question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
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<p>I'm a pure mathematician by trade, and have been trying to teach myself A-level mechanics. (This <em>is not</em> homework, it is purely self-study.)</p>
<p>I've been working through the exercises and have come up against a stubborn problem. Here it is:</p>
<p><strong>Question</strong></p>
<p>A train of mass 150 t... | g13039 | [
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<p>I am wondering how to deal with an expression like
$$ \int d^4\theta \frac{1}{T + T^\dagger} \big( \dots \big) $$
If the denominator was of the form $1 + T + T^\dagger$, I could assume that $T \ll 1$ and expand the denominator in a Taylor series.</p>
<p>If more context helps, this expression pops up in $5D$ SuGra a... | g13040 | [
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<p>Since all the traditional "continuous" quantities like time, energy, momentum, etc. are taken to be quantized implying that derived quantities will also be quantized, I was wondering if Quantum Physicists agree upon any quantity not being quantized?
I couldn't think of a single thing, until I came across this: <a hr... | g13041 | [
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<blockquote>
<p>A ball of mass $0.37\text{ kg}$ is thrown upward along the vertical with a initial speed of $14\text{ m/s}$, and reaches a maximum height of $8.4\text{ m}$.</p>
<p>a) What is the work done by air resistance on the ball? </p>
</blockquote>
<p>I came up with</p>
<p>$$F \times\text{Distance}(8.4)... | g13042 | [
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<p>Can someone tell me what does it 20-30% collision centrality mean in terms of impact parameter b?</p> | g13043 | [
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<p>Distant galaxies are said to be moving away from the Milky Way (and us) at speeds approaching the speed of light. Since Special Relativity tells us that any object moving away from us at a velocity of near the speed of light will increase in mass in our observations, i.e. it will appear to be much more massive than ... | g13044 | [
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<p>Please explain as simply as possible what the Hubbard-Holtstein model is and what it is used for.</p> | g13045 | [
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<p>I am going through <a href="http://arxiv.org/pdf/1202.2556v1.pdf" rel="nofollow">CURVATURE OF SPIN NETWORKS</a> by Jonckheere et al. The first line of the abstract mentions XX coupling and Heisenberg coupling. What is the difference between these two couplings?</p> | g13046 | [
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<p>is there any way to make electromagnetic waves reach a cell phone in faraday cage although conductor surround cell phone everywhere , can we pass current through conductor to make charges move as a trick then if electromagnetic field reach the conductor then no charge can prevent electric field as they are mobile no... | g13047 | [
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<p>I presume the answer is that it depends on the mass and size of the star and black hole, but I was wondering if somebody could provide some rough bounds (e.g. hours vs thousands of years).</p>
<p>By "eating" I mean the time it takes a star to go through the event horizon of the black hole, although maybe there are... | g13048 | [
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<p>I realize this question is very broad but may be I will still get a helpful answers. References and textbooks for the development of the technical and mathematical aspects of QFT abound. However, I never came across a source dealing with the conceptual issues of QFT. I am interested in stuff like, </p>
<ul>
<li><p>... | g13049 | [
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<p>I was reading a book on the history of Quantum Mechanics and I got intrigued by the <em>gendankenexperiment</em> proposed by Einstein to Bohr at the 6th Solvay conference in 1930.</p>
<p>For context, the thought experiment is a failed attempt by Einstein to disprove Heisenberg's Uncertainty Principle.</p>
<p><img ... | g13050 | [
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<p><a href="http://blogs.discovermagazine.com/badastronomy/2011/04/05/astronomers-may-have-witnessed-a-star-torn-apart-by-a-black-hole/">http://blogs.discovermagazine.com/badastronomy/2011/04/05/astronomers-may-have-witnessed-a-star-torn-apart-by-a-black-hole/</a></p>
<p>A lot of the star in the disc, a lot of the sta... | g13051 | [
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<p>In a photon gas, we know that pressure, $P$, and energy density, $u$, are related by:
$$P=\frac{u}{3}$$
We also know from relativity that the momentum of a photon is
$$p=\frac{E}{c}$$</p>
<p>Finally, the pressure can usually be thought of as the flux of momentum through a surface, but that would imply that the flux... | g13052 | [
