question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>I read that powerful pulsed lasers can change isotopes:
<a href="http://www.springerlink.com/content/89c45n12bxkn075l/" rel="nofollow">J. Magill, et. al.: "Laser transmutation of iodine-129"</a>.</p>
<p>Did anyone estimate what would be the energy costs to transmutate 1 kg of fission product from a conventional rea... | g12678 | [
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<p>Why is it not possible to store windfarm energy in battery banks? A lot of energy isn't being used when wind farms are at peak and we have no way of storing it. This is wasteful. So why don't we use battery banks?</p> | g12679 | [
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<p>I know from basic physics lessons that a box painted black will absorb heat better than a box covered in tin foil. However a box covered in tin foil will lose heat slower than a black box. </p>
<p>So what is the best way to conserve the temperature of a box? (aiming for 0 degrees Celsius inside the box when it's -6... | g12680 | [
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<p>Another crazy question:</p>
<p>1) I will need to generate some ozone for chemical reactions, and what seems to be the most straightforward way is using germicidal lamps, but the question is how to estimate how much ozone is produced (for let's say 100W of lamps) and what should be inlet oxygen flow for maximum ozon... | g12681 | [
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<p>This question is related to <a href="http://physics.stackexchange.com/questions/11978/impact-of-covering-glass-on-lens-performance">Impact of covering glass on lens performance</a>.</p>
<p>I use a 63x TIRF objective with a numerical aperture of 1.46 and oil immersion.
The immersion oil has an index of $n_e=1.518$.
... | g12682 | [
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<p>In a notable answer to <a href="http://physics.stackexchange.com/questions/31672/what-causes-a-force-field-to-be-nonconservative">this question</a>, Qmechanic formulates conditions for "conservative" velocity-dependent forces (e.g. the Lorentz force, but not velocity-proportional friction) that are analogous to tho... | g12683 | [
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<p>I have been studying about the SU(2) symmetry in Heisenberg Hamiltonian with a paper 'SU(2) gauge symmetry of the large U limit of the Hubbard model' written by Ian Affleck et al(Phys. Rev. B 38, 745 – Published 1 July 1988). In the paper, they represent the spin in terms of fermionic operators with constraint that ... | g12684 | [
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<p>Can we implement a scale dependent cutoff Λ to string theory? Can we perform a renormalization group analysis of string theory consistently?</p> | g612 | [
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<blockquote>
<p>Ultimately, the factor limiting the
maximum speed of a rocket is:</p>
<ol>
<li>the amount of fuel it carries</li>
<li>the speed of ejection of the gases</li>
<li>the mass of the rocket</li>
<li>the length of the rocket</li>
</ol>
</blockquote>
<p>This was a multiple-choice question i... | g12685 | [
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<p>To completely localize a string within any bounded region of space, no matter how large, requires an infinite energy. Does this mean strings modes are inherently nonlocal?</p> | g12686 | [
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<p>I think one catch in Twin Paradox was about the big acceleration that can turn back the traveling twin from light speed outward bound, to become light speed inward bound.</p>
<p>What if there is strictly no acceleration?</p>
<ol>
<li>Peter is on a space ship, traveling 99% of light speed. He is exactly 20 years a... | g12687 | [
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<p>I'm having trouble doing it. I know so far that if we have two Hermitian operators $A$ and $B$ that do not commute, and suppose we wish to find the quantum mechanical Hermitian operator for the product $AB$, then </p>
<p>$$\frac{AB+BA}{2}.$$ </p>
<p>However, if I have to find an operator equivalent for the radial ... | g12688 | [
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<p>I have read a <a href="http://arxiv.org/abs/1310.7534">recent paper</a> that says that limit on the <a href="http://en.wikipedia.org/wiki/Electron_electric_dipole_moment">EDM of the electron</a> has now been measured to 12 times better accuracy. According to that paper, as I understood, there should be a difference ... | g12689 | [
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<p>There is a set called <a href="http://en.wikipedia.org/wiki/Vitali_set" rel="nofollow">Vitali Set</a> which is not Lebesgue measurable.</p>
<p>Analogously, there also exists a Vitali set $Y$ in $\mathbb R^3$ which is a subset of $[0,1]^3$ and $|Y\cap q|=1$ for all $q\in \mathbb R^3/\mathbb Q^3$. However, I'm curio... | g12690 | [
