question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>The LHCb has recently <a href="http://arxiv.org/abs/1211.2674">published</a> the observation of $B_s \rightarrow \mu^+ \mu^-$ with a branching ratio that agrees with the Standard Model (SM). There are many blog posts about it (See: <a href="http://profmattstrassler.com/2012/11/12/first-news-from-kyoto-conference/">O... | g18959 | [
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<p>I've read that it's just as correct to think of A moving toward B (ie. A doesn't move, but B does) as it is to think about B as moving toward A (again, A doesn't move, but B does) or as the two moving toward each other. </p>
<p>If I imagine a universe in which only two objects exists - then that seems like it would... | g18960 | [
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<p>The Thomas-Fermi equation with dimensionless variables is identified as;
$$
\frac{d^2\phi}{dx^2} = \frac{\phi^{3/2}}{x^{1/2}}
$$
with the boundary conditions as
$$
\phi(0) = 1 \\
\phi(\infty) = 0.
$$
There are many series approximation solutions available to this equation. I am interested in finding the integral rep... | g18961 | [
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<p>Suppose two parties $A$ and $B$, some distance apart and at rest relative to each other both had control of one massive local object each.</p>
<p>If party $A$ lifted their local object upward relative to $B$, than the total force of gravity on $B$'s mass would angle upwards slightly.</p>
<p>If B then measured this... | g18962 | [
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<ol>
<li><p>What is <a href="http://en.wikipedia.org/wiki/Topological_degeneracy">topological degeneracy</a> in strongly correlated systems such as <a href="http://en.wikipedia.org/wiki/Fractional_quantum_Hall_effect">FQH</a>? </p></li>
<li><p>What is the difference between topological degeneracy and ordinary degenerac... | g18963 | [
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<p>Why is the lightness of particles unexpected?</p>
<p><a href="http://motls.blogspot.com/2012/09/experimenters-susy-frustrations-and.html" rel="nofollow">http://motls.blogspot.com/2012/09/experimenters-susy-frustrations-and.html</a></p> | g18964 | [
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<p>Can we use some type of magnifying glass to magnifying gravity react on a body by theoretical physics?</p>
<p>If so, could someone use it to destroy the earth</p> | g18965 | [
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<p>I did something very stupid tonight. I poured hot water into an polyethylene water bottle and it immediately contracted causing it to overflow and burn my hand and leg. I immediately wasted my hand and feet with cold water.</p>
<p>Now I am left with a useless bottle that resembles what you see at a modern art fair.... | g18966 | [
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<p>What is the current status of the swampland? Have people expanded the list of swampland criteria?</p>
<p>If let's say I wish to figure out if the Standard Model belongs to the swampland, are there any concrete steps I can use to go about it, at least in principle? If let's say technical difficulties aren't an objec... | g18967 | [
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<p>As the galaxy is moving and the solar system orbiting the galaxy and the Earth orbiting the sun. So how fast is each object moving and what is the fastest we move at?</p>
<p>Do we even know how fast the galaxy is moving that is not relative to another galaxy (although I guess velocity has to be measured relative to... | g18968 | [
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<p>We have learned that Torque is equal to a force that is perpendicular to a radius (displacement); however, I just cannot grasp one of the study questions we received:</p>
<blockquote>
<p>A hammer thrower accelerates the
hammer (mass = 7.30 kg) from rest
within four full turns (revolutions)
and releases it ... | g18969 | [
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<p>Kostyas question for angular momentum and half wave plates
<a href="http://physics.stackexchange.com/questions/4479/half-wave-plate-and-angular-momentum">Half wave plate and angular momentum</a>
made me think a little bit. It took me some seconds to "swallow" the answer. :=) </p>
<p>Then I started to think further... | g18970 | [
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<p>Clearly finite groups are of immense value in physics and these are also substructures of fields. However I never came across any computations involving finite fields at university and so I never learned about them explicitly.</p>
<blockquote>
<p>Are there some physical motivations to study <a href="http://en.wik... | g18971 | [
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<p>My research, which is mainly related to communication, involves the use of optical sources (mainly lasers). However, my background in photonics and optics is not yet solid, so my question might be a very simple one.</p>
<p>In one part of my experiment, I have two laser beams crossing a piece of glass as shown in th... | g18972 | [
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<p>Electromagnetic energy is introduced at pre-university level, starting with static electric energy followed by static magnetic energy. But the introduction of electromagnetic momentum usually has to wait until university, usually after Poynting's theorem has been derived from Maxwell's equations.</p>
<p>Is there a ... | g18973 | [
