question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>I'm currently reading about the Carnot cycle and its significance on the formulation of entropy (because I want to try to understand the concept better), but I can't seem to answer the following question:</p>
<ul>
<li>Why are <a href="http://en.wikipedia.org/wiki/Functions_of_state" rel="nofollow">state functions</... | g19239 | [
-0.024063225835561752,
0.031009193509817123,
-0.0004277794505469501,
-0.08073297888040543,
0.031894832849502563,
-0.04001191630959511,
0.03444294258952141,
0.046670619398355484,
-0.05551035702228546,
-0.0296083502471447,
-0.061315957456827164,
-0.029917433857917786,
0.05424455180764198,
-0... |
<p>I want to know how the density operator of a system evovles when we use path integral approach.</p> | g19240 | [
0.022350741550326347,
0.0553508959710598,
-0.0019615874625742435,
0.008027483709156513,
0.008830154314637184,
-0.00542481429874897,
-0.010253043845295906,
-0.01787712052464485,
-0.032317038625478745,
0.051252759993076324,
-0.019021673128008842,
-0.01771472580730915,
0.06316450983285904,
0.... |
<p>Generate an entangled pair of qubits. Send to Alice and Bob far away from each other. Both measure along basis in one of two possible orientations. The result is sent to Charlie at some later time, who compares the corellations and concludes the Bell inequalities have been violated.</p>
<p>But in Copenhagen, Charli... | g19241 | [
-0.005009675398468971,
0.029008371755480766,
0.028668848797678947,
-0.09659907221794128,
0.02612956054508686,
0.015771303325891495,
-0.001239411416463554,
0.04753674939274788,
-0.001990352524444461,
-0.018489165231585503,
-0.08108572661876678,
0.005792701151221991,
-0.021206645295023918,
-... |
<p>I know of X-Ray diffraction, which produces a pattern corresponding to the inverse Fourier Transform of the lattice (reciprocal lattice). While this method is widely employed, it provides more information than I need - I don't want to find out what Bravais lattice I'm examining, but just how homogeneous this lattice... | g19242 | [
0.02148948796093464,
0.0016456992598250508,
-0.008149742148816586,
-0.020945684984326363,
0.019702589139342308,
-0.07205495238304138,
-0.040103573352098465,
0.011312177404761314,
0.02660577930510044,
0.017683735117316246,
0.047572433948516846,
0.052925605326890945,
0.01002589799463749,
-0.... |
<p>I've just read that 68 years ago <em><a href="http://en.wikipedia.org/wiki/Little_Boy">Little Boy</a></em> was dropped on Hiroshima, which made me wonder about some rather historical facts about the development of the first nuclear bombs; they seem to be several questions, but they boil down to the same thing: the t... | g19243 | [
0.012974406592547894,
0.02669677883386612,
0.005230711307376623,
0.05390666052699089,
0.039116475731134415,
0.06696474552154541,
0.0064615290611982346,
0.013157681562006474,
-0.016849422827363014,
-0.048874858766794205,
-0.0910850316286087,
0.005861345212906599,
0.008814772590994835,
0.023... |
<p>I have the following infotmation:</p>
<p>Amplitude-Function: $U(k) = Ae^{-a|k-k_0|}$<br>
Wave Function: $u(x,t) = \frac{A}{\sqrt{2\pi}} \frac{2a}{(x-vt)^2+a^2}e^{ik_0(x-vt)}$<br>
Uncertainty in x: $\Delta x = 1$ (Linear dispersion-relation).<br>
Uncertainty in k: $\Delta k = \frac{1}{\sqrt{2a}}$<br>
And finally $a ... | g19244 | [
0.01644905097782612,
-0.0329238697886467,
-0.0011889570159837604,
-0.011997940018773079,
-0.0012751480098813772,
-0.012615012936294079,
0.02271331287920475,
0.024186166003346443,
-0.02843838930130005,
-0.025865400210022926,
-0.011171037331223488,
0.06298524141311646,
0.03261803090572357,
-... |
<p>What's the difference between "ortibal" and "orbit"?
Which one should be used in physics?
In quantum mechanics, is "atomic orbital" or "atomic orbit" used?
And what about in classical mechanics? A particle's orbit or orbital?</p> | g19245 | [
0.02047380432486534,
0.032317619770765305,
0.0005633757682517171,
-0.02079840935766697,
0.03188387304544449,
-0.03567657992243767,
-0.027073832228779793,
-0.0027177243027836084,
0.03292090445756912,
-0.0075691454112529755,
0.05383770912885666,
0.018391970545053482,
0.021447153761982918,
-0... |
<p>I'm doing an experiment where I have to calculate the stretch of a spring needed for it to launch itself into a trashcan located some distance away.
The spring is located on the edge of a ramp that is 1.13 m high. The angle of the ramp is 30 degrees above horizontal. The spring constant of the spring is 175 N/m. Th... | g19246 | [
0.09520477801561356,
0.00998615100979805,
0.007249855902045965,
-0.0046880124136805534,
0.030200451612472534,
-0.003526140935719013,
-0.011792798526585102,
-0.027246704325079918,
-0.05387497693300247,
-0.0005238046869635582,
-0.02631615288555622,
0.02377629280090332,
0.00869869813323021,
-... |
<p>I have a question in deriving Eqs. (3.6.15b) and (3.6.15c) in Polchinski's string theory vol I p. 105. </p>
<p>Given </p>
<blockquote>
<p>$$\Delta (\sigma,\sigma') = \frac{ \alpha'}{2} \ln d^2 (\sigma, \sigma') \tag{3.6.6}$$
where $d(\sigma,\sigma')$ is the geodesic distance between points $\sigma$ and $\sigma... | g631 | [
0.030042782425880432,
-0.050010934472084045,
-0.007691596634685993,
-0.07515490055084229,
0.043590959161520004,
0.02572273090481758,
0.05977887660264969,
-0.014333466067910194,
-0.010571357794106007,
-0.03229236975312233,
-0.04205060377717018,
0.018640946596860886,
0.0601908341050148,
-0.0... |
<p>One simple way of detailing the very basic structure of the nuclear shell model involves placing the nucleons in a 3D isotropic oscillator. It's easy to show that the energy eigenvalues are $E = \hbar\omega\left(n+\frac{3}{2}\right)$ with a degeneracy of $D(n) = \frac{1}{2}(n+1)(n+2)$, where $n = n_1 + n_2 + n_3 = ... | g19247 | [
-0.009060063399374485,
0.05812905356287956,
0.002608939539641142,
0.011260692030191422,
0.058406081050634384,
0.006872946862131357,
0.03138808161020279,
0.02470415271818638,
-0.03863358870148659,
0.019282052293419838,
-0.007989956997334957,
-0.002433766843751073,
0.06428249180316925,
0.055... |
<p>This article at NewScientist magazine (subscription required) describes entangling photons by passing them through a half silvered mirror.</p>
<p><a href="http://www.newscientist.com/article/mg21929282.100-quantum-weirdness-the-battle-for-the-basis-of-reality.html">http://www.newscientist.com/article/mg21929282.100... | g19248 | [
0.004960300400853157,
0.023920129984617233,
0.017567787319421768,
0.03154561668634415,
0.06867760419845581,
0.018304791301488876,
0.01823532022535801,
0.04432950168848038,
0.04557399824261665,
0.02798614650964737,
0.0039617265574634075,
0.0003727468429133296,
0.03475343436002731,
0.0280661... |
<p>Why does the attractive Dirac Delta distribution (function) <a href="http://en.wikipedia.org/wiki/Delta_potential" rel="nofollow">potential</a> $V = \alpha\delta$(x) (for negative $\alpha$) yield both bound AND scattered states? Is this due to the definition of the Dirac delta distribution? Or is it for a different ... | g19249 | [
0.03382980450987816,
0.027549363672733307,
-0.020649779587984085,
-0.01600130833685398,
0.03375959023833275,
0.05590643361210823,
0.027745723724365234,
