + \delta^{cd}f^{abe} +
\delta^{ce}f^{abd} + \delta^{de}f^{abc}
$$</p>
<p>In other words I consider all permutations of 5 i... | g16628 | [
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0.028961511328816414,
0.024666495621204376,
-0.... |
<p>The electric field at any point at a finite distance z from the centre of a charged disc of uniform charge density along the axis of the disc is given by the equation:<br>
<img src="http://phy214uhart.wikispaces.com/file/view/22_21.gif/58087210/22_21.gif" alt="equation"></p>
<p>According to this equation, at z=0, t... | g16629 | [
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<p>I have one more s****d question in Polchinski's string theory book, Eqs. (2.3.14a)</p>
<p>$$ j^{\mu}(z) :e^{ik \cdot X(0,0)}:~ \sim~ \frac{k^{\mu}}{2 z} :e^{ik \cdot X(0,0)}:,$$</p>
<p>where $j^{\mu}_a =\frac{i}{\alpha'} \partial_a X^{\mu}$, $::$ is normal ordered, defined as
$$:X^{\mu}(z,\bar{z}): = X^{\mu} (z,... | g16630 | [
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<p>My brother had an idea for a DIY project and I am curious if the science works out well enough to try it.</p>
<p>The idea is to collect rainwater then mist it onto the air conditioners condenser coils (the hot side). The hypothesis is that the water mist will provide additional cooling because water is a better con... | g16631 | [
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<p>The title says it all. Is there a physical maximum value to the 3rd derivative of position? </p>
<p>Common Lore says that there is not and that jerk does not play any role in physics. My guess is that there is not as well. But my question is looking to stir the pot a bit. Have there been experiments on this? Has an... | g16632 | [
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<p>I understand that an isothermic process, plotted on a PV diagram, can be described by a rectangular hyperbola. </p>
<p>However, now I am wondering, what about an adiabatic process, what function best describes it?</p> | g16633 | [
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<p>How would you prove that $1/T$ is the most suitable integrating factor to transform $\delta Q$ to an exact differential in the second law of thermodynamics:
$$dS = \frac{\delta Q}{T}$$</p>
<p>Where $dS$ is the change in entropy, $\delta Q$ is the change in heat energy, and $T$ is the equilibrium temperature.</p> | g16634 | [
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<p>I have a problem:</p>
<p>Ok so I want to create a superposition qutrit state, like this:</p>
<p>$$
|\Psi\rangle=\frac{1}{\sqrt{3}}(|0\rangle+|1\rangle+|-1\rangle)
$$</p>
<p>is it possible to go there, starting with an initial state of $|0\rangle$ and appropriate $\pi/2$ (or any other pulses like $\pi$ $3\pi/2$ or... | g16635 | [
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<p>Now, we do have equipment to generate single photon at a time, and LASERs are nearly monochromatic. </p>
<p>While typing the question, am realizing that successive photons in case of single photon generation may have slightly different wavelengths, but are its single photons essentially monochromatic? Because we ma... | g16636 | [
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<p>It is well known that as a bar magnet falls freely through a coil, an electromotive force is induced in the coil by Lenz's Law.</p>
<p>However, it appears that the peak e.m.f induced (ignoring the direction) is higher after the passing through a coil, than before it passes through the coil. Why so?</p>
<p>My expla... | g16637 | [
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<p>This question has puzzled me for a long time. There is already a <a href="http://physics.stackexchange.com/a/33026/40382">question</a> like this on Physics.SE. John's answer to the question seems quite satisfying. But when I googled the cause I found <a href="http://shows.howstuffworks.com/brainstuff/hot-water-freez... | g16638 | [
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<p>I was thinking about how would capillary action change in a tube (classic example) and in a tube fitted inside another tube (considering water as the liquid involved).</p>
<p>Height of liquid column:
<img src="http://i.stack.imgur.com/P5s6S.png" alt="enter image description here">
where:</p>
<p>$\gamma$ = liquid-a... | g16639 | [
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0.011... |
<p>As we know, most of the mass of ordinary matter comes from the kinetic energy of quarks. This means kinetic energy of quarks contributes to the mass of any object. </p>
<p>However take a look at this question. </p>
<p><a href="http://physics.stackexchange.com/questions/95023/does-a-moving-object-curve-space-time-a... | g16640 | [
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<p>In ultracold atoms, it is generally talked of a <a href="http://www.google.com/search?as_q=degenerate+fermi+gas" rel="nofollow">degenerate Fermi gas</a>. What does <em>degenerate</em> mean here?</p> | g16641 | [
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<p>Just what the title states.</p>
<p>Photovoltaic cells convert incident light to electricity; this probably means they create less electricity when it is dark - as in deep space. </p>
<p>How far can a solar cell be taken from the Sun, and still be effective?</p> | g16642 | [
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<p>Two particles[or micro-observers] A and B are in relative uniform motion wrt each other in the x-x’ direction. The “observer” A decides to deduce[or interpret] the Lorentz Transformations wrt to B. Accurate knowledge of the position of B makes its[that of B] momentum highly uncertain.[$\Delta x \Delta p\ge h/2\pi$]<... | g16643 | [
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<p>Say for instance a person who was strong enough to lift double his body weight. If he placed his hands under his bottom and tried to lift$^1$ himself$^2$ off the ground, could he? </p>
<p>--</p>
<p>$^1$In a slowly, controlled motion; sudden jumps etc. are excluded.</p>
<p>$^2$ All parts of himself without touchin... | g16644 | [
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0.0... |
<p>I am trying to calculate the conductivity in the linear response regime of a disordered electron gas. (or eventually of a mean field Heavy fermion system with known one particle green's functions).</p>
<p>I trying to use method in "Quantum field theory of non-equilibium states" by J.Rammer. Specifically I'm looking... | g16645 | [
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<p>Interaction-free quantum experiments like Renninger's experiment or the Elitzur-Vaidman bomb tester are often taken to be examples of interaction-free measurements of a system. Unfortunately, such assumptions presuppose the ability to post-select in the future just to make sense. Interpretationally speaking, it is h... | g16646 | [
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<p>Is the spacetime continuous or discrete?
