question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>Consider an adiabatic expansion of an ideal gas that work is done against friction or a piston. Since no heat exchange can occur the gas keep on losing energy and its temperature decreases and the gas molecules getting further and further apart. In principle the temperature can get down to a few degrees Kelvin, clos... | g16849 | [
0.06023547053337097,
-0.01897198148071766,
0.029269512742757797,
0.007384025491774082,
-0.037228427827358246,
0.011714191175997257,
-0.027293866500258446,
0.034220803529024124,
-0.044110510498285294,
-0.01961696147918701,
0.020223470404744148,
-0.016991985961794853,
-0.03470156341791153,
-... |
<p>I am studying quantum physics and there is something I don't understand:
I know that for any particle $E=hf$ (Einstein relation) and $v=\lambda f$ ($v$ is the speed of the particle).
I also know that the kinetic energy is $E_k=\frac{mv^2}{2}$.
Solving those 3 equations for $\lambda$:
$$h\frac{v}{\lambda}=\frac{mv... | g2 | [
0.0515918992459774,
0.00543631985783577,
-0.009897344745695591,
-0.02290506474673748,
0.052887316793203354,
-0.011608481407165527,
0.013225041329860687,
0.029642749577760696,
-0.08025536686182022,
-0.0211349930614233,
0.0024782856926321983,
0.01805855706334114,
-0.007545423693954945,
0.038... |
<p>My textbook says on conduction:</p>
<blockquote>
<p><em>These 'free' electrons can rapidly carry energy from the hotter to the cooler regions of the metal, so metals are generally good conductors of heat. <strong>A metal rod at 20 deg. C feels colder than a piece of wood at 20 deg. C because heat can flow more ea... | g16850 | [
0.07298731803894043,
0.025072434917092323,
-0.010714721865952015,
-0.02458139881491661,
0.040170058608055115,
0.0036349757574498653,
0.023360781371593475,
0.012413977645337582,
-0.04295935481786728,
0.025375299155712128,
0.00047335485578514636,
0.10386575013399124,
-0.0138259781524539,
-0.... |
<p>It is know that digital camera is not the best device for quantitative measurements. However, it is often used in all sorts of atmospheric physics research, maily due to:</p>
<ul>
<li>Low cost and availability. This is inevitable especially in amateur research</li>
<li>Large field of view</li>
<li>Technical simplic... | g16851 | [
0.05881362780928612,
0.014893380925059319,
0.01692783646285534,
0.036149296909570694,
0.018927447497844696,
-0.0491165854036808,
0.036040298640728,
-0.015366810373961926,
-0.023536797612905502,
0.04036521166563034,
0.03266851231455803,
-0.014448145404458046,
0.029833504930138588,
0.0608800... |
<p><strong>Scenario</strong></p>
<p>I'm planning to build an electric motor for fun (not for any practical purpose). I recently purchased a shapeoko CNC mill kit and intend to manufacture most of the parts housing, stator etc. I'm currently in the planning stage and would like to plan/build this intelligently vs trial... | g16852 | [
0.00151066726539284,
-0.018365779891610146,
-0.0041609862819314,
0.03757249936461449,
0.0295568760484457,
-0.03905480355024338,
-0.0032885191030800343,
0.03411110118031502,
-0.09156728535890579,
-0.01790161244571209,
-0.06433866173028946,
0.0012483466416597366,
0.05620753765106201,
0.02120... |
<p>I have a physics simulator that simulates a bunch of balls moving and colliding with each other, and I would like to be able to "link" two balls together so they stick to each other (are always tangent to each other), i.e. I want to be able to make a chain of balls. What is the general approach to this? I've tried v... | g16853 | [
-0.0005481068510562181,
0.021812360733747482,
0.002825989155098796,
-0.07068008929491043,
0.04733698070049286,
-0.028751088306307793,
-0.0011584182502701879,
-0.02538320980966091,
-0.05325579643249512,
-0.03260841220617294,
0.03544868901371956,
-0.014121935702860355,
0.04375144839286804,
-... |
<p>I have an online homework for my Modern Physics class, that requires me to find the uncertainty in velocity and position of a duck. The question is as below:</p>
<blockquote>
<p>Suppose a duck lives in a universe in which h = 2π J · s. The duck has
a mass of 2.55 kg and is initially known to be within a pond 1.... | g16854 | [
0.02670101448893547,
0.02108260616660118,
0.0058027529157698154,
-0.0036534385289996862,
0.030675062909722328,
0.00915591698139906,
0.04605002701282501,
0.006111759226769209,
-0.035706862807273865,
-0.04430584982037544,
-0.010557577013969421,
0.034144412726163864,
-0.020093858242034912,
-0... |
<p>how are the comets able to keep to a nearly fixed orbital period, though they lose a certain amount of mass during their <a href="http://www.google.com/url?q=http://en.wikipedia.org/wiki/Apsis&sa=U&ei=WcS5T6OSF4q09QSjg4C7CA&ved=0CB8QFjAB&usg=AFQjCNEZmuswRUPV6NnBs9uTXYh0sDODYg" rel="nofollow">periheli... | g16855 | [
0.05056058615446091,
0.0038272158708423376,
0.0016234454233199358,
-0.0357438325881958,
0.021071627736091614,
0.052985116839408875,
0.0013223334681242704,
-0.052926186472177505,
-0.028780121356248856,
-0.009158283472061157,
-0.038033612072467804,
-0.010824613273143768,
0.04783792048692703,
... |
<p>A a compact, orientable, <em>spacelike</em> surface always has 2 independent forward-in-time pointing, lightlike, normal directions. For example, a (spacelike) sphere in Minkowski space has lightlike vectors pointing inward and outward along the radial direction. The inward-pointing lightlike normal vectors conve... | g16856 | [
0.030409233644604683,
0.013481630012392998,
-0.025117503479123116,
0.02377902902662754,
-0.02441820316016674,
0.04640788957476616,
0.055576782673597336,
-0.04134145379066467,
-0.0554208867251873,
-0.04383153095841408,
-0.004285035189241171,
0.00014509512402582914,
0.0305070448666811,
0.013... |
<p>Since we are on a planar system (2D system) the massless Dirac equation reads
$$\vec{\alpha}\cdot(\vec{p}-e\vec{A})\psi_E=E\psi_E$$</p>
<p>Here Dirac matrices are Pauli matrices ($\alpha^1=-\sigma^2$ , $\alpha^2=\sigma^1$)</p>
<p>To find zero-energy modes we write the wave function as $\psi_0= \begin{pmatrix}
... | g16857 | [
-0.02202664501965046,
-0.03397054225206375,
-0.024023383855819702,
0.006476770155131817,
0.10490579158067703,
0.01096573006361723,
0.02663085050880909,
0.038638632744550705,
-0.041029635816812515,
-0.0014018911169841886,
-0.06395447254180908,
-0.032779939472675323,
-0.008354101330041885,
0... |
<p>I quote from my textbook, " Consider two vertical slits S1 and S2 placed parallel to each other, and a string is passed through them. The end B is fixed and A is given jerks perpendicular to its length. If on rotating slit S2 till it is perpendicular to S1 the amplitude of vibrations becomes zero then the wave is a ... | g16858 | [
0.04611664265394211,
0.04924662411212921,
0.010483655147254467,
-0.0023308414965867996,
-0.007341355085372925,
-0.01634306088089943,
0.0752449557185173,
0.04875907301902771,
-0.022924106568098068,
-0.03050665557384491,
0.05960827320814133,
0.018299080431461334,
-0.03216709941625595,
0.0454... |
<p>It seems like it's a given that the laws of physics that govern our universe are consistent, and that inconsistency somehow is a reason to doubt an explanatory theory (such as famously Godel's spinning universes leading to an inconsistency that caused Einstein to doubt his own theory).</p>
<p>Why?</p>
<p>Along the... | g16859 | [
0.006480783224105835,
0.038233716040849686,
0.010767488740384579,
-0.0014771412825211883,
0.03661709278821945,
0.00995324645191431,
-0.0095768291503191,
0.05382972210645676,
0.006874334067106247,
-0.05950947478413582,
-0.004233697894960642,
-0.06283864378929138,
0.04611722752451897,
0.0638... |
<p>OK, this may be a hard question to answer and really all I am looking for is an equation as I don't even know what to call this.</p>
<p>This is all for a game so bare with me please.</p>
<p>In the game two vehicles,which hover over the terrain, fight each other face to face with projectiles.</p>
<p>The projectile... | g16860 | [
-0.005333451554179192,
-0.03854226693511009,
-0.0231052003800869,
0.028628898784518242,
0.029039638116955757,
-0.007663356140255928,
0.03669310361146927,
-0.07168002426624298,
-0.03893767669796944,
-0.03546498343348503,
0.023802340030670166,
0.006185290403664112,
0.08999898284673691,
-0.02... |
<p>Basically is the black hole itself affected by the matter going into it? Does it either get pulled by gravity toward things or have its own velocity affected by matter that "impacts" it?</p> | g16861 | [
-0.004354046657681465,
0.01673784852027893,
0.03248688206076622,
0.014738654717803001,
0.027156976982951164,
0.013251920230686665,
0.031247783452272415,
0.0072546908631920815,
-0.03249051794409752,
-0.03916137292981148,
0.03386789932847023,
-0.0006689763395115733,
0.0185079425573349,
0.011... |
<p>In this question I am <em>not considering the sun</em>, but only other stars.</p>
<p>Stars are big, but they are also far away.