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<p>I am trying to derive <a href="http://en.wikipedia.org/wiki/Birkhoff%27s_theorem_%28relativity%29" rel="nofollow">Birkhoff's theorem</a> in GR as an exercise: a spherically symmetric gravitational field is static in the vacuum area. I managed to prove that $g_{00}$ is independent of t in the vacuum, and that $g_{00}... | g12691 | [
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<p>I saw an exercise where you had to calculate the units of $C_i, i=1,2$ from an equation like this:</p>
<ul>
<li>$v^2=2\cdot C_1x$ and</li>
<li>$x=C_1\cdot \cos(C_2\cdot t)$</li>
</ul>
<p>where</p>
<ul>
<li>$x$ means <em>meters</em>,</li>
<li>$t$ means seconds and</li>
<li>$v$ means velocity.</li>
</ul>
<p>For $C... | g12692 | [
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<p>First, a bit about my thoughts. I believe we have the capability today to provide energy, water, food, education, and transportation to every man woman and child on the planet. To that end, I would like to become a force that brings about this change.</p>
<p>In trying to meet the first goal, which is to provide e... | g12693 | [
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<p>I was trying to prove it 2 ways,</p>
<p>1st way:
$$p=mΔV$$
$$a=ΔV/t$$
$$ΔV=at$$
$$p=m*a*t$$</p>
<p>Remember
$$F=ma$$
$$F(t)=p$$</p>
<p>The derivative of momentum just gives us the "regular force" since b4 that momentum = force as a function of time. NOT SURE IF THIS PART IS CORRECT
thus,
$$dp/dt = F$$</p>
<p>2nd... | g12694 | [
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<p>A common result of theoretical analysis in physics is some sort of relation derived from physical parameters and typically expressed in the form of a non-dimensional parameter. These scale relations are not equalities but proportional relationships. For instance, in turbulence you end with with </p>
<p>$$ \frac{\et... | g12695 | [
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://physics.stackexchange.com/questions/39161/what-happens-to-an-embedded-magnetic-field-when-a-black-hole-is-formed-from-rota">What happens to an embedded magnetic field when a black hole is formed from rotating charged dust?</a> </p>
</blockquo... | g403 | [
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<p>Wikipedia's page on <a href="http://en.wikipedia.org/wiki/Escape_velocity" rel="nofollow">escape velocity</a> puts the escape velocity for an object travelling out of the Solar System at ~525km/s. This figure is slightly higher than the <a href="http://en.wikipedia.org/wiki/Voyager_1" rel="nofollow">tentative veloci... | g12696 | [
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<p>I am failing to explain why light won't remain inside the wooden box in the following situation. I considered a wooden box closed from all the sides, with a bulb inside it. If we switch on the bulb, light will be emitted from the bulb inside the box, if we switch off the bulb, I assumed the light to disappear, which... | g12697 | [
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<p>Is it necessary to add a constant term in the superpotential of hybrid inflation within supergravity in order to cancel SUSY vacuum energy at the end of inflation? </p> | g12698 | [
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<p>In eqn. (3.11) of Srednicki's QFT book only the positive root is considered; i.e.,</p>
<p>$ \omega = + \sqrt{(k^2 + m^2 )} $</p>
<p>Why the negative root is not considered?
And what is the $\omega$?</p> | g12699 | [
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<p>Bearing in mind I am a layman - with no background in physics - please could someone explain what the "big deal" is with quantum entanglement?</p>
<p>I used to think I understood it - that 2 particles, say a light-year apart spatially, could affect each other physically, instantly. Here I would understand the "big... | g250 | [
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<p>I've produced experimental data over how the boiling point of water varies with pressure and temperature and plotted this in a PT graph. I would like to verify my results using theory. The <a href="http://en.wikipedia.org/wiki/Clausius-Clapeyron_relation" rel="nofollow">Clausius-Clapeyron equation</a> appears to be ... | g12700 | [
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<p>I understand that power is that rate at which work is done and that because of this the power in an inductor is equal to
$$P=\frac{d}{dt} \left(\frac12Li^2\right).$$
I also understand that the power is also equal to
$$P=Li\frac{di}{dt}$$
since $L\,\frac{di}{dt}=V$ and $Vi$ is power. </p>
<p>I understand that sin... | g12701 | [
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<p>Denote the pure system as system 1, with both continuum and discrete eigen energy. $G_0$ is its Green's function.</p>
<p>After introducing some impurities, we call the resultant system system 2 with new Green's function $G$, and $T$ is T matrix.</p>
<p>We have
$G=G_0 + G_0 T G_0$</p>
<p>My question is, since the ... | g12702 | [
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<p>How to prove conservation of electric charge using Noether's theorem according to classical (non-quantum) mechanics?
