question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
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<p>This question arose while reading Peskin and Schroeder, specifically, it arose in regards to the sum of diagrams above their Eq. (10.20) on pg. 326.</p>
<p>The context is $\phi ^4$ theory and they are using a vertex renormalization condition to compute the counterterm $\delta _\lambda$ corresponding to the coupling... | g12587 | [
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<p>I am having trouble reconciling two facts I am aware of: the fact that the charge conjugate of a spinor tranforms in the same representation as the original spinor, and the fact that (in certain, dimensions, in particular, in $D=4$), the charge conjugate of a left-handed spinor is right-handed, and vice versa.</p>
... | g12588 | [
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<p>In the weakly-coupled BCS regime two-dimensional chiral (p+ip) spinless superconductors and superfluids posses a chiral gapless fermionic Majorana state localized near the boundary. This gapless edge mode is a direct manifestation of the topological quantum phase transition present in this system. Indeed the boundar... | g12589 | [
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<p>The question is</p>
<blockquote>
<p>In a combat exercise, a mortar at M is required to hit a target at O, which is taking cover 25 m behind a structure of negligible width 10 m tall. This mortar can only fire at an angle of 45 degrees to the horizontal, but can fire shells of any velocity. Find the minimum initia... | g12590 | [
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<p>Fish achieve neutral buoyancy (so they don't have to swim constantly to stay in place) via a swim bladder. A swim bladder is a little internal sack that they can inflate/deflate with air, which changes their volume but not their total mass. To see how this allows them to change their buoyancy, let's consider the sit... | g12591 | [
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<p>I have a few related questions about static electricity and conductors.
1. when we say static electric field inside a conductor is zero, let us take an example of two concentric conductors, outer one positively charged and inner negative charged -- inside inner sphere field will be zero, but there will be field dire... | g12592 | [
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<p>The problem provided by my professor goes as follows:
"Now consider a situation in which all charges are equal to q and they simultaneously become "unglued". What speed will each charge have when a hexagonal configuration has doubled in size (each side has a length).
The work done was found to be $$U=\frac{kq^2}a\le... | g12593 | [
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<p>In a classic demonstration of inducing a charge on a dielectric, the latter is exposed to an external field. There is a resulting charge separation in the dielectric. What is the velocity of propagation of this charge separation? Is it the velocity of electromagnetic waves in the dielectric i.e. "the speed of light"... | g12594 | [
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<p>So is it possbile to build a system from lenses and mirrors that can make faint gas nebulas brighter or can be used as nightvision? </p>
<p>If you increase the size of the aperture of a telescope it will collect more light, but the exit pupil will be also bigger, so not all light will enter the eye.</p>
<p>In orde... | g12595 | [
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<p>In section 134 of Vol. 3 (Quantum Mechanics), Landau and Lifshitz make the energy complex in order to describe a particle that can decay:</p>
<p>$E = E_0 - \frac{1}{2}i \Gamma$</p>
<p>The propagator $U(t) = \exp(-i H t)$ then makes the wavefunction die exponentially with time. But also, $H$ is non-Hermitian.</p>
... | g12596 | [
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<p>An hourglass H weighs h. When it's placed on a scale with all the sand rested in the lower portion, the scale reads weight x where x = h.</p>
<p>Now, if you turn the hourglass upside down to let the sand start to flow down, what does the scale read?</p>
<p>I imagine initially, when the sand starts to fall but befo... | g12597 | [
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<p>Suppose there is a slanted capillary tube and a fluid rises in it. Why does the fluid rise to the same vertical height as when the tube is perfectly vertical?</p>
<p>If I'm right surface tension force balances the weight of the lifted fluid. But in the case of a slanted tube, more fluid will be lifted and thus weig... | g12598 | [
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<p>Can solar furnace achieve higher temperature than sun surface?</p>
<p>I guess not, but I'm not sure about that. Can you check my reasoning:</p>
<p>-------- My reasoning -----------</p>
<p>Consider Sun as a black body and (almost) Lambertian radiator. If there would be an optical system which can focus <strong><em... | g398 | [
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<p>I'll a appreciate a layman's explanation, if there exists one, to this question that arose when reading an popular-science level article on Einstein and the $E=MC^2$ equation.</p>