<a href="https://en.wikipedia.org/wiki/Star" rel="nofollow">https://en.wikipedia.org/wiki/Star</a></p>
<blockquote>
<p>The nearest star to the Earth, apart from the Sun, is Proxima Cent... | g16862 | [
0.005640946328639984,
0.026870863512158394,
0.003392533166334033,
-0.0036882725544273853,
-0.013944147154688835,
0.013569180853664875,
-0.013632319867610931,
0.004670672118663788,
-0.004689803812652826,
-0.01351793110370636,
0.07449479401111603,
0.06108876317739487,
0.04676489904522896,
-0... |
<p>Suppose I have two wavelengths of light ($r_1$, $r_2$) coming from a source. These rays are then reflected specularly on a surface. What is the minimum distance required for the two wave trains of light to be considered a metamer, or perceived as one color by the eye? What would be their apparent color if $r_1$ is <... | g16863 | [
-0.0213497094810009,
0.029493477195501328,
-0.015385373495519161,
-0.012708034366369247,
0.02558780089020729,
0.01587330549955368,
0.013459518551826477,
0.04854169115424156,
0.003892956767231226,
-0.021822288632392883,
-0.027880433946847916,
0.01693113148212433,
0.0259725209325552,
0.03172... |
<p>I found out black heats up the most and white the least, as I expected.
The question I had is that despite black reflecting all the wavelengths of the visible spectrum, and hence giving the black material its colour, why is it not the coolest?</p>
<p>I mean, even blue. It's reflecting the higher frequencies, which ... | g508 | [
0.05594758316874504,
-0.0036066656466573477,
0.021614693105220795,
-0.016576586291193962,
0.1049613431096077,
-0.029521290212869644,
-0.04767272248864174,
0.05972389504313469,
0.015604334883391857,
-0.031910527497529984,
0.05706550553441048,
0.04886841028928757,
0.025275111198425293,
0.018... |
<p>This is about validating the science from a science fiction novel. </p>
<p>My understanding is that speed is all relative. So while I am in a car on the freeway my speed relative to another passenger is zero, relative to a street sign is 75, relative to a car travelling the opposite direction is 150, and relative t... | g16864 | [
0.008383781649172306,
0.04595060274004936,
0.021103868260979652,
0.0025367289781570435,
0.04485089331865311,
0.013998179696500301,
0.024688253179192543,
0.04933123290538788,
-0.03348667547106743,
-0.008894549682736397,
0.07901172339916229,
0.008934156969189644,
0.03817751258611679,
0.01278... |
<p>In physical cosmology, the content of the Universe is modeled by the stress-energy-momentum tensor of perfect fluid, with energy density rho(t) and pressure P(t). I'm wondering, why not use ideal gas instead？</p> | g16865 | [
-0.005764590576291084,
-0.01907752826809883,
-0.020655861124396324,
-0.001780246035195887,
-0.01115499623119831,
0.02404117025434971,
-0.06805552542209625,
0.018350010737776756,
-0.07567035406827927,
-0.0002609236107673496,
0.03479049354791641,
-0.04689698666334152,
0.03103466145694256,
-0... |
<p>I have been going back through some Kleppner problems and have a doubt concerning problem 6.18. It states: </p>
<blockquote>
<p>Find the period of a pendulum consisting of a disk of mass $M$ and radius $R$ fixed to the end of a rod of length $l$ and mass $m$. How does the period change if the disk is mounted to t... | g16866 | [
0.06274428963661194,
-0.01684848964214325,
0.01374763809144497,
-0.005276767071336508,
0.012294284068048,
0.004606377333402634,
0.08753407746553421,
-0.01857420988380909,
-0.05039871484041214,
0.03379899635910988,
-0.03851427882909775,
-0.03567596152424812,
-0.01150513719767332,
-0.0324733... |
<p>I have another doubt with a Kleppner problem :(. </p>
<blockquote>
<p>A thin plank of mass M and length l is pivoted at one end. The plank is released at 60$^{\circ}$ from the vertical. What is the magnitude and direction of the force on the pivot when the plank is horizontal?</p>
</blockquote>
<p>My process dif... | g16867 | [
0.11281811445951462,
0.05059371143579483,
0.015612923540174961,
0.02047712542116642,
0.04239216074347496,
0.019808147102594376,
0.05183626711368561,
0.017363907769322395,
-0.052845701575279236,
-0.00002711187335080467,
-0.0022362731397151947,
-0.04354025796055794,
-0.029820598661899567,
-0... |
<p>I would like to evaluate frequency of some unstable periodic signal coming from a detector:</p>
<p><img src="http://i.stack.imgur.com/X5P2i.png" alt="signal started">
<img src="http://i.stack.imgur.com/Zc9UZ.png" alt="period zoom"></p>
<p>The signal is registered continuously and may or may not be present (i.e. be... | g16868 | [
-0.011339366436004639,
-0.06029883399605751,
0.01024286076426506,
-0.027453240007162094,
0.04401078075170517,
-0.04926499351859093,
-0.022589676082134247,
-0.0021653282456099987,
-0.05744406208395958,
-0.04191743955016136,
0.017840249463915825,
0.07563698291778564,
0.045453887432813644,
0.... |
<p>I suspect this has been asked here before, but I didn't find anything using Search.</p>
<p>Why is Newton's second law only second-order in position? For instance, could there exist higher-order masses $m_i$ with</p>
<p>$$F(x) = m\ddot{x} + \sum_{i=3}^{\infty} m_i x^{(i)}?$$</p>
<p>Are there theoretical reasons wh... | g16869 | [
0.013504822738468647,
0.021855980157852173,
-0.011851081624627113,
-0.005430676508694887,
0.080716073513031,
0.006628470495343208,
-0.036747198551893234,
-0.006389331538230181,
-0.07814144343137741,
-0.017637670040130615,
-0.03368629887700081,
-0.023477716371417046,
0.011369114741683006,
-... |
<p>If there was an asteroid that happened to be made out of something really solid (iron, titanium?) and it got enough velocity (sling shot around the sun?), is it conceivable that it could hit a planet dead on and keep right on going?</p> | g16870 | [
0.036513764411211014,
0.03845735639333725,
0.016071248799562454,
-0.02144276164472103,
0.044483136385679245,
0.04852357879281044,
-0.04255983978509903,
-0.07834803313016891,
0.0445677824318409,
-0.023175304755568504,
0.02452891133725643,
0.01842312328517437,
0.04237610846757889,
-0.0707324... |
<p>Can anyone show detailed proof of why radius of convergence of perturbation series in quantum electrodynamics is zero? And how is perturbation series constructed?</p>
<p>So, as this argument requires imaginary electric charge of bispinor field (negative coupling constant), how is this argument considered valid? </p... | g16871 | [
0.06210421770811081,
0.0051713017746806145,
-0.009747093543410301,
-0.03801342099905014,
0.02318943850696087,
0.03615203872323036,
0.02120172791182995,
0.006600173190236092,
-0.020078787580132484,
0.03312660753726959,
-0.030889617279171944,
0.020186608657240868,
-0.020171567797660828,
0.04... |
<p>From the <a href="http://en.wikipedia.org/wiki/Tachyon" rel="nofollow">wikipedia article on tachyons</a>:</p>
<blockquote>
<p>Most physicists think that faster-than-light particles cannot exist because they are not consistent with the known laws of physics.[3][5] If such particles did exist, they could be used to... | g16872 | [
0.07044760882854462,
0.017668839544057846,
0.031252775341272354,
-0.021900000050663948,
0.03979988768696785,
-0.011316955089569092,
-0.011513861827552319,
0.0358797125518322,
-0.01625334843993187,
0.003336995607241988,
0.028673579916357994,
-0.013001451268792152,
-0.004109494853764772,
0.0... |