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<ol>
<li>First, what determines the strength of an RF signal?</li>
<li>Why is it said that a cellphones radiates more energy when the reception from signal tower is lower in strength.</li>
<li>Why is it said that RF gets transmitted along wires such as in wired headsets making them act as antennae?</li>
<li>Is it then... | g18974 | [
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<h1><strong>The setup</strong></h1>
<p>A transparent isotropic dielectric medium moving in the negative $x'$ direction at speed $v$ in frame $S'$ is stationary in frame $S$, where it has refractive index $n$. In other words, frame $S'$ is moving at speed $v$ in the positive $x$ direction relative to frame $S$. We take... | g18975 | [
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<p>We had this experiment in which we measured the intense of <strong>linear polarized</strong> wave - with and without a polarizer.</p>
<p>I noticed that <strong>without the polarizer</strong> the intense was slightly lower than <strong>with the polarizer</strong>. How is that possible?</p>
<p><img src="http://i.sta... | g18976 | [
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<p>I'm studying the holographic entanglement entropy (HEE) in <a href="http://arxiv.org/abs/hep-th/0605073v3" rel="nofollow">this paper</a> (Ryu-Takayanagi, 2006). In section 6.3 they compute the HEE for a segment in a 2D CFT. To do so, they obtain the corresponding geodesic in the bulk (in the Poincaré patch) and comp... | g18977 | [
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<p>I am interested in studying quantization, but it seems I am lacking the basics of classical mechanics. Any help would be appreciated.</p>
<p>I would first like to ask what is necessary to have a sympletic/Poisson structure in a classical mechanical system (e.g. an isolated particle moving on some Riemannian manifol... | g18978 | [
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<p>This is a summary from Physics World of the paper: L J Wang et al. 2000 Nature 406 277--
"Wang and colleagues begin by using a third continuous-wave laser to confirm that there are two peaks in the gain spectrum and that the refractive index does indeed change rapidly with wavelength in between. Next they send a 3.7... | g18979 | [
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<p>The size of our observable universe must have grown over time in the early universe. Conversely with the accelerated expansion, I have heard that eventually our observable universe will shrink down to our local group of gravitationally bound galaxies. So then the observable universe must go through a maximum at so... | g18980 | [
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<p>There is a somewhat recent <a href="http://arxiv.org/abs/1005.5173" rel="nofollow">paper</a> by Colbeck and Renner that, given the assumptions — 1) QM accurately predicts the correct statistical results in experiment (which so far has always been found to be true) and 2) the measurement can freely be chosen — that n... | g18981 | [
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<p>In the first episode of Cosmos. It was said that after the big bang, gravity worked to pull clumps of gas together and heating them.</p>
<p>My question is what was exerting the gravitational pull to make these clumps of gas come together?</p> | g18982 | [
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<p>Are the intermediate vector bosons real (like the electrons) or just mathetical constructs?i have got a theory to unify the 4 forces, but it does not tell anything about exchange particles in case of the weak force.I could proceed only if they are imaginary.</p> | g582 | [
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<p>From Hamiltonian formalism there is well known equation,
$$
\frac{d F}{dt} = \frac{\partial F}{\partial t} + \{F, H\}_{PB},
$$
where $ \{H, F\}_{PB}$ is the <a href="http://en.wikipedia.org/wiki/Poisson_bracket" rel="nofollow">Poisson bracket</a>.</p>
<p>After using Hamiltonian formalism in quantum mechanics it tra... | g18983 | [
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<p>What is the quantum mechanical explanation of the <a href="http://en.wikipedia.org/wiki/Octet_rule">octet rule</a>? In other words, what makes the octet rule be true from a quantum mechanical view? How we explain what makes some atoms don't follow the octet rule using QM?</p> | g18984 | [
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<p>I have a fluid mechanics question, that I think is caused by a lack of understanding of some key concepts. Suppose we have a horizontal capillary with a radius of 10um. The fabrication process has led to water having a contact angle of 110 degrees with 0.072N/m for the air-water surface energy. Based on the equation... | g18985 | [
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<p>There are claims often made that, eg, "An ounce of weight at the rims is like adding 7 ounces of frame weight." This is "common knowledge", but a few of us are skeptical, and our crude attempts at working out the math seem to support that skepticism.</p>
<p>So, let's assume a standard 700C bicycle tire, which has ... | g18986 | [
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<p>I'm not expecting a definitive answer. But I would like
someone to explain which are the main forces that interact
in this situation:</p>
<p>An ideal cylindrical column that is at first vertical
is pushed just enough so it loses its balance and
falls on its side.
