question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>I am a bachelor physics student and as an assignment we had to perform measurements on an FT spectroscopy setup. </p>
<p><strong>Context.</strong></p>
<p>Our setup consisted of a Michelson interferometer through which the light of two sources namely a HeNe-laser and a sodium lamp, passed at the same time. The ligh... | g7315 | [
0.01381860300898552,
-0.07737374305725098,
-0.0033767337445169687,
-0.00709938071668148,
0.033584583550691605,
-0.009098519571125507,
-0.01296708919107914,
0.03868813440203667,
-0.03808801248669624,
-0.03615705668926239,
-0.0061148651875555515,
0.03854213282465935,
0.0473535917699337,
0.01... |
<p>I am part of a school project, <a href="http://projectstratos.com/" rel="nofollow">Project Stratos</a> to send a balloon to the edge of space (the closer side :P) and was wondering how you would work out the accent rate of a large balloon (roughly 1m^3 of helium with 100g of mass) and the size of it as it increases ... | g7316 | [
0.004998018033802509,
0.017521999776363373,
0.004315143916755915,
-0.045023318380117416,
-0.003908922895789146,
0.010048569180071354,
0.009574772790074348,
0.047073349356651306,
-0.00872478261590004,
0.03026236593723297,
0.0019240379333496094,
0.08595713973045349,
0.05583992227911949,
0.00... |
<p>Suppose, we have the most simple <a href="http://en.wikipedia.org/wiki/Double_pendulum" rel="nofollow">double pendulum</a>:</p>
<ul>
<li>Both masses are equal.</li>
<li>Both limbs are equal.</li>
<li>No friction.</li>
<li>No driver.</li>
<li>Arbitrary initial conditions (no restriction to low energies)</li>
</ul>
... | g7317 | [
0.05216274783015251,
-0.0009359043906442821,
0.01390662882477045,
-0.007882573641836643,
0.028932034969329834,
0.02957865782082081,
0.048982806503772736,
-0.022979315370321274,
-0.0410461463034153,
-0.020357318222522736,
-0.06910876929759979,
0.004607462789863348,
-0.025972234085202217,
-0... |
<p>I've done a little research but I can't seem to find the answers to these questions in regards to a spinning space station simulating gravity.</p>
<p>1) If we imagine the space station as a hollow doughnut and I'm floating in the center of the tube while the station is stopped what happens when the station starts? ... | g7318 | [
0.003871155669912696,
0.03224678337574005,
-0.0061901528388261795,
0.030681515112519264,
0.01841503567993641,
0.0430247038602829,
0.04260993003845215,
0.02560511790215969,
-0.06255930662155151,
-0.060274772346019745,
-0.05624573305249214,
-0.027131883427500725,
0.021187622100114822,
-0.005... |
<p>Ok, as I understand the expansion of the initial singularity was caused by quantum fluctuations like the ones predicted by the Heisenberg Uncertainty Principle. But how can these fluctuations occur within a singularity? And how can they cause the expansion of that singularity? Or do I have a terrible misunderstan... | g7319 | [
0.059020593762397766,
0.06117160990834236,
0.0011901580728590488,
0.034659042954444885,
0.019231483340263367,
0.08775795996189117,
0.01537054218351841,
0.06113069877028465,
0.008920659311115742,
-0.010960574261844158,
-0.04630216583609581,
-0.024763766676187515,
0.03492124006152153,
0.0187... |
<p>Why is it concluded that the cosmos is expanding at an ever increasing rate when looking further out and therefore further back in time?</p>
<p>Surely, if the time were reversed to play forwards, the conclusion would be that the expansion of the universe is actually deaccelerating, and the need to postulate 'Dark E... | g7320 | [
0.060975734144449234,
0.09573844075202942,
0.0055631655268371105,
-0.03337794914841652,
0.0034591923467814922,
0.02403099462389946,
0.029836289584636688,
0.022012613713741302,
-0.02873636968433857,
-0.032628100365400314,
0.043098632246255875,
-0.0064799124374985695,
0.05116487294435501,
0.... |
<p>Consider the following thought experiment:</p>
<p>Imagine an object of a certain mass density which allows it to float in water. </p>
<p>Now if this object is viewed from a moving frame with high speed, it will look Lorentz contracted hence its density will look greater than the rest density. </p>
<p>So from the ... | g7321 | [
0.029765957966446877,
0.05203493684530258,
0.011275304481387138,
-0.046168651431798935,
0.06672565639019012,
0.021513503044843674,
0.059794891625642776,
0.013190191239118576,
-0.03989255428314209,
-0.06480804830789566,
0.007807476446032524,
0.03847113996744156,
0.06232571229338646,
0.02395... |
<p>In this <a href="http://physics.stackexchange.com/questions/18595/is-decoherence-even-possible-in-anti-de-sitter-space">link</a>, one of the answers contains the statement</p>
<blockquote>
<p>If you examine the space-time near a finite area quantum black hole,
you will see an approximate AdS space.</p>
</blockq... | g7322 | [
-0.005299123469740152,
0.04921192303299904,
-0.0056470902636647224,
-0.0382893942296505,
-0.02092156559228897,
0.012216721661388874,
0.011908634565770626,
0.01428209338337183,
-0.045369621366262436,
0.010700209066271782,
-0.0053909216076135635,
0.05377579107880592,
-0.0071487450040876865,
... |
<p>Barring aside considerations such as heat dissipation, capacitance, etc... (aka any sort of technological issue) what is the fastest speed of a processor?</p>
<p>I am told that at distances of 1 planck length $L =1.616$ x $ 10^{-35}$ m</p>
<p>Heisenberg's uncertainty principle hovers around an error factor of 1. ... | g7323 | [
0.0559808649122715,
0.08848380297422409,
0.01283948589116335,
0.024156510829925537,
0.011272556148469448,
-0.016834696754813194,
0.029229266569018364,
-0.013825115747749805,
-0.04852713271975517,
0.024319730699062347,
-0.011878014542162418,
0.03861015662550926,
-0.06210760027170181,
-0.004... |
<p>I've been looking at the <a href="http://arxiv.org/abs/1303.5076" rel="nofollow">Planck 2013 cosmological parameters</a> paper, trying to update my toy cosmology simulator with the most recent data. Most of the interesting values such as $H_0$, $\Omega_m$, and $\Omega_\Lambda$ can be found in Table 2 on page 12, bu... | g7324 | [
-0.01828232780098915,
0.010100017301738262,
0.007484120782464743,
-0.059988539665937424,
-0.009303230792284012,
0.0031541334465146065,
-0.06440362334251404,
-0.009001655504107475,
-0.08614041656255722,
0.030915113165974617,
0.03599657490849495,
-0.014627602882683277,
0.037313979119062424,
... |
<p>Suppose that I am inside of a moving train. I have a coin in my hand and I am standing still. If I toss this coin straight up, it will fall back into my hand. </p>
<p>Now, suppose that I am on that moving train's roof. Now if I toss the coin straight up, the coin will not land in my hand, rather it will fall toward... | g7325 | [
0.04440285265445709,
0.01724698767066002,
-0.008058243431150913,
-0.014883559197187424,
0.06430715322494507,
0.0771903395652771,
0.05039885640144348,
0.008702067658305168,
-0.08615273982286453,
-0.0674169585108757,
-0.02133071981370449,
0.014558166265487671,
-0.006041394080966711,
-0.02101... |
<p>The relation I was referring to in the title is</p>
<p>$${\Lambda_a}^b= \eta_{ac} {L^c}_d \eta^{db}$$</p>
<p>where ${\Lambda_a}^b$ is the inverse transpose of $L$, the <a href="http://en.wikipedia.org/wiki/Lorentz_transformation" rel="nofollow">Lorentz transformation</a>.</p>
<p>I was wondering about the signifi... | g7326 | [
0.014708052389323711,
0.0156227583065629,
-0.016296258196234703,
-0.08610014617443085,
0.04953137785196304,
0.010359038598835468,
0.02499403804540634,
0.016377147287130356,
-0.024671318009495735,
-0.0009984084172174335,
-0.03284679353237152,
0.00012355517537798733,
0.038182809948921204,
-0... |
<p>In the Lattice Boltzmann method we require (based on mass conservation) that the sum of the distribution functions for a node is equal to the density, i.e.</p>