0.01605464704334736,
-0.0022159330546855927,
-0.09601009637117386,
-0.026323575526475906,
-0.02072099596261978,
0.05335809290409088,
0.057... |
<p>Einstein showed in various papers that the energy content of a body was a measure of its inertial mass. If you increase the internal energy of a system while keeping the center of energy at rest, its effective inertial mass increases because of the increase of energy required to move the center of energy from rest t... | g19250 | [
0.018685366958379745,
-0.003979139495640993,
0.009429121389985085,
0.0014129576738923788,
-0.04231559485197067,
0.016638973727822304,
0.014119238592684269,
0.04047512635588646,
-0.06440293043851852,
0.035288505256175995,
0.006889747455716133,
-0.043654803186655045,
-0.019067618995904922,
-... |
<p>I understand that bounded states in quantum mechanics imply that the total energy of the state, $E$, is less than the potential $V_0$ at + or - spatial infinity. Similarly, the scattering state implies that $E > V_0$.</p>
<p>But I do not understand why for bounded states, the complete set of wave-function soluti... | g19251 | [
0.03788229450583458,
-0.018763309344649315,
-0.016765372827649117,
-0.003716583363711834,
0.007275192067027092,
-0.025493167340755463,
-0.0018612835556268692,
0.03664903715252876,
0.010581144131720066,
-0.056695595383644104,
0.0336262509226799,
-0.07710901647806168,
0.03742295876145363,
-0... |
<p>Before 1968, the units for absolute temperature were described as "degrees Kelvin" or "degrees absolute." After that, the SI system got rid of the idea of "degree" for absolute temperature, so the new unit should apparently be expressed as a "kelvin" (with lowercase k) and abbreviated simply "K" (without the degree... | g19252 | [
0.020846441388130188,
-0.03185782581567764,
0.022397875785827637,
-0.0399879589676857,
-0.012053491547703743,
-0.01709792949259281,
-0.018695496022701263,
0.04340772703289986,
-0.0014185570180416107,
0.04790884256362915,
0.02396467700600624,
-0.011887088418006897,
0.04976649209856987,
0.00... |
<p>I have a question about equation (17) of this paper: <a href="http://arxiv.org/pdf/1009.1635v1.pdf" rel="nofollow">http://arxiv.org/pdf/1009.1635v1.pdf</a></p>
<p>First, I was hoping that someone could explain how it is arrived at.</p>
<p>Second, I find the notation to be a bit perplexing--I do not quite understan... | g19253 | [
0.033395931124687195,
0.025434130802750587,
-0.021611694246530533,
-0.024770932272076607,
0.038943760097026825,
-0.06845363229513168,
0.08990569412708282,
0.01608123816549778,
-0.04917529225349426,
-0.005042551551014185,
-0.03977413475513458,
0.07897591590881348,
0.0442674495279789,
-0.021... |
<p>I wanted to ask why a pulse that reaches to a free end will reflect off and return with the same direction of displacement that it had before reflection.
I am looking for explanation with forces.</p> | g19254 | [
0.06633060425519943,
0.018300272524356842,
-0.01750965788960457,
-0.0271578598767519,
0.05206756293773651,
0.08856979757547379,
0.011861530132591724,
0.027602776885032654,
-0.012691413052380085,
-0.07845369726419449,
-0.030456045642495155,
0.029595259577035904,
0.018793480470776558,
-0.050... |
<p>When finding the potential energy of a dipole in a uniform electric field, I was told by my lecturer that the convention is that the potential energy is 0 when the dipole moment and electric field vectors are perpendicular. I don't understand why this is so, when it would make sense if the potential was zero when th... | g19255 | [
0.014743215404450893,
0.02918366529047489,
-0.008009310811758041,
-0.051195234060287476,
0.02452302724123001,
-0.0008736322051845491,
0.025050543248653412,
0.08397231251001358,
-0.05186003819108009,
-0.004942835308611393,
-0.0356237031519413,
-0.05050912871956825,
-0.02821141853928566,
-0.... |
<p>This is a very specific question about Robert Zwanzig's book <em>Nonequilibrium Statistical Mechanics</em>.</p>
<p>Specifically, what is he talking about in equation 1.25 on page 10 that he calls "an average over noise", and how is it calculated?
$$\left<v\left(t\right)\right>_\text{noise}=e^{-\frac{\xi t}{m}... | g19256 | [
0.03607478365302086,
-0.013330221176147461,
0.008429511450231075,
-0.05603615567088127,
0.009128515608608723,
-0.014127394184470177,
0.07719383388757706,
0.008793647401034832,
-0.06259871274232864,
0.030808640643954277,
-0.046139635145664215,
0.03366325795650482,
0.02686222828924656,
0.062... |
<p>I was doing this experiment: i take a plastic cup, put in a container of water, it floats – then when I put a coin in the water, it sinks and rests at the bottom. </p>
<p>So to make the cup sink, i fill it with water – and the cup sinks, but it sinks until it's totally submerged with water and stops ( doesn't sink ... | g19257 | [
0.052114930003881454,
0.03582953289151192,
0.01884106919169426,
-0.03623856604099274,
0.0919022187590599,
0.08978062868118286,
0.01928996481001377,
0.0004932809388265014,
-0.08286074548959732,
-0.04595348238945007,
-0.02711491473019123,
0.015388371422886848,
0.0025557756889611483,
-0.05545... |
<p>In this post: <a href="http://physics.stackexchange.com/questions/8373/dimensionless-constants-in-physics/8376#8376">Dimensionless Constants in Physics</a> there is a discussion about dimensionful vs. dimensionless constants in physics. In the context of this discussion, I'm wondering about the significance of setti... | g19258 | [
0.024578191339969635,
0.021324720233678818,
0.010175029747188091,
0.000022039208488422446,
0.011951697058975697,
0.016964437440037727,
0.016968926414847374,
0.05630280822515488,
-0.04844648763537407,
0.01685069128870964,
0.02355864644050598,
0.03765145689249039,
-0.03905594348907471,
0.033... |
<p>So I know that for an electromagnetic field in a vacuum the Lagrangian is $\mathcal L=-\frac 1 4 F^{\mu\nu} F_{\mu\nu}$, the standard model tells me this. What I want to know is if there is an elementary argument (based on symmetry perhaps) as to why it has this form. I have done some searching/reading on this, but ... | g19259 | [
0.04837394133210182,
-0.0017455575289204717,
-0.011175043880939484,
-0.043711647391319275,
0.08335789293050766,
0.06737324595451355,
0.0418824777007103,
0.010605139657855034,
-0.06147248297929764,
-0.07456760108470917,
-0.022490473464131355,
-0.004676593467593193,
0.016067039221525192,
0.0... |
<p>I have a hard time understanding the subject of fictitious forces. Let's discuss a few examples:</p>
<p>1) I'm sitting inside a vehicle which is accelerating in a straight line. I feel like someone is pushing me to the seat. So, on the one hand, I'm told that this happens according to the third Newton's law: this p... | g19260 | [
0.014022105373442173,
0.0674993023276329,
-0.006970440503209829,
0.04051300510764122,
0.07683920115232468,
0.019516902044415474,
0.023788822814822197,
0.010009811259806156,
-0.037543103098869324,
-0.020821578800678253,
0.02799244597554207,
-0.008904966525733471,
-0.0034997507464140654,
0.0... |
<p>Imagine a long circuit that goes around the Earth, or just spans a large enough distance to measure the effect, say 100'000 km.</p>
<p>The circuit has efficient light bulbs installed at each 10km mark.
