question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>I've read <a href="http://cds.cern.ch/record/457317/files/" rel="nofollow">here¹</a> that for a scalar field $\phi$, the square $\vert \phi \vert ^2$ is infinite (which gives an infinite contribution to mass), more precisely:</p>
<blockquote>
<p>the square of the field – a quantity which diverges in QFT as necess... | g18863 | [
0.0445728562772274,
0.026401299983263016,
-0.0073930188082158566,
-0.06522218883037567,
0.09367499500513077,
0.008870216086506844,
0.04364989697933197,
0.02630431205034256,
0.008342611603438854,
-0.05520264431834221,
-0.04861760139465332,
-0.013900510966777802,
0.002299511805176735,
0.0369... |
<p>This question has been inspired by a question asked on Mathoverflow about <a href="http://mathoverflow.net/questions/158145/assessing-effectiveness-of-epsilon-delta-definitions">"effectiveness of (epsilon, delta) definition"</a>. Most mathematicians have a strong opinion about the need of such definitions: They are ... | g18864 | [
-0.004707722458988428,
0.054753370583057404,
0.04066987335681915,
-0.0406498983502388,
0.03680799901485443,
0.004103207495063543,
-0.0027631463017314672,
-0.0014330970589071512,
-0.05344926938414574,
-0.01108170859515667,
0.004487076308578253,
-0.02782599814236164,
0.04429608955979347,
-0.... |
<p>What is meant by normalized projection operator? What is its physical meaning in quantum mechanics? I am pretty confused regarding the physical interpretation of both projection operator and normalized projection operator.</p> | g18865 | [
0.04597148671746254,
0.02305515855550766,
0.01632026955485344,
0.017777590081095695,
0.018151698634028435,
0.04016871377825737,
-0.03554563224315643,
0.04808593913912773,
0.0020582755096256733,
0.011806615628302097,
0.010240948759019375,
-0.020152227953076363,
-0.01950129307806492,
-0.0684... |
<p>I read in these papers(<a href="http://prd.aps.org/abstract/PRD/v75/i9/e094506" rel="nofollow">1</a>,<a href="http://www.sciencedirect.com/science/article/pii/S0550321308002459" rel="nofollow">2</a>) the concept of interface tension. I can't understand its definition. I can hardly imagine there is some tension in a ... | g18866 | [
0.023008661344647408,
-0.0032603221479803324,
-0.03430304676294327,
0.015018350444734097,
0.05489686504006386,
0.022838955745100975,
0.011916013434529305,
-0.009624531492590904,
-0.027603939175605774,
-0.05704716965556145,
-0.05581887811422348,
-0.018409131094813347,
-0.03823758289217949,
... |
<p>Is the atmospheric pressure in a closed container the same as that of the surroundings (1 bar at sea level)? </p>
<p>Consider a tube with both ends open with one end dipped into water (like a pipette in chem lab). Now if we close the other end with a thumb and draw it out of the water, the water level in the tube ... | g18867 | [
0.04657835140824318,
-0.060752760618925095,
-0.0017359007615596056,
-0.0074822502210736275,
0.019418038427829742,
0.11324608325958252,
0.07060567289590836,
-0.03266746923327446,
-0.08873698115348816,
-0.0024732989259064198,
0.010467159561812878,
0.019977491348981857,
0.004062858875840902,
... |
<p>"The diagram below represents a simple circuit composed of 5 identical light bulbs and 2 flashlight batteries. Which bulb (or bulbs) would you expect to be the brightest?</p>
<p><img src="http://i.stack.imgur.com/QT2O4.png" alt="enter image description here"></p>
<p>a) V only </p>
<p>b) V and W only </p>
<p>c) V... | g18868 | [
0.035368748009204865,
-0.022707512602210045,
0.0006902085151523352,
-0.0032579656690359116,
0.03572573885321617,
-0.02543547935783863,
0.048142995685338974,
0.02250942401587963,
-0.00562244700267911,
-0.035053055733442307,
-0.014790653251111507,
0.0876183807849884,
0.00294751999899745,
0.0... |
<p>Can we use entropy change value to define the (perhaps fractional) number of
bits of information that are lost by and, or, xor gates?</p> | g18869 | [
-0.007947186939418316,
-0.009554247371852398,
-0.016840223222970963,
-0.06492201238870621,
-0.006528855301439762,
-0.0855100080370903,
-0.021810799837112427,
0.004305885639041662,
-0.0465175062417984,
0.013394461944699287,
-0.0437600277364254,
0.06554797291755676,
0.048896390944719315,
-0.... |
<p>Why it is said that</p>
<p>$$\frac{dx^2}{dt^2}=\upsilon^2$$</p>
<p>I can only understand the following one:</p>
<p>$$\left (\frac{dx}{dt} \right)^2=\upsilon^2$$</p>
<p><strong>Edit</strong>:</p>
<p>Excerpt from Landau's Mechanics:</p>
<p><img src="http://i.stack.imgur.com/R24Yp.png" alt="enter image descriptio... | g18870 | [
0.006499354261904955,
0.028823819011449814,
-0.0018236861797049642,
-0.03172864392399788,
0.007238322868943214,
0.04550883546471596,
0.03226698189973831,
0.005947227589786053,
-0.012788636609911919,
-0.05860816314816475,
-0.031066514551639557,
0.03089655376970768,
0.03694108501076698,
-0.0... |
<p>In Weinberg's The Theory of Quantum Fields Volume 1, he considers classification one-particle states under inhomogeneous Lorentz group. My question only considers pages 62-64.</p>
<p>He define states as $P^{\mu} |p,\sigma\rangle = p^{\mu} |p,\sigma\rangle $, where $\sigma$ is any other label. Then he shows that, fo... | g18871 | [
-0.009741031564772129,
-0.04503941535949707,
-0.024843445047736168,
-0.04674160107970238,
0.028427140787243843,
0.017575658857822418,
0.020711028948426247,
0.00012006533506792039,
0.0268116258084774,
0.043223049491643906,
-0.054659824818372726,
0.06556724011898041,
-0.009173989295959473,
0... |
<p>One of the key elements of any quantum mechanical system is the spectrum of the Hamiltonian. But what about in quantum field theory? It seems as if nobody ever discusses the spectrum of a system at all -- or have I missed something? Just what role does the spectrum of any given potential play in field theory? To... | g18872 | [
0.013907755725085735,
0.05900115892291069,
0.011806161142885685,
-0.04826200380921364,
0.06145809218287468,
-0.004403521306812763,
-0.0409444160759449,
0.013034841045737267,
0.013212256133556366,
-0.03921224921941757,
0.035597819834947586,
0.019313912838697433,
0.004088356625288725,
0.0274... |
<p>First, when I say infinite focus, I am using the term from photography, perhaps incorrectly. Secondly, I believe am not talking about convergence, but about focus. If I am not mistaken, with stereoscopic displays, only the convergence is manipulated, but if the monitor is 4 feet away, your eyes remain focused at 4... | g18873 | [
0.006915454287081957,
0.04858124256134033,
0.004123648628592491,
-0.012615475803613663,
-0.03130857273936272,
-0.007890818640589714,
0.0074578686617314816,
0.01579640805721283,
0.035770006477832794,
-0.06523787975311279,
-0.009693336673080921,
-0.014608156867325306,
0.023346971720457077,
-... |
<p>On the <a href="http://www.answers.com/topic/planck-length" rel="nofollow">Answers.com</a> page on Planck length, I see two almost-same formulas for the Planck length that differ only by the use of h and hbar. However, the constants are the same, and my calculator gives the correct answer for hbar instead of h, so t... | g18874 | [
0.044344138354063034,
-0.010269023478031158,
0.013113646768033504,
0.007897304370999336,
0.04526229947805405,
0.0058967722579836845,
0.0012835162924602628,
0.040387678891420364,
-0.07100692391395569,
0.04340484365820885,
0.004159767180681229,
0.0024171846453100443,
-0.021719099953770638,
0... |
<p>I am currently reading about QCD in QFT-Peskin&Schroeder. When calculating 1-loop diagrams for QCD and using dimensional regularization, the 3-vertex boson loop, 4-vertex boson loop and ghost loop yield the following divergent terms which contain $\Gamma(1-\frac{d}{2})$ and $\Gamma(2-\frac{d}{2})$.</p>