<p>$$
\sum_i f_i = \rho
$$</p>
<p>But what units do $f_i$ have that make their sum equal to the density, which has units of $kg/m^3$?</p>
<p>I guess it me... | g7327 | [
0.02154739387333393,
0.014014709740877151,
-0.010296435095369816,
-0.007465964648872614,
0.03310726583003998,
-0.023740945383906364,
-0.018211843445897102,
0.0078020221553742886,
-0.0039587425999343395,
0.021582363173365593,
-0.03681570664048195,
0.03468581661581993,
0.03508983924984932,
0... |
<p>If you push massive object it accelerates slowly compared to object which is of same size but less density/mass.</p>
<p>However, all objects do Accelerate at the same rate.</p>
<p><code>F=ma</code>....according to this if gravity is a force than spherical ball made of cotton shouldn't also accelerate toward earth ... | g7328 | [
0.1005682423710823,
0.044309452176094055,
0.03227602317929268,
0.0041135139763355255,
0.0651814267039299,
0.046623148024082184,
0.03316526859998703,
0.005243017338216305,
-0.040627337992191315,
-0.06689663976430893,
0.040081996470689774,
-0.033837199211120605,
0.07237347215414047,
-0.02720... |
<p>Could a device with very thin columns of glass or something that attracts water more be used to pull water up and then release it to drive generator and perhaps add vacuum. </p>
<p>I have been wondering about this on and off for like 8 years.</p> | g7329 | [
-0.04175880178809166,
0.04974941536784172,
0.00337352161295712,
-0.016517456620931625,
-0.005444920156151056,
0.019113710150122643,
-0.02206517942249775,
0.006221364252269268,
-0.046986326575279236,
-0.037132542580366135,
0.01458656881004572,
0.012169921770691872,
0.010207973420619965,
0.0... |
<p>Let's say we have an object lying on a slope, the weight of the object can be divided into two components one horizontal and one vertical. My question is does the weight act only in these two directions or does it spread evenly between the the both components?</p> | g7330 | [
0.053235456347465515,
-0.009043056517839432,
0.0037484061904251575,
0.003978951834142208,
0.05024386942386627,
0.05549483373761177,
0.053518474102020264,
0.044269341975450516,
-0.08184792101383209,
-0.060243602842092514,
-0.008357517421245575,
0.00308131892234087,
-0.004805231001228094,
-0... |
<p>Quite a technical question!</p>
<p>I have measured the Point Spread Function of 100nm fluorescent breads with my Olympus scanning head. I'm two-photon exciting the beads with a wavelength of 800nm and focused in the sample with a 100x with N.A.: 1.4</p>
<p>The theory suggests me the resolution of such a system to ... | g7331 | [
-0.015632690861821175,
-0.010761593468487263,
0.008721553720533848,
0.006757739465683699,
0.024057766422629356,
-0.033699993044137955,
-0.026214469224214554,
-0.021007217466831207,
-0.01539493165910244,
-0.0250229611992836,
-0.027769137173891068,
0.08901110291481018,
0.01767200231552124,
-... |
<blockquote>
<p>A gold nucleus is 460 fm (1 fm = 10^(-15) m) from a proton, which initially is at rest. When the proton is released, it speeds away because of the repulsion that it experiences due to the charge on the gold nucleus. What is the proton's speed a large distance (assume to be infinity) from the gold nucl... | g7332 | [
0.05522110313177109,
0.059300292283296585,
0.015227378346025944,
-0.06509162485599518,
0.08351776748895645,
-0.030584629625082016,
-0.016972357407212257,
0.0626203715801239,
-0.02963540330529213,
-0.016942447051405907,
-0.031126290559768677,
0.050207529217004776,
-0.023258280009031296,
-0.... |
<p>In classical mechanics, we had Newton's law of gravity $F \propto \frac{Mm}{r^2}$. Because of this, all laws of classical electrostatics applied to classical gravity if we assumed that all charges attracted each other due to Coulomb's law being analogous. We can "tweak" classical electrostatics to fit gravity.</p>... | g247 | [
0.0155928460881114,
0.009549484588205814,
-0.004515873268246651,
-0.006203384138643742,
0.06218985840678215,
0.05403441563248634,
0.029668517410755157,
0.025157945230603218,
-0.07619582116603851,
0.018171660602092743,
0.01593679003417492,
-0.04459826648235321,
0.023272279649972916,
0.00730... |
<p>Gravity is inversely proportional to the <em>distance</em> between objects.</p>
<p>Do we use Euclidean distance or the invariant interval for that distance?</p>
<p>Using the invariant interval makes everything a bit more complex: An object that is one lightyear away, is also one year "younger" when we observe it. ... | g7333 | [
0.02221064455807209,
0.009680435992777348,
-0.006712805479764938,
-0.01359265111386776,
-0.03412920609116554,
0.05744120851159096,
0.07625172287225723,
0.049416545778512955,
-0.07021316885948181,
-0.03111143223941326,
0.04343106597661972,
0.007309251464903355,
0.0524839386343956,
-0.035593... |
<p>Suppose initially I have a uniform magnetic field.</p>
<p>Now, in this formerly-uniform magnetic field, I place an un-magnetised cylindrical body of iron into this field of known dimension, with the axis of rotation aligned with the (formerly uniform) magnetic field.</p>
<p>How would one go about mathematically de... | g7334 | [
0.020030885934829712,
-0.0025058020837605,
-0.01541109662503004,
-0.029533198103308678,
0.047972362488508224,
-0.014271238818764687,
0.04516072943806648,
0.02055266685783863,
-0.0538153275847435,
0.023176807910203934,
-0.07707180082798004,
0.04058718681335449,
0.011931431479752064,
-0.0662... |
<p>Specifically, it is a one-dimensional wave equation for waves on a string with a non-constant cross-section, i. e. $$S(x)=S_1+S_2 \cos{2x}; \qquad c(x)=\sqrt{F/\rho\, S(x)}.$$ Separating the variables yields the Mathieu differential equation $$\frac{d^2y}{dx^2}+[a-2q\cos (2x) ]y=0,$$ $a$ and $q$ are parameters of th... | g7335 | [
0.00548451766371727,
-0.07230515033006668,
0.002120833843946457,
-0.08893445879220963,
0.034306831657886505,
0.0023450744338333607,
0.019495995715260506,
-0.008876591920852661,
0.036150604486465454,
-0.015169917605817318,
-0.05976911634206772,
0.034130536019802094,
-0.01478795800358057,
-0... |
<p>I'm not the brightest person and I was wondering if it was possible, in the same way that it's possible to make ink that's visible under UV light, if it's possible to make ink that requires a distinct combination of colours of light to work. If there are different coloured UV lights would it be possible to make an ... | g7336 | [
-0.02628444880247116,
0.002580150729045272,
0.0361127071082592,
-0.024689828976988792,
0.0019255662336945534,
0.00044860775233246386,
-0.05465986952185631,
0.018056103959679604,
0.00478648254647851,
-0.039801839739084244,
0.05543309077620506,
-0.022307274863123894,
0.023830020800232887,
0.... |
<p>Speed of sound is related to the derivative of pressure with respect to density:</p>
<p>$v_s=\sqrt{(\frac{\partial P}{\partial \rho})_S}$</p>
<p>where S tells us the derivative must be taken while keeping entropy constant.</p>
<p>For an ideal Bose gas, $P$ and $\rho$ can be expressed in terms of Bose-Einstein fun... | g7337 | [
0.012298975139856339,
-0.028017867356538773,
-0.02101139910519123,
-0.035200685262680054,
0.0826575979590416,
-0.004848476964980364,
0.047531962394714355,
0.008311301469802856,
-0.07830903679132462,
0.028905797749757767,
0.006577136926352978,
0.034528449177742004,
-0.008117200806736946,
0.... |
<p>I'm referring to <em>"Path integral approach to birth-death processes on a lattice"</em>, L. Peliti, J. Physique 46, 1469-1483 (1985), available at: <a href="http://people.na.infn.it/~peliti/path.pdf">http://people.na.infn.it/~peliti/path.pdf</a></p>
<p>The article is about a reformulation of the master equation fo... | g7338 | [
0.023266058415174484,