<p>What I mean is that, why is the product of the reaction <strong>not</strong> an electrically neutral doublet of mass $2M_e$ (= 1.022 ... | g12599 | [
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<p>Jupiter has many <a href="http://en.wikipedia.org/wiki/Jupiter_Trojan" rel="nofollow">Trojan asteroids</a> located at Lagrangian points L4 and L5 and <a href="http://en.wikipedia.org/wiki/Hilda_family" rel="nofollow">Hilda asteroids</a> dispersed between points L3, L4, and L5.</p>
<p>Does the Earth have similar ast... | g12600 | [
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<p>This is a two part question about the technology described here:</p>
<p><a href="http://www.engadget.com/2011/06/22/light-field-camera-captures-unprecedented-images-lets-you-cho/" rel="nofollow">Lytro's light field camera lets you choose focus later</a></p>
<ol>
<li>I'd love to get an explanation of the technology... | g12601 | [
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<p>This article is certainly an interesting alternative perspective, but is it factual or does it contain fallacies?</p>
<p><a href="http://www.circlon-theory.com/HTML/EmcFallacies.html" rel="nofollow">http://www.circlon-theory.com/HTML/EmcFallacies.html</a></p>
<p>Are mass and energy not convertible after all? Do ph... | g12602 | [
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<p>the question is: </p>
<p>A ball is thrown directly downward with an initial speed of 8.00m/s from a height of 30.0m. After what time interval does it strike the ground.</p>
<p>so i went through the problem and got the answer 1.79 sec.
but after reviewing some notes from my teacher, I got the idea that in equation... | g12603 | [
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<p>I've been racking my brain over this, and I can't find any clues in my textbook as to how to approach it.</p>
<p>I have the following circuit:</p>
<p><img src="http://i.stack.imgur.com/SaOrc.png" alt="enter image description here"></p>
<p>My goal is to find R such that, <strong>right after the switch is unplugged... | g12604 | [
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<p>I'm trying to model the behaviour of aerosols in response to blast waves. (This is for visual effects.)</p>
<p>Intuitively, if a flare left a smoke trail above a field and then a bomb detonated elsewhere in the field, one would expect the smoke to be dispersed, to a degree varying with the bomb's energy (among oth... | g12605 | [
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<p>A star is probably visible/detected by it's radiation. But that star may or may not belong to our own galaxy ... yet news reports speak of detecting a star/nova in a distant galaxy. </p>
<p>How does one determine whether the star she/he views belongs to Milky Way, or some other galaxy ... or is galactic orphan? Is ... | g12606 | [
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<p>What is the phase difference of the oscillation of a tuning fork? </p> | g399 | [
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<p>I have two questions regarding (possibly counter intuitive results) Schrodinger equation and its application to two (strictly hypothetical) scenarios.</p>
<ol>
<li><p>Consider the 1D potential $V(x) = - \frac{\alpha}{|x|}$, which is an attractive one. As it is attractive, after a sufficiently large amount of time I... | g12607 | [
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<p>I have a question concerning the Faddeev-Popov ghost boundary conditions in the path integral quantization of bosonic strings. My ghost action is:</p>
<p>$S_g= - \frac{i}{2\pi} \int d^2 \xi \sqrt{-h} \; b_{ab} \nabla^a c^b$</p>
<p>I can derive the equations of motion, but I cannot see the boundary conditions of th... | g12608 | [
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<p>How to calculate work when a block is moving with constant velocity?
As we know $f=ma$, and for constant velocity $a=0$, so $f=0$ and $w=fs=0$? Can anybody make it clear?</p> | g12609 | [
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<p>I am trying to understand net force intuitively and this is what I think.</p>
<blockquote>
<p>If a net force is towards the positive $x$ direction, which of the following is true ?</p>
<p><strong>a)</strong> It can be moving in the negative $x$ direction</p>
<p><strong>b)</strong> It can be speeding up<... | g12610 | [
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<p>Assume that we have some non-constant electric field $E(x,t)$ and a point-dipole at a position $q$ with a constant dipole moment $\vec{p}$. How would you describe the time evolution, i.e. the motion of such a dipole?</p> | g12611 | [
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<p>I need to implement a random force in my code according to the fluctuation dissipation theorem. I have a Gaussian distribution function ready width average 0 and distribution 1 and I know I need to multiply it by something but I'm not sure what. The fluctuation dissipation theorem gives (in one dimension):</p>
<p>$... | g12612 | [
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<p>I conducted an experiment , i put a silver foil on a a CRT TV , then i open the TV, charging the foil (acting like a capacitor plate), if i approach a grounded rod to it , it will discharge with a spark of about 1.8 cm length , which is equivalent to about 18 kV.