There is a power source connected which powers all the light bulbs.</p>
<p>Time N = all light bulbs are lit. </p>... | g19261 | [
0.03347376361489296,
0.013393272645771503,
0.008147318847477436,
-0.024741042405366898,
0.015283673070371151,
-0.025415653362870216,
0.06140735372900963,
0.057648781687021255,
-0.060595281422138214,
-0.00005610306834569201,
-0.03033110871911049,
0.07032306492328644,
-0.00886999536305666,
0... |
<p>There has been numerous question, some violent even in physics@SE regarding PEP and EM forces.</p>
<p>But what baffles me is what is degeneracy pressure? I know there are 4 fundamental forces- EM, gravity, weak and strong.</p>
<p>But then degeneracy comes along in everywhere, from neutron star to the electronic co... | g19262 | [
-0.0010952998418360949,
0.04533446580171585,
-0.002757226349785924,
-0.0037794506642967463,
0.07172023504972458,
0.034372832626104355,
-0.011349950917065144,
0.022170450538396835,
-0.03158598393201828,
-0.010316101834177971,
0.0006973011768423021,
-0.040861260145902634,
0.0002841988170985132... |
<p>Let's take a wire or a rope. I usually do this with a chain or my scarf.</p>
<p>I fixate one end in my hand and apply rotation (by subtle movements of this endpoint like spinning a lasso). The rope gets into rotation and obtains certain bent shape:
<img src="http://i.stack.imgur.com/VO4DP.jpg" alt="enter image desc... | g19263 | [
0.04467301070690155,
-0.05100543424487114,
-0.0192088782787323,
-0.017106283456087112,
0.06973598897457123,
-0.052774298936128616,
0.058964427560567856,
0.015793275088071823,
0.01645602099597454,
-0.01547013409435749,
-0.02917540818452835,
0.008084322325885296,
0.017202984541654587,
0.0014... |
<p>There has been a long discussion between me and Anna V on if the products of the annihilation will really cause a fireball to form and we haven't settled it yet.</p>
<p>Our point here is that gamma rays from the annihilation are too energetic to be absorbed by the atmosphere in a short time or a little space to act... | g19264 | [
0.06674592196941376,
0.048213910311460495,
0.05090344697237015,
0.03836525231599808,
0.020598994567990303,
0.08807836472988129,
-0.01493004895746708,
0.031337808817625046,
0.018540415912866592,
-0.041471146047115326,
-0.01266559399664402,
-0.01117993239313364,
0.009276200085878372,
-0.0153... |
<p>I want to show that the determinant of the field $detF$ at the point $X \in B$ is positive, when the following motion.</p>
<p>I think that time derivative of Jacobin is positive for $t > 0$.
However, I cannot see how this helps. </p>
<p><strong>How to start to show that the $det F(X, t) > 0$?</strong></p>
<... | g19265 | [
0.039738863706588745,
0.03846009448170662,
-0.014403105713427067,
-0.014702139422297478,
0.05530676990747452,
-0.02045946940779686,
0.03620343655347824,
0.023930083960294724,
-0.03233536332845688,
0.012770953588187695,
-0.06638464331626892,
0.04335416853427887,
0.016875119879841805,
0.0171... |
<p><a href="http://en.wikipedia.org/wiki/Magnetic_levitation">Magnetic levitation</a> has been used to suspend frogs in midair. I was wondering: Does the animal still feel gravitational pull? I mean: Does the frog feel like an astronaut on the ISS, or does he feel like a trapeze artist suspended by a harness?</p> | g19266 | [
-0.04678540304303169,
0.005711650010198355,
0.0024105131160467863,
-0.02275444194674492,
-0.049187105149030685,
0.03462216258049011,
-0.026730628684163094,
-0.005212937947362661,
-0.04149400442838669,
-0.030716199427843094,
-0.0032988206949084997,
-0.01412572804838419,
-0.012054755352437496,... |
<p>I am preparing for my quals and stumbled across the following problem, and although it only requires undergraduate-level physics, I feel I can't piece everything together.</p>
<p>"A rocket of mass $m_0$ is propelled by a giant monochromatic laser mounted on the back of the rocket. The laser emits a beam with a powe... | g19267 | [
0.04999036341905594,
-0.04219171777367592,
-0.0023721640463918447,
-0.045942917466163635,
0.039537813514471054,
-0.019361482933163643,
0.0242846067994833,
-0.017132176086306572,
-0.0419449508190155,
0.02032593823969364,
0.03499816730618477,
0.0302155539393425,
0.012457495555281639,
0.03533... |
<p>I have heard from several physicists that the Kapustin-Witten topological twist of $N=4$ 4-dimensional Yang-Mills theory ("the Geometric Langlands twist") is not expected to give
rise to fully defined topological field theory in the sense that, for example, its partition function on a 4-manifold (without boundary) i... | g19268 | [
0.020461997017264366,
0.018579507246613503,
-0.01788489706814289,
0.016014965251088142,
0.013868576847016811,
0.03072526305913925,
0.04828502982854843,
0.03998325392603874,
-0.030643245205283165,
-0.03821965306997299,
0.008059173822402954,
-0.06213616579771042,
0.08545614033937454,
-0.0383... |
<p>Consider 2 mirrors which intersect at an angle. If we draw a light ray intersecting the mirrors at their point of intersection, how will it reflect?</p>
<p>What will be the normal at that point?</p>
<p><img src="http://i.stack.imgur.com/4nnNy.png" alt="enter image description here"></p> | g19269 | [
-0.020021911710500717,
-0.0014835463371127844,
0.006660172250121832,
0.0021840629633516073,
0.009594467468559742,
0.007481323555111885,
0.02410976216197014,
0.030638445168733597,
-0.023259812965989113,
-0.006123237777501345,
0.007129780948162079,
0.052238062024116516,
0.03675323352217674,
... |
<p>This question is a continuation of this <a href="http://theoreticalphysics.stackexchange.com/questions/978/some-questions-about-the-bcfw-reduction">previous question</a> of mine and I am continuing with the same notation. </p>
<p>One claims that one can actually split this $n$-gluon amplitude such that there is jus... | g19270 | [
-0.002284831367433071,
-0.007973052561283112,
-0.016987113282084465,
-0.03837936371564865,
0.030179621651768684,
-0.040466729551553726,
0.07476374506950378,
0.04392315447330475,
-0.010744720697402954,
-0.03419323265552521,
-0.045277390629053116,
0.04249367490410805,
-0.021932560950517654,
... |
<p>For a $n$-qubit state $\rho$ we perform all projective measurement consisting of one-particle measurements in the same basis, that is,</p>
<p>$$p_{i_1i_2\ldots i_n}(\theta,\varphi) = \text{Tr}\left \{ \rho [P_{i_1}(\theta,\varphi)\otimes P_{i_2}(\theta,\varphi) \otimes \ldots\otimes P_{i_n}(\theta,\varphi)] \rig... | g19271 | [
-0.008209639228880405,
0.010877177119255066,
-0.020256541669368744,
-0.0411999374628067,
0.0755145326256752,
-0.03384874016046524,
-0.01181748602539301,
-0.030945057049393654,
0.011602388694882393,
0.021114809438586235,
-0.016723811626434326,
0.027959659695625305,
-0.03557298332452774,
0.0... |
<p>I'm trying to understand how can one transmit different signals on a same copper wire using different frequencies. How does the electrons actually interact with the frequency? And how does the frequency relates to the speed of a connection?</p> | g19272 | [
0.0021694444585591555,
0.04375067725777626,
0.007762945722788572,
0.009419867768883705,
0.05819253996014595,
-0.04690392315387726,
-0.01431733276695013,
-0.02839859575033188,
-0.045503124594688416,
0.0017789012053981423,
-0.03359448164701462,
0.033491019159555435,
-0.023003095760941505,
0.... |
<p>We know all galaxies spread out after <a href="http://en.wikipedia.org/wiki/Big_Bang" rel="nofollow">Big Bang theory</a>.The key idea is that the universe is expanding after that theory. Can we play back the scenes via observable universe (galaxies) and can we calculate the coordinate of big bang point as a fixed r... | g10 | [
0.03523445501923561,
0.00981211569160223,
-0.005216219462454319,
-0.011629672721028328,
-0.014014908112585545,
0.029066206887364388,
0.006520926486700773,
0.0018077577697113156,
-0.01673845760524273,
-0.06391604989767075,
0.07618528604507446,
0.010096913203597069,
0.04358101636171341,