-0.022565899416804314,
-0.005652586929500103,
-0.0023681435268372297,
-0.015359500423073769,
-0.03402091562747955,
-0.01481866929680109,
0.03892087936401367,
-0.0183212049305439,
0.05756138265132904,
-0.018900321796536446,
0.008968884125351906,
0.02450680173933506,
0.... |
<p>I know developments in physics and mathematics often nourish each other, and at different points in history, physics and math have taken turns leading each other. An example of a physicist "inventing" the required mathematics is Newton and his calculus. At other times, the mathematics have been discovered as a curio... | g7339 | [
0.06728365272283554,
0.030973557382822037,
0.021431582048535347,
0.0016232100315392017,
0.04343506693840027,
0.0411575622856617,
0.00320053705945611,
-0.047523993998765945,
0.021053243428468704,
-0.0654691681265831,
0.027357948943972588,
0.0017569465562701225,
0.023486044257879257,
-0.0246... |
<p>Okay, first off, I know that there is a very similar problem about statically indeterminate trusses <a href="http://physics.stackexchange.com/questions/44310/solving-a-statically-indeterminate-truss">here</a>, but my problem was a bit different and I didn't know how to adapt the answer for that problem to mine.</p>
... | g7340 | [
0.06270512193441391,
0.04064323380589485,
0.004967829212546349,
-0.010833196341991425,
0.025095408782362938,
-0.06617855280637741,
-0.035515815019607544,
0.009562108665704727,
-0.038960568606853485,
-0.019907711073756218,
-0.03600040078163147,
0.0299838837236166,
-0.0753486305475235,
-0.02... |
<p>I have a doubt, say when a body moves in a circular loop, there are basically two types of acceleration acting on the object. One is the linear acceleration which is basically tangent to the circle, and there is an acceleration that acts inward which is basically centripetal acceleration. These two acceleration vect... | g7341 | [
0.04688890650868416,
0.023935891687870026,
0.017113246023654938,
0.006884633097797632,
0.07540996372699738,
0.06940563023090363,
0.0612780898809433,
0.01624223217368126,
-0.05963204801082611,
-0.057347070425748825,
0.021440546959638596,
-0.04048037528991699,
0.008471351116895676,
-0.011934... |
<p>I had to do a problem, and part of it was to find the mechanical energy of satellite orbiting around mars, and I had all of the information I needed. I thought the total mechanical energy would be the kinetic energy+ the potential energy, or $KE+PE$. However, I had the answer sheet and it said that I had to do $KE-P... | g7342 | [
0.020929748192429543,
0.07812421768903732,
-0.008453959599137306,
0.025975095108151436,
-0.01450116652995348,
0.033606644719839096,
-0.0074002002365887165,
0.004972991067916155,
-0.08223503082990646,
-0.0032484722323715687,
0.03865831717848778,
-0.0034952478017657995,
0.024583591148257256,
... |
<p>The equation for the photon propagator is straightforward
$$
D_{ij} = \langle 0 |T \{ A_{i}(x')A_{j}(x) \}|0 \rangle
$$
However, $A_{i}(x)$ is gauge-dependent and therefore unphysical (in the arguable sense). Then, since the propagator is dependent on the vector potential, the propagator is unphysical. Sadly, my w... | g7343 | [
-0.01394240278750658,
0.009688380174338818,
-0.0023978527169674635,
-0.007086493540555239,
-0.021146735176444054,
0.010160893201828003,
0.09024716913700104,
0.050043657422065735,
-0.003180063795298338,
-0.03082958236336708,
0.040638793259859085,
-0.008045780472457409,
0.045318033546209335,
... |
<p>These ideas/questions probably represent a lack of understanding on my part,
but here they are:</p>
<p>1) Cosmologists talk about the increasing speed of expansion of the universe and talk of dark energy as the cause. But, I keep thinking that the farther out we observe, is farther back in time and the light we ob... | g7344 | [
0.03891047462821007,
0.03175482526421547,
0.02644907496869564,
-0.0040486156940460205,
0.028275594115257263,
0.008510577492415905,
0.053730081766843796,
0.02560516633093357,
-0.020833132788538933,
-0.045764412730932236,
0.06707648932933807,
-0.023112302646040916,
0.05611306428909302,
0.058... |
<p>I'm having a bit of a slow day, and can't see how to do the following integral in Peskin and Schroeder (page 107 for anyone with the book). We've derived in the centre of mass frame the integral over 2 body phase space</p>
<p>$$\int d\Pi_2 =\int \frac{dp_1p_1^2d\Omega}{(2\pi)^3)2E_12E_2}(2\pi)\delta(E_{cm}-E_1-E_2)... | g7345 | [
0.04242131486535072,
-0.007121967617422342,
-0.007969407364726067,
-0.05035216361284256,
0.02319379150867462,
0.04424766078591347,
0.06911153346300125,
0.060486700385808945,
-0.07272359728813171,
0.001977213891223073,
-0.03640897199511528,
0.001063830335624516,
0.029079454019665718,
0.0026... |
<p>Criteria for thermodynamical stability is the convex of entropy. But for black hole entropy is non-additive. </p> | g7346 | [
-0.0027302519883960485,
0.004262566566467285,
0.013614906929433346,
-0.02677185647189617,
0.045674946159124374,
-0.02257169783115387,
-0.030204784125089645,
-0.036658793687820435,
-0.028657546266913414,
-0.0084142554551363,
0.005761450156569481,
0.0219133123755455,
0.011665455996990204,
0.... |
<p>Suppose someone tells me what constellation the Sun, Moon, Mercury,
Venus, Mars, Jupiter, and Saturn were in when they were born, and the
information is astronomically accurate (ie, not astrological signs).</p>
<p>Could I use this information to estimate their date of birth
(including year) to a reasonable approxim... | g7347 | [
-0.049036405980587006,
0.031444571912288666,
-0.00046579245827160776,
-0.029505059123039246,
-0.04836728423833847,
-0.001489597256295383,
-0.003713955171406269,
-0.010517816059291363,
0.05951034650206566,
-0.0065290960483253,
0.0290293637663126,
0.01404351182281971,
0.06850683689117432,
0.... |
<p>Is the structure of the periodic table fundamental enough that other forms of intelligent life would likely structure their own listing of the elements in the same way (i.e. are there other ways of arranging the periodic table (in 2D) which would be equally useful, or is the current structure the most efficient way ... | g7348 | [
-0.006644188426434994,
0.019414745271205902,
0.008656181395053864,
-0.043327897787094116,
0.0171553622931242,
0.01153609063476324,
-0.020961491391062737,
-0.05351630598306656,
0.002579444320872426,
-0.004122000187635422,
0.05465017259120941,
0.0038201785646378994,
0.018742941319942474,
-0.... |
<p>It makes intuitive sense to me for the apparent frequency of a sound as modified by the Doppler effect to be based entirely on the speed at which the observer and the source get closer or farther apart, regardless of whether the source or the observer is moving, based on the principle of relativity. However, the gen... | g7349 | [
-0.001177977304905653,
0.00807271059602499,
-0.002664426574483514,
0.0005323143559508026,
0.027960272505879402,
-0.022402657195925713,
0.03256390988826752,
0.02867909148335457,
-0.019161352887749672,
-0.014259040355682373,
0.011896451003849506,
-0.015117700211703777,
0.05477698892354965,
0... |
<p>What causes humans to emit infra red radiation and why don't we also emit other types of electromagnetic radiation such as ultra violet or microwave? Sunlight contains UV and our body takes it in, but when we give off radiation, do we not radiate it back? </p>
<p>I know that the constant motion of molecules embodie... | g7350 | [
0.027239207178354263,
0.024395544081926346,
0.023013243451714516,
0.05777493119239807,
-0.016474373638629913,
0.029424501582980156,
-0.009088443592190742,
0.0253298282623291,
-0.008942346088588238,
-0.027941172942519188,
0.020491434261202812,
0.040728189051151276,
0.04025598615407944,
0.01... |