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<p>Having a <code>2D map</code> filled <code>uniformly by random values</code> (<em>Figure:top-left</em>) to demonstrate a disordered phenomena, the next maps are kernel averaged with a kernel of sizes 3x3, 5x5, ..., 11x11.<br>
<strong>The questions are:</strong><br>
What are the patterns appeared in the kernel average... | g13053 | [
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<p>The cause of surface tension is said to be asymmetry in the forces experienced by the molecules at the surface due to different interactions with air and liquid, but then the same argument also applies for all other surfaces, where the fluid is in contact with the container then why isn't all strange surface tension... | g13054 | [
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<p>James Joule established that all forms of energy were basically the same and interchangeable. My question is if thas law is relevant in particle physics. Can a positive charge and a negative charge be interchangeable? Will the force carrying particles allow it?</p> | g13055 | [
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<p>How would you go about finding the natural frequencies of solid materials like wood (e.g., teak, pine), stone (e.g., marble, granite) liquid, etc?</p> | g13056 | [
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<p>Is there a repository where one can find unpolarized nuclear Compton scattering data $\gamma (Z,N)\rightarrow \gamma (Z,N)$ for specific nuclei $(Z,N)$? or even some parametrization of structure functions that loosely follows the data? </p> | g13057 | [
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<p>How is the black hole complementarity version of the holographic principle derived from path integrals and/or string theory? That has never been obvious to me. Can someone show me how to do it step by step? </p>
<p>I know string theorists have shown extremal and near-extremal BPS black holes have stringey entropies... | g13058 | [
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<p>Why are ice and oil slippery? In general, why do certain substances make a surface difficult to walk on? </p> | g13059 | [
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<p>what fundalmentel force does a black hole based on?</p>
<p>It seems people is very unfamilar with black holes.</p>
<p>I will take a guess, is it electromantic force? please explain.</p> | g13060 | [
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<p>With all the sudden discussion related to Nuclear power, safety, fuel, waste, etc, there's one question whose answer has so far eluded me.</p>
<p>How big (height and diameter) is the actual pressure vessel of a conventional BWR or PWR? I've seen, now, about a thousand images depicting the structures of Fukushima, ... | g13061 | [
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<p>I know that molecules in ideal gas can move freely, and molecules in crystal are bonded to some specific location. But can I describe this in a more quantitative way? Do gas molecules have more degrees of freedom?</p> | g13062 | [
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<p>Imagine a pipe which is bent to form a circular arc and a liquid is force through this pipe. How will you find the net force exerted by the fluid on pipe? Is the only force acting on fluid centripetal force or is there a tangential force too?</p>
<p>No drag forces or viscous forces</p> | g13063 | [
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<p>I have recently carried out an experiment to verify Faradays law for a falling magnet. My starting point was to keep both the area of the coil and the number of turns constant whilst changing the velocity (the different velocities were obtained by dropping from different heights).What would be good is if a graph of ... | g13064 | [
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<p>I am reading a book on Gas dynamics and there is a small section
on thermodynamics before the conservation laws of mass momentum
and energy are introduced. </p>
<p>The book says</p>
<p>$$ p = R \rho T$$
where $R$ is a constant. When that is the case we can write </p>
<p>$$TdS = de + p d (\frac{1}{\rho}) \\
dS ... | g13065 | [
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<p>I'm studying vibrations; so I'm using Beer-Johnston-Cornwell Dynamics book. I am worry about the equation for Underdamped Vibration, which in the book it is: $$x_{(t)}=x_0e^{-\lambda t}\sin(\omega_d+\phi)$$; where $$\omega_d=\sqrt{\omega_n^2+c^2/4m^2}$$.</p>
<p>I think that $x_0$ would be replaced by the result vec... | g13066 | [
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<p>I'm trying to figure out the missing step here, in a problem about X-ray crystallography. I am referring to the attached image:</p>
<p><img src="http://i.stack.imgur.com/EkwDw.png" alt=""></p>
<p>In the image, $A =$ electron density, $Z =$ distance traveled, $\lambda =$ X-ray wavelength, $p$ = electron position. I... | g13067 | [
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<p>I'm a layman, but i watched some intereting videos about big bang on youtube[michio kaku, hawking this kind of things, not some crackpots :)] </p>