At every moment there's a point in the circumference... | g18987 | [
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<p>Changing Electric Field causes Magnetic filed and changing Magnetic Field causes Electric Field. Is there anything similar in relation to Gravitational Field? What sort of field is created by varying Gravitational Field?</p> | g18988 | [
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0.025767... |
<p>In the Green, Schwarz and Witten Superstring Theory textbook, the paragraph below equation 3.3.15 says, </p>
<blockquote>
<p>For genus greater than one, it can be shown that the surface admits a metric of everywhere negative scalar curvature.</p>
</blockquote>
<p>This statement is essential in the proof that $C_... | g18989 | [
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<p>My understanding is that a black hole radiates ~like an ideal black body, and that both photons and massive particles are emitted by Hawking radiation. So for a low temperature black hole, photons are emitted according to Planck's law, but the peak of this spectrum shifts to higher frequencies as temperature increas... | g18990 | [
0.022777536883950233,
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0.001... |
<p>I have set myself the task of studying the kinetic energy $T$ in a quantum mechanical system. For the latter, I use the simple case of the Hydrogen atom in the $n=1$ state. Then the wave function is (essentially) given by $\Psi = \exp(-r)$. The kinetic energy operator is a (negative) constant times the Laplace opera... | g18991 | [
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<p>What is the optical illusion called where our sun seems to disappear for 3 days and then rise again into view on the third day? And where can it be viewed from?</p> | g18992 | [
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<p>I can't wrap my head around this idea because I don't know much about air flows.</p>
<p>Say we have this imaginary apartment with two windows, one of which is two times smaller than the other:</p>
<p><img src="http://i.stack.imgur.com/2jkqC.png" alt="enter image description here"></p>
<p>Will the first one let mo... | g18993 | [
0.029091788455843925,
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<p>I understand that gauge bosons transform as the adjoint of their respective symmetry groups, but what determines the spin of the field? Can you have some gauge group where the adjoint is spin zero?</p> | g18994 | [
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<p>If the charge is large, considering charge density is usually meaningful despite the discrete nature of electrical charge. The following sentence is part of a problem in a textbook on electromagnetics:</p>
<blockquote>
<p>Imagine a sphere of radius <em>a</em> filled with negative charge of uniform density, the to... | g18995 | [
0.017415251582860947,
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<p>I have a little problem that is kind of confusing me at the moment.
The following task:</p>
<blockquote>
<p>Light of the wavelength $\lambda = 500nm$ hits a double slit whose distance is $a = 30\mu m$. Each is $a = 1\mu m$ wide. On the detector the distance from the first minima to the center is $y' = 1.5 cm$. Ho... | g18996 | [
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<p>Can we actually prove with 100% accuracy that there is more than 3 dimensions plus time?</p>
<p>In the news there are always articles like "there are probably 7, 11 or more dimensions", "time is actually not a 4th dimension" etc.</p>
<p>My question is: </p>
<p><strong>Could we be 100% sure that there are more tha... | g583 | [
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<p>I have the following problem - which is basically that $\omega = f(g,h,l)$ now the book claims that the two $\pi$ terms as follows $\pi_1 = \omega \sqrt{\frac{l}{g}}$ and $\pi_2 = \frac{h}{l}$. Now we know we can get different dimensional $\pi$ terms because of the nature of the theorem. The ones I get however I obt... | g18997 | [
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0.04987639933824539,
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<p>I am trying to simulate a soft body object by having a collection of points connected by springs. I also want to have the object bounce on a plane. I have been able to implement Euler's method to make this simulation work, but it is not satisfactory because when I increase the spring constants it becomes unstable. I... | g18998 | [
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0.... |
<p>Today, I was reading an article <a href="http://home.howstuffworks.com/thermos1.htm" rel="nofollow">How Thermoses Work</a>
It goes on to explain all three processes of heat transfer:</p>
<ul>
<li>Conduction</li>
<li>Radiation</li>
<li>Convection</li>
</ul>
<p>In Convection, It states,</p>
<blockquote>
<p>If it ... | g18999 | [
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0.06851450353860855,
0.004652786068618298,
0.047... |
<p>Yes, they are different phases of the same thing, but suppose a scenario where the ice must remain solid and water must stay in it's the liquid form. </p>
<p>This is more of a philosophical question than a practical one, but suppose 2 scientists. one from the liquid planet and another from solid planet, where the r... | g19000 | [
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<p>Why is energy/ mass taken away from a black hole? Doesn't the energy coming from the virtual particle come from the vacuum energy? ...if this is so, why does the black hole have to pay the energy debt? </p>
<p>If the black hole creates the particles by its energy, what energy was used from the black hole to crea... | g19001 | [
0.07395779341459274,
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0.020721813663840294,
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-0.00... |
<p>In the introduction of his book <a href="http://www.alainconnes.org/en/downloads.php" rel="nofollow"><em>Noncommutative Geometry,</em></a> p. 42, Connes explains that when a classical dynamical system has enough constants of motions, the motion of the system is <a href="http://en.wikipedia.org/wiki/Almost_periodic_... | g19002 | [
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-0.... |
<p>So I'm trying to gain a better understanding of electrooptic tensors:
<br>
An example of a quartz electrooptic tensor is given.