<p>I wonder if there is a certain amount of weight that I could carry in a rolling bag to help prevent me from being knocked over by the wind. I have balance problems and some lack of muscle strength in my legs and sometimes it feels like strong wind gusts here in Boston, MA may knock me over, especially when I walk in... | g7351 | [
-0.02209540829062462,
-0.0026977392844855785,
0.021623393520712852,
-0.011219278909265995,
-0.0411013588309288,
0.08252289146184921,
0.015591317787766457,
0.03724328801035881,
-0.06287869065999985,
0.0006516819703392684,
0.0029197148978710175,
-0.07207189500331879,
-0.006714235059916973,
0... |
<p>What is the <strong>physical meaning</strong> of the kinetic term in the classical scalar field Lagrangian $$\mathcal{L}_{kin}~=~\frac{1}{2}(\partial_\mu\phi)(\partial^\mu\phi)~?$$ It gives how does the field change from one space-time point to the other. Right? What is the significance of the relative minus sign be... | g7352 | [
0.03181583434343338,
-0.004950250498950481,
-0.02190869115293026,
-0.01880802772939205,
0.05559907481074333,
0.04238102212548256,
0.06808285415172577,
0.06685509532690048,
-0.03685309737920761,
0.007502657826989889,
-0.030765313655138016,
0.054918598383665085,
0.04988323524594307,
0.008462... |
<p>So few days ago I came across this new tool for smart phones <a href="http://www.consumerphysics.com/myscio/" rel="nofollow">http://www.consumerphysics.com/myscio/</a>. It says it uses NIR spectroscopy, which I don't know lot about. My question is: <strong>Is it possible for such a small device (73x25x16.5 mm) to be... | g7353 | [
0.010397090576589108,
0.013392500579357147,
0.013395833782851696,
0.021647829562425613,
0.018244709819555283,
-0.04678530991077423,
-0.04074035957455635,
-0.06446264684200287,
-0.013543318957090378,
-0.01842605136334896,
0.003155858488753438,
0.0038635197561234236,
0.018461622297763824,
-0... |
<p>The following functional derivative holds:
\begin{align}
\frac{\delta q(t)}{\delta q(t')} ~=~ \delta(t-t')
\end{align}
and
\begin{align}
\frac{\delta \dot{q}(t)}{\delta q(t')} ~=~ \delta'(t-t')
\end{align}
where $'$ is $d/dt$.</p>
<p>Question: What is
\begin{align}
\frac{\delta q(t)}{\delta \dot{q}(t')}?
\end{alig... | g7354 | [
0.08133605122566223,
-0.03321044147014618,
-0.0013641209807246923,
-0.07612700015306473,
0.05473022907972336,
0.023916929960250854,
0.07934132218360901,
0.00864524394273758,
-0.053387582302093506,
-0.03076034225523472,
-0.04092356190085411,
0.04966777563095093,
0.03416254371404648,
-0.0146... |
<p>I've read that the faster you travel in space, the slower you travel in time.
And when you reach the speed of light (which we won't be able to) time will stand still.
So when light travels at the speed of light, it doesn't move in time, so no time will have past when the light arrives at it's "destination". Right?<... | g195 | [
0.005886953789740801,
0.07385434210300446,
0.021537285298109055,
0.03243827447295189,
0.003099750494584441,
-0.013643449172377586,
0.05015168339014053,
0.023886678740382195,
-0.040695786476135254,
-0.02958582155406475,
0.011775919236242771,
-0.03215577453374863,
0.029308363795280457,
-0.04... |
<p>If the second and third matter families (so-called generations: muon, muon neutrino, tau, tau neutrino, ...) didn't exist, would that affect how the universe runs? Are they optional or required?</p> | g7355 | [
-0.04018907994031906,
0.008181151002645493,
0.022744709625840187,
-0.030591873452067375,
0.046694282442331314,
0.039172351360321045,
-0.0659138560295105,
-0.003704106668010354,
-0.023548534139990807,
-0.05661087855696678,
-0.002372888382524252,
-0.02237028442323208,
-0.011283278465270996,
... |
<p>Today, I was tutoring and explained the space-time. I explained how one can convert North-South into West-East by rotating, and how you can convert time into space with velocity.</p>
<p>Below the Energy-Momentum stuff the book had some problems. One was the following:</p>
<blockquote>
<p>Given an event at (1 Lig... | g7356 | [
0.047267746180295944,
0.012396667152643204,
-0.0053825075738132,
-0.04625871777534485,
0.0498315654695034,
-0.028554357588291168,
0.04095606505870819,
0.000084903251263313,
-0.045284196734428406,
0.013550917617976665,
0.05600401386618614,
-0.017158232629299164,
0.0730067789554596,
0.019077... |
<p>According to <a href="http://en.wikipedia.org/wiki/Density_matrix#Pure_and_mixed_states" rel="nofollow">Wikipedia</a>, if a system has $50\%$ chance to be in state $\left|\psi_1\right>$ and $50\%$ to be in state $\left|\psi_2\right>$, then this is a mixed state.</p>
<p>Now consider state $\left|\Psi\right>... | g7357 | [
0.041670672595500946,
-0.006818352732807398,
-0.005723038222640753,
-0.04571138694882393,
-0.01434353832155466,
0.013840037398040295,
0.0736716091632843,
0.0405503548681736,
0.01400470919907093,
-0.04445677623152733,
0.00117046560626477,
-0.05267368629574776,
0.005010910797864199,
-0.00835... |
<p>I'm curious what will happen if we 'drive' a car with (almost) the speed of light, and all of sudden we switch the car headlights on? Will the car headlights ray have double speed (speed of 600.000km/h) or that ray will never be seen?</p> | g109 | [
0.01403126772493124,
0.014859936200082302,
0.002850242890417576,
0.03616759181022644,
0.027754168957471848,
-0.08988155424594879,
0.004093455150723457,
0.040989041328430176,
-0.016072653234004974,
0.03799901530146599,
0.01678389310836792,
0.04744300618767738,
0.013884604908525944,
-0.06491... |
<p>Why is the Dirac operator considered so important - in both physics and (pure) mathematics?</p> | g7358 | [
0.020767219364643097,
0.05007423087954521,
-0.01399847399443388,
0.026936382055282593,
0.0400005541741848,
-0.012722909450531006,
0.0652991235256195,
0.01767350174486637,
0.001495344447903335,
-0.059453751891851425,
-0.04722440242767334,
-0.027055812999606133,
0.013096346519887447,
0.04831... |
<p>Given the energy momentum tensor in E&M:
$T_{\mu\nu} = -F_{\mu\alpha} g^{\alpha \beta} F_{\beta \nu} +\frac{1}{4} g_{\mu \nu} F_{\sigma \alpha} g^{\alpha \beta} F_{\beta \rho} g^{\rho \sigma}$
I want to show it is homogenous and isotropic in Robertson-Walker spacetime. How would you go about performing a rotatio... | g7359 | [
0.0023587862960994244,
-0.029425418004393578,
-0.028307469561696053,
-0.06077625975012779,
0.027249738574028015,
0.026159742847085,
0.051662031561136246,
0.01965678110718727,
-0.054282158613204956,
0.03625278174877167,
0.03205687925219536,
-0.03196445852518082,
-0.03672785311937332,
0.0126... |
<p>I have been trying to understand Einstein's principle of relativity for quite some time. I have at least I believe, understood the notion that time is relative and can actually 'change' relative to some frame of reference close to c. My question is, time is actually a variable that we invented based on how we though... | g117 | [
0.005276625044643879,
0.054306939244270325,
-0.007219791878014803,
-0.03948764503002167,
-0.04227948561310768,
0.01679147779941559,
0.06890616565942764,
0.008090924471616745,
-0.03669709712266922,
0.004088584333658218,
-0.0150978434830904,
-0.0019023875938728452,
0.06199195981025696,
-0.01... |
<p>This is a very trivial question, but I can't seem to reason it out, again, as to why charges gather at points and edges.</p> | g7360 | [
0.09441302716732025,
0.014234572649002075,
-0.015522719360888004,
0.010748128406703472,
0.1189311072230339,
0.022820334881544113,
0.02691805176436901,
-0.022696245461702347,
-0.043752897530794144,
0.0005720937624573708,
-0.039551522582769394,
0.049515921622514725,
0.040794286876916885,
0.0... |
<p>Today in an engineering thermodynamics lecture, the professor gave an example of a gas doing work. We had a cylinder full of helium at a pressure of something like 200 kPa absolute and the valve was opened so that the gas would flow out against the atmospheric pressure until the pressures were equal. Also the cylind... | g7361 | [