<p>I described everything on my picture: </p>
<p><img src="http://i.stack.imgur.com/fqZAC.png" alt="enter image description here"></p>
<p>So is there any possibility t... | g13068 | [
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<p>I'm arriving at a contradiction.</p>
<p>To calculate the scattering amplitude, one usually follows the prescription given by the Feynman rules that you only consider <strong>fully connected</strong> diagrams with the required number of incoming and outgoing external legs (See Peskin & Schroeder pg 111 where the... | g13069 | [
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<p>In the course of circuits and electronics, I remember there is an experiment to show the polarization of the wave as lissajous figures. I am wondering for polarized laser, is there any way to visualize the polarization in the similar way? I try to use a light splitter to split the (circular) polarized light into two... | g13070 | [
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0.06580797582864761,
0.016137614846229553,
0.046954959630966187,
0.022417519241571426,
0.06432560831308365,
0.0... |
<p>I came across K. O. Friedrichs' very old book (1953) "Mathematical Apsects of the Quantum Theory of Fields", and hardly any of it makes sense to me.</p>
<p>One of the strange things that he refers to are "Myriotic" fields. What are these? Is there a modern account of what Friedrichs is talking about?</p> | g13071 | [
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<p>How does the Fermi energy of extrinsic semiconductors depend on temperature?</p> | g13072 | [
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<p>It's a well known fact that an observer that accelerates at a constant rate from $-c$ at past infinity to $+c$ at future infinity sees a horizon in flat Minkowski spacetime. This is easy to see from a spacetime diagram once you realize that the union of past light cones on such a trajectory has a boundary that divid... | g13073 | [
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<p>Someone told me that reading glasses (<em>a priori</em> with a magnifying glass effect only) improve one's eyesight of objects lying in the long range distance. I am really sceptic about it since everything is blurry if I look at objects through those glasses! Is it possible (for this particular person at least)?</p... | g13074 | [
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<p>Let $\lambda$ be a linear density of a rope which is moving into a scale at velocity v. The additional force on the scale due to the collision is given as
$\frac{d p}{d t} = v\frac{d m}{d t} = \lambda v^2$.</p>
<p>For an incompressible fluid, the stagnation pressure from stopping a column of water <em>in excess o... | g13075 | [
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<p>Does it just mean "AC electric conductivity"? If so, why have a special name for it, and why mention optical specifically?</p>
<p>The <a href="http://en.wikipedia.org/wiki/Optical_conductivity" rel="nofollow">wikipedia page</a> on it is very sparse. <a href="http://physics.unl.edu/tsymbal/teaching/SSP-927/Section%2... | g13076 | [
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<p>Did he invent surface and line integrals, or did they already exist when he formulated his equations. If they did, already exist, how did they come about in pure math?</p> | g13077 | [
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<p>I basically want to observe the electrostatic force between two charges. I want to know if is there a simulator which could both help me to observe and calculate the force between two charges.</p>
<p>I found <a href="http://dept.sfcollege.edu/natsci/physics/simulations/electric_force_sim.htm" rel="nofollow">this si... | g13078 | [
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<p>The question is from ISSP by Kittel and as follows:</p>
<p>(a)Find a solution of the London equation that has cylindrical symmetry and applies outside a line core. In cylindrical polar coordinates, we want a solution of
$$ B-\lambda \nabla^2 B = 0 $$
that is singular at the origin and for which the total flux is th... | g13079 | [
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<p>If two gravitational waves came in contact with each other what would happen? In another question entirely, what happens when a higher gravitational field interacts with a weaker one.</p> | g13080 | [
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<p>I am reading the statistical mechanics by Pathria in Chap 12. I have a question about the Landau free energy. What is the physical reasoning for that the free energy could be a functional of the order parameter? Normally, the free energy is used when we choose the canonical ensemble and we we know that the free ener... | g13081 | [
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<p>Usually we say that equality of masses of particle and antiparticle follows from CPT-theorem. But do we need it for showing this equality?</p>
<p>The first method to show that is following.</p>
<ol>
<li><p>The equation of free fields of an arbitrary spin $s$: all of them have Klein-Gordon or Dirac form (with some ... | g13082 | [