<p>I had a discussion at work regarding a recent fusion <a href="http://arstechnica.com/science/2013/11/fusion-reactor-achieves-tenfold-increase-in-plasma-confinement-time/" rel="nofollow">experiment</a> in China that resulted in temperatures five times hotter than the Sun. Someone mentioned that no one can know the te... | g16873 | [
0.010162018239498138,
0.022923732176423073,
-0.014380818232893944,
-0.027653416618704796,
0.022642025724053383,
-0.07021468132734299,
0.0034575241152197123,
0.02550058811903,
-0.04268035665154457,
-0.01292822603136301,
-0.017759213224053383,
0.019995832815766335,
0.06354627013206482,
0.007... |
<p>I am a teacher planning a unit on climate change. I came across this statement: "Clouds are water vapor (green house gas) and water molecules will reflect heat into space… actually clouds are condensed water and the water molecule absorbs the heat, lowering the temperature of the atmosphere around the cloud." I do... | g16874 | [
0.0016229473985731602,
-0.015029404312372208,
-0.0010560195660218596,
0.024350326508283615,
0.0286351777613163,
0.07232183963060379,
-0.04612399637699127,
0.035540975630283356,
-0.018477413803339005,
-0.03209201991558075,
0.024991199374198914,
0.04109429568052292,
0.05195481702685356,
0.03... |
<p>Lorentz contraction and time dilatation can be deduced without Lorentz transformation. Can you deduce also the theorem of <a href="http://en.wikipedia.org/wiki/Velocity-addition_formula">addition of velocities</a> </p>
<p>$$w~=~\dfrac{u+v}{1+uv/c^2}$$ </p>
<p>without Lorentz transformation? Using just the constanc... | g687 | [
0.01786777377128601,
0.02506476640701294,
-0.009894272312521935,
0.04197059944272041,
-0.010298389010131359,
-0.03389991074800491,
0.052956752479076385,
-0.015525135211646557,
0.019712751731276512,
-0.01861722394824028,
-0.031313952058553696,
0.002831830410286784,
-0.0009469403885304928,
0... |
<p>I have a 20x20cm piece of foil with a circular hole of diameter 1cm in the centre.</p>
<p>If I slowly stretch the foil both horizontally and vertically, what happens to the size of the hole?</p>
<p>Does the size of the hole change? If the foil doubles in size to 40x40cm, will the hole be of diameter 2cm? Do any fa... | g16875 | [
0.060907699167728424,
0.01730647124350071,
0.015598434023559093,
-0.03069901093840599,
-0.019613880664110184,
0.023002807050943375,
0.0010627803858369589,
0.034282077103853226,
-0.026396581903100014,
0.0016675436636433005,
0.008995226584374905,
0.03491998836398125,
-0.060561273247003555,
-... |
<p>If a body is revolving around a point at radius R with tangential velocity V, does General Relativity predict that at some tangential speed, the body will revolve around the point without any external forces acting on it? Since General Relativity models gravity as a curvature of spacetime, I was thinking that an ob... | g16876 | [
0.015696128830313683,
0.04477274417877197,
0.012090484611690044,
0.010321484878659248,
0.02833348885178566,
0.019115766510367393,
0.05124136060476303,
0.006246782839298248,
-0.003003278747200966,
-0.0052337078377604485,
0.012161396443843842,
0.014353523030877113,
0.03523531183600426,
-0.03... |
<p>I have a servo that is fixed and that can move a heavy load approximately one inch. I need the fixed servo to move a light load approximately 4 inches. How can I do this with a set of pulleys? Is it even possible. I don't have access to any sort of gears or timing belts either, just pulleys.</p> | g16877 | [
0.017485463991761208,
0.026717351749539375,
-0.009432671591639519,
0.0012629140401259065,
-0.021178610622882843,
-0.015022212639451027,
-0.022155841812491417,
-0.009545937180519104,
-0.07428596913814545,
-0.022131336852908134,
-0.09277737885713577,
-0.047074172645807266,
-0.01014777272939682... |
<p>The following is a question from a past exam paper that I'm working on, as I have an exam coming soon. I would appreciate any help.</p>
<hr>
<p>A fairground ride takes the form of a hollow, cylinder of radius $R$ rotating about
its axis. People stand against the cylinder wall when it is stationary and its axis is
... | g16878 | [
0.030662517994642258,
0.011343464255332947,
0.002344102831557393,
-0.018865035846829414,
0.005752142518758774,
0.01450033113360405,
0.17156639695167542,
-0.0434393435716629,
-0.08491817116737366,
0.00852914433926344,
-0.06256021559238434,
0.03675752133131027,
-0.003553217276930809,
-0.0361... |
<p>If in DC , Emf is the work done to carry a unit positive charge from -ve to +ve terminal . </p>
<p>What is induced EMF then , in a similar sense ? To carry a unit charge around a loop once along a fixed circuit ? Where is a -ve to +ve place ? </p> | g16879 | [
0.021823573857545853,
-0.03461115062236786,
-0.02331634797155857,
-0.03512294590473175,
0.06986561417579651,
0.011316181160509586,
0.04732716456055641,
0.02485491707921028,
-0.07213346660137177,
-0.02517789602279663,
-0.13218024373054504,
0.028407497331500053,
-0.026428697630763054,
0.0082... |
<p>The definitions between on- and off-shell are given in <a href="http://en.wikipedia.org/wiki/On_shell_and_off_shell">Wikipedia</a>. </p>
<p>Why is it so important in QFT to distinguish these two notions ?</p> | g16880 | [
0.024878136813640594,
0.021522874012589455,
-0.014525185339152813,
-0.05773847922682762,
0.05717819929122925,
-0.026168139651417732,
0.0032058251090347767,
0.008491473272442818,
-0.014274911023676395,
-0.04767721891403198,
-0.05444645509123802,
0.018945351243019104,
0.03080526366829872,
0.... |
<p>I'm interested in calculating the operator norm of a Hermitian operator, say $B$, acting on the Hilbert space of square integrable functions. The context is I have an optical system in all its infinite dimensional glory. To be clear, by operator norm I mean the largest eigenvalue, or
$||B||_{\infty}=\sup \{ \langl... | g16881 | [
-0.032034557312726974,
-0.0376196950674057,
0.02519671432673931,
0.006768606603145599,
-0.03417041897773743,
-0.07064434885978699,
0.04323503002524376,
0.08641525357961655,
-0.005647984333336353,
0.04676429182291031,
-0.02430167980492115,
0.012893886305391788,
-0.009714756160974503,
0.0430... |
<blockquote>
<p>$\require{mhchem}$What is the energy $Q$ released when $\ce{^131_53I}$ decays and $\ce{^131_54 Xe}$ is formed? The atomic mass of $\ce{I}$ is $130.906118~u$ and the atomic mass of $\ce{Xe}$ is $130.90508~u$.</p>
</blockquote>
<p>To compute $\Delta m$, I thought of $130.90508~u - 130.906118~u = 0.2989... | g16882 | [
-0.02399252913892269,
-0.006471451837569475,
0.008393757045269012,
0.022863775491714478,
0.01578882895410061,
0.016664857044816017,
0.023845521733164787,
0.09855737537145615,
-0.014469722285866737,
-0.00025825711782090366,
-0.025507837533950806,
-0.007239174097776413,
0.025901205837726593,
... |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://physics.stackexchange.com/questions/24042/baryon-asymmetry">Baryon asymmetry</a> </p>
</blockquote>
<p>Baryon asymmetry refers to the observation that apparently there is matter in the Universe but not much antimatter. We don't see galaxie... | g509 | [
0.017930852249264717,
0.01275434996932745,
0.0011654330883175135,
-0.028940269723534584,
0.10508222132921219,
0.00483745476230979,
0.0026559613179415464,
-0.0016094325110316277,
-0.024673493579030037,
0.02018284983932972,
0.11927002668380737,
-0.012841529212892056,
0.02024666592478752,
0.0... |