I know in order to best implement this crystal, in order to get the highest birefringence or highest opto,piezoelectric output, I want to use the value that is largest in this tensor.
<br>
... | g19003 | [
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0.04657835513353348,
0.0014291536062955856,
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0.06753560155630112,
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0.029032154008746147,
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0.01879049651324749,
0.04752829298377037,
-0.048... |
<p>Imagine a set up with a column of sand with porosity $\phi$ and permeability $k$ contained in a cuboid container. When one pours water evenly (let's say $V_w/A$ cubic meters per square meter) on the top surface of the sand at the same time, how does the distribution of water (water content at a particular height) of... | g19004 | [
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0.024873578920960426,
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0.005837294738739729,
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0.00161... |
<p>I'm trying to relate a near shore tidal signal (<strong>point A</strong>) to 3 points along a long model boundary (<strong>points B C D</strong>). I want to possibly have a relationship between <strong>B C D</strong> with which we can convert <strong>A</strong> predictions into <strong>B C</strong> and <strong>D</st... | g19005 | [
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0.004823342431336641,
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0.033868804574012756,
0.06780151277780533,
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<p>I live in area which have many properties similar to desert. Many times when I drive by I see a whirlwind/tornado/dust devil of sand or other garbage parts.
I would like to ask how this was normally being created and what kind of force keeps it stable?
How high can such a vortex can get to? (Just an estimation) Is i... | g19006 | [
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<p>I have a very basic question with respect to supersymmetry. Actually, I no clear idea at all what the effect of the superpartners (called gauginos??) of the exchange particles of interactions (photons, gravitons, gluon, W+-s and Z0s) on the corresponding interaction is.
Example: Gravitation: According to supersymmet... | g19007 | [
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0.0170... |
<p>In the fifth of his <a href="https://www.youtube.com/watch?feature=player_detailpage&v=-Km7-6-J81k#t=2182s" rel="nofollow">Messenger Lectures</a> Feynman mentions the fact that Carbon-12 has an energy level at 7.82 MeV. He then states that this is what enables the fusion of three Helium-4 ions into Carbon and ul... | g19008 | [
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<p>In explosive safety and stability testing, a drop test is commonly used to determine the sensitivity to impact. In the test, an impactor of known mass is dropped. The initial height varies throughout the experiment. The detonation status is recorded in the material and various techniques are used to convert the heig... | g19009 | [
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<p>What is the appropriate mathematical background someone must attain in order to enroll in a quantum physics course for beginners?</p> | g223 | [
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<p>Layman here so I'm hoping for an answer for my query that doesn't involve math.</p>
<p>I'm reading about inflation and how it solves the flatness and horizon problems. I get that the horizon problem deals with the uniformity of matter/energy in the universe. </p>
<p>Flatness deals with the curvature. But isn't the... | g19010 | [
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0.016030939295887947,
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0.03613966330885887,
0.00... |
<p>$F=Gm_1m_2/d^2$</p>
<p>$F=ma$</p>
<p>$a_g=Gm_{other}/d^2$</p>
<p>In Newtonian mechanics, the acceleration of object A toward object B is not dependent on the mass of object A but on the mass of object B and the distance between objects A and B. Because the mass of object A does not affect its acceleration due to... | g19011 | [
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<p>I read about magnetic induction communication on <a href="http://www.mining-technology.com/features/featurelockheed-martin-post-accident-wireless-mining-communication/">Lockheed Martin's wireless mining communication system</a></p>
<p>In this interview Warren Gross said:</p>
<blockquote>
<p>We generate a signal ... | g19012 | [
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0.04860837757587433,
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-... |