I know the proof based on using Klein–Gordon field, but that derivation use quantum mechanics particularly.</p> | g12703 | [
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<p>I am trying to understand the photoelectric-effect deeply. My teacher used the <a href="http://en.wikipedia.org/wiki/Planck%27s_law" rel="nofollow">Planck's law</a> and integrated it to deduce the <a href="http://en.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_law" rel="nofollow">Stefan-Boltzmann law</a>. He somehow... | g12704 | [
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0.038935333490371704,
... |
<p>I wonder if it's possible to discover another version of quantum theory that doesn't depend on complex numbers. We may discover a formulation of quantum mechanics using p-adic numbers, quaternions or a finite field etc. Also, physical states lives on a Hilbert space. What if we consider the infinite dimensional Hilb... | g12705 | [
-0.013894042000174522,
-0.003970939200371504,
-0.01592971757054329,
-0.04675291106104851,
-0.04055801406502724,
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0.02746899239718914,
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0.003827523672953248,
-0.0786571204662323,
0.03755499795079231,
-0.10312500596046448,
0.07782401889562607,
0.020... |
<p>How to explain <a href="http://en.wikipedia.org/wiki/Tsirelson%27s_bound" rel="nofollow">Tsirelson's inequality</a> using extended probabilities?</p>
<p>Some people have tried explaining the Bell inequalities using extended probabilities.</p>
<p>For instance, a pair of entangled photons are created and sent off to... | g12706 | [
-0.037179507315158844,
0.052827395498752594,
0.013706708326935768,
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0.002212979830801487,
0.03886674344539642,
0.026051240041851997,
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0.041596200317144394,
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0.008666574954986572,
-0.06940516084432602,
... |
<p>How can the <a href="http://www.google.com/search?q=glueball+mass+estimate" rel="nofollow">glueball mass</a> be calculated in Yang Mills theory?</p> | g12707 | [
0.013933495618402958,
0.007297528441995382,
-0.00022185077250469476,
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0.04928244650363922,
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-0.0012222144287079573,
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-0.03272510692477226,
0.03708304837346077,
0.04... |
<p>Since average velocity is defined as$^1$
$$\vec{\mathbf v}_\mathrm{av}=\frac{\vec{\mathbf x}-\vec{\mathbf x}_0}{t-t_0},$$
where $\vec{\mathbf x}$ denotes position, why is this quantity equal to
$$\frac{\vec{\mathbf v}+\vec{\mathbf v}_0}{2},$$
where $\vec{\mathbf v}=\frac{d\vec{\mathbf x}}{dt}$ and $\vec{\mathbf v}_0... | g12708 | [
0.0559903047978878,
0.0016294856322929263,
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0.03331330418586731,
0.05846739187836647,
0.0026380408089607954,
0.05660489574074745,
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0.006978488061577082,
-0.0009016041876748204,
-0.02832479029893875,
0.0257... |
<p>Consider the quantum effective action of a fixed QFT. If we compute it perturbatively to finite loop order $\ell$, we get a sum over an infinite number of Feynman diagrams. For example, the 1-loop quantum effective action of QED contains contributions from all diagrams in which a single electron loop is connected t... | g12709 | [
-0.03378225117921829,
0.009848270565271378,
-0.009442073293030262,
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0.035427797585725784,
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0.02654569409787655,
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0.030685849487781525,
0.0023146371822804213,
... |
<p>Is there precision experimental evidence for or contradicting Furry's theorem -- that only even degree VEVs are non-zero, specifically for the EM field?</p> | g12710 | [
0.01228263322263956,
0.016547508537769318,
0.007799109444022179,
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0.09274335205554962,
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0.00011967225873377174,
... |
<p>AdS/CFT at D = 3 (on the AdS side) seems to have some special issues which I bundled into a single question</p>
<ul>
<li>The CFT is 2D hence it has an infinite-dimensional group of symmetries (locally). The global (Mobius) conformal transformations correspond to isometries of AdS. What is the meaning of the other c... | g12711 | [
0.006344822235405445,
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0.04782392457127571,
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-0.... |
<p>Can anyone point me to a paper dealing with simulation of QED or the Standard Model in general? I will particularly appreciate a review paper.</p> | g12712 | [
0.013160951435565948,
0.032502613961696625,
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0.006212204694747925,
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0.021446434780955315,
0.054644450545310974,
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0.04522206261754036,
-0... |
<p>For Haag-Kastler nets $M(O)$ of von-Neumann algebras $M$ indexed by open bounded subsets $O$ of the Minkowski space in AQFT (algebraic quantum field theory) the DHR (Doplicher-Haag-Roberts) superselection theory treats representations that are "localizable" in the following sense.</p>
<p>The $C^*-$algebra</p>
<p>$... | g12713 | [
0.05180569738149643,
0.029175424948334694,
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0.008878740482032299,
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-0.029861848801374435,
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-0.0012119585881009698,
... |
<p>I am currently making an exercise from Paterson,1983, IV.3.ii. It goes as follows</p>
<blockquote>
<p>Water flows steadily and incompressibly along a pipe whose area cross section $A(x)$ varies slowly with the coordinate $x$ along the pipe. Use the conservation of mass and/or incompressibility to calculate the m... | g12714 | [
0.06291685253381729,
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0.004452113527804613,
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0.01757967658340931,
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0.09157883375883102,
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0... |
<p>I am wondering how you calculate the vector forces of the wind on an object? The information I have is the bearing direction of the wind and the speed of the wind. So how do I calculate the <em>x</em> and <em>y</em> vector forces of the wind as shown in the diagram below? Also I do realise that using trig I can do a... | g12715 | [
0.04337979480624199,
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0.02106182649731636,
0.013173770159482956,
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-... |