<p>I was talking about K3 surfaces with some physicists, and one of them told me that the N=4 superconformal field theories with central charge 6 are expected to be relatively scarce. In particular, one should expect a lot of a priori different theories (e.g., those coming from sigma models whose targets are different... | g16883 | [
0.032261770218610764,
0.07537279278039932,
-0.008413503877818584,
0.029693109914660454,
0.025629466399550438,
0.018129752948880196,
0.007109552156180143,
-0.02846195176243782,
0.029093245044350624,
-0.048089511692523956,
-0.03928835317492485,
-0.044533077627420425,
0.018338417634367943,
0.... |
<p>If I break an egg, how broken it is depends on "when" I am not "where" I am. Why is the time dimension special?</p> | g16884 | [
-0.004791915882378817,
0.07500633597373962,
0.0014433134347200394,
0.004471261985599995,
-0.04920336231589317,
0.03421355038881302,
0.005175875965505838,
0.004201391711831093,
-0.04315396398305893,
-0.0015124671626836061,
-0.034818682819604874,
0.006369233131408691,
-0.004851359874010086,
... |
<p>I've read in many places that centre of lift is about quarter chord of the wing and that post-stall lift (the part developed on lower surface) has centre midchord. The later makes sense; the pressure is distributed more or less uniformly (or at least symmetrically) on the lower surface. But what determines the centr... | g16885 | [
0.05330420657992363,
-0.017762038856744766,
-0.03973221406340599,
0.00477080512791872,
0.02253299206495285,
0.0313711017370224,
0.044366512447595596,
0.01899297721683979,
-0.0289712306112051,
-0.0648643895983696,
0.013678813353180885,
0.020236752927303314,
0.011288663372397423,
-0.05195266... |
<p>I am looking at S-duality a bit, and was wondering if anyone had the answer to the following question. It is known that the supersymmetric Yang-Mills theory in 4 space dimensions is self-dual with gauge group or U(N) or SU(2). But is it known whether there are more Yang-Mills theories that are self-dual? On the ot... | g16886 | [
0.0033711937721818686,
0.03005206398665905,
-0.001212659990414977,
0.047207310795784,
-0.02774994820356369,
0.042712513357400894,
0.005212548654526472,
0.038160890340805054,
0.004997720010578632,
0.03435332700610161,
-0.013215148821473122,
-0.048090722411870956,
0.045464858412742615,
0.037... |
<p>Here is what I know:</p>
<p>$F = E q = m a$ </p>
<p>so $a = \frac{E q}{ m}$</p>
<p>and we can increase the acceleration ($a$) of a particle in an electric field ($E$) by either decreasing its mass ($m$) or increasing its charge ($q$).</p>
<p>Here is where I am confused:</p>
<p>$a = \frac{v}{ t}$, thus $E = \... | g16887 | [
0.07486619800329208,
0.057147614657878876,
0.009771102108061314,
0.022828483954072,
0.12461481243371964,
0.014383881352841854,
0.033193644136190414,
0.03488437831401825,
-0.06653362512588501,
-0.020283522084355354,
0.0014806394465267658,
0.011764531023800373,
0.021480297669768333,
0.025233... |
<p>Following Polchinski's book (String Theory 1), we have the bc action :</p>
<p>$$S = \frac{1}{2 \pi}\int~d^2z ~b\bar \partial c\tag{2.5.4}$$</p>
<p>where $b$ and $c$ have holomorphic weights $\lambda$ and $1- \lambda$.</p>
<p>From this action, it is said, that applying the Noether's theorem, we get the energy-mome... | g16888 | [
0.020171429961919785,
-0.043788131326436996,
-0.017729826271533966,
0.0037136676255613565,
0.05784743279218674,
-0.010532353073358536,
0.07272765040397644,
0.01871318183839321,
-0.009376528672873974,
0.01261294074356556,
-0.04445360600948334,
-0.0307723730802536,
-0.04429345950484276,
-0.0... |
<p>An excerpt from <a href="http://www.chem4kids.com/files/matter_gas.html" rel="nofollow">this</a> page:</p>
<blockquote>
<p>Gases can fill a container of any size or shape. It doesn't even matter how big the container is. The molecules still spread out to fill the whole space equally. That is one of their physical... | g16889 | [
0.016217101365327835,
0.054109279066324234,
0.008898014202713966,
0.015229248441755772,
0.00857475958764553,
0.023263761773705482,
-0.03900502994656563,
0.034795187413692474,
-0.06769176572561264,
-0.06779004633426666,
0.038922809064388275,
-0.05113198235630989,
0.020787889137864113,
0.011... |
<p>Since we all know that to increase the magnetic field we can do these of the following things:</p>
<p>(i) Increase the number of turns in a coil,</p>
<p>(ii) Increase the current following through conductor,</p>
<p>and there would be more but I know only these (upto my standard - Xth )</p>
<p>now if I use the fi... | g16890 | [
0.032095108181238174,
0.04216820001602173,
0.008832955732941628,
-0.029419230297207832,
0.0588533990085125,
-0.0009477991261519492,
0.027264021337032318,
0.018685150891542435,
-0.020702006295323372,
-0.012242845259606838,
-0.07107110321521759,
0.012999464757740498,
0.000920870341360569,
0.... |
<p>Does a thermal photon radiate spherically whereas a photon radiates in a circle/beam?
How do you tell a thermal photon of, say 3 eV, from a photon of light?</p> | g16891 | [
0.03199358284473419,
-0.023119570687413216,
-0.01647091470658779,
0.012986032292246819,
0.009885422885417938,
-0.013063241727650166,
-0.00559183768928051,
-0.00682078255340457,
-0.01090783067047596,
0.031235292553901672,
0.024430133402347565,
0.07084619253873825,
0.02944117970764637,
-0.01... |
<p>Almost in every book on physics we can find a statement like "diffraction gets stronger when the size of the slit is comparable to the wavelength". Let's say we have a wall in a bathtub with a slit in it. When water waves reach the slit, the books usually come up with the Huygens' principle to explain that the point... | g16892 | [
0.0391378328204155,
0.04027169942855835,
-0.0013129467843100429,
-0.061527106910943985,
-0.013626551255583763,
0.024388471618294716,
0.02715545892715454,
0.009962113574147224,
-0.03484626114368439,
-0.0599396675825119,
0.04265913739800453,
0.028673667460680008,
0.008522376418113708,
0.0171... |
<blockquote>
<p><strong>Proposition:</strong> the event horizon and the apparent horizon of a black hole always coincide.</p>
</blockquote>
<p>As a reminder: the event horizon is defined as the boundary of the closure of the causal past of future null infinity, i.e. the boundary of the closure of the set of points w... | g16893 | [
0.0707305520772934,
0.01869276538491249,
0.03175213187932968,
-0.0051751709543168545,
-0.0355449840426445,
0.010240774601697922,
0.024667704477906227,
0.03311871364712715,
-0.00980748888105154,
0.027575861662626266,
0.046072445809841156,
0.017074786126613617,
-0.01661692000925541,
0.062028... |
<p>A volcano erupts 50m below the sea level. A rock leaves the crater at 20 m/s at an angle 30 deg with the vertical line. The rock has a mass of 15kg. IGNORE WATER RESISTANCE. It gets out of the water, reaches a max height and falls back it.</p>
<p>When does it reach 30 below sea for the first and second times?</p>
... | g16894 | [
0.07728682458400726,
-0.015059680677950382,
-0.0010148707078769803,
-0.037958260625600815,
0.06201242282986641,
0.051667749881744385,
0.024552220478653908,
-0.03132617101073265,
-0.06634726375341415,
-0.026748834177851677,
-0.07697609812021255,
0.02666899561882019,
0.03839396312832832,
-0.... |
<p>We know that the spin-1 chain realizes <a href="http://en.wikipedia.org/wiki/AKLT_Model">the Haldane phase</a> which is an example of
symmetry protected topological (SPT) phases (ie short-range entangled phases with symmetry). The Haldane phase is protected by the $SO(3)$ spin rotation symmetry.