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<p>I have some data like: </p>
<p>Wind flow from north direction = “X” Numbers of days. </p>
<p>Wind flow from east direction = “Y” Numbers of days. </p>
<p>Then is there any formula to know numbers of days wind flows from North-East direction?</p> | g13083 | [
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<p>If we describe a photons with a wave packet, moving towards a potential barrier and E smaller than V, there is a finite chance that it will tunnel to the other side. In this process it is likely that it will arrive before a photon that does not tunnel, not because it exceeds the the speed of light, but because the f... | g13084 | [
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<p>Preferably one that is researched in a paper, not necessarily in production.</p>
<p>I have found various claims of OPVs with an efficiency of 10%, 8% and 7.3%, the only one I can substantiate is referenced in a paper in Advanced Materials (Volume 22, Issue 34 pp 3839–3856) to Solarmer but the web reference there le... | g13085 | [
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<p>My first question is fairly basic, but I would like to clarify my understanding. The second question is to turn this into something worth answering.</p>
<p>Consider a relativistic electron, described by a spinor wave function $\psi(\vec x ,\sigma)$ and the Dirac equation. The conventional wisdom is that rotating ev... | g13086 | [
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<p>What is a proper definition of locality in condensed matter lattice model? I emphasize "condensed matter" because there is no Lorentz symmetry or "speed of light". I think it is quite important because this constraint will rules out most nonlocal lattice Hamiltonians. First, let's say local Hilbert spaces are put bo... | g13087 | [
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<p>If I keep a compass with bar magnets all around it, all of equal strength and a compass in a center then what will happen? Will the compass start rotating?</p> | g13088 | [
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<p>This post is aimed to stimulate some discussions.</p>
<p>We are familiar with many physical descriptions and theories of the (many-body quantum) system, with both <strong>quasi-particle description</strong> and <strong>Lagrangian description</strong>. For example: </p>
<blockquote>
<p>the Landau Fermi-liquids th... | g13089 | [
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<p>Hi I want to start learning multi variable calculus specifically for learning electrodynamics. What are some good text books?</p> | g185 | [
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<p>I've tried an alternative solution for finding the partition function of this model. </p>
<p>So is what I've done correct? If it isn't then please prove and explain why not. (I'm pretty sure I made a mistake along the way):$$ $$
Starting with the Energy:
$$
E = -J\sum_{i=1}^{N}S_{i}S_{i+1}-J'\sum_{i=1}^{N}S_{i}S_{i... | g13090 | [
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<p>We all know the Winter Solstice comes on December the 20th or 21st, which is (by definition) the shortest day of the year.</p>
<p>The Winter Solstice day is <strong><em>not</em></strong> the day of the year the Sun rises later (that would be one or two weeks later), and also is <strong><em>not</em></strong> the day... | g13091 | [
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<p>I drink from a glass of water with a vertical straw. What's the longest straw I can use and still drink water if the ambient pressure is 1 atm?</p>
<p>Details and assumptions</p>
<ul>
<li>1 atm is 101,325 Pa.</li>
<li>The acceleration of gravity is -9.8m/s^2 .</li>
<li>The density of water is 1g/cm^3.</li>
</ul>
... | g13092 | [
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<p>I got a rather small Netwon's cradle and when I start it, the effect is not very good since all the balls start to swing where the effect we want is obvious. The balls are small and I wonder if larger balls would make the swing more ideal, like only the outer balls appear to move and the 3 inner balls should be stil... | g13093 | [
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<p>I know that a clock placed on an aeroplane will have slowed with respect to a clock placed on earth because the more our velocities are, compared to the speed of light, the more the time slows down. But, the earth is moving faster than the aeroplane when viewed from outer space. Then, the clock placed on Earth shoul... | g13094 | [
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<p>I'm just starting to study quantum mechanics. Please explain the error in this thinking:</p>
<p>You set up decay of two $\pi$ mesons and get $2\mathrm{e}^-$ on Mars and $2\mathrm{e}^+$ on Earth. </p>
<p>On Earth you may or may not measure the spin of those positrons, with 50% probability that they are the same spi... | g13095 | [