<p>The c... | g18875 | [
0.028711514547467232,
-0.003613947657868266,
-0.006380092352628708,
-0.06755345314741135,
0.06493108719587326,
0.05447918176651001,
0.02753460966050625,
0.00031394982943311334,
-0.013733204454183578,
-0.004014235455542803,
-0.061141788959503174,
0.0463743656873703,
0.03263235092163086,
-0.... |
<p>Where do the electrons come from when an electric generator is making electricity? Is from the air? Would a generator work in a vacuum? Electrons have mass so where would they be pulled from if there is nothing?</p> | g18876 | [
0.007153164129704237,
0.054784517735242844,
0.00545573839917779,
-0.011939676478505135,
0.02956474758684635,
0.05740309879183769,
-0.056028638035058975,
0.08917078375816345,
-0.07519930601119995,
0.002611147705465555,
-0.02705177664756775,
0.005172026343643665,
-0.00010148382716579363,
0.0... |
<p>What is the difference between <a href="http://en.wikipedia.org/wiki/Background_independence" rel="nofollow">background independence</a>, which loop quantum gravity formalism claims to have, and <a href="http://en.wikipedia.org/wiki/General_covariance" rel="nofollow">diffeomorphism invariance</a>?</p> | g18877 | [
0.029900796711444855,
0.042815517634153366,
-0.016550997272133827,
-0.02824530005455017,
0.010738418437540531,
0.05091552436351776,
0.07375269383192062,
0.00025912359706126153,
-0.011223183013498783,
-0.0014322096249088645,
0.009256677702069283,
-0.002955235308036208,
0.0073532769456505775,
... |
<p><a href="http://ltl.tkk.fi/research/theory/helium.html" rel="nofollow">Helium-3's Phase diagram</a> shows that at the right temperature and pressure combination, the solid region dips <em>downward</em> as temperature increases. That means that you can <em>heat it up and it will freeze</em>. What is going on? </p> | g18878 | [
0.03324294462800026,
0.03372633084654808,
0.0036951324436813593,
0.0008708282257430255,
0.053294774144887924,
0.10945206135511398,
-0.02866879291832447,
0.054195255041122437,
-0.05980938300490379,
-0.017690066248178482,
-0.03656569868326187,
0.0192724596709013,
-0.0070418016985058784,
-0.0... |
<p>I would like to know whether electric and magnetic fields interact with air pressure. Do changes in magnitude or direction of such fields increase or decrease the air pressure in a given volume of air? Does it Does it affect the air flow? For example, could it change the flow from laminar to turbulent? </p> | g18879 | [
0.0325491838157177,
0.024421848356723785,
0.012544814497232437,
0.012552589178085327,
0.055822376161813736,
0.031741783022880554,
-0.008369061164557934,
-0.010800442658364773,
0.0029188874177634716,
0.018690578639507294,
-0.027722587808966637,
-0.000133230714709498,
-0.0252425204962492,
0.... |
<p>The textbook defines a tensor to be an element in $(T^*)^k×T^l→R$. It then expresses tensors as arrays of components with respect to a certain basis, and defines tensor contraction using summation convention. My question is: Can we define tensor contraction without referring to basis, components, and summation, but... | g18880 | [
-0.01662866212427616,
-0.0017658935394138098,
0.007145120296627283,
-0.024145519360899925,
-0.018813706934452057,
-0.05196738243103027,
0.034698888659477234,
0.04270274192094803,
-0.012965516187250614,
0.01818515546619892,
-0.04687747731804848,
-0.03516818583011627,
0.08457855880260468,
-0... |
<p>I have heard that <a href="http://physics.stackexchange.com/a/2168/57967">time-travel <em>is</em> possible...<em>relative to some observer</em></a>.</p>
<p>So, as I understand it, the following example would be accurate:</p>
<p>There are two twins- TwinA and TwinB. Both have very accurate clocks, that are exactly ... | g249 | [
0.0294662993401289,
0.05077614262700081,
-0.004064461681991816,
0.0047898185439407825,
0.008296355605125427,
0.008502083830535412,
0.035580240190029144,
0.004382083658128977,
-0.06409850716590881,
0.030242688953876495,
0.007895706221461296,
0.00688064144924283,
0.076179638504982,
-0.025658... |
<p>Consider the following situation:
<img src="http://i.stack.imgur.com/pH3N4.jpg" alt="enter image description here"></p>
<p>This is taken from an example from my book with a solution.</p>
<p>The box weight is $W$ and the coefficient of friction between the floor and the object is $\mu$.</p>
<p>What is the minimal ... | g18881 | [
0.04144573211669922,
0.02195419743657112,
-0.011529485695064068,
0.002133816247805953,
0.04508679360151291,
0.017248094081878662,
0.06032419949769974,
-0.0037041250616312027,
-0.06360087543725967,
-0.06926893442869186,
-0.033224184066057205,
-0.03199777379631996,
0.0522477962076664,
-0.003... |
<p>Recently I have been studying about properties of Mode-Stirred Reverberation Chamber (MSRC). I have run through some of the research papers about the MSRC, but none of them talks about the meaning of mode. What does the "mode" mean in the term MSRC?</p> | g18882 | [
0.0020248480141162872,
0.012244937941432,
-0.019020408391952515,
-0.027796190232038498,
0.016991935670375824,
0.04532128944993019,
0.03940552473068237,
0.0506444126367569,
0.01430918276309967,
-0.04791528359055519,
-0.06769188493490219,
-0.02823794074356556,
0.04820961132645607,
-0.0043887... |
<p>I have recently learned about the Israel junction conditions in GR (as explained in for example Gravitation by MTW). I then tried to generalize it when including Electromagnetism, ie matching two spacetimes over a junction but when there is some non-zero electromagnetic content in, but I ran into difficulties. Does ... | g18883 | [
0.01817670650780201,
0.027164779603481293,
-0.02199683152139187,
-0.0283029954880476,
0.05312029644846916,
0.035867247730493546,
0.02713753841817379,
0.04639587923884392,
-0.057486604899168015,
-0.03801090270280838,
-0.01383459847420454,
-0.02189665287733078,
0.02657567337155342,
-0.004492... |
<p>Is there a published theory that looks at all matter as occupying no space and only being felt because of its gravitational pull?</p>
<p>We've been taught in school that matter has mass and occupies space. I was just wondering if anyone tried to look at matter as having no physical reality...</p> | g18884 | [
0.03787204995751381,
0.008610007353127003,
0.01112768892198801,
-0.052174463868141174,
0.013783891685307026,
0.07965544611215591,
-0.022938532754778862,
0.010493149049580097,
-0.025516096502542496,
-0.05807282030582428,
0.12349957972764969,
-0.06936600804328918,
0.06318066269159317,
0.0385... |
<p>I am trying to figure out how to parametrize the path of a body under the influence of gravity from another body, but I am stuck.</p>
<p>I have looked at the Wikipedia page on <a href="http://en.wikipedia.org/wiki/Kepler_orbit" rel="nofollow">Kepler orbits</a>, but it is rather hard to follow, and doesn't seem to e... | g18885 | [
0.042005423456430435,
0.0501064695417881,
0.002022871980443597,
0.02782025747001171,
-0.04271143302321434,
0.0043550897389650345,
0.05597537383437157,
-0.014286885969340801,
-0.03310844302177429,
0.008916675113141537,
0.00935687217861414,
0.019393645226955414,
0.015032779425382614,
-0.0387... |
<p>I've a question regarding the Hodge star operator. I'm completely new to the notion of exterior derivatives and wedge products. I had to teach it to myself over the past couple of days, so I hope my question isn't trivial.</p>
<p>I've found the following formulas on the internet, which seem to match the definitions... | g18886 | [
-0.023777900263667107,
0.010985716246068478,
-0.006891917437314987,
-0.03324650228023529,
0.0041643111035227776,