<p>So we all heard about the twins paradox to explain einstein's time space relativity.</p>
<p>Wikipedia Quote :"
In physics, the twin paradox is a thought experiment in special relativity involving identical twins, one of whom makes a journey into space in a high-speed rocket and returns home to find that the twin wh... | g12716 | [
0.00232344469986856,
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0.006855512969195843,
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0.06069016829133034,
0.01... |
<p>I am aware that flavor $\neq$ mass eigenstate, which is how mixing happens, but whenever someone talks about neutrino oscillations they tend to state without motivation that when neutrinos are actually propagating, they are doing so in a mass eigenstate. Presumably this is glossed over because it is a deep and basic... | g728 | [
0.00469988351687789,
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0.006226756609976292,
0.001149452175013721,
0.0370919443666935,
0.06896825... |
<p>I'm studying for my nuclear physics exam and the book we use is Introductory Nuclear Physics by K.S. Krane. In the chapter on Basic Nuclear Structure, we research the deuteron. However, when discussing the total angular momentum of the deuteron, something confuses me (p84 if someone has the book). I'll copy the para... | g12717 | [
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<p>I am looking for a system capable of creating a gradient of $100\, \mathrm{K}/\mathrm{\mu \textrm{m}}$ on a $30\, \mathrm{\mu}\textrm{m}$ spacing of a system mounted on a Si-N membrane. My so-called nanoheater is not up to the task.</p> | g12718 | [
0.005210365168750286,
0.04160143807530403,
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0.03706861287355423,
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... |
<p>Is there any substantial body of work in physics on dynamically simulating effects of surface tension on liquids? The texts i found so far on fluid dynamics all seem to ignore surface tension, probably because they concentrate on liquids without free surfaces and fluid mechanics texts consider only special cases, li... | g12719 | [
0.018489502370357513,
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0.05572809651494026,
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0.021008452400565147,
... |
<p>I have something like this:</p>
<p>$$\frac{0.04\,\text{kg} \times 90\,^{\circ}\text{C} + 0.06\,\text{kg} \times 50\,^{\circ}\text{C}}{0.1\,\text{kg}} = T_k$$</p>
<p>Where $T_k$ is a temperature, in Celsius. But I have no idea how to multiply Celsius times kilograms. How do I do it?</p> | g12720 | [
0.03786895424127579,
0.029447592794895172,
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0.04322633892297745,
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0.02359917014837265,
-0.07965701818466187,
-0.02610071375966072,
0.05489223077893257,
-0.02570110... |
<p>Summary: What "well-known" and short parametrized mathematical
function describes daily and hourly temperature for a given location? </p>
<p>If you look at the mean daily temperature graph for a given location,
it looks like a sine wave with a period of one year. </p>
<p>Similarly, the hourly temperature for a g... | g12721 | [
0.010826220735907555,
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-0.02130126766860485,
0.019462550058960915,
0.006430461537092924,
0.05375901237130165,
... |
<p>Is there a formula that gives me the instantaneous change in temperature under ideal circumstances? Details: </p>
<p>On a cloudless day, temperature is affected by two major things(?): </p>
<ul>
<li><p>While the Sun is up, incoming solar radiation, which increases the temperature at a known rate(?) depending on th... | g12722 | [
0.021875454112887383,
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0.009105926379561424,
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0.01434401236474514,
0.027142787352204323,
0.0643979161977768,
0.08559274673461914,
0.04... |
<p>I am studying Statistical Mechanics and Thermodynamics from a book that i am not sure who has written it, because of its cover is not present.</p>
<p>There is a section that i can not understand:</p>
<p>${Fj|j=1,..,N}$</p>
<p>$S= \sum_{j=1}^{N} F_{j}$</p>
<p>$<S>=< \sum_{j=1}^{N} F_{j}> = \sum_{j=1}^... | g12723 | [
0.05047771707177162,
0.00391830038279295,
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0.03349548578262329,
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-0.039311300963163376,
-0.06159050017595291,
0.00804502610117197,
0.04799933731555939,
0.... |
<p>In mathematics, sum of all natural number is infinity.</p>
<p>but Ramanujan suggests whole new definition of summation.</p>
<p>"The sum of $n$ is $-1/12$" what so called <a href="http://en.wikipedia.org/wiki/Ramanujan_summation" rel="nofollow">Ramanujan Summation</a>.</p>
<p>First he find the sum, only Hardy reco... | g12724 | [
0.018910527229309082,
0.04398549720644951,
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0.004210134502500296,
0.036763306707143784,
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0.006240801885724068,
0.0012266850098967552,
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0.0023911145981401205,
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-0.015338772907853127,
0.023655785247683525,
... |
<p>I can't be the only one who's ever thought of this, but obviously it hasn't caught on:</p>
<p>In terms of energy density, fossil fuels are the best thing around short of enriched uranium (and, flammability aside, a <em>lot</em> safer). The biggest two problems with using fossil fuel as an energy source are the low ... | g12725 | [
0.027381381019949913,
0.05405978858470917,
0.00881845224648714,
0.03249187022447586,
0.02962508425116539,
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0.02490447647869587,
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0.05932943522930145,
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0.050522882491350174,
-0.017... |
<p>There are two different sorts of inertia: <a href="http://en.wikipedia.org/wiki/Mass#Inertial_mass" rel="nofollow">inertial mass</a> and <a href="http://en.wikipedia.org/wiki/Moment_of_inertia" rel="nofollow">moment of inertia</a>.</p>
<p>I am currently reading about moment of inertia. Now, I know inertia is an imp... | g12726 | [
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0.021827401593327522,
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0.009084911085665226,
0.05090370401740074,
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0.02611721120774746,
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0.010106912814080715,
-0.030742190778255463,
-0.0410168282687664,
-0.025077590718865395,
-0.0... |
<p>I have a question pertaining to the ideas behind the considered homogeneity and isotropic nature of the universe (at a grand scale) versus the theory of a chaotic and anisotropy structure of the universe.