If we change the sym... | g16895 | [
-0.06435886770486832,
0.034263625741004944,
0.010206875391304493,
0.041830554604530334,
-0.009521015919744968,
0.033990226686000824,
-0.003863193094730377,
0.03701381757855415,
0.07139793038368225,
-0.009182211011648178,
0.004330667667090893,
0.0044929576106369495,
-0.011965055949985981,
-... |
<p>An unbarred $B$-meson contains $\bar{b}$ (an anti-bottom quark), whereas a barred $\bar{B}$-meson contains $b$ (a bottom quark). What is the historical reason for this hellish naming convention?</p> | g16896 | [
0.06210871413350105,
0.019464218989014626,
0.00962863676249981,
-0.047701653093099594,
0.10298210382461548,
0.04218800738453865,
0.021343078464269638,
-0.023543793708086014,
-0.021182013675570488,
-0.04119464010000229,
0.016551543027162552,
0.058099862188100815,
-0.010701986961066723,
0.03... |
<p>I read somewhere that $E=mc^2$ shows that if something was to travel faster than the speed of light then they would have infinite mass and would have used infinite energy. </p>
<p>How does the equation show this?</p>
<p>The reason I think this is because of this quote from Hawking (I may be misinterpreting it):</p... | g16897 | [
0.03806789591908455,
0.029290249571204185,
0.022301118820905685,
-0.008782540448009968,
0.004323936067521572,
-0.0035722970496863127,
0.049718450754880905,
0.06894280761480331,
-0.0638093501329422,
0.0009596077725291252,
-0.00924137607216835,
-0.012704247608780861,
0.04721571132540703,
0.0... |
<p>This question is about <a href="http://www.youtube.com/watch?v=vWVZ6APXM4w" rel="nofollow">this video on YouTube</a>, in which a bullet is fired vertically into the center of a wooden block from below, sending the block up into the air. Next, a bullet is fired vertically but off-center into a similar block from belo... | g16898 | [
0.07998575270175934,
0.025828009471297264,
0.009798482060432434,
0.03360269218683243,
0.028689958155155182,
0.02285214327275753,
0.06434448063373566,
0.011232568882405758,
-0.044484641402959824,
-0.013272221200168133,
-0.061166346073150635,
0.034323688596487045,
-0.011530001647770405,
0.00... |
<p>I want to calculate the efficiency of this Stirling cycle for an ideal gas $pV = nRT$</p>
<p><img src="http://i.stack.imgur.com/AhKqy.png" alt="taken from Nolting. Grundkurs Theoretische Physik 4. Spezielle Relativitätstheorie und Thermodynamik"></p>
<p>The mechanical work is</p>
<p>$$
\Delta W_{12} = - \int_{V_... | g16899 | [
-0.020621662959456444,
-0.03305008262395859,
-0.010199680924415588,
-0.020285550504922867,
0.004022959154099226,
-0.0184338316321373,
0.009987203404307365,
0.0019528291886672378,
-0.07850639522075653,
0.042348723858594894,
-0.03916242718696594,
0.036825407296419144,
-0.004295933060348034,
... |
<p>I am trying to do this question as a prep for my quals and find my solution too simplistic. I fear I am missing something important. </p>
<p>"Iron atoms (atomic mass 56) contain two free electron spins that can align with an external magnetic field. An iron wire 3 cm long and 1 mm in diameter is suspended verticall... | g16900 | [
0.015203437767922878,
0.05462224781513214,
0.002613761695101857,
-0.07686291635036469,
0.03636660799384117,
-0.020555658265948296,
0.056421589106321335,
-0.037463732063770294,
-0.029105253517627716,
0.06451921164989471,
-0.025920450687408447,
0.01773884892463684,
-0.015910815447568893,
-0.... |
<p>I am wondering if beyond <a href="http://theoreticalphysics.stackexchange.com/questions/28/physical-interpretation-of-different-selfadjoint-extensions">physical interpretation</a>, the one dimensional contact interactions (self-adjoint extensions of the the free Hamiltonian when defined everywhere except at the orig... | g16901 | [
0.010946547612547874,
0.03899543732404709,
-0.017430715262889862,
-0.013701314106583595,
0.02624039351940155,
-0.03155682608485222,
0.02466096729040146,
-0.051628876477479935,
-0.0012415166711434722,
0.03415601700544357,
0.001158356899395585,
-0.031037386506795883,
0.0003312023764010519,
0... |
<p>In a 3d SU(N) gauge theory with action $\frac{k}{4\pi} \int \mathrm{Tr} (A \wedge dA + \frac{2}{3} A \wedge A \wedge A)$, where the generators are normalized to $\mathrm{Tr}(T^a T^b)=\frac{1}{2}\delta^{ab}$, it is well known the Chern-Simons level $k$ is quantized to integer values, i.e. $k \in \mathbb{Z}$. </p>
<p... | g16902 | [
0.009180635213851929,
0.0029795037116855383,
-0.02190883830189705,
0.013091091066598892,
0.003581876866519451,
0.0062932223081588745,
0.03271373733878136,
0.03391210734844208,
0.005928887519985437,
0.06213937699794769,
-0.017499227076768875,
-0.03925636410713196,
0.02466883324086666,
0.026... |
<p>Can we view the normal, non-relativistic quantum mechanics as a classical fields?</p>
<p>I know, that one can derive the Schrödinger equation from the Lagrangian density</p>
<p>$${\cal L} ~=~ \frac{i\hbar}{2} (\psi^* \dot\psi - \dot\psi^* \psi) - \frac{\hbar^2}{2m}\nabla\psi^* \cdot \nabla \psi - V({\rm r},t) \psi... | g16903 | [
0.03198866918683052,
0.014749928377568722,
-0.021323751658201218,
-0.02173674665391445,
0.03028234839439392,
-0.0090492470189929,
0.026146337389945984,
0.004187215585261583,
0.023314202204346657,
-0.012138376012444496,
0.048309359699487686,
-0.02552216500043869,
-0.02897455543279648,
-0.01... |
<p>In some theories inflation is supposed to be able to turn quantum fluctuations into macroscopic inhomogeneities.</p>
<p>I don't understand how an isolated system such as the universe can undergo such a random transformation : if at the beginning the universe is in a state $A$, quantum mechanics says that $A$ will e... | g16904 | [
-0.07086485624313354,
0.01894252374768257,
-0.005569969303905964,
0.0060983519069850445,
-0.007874647155404091,
0.018357500433921814,
0.0028391436208039522,
0.028881443664431572,
0.038126446306705475,
-0.04622166231274605,
-0.04036909341812134,
0.026620635762810707,
0.033062804490327835,
0... |
<p>I was reading the heterotic string section of <a href="http://arxiv.org/abs/hep-th/0109149.pdf" rel="nofollow">this thesis desertation by Luboš Motl</a>, since I <em>think</em> I now understand the Type IIA Matrix String Theory. The only thing I knew about Type HE Matrix Strings, however, was:</p>
<p>That It has a... | g16905 | [
0.0248486939817667,
0.056114789098501205,
-0.019626203924417496,
-0.06911154091358185,
0.04286005347967148,
0.006742635741829872,
-0.008439557626843452,
-0.017070656642317772,
-0.029247581958770752,
-0.014192590489983559,
-0.0018209745176136494,
-0.0089803421869874,
0.028505275025963783,
0... |
<p>Here is a question I am trying to solve. Sorry for the highlighting, it is not relevant.</p>
<p><img src="http://i.stack.imgur.com/9OxTR.png" alt="enter image description here"></p>
<p>Here are my answers.</p>
<p>For a), I would write $dE = dQ + dW$, following the first principle of thermodynamics. And for $dW$, ... | g16906 | [
0.03459852188825607,
-0.014792787842452526,
0.005841153208166361,
-0.026233913376927376,
0.02781268022954464,
-0.048036374151706696,
0.04028860107064247,
-0.001579758245497942,
-0.079147107899189,
-0.003950466867536306,
-0.01990508660674095,
0.006280158180743456,
0.0580449253320694,
0.0145... |
<p>This question combines several sub-questions, the common theme being: why the known 5 string theories are unique?</p>
<p>Firstly, regarding heterotic theory. I understand the only allowed gauge groups are $E_8\times E_8$ and $Spin(32)/\mathbb{Z}_2$. I wanted to ask why these are the only two options but then I foun... | g16907 | [
0.01279835868626833,
0.05548468604683876,
0.007916014641523361,
-0.023490436375141144,
0.03331378102302551,
0.0215950645506382,
0.04553794488310814,
-0.004832896403968334,