0.013640555553138256,
0.09632266312837601,
-0.024785658344626427,
-0.019192658364772797,
0.024058490991592407,
-0.039453279227018356,
0.040946491062641144,
0.012468493543565273,
... |
<p>I have laser beam path that fires two pulses of light in a gaussian distribution, so the intensity graph over time is two identical gaussians separated by a distance $t_0$. In other words, a gaussian convolved with two $\delta$ functions equidistant from the origin. When I take the Fourier transform of this, I get a... | g18887 | [
0.026095954701304436,
-0.005266052670776844,
-0.010289582423865795,
-0.022879822179675102,
-0.0051271249540150166,
-0.016215477138757706,
-0.0021349769085645676,
0.01904377155005932,
-0.031171927228569984,
-0.039092056453228,
-0.031915657222270966,
0.056023918092250824,
0.037769466638565063,... |
<p>I have an hydrogenic atom, knowing that its ground-state wavefunction has the standard form
$$
\psi = A e^{-\beta r}
$$
with $A = \frac{\beta^3}{\pi}$, I have to find the best value for $\beta$ (using the variational method). After having included the Darwin correction
$$
H_D = D\delta(r)
$$
with $D = \frac{\alph... | g18888 | [
0.0400383397936821,
-0.05051441490650177,
-0.015115504153072834,
0.017150120809674263,
0.08658033609390259,
-0.008922100998461246,
0.006899112369865179,
0.030272280797362328,
-0.04866898059844971,
-0.009050996042788029,
-0.03181177005171776,
0.00033367876312695444,
-0.024414697661995888,
0... |
<p>It seems if I reverse velocities then things begin orbiting backwards, at least in classical mechanics.</p>
<p>From <a href="https://en.wikipedia.org/wiki/Orbital_mechanics#Laws_of_astrodynamics" rel="nofollow">here</a>:</p>
<blockquote>
<p>Every orbit and trajectory outside atmospheres is in principle reversibl... | g18889 | [
0.037105899304151535,
0.07566608488559723,
0.03224843740463257,
0.04398919269442558,
0.06714995950460434,
0.010101912543177605,
0.010150149464607239,
0.03805902600288391,
-0.014382217079401016,
-0.039051834493875504,
0.005982200149446726,
0.08614222705364227,
0.03781672567129135,
-0.016570... |
<p>So I am a teaching assistant for an introductory physics class. One of the problems on this weeks workshops is:</p>
<p>Where is the near point (far point) of an eye for which a contact lens with power of +2.75 (-0.83) diopter is prescribed.</p>
<p>So I know that the power is the inverse of the focal length, so I... | g18890 | [
-0.01717008650302887,
-0.0396169014275074,
0.0007221421110443771,
-0.03357871249318123,
-0.02592061460018158,
-0.015086288563907146,
-0.002684961771592498,
0.012614484876394272,
-0.048986271023750305,
0.035675134509801865,
0.01858607493340969,
0.004314352758228779,
0.07849518209695816,
-0.... |
<p>I have just read curious statement on this website: <a href="http://www.trinitas.ru/rus/doc/0016/001d/00162241.htm" rel="nofollow">http://www.trinitas.ru/rus/doc/0016/001d/00162241.htm</a> (unfortunately this is in Russian, but I will try to translate)</p>
<p>"В заключение можно отметить, что всплески потоков части... | g18891 | [
-0.00792249571532011,
0.03206935152411461,
0.008290000259876251,
0.0027909469790756702,
0.04865431413054466,
0.021147379651665688,
0.020898548886179924,
0.004083987325429916,
0.03129049763083458,
-0.06762722134590149,
-0.022723974660038948,
0.05190899223089218,
0.02274240553379059,
0.01946... |
<p>In designing a switch, I made it such that it "springs" back via two neodymium magnets (one in button repelling one in switch). I've found the magnets are too weak and don't spring back. I've resorted to putting a spring in the prototype for now and it works fine.</p>
<p>I have to produce 1000s of these. It's cheap... | g18892 | [
0.020648490637540817,
0.06696345657110214,
0.007864507846534252,
-0.04203841835260391,
0.0359855592250824,
0.004998571239411831,
0.005255730822682381,
0.049710337072610855,
-0.02536080777645111,
-0.03512735292315483,
-0.08218255639076233,
-0.0035032988525927067,
0.00315500027500093,
-0.027... |
<p><strong>Final edit</strong>: I think I pretty much understand now (touch wood)! But there's one thing I don't get. What's the physical reason for expecting the correlation functions to be independent of the cutoff? I.e. why couldn't we just plump for one "master Lagrangian" at the Planck scale and only do our integr... | g18893 | [
0.03867647796869278,
0.03784388303756714,
0.012156052514910698,
-0.05514342337846756,
0.013372069224715233,
0.06097691133618355,
-0.019114837050437927,
0.03407467529177666,
-0.01108027994632721,
-0.07449845224618912,
-0.00455939257517457,
0.005495540332049131,
0.008498446084558964,
0.00341... |
<p>I need to compute the power factor for two ideal impedances, a capacitor:</p>
<p>$$Z_C=\frac{-j}{\omega C} $$</p>
<p>and a inductor:</p>
<p>$$Z_L=j\omega L $$</p>
<p>I know that the power factor is defined as a term $\cos(\phi)$, but I don't know how to compute it in terms of $Z_C$ and $Z_L$. Moreover I need to ... | g18894 | [
-0.006267668679356575,
-0.0044553703628480434,
-0.00533744040876627,
-0.05993199720978737,
0.03143787756562233,
-0.09144185483455658,
0.012827142141759396,
0.04604443907737732,
-0.04045695438981056,
0.03877240791916847,
-0.0578986294567585,
0.05011473223567009,
0.03480655699968338,
0.00896... |
<p>Please bear with me, as I'm not in the field of physics, this question may seem a bit simple.</p>
<p>This question is concerning stable circular orbits around celestial bodies.</p>
<p>I know the equation relevant to my question is given by the equality of gravitational to centripetal force:</p>
<p>$$G\frac{mM}{r^... | g18895 | [
0.014957373961806297,
0.06102161109447479,
0.005307455081492662,
0.04884931445121765,
0.008362583816051483,
0.07175683230161667,
-0.016802014783024788,
-0.021089831367135048,
-0.07872973382472992,
-0.007247961591929197,
0.011433601379394531,
0.029783952981233597,
-0.018319763243198395,
-0.... |
<p>Lets say we have a particle in a infinite square well which has a wavefunction like this ($A$ is some constant and $d$ is the width of the well):</p>
<p>\begin{align}
A\left[ \sin \left(\frac{2 \pi x}{d}\right) + \frac{1}{3}\sin \left(\frac{3 \pi x}{d}\right)\right]
\end{align}</p>
<p>How do we know from which sta... | g18896 | [
-0.0027107736095786095,
-0.07739460468292236,
-0.03912384808063507,
-0.02952117659151554,
0.03586750850081444,
-0.021808046847581863,
0.044646598398685455,
0.04188106954097748,
0.04474503919482231,
-0.02707923948764801,
-0.05805482715368271,
0.028150921687483788,
0.020555101335048676,
-0.0... |
<p>I was kind of puzzled yesterday when thinking about this.</p>
<ol>
<li>If we observe an object moving away from us with 10m/s we would say the object is moving away from us really slowly</li>
<li>But if we (humans, making an observation) would be the size of a proton, previously mentioned 10m/s would appear enormou... | g18897 | [
0.055847249925136566,
0.0259774811565876,
0.022903023287653923,
-0.035612381994724274,
0.07138384878635406,
0.0024875302333384752,
0.017002563923597336,
0.08156463503837585,
-0.06080510839819908,
-0.037875279784202576,
0.02373354695737362,
0.032738275825977325,
0.04059918597340584,
-0.0362... |
<p><a href="http://en.wikipedia.org/wiki/Planck_constant" rel="nofollow">Planck's Constant</a> is said to be one of the smallest constants used in Physics. Some even say it is one of the imponderables – something that we know exists and is true but cannot be explained yet. I remember reading somewhere that Max Planck s... | g18898 | [
0.03917676955461502,
0.008294133469462395,
0.011999232694506645,
-0.0362689234316349,
0.0006556656444445252,