Or better, is the 4-dimensional spacetime of general-relativity discrete or continuous? What if we consider additional dimensions like string theory hypothesizes? Are those compact additional dimensions discrete or continuous? </p>
<p>Are there experimental evidences of cont... | g173 | [
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<p>Phonons are the quantum of lattice vibrations in crystals and are not to be confused with photons, the gauge bosons of the electromagnetic force. Apparently, they contribute to heat conduction, but I don’t understand why, as this is not explained in course 2062 of Aalto University.</p>
<p>So why is diamond a good h... | g16647 | [
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://physics.stackexchange.com/questions/234/how-should-a-physics-student-study-mathematics">How should a physics student study mathematics?</a> </p>
</blockquote>
<p>If some-one wants to do research in string theory for example, Would the Naka... | g108 | [
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<p>I'm trying to develop a very basic scaling law/unit analysis for viscous droplet formation, and I'd like to get some rough numerical values of the Reynolds number to play with. To be specific, I'm looking at the behavior of the smaller of the two droplets shown in the picture below (experimental setup shown sideways... | g16648 | [
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0.024377601221203804,
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<p>If rigid bodies $R_1$ and $R_2$ has exactly same total mass $M$, central of mass, and rotational inertia $I$, but different third moment of inertia $M_3$, how would they move/rotate differently? What's the observable phenomenon of the difference in their third moment of inertia?</p> | g16649 | [
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... |
<p>I'm looking for modern publications on the physical nature of life in which the primary reference is to the discussion started by Schrödinger in 1944 in his book "What is life". </p>
<p>For example, publications that suggest amendments (which have been generally accepted) to his ideas, similar books (not text books... | g16650 | [
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0.011571881361305714,
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<p>If there are particles that we are uncertain of are in a state of superposition, do they still function as they would when they are measured? For instance say there is a mechanical clock, and the gears are quantum in superposition, would the clock still function? Or would it be impossible since there is not a measur... | g16651 | [
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<p>To what size and how does "quantum weirdness" such as entanglement and superposition stop applying to larger objects (mere unions of these quantum particles). How do these macro objects that behave as classical mechanics not function like the very particles that they are made of?</p> | g16652 | [
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<p>I have been searching for the percentage of stars that are massive enough to end their lives as a <a href="http://en.wikipedia.org/wiki/Supernova">supernova</a> but couldn't get any result.
As far as I know, a star has to be at least 8 times more massive than the sun to go supernova, so what is the percentage of st... | g16653 | [
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<p>Question: An inductive coil has an internal resistance of 20 $\Omega$. When an AC Voltage source with a frequency of 100 Hz is connected to the coil, the current lags the voltage by 30 degrees. What is the value of the inductance L. </p>
<p>My Work: I am unsure where to begin here. If we know that $\omega_d=\frac{1... | g16654 | [
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<p>Synchrotron radiation is produced via the acceleration of charged particles, much like incandescence.
However, all information I've seen state that incandescent light is produced exclusively from the thermal motion of the charges.</p>
<p>Is there therefore a better term to describe the light produced via synchrotro... | g16655 | [
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<p>Consider the following problem</p>
<blockquote>
I pull a mass m resting at x = 0 on a frictionless table connected to a spring with some k by an amount A and let it go. What will be its speed at x=0?