<p>I don't really understand the general theory of relativity (GTR) really deeply, but according to my understanding, the GTR say that gravitation is caused by the curvature of spacetime by objects with mass. This makes some sense when you are talking about a moving object having it's course changed by the gravitation... | g19013 | [
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<p>A block of mass m slides down a hemisphere of mass M. What are the accelerations of each mass? Assume friction is negligible. </p>
<p><img src="http://i.stack.imgur.com/cLWnd.png" alt="enter image description here">
a_M = Acceleration of hemisphere</p>
<p>N_m = Normal force of M onto m</p>
<p>N_M = Normal force ... | g19014 | [
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<p>In elastic collision of ball to wall along x axis<br>
m*V<sub>ix</sub>=m*V<sub>fx</sub><br>
as velocity of wall is 0 before and after collision thus<br>
V<sub>ix</sub>=V<sub>fx</sub> ......eq(1)<br>
Kinetic Energy is conserved so<br>
m*V<sub>i</sub><sup>2</sup> = m*V<sub>f</sub><sup>2</sup><br>
(V<sub>ix</sub><su... | g19015 | [
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<p>I'll start with a scenario for some control in the concepts I'm asking about today.
Forgive me in advance, I never had the chance to explore physics in school, but I'd be happy to learn something new here.</p>
<p>Let's say I have 3 different fly wheels, all 3 of them have a handle in the middle to hand-crank them. ... | g19016 | [
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... |
<p>I did a recent question about relativistic kinematics here: <a href="http://physics.stackexchange.com/q/66718/10531">Generalizing a relativistic kinematics formula for spatial-acceleration dependence</a>.</p>
<p>I have a confusion. In the textbooks I've seen, they put the relationship between proper acceleration an... | g19017 | [
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0.02554759755730629,
0.00023689087538514286,
0.0... |
<p>I have a very simple question. Can we know about the topology of the underlying space-time manifolds from Quantum mechanics calculations? If the Space-time is not simply connected, how can one measure the effects of this from calculating transition amplitudes in the path integral formalism?</p> | g19018 | [
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... |
<p>I don't understand what is meant by there being a "solution" to an equation. For example, what does a solution to the wave or heat equation represent, and <em>what are we solving for</em>? </p>
<p>Of course, we can use such equations to perform computations, but what can the "solutions" tell us, and how can we use ... | g19019 | [
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<p>Is the particle in a box under harmonic driving electric field solvable analytically?</p>
<p>Here is the Schrodinger equation:</p>
<p>$$
i\frac{\partial \psi(x,t)}{\partial t}=\left[-\frac{1}{2} \frac{\partial^2}{\partial x^2}+V(x)+F(t)*x\right]\psi(x,t)
$$</p>
<p>where the potential $V(x)$ is</p>
<p>$$
V(x)=
\b... | g19020 | [
-0.015341799706220627,
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0.0869235172867775,
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0.02387096919119358,
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0.0029669199138879776,
0.009378818795084953,
0.013333423994481564,
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-0.... |
<p>When I cook things, such as scallop and salmon, I found that the food may be more tender if I wait till the water boils (at 100 C) and immediately turn the fire lower so that the water is not bubbling in the cook pot and maintain the fire at this level. But I noticed that at this point, there is more steam coming o... | g19021 | [
0.07273032516241074,
0.02041517198085785,
0.0023402150254696608,
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<p>The <a href="http://www.fair-center.eu/public/what-is-fair/accelerators.html" rel="nofollow">FAIR accelerator</a> is a planned facility for antiproton and ion research.</p>
<p>Ground water wells are being put in, the forest is being cleared... But when is it supposed to be completed? Does anyone know?</p> | g19022 | [
0.030908947810530663,
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0.043900828808546066,
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... |
<p>I want to calculate if it is possible to photograph a subject lit only by starlight. I found one website claiming that a starlit scene is lv = -15 (daylight is lv 15, or 2^31 times brighter), but he has no references. However I'd prefer to confirm this before I take a one hour exposure in the middle of nowhere, far ... | g19023 | [
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0.011458752676844597,
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0.... |