I am particularly ignorant on this subject, but I am assuming that the idea of fractal cosmology expresses that... | g12727 | [
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0.016606325283646584,
0.02703961171209812,
0.02665218897163868,
0.02789880335330963,
0.02191491238772869,
0.052588172256946564,
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0.036393459886312485,
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0.07611126452684402,
0.0546... |
<p>can anyone explain Multi-step nuclear reactions in terms of direct nuclear reactions .</p> | g12728 | [
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0.09436435997486115,
0.021... |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://physics.stackexchange.com/questions/20034/what-practical-issues-remain-for-the-adoption-of-thorium-reactors">What practical issues remain for the adoption of Thorium reactors?</a> </p>
</blockquote>
<p>I have been reading and watching a bi... | g404 | [
0.003334037959575653,
0.06972263008356094,
0.015495491214096546,
0.07109954208135605,
0.02108912542462349,
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0.0282779261469841,
0.09795168787240982,
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-0.010137339122593403,
0.034057244658470154,
0.033502932637929916,
0.03581557422876358,
0.0119029... |
<p>Mr.E is on a luxury spaceship travelling about 1/2 the speed of light and finds a cubic lump of unstable matter(attached to a bomb) in his cabin. He of course is an expert with bombs but this device is based on the unstable matter's critical mass. The lump of matter fluctuates a tiny amount constantly but if it is m... | g12729 | [
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0.03985123336315155,
0.030587662011384964,
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0.02379060909152031,
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0.008373747579753399,
0.012070294469594955,
0.052017778158187866,
0.010541... |
<p>In atomic physics, it is common knowledge that following the absorption edge, where the photon energy equals the binding energy of a core electron, a monotonic decrease in the absorption coefficient with increasing photon energy is observed. Obviously it is so common, that everyone mentions it, but nobody cares to e... | g12730 | [
0.031508538872003555,
0.05185360834002495,
0.006820680573582649,
0.014354411512613297,
0.05461035668849945,
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-0.02551531232893467,
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0.05434724688529968,
0.027841931208968163,
-0.00... |
<p>Conservation of energy states energy can't be destroyed, but isn't energy used up when walking in a straight line? If your not walking up a slope, kinetic energy isn't converted to gravitational potential energy, so what is it converted to?</p> | g12731 | [
0.03789800778031349,
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0.0030062547884881496,
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-0.0... |
<p>I am reading "Supercollision cooling in undoped graphene." <a href="http://www.nature.com/nphys/journal/v9/n2/full/nphys2494.html" rel="nofollow">There</a> the authors write: ``Above $T_{BG}$ (the Bloch-Gruneisen temperature), only a fraction of acoustic phonons with wave vector $q\le 2k_{F}$ can scatter off electro... | g12732 | [
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0.0043211751617491245,
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0.06759776175022125,
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-0... |
<p>A book I was reading stated that diffusion can exist without a gradient of a physical quantity. Heat is an example of diffusion because of temperature gradient and similar is the case of mass flow in chemistry. Can anyone give me an example for a gradient less diffusion process?</p> | g12733 | [
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0.0... |
<p>This question is based on problem II.3.1 in Anthony Zee's book Quantum Field Theory in a Nutshell (I'm reading this for fun- it isn't a homework problem.) </p>
<blockquote>
<p>Show, by explicit calculation, that $(1/2,1/2)$ is the Lorentz Vector. </p>
</blockquote>
<p>I see that the generators of SU(2) are the ... | g12734 | [
-0.03588830679655075,
-0.013410976156592369,
-0.027220051735639572,
-0.04350200667977333,
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-0.022900696843862534,
0.012737318873405457,
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0.014366094022989273,
0.043752167373895645,
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0.054085005074739456,
0.017493903636932373,
... |
<p>I came a comment in this paper: <a href="http://arxiv.org/abs/1212.5605v1">Scattering Amplitudes and the positive grassmannian</a> in the last paragraph of page 104 which says:
"One of the most fundamental consequences of space-time locality is that the ultraviolet and infrared singularities are completely independe... | g12735 | [
0.04105038568377495,
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0.015415066853165627,
... |
<p>On <a href="http://en.wikipedia.org/wiki/Electron_degeneracy_pressure" rel="nofollow">Wikipedia</a> the following statement is made without reference:</p>
<blockquote>
<p>Freeman Dyson showed that the imperviousness of solid matter is due to
quantum degeneracy pressure rather than electrostatic repulsion as had... | g12736 | [
0.06278439611196518,
0.03408701345324516,
0.014495056122541428,
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0.06931542605161667,
0.05386608839035034,
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0.026911301538348198,
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0.007501163054257631,
0.034... |
<p>It is said that the off-diagonal elements of density matrix are <code>coherence</code>. When a system </p>
<p>interacts with its environment the off-diagonal elements decay and the final density matrix </p>
<p>is the diagonal one, a statistical mixture. This process is called decoherence.</p>
<p>We know that ever... | g12737 | [