</blockquote>
<p>I know how to solve it using the law of energy conservation but as a challenge I wanted to find th... | g545 | [
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<p>My understanding of quantum mechanics is that the state of a system is represented by a vector in multidimensional complex vector space. Is there, in principal, a state vector that represents a large, classical object such as, say, a cheeseburger, at an instant in time? If so, what is the physical meaning of that "s... | g16656 | [
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-0.01648470014333725,
-0.03653190657496452,
0.0119026442989707,
0.01... |
<p>I've noticed that many journal articles (in optics) use the phrase "Fourier frequency" to describe, well, the frequency of something.</p>
<ul>
<li><a href="http://scholar.google.com/scholar?q=%22Fourier+frequency%22&hl=en&btnG=Search&as_sdt=1%2C19&as_sdtp=on" rel="nofollow">Google scholar search for... | g16657 | [
0.01654166355729103,
-0.016979411244392395,
0.020522436127066612,
-0.0937691181898117,
0.0037690044846385717,
-0.01643209345638752,
-0.0013268832117319107,
0.04678192362189293,
-0.003610815852880478,
-0.013191908597946167,
-0.0004988369764760137,
-0.005011552479118109,
0.05542237311601639,
... |
<p>From <em>A Short History of Nearly Everything</em> by Bill Bryson:</p>
<blockquote>
<p>Atoms, however, go on practically forever. Nobody actually knows
how long an atom can survive, but according to Martin Rees it is
probably about 10^35 years</p>
</blockquote>
<p>Can anybody explain this result to me?</p>... | g16658 | [
0.04504118487238884,
0.014582681469619274,
0.013520834967494011,
-0.007341565564274788,
-0.023603860288858414,
0.05850968882441521,
-0.0136141711845994,
0.06115773320198059,
0.014801439829170704,
-0.048692092299461365,
0.003416342893615365,
0.013032641261816025,
0.014650160446763039,
-0.00... |
<p>I was wondering how one obtains geometric quantization from a path integral. It's often assumed that something like this is possible, for example, when working with <a href="http://en.wikipedia.org/wiki/Chern%E2%80%93Simons_theory" rel="nofollow">Chern-Simons theory</a>, but rarely explained in detail. One problem... | g16659 | [
0.04972575604915619,
0.006834494415670633,
-0.013934068381786346,
-0.0031647540163248777,
-0.029764553532004356,
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0.03386266902089119,
0.0529845766723156,
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0.03317806124687195,
-0.024314776062965393,
-0.05571802332997322,
-0.0016895688604563475,
0... |
<p>I was just watching the movie "Frozen" (not the Disney one), and they were trapped in a ski lift 50 feet off the ground. They had to jump. My question is, when they jump, should they swing on the lift towards up the hill or down the hill? If they swing up the hill, it will be a shorter drop. If they swing down t... | g16660 | [
0.002846789313480258,
0.05995428189635277,
-0.006588783115148544,
0.030170820653438568,
0.011721370741724968,
0.07708261162042618,
0.03339902311563492,
0.0013143931282684207,
-0.05254755914211273,
0.01510076317936182,
-0.0392971895635128,
0.03192288056015968,
-0.02976527065038681,
-0.04933... |
<p>I am not sure that this notation is specific to supersymmetry theories but I ran into this while studying that. </p>
<p>I see people talking of component fields of a chiral superfield as $\phi$ and $\bar{\psi}$ in the adjoint representation of some gauge group. (One sometimes also seems to use the notation of $\bar... | g16661 | [
0.020651239901781082,
0.014770467765629292,
-0.026474663987755775,
-0.020892145112156868,
0.07221750169992447,
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0.0652957558631897,
0.08064420521259308,
0.032914552837610245,
-0.009532122872769833,
-0.029334329068660736,
0.015619371086359024,
-0.004898006562143564,
0.... |
<p>Is it possible to indicate if objects after collision will stick together knowing their properties(materials,hardness,etc)?</p> | g16662 | [
0.00438870070502162,
-0.001226549269631505,
0.020753055810928345,
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0.06997273117303848,
0.012695936486124992,
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0.0007983746472746134,
0.011600654572248459,
-0.04527946561574936,
-0.0021835786756128073,
... |
<p>Is the electron the only subatomic particle that can absorb and emit a photon?</p> | g16663 | [
0.02578010782599449,
0.027515336871147156,
0.004087572917342186,
0.024236982688307762,
0.012282908894121647,
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0.07175315171480179,
0.030860697850584984,
-0.01159503310918808,
0.022324316203594208,
0.08005990087985992,
0.022838497534394264,
-0.01034... |
<p>What is the '<strong><em>molecular</em></strong>' origin of the <strong><em>viscosity</em></strong>? The molecular origin of elasticity is almost clear for me: at the very bottom the 'elasticity' comes from the attraction and repulsion between atoms when they are reasonably far from each other or very close (like Le... | g16664 | [
0.0692901760339737,
-0.00025004599592648447,
0.007340114563703537,
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0.03840535879135132,
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0.04065000265836716,
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-0.012800452299416065,
-0.03615984320640564,
-0.000299075007205829,
0.015345834195613861,
-0... |
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