What i am really interested in is once that spark goe... | g12613 | [
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<p>Do electrons move randomly, with no preference of directions?
And why electrons don't fall into the nucleus? About this question, I read the article on Chemistry wiki, which says that when electron falls towards nucleus, its kinetic energy becomes extremely large so there is a battle between electrons and nucleus, a... | g132 | [
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<p>For a very long time now, I've been thinking about the <a href="http://en.wikipedia.org/wiki/Drude_model" rel="nofollow">Drude Model</a> derivation of Ohm's Law. I know that a rigorous derivation requires a Quantum Mechanical approach. However, the mere fact that the Drude Model churns out the right equation seems t... | g12614 | [
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0.02297235280275345,
0.032... |
<p>I am studying classical Maxwell fields and I am stuck on this differentiating part. How can I derive the result given below ?</p>
<p>$$\dfrac{\partial}{\partial(\partial A_{\mu}/\partial x_{\nu})} \left(2\dfrac{\partial A_{\sigma}}{\partial x_{\lambda}}\dfrac{\partial A_{\sigma}}{\partial x_{\lambda}}-2\dfrac{\part... | g12615 | [
0.01764935441315174,
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<p>Let me set up the notation I am using. $(abc,de)$ denotes the standard Young tableau where the first row is $abc$ and the second row is $de$. Each young tableau corresponds to the young symmetriser, and I use the convention that given the Young tableau $\lambda$ young symmetriser is given by,</p>
<p>$P_{\lambda} = ... | g12616 | [
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<p>Prompted by <a href="http://math.stackexchange.com/questions/96331/in-russian-roulette-is-it-best-to-go-first">this discussion on the math exchange</a></p>
<p>My thought was that the added mass of a bullet in an otherwise empty revolver would bias the chamber spin such that the bullet would remain in one of the low... | g12617 | [
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0.022657182067632675,
-0.... |
<p>I am not seeing the "big picture" here. If I have two conducting spheres separated by a long conducting wire, why would the spheres share the same electric potential?</p>
<p>I think of the spheres as point charges, what does the conducting wire do? The $E$ field inside the conducting wire is 0, so what is it really... | g12618 | [
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<p>In "introductory Quantum Optics", by Gerry and Knight, the Jeynes model is considered. In this model of electron-EM field interaction the electron is approximated by a two state system ($\lvert g\rangle$ and $\lvert e\rangle$), and the form of the dipole operator $\hat{d}$ is said to be constrained by parity conside... | g12619 | [
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<p>i) Do people use axial gauge with a $\xi$ term? When $\xi\neq 0$, ghosts do not decouple, but maybe it's still useful?</p>
<p>ii) Is it proved that the term $\frac 1 {2\xi}(n.A)^2$ in the Lagrangian does not renormalize, for $\xi=0$ and $\xi\neq 0$?</p> | g12620 | [
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<p>I keep on hearing that magnetism is just another form of electricity and vice versa. If that's the case why can't we use magnets as batteries, and why aren't my batteries magnetic?</p> | g12621 | [
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<p>The displacement current is due to changing electric field. Since, after the capacitor gets fully charged there is no changing electric field there is no displacement current.(capacitor connected to a DC voltage input) This is my understanding. Please correct me if I'm wrong.</p> | g12622 | [
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<p>Why is the <a href="http://en.wikipedia.org/wiki/Gravitational_constant" rel="nofollow">Gravitational constant</a> about $10^{23}$ times of the <a href="http://en.wikipedia.org/wiki/Planck_constant" rel="nofollow">Planck constant</a> in SI-units? Is there any relation between them?