0.03... |
<p>I keep working through this problem and getting the wrong answer: </p>
<blockquote>
<p>A spring with spring constant k is positioned vertically and then
compressed from its equilibrium length by a distance Δy. A ball of
mass m is placed on top of the spring, and is launched into the air
when the spring is r... | g19273 | [
0.06438010185956955,
0.026852725073695183,
-0.001749487011693418,
0.041331611573696136,
0.0023242041934281588,
-0.01036760676652193,
0.03152356296777725,
-0.013014881871640682,
-0.06811028718948364,
0.002488798461854458,
-0.06425239145755768,
0.04031360149383545,
0.0069205001927912235,
0.0... |
<p>Is it possible to imagine micro blackhole set creating hawking radiation soliton convergence that forms new micro black hole? If so, is there a configuration of micro black hole that would loop?</p> | g19274 | [
-0.03547373786568642,
0.017233500257134438,
0.03553810343146324,
-0.008726833388209343,
-0.01647508144378662,
0.012187332846224308,
-0.02696245349943638,
-0.006664432119578123,
-0.01943727396428585,
-0.02044598013162613,
-0.008601573295891285,
0.016031499952077866,
0.021888161078095436,
0.... |
<p>I've tried doing research on this and there are some similar questions. However, they have slightly different scenarios and to make sure I understand things perfectly, I wanted to word it into my own words and confirm that my thought process is correct. I am just getting back into physics after a decade of not do... | g19275 | [
0.07654648274183273,
0.021283971145749092,
0.011953587643802166,
0.005666864570230246,
0.02526102587580681,
0.03333805501461029,
0.01812564767897129,
0.013165710493922234,
-0.0993683710694313,
-0.019582252949476242,
-0.011320186778903008,
0.0118721853941679,
0.02188790962100029,
0.01974828... |
<p>In my view, this is one of the most profound unsolved mysteries of Science. How to explain the fine tuning of the Universe without recourse to saying that a God/Designer did it.</p>
<p>Examples of fine tuning:</p>
<p>We exist because of a crucial one part in a billion difference that favors matter over antimatter.... | g19276 | [
0.032581355422735214,
0.07968618720769882,
0.003855314804241061,
0.03187005966901779,
0.014301604591310024,
0.05711764842271805,
0.031639885157346725,
-0.017955977469682693,
0.008456839248538017,
-0.10183395445346832,
0.018393253907561302,
-0.013362723402678967,
0.055530283600091934,
0.048... |
<p>With the FLRW equations we can get solutions for a matter dominated closed universe in which the finale is an ultimate collapse, but this is only in terms of $a$ (the scale factor) and $t$ (time) and some $q_0$ and $\theta$:</p>
<p>$a = {\frac {q_0}{2 q_0 -1 } } (cosh (\theta) -1) $, (1)</p>
<p>$t = {\frac... | g19277 | [
0.020407017320394516,
-0.04878002032637596,
0.006134959869086742,
0.012030678801238537,
-0.01250182744115591,
0.005937154870480299,
0.030640719458460808,
0.015239420346915722,
-0.04996675252914429,
-0.0023583255242556334,
-0.017155088484287262,
-0.014528951607644558,
0.014668548479676247,
... |
<p>Alternatively, why does the force created by blowing out air feel so much stronger than the force created by sucking in air?</p>
<p>Ok, so forget the human factor involved in <em>blowing out candles</em>. Consider a vacuum cleaner with a suction end and a blower end. Anyone who has tried it out notices the blower e... | g19278 | [
0.06000678613781929,
0.04405837506055832,
-0.0009248765418305993,
0.04165159538388252,
0.015030410140752792,
0.0641297698020935,
-0.005235795862972736,
0.056175779551267624,
-0.010350039228796959,
-0.04563576728105545,
0.03373996168375015,
-0.02925797365605831,
-0.02389872446656227,
0.0250... |
<p>I am a quantum computing enthusiast, and recently I stumbled upon this the following two propositions:</p>
<p>$$ \alpha|1\rangle + \beta|0\rangle$$</p>
<p>What does this mean? </p>
<p>My understanding of this is that: the two bits, 1 and 0 are represented in a state of superposition, hence the bra-ket notation (w... | g19279 | [
0.023462077602744102,
0.015442696399986744,
-0.015427244827151299,
-0.07043052464723587,
0.021102605387568474,
0.0022394719999283552,
0.03695578873157501,
0.04511793330311775,
-0.00890446174889803,
-0.017347177490592003,
-0.04780192673206329,
-0.004127399064600468,
0.026656603440642357,
-0... |
<p>How clearly can the stars of the <a href="http://en.wikipedia.org/wiki/Pleiades" rel="nofollow">Pleiades</a> cluster be seen through a 15x telescope (for example, <a href="http://www.telescope.com/FunScope-76mm-Tabletop-Reflector-Telescope/p/9766.uts" rel="nofollow">FunScope</a>)?</p> | g19280 | [
-0.09745470434427261,
0.05161571502685547,
-0.028468690812587738,
-0.09358534961938858,
0.04391995072364807,
0.002794227097183466,
-0.0037695993669331074,
0.003393624909222126,
0.06386485695838928,
-0.02024015597999096,
0.08430564403533936,
0.06803835928440094,
0.06838586926460266,
-0.0185... |
<p><a href="http://en.wikipedia.org/wiki/Mercury_%28planet%29" rel="nofollow">From Wikipedia</a>:</p>
<blockquote>
<p>Although the daylight temperature at the surface of Mercury is generally extremely high, observations strongly suggest that ice exists on Mercury.</p>
</blockquote>
<p>Does that mean there could be ... | g19281 | [
0.017345907166600227,
0.038551799952983856,
0.006167605984956026,
-0.022816797718405724,
0.017164556309580803,
0.07277841120958328,
0.010883539915084839,
0.04804210364818573,
-0.004828243050724268,
-0.03597690537571907,
0.031126683577895164,
0.04147152602672577,
-0.058978527784347534,
-0.0... |
<p>This is really several related questions...</p>
<p>The equations of classical electrodynamics are time-reversal invariant. However, when we solve the equations for a particular system of charges it is common to take the solution with only retarded fields. The reason given for this choice is usually so that the solu... | g19282 | [
0.06035231053829193,
-0.009809345938265324,
-0.00015699921641498804,
0.021841488778591156,
0.10765077918767929,
0.018023081123828888,
0.038788050413131714,
0.016568467020988464,
-0.020954808220267296,
0.03231227025389671,
0.014536323957145214,
0.04753245785832405,
-0.06181514263153076,
0.0... |
<p>I am sitting in a cigar lounge, and under the jazz music playing I can hear this strange, rising and falling tone, that sounds similar to one of those <em>weird tubes</em> you can find at a fun fair. You tilt the tube this way, and tip it that way, and a weight moves in the tube and creates a <em>weird tube</em> sou... | g19283 | [
-0.0061819120310246944,
-0.01389006245881319,
-0.004045549314469099,
-0.061592794954776764,
0.003052114276215434,
0.022577686235308647,
-0.0206279493868351,
0.011831583455204964,
-0.05225563049316406,
-0.017310328781604767,
-0.036316968500614166,
-0.006852465681731701,
0.060969751328229904,
... |
<p>I have a pretty good knowledge of physics but couldn't understand what a <a href="http://en.wikipedia.org/wiki/Tensor" rel="nofollow">tensor</a> is. I just couldn't understand it, and the wiki page is very hard to understand as well. Can someone refer me to a good tutorial about it?</p> | g514 | [
0.0021570506505668163,
0.11288347840309143,
-0.0014024412957951427,
0.00950414128601551,
0.0599374882876873,
-0.007858739234507084,
0.06724618375301361,
0.04017489403486252,
-0.0189504474401474,
-0.04196987301111221,
-0.05580701306462288,
-0.015645012259483337,
0.07842925935983658,
-0.0349... |
<p>I recently stumbled upon this interesting image of a wasp, floating on water:</p>
<p><img src="http://i.stack.imgur.com/Sa7bm.jpg" alt="enter image description here"></p>
<p>Assuming this isn't photoshopped, I have a couple of questions:</p>
<ol>
<li><p>Why do you see its image like that (what's the physical expl... | g19284 | [
0.06641029566526413,
0.002016895217821002,
-0.005579014774411917,
-0.01754142716526985,
0.0742485374212265,
0.06650543212890625,
0.043584808707237244,