<p>I encountered the term "lateral fridge displacement" in my optics homework for a problem about inserting a thin plate of glass over one of Young's double splits. </p>
<p>So what does "lateral fringe displacement" mean in this context? I <a href="http://www.google.com/search?q=lateral+fringe+displacement" rel="nofol... | g19024 | [
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<p>I can't figure out how many different spin states I can create with a four-electron system. I think I can create a spin-zero state, three spin-one states, and five spin-two states. That gives me nine possible states altogether. </p>
<p>My problem is that I can specify a maximum of eight (complex) numbers to complet... | g19025 | [
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<p>When quantum entanglement is explained in "layman's terms", it seems (to me) that the first premise, that we have to accept on faith, is that a particle doesn't <em>have</em> a certain property (the particle is not IN one state or another) until that property is measured. </p>
<p>For example, I have read that a pa... | g19026 | [
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<p>If we have a dielectric inside an electric field, the dipoles in the dielectric will align in the following direction due to the torque on them by the external field.</p>
<p><img src="http://i.stack.imgur.com/Ya5zU.gif" alt="enter image description here"></p>
<p>The conclusion then is that the overall field is red... | g19027 | [
0.009569625370204449,
0.004292486235499382,
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... |
<p>Im estimating the $H_0$ (<a href="http://en.wikipedia.org/wiki/Hubble_constant" rel="nofollow">Hubble constant</a>) using the calculated distance to galaxy (M100) in the Virgo cluster, but given that the cluster is about 1-2 megaparcecs in diameter, what issues can I expect to face with using this method? </p>
<p>A... | g19028 | [
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0... |
<p>When the effect of the strain on solids is discussed, normally the explanation is the following: increasing stress, first point defects created, then dislocations, then plastic deformation starts, etc. I am trying to find papers (books) where first step is discussed in details.</p>
<p>Surprisingly, it is not that s... | g19029 | [
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<p>I am studying 2D quantum scattering models for my Bachelor's thesis. Somewhat like these:</p>
<p><img src="http://i.stack.imgur.com/9s7SK.png" alt="enter image description here"></p>
<p>,with Dirichlet ($\psi \mid_\Gamma = 0$) boundary conditions on the "walls" of the waveguide and the resonator. The waveguide is ... | g19030 | [
-0.030682260170578957,
0.016881784424185753,
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... |
<p>In class today (philosophy of the mind) we discussed the ideas of Richard Lewontin. He stated that in determining the phenotype of a gene we must take into account the environment but also quantum uncertainties. Many people did not understand what these uncertainties might be. I would like to email the class and exp... | g19031 | [
0.015928523615002632,
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0.01340213231742382,
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<p>The de broglie hypothesis suggests a particle can be associated with a wave of
momentum $p = \hbar k$</p>
<p>my question is the following: how does one arrive at this concept of the momentum of a wave?</p>
<p>I understand the classical definition of momentum, however I do not see an obvious extension to an object... | g19032 | [
0.07103518396615982,
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0.024020588025450706,
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-0.02335185743868351,
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0.0027346909046173096,
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0.011... |
<p>If I apply horizontal force on a body resting on the ground, my force will be opposed by the frictional force and the body will accelerate at the point where my force exceeds the force of friction = $\mu\, \mathrm{N}$ ($\mathrm{N}$ being the normal and $\mu$ being the coefficient of friction). In this case, the thre... | g19033 | [
0.042972542345523834,
0.04164629057049751,
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-0.022124... |
<p>Consider a standard Michelson Interferometer (I took the picture from <a href="http://en.wikipedia.org/wiki/Interferometer" rel="nofollow">http://en.wikipedia.org/wiki/Interferometer</a>)</p>
<p><img src="http://i.stack.imgur.com/9YzLF.png" alt="Michelson Interferometer"></p>
<p>The incident beam is split into two... | g19034 | [
0.03480705991387367,
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0.041035208851099014,