I mean Planck constant is about $6... | g12623 | [
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<p>Ref. 1, page 15, equation (23) defines the $U(1)_V$ and $U(1)_A$ actions as $$e^{i\alpha F_V}: \Phi(x,\theta^{\pm},\bar{\theta}^{\pm}) \rightarrow e^{i\alpha q_V}: \Phi(x,e^{-i\alpha }\theta^{\pm},e^{i\alpha }\bar{\theta}^{\pm}) $$
The superfield can be written as $$\Phi(x,\theta^{\pm},\bar{\theta}^{\pm}) =x+\theta^... | g12624 | [
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<p>Quarks have the unusual characteristic of having a fractional electric charge.
here there is a new model that suggests maybe an up Quark has no electric charge and infact down Quark has electric charge of (+1,-1), through weak interaction between Up Quark and W$^{\pm}$</p>
<p>$$u^{0}+W^{+}\to d^{+},$$
$$u^{0}+W^{-}... | g400 | [
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<p><strong>Question:</strong> Which of the following affect the frequency of a tuning fork?</p>
<ul>
<li>Tine stiffness</li>
<li>Tine length</li>
<li>The force with which it's struck</li>
<li>Density of the surrounding air</li>
<li>Temperature of the surrounding air</li>
</ul>
<p><strong>Answer Attempt:</strong> Base... | g12625 | [
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<p>If an object is designed to cope with large forces such as tension, would removing these forces risk damaging the object?</p>
<p>For example: The neck of a guitar is built to handle the tension of steel strings (~800 Newtons),
if you removed/reduced the tension (removed the strings) for a long period of time would ... | g12626 | [
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<p>In this question I am talking about the following situation:</p>
<p><img src="http://i.stack.imgur.com/Q4brH.gif" alt="enter image description here"></p>
<p>Now, I know that the max kinetic energy of the electrons emitted is</p>
<p>$KE_{max} = h\nu - e\phi_{em}$</p>
<p>where $\phi_{em}$ is the work function of t... | g12627 | [
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0.029724... |
<p>The title really says it all. One follow-up question is: How could one falsify this?</p> | g12628 | [
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<p>Due to increase in forward bias voltage, the intensity of light increases but after a particular value the intensity decreases. Why?</p> | g12629 | [
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<p>In an extrinsic semiconductor the electric potential is:
$$\phi = \frac{1}{q}(E_{\mathrm{F}} - E_{\mathrm{Fi}})$$
where $E_{\mathrm{F}}$ is the Fermi energy, $E_{\mathrm{Fi}}$ is the intrinsic Fermi energy, $q$ is the electron charge and $\phi$ is the electric potential. I am not sure where this equation comes from.... | g12630 | [
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0.004... |
<p>I am sure all of us have played with rubbing things and producing static electricity and when I was charging my comb by rubbing it on my hair and watching it attracting a small piece of paper, I heard a very feeble noise just like an electric buzz sound. I could feel the electron "cloud" all around the comb and the ... | g12631 | [
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<p>for example, i have a vague notion that the actual answer is that the permittivity and permisivity are different in each different material, so all waves refract at every boundary, but we only call it that if it makes it out with any real magnitude left which depends on the skin depth or something like that, but is ... | g12632 | [
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0.0... |
<p>If we ignore 5GHz WiFi, then both microwaves and WiFi create photons at ~2.4GHz but one of them will boil water in a few seconds but the other doesn't have any effect. So what's the difference?</p>
<p>Is it simply the number of photons created? Is that what the wattage of a microwave measures? If so, what would be ... | g230 | [
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<p>Imagine a following thought experiment.</p>
<p>Suppose we have a large amount of entangled particle pairs, several million or billion.