0.00672894436866045,
-0.01083818543702364,
-0.032611072063446045,
-0.004012355115264654,
0.0017933403141796589,
0.09397269785404205,
0.0298... |
<p>The project at <a href="http://www.torresolenergy.com/EPORTAL_DOCS/GENERAL/SENERV2/DOC-cw4cb709fe34477/GEMASOLARPLANT.pdf" rel="nofollow">Gemasolar</a> uses molten salt to store heat. This heat is then used with water to drive steam turbines. Over time does this kind of repeated heat/cold cycle make the molten salt ... | g19285 | [
0.0055888984352350235,
-0.004461465869098902,
0.0016671284101903439,
-0.0480523519217968,
-0.049209967255592346,
-0.037442587316036224,
-0.004851526115089655,
0.008554276078939438,
-0.014285768382251263,
-0.0025159085635095835,
-0.025661634281277657,
0.060056328773498535,
0.07446351647377014... |
<p>Could someone please give me a good definition of the following electric terms? Despite what searching I have done, I have not come across a definition that I have found clear for me to understand:</p>
<ul>
<li>Free electron</li>
<li>Mobile charge</li>
</ul> | g19286 | [
0.035170961171388626,
0.04907330870628357,
-0.00135452498216182,
-0.030967367812991142,
0.06562989950180054,
0.027208611369132996,
-0.058049753308296204,
-0.014575589448213577,
0.00564013235270977,
0.031021472066640854,
-0.06254985183477402,
0.03015473484992981,
0.002952099312096834,
0.002... |
<p>What is the relation between control rods surface exposed into a nuclear reactor and neutron energy? Is it linear? I mean, how do neutron absorbing rate change with the progressive immersion of control rods into the core?</p> | g19287 | [
0.037729497998952866,
0.015698658302426338,
0.006610586773604155,
-0.02183164283633232,
0.00009061829769052565,
0.0034076787997037172,
0.059576526284217834,
0.07406366616487503,
-0.007102629169821739,
-0.010794582776725292,
-0.010158061049878597,
0.020403442904353142,
-0.013019143603742123,
... |
<p>Is it known whether spiral galaxies typically (or exclusively?) rotate with the arms trailing or facing?</p>
<p>Intuitively it feels weird to think of the arms as facing the direction of rotation, but that's silly, of course -- it seems to have its origin in an instinctive assumption that some sort of friction with... | g19288 | [
0.006339444778859615,
-0.011968005448579788,
0.0034920605830848217,
-0.03604426980018616,
0.0681615024805069,
-0.03922111168503761,
0.058889299631118774,
-0.027893010526895523,
0.00556981610134244,
-0.049173079431056976,
-0.008503388613462448,
0.0392923578619957,
0.007276964373886585,
0.00... |
<p>Given that <a href="http://en.wikipedia.org/wiki/Antimatter">antimatter</a> galaxies are theoretically possible,
how would they be distinguishable from regular matter galaxies?</p>
<p>That is, antimatter is equal in <a href="http://en.wikipedia.org/wiki/Atomic_weight">atomic weight</a> and all properties, except fo... | g321 | [
-0.021746816113591194,
-0.027145205065608025,
0.011159928515553474,
-0.020236847922205925,
0.05646704509854317,
0.010678345337510109,
-0.04859276860952377,
0.0030902791768312454,
-0.01053939200937748,
-0.035028062760829926,
0.049195796251297,
0.022547122091054916,
0.0276812594383955,
0.029... |
<p>Does there exist a <a href="http://cleardarksky.com/c/SanFranCAkey.html?1" rel="nofollow">Clear Sky Chart</a> with the following enhancements?:</p>
<p>1 - Actual Cloud Cover (Offered Visually and not just Colors with a Legend, Over Time/Past & Predictive)</p>
<p>2 - Simulate/Predict Cloud Cover taking into acc... | g19289 | [
-0.01996222697198391,
-0.006044205743819475,
-0.0003800352569669485,
-0.05487983301281929,
-0.07391157746315002,
0.012589100748300552,
0.007885640487074852,
-0.04146815091371536,
0.01525108702480793,
0.01857747882604599,
0.09635955095291138,
0.019963376224040985,
0.10749950259923935,
0.023... |
<p>The Earth's axis is 23.5 degrees away from othogonality to the ecliptic, and it takes about 26 000 years for it to precess fully. I have neither an intuitive sense nor the formula for precession frequency in front of me for how the latter depends on the former (and other things). So...</p>
<p>A. What is the general... | g19290 | [
0.018506979569792747,
0.06362355500459671,
-0.01106459740549326,
-0.014385097660124302,
0.01126071810722351,
-0.021156346425414085,
0.1149895116686821,
-0.04996812716126442,
-0.015617684461176395,
-0.02777622826397419,
-0.01859620213508606,
-0.0026868898421525955,
0.05607067793607712,
-0.0... |
<p>Are meteorites <a href="http://en.wikipedia.org/wiki/Igneous_rock" rel="nofollow">igneous</a>, <a href="http://en.wikipedia.org/wiki/Sedimentary_rock" rel="nofollow">sedimentary</a> or <a href="http://en.wikipedia.org/wiki/Metamorphic_rock" rel="nofollow">metamorphic</a> rocks?</p>
<p>Or do we need a new method of ... | g19291 | [
0.04725964367389679,
-0.007756608538329601,
-0.0052515375427901745,
-0.07688534259796143,
0.025987200438976288,
-0.05854235962033272,
-0.03718272224068642,
-0.026975814253091812,
-0.01420559547841549,
-0.014877021312713623,
0.02005215920507908,
-0.016901763156056404,
0.06539951264858246,
-... |
<p>Very curious as to where this angle comes from? It describes the peak of radiation for almost all radiation regimes, but I am having a difficult time seeing where it comes from.</p>
<p>Also, the physical significance of it.</p>
<p>Thanks in advance!</p> | g19292 | [
0.06776886433362961,
0.0028098267503082752,
-0.011981484480202198,
0.008293503895401955,
0.04972578212618828,
-0.02083037979900837,
0.049072396010160446,
0.046094849705696106,
0.01609635539352894,
0.03873297944664955,
0.027905665338039398,
0.040519632399082184,
0.06537247449159622,
-0.0352... |
<p>I understand the concept, but I'm having a hard time applying the consequences of conservation (energy/momentum). For example:</p>
<p>A proton with kinetic energy 437 MeV hits a proton at rest elastically and as result both protons rebound with equal energies. What is the included angle between them?</p>
<p>Attemp... | g19293 | [
0.07772251963615417,
-0.012465282343327999,
-0.0046819341368973255,
-0.004643840249627829,
0.04986542463302612,
0.0055544269271194935,
0.01843975856900215,
0.011226932518184185,
0.003748093033209443,
0.0020675286650657654,
0.007288000546395779,
0.0021216771565377712,
-0.009922106750309467,
... |
<p>My question is are there any systems in physics that can only be formulated as an integral equation? Or do all integral equations have an equivalent differential equation? </p> | g19294 | [
0.04017636924982071,
0.047959182411432266,
-0.009132773615419865,
-0.00024565489729866385,
0.025000697001814842,
-0.01164967194199562,
-0.04064900800585747,
0.0035973081830888987,
0.0008316666353493929,
-0.03026178851723671,
-0.008316712453961372,
-0.028733406215906143,
-0.028035491704940796... |
<p><a href="http://en.wikipedia.org/wiki/Electromagnetic_induction" rel="nofollow">Faraday's Law</a> seems more like an observation than an explanation. Sure, a changing magnetic current causes emf, but <em>why</em>?</p>
<p>How does a changing magnetic field cause electrons to move in the direction of a wire? Assume t... | g19295 | [
0.026846518740057945,
0.05196500942111015,
-0.03141339123249054,
0.013010609894990921,
0.08488655835390091,
0.035385534167289734,
0.06685323268175125,
0.027686135843396187,
-0.05279640108346939,
-0.02608276903629303,
-0.03869682550430298,
0.022251730784773827,
0.040127210319042206,
0.03082... |
<p>I attribute it to the fact that for an ultrarelativistic charge the field is contracted and essentially there are only fields in the transverse direction and nothing longitudinally (wrt the charges velocity). Any thoughts?</p> | g19296 | [
0.06838589161634445,
0.04772944375872612,
-0.025690602138638496,
0.0170582327991724,
0.11220355331897736,
0.05538056790828705,
0.050091683864593506,
-0.004485036712139845,
0.005356097128242254,
-0.04786993935704231,
-0.020867476239800453,
-0.015979867428541183,