-0.022588463500142097,
-0.029940729960799217,
-0.035311464220285416,
0.013184870593249798,
-0.01644476130604744,
0.065... |
<p>Can you recommend to me good references on this action? From basics to more advanced stuff.</p> | g393 | [
0.04446842521429062,
-0.018445704132318497,
-0.008010754361748695,
0.03678034245967865,
0.04287995770573616,
-0.02664226107299328,
0.02571209706366062,
0.01368762832134962,
0.015302283689379692,
-0.010216280817985535,
0.019359806552529335,
-0.0026517226360738277,
0.020907390862703323,
-0.0... |
<p>An external charge when brought close to a conductor induces bound charges on the nearer side and free charges on the further side so that the field induced in the conductor can counterbalance the field due to the external charge,right? Now in case of 2 concentric spheres, if the outer one is charged & the inner... | g16908 | [
0.024234194308519363,
0.005177907645702362,
0.009380707517266273,
-0.011972854845225811,
0.03453303501009941,
0.05949648842215538,
0.02068563550710678,
-0.00015285733388736844,
-0.0082808593288064,
-0.023663492873311043,
-0.07550156116485596,
0.010316221043467522,
0.014776494354009628,
-0.... |
<p>In an inflationary model of our universe, the space-time expands within a finite boundary. Some other models are also proposed where the universe is not explained to have been expanding rather the masses of the objects are presented to be expanding with time. If so, what happens to the information scattered in space... | g16909 | [
0.007866043597459793,
0.06554169952869415,
-0.004804862663149834,
0.010443381033837795,
0.009505254216492176,
0.03571982681751251,
-0.0378466434776783,
-0.03614839166402817,
-0.016961902379989624,
-0.0469818077981472,
0.03470257297158241,
-0.037347692996263504,
0.02434292621910572,
0.01430... |
<p>I understand why amplitude doesn't affect the speed of the sound AFTER the 'leading compression'. The extra force provided on one stage of the cycle is countered on the other stage. But shouldn't the 'leading compression' travel faster if amplitude is greater? Because wave motion hasn't been set up yet shouldn't all... | g16910 | [
0.018510164692997932,
0.038332708179950714,
0.0100090391933918,
-0.0012953713303431869,
0.02895253337919712,
-0.002529482590034604,
0.09424246102571487,
0.030254831537604332,
-0.03391936048865318,
-0.028824184089899063,
-0.028175421059131622,
-0.01917424611747265,
-0.04278484731912613,
0.0... |
<p>This is an exercise of my last exam. Since I couldn't find anybody who solved it or knows how to, it would be really nice if somebody could tell me if my thoughts on it go into the right direction.</p>
<p>Two harmonic Oscillators can be described by the Hamiltonian </p>
<p>$\hat H_a + \hat H_b + \hat H_c$ </p>
... | g16911 | [
0.02523593232035637,
-0.019519764930009842,
0.003596823662519455,
-0.03726120665669441,
0.040606360882520676,
-0.02810787968337536,
0.04827987775206566,
0.06321801990270615,
0.014361598528921604,
0.014606771059334278,
-0.010888724587857723,
0.01636471226811409,
-0.04519481584429741,
0.0513... |
<p>What would you see if you have 2 huge mirrors (you cant look over it or next to it)</p>
<p>You place them with the reflecting side to each other and you look in the mirror from behind one mirror (one way mirror = 1 side glass 1 side mirror, like in a movie when cops are questioning a suspect.)</p>
<p>The mirror wo... | g698 | [
-0.03519700467586517,
0.022852525115013123,
-0.0008049568277783692,
0.0025097148027271032,
0.020528297871351242,
0.019656339660286903,
0.035161711275577545,
0.10121075063943863,
-0.020439906045794487,
-0.059285007417201996,
0.016285603865981102,
0.052217673510313034,
0.029080364853143692,
... |
<p>I would be highly obliged if someone would guide me in the right direction regarding this.</p>
<p>I am trying to understand and mathematically explain the relation between angular velocities as observed by a moving observer of an otherwise, static object.
For example-
A tree passes by, as we travel in a bus. </p>
... | g16912 | [
0.03480816259980202,
0.01518719457089901,
0.013373651541769505,
0.0009727127035148442,
0.035997290164232254,
-0.020772051066160202,
0.037464313209056854,
0.015577990561723709,
-0.0016574867768213153,
-0.004226165823638439,
-0.016720155254006386,
-0.0013268491020426154,
0.08187418431043625,
... |
<p>I have a question the variation of the Polyakov action, related to <a href="http://physics.stackexchange.com/q/72948/">this </a> Phys.SE post.</p>
<p>For Polyakov action
$$ S_p[X,\gamma]=-\frac{1}{4 \pi \alpha'} \int_{-\infty}^{\infty} d \tau \int_0^l d \sigma (-\gamma)^{1/2} \gamma^{ab} \partial_a X^{\mu} \partia... | g16913 | [
0.032527823001146317,
-0.04969717934727669,
0.0018499321304261684,
0.00642748549580574,
0.025414010509848595,
0.026096630841493607,
0.08418670296669006,
0.009488681331276894,
0.0028763022273778915,
-0.02938675507903099,
-0.04245978593826294,
0.05503761023283005,
-0.023677479475736618,
0.03... |
<p>In brief, is there a list of spin glass transition properties for the RBIM on different lattices? Is there any know results about the relationships between these probabilities for a graph and its dual?</p>
<p>In more detail:</p>
<p>I'm interested in RBIMs on a multitude of lattices. Specifically, I'm interested in... | g16914 | [
-0.0453668013215065,
0.004234564956277609,
-0.0015556988073512912,
0.0370851568877697,
0.0062988996505737305,
-0.04336900636553764,
0.03841887786984444,
0.06564304232597351,
0.06557352840900421,
-0.008804877288639545,
0.018764477223157883,
0.06664223968982697,
-0.015864303335547447,
-0.012... |
<p>Suppose that a qubit in an initial state that we don't know was measured, and the result was 1.
Is it possible to know the initial state of the qubit by the result measured? And if the result would have been 0?</p> | g16915 | [
0.007660865318030119,
-0.008683557622134686,
0.017622174695134163,
-0.033655084669589996,
0.00404485035687685,
-0.010927727445960045,
-0.009588631801307201,
0.0013813817640766501,
0.005338660441339016,
-0.011679885908961296,
-0.05772576108574867,
0.04102582857012749,
0.0016812534304335713,
... |
<p>The formula for a capacitor discharging is $Q=Q_0e^{-\frac{t}{RC}}$
Where $Q_0$ is the maximum charge. But what property defines the maximum charge a capacitor can store? </p>
<p>If it depends on capacitance then that means it depends on the voltage you put across the capacitor, but how can any capacitor "cope" wit... | g16916 | [
0.051134683191776276,
0.03472922742366791,
-0.006760225165635347,
0.047623809427022934,
0.03958476707339287,
-0.010679089464247227,
-0.006658762693405151,
-0.02199568971991539,
-0.05666840076446533,
-0.02615285851061344,
-0.07563044875860214,
-0.011818126775324345,
0.020682139322161674,
0.... |
<p>Suppose we have a shell with mass $M$ and radius $R$. If we let that roll without slipping down a ramp of angle theta to the horizontal, we can easily find the acceleration of the shell the instant the ball is let go. </p>
<p>Now, what if we completely fill the shell of mass $M$ and radius $R$ with a frictionless f... | g16917 | [
0.10286490619182587,
0.026839811354875565,
0.015219095163047314,
-0.026731466874480247,
0.0402798056602478,
0.029104286804795265,
0.05415569618344307,
-0.008479760028421879,
-0.06989321112632751,
-0.006850818637758493,
-0.05423927307128906,
0.004681759513914585,
0.02027565985918045,
0.0353... |
<p>Rotating Bucket, gravity, euler fluid. E.g faber ch 2 or landau, if we start from the full 3 d equations in cylindrical coördinaties, we have symmetry over the azimuthal angle, but why is there symmetry for radius and z ? I.e why pressure and speed should not depend on r and z ?