-0.002371270675212145,
0.0006328526069410145,
-0.003993292339146137,
-0.07450447976589203,
0.022241534665226936,
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0.012998956255614758,
0.027364008128643036,... |
<p>I have a confusion regarding the height of different layers of <a href="http://en.wikipedia.org/wiki/Atmosphere_of_Earth" rel="nofollow">atmosphere</a>. I have searched for this in some books but the information varies.</p> | g12738 | [
0.06242264434695244,
0.060812145471572876,
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0.033935874700546265,
0.008432058617472649,
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0.001514463685452938,
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... |
<p>I've heard that it is impossible to have a properly Lorentz-invariant lattice QFT simulation, as the Lorentz invariance is spoiled by the nonzero lattice distance $a$. I've also heard that there are other symmetries that <em>must</em> be preserved for a lattice simulation to be realistic.</p>
<p>What symmetries mus... | g12739 | [
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0.05328202620148659,
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0.002774683991447091,
0.0074625033885240555,
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0.0063062068074941635,
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0... |
<p>Consider the following situation: </p>
<p>You are locked inside a cylindric container allowing you to move around freely without being in contact with any of the items or surfaces aboard. The container is floating in space, far from any gravitational field, and is spinning around - like a washing machine would do, ... | g12740 | [
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0.02531428... |
<p><img src="http://i.stack.imgur.com/63qqd.jpg" alt="enter image description here"></p>
<p>For part (a), I know how to take the partial derivatives of S to get chemical potential, pressure. But there seems that I still need one equation to correctly express chemical potential in terms of T and P. </p>
<p>The biggest... | g12741 | [
0.029062923043966293,
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0.038057636469602585,
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0.005663865711539984,
0.0010692396899685264,
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0.0015970059903338552,
... |
<p>Alright, I am writing a space simulator for a 3D game and I would like to implement gravity of objects into it.</p>
<p>Is there a nice way to find a velocity vector which can be added to my engine output vector to create the effect of gravity.</p>
<p>In addition, how would I be able to find the velocities required... | g12742 | [
0.023677464574575424,
0.04700658097863197,
0.0006321649416349828,
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0.013783511705696583,
0.036636125296354294,
0.07622262090444565,
... |
<p><a href="http://en.wikipedia.org/wiki/Diffraction" rel="nofollow">Diffraction</a> is just light interacting with small objects, and bending, but this seems like a very imprecise definition to me. What is diffraction, actually? I was confused because there are at least two diffraction gratings, that I know of. One be... | g12743 | [
0.04921242594718933,
0.005787388887256384,
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0.001729233656078577,
0.024035578593611717,
0.02603624388575554,
-0.0... |
<p>I have a very hard time finding information about $HCCO$. I don't even know what it's name is. </p>
<p>I'd like to know what its main features are, where it shows up and/or what it's used for?</p> | g12744 | [
0.0029447218403220177,
0.05924609676003456,
0.019904501736164093,
0.041204702109098434,
0.03648512437939644,
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0.03573992848396301,
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-0.04887192323803902,
0.025417635217308998,
0.020004715770483017,
0.021438701078295708,
0.020... |
<p>Maxwell's equations specify two vector and two scalar (differential) equations. That implies 8 components in the equations. But between vector fields $\vec{E}=(E_x,E_y,E_z)$ and $\vec{B}=(B_x,B_y,B_z)$, there are only 6 unknowns. So we have 8 equations for 6 unknowns. Why isn't this a problem?</p>
<p>As far as I kn... | g289 | [
0.027975117787718773,
0.001459502731449902,
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0.04248500242829323,
0.058552175760269165,
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0.07925595343112946,
0.04348514601588249,
0.00009082009637495503,
-0.015294511802494526,
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0.0021441057324409485,
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<p>I have two powerful rare earth magnets, that are separated by a distance of 1 mm. I applied energy to bring them closer to each other, hence increasing the potential energy. Now, when one of the magnets is released(other is fixed) there is acceleration, with time force = 0 since the gap(D) is increased, yet there is... | g12745 | [
0.041846517473459244,
0.0420943908393383,
0.00893829483538866,
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0.0007518228958360851,
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0.008629167452454567,
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<p>We know that for a GPS we need to make a correction for both general and special relativity: general relativity predicts that clocks go slower in a higher gravitational field (the clock aboard a GPS satellite moves faster than a clock down on Earth), while special Relativity predicts that a moving clock is slower th... | g915 | [
0.04664520546793938,
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0.0008993145311251283,
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0.01863284781575203,
0.07700370997190475,
0.014369203709065914,
0.054344553500413895,