Now suppose there are two observers, each carrying one member of particle pair - a slower-then-light spaceship and mission control on Earth, for example.</p>
<p>Before departure, b... | g12633 | [
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<p>In an electron multiplier (discrete dynode detector), one electron triggers the release of more electrons in a cascade.</p>
<p>Is it possible that a "large" number of electrons hitting the detector can temporarily (course of hours) reduce the number of electrons available to amplify future incident electrons? (E.g.... | g12634 | [
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<p>I'm trying to understand the basics of <a href="http://en.wikipedia.org/wiki/Anyon" rel="nofollow">anyons</a> physics. I understand there is neither a Fock space they live in (because Fock is just the space of (anti-)symmetrized tensor product state, see <em>e.g.</em> <a href="http://en.wikipedia.org/wiki/Fock_space... | g12635 | [
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0.01833309233188629,
0.0... |
<p>I'm trying understand how to rotate Dirac fields to absorb complex phases in masses. I have a few related questions:</p>
<ol>
<li><p>With Weyl spinors, I understand, $$ \mathcal{L} = \text{kinetic} +
|M|e^{i\theta}\xi\chi + \textrm{h.c.} $$ The phase removed by separate
left- and right-handed rotations, e.g. $\... | g12636 | [
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0.006857207510620356,
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-0.0... |
<p>How is <a href="http://en.wikipedia.org/wiki/Fermat%27s_principle" rel="nofollow">Fermat's least time principle</a> proven? Or it is what usually is observed and is basis for the theories?</p> | g12637 | [
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<p>Is the particle entanglement a boolean property? That is, when we consider two given particles, is the answer to the question "are they entangled" always either "yes" or "no" (or, of course, "we are not sure if it's yes or no")? Is there such thing as partial entanglement?</p> | g12638 | [
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<p>Let's have Schrodinger equation or Dirac equation in Schrodinger form:
$$
i \partial_{0}\Psi = \hat {H}\Psi .
$$
Sometimes we can introduce some operators $\hat {A}, \hat {B}$ (the second is not always Hermitian conjugate to the first) for which
$$
\hat {H} = \hat {B}\hat {A} + \varepsilon ,
$$
which is look like re... | g12639 | [
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-0.02653028443455696,
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0.021372489631175995,
0.026... |
<p>Is there a general systematic procedure or approach to obtain the analytic functions $c_{ijk}$
as well as the corresponding operators $$A_i(z)$$ that appear in the operator product expansion (OPE)</p>
<p>$$
A_i(z)A_j(w) = \sum\limits_k c_{ijk}(z-w)A_k(w)
$$</p>
<p>for any given two operators $A_i(z)$ and $A_i(z)$?... | g12640 | [
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0.... |
<p>If the sun is the hottest known thing to humans is it possible to have a temperature greater than the sun?</p> | g12641 | [
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<p>As a condensed matter physicist, I take it for granted that a Fermi surface is <em>stable</em>.</p>
<p>But it is stable with respect to what? </p>
<p>For instance, Cooper pairing is known as an instability of the Fermi surface.</p>
<p>I'm simply wondering what makes the Fermi surface stable? </p>
<p>Possible way... | g12642 | [
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<p>In "String theory and M-theory" (K. Becker, M. Becker and H.Schwarz) page 81, they said that among the background fields, the fields associated with massless bosonic fields are especially significant. My question is, why is that? What's the most general form for the action in bosonic string theory with background th... | g12643 | [
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0.04748614877462387,
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0.0262... |
<p>In history class in elementary school I remember learning that the Greeks would build their stone columns hollow because they thought this provided more support. Is it true that a hollow column is stronger? Thanks!</p> | g12644 | [
0.038777660578489304,
0.01919778622686863,
0.01177531573921442,
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0.0754653587937355,
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0.015117461793124676,
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0.010418047197163105,
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<p>What I know so far:
- Charges (electrons) inside a conductor will repel (Coulomb's law).
- The charges will experience repulsion which results in maximum separation distances between the charges.