0.015001565217971802,
0.03504112362861633,
-0.002150332322344184,
-0.07125523686408997,
-0.02063901163637638,
-0.013700379058718681,
-0.01862933300435543,
-0.02722500078380108,
-0.0... |
<p>Is there some motivation for the construction of Ladder operator that compound the recursive halmitonian of the Anderson model for numerical renormalization contained is this <a href="http://journals.aps.org/prb/abstract/10.1103/PhysRevB.21.1003" rel="nofollow">paper</a>?</p> | g18899 | [
0.029804866760969162,
-0.0006949242670089006,
0.0018080740701407194,
-0.02999943681061268,
0.028001567348837852,
-0.0276922769844532,
0.0017932902555912733,
0.04661667346954346,
0.043332044035196304,
0.02078092470765114,
-0.06656217575073242,
0.006131704431027174,
0.007988575845956802,
0.0... |
<p>I wish to calculate the magnetic field due to a charged ring rotating about an axis perpendicular to the plane of the ring and passing through a point on its circumference $(P)$. <strong>I arrive at something unusual</strong>. </p>
<p><img src="http://i.stack.imgur.com/2uxU4.png" alt="Ring"></p>
<blockquote>
<p>... | g18900 | [
0.06729873269796371,
0.04086734354496002,
-0.023839998990297318,
0.011801422573626041,
0.04814963415265083,
0.040906161069869995,
0.051671259105205536,
0.015513845719397068,
-0.041833680123090744,
0.018778406083583832,
-0.021441683173179626,
0.03626350313425064,
0.009476453065872192,
-0.03... |
<p>Some dictionaries define a <a href="http://en.wikipedia.org/wiki/Scalar">scalar</a> as follows:</p>
<blockquote>
<p>A quantity, such as mass, length, or speed, that is completely specified by its magnitude and has no direction. -- <a href="http://www.thefreedictionary.com/scalar">The Free Dictionary</a></p>
</bl... | g18901 | [
0.01995793543756008,
0.030780775472521782,
0.0065943473018705845,
-0.02827378734946251,
0.01886940188705921,
0.005640967283397913,
0.008767335675656796,
0.07802644371986389,
-0.043660156428813934,
-0.013237101025879383,
-0.008533691987395287,
-0.011003388091921806,
0.06578171998262405,
-0.... |
<p>If you are in a moving train or in a bus, what you observe is that the trees which are nearer to you move opposite to the direction of your motion. But the trees which are very far away from you, appear to be moving along with the direction of motion. Why it happens?</p> | g581 | [
-0.008639630861580372,
0.015420272015035152,
-0.003985206596553326,
0.023957373574376106,
0.05628490075469017,
0.034706566482782364,
-0.0036846110597252846,
0.03145839646458626,
-0.018643347546458244,
-0.024783365428447723,
0.007561657577753067,
0.02490774542093277,
0.04737682640552521,
0.... |
<p>The Law:</p>
<ul>
<li>The size of a solid material that can be carried by a (water) stream is proportional to the sixth power of its velocity.</li>
</ul>
<p>I have just discovered that I read this law long time ago (it has a name starting with N or P or something), and I was required to construct a convincing mode... | g18902 | [
0.04506301134824753,
0.06222522258758545,
-0.010034102015197277,
-0.055682308971881866,
-0.00928540900349617,
0.014873790554702282,
-0.0254049189388752,
-0.01724350079894066,
-0.0334927998483181,
-0.0011756892781704664,
0.004778988193720579,
-0.033523403108119965,
0.03137509524822235,
-0.0... |
<p>I don't understand why we are able to see and measure curvature / warping of space at all.</p>
<p>Space as I understand it determines distances between objects, so if space were "compressed" or warped, shouldn't distances be compressed or warped the same way (like crumpling up a sheet of paper) ?</p>
<p>Then, howe... | g18903 | [
0.027303455397486687,
0.033646222203969955,
-0.02323821745812893,
-0.07093545794487,
0.0328667089343071,
-0.025366736575961113,
0.01417066901922226,
0.04280424118041992,
-0.0037963883951306343,
-0.037238821387290955,
0.08596675097942352,
-0.0074531445279717445,
0.07871180772781372,
0.01986... |
<p>In MRI dephasing is characterized by $T_2^*$. </p>
<p>$T_2^*$ is measured by performing a Ramsey experiment and is defined as the 1/e decay time of the measured oscillation. </p>
<p>I have read that when there is a slow spin bath the decay will be a Gaussian but cannot find any good sources describing why. </p>
<... | g18904 | [
0.01820663921535015,
0.0029879994690418243,
0.004506486933678389,
-0.08361847698688507,
0.056656163185834885,
0.033205676823854446,
0.05665958300232887,
0.040250856429338455,
0.023557249456644058,
-0.018116844817996025,
-0.007122068665921688,
0.008871156722307205,
0.0433010496199131,
-0.01... |
<p>I've been looking a lot at <a href="http://en.wikipedia.org/wiki/Closed_timelike_curve" rel="nofollow">Closed Timelike Curves</a>, and how if a theory allows for these curves it doesn't respect causality. I understand that about the curves themselves (Grandfather Paradox), but can't seem to fathom how a theory would... | g18905 | [
0.038929641246795654,
-0.004766521509736776,
0.016572531312704086,
-0.026306821033358574,
0.013149772770702839,
0.0469338521361351,
0.01236746832728386,
-0.013445455580949783,
-0.07729252427816391,
-0.03350542113184929,
0.020335542038083076,
-0.05297698453068733,
0.07101178169250488,
0.032... |
<p>Fresh fruits can be used as batteries for glowing bulbs, but how this is possible? I mean how can electric charges flow through fruits? Do they contain chemicals like cells?</p> | g18906 | [
0.03992963209748268,
0.06353437155485153,
0.006945780012756586,
0.03660744056105614,
0.039505619555711746,
0.007400002796202898,
-0.029109394177794456,
-0.03471517935395241,
-0.009673780761659145,
-0.021550508216023445,
-0.04664086923003197,
0.008566510863602161,
0.04887497425079346,
-0.02... |
<p>Displacement operators $\hat D(x,p), \ \ x,p\in\mathbb{R},$ follow a composition rule
$$D(x,p) D(x',p') = \exp\frac{i(px'-xp')}2 D(x+x',p+p').$$
Because of the extraneous phase factor, the set of all displacements is not a group. I could take a set of all displacements multiplied by all possible phase factors and I ... | g18907 | [
-0.012851919047534466,
0.04616463556885719,
-0.030432112514972687,
-0.029120812192559242,
0.013561793603003025,
0.0073243617080152035,
0.019572876393795013,
-0.00001656872518651653,
0.0014396640472114086,
-0.029340606182813644,
-0.04932110011577606,
0.010574151761829853,
-0.02260356023907661... |
<p>I learned that when a body rotates, its total energy is,</p>
<p>$$energy=\left(\frac12\right)mv^2 + \left(\frac12\right)I\omega^2 $$</p>
<p>However, if an astronomical object is orbiting around the earth, is there any rotational kinetic energy? or is it purely translational?</p> | g18908 | [
0.04989383742213249,
0.0448172353208065,
-0.0021677538752555847,
-0.006603661924600601,
0.02387949265539646,
0.008374341763556004,
0.0008884692215360701,
0.01517290249466896,
-0.03435545787215233,
-0.03501487895846367,
-0.008444305509328842,
0.009570308960974216,
0.0039690639823675156,
-0.... |
<p>Analog radio signals are transmitted using light in the radio area of the spectrum.</p>
<p>If it was transmitted using the visible spectrum instead (using a visible light emitting device instead of a radio antenna, obviously), what would it look like?</p>
<p>Would it look like a solid light, because the vibrations... | g18909 | [
0.010884121060371399,
-0.009080921299755573,
0.02232442796230316,
-0.05158441886305809,
-0.018430273979902267,
-0.06313975900411606,
-0.03641102835536003,
0.013046699576079845,
0.033366527408361435,
-0.019217560067772865,
0.04386230930685997,
0.02305305004119873,
0.0327007919549942,
0.0269... |
<p>So, my company works with electric motors, and my boss wanted me to calculate how much weight could be lifted by a motor rated at 750W.</p>