-0.021630816161632538,
-0.01... |
<p>I have some ponderings about the double slit experiment(s) and mainly their interpretations. Some of my questions may exhibit insufficient scholarship so please bear along, or please point out the fallacies wherever they are instead.</p>
<ol>
<li><p>Why is it commonly said that it is impossible to know in advance w... | g19297 | [
-0.0022350489161908627,
-0.0009272510069422424,
0.001338335801847279,
-0.009482012130320072,
0.04988967999815941,
-0.005436540115624666,
0.054179247468709946,
0.0660734474658966,
0.007218347396701574,
-0.04178665578365326,
0.020665941759943962,
0.044794727116823196,
0.038619015365839005,
0... |
<p>It is sometimes said that the universe is homogeneous and <a href="http://en.wikipedia.org/wiki/Isotropy" rel="nofollow">isotropic</a>. What is meant by each of these descriptions? Are they mutually exclusive, or does one require the other? And what implications rise because of this?</p> | g19298 | [
-0.016779238358139992,
0.062126245349645615,
-0.03043864294886589,
-0.031165380030870438,
0.045294973999261856,
0.03125610202550888,
0.008111463859677315,
-0.012105041183531284,
0.0004749301297124475,
0.0052914805710315704,
-0.00887331459671259,
-0.03248520568013191,
0.028629245236516,
0.0... |
<ol>
<li>I've heard most of galaxies are spiral or ellipsoid shaped. Is it true? </li>
<li>If true, then why they form in such shapes? </li>
<li>How did arms of the spiral galaxies form?</li>
</ol> | g19299 | [
0.05160817503929138,
-0.0035981214605271816,
-0.0013342102756723762,
-0.024253051728010178,
0.0977831557393074,
0.01607554964721203,
-0.03061089664697647,
-0.044390901923179626,
0.0359378382563591,
-0.03668041527271271,
-0.025391796603798866,
0.012453182600438595,
0.051916684955358505,
0.0... |
<p>AFAIK all the celestial objects have a spin motion around its axis. What is the reason for this? If it must rotate by some theory, what decides it's direction and speed of rotation?</p>
<p>Is there any object that does not rotate about its axis?</p> | g231 | [
0.03508855029940605,
0.04493338614702225,
0.016527283936738968,
0.03689410537481308,
0.055417340248823166,
-0.009222127497196198,
0.04613078385591507,
0.001542208599857986,
-0.02524263970553875,
-0.04531661048531532,
-0.006317178253084421,
0.003045132616534829,
0.012689489871263504,
-0.026... |
<p>Can we ever have a black colored (the color of the light and not the body's color) torch that darken (or dis-illuminates) everything? While compared to a normal torch it would function in an opposite manner. If not now, will it be possible to create this in the near future?</p> | g781 | [
-0.004870854318141937,
0.0017969541950151324,
0.02907148189842701,
-0.01899695210158825,
0.0022356354165822268,
-0.02773846685886383,
-0.04367286339402199,
0.07160357385873795,
-0.013994446024298668,
-0.05181891471147537,
0.05197501555085182,
0.05268983170390129,
0.02540956251323223,
-0.02... |
<p>I was wondering if all the stars that we can see with the unaided eye as distinct point sources are from our own galaxy?</p>
<p>In other words, can we see stars from the <a href="http://en.wikipedia.org/wiki/Andromeda_Galaxy">Andromeda Galaxy</a> or other galaxies without telescopes?</p> | g19300 | [
-0.03705558925867081,
0.012740164063870907,
0.009672343730926514,
-0.0312369242310524,
-0.024744991213083267,
-0.013384769670665264,
-0.045012906193733215,
0.01864735037088394,
0.05167703703045845,
-0.014857370406389236,
0.06569801270961761,
0.054572828114032745,
0.025960763916373253,
-0.0... |
<p>One thing is certain: Mars can be further from Jupiter than Earth can ever be (when they're on opposite sides of the solar system), but Mars can also be closer from Jupiter than Earth can ever be.</p>
<p>And does this carry any physical implications?</p> | g19301 | [
0.004246849566698074,
0.0485256165266037,
0.03649730607867241,
-0.004264194983989,
0.029459943994879723,
0.06995628029108047,
-0.01632673852145672,
-0.03252021595835686,
-0.045406777411699295,
-0.07522720098495483,
0.07875364273786545,
-0.02708606608211994,
0.011065949685871601,
-0.0166847... |
<p>In Jaume Gomis's <a href="http://www.perimeterscholars.org/327.html#top" rel="nofollow">lecture 5</a> on CFT at Perimeter Institute, he says (at 27:40 minute mark) that the beta function, <em>classically</em>, of the $m^2$ parameter in massive $\lambda \phi^4$ theory is</p>
<p>$$\beta(m^2) = -2m^2\,.$$</p>
<p>The ... | g19302 | [
0.04618017375469208,
-0.018228333443403244,
-0.01036269124597311,
-0.06710813194513321,
0.08317486941814423,
0.013104286044836044,
0.03364470228552818,
-0.008189620450139046,
-0.09642387181520462,
0.007154734339565039,
-0.07203252613544464,
0.05613647401332855,
0.02046547830104828,
0.04373... |
<p>I would like to view some spiral galaxy. However, I would prefer not to spend lots of $$$. What are the minimum specs a telescope must have to resolve detail in a spiral galaxy?</p> | g19303 | [
-0.021024229004979134,
0.03698572888970375,
-0.021566713228821754,
-0.02284090220928192,
0.02099408023059368,
-0.07548503577709198,
-0.030769729986786842,
-0.0386664979159832,
0.02679491974413395,
-0.04678192362189293,
0.02550552412867546,
0.065489262342453,
-0.02307637222111225,
-0.019133... |
<p>So let's say for example I have an object with 5kg of mass.</p>
<p>It explodes with a force of 500N.</p>
<p>The object fragments into four fragments: a 0.5kg, a 1kg, a 1.5kg and a 2kg object.</p>
<p><strong>What force does each of those fragments have (and thus what acceleration)?</strong></p>
<p>My assumption i... | g19304 | [
0.062233537435531616,
0.014582588337361813,
0.006154611706733704,
0.021967513486742973,
0.023244818672537804,
0.00016485531523358077,
0.0038253620732575655,
0.022873327136039734,
-0.02091316506266594,
-0.04891260340809822,
-0.0015899057034403086,
-0.015767818316817284,
-0.00576752470806241,
... |
<p>The question is 2.10 taken from: Introductory Chemical Engineering Thermodynamics, 2E by Elliot,Lira</p>
<blockquote>
<p>Air at 30ºC and 2MPa flows ata steady state in a horizontal pipeline with a velocity of 25m/s. It passes through a throttle valve where the pressure is reduced to 0.3MPa. The pipe is the same d... | g19305 | [
0.06953407824039459,
-0.02739630453288555,
-0.014524074271321297,
0.010126360692083836,
-0.07411982864141464,
-0.02846122719347477,
0.07483062148094177,
-0.001283756224438548,
-0.10066825896501541,
-0.013763018883764744,
-0.02809232659637928,
0.006548002827912569,
-0.020103923976421356,
0.... |
<p>I used until now only <a href="http://www.stellarium.org"><code>stellarium.org</code></a> and I'm curious if there is any other software that is better than stellarium. By better, I mean:</p>
<ul>
<li>doesn't have high system requirements</li>
<li>requires very little power from the battery when running(as the norm... | g19306 | [
0.023528680205345154,
-0.008962706662714481,
-0.00537644000723958,
-0.03093917854130268,
-0.03005080856382847,
-0.05155270919203758,
-0.03829960897564888,
0.0006470547523349524,
-0.01567087508738041,
-0.021877899765968323,
0.07118504494428635,
0.03363098204135895,
0.050893668085336685,
-0.... |
<p>I've heard people say that high amperage or high voltage is dangerous to humans-aren't they both? And what are the advantages to high amperage versus high voltage? And how do you generate one or the other? They are related via Ohm's Law, so I always run into problems trying to think of how to generate one, because I... | g589 | [
0.05920255184173584,
0.05473417416214943,
0.001526675303466618,
0.044217243790626526,
0.05750815197825432,
-0.019901642575860023,
-0.020600156858563423,
0.026480266824364662,
-0.026877552270889282,
0.012689951807260513,
-0.036863647401332855,
0.03669898211956024,
-0.038860633969306946,
0.0... |
<p>I know the field difference across a charged sheet-but what's the potential on a charged sheet? Is it just asymptotic?