0.03957267850637436,
-0.015835260972380638,
0.02469645068049431,
0.0008849006844684482,
-0.01897873356938362,
0.05785655975341797,
0.019933322444558144,
-0.01615823432803154,
-0.08109000325202942,
-0.0011004088446497917,
0.010642915964126587,
0.025980735197663307,
0.01764686591923237,
0.01... |
<p>Every once in a while, we get a question asking for a book or other educational reference on a particular topic at a particular level. This is a meta-question that collects all those links together. If you're looking for book recommendations, this is probably the place to start.</p>
<p>All the questions linked belo... | g98 | [
0.013923545368015766,
0.032715603709220886,
0.0053242044523358345,
-0.03366818651556969,
0.039470382034778595,
0.0314275324344635,
0.00045281415805220604,
0.014073163270950317,
-0.013483472168445587,
0.008136806078255177,
0.03697654977440834,
-0.017126798629760742,
0.008668212220072746,
0.... |
<p>Many of us may remember the problems from thermodynamics where we had to determine if a pretend air conditioning unit supplier's claims violated the 2nd law. I want to pose a similar question regarding a new "green" Air Conditioning (AC) technology.</p>
<p>An ice energy storage unit for AC works by making ice duri... | g7362 | [
0.025484245270490646,
0.035704031586647034,
0.017237357795238495,
0.07336791604757309,
-0.031114542856812477,
0.0036570485681295395,
0.03433915600180626,
-0.014152727089822292,
-0.05937373265624046,
0.0342167429625988,
0.024457812309265137,
-0.00112766248639673,
-0.020448924973607063,
-0.0... |
<p>What is meant by a cyclic rotation of a matrix, specifically in proving that j*k-k*j=i*l
where j,k,l are cyclic rotations of the Pauli spin matrices sigma x, sigma y, and sigma z</p> | g7363 | [
-0.009400791488587856,
0.018811119720339775,
-0.013062164187431335,
-0.012172820046544075,
0.0119556849822402,
-0.08500929176807404,
0.06255079060792923,
-0.024202600121498108,
0.008995025418698788,
0.038048155605793,
-0.038533445447683334,
0.046614039689302444,
-0.0035929197911173105,
-0.... |
<p>The Kolmogorov theory of turbulence indicates an energy cascade in turbulence. Is there a corresponding version of relativistic fluid?</p> | g7364 | [
0.014687062241137028,
-0.017821526154875755,
0.008806859143078327,
0.002768562640994787,
0.025653716176748276,
0.02772507630288601,
-0.018166249617934227,
0.07084222137928009,
-0.0024258845951408148,
0.015843812376260757,
-0.0018386823358014226,
0.01333559863269329,
0.003457049373537302,
0... |
<p>Suppose you do a Stern-Gerlach experiment with atoms in a $j=1$ state. There would be three separate beams ($m_j = -1, 0, 1$) coming out of the apperatus. But what would be the relative distribution of atoms in these beams?</p>
<p>On first thought I would say that the distribution should be $\frac{1}{3}$, $\frac{1}... | g7365 | [
0.017710229381918907,
0.016176020726561546,
0.013695752248167992,
-0.04449746757745743,
0.026217181235551834,
0.014720278792083263,
0.00029608962358906865,
0.02244463935494423,
0.03916142135858536,
-0.004139258060604334,
0.009885958395898342,
-0.01633542962372303,
0.01311852503567934,
0.00... |
<p>If we know a function $f(\phi, \theta)$ in $\mathbb R^3$ only over a convex surface (which for simplicity let's assume a sphere of radius $r$), is there any measure for the degree of anisotropy over this surface? That is, given two functions, $f_1, f_2$ is there any objective measure $A(f)$ where we can make qualita... | g7366 | [
0.012755177915096283,
-0.008279900997877121,
-0.009405095130205154,
-0.047759048640728,
0.022191952913999557,
0.015233010053634644,
0.024010110646486282,
-0.023456012830138206,
0.013392951339483261,
0.003736307378858328,
-0.028778670355677605,
0.003101455746218562,
0.01455368846654892,
-0.... |
<p>I am trying to understand <a href="http://en.wikipedia.org/wiki/Coherent_states">coherent states</a>. As far as I could find there are three equivalent definitions and in general many sources start from a different one, still I fail to see their equivalence. I restate the definitions and their equivalences given in ... | g339 | [
0.03145752102136612,
-0.023884791880846024,
0.0037922728806734085,
0.013077592477202415,
-0.008857538923621178,
0.04046306386590004,
0.004129679873585701,
0.05375603586435318,
0.021103667095303535,
-0.042547088116407394,
0.002761789131909609,
-0.08165988326072693,
0.034310758113861084,
0.0... |
<blockquote>
<p>A 9.5 kg block (A) is traveling in the positive x-direction with a speed of 3.0 m/s. At some point, it explodes and breaks into two pieces. After the explosion, block C, which is 6.0 kg, moves off in the negative y-direction, and block B, which is 3.5 kg, moves off at an angle 35° with respect to the ... | g7367 | [
0.06359344720840454,
0.007626453880220652,
0.019978957250714302,
0.025291331112384796,
0.05379864200949669,
-0.02867567166686058,
0.006476385518908501,
0.037178050726652145,
-0.0037560327909886837,
-0.0021331491880118847,
-0.020271161571145058,
-0.027335230261087418,
0.001478145713917911,
... |
<p>Do the full inhomogeneous Maxwell equations obey parity (P) and time reversal (T) symmetry separately or only the full CPT symmetry?</p>
<p>I believe the homogeneous Maxwell equations obey parity and time reversal symmetry separately - is that right? The homogeneous Maxwell equations reduce to a wave equation in wh... | g7368 | [
0.014593759551644325,
-0.009927467443048954,
-0.021105771884322166,
0.02937542088329792,
0.10936034470796585,
0.017897240817546844,
0.08024052530527115,
0.055385690182447433,
-0.03682578355073929,
0.02641696110367775,
-0.044237107038497925,
0.03570747375488281,
-0.04002520069479942,
0.0011... |
<p>Recently I am reading Di Francesco's book Volume I on Conformal Field Theory. In order to reduce the number of fields in a correlator, the calculation of Operator Algebra is extremely important. To do this, equation (6.175), which is derived from (6.174), is necessary. The author writes in the book below equation 6.... | g7369 | [
0.02863561548292637,
0.0023781443014740944,
-0.007449881639331579,
0.023372385650873184,
0.037153735756874084,
-0.017543962225317955,
0.10468113422393799,
0.04146130755543709,
-0.038052596151828766,
-0.00718205701559782,
-0.06370782107114792,
-0.012319338507950306,
0.022839676588773727,
0.... |
<p>If an electron falls into a black hole. How can the Heisenberg uncertainty principle hold? The electron has fallen into the singularity now so it has a well defined position which means that it doesn't have a well defined momentum? Furthermore, the electron can't have a well defined position in space because space e... | g7370 | [
0.0010777562856674194,
0.01012054830789566,
0.007081517484039068,
0.007157923653721809,
0.06118820235133171,
0.04151539131999016,
0.018737345933914185,
0.047728247940540314,
-0.04422760382294655,
0.003230226458981633,
-0.0264017041772604,
-0.014888106845319271,
0.018854081630706787,
0.0066... |
<p>Who can provide me some elegant solution for </p>
<p>$$\left[\hat{a}^{M},\hat{a}^{\dagger N}\right]\qquad\text{with} \qquad\left[\hat{a},\hat{a}^{\dagger}\right]~=~1$$</p>
<p>other than brute force calculation?</p>
<p>================================================</p>
<p>O lala!!! Thanks for @Prathyush and @Qm... | g7371 | [
-0.0006004436290822923,
-0.062202706933021545,
-0.03312651067972183,
-0.05347185954451561,
0.01924012042582035,
-0.07522053271532059,
0.04067860543727875,
-0.04300834983587265,
0.000003728983301698463,
0.01083221472799778,
0.010134903714060783,
0.03934064880013466,
-0.02206796035170555,
-0... |