For example, I may have vortex in z a... | g16918 | [
0.018942248076200485,
0.022898294031620026,
0.01293105911463499,
0.041525665670633316,
0.05710136145353317,
-0.012155195698142052,
0.13894635438919067,
-0.0023334301076829433,
-0.09193367511034012,
0.0076071275398135185,
-0.009085464291274548,
-0.012110831215977669,
0.00027276380569674075,
... |
<p>We've all been there: you drop your bottle of soda at some point and when you try to open it, it bursts into foam.</p>
<p>My question is, then: why does shaking a carbonated drink make the dissolved gas escape?</p>
<p>(I can't think of appropriate tags for this so feel free to retag.)</p> | g16919 | [
0.006822630763053894,
0.018924670293927193,
0.015308313071727753,
0.07991219311952591,
0.05012211948633194,
0.00581803685054183,
0.06079142168164253,
0.07213421165943146,
-0.026485208421945572,
-0.0507286861538887,
-0.05294865742325783,
-0.04129166528582573,
0.058906033635139465,
0.0111017... |
<p>Does Earth produce metallic elements in <a href="http://en.wikipedia.org/wiki/Core_of_the_Earth" rel="nofollow">its core</a>?</p> | g16920 | [
0.048858001828193665,
0.062159232795238495,
-0.005937496665865183,
-0.049608781933784485,
0.032811716198921204,
0.04271175339818001,
-0.004211849998682737,
-0.03364265337586403,
-0.008644664660096169,
0.002611311851069331,
-0.013038456439971924,
0.04044848680496216,
0.015795864164829254,
-... |
<p>I've done a fair bit of reading on this subject and I'm still confused about the basic principle of integrating out fields in QFT. When we have a function of 2 fields a and b, f(a,b), and we integrate out the heavy b-fields to give f(a), by what mechanism does the b-field dependence disappear? Are we basically sayin... | g16921 | [
0.09184026718139648,
0.031454864889383316,
0.01106770895421505,
0.00244878139346838,
0.01828986220061779,
0.02013745903968811,
0.07947775721549988,
0.03429900109767914,
-0.016977572813630104,
-0.02270585671067238,
-0.05896253138780594,
0.0045319655910134315,
-0.030006280168890953,
-0.02371... |
<p>In classic thermodynamics one can derive the Maxwell Boltzmann statistics by solving a <a href="http://en.wikipedia.org/wiki/Lagrange_multiplier" rel="nofollow">Lagrange multipliers</a> equation. In this process a new parameter $\beta$ is introduced to take account of the total energy constraint,</p>
<p>$$L = \beta... | g16922 | [
0.04779857024550438,
-0.02249661087989807,
0.005086200777441263,
-0.03448083624243736,
0.05360359326004982,
-0.011238057166337967,
0.04336422309279442,
0.015939492732286453,
-0.06812034547328949,
0.008417532779276371,
0.0006768179009668529,
0.040981393307447433,
0.06443673372268677,
0.0460... |
<p>I am looking for some explanation and if possible also some references about the applications of <a href="http://www.google.com/search?hl=en&as_q=curie+dissymmetry+principle" rel="nofollow">Curie's principle</a> in electromagnetic field Theory, precisely in the computation of magnetic (resp. electric) fields gen... | g16923 | [
-0.0032121215481311083,
0.005767513066530228,
-0.027473323047161102,
-0.0338376984000206,
0.046463143080472946,
0.012260723859071732,
0.09698497503995895,
0.07813710719347,
-0.03425857424736023,
-0.0005486152949742973,
-0.039871782064437866,
-0.0636056661605835,
0.012146378867328167,
0.002... |
<p>Its about <a href="http://en.wikipedia.org/wiki/Newton%27s_laws_of_motion" rel="nofollow">Newton's second law of motion</a>, </p>
<p>$$F=ma.$$</p>
<p>It says the acceleration of an object is directly proportional to the net force and is inversely proportional to the object's mass. Yes I can imagine that. But there... | g16924 | [
0.10400398075580597,
0.04240565001964569,
-0.007349905092269182,
0.011553723365068436,
0.09835132956504822,
0.04358042776584625,
0.03497518599033356,
0.026583710685372353,
-0.07887695729732513,
-0.030525151640176773,
-0.03179990127682686,
-0.016096696257591248,
0.05839031562209129,
-0.0125... |
<p>My friend asked me a question which was:</p>
<blockquote>
<p>For an apple resting on the floor, what is the action and reaction force pair?</p>
</blockquote>
<p>I said that the Earth exerts a gravitational force on the apple and the apple also pulls on the earth and both these forces are equal in magnitude and o... | g16925 | [
0.05809459090232849,
0.11069627851247787,
0.014071410521864891,
0.03282766044139862,
0.021295877173542976,
0.05932897701859474,
0.07941130548715591,
0.04101862758398056,
-0.05899125337600708,
-0.06307470798492432,
-0.003136494429782033,
0.011846190318465233,
-0.015225837007164955,
0.011468... |
<p>I am 32 now, and have forgotten the basic physics formulas we used in school. I am sitting with a question that is bugging me.</p>
<p>If I had to hit two golf balls of different weight with the same force, which one travels further?</p>
<p>I imagine that a $200\;\rm g$ golf ball travels farther than a $1\;\rm g$ b... | g16926 | [
0.04020160064101219,
0.025287946686148643,
0.008337043225765228,
0.0023084518034011126,
0.01222813781350851,
0.01218581385910511,
0.0032513984479010105,
-0.021853256970643997,
-0.09742362052202225,
-0.01651756837964058,
-0.023532327264547348,
-0.009037450887262821,
0.03153383731842041,
-0.... |
<p>Let us consider a 2D irrotational flow, such that $\nabla\times\boldsymbol u =\boldsymbol 0$. Defining the stream function such that $\boldsymbol u =\nabla\times\psi \boldsymbol n$ where $\boldsymbol n$ is the unit vector perpendicular to the plane of the motion.