<p>I know that i can't just calculate the work done by it without any further specification of characteristics, but what i what to know is a couple of formulas that could get m... | g18910 | [
0.00772466417402029,
-0.013426285237073898,
0.013419203460216522,
-0.02666163258254528,
-0.04604287073016167,
-0.059154242277145386,
-0.0024986981879919767,
0.07212162017822266,
-0.07640302926301956,
0.044507384300231934,
-0.028290092945098877,
-0.007546413689851761,
0.02527596615254879,
0... |
<p>The way I see it, in both spontaneous and stimulated emission, one atom being de-excited would result in one photon being produced. So if we excite $10^{23}$ atoms, only $10^{23}$ photons would be produced when they de-excite. How can there be a net output of photons then? How is it that lasers can be sustained for ... | g18911 | [
-0.025189805775880814,
0.08005388081073761,
-0.015793828293681145,
-0.0016063806833699346,
0.008982743136584759,
-0.0490599200129509,
0.03218601644039154,
0.029708314687013626,
0.02581075020134449,
-0.027599332854151726,
-0.06953564286231995,
-0.0005494402139447629,
0.030066385865211487,
0... |
<p>In a vacuum:</p>
<p>On my left I have a rod that is 558000 miles long (3 light seconds). A button is secured to its end which activates a laser beam sent back to me once I've pushed the rod in the direction of the button. On my right I have a laser aimed at a reflector that is 558000 miles away pointing straight ... | g4 | [
0.015579777769744396,
-0.026542887091636658,
0.009781834669411182,
0.015313958749175072,
0.04790167137980461,
0.023781057447195053,
0.008446196094155312,
0.02334263175725937,
0.0053146895952522755,
-0.0029172664508223534,
-0.023644492030143738,
0.09152976423501968,
-0.009340481832623482,
-... |
<p>Typically in an exam or problem set we have a problem that's like this:
Determine the specified property at the indicated state of water. Locate the state on a sketch of the T-v and P-v diagram.</p>
<p>p= 3 bar, T= 240°C. Find v, in $m^3/kg$.</p>
<p>I believe I can figure out $v,u,h$ when it ask to find this infor... | g18912 | [
0.018085390329360962,
0.018424363806843758,
-0.011032451875507832,
-0.06543657928705215,
-0.01683800108730793,
-0.03434784337878227,
-0.0060141547583043575,
0.005933137144893408,
-0.04672151058912277,
0.0024167108349502087,
0.04668702930212021,
0.0044394140131771564,
0.038048066198825836,
... |
<p>Given a certain potential $ a^{x} $ with positive non-zero 'a' are there a discrete spectrum of energy state for the Schrodinger equation </p>
<p>$$ \frac{- \hbar ^{2}}{2m} \frac{d^{2}}{dx^{2}}f(x)+a^{x}f(x)=E_{n}f(x)$$</p>
<p>Is there an example of this potential in physics?</p>
<p>EDIT: what would happen if we ... | g18913 | [
-0.03571103513240814,
0.03409802168607712,
0.016205910593271255,
-0.022748054936528206,
0.03897368907928467,
-0.018036622554063797,
-0.06310959905385971,
0.04004210606217384,
-0.02183941751718521,
-0.036722272634506226,
0.033614713698625565,
-0.05409729480743408,
0.011109252460300922,
0.01... |
<p>I always see lots of information about asteroid impacts, but very little is said about comet impacts. As I see, a long period comet impact is much more dangerous because a) we wouldn't have time to prepare for it, and b) even small bodies would have high kinetic energy, equivalent to large asteroids. </p>
<p>On the... | g18914 | [
0.036571599543094635,
0.04084741696715355,
0.02765577845275402,
-0.04140673205256462,
-0.01772996038198471,
0.05322909727692604,
0.020424114540219307,
-0.06101081147789955,
-0.006033203564584255,
-0.02997414395213127,
0.047645580023527145,
0.03317242115736008,
0.0333675742149353,
-0.051710... |
<p>I read about <a href="http://en.wikipedia.org/wiki/Nonthermal_plasma" rel="nofollow">non-thermal plasma</a>, but I still have some questions: </p>
<ol>
<li><p>The ions and neutral particles are not in thermal equilibrium with the electron, does that mean that the overall temperature is low like in neon signs?</p></... | g18915 | [
0.03324297070503235,
0.03548914194107056,
-0.007655469700694084,
-0.018872085958719254,
0.05237026512622833,
-0.03829324617981911,
-0.07105815410614014,
0.012153781950473785,
-0.007770681753754616,
-0.02056172303855419,
-0.0189913809299469,
0.042638782411813736,
-0.011649616062641144,
-0.0... |
<p>The EMDrive described in patent application GB 2493361 is a simple section of a sphere surrounded by a superconducting cooling system. I have attempted to solve the oscillation modes possible and find spherical Bessel functions for radial directions and Legendre polynomials for "theta". When I apply boundary condi... | g18916 | [
0.02358795516192913,
0.045387160032987595,
-0.02344909869134426,
-0.02360844984650612,
0.048715200275182724,
0.03477838262915611,
0.0823475569486618,
0.025607189163565636,
-0.042117923498153687,
-0.004325146321207285,
-0.02486775629222393,
0.0075368573889136314,
-0.045921579003334045,
0.02... |
<p>I am reading a text that describes the scattering of light by a particle with dielectric constant $\epsilon$</p>
<p>After a bit of maths starting from Maxwell's equations they obtain:</p>
<p>$$\nabla (\nabla \cdot E(r)) - \nabla^2E(r)=\mu_0\omega^2\epsilon(r)\cdot E(r)$$</p>
<p>then say "Fourier transforming with... | g18917 | [
0.006461604963988066,
0.01933084987103939,
-0.036666933447122574,
-0.0693291500210762,
0.0761573389172554,
-0.04564099386334419,
0.04831765592098236,
0.026945170015096664,
-0.03239459916949272,
0.022532427683472633,
-0.016655636951327324,
0.05957231670618057,
0.11800557374954224,
0.0399210... |
<p>I'm trying to learn Maxwell's equations but I got stuck. I couldn't understand the usage of the differential form of the Gauss' law. How can it be applied to questions? For example, let's say there is a plate sizes of 10 cm X 5 cm and has a charge of 1 C. To calculate the electric field on the point <strong><em>a</e... | g18918 | [
0.038266878575086594,
-0.001528451917693019,
-0.005547412671148777,
0.010140147060155869,
0.050545334815979004,
0.0667194202542305,
0.03539564087986946,
0.01712459698319435,
-0.02933209389448166,
-0.02501816675066948,
-0.015693895518779755,
0.006956575904041529,
0.019338566809892654,
-0.01... |
<p><a href="http://en.wikipedia.org/wiki/Shot_peening" rel="nofollow">Shot peening</a> is a process of inducing <a href="http://en.wikipedia.org/wiki/Residual_stress" rel="nofollow"><em>residual compressive stress</em></a> on the surface layer of metal parts. When shooting particles are colliding on the surface of meta... | g18919 | [
0.06344938278198242,
-0.00043790810741484165,
-0.02830449491739273,
-0.006097447592765093,
0.03307529538869858,
0.06608115136623383,
0.02437303401529789,
0.02338186465203762,
-0.027320651337504387,
-0.0422254279255867,
-0.06195121258497238,
-0.025147179141640663,
-0.00749601237475872,
-0.0... |
<p>How much mass is converted to energy when a <a href="http://en.wikipedia.org/wiki/Thermonuclear_weapon" rel="nofollow">hydrogen bomb</a> explodes? I remember an eighth grade chemistry class where, by going through the nuclear processes, my teacher estimated that roughly 2g of matter was converted in a fission bomb... | g18920 | [
0.030510012060403824,
0.022505246102809906,
0.020186567679047585,
-0.013052238151431084,
0.022443225607275963,
-0.008190041407942772,
-0.037964411079883575,
0.10654610395431519,
-0.07312102615833282,
-0.03320048376917839,
-0.03455699607729912,
-0.0062566655687987804,
-0.00547655439004302,
... |
<p><img src="http://i.stack.imgur.com/yIa9K.gif" alt="Animation of relationship between torque and momentum"></p>