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<p>Much is made of finding exoplanets in habitable zones, locations with orbital semi-major axes permitting water in the liquid state. Habitability may be compromised if such bodies become tidally locked, orbiting within the star's tidal lock radius. The illustration below shows the tidal lock radius for various stella... | g19035 | [
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0.05187177285552025,
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0.007314175367355347,
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<p>Consider a metal plate, on which a light of appropriate wavelength is incident such that it creates an interference pattern. The wavelength is chosen such that it can cause detectable photo-electric emission.</p>
<p>If we observe only the part of the metal where the light interferes destructively, two things can ha... | g19036 | [
0.043906308710575104,
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<p>I know that</p>
<p>$$p+\bar{p}\to 4\pi^++4\pi^-+(\gamma)$$</p>
<p>Before the collision, the sum of absolute electric charge value is $2$.</p>
<p>$$\left | +1 \right |+\left | -1 \right |=2$$</p>
<p>After the collision, the $p$ collapses to $4\pi^+$, and $\bar{p}$ collapses to $4\pi^-$.</p>
<p>After that, $4\pi^... | g19037 | [
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0.008... |
<p>(My questions are at the end, but they may not mean much without explanation below.)</p>
<p>Galileo argued that because the mass of a falling object can always be redistributed in ways that asymptotically approximate a set of smaller falling objects, e.g. linked by light strings, then the equations of motion for an... | g19038 | [
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<p>I'd like to know what are the basic equations of <a href="http://en.wikipedia.org/wiki/Electromagnetism" rel="nofollow">electromagnetism</a>, that can be used to formulate all the other laws and equations.</p>
<p>Those basic equations I can think of are Maxwell equations, Lorentz force equation and Coulomb's law. W... | g19039 | [
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<p>I recently watched a <a href="http://www.discovery.com/tv-shows/mythbusters/videos/a-helmet-full-of-body.htm" rel="nofollow">Mythbusters episode</a> where they tested decompression in a tethered diving suit (which I believe is a <a href="http://en.m.wikipedia.org/wiki/Standard_diving_dress" rel="nofollow">Standard D... | g19040 | [
0.011507843621075153,
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<p>In the book "Statistical Physics, Part I ($3^{{\rm rd}}$ edition)" by Landau and Lifshitz, at $\S59$ when he treats the diamagnetic part of the magnetisation of a degenerate electron gas for weak fields ($\mu_BH\ll\varepsilon_F$, where $\varepsilon_F$ is the Fermi energy), he says that the energy levels of the orbit... | g19041 | [
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<p>When grounded, can an insulative material keep its charge for any measurable length of time? Or, I suppose, if it was a perfect insulator, would it discharge at all?</p>
<p>An example might be a charged rubber tire placed on the ground.</p> | g19042 | [
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<p>As we known, to express the position operator $x$ in terms of the creation and annihilation operator $a^{+}$ and $a$, one way is:<br>
$$x= \sqrt{\frac{\hbar}{2\mu\omega}}(a^++a);$$</p>
<p>$$p= i\sqrt{\frac{\mu\hbar\omega}{2}}(a^+-a).$$</p>
<p>But how about </p>
<p>$$x= -i\sqrt{\frac{\hbar}{2\mu\omega}}(a^+-a);$$<... | g19043 | [
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<p>Why is it that if I'm sitting on a seat on a bus or train and its moving quite fast, I am able to throw something in the air and easily catch it? Why is it that I haven't moved 'past' the thing during the time its travelling up and down?</p> | g620 | [
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<p>I've a problem to reproduce the result in equation (4) on page three of this paper: <a href="http://arxiv.org/abs/0802.2588" rel="nofollow">http://arxiv.org/abs/0802.2588</a>.</p>
<p>So far I've understood that they apply a Heisenberg XXX interaction between 2&4, 4&6, 1&3 and 3&5. After this they me... | g19044 | [
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<p>What does 1/k represent regarding Newtons Law of Cooling?<br>
I know k represents the cooling constant. I think the inverse of k is the time taken for the liquid to cool from its maximum temperture to surrounding temperature. Any clarification would be most appreciated.</p> | g754 | [
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<p>This is something probably very basic but I was led back to this issue while listening to a recent seminar by Allan Adams on holographic superconductors. He seemed very worried to have a theory at hand where the chemical potential is negative. (why?)</p>