The incompressibility condition implies $\nabla^2\p... | g16927 | [
0.04902978986501694,
-0.022710226476192474,
0.021848760545253754,
-0.006961701903492212,
0.04932701215147972,
-0.001821456360630691,
-0.024674564599990845,
-0.018302559852600098,
-0.0326722078025341,
0.004148819483816624,
0.001728604780510068,
0.04559054970741272,
-0.02506442554295063,
0.0... |
<p>Imagine you put a tea bag in a cup and half fill it with boiling water. Then after one minute you take the tea bag out and then fill the cup up to fill with hot water. Will the tea be weaker than if you had filled the water up to the normal level with boiling water in the first place and then left it for one minute... | g16928 | [
0.0011601081350818276,
0.02146623469889164,
0.01348908245563507,
0.008528212085366249,
-0.010298147797584534,
0.0013982013333588839,
0.029258865863084793,
-0.004192945081740618,
-0.04598802328109741,
-0.011980440467596054,
-0.029410470277071,
-0.0663834810256958,
-0.02398071438074112,
0.07... |
<p>A book about the <a href="http://en.wikipedia.org/wiki/Bohr%E2%80%93Einstein_debates" rel="nofollow">Bohr-Einstein debate</a>?</p>
<p>Is there any book that details the correspondence between the two? The only books I could find are popular science books, I wonder if there is a book that lists the correspondence in... | g16929 | [
0.032601937651634216,
0.00873182900249958,
0.028483431786298752,
-0.022400541231036186,
-0.00020246054918970913,
0.018935343250632286,
-0.026740124449133873,
-0.00011128852929687127,
-0.0030729244463145733,
0.0028503569774329662,
0.08299514651298523,
-0.022923966869711876,
0.0467161461710929... |
<p>I have expressed my self in a detailed way. I've labeled the points to which I want an answer. </p>
<hr>
<p>I have doubt in the Einstein's rail experiments which he mentioned in his <a href="http://books.google.co.in/books?id=x49nkF7HYncC&redir_esc=y" rel="nofollow">book</a>.<br>
In this experiment we preassu... | g16930 | [
0.008961307816207409,
0.023105349391698837,
0.014540594071149826,
0.007806604728102684,
0.052848976105451584,
0.021997814998030663,
0.09082373231649399,
0.03911111131310463,
-0.013882785104215145,
-0.022369572892785072,
-0.028946345672011375,
-0.005440532695502043,
0.05751163884997368,
-0.... |
<p>If radiation pressure is a pressure exerted upon any surface exposed to electromagnetic radiation then why do planets such as the ones in our solar system maintain consistent orbits? I'm guessing the pressure must be very slight but in the vacuum of space wouldn't even the slightest pressure effect the consistency o... | g16931 | [
0.02494768425822258,
0.02353963442146778,
0.009264232590794563,
-0.006499773822724819,
0.06055270507931709,
0.04887257516384125,
-0.03337331488728523,
-0.015256580896675587,
0.006813430693000555,
0.00451095262542367,
0.04329488053917885,
0.05409980192780495,
0.006195416208356619,
-0.003501... |
<p>There are two objects m1 and m2 connected by a spring and a viscous damper (e.g car body and wheel connected by spring)
From wiki: $\zeta ={c \over 2{\sqrt {mk}}}$</p>
<p>ζ is damping ratio,</p>
<p>c is damping coefficient,</p>
<p>k is spring constant</p>
<p>In wiki example, there is only one mass connected to ... | g16932 | [
0.06674201041460037,
-0.07130083441734314,
-0.0054967040196061134,
-0.010881363414227962,
0.05282874032855034,
-0.03806215152144432,
0.03465414419770241,
0.038643646985292435,
-0.0817718654870987,
0.034607045352458954,
-0.031119326129555702,
-0.02083107829093933,
-0.005928458645939827,
0.0... |
<p>Is it true that the field strength $F_{\mu\nu}$ in a non-Abelian gauge theory with gauge group $G$ vanishes if, and only if, the gauge field $A_{\mu}$ is a pure gauge?</p>
<p>I can show one implication. </p>
<p>If $A_{\mu}=\frac{i}{g}U\partial_{\mu}U^{\dagger}$ where $U \in G$, then the field strength vanishes, bu... | g16933 | [
0.006847823038697243,
0.018948083743453026,
-0.006927903741598129,
-0.0020360944326967,
0.05875628441572189,
0.017964880913496017,
0.02799754962325096,
0.01230948232114315,
0.021322190761566162,
0.018967963755130768,
0.002055197022855282,
-0.03690781816840172,
-0.047720182687044144,
0.0039... |
<p>We have a homogeneous body that looks like this: </p>
<p><img src="http://i.stack.imgur.com/j9fuR.jpg" alt="Homogeneous body"></p>
<p>I have tried dividing the body into different parts using the following definition:</p>
<p><strong>R</strong> g * <strong>A</strong> = <strong>R</strong> 1 * <strong>A</strong> 1 +... | g16934 | [
0.07310531288385391,
0.02427683211863041,
-0.02146572433412075,
-0.0415983572602272,
0.06295416504144669,
0.002520910697057843,
-0.020719999447464943,
0.0632699504494667,
-0.005319965071976185,
-0.014423512853682041,
-0.027257053181529045,
-0.005543607287108898,
-0.0015465799951925874,
-0.... |
<p>Is there evidence of dark matter in our galaxy?</p>
<p>How can we measure this, say, how many percent of the center of our galaxy is dark matter?</p>
<p>I did not find the answer in the question <a href="http://astronomy.stackexchange.com/questions/308/whats-dark-matter-and-who-discovered-it">What's Dark Matter an... | g16935 | [
0.014109943993389606,
-0.01793079823255539,
0.0023127056192606688,
-0.08147501200437546,
0.07934020459651947,
0.009341508150100708,
-0.04274694249033928,
-0.006132079288363457,
0.023978127166628838,
-0.025980288162827492,
0.0300567839294672,
0.027408422902226448,
0.017125649377703667,
-0.0... |
<p>What type of commercial amateur telescope and what method (<em>difference imaging</em>,...) did he use for identifying the supernova?</p> | g16936 | [
-0.0011613910319283605,
0.000988492858596146,
0.009744384326040745,
-0.022063545882701874,
0.023183980956673622,
-0.014552915468811989,
0.013983003795146942,
-0.055702898651361465,
0.06278610229492188,
-0.04512975737452507,
-0.01654563844203949,
0.052582431584596634,
0.07916203886270523,
0... |
<p>Some suggest that if a human was born and raised in a gravity-less environment their bone structure/strength would be different that for children born on earth. If this is the case do you think this change would be gradual (over several generations) or would it be immediate? Also would these changes be permanent in ... | g16937 | [
0.06002458930015564,
0.034300051629543304,
0.002247914904728532,
0.029789267107844353,
-0.048511628061532974,
0.08025060594081879,
0.07752345502376556,
0.028291070833802223,
-0.05479242652654648,
-0.00513927498832345,
-0.03972065448760986,
0.013127371668815613,
-0.04006750136613846,
-0.022... |
<p>Since Jupiter and Saturn's moons are composed of a rock+ice mix. For example, Callisto is 50% rock and 50% ice. When the Sun finally goes red giant, could it melt a significant portion of the 50% of Callisto that is ice? And over what timescale?</p> | g16938 | [
0.005752366501837969,
0.08323170244693756,
-0.0021455513779073954,
0.013553244061768055,
-0.0040464336052536964,
-0.02499692142009735,
-0.03603219985961914,
-0.007729652337729931,
0.033194709569215775,
0.04626857489347458,
-0.020994804799556732,
0.03833440691232681,
0.03516223654150963,
-0... |
<p>Is it possible to dimensionally regularize an amplitude which contains the totally antisymmetric Levi-Civita tensor $\epsilon^{\mu\nu\alpha\beta}$? </p>
<p>I don't know if it's possible to define
$\epsilon^{\mu\nu\alpha\beta}$ in e.g. $$d-\eta$$-dimensions where $\eta$ is considered small and which we set to zero ... | g16939 | [
0.01572694443166256,
0.01814468950033188,
0.007768236566334963,
-0.0467812642455101,
0.022369444370269775,
-0.030481334775686264,
0.03982198238372803,
0.012110929936170578,
-0.052816733717918396,
-0.021584711968898773,
-0.026722973212599754,
0.021480003371834755,
0.0005828799330629408,
0.0... |
<p>If I have a rectangular loop moving through a magnetic field, which way will it go?</p>
<p>A uniform magnetic field (say it's pointing into the page)
A square/rectangular loop of wire moving into the field from left to right with constant speed.</p>
<p>The induced current should be counterclockwise right?</p> | g16940 | [
0.04133718088269234,
0.022089846432209015,
0.0098488200455904,
-0.04418365657329559,
0.0620875209569931,
0.022516051307320595,
0.036535706371068954,
-0.007567528169602156,
-0.04233645647764206,
-0.055906277149915695,
-0.0362885557115078,
0.02666296437382698,
-0.04320468381047249,
-0.003261... |
<p>I'm getting hung up on this term. In studying <a href="http://en.wikipedia.org/wiki/Supermassive_black_hole" rel="nofollow">SMBHs</a>, I see that <a href="http://en.wikipedia.org/wiki/Velocity_dispersion" rel="nofollow">velocity dispersion</a> strongly correlates with mass. Just what is the velocity dispersion? How ... | g16941 | [
0.015050157904624939,
-0.005250036716461182,
-0.011570611968636513,
-0.01749655231833458,
0.053355105221271515,
-0.03519696742296219,
0.06552164256572723,
0.07441771030426025,
-0.017844954505562782,
-0.051745276898145676,
-0.015088464133441448,
0.02314571850001812,
0.05669736489653587,
0.0... |
<p>I'm not referring to phenomena such as galaxies or clusters but rather, what is the largest discrete celestial body that has been observed in the universe?</p> | g16942 | [
-0.00607640203088522,
0.06128133088350296,
0.016729099676012993,
-0.05485972762107849,
-0.015657572075724602,
-0.018650241196155548,
-0.05803859233856201,
0.01495602261275053,
0.0397503636777401,
-0.07434292882680893,
0.02650429680943489,
-0.065484918653965,
0.0365401990711689,
0.014690120... |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.