<p>If angular momentum (<strong>L</strong>) works like this animation from Wikipedia leads me to believe, why can't we put a large flywheel or several small ones on a chassis, all rotating counter-clockwis... | g18921 | [
0.021149523556232452,
0.050019457936286926,
-0.015095584094524384,
-0.019854990765452385,
0.03209523856639862,
0.011964230798184872,
0.07226311415433884,
0.01256608311086893,
-0.03212915360927582,
-0.04650824889540672,
-0.02992919273674488,
-0.06355338543653488,
0.03869186341762543,
0.0000... |
<p>What is the `physical' meaning of <strong>consistent anomalies</strong> and <strong>covariant anomalies</strong>?</p>
<p>Perhaps a good Reference is:
<a href="http://www.sciencedirect.com/science/article/pii/0550321384903225" rel="nofollow">Consistent and covariant anomalies in gauge and gravitational theories -
W... | g18922 | [
0.05770046263933182,
-0.06936762481927872,
-0.00885681714862585,
0.019203754141926765,
0.044949889183044434,
0.03400583565235138,
0.03593188151717186,
-0.03671794757246971,
-0.0235899630934,
0.036131273955106735,
0.03741629049181938,
0.009991558268666267,
-0.015263895504176617,
-0.00262289... |
<p>A modern flywheel rotor is suspended in a vacuum by magnetic bearings. This means that nothing touches the rotor as it spins. When time comes that we need to recover that stored kinetic energy, how do we recover it?</p>
<p>I imagine a clutch making contact with the rotor, but wouldn't that give quite a jolt, slowin... | g18923 | [
0.09074912965297699,
0.06924005597829819,
-0.003933563828468323,
0.03683319315314293,
-0.00889743585139513,
0.0397709421813488,
0.02961084619164467,
0.03823985159397125,
-0.04984372481703758,
-0.026363931596279144,
-0.01635040156543255,
-0.09067857265472412,
0.011211113072931767,
0.0378161... |
<p>I'm trying to learn on my own a bit of solid physics to tackle semiconductors afterwards. I'm struggling with the Energy versus $k$ diagrams for a free electron which shows that for a single value of $k$ we can have many energies value although that there's only one band (in this example).</p>
<p><a href="http://en... | g18924 | [
-0.006649340037256479,
0.021484341472387314,
-0.002516796812415123,
-0.012720782309770584,
0.001712973928079009,
-0.011255350895226002,
-0.03427501395344734,
0.00883747823536396,
-0.019450245425105095,
-0.0028689054306596518,
0.011028903536498547,
0.07358036190271378,
-0.021239839494228363,
... |
<p>Why there can't be infinitely small existing? </p>
<p>I am not suggesting it can or cannot. I am asking can there be an absolute or reasonable answer to that question. </p> | g18925 | [
0.031736698001623154,
0.06491556018590927,
0.035204432904720306,
-0.03224940225481987,
-0.0014665195485576987,
0.06326058506965637,
-0.022688698023557663,
0.0743618980050087,
-0.05964451655745506,
-0.05411502718925476,
-0.008775273337960243,
-0.013785801827907562,
-0.04780695587396622,
0.0... |
<p>My physics instructor gave us a general problem</p>
<blockquote>
<p>A box is sitting motionless on a rough, horizontal patch of ground. You give it a good kick, so that it slides to the right with an initial speed of 4.5 m/s. The box slows and eventually comes to a stop after traveling 14m. As the box nears the e... | g18926 | [
0.03153292089700699,
0.0865907147526741,
0.007462460082024336,
0.00942816399037838,
0.06186048313975334,
0.013173076324164867,
0.037031855434179306,
0.037061579525470734,
-0.07300852239131927,
-0.0657564103603363,
0.00874203909188509,
-0.029633332043886185,
-0.03834183141589165,
-0.0119875... |
<p>Is opposite statement of <a href="http://en.wikipedia.org/wiki/Free_will_theorem" rel="nofollow">Free Will Theorem</a> right: If elementary particles have a certain amount of free will, then so must we? Because to me elementary particles does have a bit of free will – quantum mechanics guarantees that nobody can pre... | g18927 | [
0.035328757017850876,
0.022809835150837898,
0.012808321975171566,
-0.016999920830130577,
0.011036533862352371,
0.018712038174271584,
-0.009415448643267155,
-0.02591741643846035,
-0.00029433349845930934,
-0.05675121396780014,
0.009702911600470543,
0.008365383371710777,
0.010062356479465961,
... |
<p>The following graph shows the result of a very impressive differential measurement of the gravitational field in Boulder, Colorado, over a period of a couple of days.</p>
<p><img src="http://i.stack.imgur.com/OXbRy.png" alt="graph of g as a function of t"></p>
<p>Floris got it from a description in a book and post... | g18928 | [
0.030210645869374275,
0.0036565407644957304,
-0.010358001105487347,
0.001806424232199788,
0.035460639744997025,
0.06040344014763832,
0.08334708213806152,
-0.03415925055742264,
-0.0264955535531044,
-0.06284189224243164,
0.04109910875558853,
-0.006472135428339243,
0.03945818543434143,
-0.019... |
<p>Figure shows a standard two slit
arrangement with slits S1, S2. P1, P2 are the two
minima points on either side of P.
At P2 on the screen, there is a hole and behind P2
is a second 2- slit arrangement with slits S3, S4
and a second screen behind them. </p>
<p><img src="http://i.stack.imgur.com/ZyPgM.png" alt="enter... | g18929 | [
-0.01195241417735815,
0.005728989373892546,
0.0018745638662949204,
-0.0017238524742424488,
0.00750706298276782,
0.0162783432751894,
0.028630321845412254,
0.005601100157946348,
0.037854816764593124,
-0.05526987835764885,
0.03345070779323578,
0.0281466543674469,
-0.025036318227648735,
0.0207... |
<p>Can any gas be liquidified by lowering the temperature? What happens with gases at absolute zero? Are there gases that remain gases at absolute zero? Do their molecules move at these temperatures? Does the gas acquire a crystallic structure at these temperatures while still remaining gaseous?</p> | g18930 | [
0.03132718801498413,
-0.027421679347753525,
0.01852792501449585,
0.029648134484887123,
0.03185165673494339,
0.0033828113228082657,
-0.04310871288180351,
0.04399346187710762,
-0.02363298274576664,
-0.01641000248491764,
-0.05315786972641945,
-0.013881250284612179,
-0.011358999647200108,
-0.0... |
<p>Higgs boson seems to be the only non-rotating elementary particle (unsure about Planck particle). Does it mean that by studiing Higgs bosons one can find the anisotropy in the physical space (or find a distinguished dimension)?</p> | g18931 | [
0.01100841537117958,
0.027111666277050972,
0.0031736770179122686,
-0.03693735599517822,
0.05182056501507759,
0.02668938599526882,
0.022684743627905846,
-0.011778405867516994,
-0.020148124545812607,
-0.03348685801029205,
-0.008489931933581829,
-0.017330164089798927,
-0.011032361537218094,
-... |
<p>Let's consider rotating charged ring. Theoretically mass of this ring has no limit as rotation speed increases. So what about magnetic moment of the ring? Is it limited by the value of speed of light?</p> | g18932 | [
-0.02917303889989853,
0.06303032487630844,
-0.003234419273212552,
-0.0060311113484203815,
0.0768415629863739,
0.01586439646780491,
0.040462058037519455,
-0.012228197418153286,
-0.036959197372198105,
0.024744056165218353,
0.021798359230160713,
0.002701857825741172,
-0.03503260016441345,
-0.... |
<p>The density of powdered sugar is <a href="http://www.franklinmiller.com/material-bulk-density-highlight.html" rel="nofollow">about 20% lower</a> than that of granulated sugar. There is small composition difference between the two - about 3% cornstarch and 0.5% water in powdered sugar, but that's it.</p>
<p>It seems... | g18933 | [
0.03986252099275589,
0.03399612009525299,
-0.0021544713526964188,
0.01297692209482193,
0.015090273693203926,
-0.03635150194168091,