- The charges will then redistribute along the surface of the conductor in order to achieve electrostatic equilibrium (ie... | g12645 | [
0.02956485003232956,
0.07275697588920593,
0.005095803644508123,
0.02060697227716446,
0.10196778923273087,
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0.009277451783418655,
-0.07546962797641754,
-0.029155174270272255,
-0.03925308957695961,
-0.03... |
<p>Consider the ray model of light. Let's say an object such as a pencil is illuminated, and consider one point on that pencil. Since there could be many rays of light bouncing off the same point on the pencil, one ray could hit the left side of your eye and another ray from the same point could hit the right side of t... | g12646 | [
0.004040543921291828,
0.026384396478533745,
0.01332174427807331,
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-0.029553329572081566,
0.0566139854490757,
0.032292213290929794,
0.07648614794015884,
-0.016... |
<p>The drag force on a spherical body according to <a href="http://en.wikipedia.org/wiki/Stokes%27_law" rel="nofollow">Stokes' law</a> is given by</p>
<p>$$F = 6π\mu rv$$
Where $\mu$ is the dynamic viscosity of the fluid, $r$ is the radius of the spherical object, and $v$ is its velocity.</p>
<p>At low speeds, the dr... | g401 | [
0.06613041460514069,
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0.021858705207705498,
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<p>The correlation function g1 is pretty easy to understand and the relation to young's double slit experiment is also clear to me. </p>
<p>In every quantum optics book I read so far correlation functions $g^n(x_1, ... , x_{2n})$ of an order greater than 1 are defined, but not related to an experiment or explained any... | g12647 | [
0.004370059352368116,
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0.04168272390961647,
0.038773223757743835,
... |
<p>For example, consider the $\phi^3$ theory in $d=8$, with Lagrangian: </p>
<p>$\mathcal{L}=\frac{1}{2}\partial_{\mu}\phi\partial^{\mu}\phi-\frac{1}{2}m^{2}\phi^{2}-\frac{1}{3!}\lambda_{3}\phi^{3}$.</p>
<p>In 8 dimensions, the box diagram now diverges. We would need to add a $\lambda_{4}\phi^{4}$ coupling to our Lag... | g12648 | [
0.07731213420629501,
0.028554633259773254,
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0.... |
<p>There is a question regarding basic physical understanding. Assume you have a mass point (or just a ball if you like) that is constrained on a line. You know that at $t=0$ its position is $0$, i.e., $x(t=0)=0$, same for its velocity, i.e., $\dot{x}(t=0)=0$, its acceleration, $\ddot{x}(t=0)=0$, its rate of change of ... | g12649 | [
0.032529592514038086,
0.025422675535082817,
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0.0136481374502182,
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0.08220356702804565,
-0.016... |
<p>I can't really understand why two higgs doublets are required in SUSY. </p>
<p>From the literature, I have found opaque explanations that say something along the lines of: the superpotential W must be a holomorphic function of the chiral supermutiplets and thus we need to introduce another chiral supermutiplet.</p>... | g12650 | [
0.033300019800662994,
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<p>If gravity can be thought of as both a wave (the gravitational wave, as predicted to exist by Albert Einstein and certain calculations) and a particle (the graviton), would it make sense to apply quantum mechanics (which I understand only applies to mass/energy) and therefore wavefunction collapse to gravity? In oth... | g12651 | [
0.026602551341056824,
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0.03127053380012512,
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0.0603138767182827,
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<ol>
<li><p>What is <a href="http://en.wikipedia.org/wiki/Background_independence" rel="nofollow">background independence</a> and how important is it?</p></li>
<li><p>In order to be a theory of everything, will the final string-theory/m-theory have to be background independent? </p></li>
<li><p>Does the current lack of... | g12652 | [
0.014247231185436249,
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0.021144812926650047,
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0.03700235113501549,
0.020940113812685013,
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-0.007679719477891922,
0.01789562590420246,
0.02078867517411709,
0.023196183145046234,
0.0... |
<p>Can all of the predictions made in <a href="http://en.wikipedia.org/wiki/Special_relativity" rel="nofollow">Special Relativity</a> (SR) also be made in <a href="http://en.wikipedia.org/wiki/General_relativity" rel="nofollow">General Relativity</a> (GR)?</p> | g12653 | [
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<p>One of the major reasons SUSY was adopted in particle physics is to Naturally have a Higgs boson (a fundamental scalar) at the weak scale. </p>
<p>If we abandon this argument, what other motivation for low-scale ($\mathcal{O(1)}$ TeV) SUSY exists? </p> | g12654 | [
0.03107580728828907,
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0.08737... |
<p>I understand (supposedly) the mathematics concerning the relativity of simultaneity in Special Relativity, but I have a nagging question regarding the original example given by Einstein supporting it (I'm only disagreeing with this specific example, not the concept).</p>
<p>It is normally given as a person on an em... | g12655 | [
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<p>I'm now studying Quantum Mechanics, and I took a course on Vibration and Waves last year.
I have been trying to make an analogy between classical and the quantum waves.