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<p>Example. Two bodies with masses m1 and m2 distance between them one year of light. What happens to the force of attraction between the two bodies when one body suddenly disappears? Is the force disappears at the same time or the force will act on second body for one year?</p> | g4 | [
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<p>I'm studying circular motion and centripetal force in college currently and there is a very simple question but confuses me (our teacher doesn't know how to explain either :/), so I hope we can sort it out here ><
So I draw two pictures to show what I was thinking on it.</p>
<p><img src="http://i.stack.imgur.com... | g13096 | [
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<p>It is known that the Coulomb potential can be obtained by Fourier transform of the propagator from E&M. Is this because one of Maxwell's equations have the form $\nabla \cdot \mathbf{E}=\rho$? </p> | g13097 | [
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<p>I'm reading the specs of an IC (Cypress 5LP SoC) and it says it's available in 30 k g shock resistance configuration. The fastest acceleration I heard of so far was hitting a golf ball hard, which would be around 1000 g. Does anyone have an example of a mechanical impact of 30 000 g (300 000 m$\cdot$s$^2$), applicab... | g13098 | [
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<p>A rod of length L & mass M is rotating in a circle about one end then calculate tension in the rod at a distance 'x' from the support ?</p>
<p>For its solution why should we take mass of L-x portion of rod instead of taking mass upto x distance from support as we have the formula </p>
<p>T = m w2 x
I m in conf... | g13099 | [
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<p>So this seemed pretty straight forward at first, but then I wasnt too sure about gravity forces...</p>
<p>So.</p>
<ul>
<li>centerfuge</li>
<li>2 samples</li>
<li>1 sample is 1gram heavier than the other</li>
<li>centerfuge at top speed is exerting 20000 gravitys of force on the samples</li>
</ul>
<p>What kind of ... | g13100 | [
0.04289315640926361,
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<p>I have read this article</p>
<p><a href="http://scitation.aip.org/content/aas/journal/aer/9/1/10.3847/AER2010009">SIBBERNSEN, Kendra. Catching Cosmic Rays with a DSLR. <em>Astronomy Education Review</em>, 2010, 9: 010111.</a></p>
<p>and it talks about estimating the muon cosmic ray flux by means of a DSLR camera.<... | g13101 | [
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<p>Knowing that:</p>
<ul>
<li><p>The Zone of Avoidance (Looking towards the center of the Milky Way) blocks roughly 20%</p></li>
<li><p>Each Milky Way star has an angular size, depending on proximity, that obscures a certain percentage of our optical view.</p></li>
<li><p>Each Galaxy has an angular size, depending on ... | g13102 | [
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<p>The operator $\hat{F}$ is defined by $F\psi(x)=\psi(x+a)+\psi(x-a)$</p>
<p>Does this mean $\hat{F}=(x+a)+(x-a)$ and that $\hat{F}$ is operating on $\psi(x)$?</p> | g13103 | [
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://physics.stackexchange.com/questions/886/swimming-in-spacetime-apparent-conserved-quantity-violation">Swimming in Spacetime - apparent conserved quantity violation</a> </p>
</blockquote>
<p>It is well known that a deformable object can perf... | g412 | [
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<p>I am working on upgrading an electromagnet design program. There are currently two types of wire used for the coil, circular and strip (read as: rectangular).</p>
<p>The current algorithms in this program are empirically derived with lots of undocumented constants and so one of the requirements is to move it more i... | g13104 | [
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<p>Suppose I have a wave function $\Psi$ (which is not an eigenfunction) and a time independent Hamiltonian $\hat{\mathcal{H}}$. Now, If I take the classical limit by taking $\hbar \to 0$ what will happen to the expectation value $\langle\Psi |\hat{\mathcal{H}}|\Psi\rangle$? Will it remain the same (as $\hbar = 1.0$) ... | g13105 | [
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<p>Can someone explain to me the origin of the exchange interaction between two electrically charged spin 1/2 fermions? Quantitative or qualitative accepted. </p> | g13106 | [
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<p>When accounting for the excluded volume for in the Van der Waals equation, it is assumed that the molecules are hard spheres and are of diameter. If we consider a cube of volume V, then we can say that the side of this cube is of length $V^{1/3}$. Consider the diameter of the molecules to be $\sigma$. Suppose that t... | g13107 | [
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<p>There are power law of phase transition in physics and Zipf law in linguistics which are similiar to each other ,and some expert think they are in fact just the same.But the diagrams of them base on the data of physics and data of language are not that same.