-0.020320091396570206,
-0.0019399761222302914,
-0.050242818892002106,
-0.008571187034249306,
0.046240027993917465,
-0.03243299201130867,
0.080916628241539,
0.0... |
<p>What percentage of physics PhDs leave physics to become quantitative analysts, work in computer science/information technology or business? Is physics that bad that so many people leave? Was it worth it?</p> | g18934 | [
-0.009926063939929008,
0.046964533627033234,
-0.0032301039900630713,
0.007891625165939331,
0.05859028920531273,
0.01692589372396469,
-0.024528834968805313,
-0.0654577761888504,
0.012826166115701199,
0.028856337070465088,
0.029490137472748756,
0.012240128591656685,
0.010005390271544456,
-0.... |
<p>From the "no hair theorem" we know that black holes have only 3 characteristic external observables, mass, electric charge and angular momentum (except the possible exceptions in the higher dimensional theories). These make them very similar to elementary particles. One question naively comes to mind. Is it possible... | g18935 | [
0.015801548957824707,
0.0015064551262184978,
0.009565049782395363,
-0.049349844455718994,
0.00807536207139492,
0.055889155715703964,
-0.03372739627957344,
0.004496848676353693,
-0.03426125645637512,
0.006811982486397028,
-0.004228292033076286,
0.001355191576294601,
0.007933269254863262,
0.... |
<p>In QED, the field strength dependence is expressed by a field of virtual photons of varying spatial density. I know that we describe gravity as a warp in space-time, but how can one warp space (and time) if there isn't anything there to warp (how does one warp a vacuum)? We have established the lack of an ether, but... | g18936 | [
-0.02302241139113903,
0.03512835502624512,
-0.01544093620032072,
-0.06371960043907166,
0.023621289059519768,
0.04808797687292099,
0.007600890472531319,
0.006127045955508947,
0.028732886537909508,
-0.01156096812337637,
0.03941526263952255,
-0.04310831427574158,
0.05441199615597725,
-0.02225... |
<p>I have the following homework problem: </p>
<blockquote>
<p><em>A line of charge $\lambda$ is located on the z-axis. Determine the
electric flux for a rectangular surface with corners at coordinates:
$(0, R, 0)$, $(w, R, 0)$, $(0,R, L)$, and $(w, R, L)$.</em></p>
</blockquote>
<p>This is what I have come up ... | g18937 | [
0.07577400654554367,
-0.015130403451621532,
-0.009991012513637543,
-0.0383879728615284,
0.06445588916540146,
-0.017239443957805634,
0.03990831598639488,
-0.022491486743092537,
-0.04711214080452919,
0.003652054350823164,
-0.030390359461307526,
0.04276914522051811,
0.005205226130783558,
0.02... |
<p>Hypothetically, should a force feel the same as its measured force at relativistic speeds? Obviously a human body would not survive the force of a rotation at say, 0.6 the speed of light, but it’s easier to imagine the problem using large values. </p>
<p>Now, because time runs slower in the body's frame for every c... | g18938 | [
0.034690748900175095,
-0.004143611993640661,
0.02107437327504158,
-0.01458593737334013,
0.0025674705393612385,
0.002586477668955922,
0.055173709988594055,
0.024678248912096024,
-0.012164076790213585,
0.018904201686382294,
0.01991804502904415,
-0.035453759133815765,
-0.026268402114510536,
0... |
<p>I've heard that regular light bulbs with a filament are better for the eyes. Is the spectrum of one worse than the other? If so, are there any regulations for their use in industrial settings for worker safety?</p> | g18939 | [
0.000034088781831087545,
0.0123904375359416,
0.02081368863582611,
0.016607854515314102,
-0.018126213923096657,
-0.10461357980966568,
-0.031094513833522797,
-0.00762657355517149,
0.04131987690925598,
-0.013840160332620144,
0.061723653227090836,
-0.016078311949968338,
-0.014755401760339737,
... |
<p>Einstein's field equations are:</p>
<p>$R_{ab} - {1 \over 2}g_{ab}\,R + g_{ab} \Lambda = {8 \pi G \over c^4} T_{ab}$</p>
<p>And since the Ricci curvature tensor is "less information" than the Riemann curvature tensor because:</p>
<p>$R_{ab} = R^c{}_{acb}$</p>
<p>and the Riccie curvature scalar is even "less info... | g18940 | [
0.004265494178980589,
0.04825929179787636,
-0.021718667820096016,
0.01981409639120102,
0.057602956891059875,
0.022002380341291428,
0.06073588505387306,
0.014550319872796535,
-0.05592404305934906,
-0.03469415381550789,
-0.036828476935625076,
-0.0024138500448316336,
0.05855436623096466,
-0.0... |
<p>I'm assuming the LHC can create a Higgs and an anti-Higgs boson. If so, would their fields be identical with respect to mass effects? How would LHC detectors distinguish between the two bosons?</p> | g18941 | [
0.042634718120098114,
-0.009983026422560215,
0.023570729419589043,
-0.032133594155311584,
0.06278064846992493,
-0.013841402716934681,
-0.04509115219116211,
0.06853311508893967,
-0.0058891428634524345,
-0.05134076997637749,
-0.0758654773235321,
0.0458475761115551,
-0.013278251513838768,
0.0... |
<p>I am a graduate level student, interested in String theory.</p>
<p>I was reading a paper on "String Theory and Einstein's Dream" published in Current Science, vol. 89, No. 12, p 2045, Dec. 25, 2005. and I came across to know that The Standard model of Quantum physics have failed to explain the interaction of grav... | g18942 | [
-0.001466287998482585,
0.09549228847026825,
0.01164061389863491,
-0.02218327485024929,
0.04785946384072304,
0.07366707175970078,
-0.010631902143359184,
0.02996724285185337,
-0.025653239339590073,
-0.05389394983649254,
-0.0064508914947509766,
-0.060870230197906494,
0.01855461858212948,
-0.0... |
<p>Continuing from my first question titled, S<a href="http://physics.stackexchange.com/questions/10053/simple-quantum-mechanics-question-about-the-free-particle-part1">imple Quantum Mechanics question about the Free particle, (part1)</a></p>
<p>Griffiths goes on and says,</p>
<blockquote>
<p>"A fixed point on the ... | g18943 | [
0.059745438396930695,
0.0051131281070411205,
-0.004377430304884911,
-0.036727480590343475,
0.07606519758701324,
0.01064345147460699,
0.03214284032583237,
0.01877462863922119,
-0.0581279955804348,
-0.021137215197086334,
-0.01601855456829071,
0.0620947889983654,
-0.018365321680903435,
-0.045... |
<p>When you come to a stop normally, the brakes don't pulse when you stop. Since the car can only know its speed by the rotation of the wheels, how can it distinguish between the car is stopped normally and the car wheel's stopped rotating because they locked up?</p> | g18944 | [
0.031897030770778656,
0.023867711424827576,
0.003658825531601906,
0.04681101068854332,
0.06685271859169006,
-0.04053865000605583,
0.11272457242012024,
0.05468202382326126,
-0.024169253185391426,
-0.014338198117911816,
-0.02326524816453457,
-0.03023538552224636,
-0.00628221221268177,
-0.018... |
<p>I've read on NASA's page on neutron star that one teaspoonful of that star would weigh over 20 billion ton on Earth. If it was somehow possible to bring it to earth would it:
A) Burn and disappear during earth atmosphere entry?
B) Assuming we bave 20 billion ton of mass in size of a teaspoon here on earth, would it ... | g18945 | [
0.0061742039397358894,
0.097629614174366,
0.019032716751098633,
-0.053619351238012314,
-0.050034333020448685,
0.060388848185539246,
-0.03707364574074745,
0.023709585890173912,
-0.03480147570371628,
-0.02703719772398472,
-0.04646090045571327,
0.005568485241383314,
0.01856246404349804,
0.004... |
<p>When we are cooling the permanent magnet what property of magnet changes?
normally the superconductivity of magnets occurs at critical temperature(negative degrees).It is having a long life period and it exhibits huge magnetic field.