If we had a thin cylindrical sheet would it be the same? Zero field inside the cylinder, and jump to infinity on the sheet, and q/r outside? </p> | g19307 | [
0.05279591307044029,
0.034159768372774124,
-0.011201943270862103,
-0.0019339699065312743,
0.07735668122768402,
0.015091129578649998,
0.010816534049808979,
-0.020605362951755524,
-0.0736035630106926,
-0.028050091117620468,
-0.046027373522520065,
0.014025759883224964,
0.0002659245510585606,
... |
<p>It is said every electron is negatively charged and so they repel each other but if electrons are tiny magnets(which are responsible for atomic attraction and how solid magnet works) does it mean opposite electron poles attract each other?</p> | g19308 | [
0.037925492972135544,
0.002331198425963521,
0.0076543851755559444,
-0.030335968360304832,
0.05266308784484863,
0.0748758539557457,
-0.016362914815545082,
0.018237514421343803,
-0.015085128135979176,
0.005810590460896492,
-0.06187419965863228,
0.01775224506855011,
-0.016308212652802467,
-0.... |
<p>Or is the kinetic energy of the electrons not counted towards the thermal energy? (In other words only the energy of the lattice structure is counted)</p> | g19309 | [
0.07841181010007858,
0.01973825879395008,
0.0038725705817341805,
0.0011749868281185627,
0.027537953108549118,
-0.015426256693899632,
-0.024692552164196968,
0.08577525615692139,
-0.007942085154354572,
0.0038517655339092016,
-0.0016440779436379671,
0.04818281531333923,
-0.012697440572082996,
... |
<p>The <a href="http://en.wikipedia.org/wiki/Geodesic_curvature" rel="nofollow">geodesic curvature</a> is given by</p>
<p>$$k=\pm t^a n_b\nabla_a t^b,$$</p>
<p>where $t^a$ is a unit vector tangent to the boundary of the string worldsheet and $n_a$ is an outward vector orthogonal to $t^a$. I don't understand why under... | g19310 | [
0.06261712312698364,
0.00547698512673378,
-0.024612488225102425,
-0.014813781715929508,
0.044177860021591187,
0.01259167306125164,
0.07077319920063019,
0.01692792773246765,
-0.04536759480834007,
-0.007818900048732758,
0.03428724408149719,
0.0000357294047717005,
0.10965132713317871,
-0.0073... |
<p>When pouring a liquid into a glass some streams have a wavy shape, like the one in the following photo:</p>
<p><img src="http://i.stack.imgur.com/SpGs5.jpg" alt="example"></p>
<p>(Couldn't find a better picture, sorry.)</p>
<p>What causes the stream to be of such a shape?</p> | g19311 | [
0.027227148413658142,
0.01947038620710373,
0.007922481745481491,
-0.0031920825131237507,
0.049687691032886505,
0.010572521016001701,
0.04892392084002495,
0.03320213407278061,
-0.009718125686049461,
-0.025940582156181335,
-0.012050132267177105,
0.06646062433719635,
0.030614251270890236,
0.0... |
<p>The center of the gaussian beam in glass has a beam power of 1 mW and a beam radius of 20 μm (micro meter). The wavelength of the light $\lambda_0$ is 1550 nm. </p>
<p>How can I find the electric field E and magnetic field H?</p> | g19312 | [
0.02277262881398201,
-0.013491949997842312,
-0.028470834717154503,
-0.039225418120622635,
0.026520241051912308,
-0.037151169031858444,
-0.03760901838541031,
0.0369870699942112,
0.02725137583911419,
0.014457805082201958,
-0.014820248819887638,
0.04763782024383545,
-0.031221315264701843,
0.0... |
<p>In superconductivity, when we solve the ginzburg-landau equations relative to a 2 dimensional plane immersed in a magnetic field, we find that a periodic lattice of vortices is a solution. When we look at the higher critical magnetic field, we suppose that the plane is covered with vortices each having inside a flux... | g19313 | [
0.003362349234521389,
0.09009057283401489,
-0.026791539043188095,
0.03140786290168762,
0.030360333621501923,
-0.029328733682632446,
0.04561087116599083,
0.014068251475691795,
0.00742252916097641,
-0.007829799316823483,
-0.07675586640834808,
0.010297760367393494,
-0.02957587130367756,
0.045... |
<p>I'm having difficulties solving boundary conditions for an infinitely thin conducting layer in a presence of an alternating field.</p>
<p>I use the Maxwell equations:<br>
$\nabla \cdot \mathbf B = 0$<br>
$\nabla \cdot \mathbf D = \rho$<br>
$\nabla \times \mathbf E = i \omega \mathbf B$<br>
$\nabla \times \mathbf H ... | g19314 | [
0.06501324474811554,
-0.027870312333106995,
0.00035493922769092023,
-0.021912580356001854,
0.058697961270809174,
0.02567574940621853,
0.042384516447782516,
-0.0012487178901210427,
-0.042705196887254715,
0.032745860517024994,
-0.024390026926994324,
0.03139549121260643,
-0.08591700345277786,
... |
<p>I'd like to ask a question if I may about the relativity. When travelling at the speed of light(which is impossible for particles with masses) or very close to it, would it be me, myself, seeing my watch run slower, or would it be an observer seeing it? </p>
<p>Also, according to Twin Paradox, the twin who stays in... | g590 | [
0.030880432575941086,
0.06725122034549713,
0.009439683519303799,
-0.004980927798897028,
0.019632812589406967,
0.03276975825428963,
0.07263387739658356,
-0.009035224094986916,
-0.0070990691892802715,
-0.022100361064076424,
0.029191456735134125,
0.01786208339035511,
0.08029228448867798,
-0.0... |
<p>I'm having trouble putting the pieces together. In SM, neutral kaon oscillation is heavily constrained. This means, roughly, that the squark mass matrices have to be diagonal. And this is called universality of soft parameters.</p>
<p>What exactly is universality and why do we have universality in this situation? F... | g19315 | [
-0.044025469571352005,
0.09462916851043701,
-0.006131500005722046,
0.012194166891276836,
0.002548239892348647,
0.024670308455824852,
-0.006733637768775225,
0.0500643253326416,
0.007681998889893293,
0.016447506844997406,
0.006591756362468004,
0.005044274963438511,
0.04550519958138466,
0.053... |
<p>The Harvard-Smithsonian Centre for Astrophysics held a press conference today to announce a major discovery relating to gravitational waves. What was their announcement, and what are the implications?</p>
<p>Would this discovery be confirmation of gravitational waves as predicted by general relativity (even though ... | g19316 | [
0.025947974994778633,
0.0710919052362442,
0.0030311564914882183,
-0.03309159353375435,
0.044184405356645584,
0.017060749232769012,
0.01816791296005249,
-0.017451191321015358,
-0.0364757739007473,
-0.03860984742641449,
0.01535069290548563,
0.014991691336035728,
0.025453435257077217,
0.04208... |
<p>Is it possible to create a neutron out of pure energy, i.e. not by bringing a bunch of already-existing quarks together? (A quick calculation using E = mc2 shows the energy required would be about 1.5 e-10 J.)</p>
<p>Would an equivalent antiparticle always need to be created?</p> | g19317 | [
0.018600640818476677,
0.03505036607384682,
-0.005583312828093767,
-0.03609147667884827,
-0.025388078764081,
-0.010562680661678314,
-0.035002127289772034,
0.06708304584026337,
-0.04306033253669739,
-0.05331077799201012,
-0.010206387378275394,
0.018314016982913017,
-0.018094955012202263,
-0.... |
<p>If the space-time metric is expanding with the expansion of the universe, if I could travel back in time, would I be less dense than the matter in that previous era? </p> | g56 | [
0.0025484308134764433,
0.08048372715711594,
-0.0068962592631578445,
-0.0006791566265746951,
-0.01905413530766964,
0.04890993982553482,
0.014416403137147427,
-0.030694402754306793,
-0.02777271717786789,
-0.031964052468538284,
0.048835787922143936,
-0.04083999991416931,
0.021783431991934776,
... |