What is difference and linkage between power law of phase ... | g13108 | [
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<p>NASA has recently <a href="http://science.nasa.gov/science-news/science-at-nasa/2014/02jun_saucer/" rel="nofollow">tested a saucer-shaped spaceship</a>. What's the advantage of this new design over traditional aerodynamic designs?</p>
<p>The test launch was performed from within atmosphere which would offer higher ... | g13109 | [
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<p>Take the Lagrangian with one fermion:
$$ \mathcal{L} = -\frac{1}{4}F^{\mu\nu}_aF^a_{\mu\nu} + \bar{\psi}(i\gamma^\mu D_\mu - m)\psi$$
where the gauge covariant derivative $D_\mu = \partial_\mu+i\frac{g}{2}t^aW^a_\mu$. The Lagrangian is invariant under a local $SU(2)$ transformation:
$$ \psi(x) \rightarrow \exp \left... | g13110 | [
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<p>If a current in a wire is flowing perpendicular to a magnetic field, the Hall effect will be observed, which is caused by the forces from magnetic fields 'pushing' the electrons to one side or the wire. So, does it increases the resistance of the wire, as there is now less area for current to flow through due to one... | g13111 | [
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<p>I am an undergraduate student (Bachelors of engineering) about to complete my 1st year in the
field of Information science and engineering or information
technology. I am interested in pure physics especially high energy
physics and some parts of quantum Physics. My question is that, is there any
possibilities i... | g13112 | [
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<p>While studying radioactivity I found that even the most radioactive substances i.e substances with the shortest half lives do not completely degenerate. </p>
<p>Suppose there is a 1 mole sample of an element <strong>X</strong> whose half life is <strong>1 day</strong>.
But as the <em>degeneration equation</em> is <... | g13113 | [
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<p>I had never seen rotation free transformations called "boosts" (I think I have it right) before reading some questions here. I'm too old perhaps. I have not found the etymology after some searching, though it sounds like something V.I. Arnold would think up, or jargon from inertial navigation. Anyone know where/how ... | g13114 | [
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0.005734208971261978,
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<p>I've noticed that an airplane appears to have more lift when it's almost touching the ground then it has 100 feet or more in the air. What causes this to occur?</p> | g13115 | [
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0.06319... |
<p>Let $\dot{z} = A(t)z + b(t)$ with $ z(t) \in \mathbb{R}^n$ and $A(t)$ be a linear map from $\mathbb{R}^n \rightarrow \mathbb{R}^n$. A propagator is also a linear map $P(t,s):$ $\mathbb{R}^n \rightarrow \mathbb{R}^n:$ $z(s) \rightarrow z(t)$ and has the following properties:</p>
<ol>
<li>$P(t,r)P(r,s) = P(t,s)$</li>... | g13116 | [
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0.0017937063239514828,
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0.07906901091337204,
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... |
<p>I was told that the Galilean relative velocity rule does not apply to the speed of light. No matter how fast two objects are moving, the speed of light will remain same for both of them. </p>
<p>How and why is this possible? </p>
<p>Also, why can't anything travel faster than light?</p> | g348 | [
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<p>I have an UPS with two 6V batteries connected in series. Is it possible to use the same system (UPS) to charge another two pieces of 6 volts battery if all the batteries are connected in parallel to maintain a 12 volts circuit?</p>
<p>Will this affect the charging system of the ups if the connection is made?</p> | g13117 | [
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<p>This may or may not be an incredibly stupid thought experiment, but a short time ago I read that most of the "mass" in the proton was actually energy from the quarks and gluons, as opposed to the actual mass which was coupled to the Higgs field. This made me start thinking about objects on macroscopic scales and the... | g13118 | [
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<p>After closing my refrigerator's door I noticed that it's much harder to reopen it immediately, as if there's an underpressure. Only after a minute or so it opens normally. How can this be explained?</p> | g13119 | [
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0.0... |
<p>The hyperfine structure of the energy levels of the hydrogen atom refers to the shifts in the evergy levels due to the magnetic moments of the nucleus and of the electron. This is an effect of non-relativistic QM, if I understand correctly.</p>
<p>On the other hand, the Lamb shift in the energy levels is due to com... | g13120 | [
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<p>Does anyone know the amount of thermal energy that the Earth's mantle and core possess? I don't mean the maximum limit of electrical power we could generate with geothermal plants, but rather: if you took the Earth and magically cooled it down so that its temperature became homogeneously 0K, what would the change in... | g13121 | [
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0.019636861979961395,
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0.002056046621873975,
0.02939927577972412,
-0.0202... |
<p>One model for confinement in quantum chromodynamics is the <a href="http://scholar.google.com/scholar?hl=en&q=savvidy" rel="nofollow">Savvidy vacuum</a>. This is a spontaneous symmetry breaking of color gauge symmetry by the gauge fields. The vacuum is divided into Savvidy domains. Is this process hidden by conf... | g13122 | [
0.016695233061909676,
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0.012009450234472752,
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0.004470400977879763,
0.015130813233554363,
0.01... |
<p>How would you prove that the simultaneous measurements of position and energy are not subject to interference?