if we keep the magnets at some temperature which is nearer to critical temperature ... | g18946 | [
0.07115847617387772,
0.007702609524130821,
0.029131345450878143,
0.0016754111275076866,
0.015804840251803398,
0.05080581456422806,
0.023675404489040375,
0.021129202097654343,
-0.01336284726858139,
0.03375682234764099,
-0.0526888333261013,
0.06702034920454025,
-0.01744741201400757,
-0.03516... |
<p>When we pass current to the permanent magnet does its magnetic flux, magnetic property of attraction and repulsion increases? if possible
Is there any other way for increasing the magnetic flux?</p> | g18947 | [
-0.005165914073586464,
0.009773780591785908,
0.024062130600214005,
-0.05844404548406601,
0.020714661106467247,
0.09119222313165665,
0.003764816327020526,
0.018532970920205116,
-0.001975190592929721,
0.00254275044426322,
-0.0010536862537264824,
0.044730160385370255,
-0.0043686674907803535,
... |
<p>Is the missing link of what creates gravity, the velocity that an object rotates or moves through space ? Can a small object with little mass which rotates or moves in enormous speed create a strong gravitational field ?</p> | g18948 | [
0.038841843605041504,
0.066825732588768,
-0.011419707909226418,
0.04434039071202278,
0.06144709512591362,
0.05846147611737251,
0.05089559033513069,
-0.036450959742069244,
-0.04634298384189606,
-0.08312519639730453,
-0.024327265098690987,
-0.05598120391368866,
-0.008226772770285606,
-0.0476... |
<p>Suppose they are held 10 nm apart.</p>
<p>What is the dominant interaction between them?</p>
<p>The magnetic dipole interaction or something else?</p> | g18949 | [
-0.00425363564863801,
0.018307466059923172,
-0.0022771195508539677,
-0.005058536306023598,
0.05123697593808174,
0.009152067825198174,
-0.04434638097882271,
0.006742015015333891,
0.0022265780717134476,
-0.03565593063831329,
-0.014949102886021137,
-0.013650805689394474,
-0.062498435378074646,
... |
<p><s>I realize Quantum Field Theory doesn't include gravity at all. Other than that, does QFT completely describe all electromagnetic and nuclear interactions? In other words, does it describe (at least) everything the classical field theories did (other than gravity)?</s></p>
<p>Do the QFTs of the standard model des... | g18950 | [
0.02177521586418152,
0.02360612526535988,
-0.014858921989798546,
-0.011554274708032608,
0.05513830855488777,
0.011693820357322693,
-0.028400843963027,
-0.015845730900764465,
0.014560596086084843,
-0.06508742272853851,
0.011787224560976028,
-0.03974980488419533,
-0.033118974417448044,
-0.00... |
<p>I know that the energy eigenstates of the 3D quantum harmonic oscillator can be characterized by three quantum numbers: $$ | n_1,n_2,n_3\rangle$$ or, if solved in the spherical coordinate system: $$|N,l,m\rangle$$</p>
<p>The relationship between capital $N$ and the little $n_i$'s is straightforward: $N=n_1+n_2+n_3... | g18951 | [
0.041837967932224274,
-0.019498826935887337,
-0.012681763619184494,
-0.08352392911911011,
0.010110445320606232,
0.018709499388933182,
-0.016393406316637993,
0.03603915497660637,
-0.022000469267368317,
0.0029986619483679533,
-0.02577047236263752,
-0.02171984314918518,
-0.01090965699404478,
... |
<p>I'm following Griffiths' Introduction to Quantum Mechanics, and I see that he's got 2 different expressions for $\Psi(x,t)$. One of them is $$\Psi(x,t)=\psi(x)\exp\left(\frac{-iEt}{\hbar}\right)\tag{2.7}$$. The other is $$\Psi(x,t)=\sum\limits_{n=1}^{\infty} c_n \psi_n(x)\exp\left(\frac{-iE_nt}{\hbar}\right)\tag{2.1... | g18952 | [
0.033591464161872864,
-0.008995023556053638,
-0.0013579472433775663,
-0.05198216065764427,
0.10397972911596298,
-0.010034920647740364,
0.05458363518118858,
-0.012086437083780766,
-0.05724548175930977,
0.018854688853025436,
0.006075352430343628,
-0.022983454167842865,
-0.0006580520421266556,
... |
<p>I read about Fractional Quantum Mechanics and it seemed interesting. But are there any justifications for this concept, such as some connection to reality, or other physical motivations, apart from the pure mathematical insight?</p>
<p>If there are none, why did anyone even bother to invent it?</p> | g18953 | [
0.06012510880827904,
0.028272444382309914,
0.02642779052257538,
-0.02067205309867859,
0.011152861639857292,
0.021951450034976006,
-0.0006919704610481858,
0.0289070513099432,
0.004098685923963785,
-0.10387697070837021,
0.01002517994493246,
-0.04196726530790329,
-0.0012295367196202278,
0.030... |
<p>What is the difference between <a href="http://en.wikipedia.org/wiki/Center_of_mass">center of mass</a> and <a href="http://en.wikipedia.org/wiki/Center_of_mass#Center_of_gravity">center of gravity</a>?</p>
<p>These terms seem to be used interchangeably.</p>
<p>Is there a difference between them for non-moving obj... | g18954 | [
0.032465022057294846,
0.019368266686797142,
-0.004659732338041067,
-0.03538596257567406,
0.06783633679151535,
0.006014465354382992,
0.05543410778045654,
0.008000600151717663,
-0.056514330208301544,
-0.031120985746383667,
0.004736846778541803,
-0.024450473487377167,
0.04192928969860077,
-0.... |
<p>Concerning two identical wires carrying the same current (same direction, speed and magnitude), they will be attracted because of the Ampere force. But when I was in the frame moving with the same speed as the electron in the current, why will there be the same force between each wire (supposing that the electrons a... | g18955 | [
0.03647761419415474,
0.017202146351337433,
0.005149638280272484,
-0.01233025174587965,
0.06142487749457359,
-0.006781183648854494,
0.04427273944020271,
0.013244641944766045,
-0.04376368597149849,
0.024191787466406822,
-0.0025055722799152136,
0.033715926110744476,
-0.05507879704236984,
0.03... |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://physics.stackexchange.com/questions/193/best-books-for-mathematical-background">Best books for mathematical background?</a> </p>
</blockquote>
<p>I'm looking for a textbook on the group/representation theory for a student-physicist. The ma... | g185 | [
0.03344632685184479,
0.04195140674710274,
0.003394286148250103,
-0.05141046270728111,
0.006353258155286312,
0.023331986740231514,
0.020764440298080444,
0.0033570746891200542,
0.008150126785039902,
0.04025548696517944,
0.03438955545425415,
0.04887918755412102,
0.02085118740797043,
0.0332764... |
<p>In Dirac's The Principles of Quantum Mechanics he often uses the notion of "a complete set of commuting observables". This means a set of observables $\{\xi_1, \xi_2, \ldots, \xi_v, \xi_{v+1}, \ldots, \xi_u\}$ where $\{\xi_1, \xi_2, \ldots, \xi_v\}$ have discerete eigenvalues, and $\{\xi_{v+1}, \ldots, \xi_u\}$ have... | g18956 | [
0.012643757276237011,
-0.0009119907044805586,
0.010146129876375198,
-0.005062451120465994,
0.05436132103204727,
-0.0056646401062607765,
0.052063096314668655,
-0.013225561939179897,
-0.016180962324142456,
-0.03156435489654541,
-0.048411741852760315,
-0.08022050559520721,
-0.021212907508015633... |
<p><a href="http://en.wikipedia.org/wiki/David_Deutsch" rel="nofollow">David Deutsch</a> (Oxford University) asked the following question which I think is an interesting one:</p>
<p>In what class of 4-dimensional spacetimes does there exist a real, non-constant scalar field φ with the following properties:</p>
<ul>
<... | g18957 | [
-0.0194891057908535,
-0.02481747232377529,
-0.006288235541433096,
-0.018283234909176826,
0.05270148068666458,
0.03825511783361435,
0.019004885107278824,
0.04060608148574829,
-0.04020791873335838,
-0.04715244472026825,
-0.08084844052791595,
-0.005504589527845383,
0.02835155837237835,
0.0612... |
<p>Gravity must decrease due to less effective mass when going inside the object but also must increase with depth inside the star due to its higher density. Is there a model or formula approximating gravity calculations along the radius (from center to surface) of the stars?</p> | g18958 | [
-0.06001434847712517,
0.03654559701681137,
-0.007427203468978405,
-0.022462446242570877,
-0.006827653385698795,
0.06633929163217545,
0.03985464945435524,
-0.005479253362864256,
-0.12210799008607864,
0.008590703830122948,
-0.025287127122282982,
0.014839889481663704,
0.062104642391204834,
0.... |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.