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<p>I have a doubt about the understanding of drift velocities in a current. My problem is that the textbook speaks very loosely about this. It's like: "well, if we apply a field $E$ then the charges will experience a force due to this field, aquire acceleration, colide between then and because of that there will be a s... | g12746 | [
0.03545033931732178,
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0.027827097... |
<p>Is it always assumed that, in a microcanonical ensemble, the number of particles is $N \gg 1$ ?</p>
<p>If no, are all the theorems related to the microcanonical description true even if the number of particles is small ?</p> | g12747 | [
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0.033927809447050095,
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<p>I have been learning Fourier transformation of a gaussian wave packet and i don't know how to calculate <strong>this</strong> integral:</p>
<p><img src="http://i.stack.imgur.com/G579S.png" alt="enter image description here"></p>
<p>In the above integral we try to calculate $\varphi(\alpha)$ where $\alpha$ is a sta... | g12748 | [
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0.03914541378617287,
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0.035... |
<p>An aluminium pot has a mass of 200g and contains 400g of ice at 0°C. How much heat would be needed to melt that ice and then raise the temperature of the resulting water to 20°C. The specific heat capacity of water and aluminium are 4200 J Kg ^-1 and 910 J Kg ^-1 respectively, and the latent heat of fusion of ice is... | g12749 | [
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0.004647696390748024,
0.0830681324005127,
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0.06305105239152908,
0.004925969056785107,
0.08063599467277527,
0.063677117228508,
-0.0216542... |
<p>After seeing this image:</p>
<p><a href="http://mynasadata.larc.nasa.gov/images/EM_Spectrum3-new.jpg" rel="nofollow">http://mynasadata.larc.nasa.gov/images/EM_Spectrum3-new.jpg</a></p>
<p>And reading this:</p>
<blockquote>
<p>"The long wavelength limit is the size of the universe itself, while it is thought tha... | g12750 | [
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0.013161782175302505,
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0... |
<p>Is there an accessible account of superfluidity in <a href="http://en.wikipedia.org/wiki/Helium-4" rel="nofollow">Helium-4</a> as a manifestation of "global gauge symmetry" breaking? </p>
<p>And what is meant by "global gauge symmetry"? I was taught that gauge symmetries were by definition local. Is it just a diffe... | g12751 | [
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0.040593259036540985,
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<p>What is currently the most plausible model of the universe regarding curvature, positive, negative or flat?</p>
<p>(I'm sorry if the answer is already out there, but I just can't seem to find it...)</p> | g12752 | [
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0.0693482905626297,
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0.08204036206007004,
... |
<p>If an explosion were to occur at any point on earth, how powerful would that explosion have to be for it to be audible or otherwise detectable by every person on the planet? Detection could mean either seeing or hearing the blast or feeling the tremors created by the shock wave.</p>
<p>Bonus question: is any such e... | g12753 | [
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<p>Given a manifold $M$, Arnold's "Mathematical Methods of Classical Mechanics" defines a Lagrangian system as a pair $(M,L)$ where $L$ is some smooth function on the tangent bundle $TM$. The function $L$ is called the Lagrangian. In the case when $M$ is a Riemannian manifold and a particle in $M$ is moving under some ... | g12754 | [
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<p>many textbooks tell me that Hamiltonians are constructed from Lagrangians like
$$L=L(q,\dot{q})$$
with a Legendre transformation to obtain the Hamiltonian as
$$H=\dot{q}\frac{\partial L}{\partial \dot{q}}-L$$
but none of the textbooks explain how this is done.</p>
<p>My specific problem is that I have Lagrangians t... | g12755 | [
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0.0247... |
<p>I was wondering how one would actually calculate how much oxygen would dissolve into water given the necessary initial conditions, and what those initial conditions would need to be. I assume they would be pressure, and initial concentration, but I really don't know where I would go from there. Clearly air and water... | g12756 | [
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0.018217531964182854,
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0.023029858246445656,
0.011570997536182404,
0.002... |
<p>Suppose we have a pair of entangled qubits.
$$
|\psi\rangle = \frac{1}{ \sqrt{2} } ( |00\rangle + |11\rangle )
$$</p>
<p>Now we give one qubit to Alice and other to Bob. Alice measure the her qubit to know the spin in z-direction and bob simultaneously measures the spin in x direction. </p>
<p>Since alice and bo... | g12757 | [
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<p>We have a screen with two slits (Young style) separated by a distance $d$, one of them receives a planar wave of $600nm$, the other receives a planar wave of $400nm$. Behind the slits there's a screen we observe.</p>
<p>Only with this, as the waves have different wavelengths, I guess there can't be any interference... | g12758 | [
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<p>I am reading about dielectric boundaries and electromagnetic plane waves following griffiths ch7. When considering a boundary at z=0 with electric fields perpendicular to the plane of incidence it states that the boundary condition,
$$
\left[ \frac{1}{\mu}(\textbf{k}\times \textbf{E}+\textbf{k}_{r}\times \textbf{E... | g12759 | [
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<p>I know that the reason why they stay in orbit but why do some move away from the earth(the moon) or come closer and eventually fall?