I was thinking in calculate the commutation relation between $x$ and $H$ (Because $\Delta E=\Delta H$), but I realized that $[H,x]\neq0$, so I tried to use a more general expression for the Uncertainty Prin... | g13123 | [
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0.015308293513953686,
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<p>If you look at most published articles, or those on the preprint server, you find the vast majority of articles have more than one authors. Are collaborations needed to be productive in physics? In other fields like math, single author articles are the norm.</p> | g13124 | [
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-0... |
<p>I was wondering what subjects a freshman in mathematics ought to choose in the future if s/he wanted to help working on energy and environment-related issues we are currently facing, and will very likely be even more profound in the future. </p>
<p>I am currently day-dreaming about using the skills I will acquire a... | g13125 | [
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0.07603015750646591,
0.04938606545329094,
0.034358806908130646,
-0.00... |
<p>It seems that virtual photons also exist in vacuum. So the precise question is:</p>
<p>What is the additional virtual photon density due to the electric field of a unit charge?</p>
<p>Or: How many virtual photons per volume are found around a unit charge?</p>
<p>The answer will depend on distance, but what are th... | g13126 | [
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0.024... |
<p>According to the <a href="http://en.wikipedia.org/wiki/Induction_cooking#Limitations" rel="nofollow">Wikipedia</a>, one of the limitations of the induction cooker is that the bottom surface of the pot should be flat.</p>
<p>Accordingly, I commented on a question on <a href="http://cooking.stackexchange.com/q/14669/... | g13127 | [
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0.... |
<p>Or said another way - how much counterweight does the base of a sign need to keep it from tipping over given a specific max wind?</p>
<ul>
<li>Assume the sign does not let wind through</li>
<li>Assume the base of the sign cannot slide on the ground</li>
<li>Assume the sign does not flex in the wind</li>
<li>Assume ... | g884 | [
0.02443348988890648,
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0.008757895790040493,
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0.03... |
<p>I was told long time ago that DC relay had a coil. There was a switch (2 wires, one is stable, the other one is flexible) inside the coil. The switch was parallel to the axial direction of the coil. </p>
<p>Today, I am thinking how AC relay works. I go back to think about DC relay. If what I was told is right, the ... | g13128 | [
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<p>I noticed when I was boiling pasta the other day that the pasta uniformly spread out and formed a donut like torus. Why does this happen? Does it have to do with the shape of the pot? I tried to take a picture when it was boiling, but steam got all over my lens. So, this is a more 2d version of what the pasta looked... | g13129 | [
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<p>So I was bored and had some clear Scotch tape nearby. Decided to mess around, and now I have questions. </p>
<ul>
<li><p>What is the physics behind the force of tape adhesive? </p></li>
<li><p>Why does the tape hold so much better if it is pulled parallel to the surface
plane it is on? (Excuse my poor drawing skil... | g13130 | [
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<p>I'm currently preparing for an examination of course in introductory (experimental) particle physics. One topic that we covered and that I'm currently revising is the universality in weak interactions. </p>
<p>However I don't really understand the point my professor wants to make here. </p>
<p>Let me show you his ... | g13131 | [
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<p>To explain, with a source of 'normal' photons, as the source becomes more and more distant the luminosity fades until finally the stream of photons is no longer continuous, giving the receiver individual peaks of energy with none in between. As recession continues the gaps between energy peaks (photon impacts) becom... | g13132 | [
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... |
<p>The orbit of the earth seems to be very predictable. But as it is a many-body problem having sun, earth, moon, jupiter and so on, is it really that stable or will it start making strange movements sooner or later?</p>
<p>Are there asteroids or moons in our solar system with obviously chaotic orbits?</p> | g13133 | [
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0.006984... |
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