<p>This is a question regarding the physics behind the observation.</p>
<p>I have guessed the answer to the question, but I may be wrong, so I want to wait for the responses before posting it.</p>
<p>Some major considerations:</p>
<ol>
<li><p>A battery's positive terminal does have a positive potential. ie, a test p... | g19318 | [
0.05110933631658554,
-0.008843096904456615,
-0.015713362023234367,
0.010274781845510006,
0.05966343358159065,
0.044597432017326355,
0.043066736310720444,
0.005593955051153898,
-0.05037350207567215,
0.007947246544063091,
-0.008946473710238934,
0.06080899387598038,
0.00007551884482381865,
0.... |
<p>Sometimes I read here or there that a problem with the electroweak vacuum is that it implies a huge positive cosmological constant. On other side, I also read that AdS spaces are not useful anymore for real world observations because we need to get a small positive cosmological constant at the end of the day.</p>
<... | g19319 | [
-0.02176271565258503,
0.03327689692378044,
-0.0019763074815273285,
-0.023648623377084732,
0.011229462921619415,
0.06923463195562363,
0.015780335292220116,
0.05384032428264618,
-0.0100223608314991,
-0.008382504805922508,
0.04652538150548935,
0.0022105183452367783,
-0.003036974696442485,
0.0... |
<p>I am learning nonlinear sigma model from <strong>Assa Auerbach</strong>'s book "<strong>Interacting Electrons and Quantum Magnetism</strong>" and getting some difficulties in taking continuum limit. I am following chapter 12: The continuum approximation.</p>
<p>Let me formulate the problem first. Consider the Heise... | g19320 | [
-0.0022031350526958704,
0.041345104575157166,
0.0021240334026515484,
-0.018469655886292458,
-0.02335250750184059,
0.03416869044303894,
0.058302801102399826,
0.06638585031032562,
0.010272483341395855,
0.012315884232521057,
-0.04161105304956436,
0.05185391381382942,
-0.042959295213222504,
-0... |
<p>If we consider a system comprising a massless string over a frictionless pulley,then we write the torque equation as $(T_2-T_1)R=I a$ ,where $T_2$ and $T_1$ are tensions on either side of the pulley.</p>
<p>The tangential force acting on the pulley is the friction $F$ between the pulley and the string. How is that ... | g19321 | [
0.02910439856350422,
0.0021390835754573345,
0.01758611761033535,
-0.020592063665390015,
0.004388025961816311,
-0.022393949329853058,
0.023515766486525536,
-0.029864924028515816,
-0.05352454259991646,
0.009068535640835762,
-0.025784924626350403,
-0.030974337831139565,
0.02808930166065693,
0... |
<p>By definition according to the notes I am looking through:</p>
<p>The <strong>partial trace</strong> $\text{Tr}_A:L(H_A \otimes H_B) \rightarrow L(H_B)$ is the unique map that satisfies: $$\text{Tr}(L_B \cdot \text{Tr}_A(R_{AB})) = \text{Tr}((\mathbb{I} \otimes L_B)R_{AB})$$ for all $L_B \in L(H_B)$ and $R_{AB} \in... | g19322 | [
0.026250915601849556,
-0.055492859333753586,
-0.03334459662437439,
0.016390394419431686,
0.06244141608476639,
-0.029098136350512505,
0.024690663442015648,
0.008985656313598156,
0.006239024922251701,
-0.0069349962286651134,
-0.03360689431428909,
-0.025846723467111588,
0.008190358988940716,
... |
<p>Consider the following cases (these are sections):</p>
<p><img src="http://i.stack.imgur.com/cnea1.png" alt="straight line ramp"></p>
<p><img src="http://i.stack.imgur.com/HfNpp.png" alt="curved ramp"></p>
<p>I can find the equation of motion for Case a however I don't know how to deal with Case d. Normally I wou... | g591 | [
0.08832715451717377,
-0.0035673421807587147,
-0.02570519782602787,
0.024420909583568573,
0.053262703120708466,
-0.028553737327456474,
0.06310494989156723,
-0.03239859268069267,
-0.0142356026917696,
-0.004795535933226347,
-0.048961009830236435,
-0.051614727824926376,
0.04631377384066582,
0.... |
<p>I was wondering what dimension can mean in physics?</p>
<p>I know it can mean <a href="http://en.wikipedia.org/wiki/Dimension#In_physics" rel="nofollow">the dimension of the space and time</a>.</p>
<p>But there is <a href="http://en.wikipedia.org/wiki/Dimensional_analysis" rel="nofollow">dimensional analysis</a>. ... | g19323 | [
0.014822205528616905,
0.0269783828407526,
-0.009798427112400532,
-0.0476546473801136,
0.0026375669986009598,
0.0487612783908844,
0.05276290327310562,
0.01936117373406887,
-0.1017308160662651,
-0.020263120532035828,
-0.004919758997857571,
-0.005551986396312714,
0.03774495795369148,
-0.00963... |
<p>We sometimes play a game in my family whereby we trace the energy for a device back to it's source:</p>
<ol>
<li>The Xbox got power from the wall.</li>
<li>The wall got power from the local transformer.</li>
<li>The transformer got power from the coal plant via the power lines.</li>
<li>The coal plant got power fro... | g19324 | [
0.07143336534500122,
0.05818063020706177,
-0.021290697157382965,
-0.057585958391427994,
0.035138290375471115,
-0.05134718120098114,
-0.015277239494025707,
0.03335127234458923,
-0.09232519567012787,
-0.021556779742240906,
0.04760673642158508,
-0.04858613759279251,
0.05009712651371956,
-0.01... |
<p>Does magnetic geometry determine the scaling of a <a href="http://en.wikipedia.org/wiki/Polywell" rel="nofollow">Polywell</a> fusor?</p>
<p>Forgive imprecise terminology here - by "magnetic geometry" I mean the configuration of the magnets, the configuration that creates the "Christmas star" geometry of the electro... | g19325 | [
0.027926983311772346,
0.08657362312078476,
-0.000989939202554524,
-0.020452819764614105,
0.011540487408638,
-0.016580499708652496,
0.023407526314258575,
0.05803690478205681,
-0.022397443652153015,
0.002985595725476742,
-0.04232845455408096,
-0.00048352841986343265,
0.03395700082182884,
0.0... |
<p>At high-energies when the Higgs field won't affect (interact with) particles, when the symmetry breaking won't occur, what would be $\rm W\pm$ or $\rm Z^{0}$ bosons speed if they would then have a $0$ rest mass? What about Fermions?</p> | g19326 | [
0.04768873006105423,
-0.00032032292801886797,
0.02008538320660591,
0.0038754025008529425,
0.04853396117687225,
-0.03963775560259819,
0.04825768992304802,
0.03123939223587513,
-0.007370649371296167,
-0.039400581270456314,
-0.03179448843002319,
0.023720474913716316,
-0.09812497347593307,
0.0... |
<blockquote>
<p>By considering the energy-time uncertainty principle, estimate the range of the weak nuclear interaction at low energies. Compare this range to the size of a typical nucleon (for example, a proton) and therefore explain why the weak nuclear interaction between individual nucleons is 'weak'.</p>
</bloc... | g19327 | [
0.02757091261446476,
0.0738937184214592,
0.0022993511520326138,
-0.012956950813531876,
-0.01619352214038372,
-0.02141467109322548,
-0.0798773467540741,
0.001391061581671238,
-0.048365071415901184,
-0.024808507412672043,
-0.015504319220781326,
0.002794751198962331,
-0.07634209841489792,
0.0... |
<p>There are various ways to numerically find the ground state energy and wavefunction of a many-body Hamiltonian. You can diagonalize the Hamiltonian and pick out the lowest eigenstate, or you use Lancoz.</p>
<p><strong>My proposal is that can I use imaginary time propagation for many-body problems?</strong></p>
<p>... | g19328 | [
0.0055818138644099236,
0.0343262180685997,
-0.0015627085231244564,
-0.04161067679524422,
-0.021114178001880646,
-0.059571221470832825,
0.008772172033786774,
0.07440531998872757,
0.037575483322143555,
0.02656162716448307,
-0.004913883749395609,
-0.007919530384242535,
-0.005181700922548771,
... |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.