And why does the moon move away from earth?</p> | g12760 | [
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<p>Visitors of two public exhibitions A and B are equipped with compasses.</p>
<p><strong>Exhibition A:</strong></p>
<p>I want to guide these visitors along a certain path throughout the exhibition by "overriding" the earth magnetic field so that they can follow there compasses "north" along the path. The path where ... | g12761 | [
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... |
<p>I'm following a calculation done by a guy who's done it a bit different than what I've done before (used nearest neighbour vectors and a DFT instead of what I will show below), I'm not quite sure how to invert this expression he gives.</p>
<p>We are looking at formulating the tight binding picture for graphene, usi... | g12762 | [
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<blockquote>
<p>The magnetic field over a certain range is given by $\vec{B} = B_x\hat{\imath} + B_y\hat{\jmath}$, where $B_x= 4\: \mathrm{T}$ and $B_y= 2\: \mathrm{T}$. An electron moves into the field with a velocity $\vec{v} = v_x\hat{\imath}+v_y\hat{\jmath}+v_z\hat{k}$, where $v_x= 5\: \mathrm{m/s}$, $v_y= 8\: \m... | g12763 | [
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0.02763640135526657,
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0.1344691962003708,
-0.06418776512145996,
0.0799880251288414,
0.003027713391929865,
-0.03338269516825676,
0.044056281447410583,
-0.06917304545640945,
0.059182267636060715,
-0.030565336346626282,
-0.00732... |
<p>If we had the ability to make an actuator that could turn around at or past the speed of light and I attached a high miliwatt laser to it, then spun the laser around on the actuator at the speed of light, would the light beam bend act like a the stream of water from a spinning hose as the laser went around it?</p> | g12764 | [
-0.003342174692079425,
-0.061872366815805435,
0.006727552507072687,
0.0337911956012249,
-0.019197743386030197,
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0.03628229722380638,
0.025689048692584038,
0.0019450710387900472,
-0.05061152204871178,
0.016445504501461983,
0.059259217232465744,
0.007508284877985716,
0.0... |
<p>Is there a complete physics simulator that I can use to do general simulations for learning purposes? For example:</p>
<ol>
<li>Create a sandbox.</li>
<li>Fill with a gas.</li>
<li>Load a <a href="http://www.salemclock.com/weather/weatherglass_files/image001.jpg" rel="nofollow">3d solid model like this (but 3d)</a>... | g12765 | [
0.042451437562704086,
0.028283657506108284,
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0.00880961213260889,
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0.04861145094037056,
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0.04117545858025551,
-0.... |
<p>We are supposed to show that orbits in 4D are not closed.
Therefore I derived a Lagrangian in hyperspherical coordinates
$$L=\frac{m}{2}(\dot{r}^2+\sin^2(\gamma)(\sin^2(\theta)r^2 \dot{\phi}^2+r^2 \dot{\theta}^2)+r^2 \dot{\gamma}^2)-V(r).$$</p>
<p>But we are supposed to express the Lagrangian in terms of constant ... | g12766 | [
0.03148235008120537,
-0.031924765557050705,
-0.02154148370027542,
-0.06007958948612213,
-0.005882736761122942,
0.030147291719913483,
0.046676259487867355,
-0.006921806838363409,
-0.03291694447398186,
-0.009047691710293293,
-0.0420263409614563,
0.05630505084991455,
0.011959261260926723,
0.0... |
<p>I have this $2^n*2^n$ matrix that represent the evolution of a system of $n$ spin.
I know that I can have only one excited spin in my configuration a time.
(eg: 0110 nor 0101 ar not permitted, but 0100 it is)</p>
<p>$s_+$ is defined with $s_x+is_y$ and $s_-$ is defined with $s_x-is_y$
(creation and annichilation ... | g12767 | [
-0.017600813880562782,
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-0.00029426312539726496,
0.024825192987918854,
-0.007361814379692078,
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0.06683363765478134,
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0.02114102616906166,
-0.050594180822372437,
0.027862118557095528,
0.023839285597205162,
... |
<p>Given a <a href="http://en.wikipedia.org/wiki/Pseudo-Riemannian_manifold#Definition" rel="nofollow"><i>Lorentzian manifold and metric tensor</i>, "$( M, g )$"</a>, the corresponding <a href="http://en.wikipedia.org/wiki/Causal_structure#Causal_relations" rel="nofollow"><i>causal relations</i></a> between its element... | g12768 | [
0.03592145815491676,
-0.01154133677482605,
0.0006989887333475053,
-0.010458282195031643,
0.002142779529094696,
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0.07458612322807312,
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0.033442456275224686,
-0.017838288098573685,
0.009245941415429115,
0.020779810845851898,
0.02986057475209236,
-... |
<p>I seem to have forgotten how to solve Laplace's equation when there is a Yukawa mass $\mu$. I want to find the Yukawa potential due to a homogeneously charged sphere of radius $R$ and charge density $\rho$.</p>
<p><strong>My attempt</strong></p>
<p>I need to solve $(\nabla^2-\mu^2)\phi = -\rho$ inside and outside... | g12769 | [
0.025799423456192017,
0.009098532609641552,
-0.004137022886425257,
-0.02880752645432949,
0.012770470231771469,
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0.04409044235944748,
0.01832892931997776,
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0.0357573963701725,
-0.0329853817820549,
-0.0014067402807995677,
0.034553416073322296,
0.04933... |
<p>I'm a student of mathematics with not much background in physics. I'm interested in learning Quantum field theory from a mathematical point of view.</p>
<p>Are there any good books or other reference material which can help in learning about quantum field theory?
What areas of mathematics should I be familiar with ... | g12770 | [
0.02970684878528118,
0.03801785409450531,
0.025307483971118927,
-0.0061509329825639725,
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0.029832130298018456,
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0.012726323679089546,
0.01597682386636734,
0.011635835282504559,
-0.010129454545676708,
0.... |
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