<p>Let's say a 10N cube (in air, on Earth) rests flat on a scale at the bottom of a tank of water, and the scale reads 8N, so there is 2N of buoyant force on the cube. How does the buoyant force manifest itself on the cube? I assume the force is normal to the surface of the scale, but if there isn't any water under t... | g7372 | [
-0.013313539326190948,
0.03171134740114212,
0.005522232502698898,
-0.05276684835553169,
0.02282303012907505,
0.0694274753332138,
-0.000689277017954737,
-0.022954944521188736,
-0.058901771903038025,
-0.06564722955226898,
-0.02237042598426342,
0.02332226186990738,
-0.024311263114213943,
-0.0... |
<p>Let $ H = \frac{-h^2}{2m}\frac{\partial^2 }{\partial x^2}$. I want to find the matrix elements of $H$ in position basis. It is written like this:</p>
<p>$\langle x \mid H \mid x' \rangle = \frac{-h^2}{2m}\frac{\partial^2}{\partial x^2} \delta(x -x')$.</p>
<p>How do we get this? are we allowed to do $\langle x | \... | g7373 | [
0.02597087062895298,
-0.027872443199157715,
-0.013660724274814129,
-0.051132723689079285,
0.06419100612401962,
-0.05962817743420601,
0.00956921186298132,
0.01965191215276718,
-0.09349733591079712,
-0.019923070445656776,
0.014833875000476837,
0.031485121697187424,
-0.007707929238677025,
-0.... |
<p>What experiments prove the greenhouse effect? I've read a little on <a href="http://en.wikipedia.org/wiki/Greenhouse_effect" rel="nofollow">wikipedia</a> but I've got only some names but not their experiments.</p> | g710 | [
0.026972882449626923,
0.006400803569704294,
0.015229434706270695,
0.05434694141149521,
0.06929464638233185,
0.0018644698429852724,
0.04671705886721611,
0.04171495512127876,
-0.010239243507385254,
-0.003291687462478876,
-0.023626163601875305,
0.0044001927599310875,
0.007857074029743671,
0.0... |
<p>I know the equations, but I am having difficulties to get the difference between this two concepts, binding energy and adsorption energy.</p> | g7374 | [
0.029283106327056885,
0.02034383825957775,
0.0025474398862570524,
0.023723801597952843,
-0.02664608508348465,
-0.0029768324457108974,
-0.00541817769408226,
0.06437664479017258,
-0.03364456444978714,
-0.0024673675652593374,
0.020778212696313858,
-0.003148547373712063,
-0.016096802428364754,
... |
<blockquote>
<p>Can a liquid insulator be electrically charged by touching a charged
conductor?</p>
</blockquote>
<p>I understand that solid insulator will only be charge on the surface where it is touch, but the case is different from liquid which it circulates, so I imagine that slowly liquid insulator will be f... | g7375 | [
0.04717787727713585,
-0.02376517280936241,
0.024853451177477837,
-0.018468165770173073,
0.005140332039445639,
0.04788217321038246,
0.021934250369668007,
0.03740961477160454,
-0.014016462489962578,
0.014004700817167759,
-0.025952553376555443,
0.05544259771704674,
-0.05014162138104439,
-0.01... |
<p>What is the temperature of objects in Low Earth Orbit?</p>
<p>Consider LEO to be 600km to 800km.</p> | g7376 | [
0.006075975485146046,
0.020654264837503433,
-0.004330238327383995,
-0.018039923161268234,
-0.01014706864953041,
0.019120536744594574,
-0.0736086294054985,
0.027279512956738472,
-0.016724076122045517,
-0.016857935115695,
-0.0036715830210596323,
0.09513988345861435,
0.009953453205525875,
-0.... |
<p>My mind is drawing a blank right now. In systems with spin and orbital angular momentum, I know that rotational invariance implies that $[H, \mathbf{J}]=0$ where $\mathbf J=\mathbf L+\mathbf S$. But I don't see why rotationally invariant systems should necessarily commute with the <em>square</em>-magnitude operato... | g7377 | [
-0.009552561677992344,
-0.0147507693618536,
-0.015036074444651604,
-0.006994729861617088,
0.00849556177854538,
-0.0025048754177987576,
0.047297403216362,
0.03228098899126053,
0.01124818529933691,
0.03382933512330055,
-0.021267404779791832,
-0.0361880287528038,
0.005522001534700394,
-0.0098... |
<p>What is the material for optical focusing that produces the less diffraction losses?</p>
<p>Suppose one have a sequence of serial optical elements $R$ that keep refocusing a beam of collimated light, each a distance $D$. Now suppose that the wavelength $\lambda$, the optical element and the distance are such that t... | g7378 | [
0.055573415011167526,
-0.01975042000412941,
0.022087737917900085,
0.021452631801366806,
-0.030881622806191444,
0.018505079671740532,
0.002084246138110757,
-0.027168426662683487,
0.024641338735818863,
-0.030211469158530235,
0.010565485805273056,
0.07022175937891006,
0.01683085598051548,
-0.... |
<p>I've heard and read that our solar system lies near to the peripheral region of the Galaxy. Then accordingly we would have a greater probability of sustaining to eventual gulping down by the super-massive black hole. But how long ?</p> | g405 | [
0.04985935986042023,
0.04443211108446121,
0.010680650360882282,
-0.006531213875859976,
-0.03791666030883789,
0.011816892772912979,
-0.010930558666586876,
0.06286759674549103,
-0.011154640465974808,
-0.03082922473549843,
0.04737991467118263,
0.03312539681792259,
0.02831638604402542,
0.01397... |
<p>Can the statement be regarded as true? That every particle, or element in the universe can be regarded as a combination of black hole and white hole in variable proportion.</p> | g7379 | [
0.03155875205993652,
-0.0090950857847929,
-0.009471306577324867,
-0.024934174492955208,
0.07005304098129272,
0.007517104968428612,
-0.023226117715239525,
0.01403062418103218,
0.038564521819353104,
0.013123949989676476,
0.05556730180978775,
0.006733034737408161,
-0.016178982332348824,
0.014... |
<p>Can someone explain these 3 concepts into a unified framework.</p>
<ol>
<li><p>Randomness : Randomness as seen in a coin toss, where the system follows known and deterministic (at the length and scale and precision of the experiment) physics but, the complexity allows us to treat the system as random. (i.e we can a... | g7380 | [
0.014168037101626396,
0.010377197526395321,
0.013240435160696507,
-0.02998427301645279,
0.06467287987470627,
0.021821416914463043,
0.042954057455062866,
-0.01032746210694313,
0.03209395706653595,
-0.03249748423695564,
-0.013716762885451317,
0.031084105372428894,
0.03620430454611778,
-0.000... |
<p>When doing physics with two-level systems and introducing rotations, a term that appears quite often is the rotation of a pauli matrix by another one:</p>
<p>$e^{- i \sigma_i \theta/2} \sigma_k e^{i \sigma_i \theta/2}$</p>
<p>The way I know to evaluate this is by using</p>
<p>$\exp(i \sigma_i \theta/2) = I \cos \... | g7381 | [
0.01742614060640335,
0.0628359392285347,
-0.011555862613022327,
-0.05906761437654495,
0.011631720699369907,
-0.050549671053886414,
0.06353353708982468,
-0.009519691579043865,
-0.021633205935359,
0.053318653255701065,
0.010084489360451698,
0.012953154742717743,
0.02215741202235222,
0.028390... |
<p>The trajectory of a cannonball fired from the origin with initial speed $v_0$ at an angle $\theta$ is given by
$$y = x\tan\theta - \frac{g}{2v_0^2 \cos^2\theta}x^2.$$
For fixed $v_0$, at what angle $\theta$ should the canon ball be fired so that it will hit a target located at $(x_0,y_0)$? What is the area of the re... | g7382 | [
0.018051933497190475,
-0.03726380690932274,
-0.008576307445764542,
0.023742621764540672,
0.02912108041346073,
0.023329295217990875,
0.05533343181014061,
-0.027590597048401833,
-0.04284519702196121,
-0.02042018249630928,
-0.016008662059903145,
0.065150685608387,
0.0694630891084671,
-0.04859... |
<p>We know that the uncertainty product of general states is bounded by the inequality described by Heisenberg's uncertainty relation. And the ground state of the quantum harmonic oscillator falls under the minimum uncertainty product ($\frac{\hbar}{2}$). Do the excited states of QHO have also the minimum uncertainty p... | g7383 | [