<ul>
<li>For fermions, isn't the sign of the chemical potenti... | g239 | [
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<p>In <a href="http://arxiv.org/abs/0909.2207v4" rel="nofollow">this</a> paper the authors refer to</p>
<blockquote>
<p>transverse susceptibility $\chi_{ \perp}$ [meV $^{−1}$]</p>
</blockquote>
<p>I was taught that the magnetic susceptibility is dimensionless.</p>
<p>How do I get $\chi$ in the above units??</p> | g19045 | [
0.023784972727298737,
0.029545748606324196,
-0.005678138229995966,
-0.011268285103142262,
0.039619605988264084,
0.023911604657769203,
-0.003075037384405732,
0.05957436189055443,
-0.03058004565536976,
0.015492935664951801,
-0.0563720278441906,
0.08766685426235199,
-0.0002014820056501776,
-0... |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://physics.stackexchange.com/questions/6582/what-sort-of-jobs-do-physics-graduates-with-b-sc-m-sc-get">What sort of jobs do physics graduates with B.Sc/M.Sc get?</a> </p>
</blockquote>
<p>I've been told over and over again..."I would not majo... | g584 | [
-0.014714931137859821,
0.018091151490807533,
0.009810402989387512,
0.004083713050931692,
0.003489120164886117,
-0.004489010665565729,
0.005691625643521547,
0.016614612191915512,
0.03371593728661537,
-0.03889482840895653,
0.02444673515856266,
0.011213775724172592,
0.03277591988444328,
-0.03... |
<p>So I am trying to derive an expression for electron temperature based on the voltages on a triple Langmuir probe. I have pretty much been following the triple Langmuir probe derivation on <a href="http://en.wikipedia.org/wiki/Langmuir_probe#Triple_probe" rel="nofollow">wikipedia</a> but I cannot reproduce their resu... | g19046 | [
-0.004438410513103008,
-0.025417067110538483,
-0.006557746324688196,
-0.039187122136354446,
0.062468670308589935,
-0.004315030761063099,
-0.019204609096050262,
0.05344778299331665,
-0.023603424429893494,
0.047245681285858154,
-0.010548530146479607,
0.0358731783926487,
-0.0026485593989491463,... |
<p>Do the laws of physics allow for the possibility that in a galaxy far far away, the perceived arrow of time is in the opposite direction to ours, where people (aliens) die before they are born, and from our perspective appear to be living through time in the wrong direction?</p> | g19047 | [
-0.003948161378502846,
0.0047943852841854095,
0.005113155581057072,
-0.004966034088283777,
0.044486384838819504,
0.0444403775036335,
0.010537688620388508,
-0.020046617835760117,
-0.0027771538589149714,
0.029912762343883514,
0.09068436920642853,
0.020153701305389404,
0.0648060217499733,
-0.... |
<p>So atoms are formed from protons and neutrons, which are formed from quarks.</p>
<p>But where do these quarks come from? What makes them?</p> | g324 | [
0.04808324947953224,
0.0021253919694572687,
-0.010044310241937637,
-0.04084758833050728,
0.026036612689495087,
0.04434101656079292,
-0.06163780763745308,
0.04470231011509895,
0.015956303104758263,
-0.02844991721212864,
-0.03651084378361702,
-0.006914801895618439,
0.02301575243473053,
-0.00... |
<p>For pilots of gliders or sailplanes, the 'thermal' is the most important phenomena of the air. A thermal is classically described as an upward flow of air caused by ground level heating of air that rises in bubbles or a connected stream of warmed air. Given sufficient velocity of the rising air, a gliding craft, b... | g19048 | [
0.013068974018096924,
0.013492247089743614,
0.011735795065760612,
-0.03728337213397026,
-0.0067389532923698425,
0.03665068373084068,
-0.000405868049710989,
0.021144239231944084,
-0.012802038341760635,
-0.028029918670654297,
0.04177962988615036,
-0.0010677027748897672,
0.08359463512897491,
... |
<p>Is it possible to build, today, a personal aircraft that not use an impracticable amount of fuel for everyday use? What are the physical concepts that could be used to build it?</p> | g19049 | [
-0.041278209537267685,
0.05459066852927208,
0.013108117505908012,
0.04506804794073105,
-0.049081191420555115,
-0.023817474022507668,
-0.04390614852309227,
-0.004009620752185583,
-0.07419361919164658,
-0.049769327044487,
0.06608422845602036,
-0.05543641000986099,
0.007725255563855171,
0.020... |
<p>When an electron is excited from valence band to conduction band, it has to have a finite momentum in the case of indirect bandgap. Does that mean that the electron cannot be created at rest ? does it have a non zero "speed" ?</p> | g19050 | [
-0.007284785155206919,
0.00915435515344143,
-0.010906151495873928,
-0.02368788979947567,
0.08913205564022064,
-0.011680197902023792,
0.027487382292747498,
0.0053278300911188126,
0.008491603657603264,
0.021565187722444534,
-0.03454388305544853,
0.03356671705842018,
-0.030521828681230545,
-0... |
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