Is it true that both the modes of a quantum and classical wave can not be excited individually?</p>
<p>Whenever you pluck a classical string, its ... | g12656 | [
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0.013494118116796017,
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0.006906774826347828,
0.... |
<p>In non-relativistic QM, does it make a difference if an energy shift is applied to the systems's Lagrangian or Hamiltonian?</p> | g402 | [
0.031505078077316284,
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0.005028356797993183,
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0.0393357090651989,
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0.009153462946414948,
0.011163721792399883,
0.030451523140072823,
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0.0... |
<p>I've seen many applications of topology in Quantum Mechanics (topological insulators, quantum Hall effects, TQFT, etc.) Does any of these phenomena have anything in common?</p>
<p>Is there any intuitive explanation of why topology is so important? </p>
<p>Is there a similar application of topology in Classical Me... | g12657 | [
0.035004571080207825,
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0.04839088022708893,
0.0189... |
<p>After working in air fed suits,operatives are required to give samples from their nasal passages by blowing their nose into a tissue,which is then counted in a noseblow counter. How does this work?</p> | g12658 | [
0.00014804763486608863,
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0.018246768042445183,
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0.002214775187894702,
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0.03163808956742287,... |
<p>When matter is condensed the mass stays the same and we also know that only the volume and density are the only other two effected variables. But is there a point in which the matter cannot condense anymore? Or a point in which the volume cannot decrease anymore?</p> | g12659 | [
0.02056107670068741,
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0.03316742926836014,
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<p>Let's imagine that there is a lamp on the floor. There is a dice on that same floor casting a shadow from our light source, the lamp. Why is it that there are different shades of the shadow phasing from darkest to dullest (darkest being closest to dice and dullest being farthest)?</p> | g12660 | [
-0.012332978658378124,
0.007358618546277285,
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0.0439426563680172,
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0.0525... |
<p>Let's say I have two planets that are one hundred thousand lightyears away from each other. I and my immortal friend on the other planet want to communicate, with a strong laser and a tachyon communication device.</p>
<p>I record a message on the tachyon communication device and release the message at exactly the s... | g12661 | [
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0.02529263310134411,
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0.04286670312285423,
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0.008470166474580765,
0.03210265561938286,
0.02127... |
<p>Is it theoretically possible to create some system such that the energy distribution creates a gravitational potential offset from its center of mass (or energy?) so that the body continually 'falls' into its own potential (i.e., as the body moves, the center of the potential moves with it such that it constantly fa... | g12662 | [
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<p>The wiki article states that <a href="http://en.wikipedia.org/wiki/D%27Alembert%27s_principle" rel="nofollow">D'Alembert's Principle</a> cannot derived from Newton's Laws alone and must stated as a postulate. Can someone explain why this is? It seems to me a rather obvious principle.</p> | g12663 | [
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<p>First let me clarify what I mean by vacuum.</p>
<p>Suppose we are concerned with a theory of fields $\phi ^i$ defined on a stationary globally hyperbolic spacetime $M$ (I want the spacetime to be stationary so that I have a canonical choice of time-derivative and I want the spacetime to have a Cauchy surface so tha... | g12664 | [
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0.0645... |
<p>What equations to use on this system to form a matrix $A$ with dimensions $[n,n]$ and load vector $q$ with dimension $[n]$ ? I am trying to get vertical displacement $w$.</p>
<p>$$w = A^{-1}\times q$$</p>
<p>Boundary conditions are as follows:
$$w(o) = 0 $$
$$w(L) = 0 $$
$$\phi(o) = 0$$
$$\phi(L) = 0$$
It is becou... | g12665 | [
0.06160896271467209,
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0.007369298487901688,
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-0.05432868003845215,
-... |
<p>What are the ways electrostatic charged objects leak charge in humid conditions?</p>
<p>Can airborne particles pick up charge by contact, then be repelled hence removing charge? If so would it be a significant factor?</p> | g12666 | [
0.055089496076107025,
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0... |
<p>Lets say I have two cars.<br>