-0.012147906236350536,
0.023287637159228325,
-0.028881847858428955,
0.07927431166172028,
-0.007958776317536831,
0.052836932241916656,
-0.01640094816684723,
0.021378621459007263,
0.021738560870289803,
-0.04081113263964653,
-0.031043343245983124,
0.020158082246780396,
-0.08040992170572281,
-... |
<p>I'm bit confused about 'black' as a color. As per my knowledge, it is not given in visible color spectra like other colors for example red, violet etc. Also I'm confused with definition of color--does it mean the reflection of respective wavelengths from an object perceived by human eyes or latest electronic sensors... | g909 | [
0.007872691377997398,
-0.006947399117052555,
0.038429152220487595,
-0.004958490375429392,
0.04521084949374199,
0.0010735943214967847,
0.005915613379329443,
0.05440366640686989,
0.004861811175942421,
-0.032900676131248474,
0.028456252068281174,
0.043364234268665314,
0.05387897044420242,
0.0... |
<p>im trying to develop a flexible robotic arm filled with ferro fluid. Different flexible motions can be performed using this concept.</p> | g7384 | [
0.0732964277267456,
0.03405481204390526,
0.020010607317090034,
0.022037401795387268,
0.036268800497055054,
-0.004725220613181591,
-0.013295545242726803,
0.0009952193358913064,
-0.04631340876221657,
-0.05548931658267975,
-0.0005646472563967109,
-0.041281476616859436,
0.03751327469944954,
0.... |
<p>I am trying to solve the following problem that involves motion in a straight line. I am not quite sure how to go about it though. I know it will involve formulas and derivatives but which specific ones would I use?</p>
<blockquote>
<p>An electron has a constant acceleration of 2.6 m/s^2. At a certain
instant i... | g7385 | [
0.08414320647716522,
0.07188951224088669,
0.023365916684269905,
0.024816762655973434,
0.042258620262145996,
-0.04992913454771042,
0.0302407406270504,
-0.020220549777150154,
-0.08714918792247772,
0.014564650133252144,
-0.07516470551490784,
0.0619872622191906,
0.026262883096933365,
0.0396726... |
<p>Why do we have two different types of phonons, <a href="http://en.wikipedia.org/wiki/Phonon#Acoustic_and_optical_phonons" rel="nofollow">optical and acoustical</a>? Why are they called optical phonons? </p> | g7386 | [
0.04927168786525726,
-0.0018902717856690288,
0.009342468343675137,
-0.016665183007717133,
0.07254119962453842,
-0.024058761075139046,
0.03260578587651253,
0.01096260640770197,
0.0029634302482008934,
-0.032721199095249176,
-0.03706491366028786,
0.028772467747330666,
0.009168739430606365,
0.... |
<p>From what I understand, it seems like you can only "add" beams together. You can use a beam combiner, basically using a beam splitter in reverse, to combine two beams. In homodyne detection, you use a local oscillator beam to mix with the signal beam so you can decipher the difference in phase change which would giv... | g7387 | [
0.004765538964420557,
-0.03139792010188103,
0.00890412088483572,
0.0006701007951050997,
0.06574533879756927,
-0.04084820672869682,
0.013369007036089897,
0.040845055133104324,
-0.005828903056681156,
0.013445816934108734,
0.001670557539910078,
0.01124096754938364,
-0.03333936259150505,
-0.01... |
<p>How would you determine whether an object is at equilibrium or not?</p>
<p>What is the definition of <a href="http://en.wikipedia.org/wiki/Mechanical_equilibrium" rel="nofollow">equilibrium</a>?</p> | g7388 | [
0.008162249810993671,
0.023670129477977753,
0.0027812172193080187,
-0.024343833327293396,
0.07339872419834137,
-0.04369804263114929,
0.03313013166189194,
-0.0344131700694561,
-0.04952716827392578,
-0.0024938443675637245,
-0.07557591795921326,
-0.018165575340390205,
0.02399183064699173,
0.0... |
<p>There are lots of devices that purport to measure the absolute value of sound pressure levels. <a href="http://rads.stackoverflow.com/amzn/click/B000A6V5FS" rel="nofollow">Here is an example</a>, <a href="http://rads.stackoverflow.com/amzn/click/B000I4ZVHU" rel="nofollow">here's another</a>, there's also this <a hr... | g7389 | [
0.06667973101139069,
-0.06392354518175125,
-0.007081544026732445,
-0.02181243896484375,
0.05940443277359009,
-0.0014182914746925235,
-0.014709548093378544,
-0.014680769294500351,
-0.051937732845544815,
0.022952482104301453,
0.010889875702559948,
-0.017243657261133194,
0.03581549972295761,
... |
<p>If a container like a balloon but with constant volume is filled, is it possible to pack air molecules so closely together that they don't have any empty space between them? If so, what would this material look like?</p> | g7390 | [
0.015472374856472015,
0.020363029092550278,
0.015836581587791443,
0.020719945430755615,
-0.03406545892357826,
0.021365458145737648,
-0.06647519767284393,
0.017741821706295013,
-0.042724061757326126,
-0.03279239311814308,
-0.010772157460451126,
-0.05314447358250618,
-0.017786135897040367,
-... |
<p>The standard lore in QFT is that one must work with renormalised fields, mass, interaction etc. So we must work with "physical" or renormalised quantities and all our ignorance with respect to its relation with "bare quantities" is taken care by counter terms which (surprisingly!!) cancel infinities. My question is:... | g7391 | [
0.04513649642467499,
0.038012124598026276,
-0.00971028208732605,
-0.06981755793094635,
0.03040669485926628,
-0.021797433495521545,
0.01100853644311428,
0.08719233423471451,
-0.009721758775413036,
-0.045314908027648926,
-0.042384639382362366,
-0.015232211910188198,
-0.025951094925403595,
0.... |
<blockquote>
<p>A $150~\text{V}$ battery is connected across two parallel metal plates of area $28.5~\text{cm}^2$ and separation $0.00820~\text{m}$. A beam of alpha particles (charge $+2e$, mass $6.64 \times 10^{-27}~\text{kg}$) is accelerated from rest through a potential difference of $1.75~\text{kV}$ and enters th... | g7392 | [
0.028976434841752052,
0.0653371810913086,
-0.012645394541323185,
-0.012606467120349407,
0.07507602870464325,
0.04392370954155922,
0.00000759863041821518,
0.055226296186447144,
-0.02168496884405613,
0.01975746639072895,
0.02539166249334812,
0.0599488839507103,
-0.04200056940317154,
-0.00106... |
<p>Cern recently stated that antimatter may be repelled by matter, much like the opposite effect of Gravity. So is it possible that antimatter is actually repelled to the edges of the Universe to create a sort of outer-shell, something that allows the expansion of the Universe into nothingness..</p> | g7393 | [
0.0206502266228199,
0.049964044243097305,
0.028741726651787758,
-0.043746259063482285,
0.04070794954895973,
0.06248704716563225,
-0.07600858807563782,
0.007029129192233086,
-0.03714120015501976,
-0.05299697816371918,
0.05458148196339607,
-0.007009066641330719,
0.021243693307042122,
0.01349... |
<p>Problem:</p>
<p>An object is undergoing simple harmonic motion with period 1.2s and amplitude 0.6m. At $t=0$, the object is at $x=0$. How far is the object from the equilibrium position when $t=0.480$s?</p>
<p>Attempt at solution:</p>
<p>I used the displacement equation :</p>
<p>$$x(t)=A\cos(\omega t+\phi)$$</p>... | g7394 | [
0.02461622841656208,
-0.015038762241601944,
0.022395284846425056,
-0.060727715492248535,
0.014443333260715008,
-0.012482662685215473,
0.04156617447733879,
-0.024923129007220268,
0.03133486211299896,
0.002101622289046645,
-0.01919877529144287,
0.03361167386174202,
0.013757020235061646,
-0.0... |
<p>what does string theory have to say about the trace anomaly in the expectation value of the stress energy tensor of massless quantum fields on a curved background and its interpretation as the emergence of an extra scalar degree of freedom in the semiclassical limit of GR + QFT?
Is it something that can be proved? t... | g7395 | [
0.021140340715646744,
0.010344482958316803,
0.023130588233470917,
-0.024585915729403496,
0.06841979175806046,
0.06601656228303909,
0.014203236438333988,
-0.010689157992601395,
0.010757259093225002,
-0.025778235867619514,
-0.03524605929851532,
0.03984997048974037,
0.004731848835945129,
-0.0... |
<p>I have a question about the restoring force in elastic band or rope which confusing me for a long time.</p>
<p>As I was told in high school physics, for an elastic band (or spring), if Hooke's law holds, we have $F = k\Delta x$. What's confusing me is: should F be the total force acting on the object or the restori... | g7396 | [
0.03385326638817787,
-0.039332158863544464,
0.02196592651307583,
0.013470578007400036,
0.06116450950503349,
-0.009259105660021305,
0.014335470274090767,
0.01960139535367489,
-0.005132225342094898,
-0.07616971433162689,
0.02603156864643097,
0.002329496666789055,
0.013495266437530518,
-0.008... |
<p>I'm a statistician with a little training in physics and would just like to know the general consensus on a few things.</p>
<p>I'm reading a book by <a href="http://en.wikipedia.org/wiki/John_Moffat_%28physicist%29">John Moffat</a> which basically tries to state how GR makes failed predictions in certain situations... | g7397 | [
-0.00028581495280377567,
0.02371138706803322,
-0.00494544580578804,
-0.04276609793305397,
0.01696724072098732,
0.08166266977787018,
-0.004326752852648497,
-0.021072108298540115,
-0.0446188859641552,
-0.034310873597860336,
0.1013721376657486,
-0.030025362968444824,
0.06245223432779312,
0.00... |
<p>Recently I heard that both of "languages" of scattering theory (formal solution by method of classical scattering theory and its reworking by Feynman with his rules) predict virtual particles. But for first language intermediate states may be interpreted as particles which satisfy corresponding wave equations but do... | g7398 | [
0.006662757135927677,
0.012154674157500267,
0.018807439133524895,
-0.01194587629288435,
0.0542503260076046,
0.013552729040384293,
-0.009587518870830536,
0.02464419975876808,
0.0014962542336434126,
-0.009951521642506123,
-0.04689546674489975,
-0.009048204869031906,
-0.019490282982587814,
-0... |
<p>I understand that changing electric field produces magnetic field and changing magnetic field produces electric field.</p>
<p>Are these produced magnetic and electric field produced due to one defined to be constant or variable?
If these are defined to be variable then do they continue to produce one another? By th... | g7399 | [
0.046713948249816895,
-0.013250782154500484,
0.0013672851491719484,
-0.013193560764193535,
0.02962655760347843,
0.008245090022683144,
-0.017486361786723137,
-0.003895706031471491,
-0.02130148373544216,
-0.019529148936271667,
-0.09724361449480057,
0.004786491859704256,
-0.00786364171653986,
... |
<p>It seems that the Bloch equations, or a suitable generalization thereof, are enough to phenomenologically model the measurement process in NMR. Has anyone attempted a fully quantum mechanical model of the NMR spin system and measurement coil together? </p>
<p>It seems to me that these coils are intentionally of l... | g7400 | [
-0.019699973985552788,
-0.08646021783351898,
0.0020096045918762684,
-0.00535011338070035,
0.014518611133098602,
-0.04450886696577072,
-0.003186488291248679,
0.021095259115099907,
0.0027502018492668867,
0.000321200059261173,
-0.02059902995824814,
-0.010092147625982761,
-0.00950469821691513,
... |
<p>That is perhaps a bit of an advertisement, but a couple of collaborators and myself just sent out a <a href="http://arxiv.org/abs/1110.2791v1" rel="nofollow">paper</a>, and one of the results there is a little bit surprising. We found (in section 6E) a fermionic local symmetry which closes to a tensor gauge symmetry... | g7401 | [
0.03400954231619835,
0.006859414279460907,
0.0019277373794466257,
-0.05310015380382538,
0.028121743351221085,
0.009282361716032028,
0.00531493965536356,
0.019046274945139885,
-0.029985317960381508,
-0.028377242386341095,
-0.007043305318802595,
-0.009891362860798836,
0.04504350572824478,
-0... |
<p>I am currently studying generalized probabilistic theories. Let me roughly recall how such a theory looks like (you can skip this and go to "My question" if you are familiar with this).</p>
<p><strong>Recall</strong>: In a <em>generalized probabilistic theory</em> (GPT), the set of states is given by a convex subse... | g7402 | [
-0.03463248908519745,
0.05862940847873688,
-0.01769852824509144,
0.029477501288056374,
-0.01572246477007866,
0.0234066192060709,
0.0544341579079628,
0.038536105304956436,
0.051918938755989075,
0.01238549966365099,
-0.017612528055906296,
-0.05957277864217758,
0.03113873302936554,
-0.0200592... |
<p>This question comes from reading <a href="http://theoreticalphysics.stackexchange.com/questions/278/which-letter-to-use-for-a-cft">Andre's question</a> where I wandered whether that question even makes sense physically. In mathematics, VOAs form a category, does this category as a whole have a physical interpretatio... | g7403 | [
0.03166705742478371,
-0.005106159020215273,
0.02336716093122959,
-0.0647040531039238,
0.054488543421030045,
-0.02778877690434456,
0.03221889212727547,
-0.03218906745314598,
-0.024952897801995277,
-0.04443605989217758,
0.04463161155581474,
-0.0207217950373888,
0.03693711757659912,
-0.002733... |
<p>The gravitational acceleration on Earth is approximately $ 10 \mathrm{m}/\mathrm{s}^2 $. Compared to this, the tidal effect of the Moon's gravity gives a local variation in the acceleration of approximately $ 9 \cdot 10^{-7} \mathrm{m}/\mathrm{s}^2 $, that is, seven orders of magnitudes less. The level of the wate... | g7404 | [
0.0886433944106102,
0.059270523488521576,
-0.006549360696226358,
0.007384436670690775,
0.01867031678557396,
0.08817360550165176,
0.031634606420993805,
-0.024325808510184288,
-0.04051823168992996,
-0.034334927797317505,
0.011033817194402218,
0.020671773701906204,
0.027926279231905937,
0.040... |
<p>The single inpurity Anderson Hamiltonian is
$H=\sum_{\sigma}\epsilon_{\sigma}n_{d,\sigma}+Un_{d,\uparrow}n_{d,\downarrow}+\sum_{k,\sigma}\epsilon_{k}c_{k,\sigma}^{+}c_{k,\sigma}+\sum_{k,\sigma}(V_{k}c_{d,\sigma}^+c_{k,\sigma}+h.c.)$</p>
<p>where $n_{d,\sigma}$ is the occupation number of d electron and $\epsilon_d$... | g7405 | [
-0.005725985858589411,
0.02351089008152485,
-0.02891699969768524,
-0.04633322358131409,
0.04093344137072563,
0.035506196320056915,
0.05825474485754967,
-0.0024002408608794212,
0.017338361591100693,
0.02778533287346363,
0.03636401519179344,
0.018187448382377625,
0.025479279458522797,
-0.022... |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.