They are identical in every way, except that Car A has a normal breaking system, where most of the breaking power is inflicted on the front wheels, and some on the back, and Car B has a breaking system where all of the power is inflicted on the front wheels and none on the back. </p>
... | g12667 | [
0.055674873292446136,
0.022258151322603226,
0.030764557421207428,
0.006616381928324699,
0.02605588734149933,
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0.026545213535428047,
0.012750601395964622,
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<p>Imagine $N$ oscillators with only two possible energies, $\epsilon_0$ and $ \epsilon_1$, with $\epsilon_1 > \epsilon_0$. Taking $\epsilon_0 = 0$ for now</p>
<p>I showed $\Omega(q\epsilon_1) = \frac{N!}{(N-q)!q!}$ and then</p>
<p>$$\frac{\partial S}{\partial q} = k \log(N/q - 1) $$</p>
<p>How can I use the abo... | g12668 | [
-0.021469980478286743,
0.027181465178728104,
-0.01522170752286911,
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0.04924224689602852,
0.04680657014250755,
0.0... |
<p>Why is the light speed a limit? Why can't anything go faster than light? Not even a single atom?</p> | g109 | [
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0.10094331949949265,
0.017706384882330894,
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0.0653209239244461,
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0.0195... |
<p>Is there a fast and convenient way of calculating the neutron stopping power of materials, consisting of multiple elements (e.g. doped crystals) without the need for Monte Carlo Simulation, that is more exact than simple cross-section additivity?</p> | g12669 | [
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0.030390173196792603,
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... |
<p>In the Shockley diode equation, why the exponential $\exp$ and the ideality factor $n$ are there? What do they represent & what is their significance?</p>
<p>I have to work on Solar Photovoltaics, and I need to understand the <a href="http://en.wikipedia.org/wiki/Diode#Shockley_diode_equation" rel="nofollow">S... | g12670 | [
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0.03374551236629486,
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0.0313824787735939,
0.07700669020414352,
0.05304... |
<p>I've been attempting to calculate how much torque a motor needs to produce in order to start a stationary object on wheels moving. (The torque is being applied to the rear 2 wheels, the front 2 are on bearings.)</p>
<p>I keep seeing Torque = Force * Radius (of the torqued wheel). I can't figure out how to calculate... | g267 | [
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0.0... |
<p>Plenty of research activity in physics have been vigorously opposed by their opponents as pseudoscience or fringe science, while other research are mainstream. It is possible some topic is pseudoscience if the experts claim it is so, but they could potentially be biased. For the nonexperts out there, short of appeal... | g12671 | [
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<p>I'm having some trouble understand what the difference is between these two.
It seems as though there are kind of the same, but that spin-orbit coupling reduces to LS coupling under certain circumstances.</p>
<p>But, I can't seem to make sense of it. So I was hoping anyone could explain the difference briefly, and ... | g12672 | [
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<p>In my math course we're taught to solve PDE (partial derivative equations) like transport equation:
$$
c\frac{\partial u}{\partial x} +\frac{\partial u}{\partial t}~=~0.
$$</p>
<p>If $u(x,t)$ is the quantity transported and $c$ has speed dimension (according to my book), $\frac{\partial u}{\partial t}$ must be spee... | g12673 | [
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<p>When I was in school, I learned (from Democritus) that an atom was
similar to a solar system, with the nucleus being the sun, and the
electrons being the planets. Of course, there are some differences: </p>
<ul>
<li><p>The "sun" isn't a single entity, but a collection of protons and nuetrons. </p></li>
<li><p>Two... | g12674 | [
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<p>first my actual problem. then my try on improving the current way of solving this with the wish for feedback or even a solution :)</p>
<p>gpx file with lat/long, elevation and time. wanna calculate speed... easy! when visualizing the speed on a chart you would figure it needs a little smoothing. done you have a pre... | g12675 | [
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<p>Is it just a historical choice that both magnetic field and the Lorentz force equation include the speed of light?
I figure that whoever wrote up the equations (in cgs!) could have put both factors of $c$ in either the force equation, or have define the magnetic field as being smaller by a factor of c- but they did... | g12676 | [
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<p>We’re told that ‘all forces are gauge forces’. The process seems to start with the Lagrangian corresponding to a particle-type, then the application of a local gauge symmetry leading to the emergence of the force bosons via the associated symmetry group.</p>
<p>But where did <em>exactly four forces</em> come from? ... | g12677 | [
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-0... |
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