question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>I am new to Quantum Mechanics. I read the uncertainty principle - it says there are pairs of physical quantities which can't both be determined with certainty for a particle.</p>
<p>My question is does the same apply to a system of particles - the nucleus for example ? Can we determine both the position and momentu... | g10557 | [
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<p>The clumsy "almost-commutative graviton" is provocative. I use it on purpose, to ask two questions in one :</p>
<ul>
<li><p><strong>Is the observation of only one Higgs and no supersymmetric particle below 8 TeV (up to now) a sufficient evidence to substantiate the almost commutative spectral model?</strong> </p></... | g10558 | [
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<p>I got this question in a assignment and haven't been able to figure out how to get to the correct result.</p>
<blockquote>
<p><em>A force of 6 newtons and a force of 10 newtons can be combine to form
a resultant of what magnitude?</em></p>
<p><em>Ans ( 8 newtons )</em></p>
</blockquote>
<p>I though this w... | g10559 | [
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<p>This was a statement given in my class:</p>
<p>"<a href="http://en.wikipedia.org/wiki/Strangeness" rel="nofollow">Strangeness</a> is conserved in the <a href="http://en.wikipedia.org/wiki/Strong_interaction" rel="nofollow">strong</a> and electromagnetic interactions, but not in a <a href="http://en.wikipedia.org/wi... | g10560 | [
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<p>Given the lack of financial efficacy in the medical industry, I was wondering if nuclear magnetic resonance imaging would be possible with a copper/silver coil if the use is short 10 second imaging bursts.
Or is the resistance simply too disruptive for any imaging to occur?</p>
<p>What I had in mind is a very small... | g10561 | [
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<p>I would like to know whether a ball bounces back normally if you throw it against an oily wall. Like a wall watered down with oil.
Basically I want to know if it will actually slip before bouncing back or not?</p> | g10562 | [
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<p>Sometimes, when we have a certain line element and we are given a worldline parametrised by a path parameter that is not necessarily proper time I don't completely understand some of the standard manipulations done. A specific example:</p>
<p>Godel spacetime has the line element $ ds^2=a^2(dt^2-dr^2 + f(r)d\phi^2 +... | g10563 | [
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<p>I'm studying a diagrammatic approach to degenerate electron gas. Now I need to prove that the energy contribution, with an arbitrary potential, of polarization at first perturbative order given by the diagram:
<img src="http://i.imgur.com/pECT8IX.png" alt="Diagramma">
is null. I expanded it as an integral:
$$
\Pi_{(... | g10564 | [
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<p>As a person who will be using the scattering measurement results (in Zemax), I was asked to prepare the specs for the <a href="http://en.wikipedia.org/wiki/Bidirectional_reflectance_distribution_function" rel="nofollow">BRDF</a> measurement. However I've never done it until now, so help would be greatly appreciated.... | g10565 | [
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<p>what do they mean by "in a weak interaction, quark flavor can change"</p>
<p>I know that in a weak interaction strangeness is conserved... so is this what the statement is referring to.</p> | g10566 | [
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<p>Suppose we have a qubit in state $| \Psi \rangle = \alpha | 0 \rangle + \beta | 1 \rangle$</p>
<p>Suppose we expose this to decoherence, which we will express as the state $| R \rangle$ such that
$$| 0 \rangle| R \rangle \rightarrow | 0 \rangle| R_0 \rangle$$
$$| 1 \rangle| R \rangle \rightarrow | 1 \rangle| R_1 \r... | g10567 | [
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<p>The question asked me to find the potential at a distance $r$ from the center of a charged sphere, where $r>r_0$ of the sphere. </p>
<p>Actually, the question is answered, but what is confusing me is that the author took 2 points out of the sphere ($a$ & $b$) and calculated the potential difference between t... | g10568 | [
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<p>As far as I can tell within an Fourier Transform Spectrometer the spectral information is gained from changing the path length along one arm, this sounds very similar to a michelson interferometer but using two apertures instead of one.</p>
<p>So are there any underlying differences between the two? </p> | g10569 | [
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<p>I am trying to find an approximate value of the electrical conductivity $\sigma$ of graphene in units of S/m or S/cm. <a href="http://en.wikipedia.org/wiki/Electrical_resistivity_and_conductivity#Resistivity_of_various_materials" rel="nofollow">This table on Wikipedia</a> gives $\sigma$ values for a variety of mate... | g10570 | [
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<p>in this video at arround 0:47 they deliver the 'dry pots' to the under water lab, bellow the water and they seem to swim up into an opening where it is completly dry.. how is this dry, surly the water would fill into that void seeing as its under water ?</p>
<p>Sorry if this is such a basic quesiton !</p>
<p><a hr... | g10571 | [
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<p>Is there any current estimate of the electroweak vacuum lifetime based on the recent measurement of the Higgs boson and the top quark masses?</p> | g10572 | [
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<p>Excitons can be observed when we excite electrons to the conduction band.</p>
<p>I don't know about excitons being observed when we excite the electrons to an electronic level that would eventually be in the middle of the bandgap.</p>
<p>Why? Is it related with the binding energy, density of states of the level, o... | g10573 | [
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<p>The BICEP2 paper reports a tensor/scalar ratio $r = 0.20_{-0.05}^{+0.07}$, but then says:</p>
<p>Subtracting the various dust models and re-deriving the r
constraint still results in high significance of detection. For
the model which is perhaps the most likely to be close to reality
(DDM2 cross) the maximum likeli... | g10574 | [
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<p>How does the <a href="http://www.google.com/search?q=tester+screwdriver+work" rel="nofollow">tester screwdriver work</a>? If I put the tester screwdriver inside a "phase" hole of an electric socket, it lits up. If I press my finger against the metal cap on top of the screwdriver. This happens also if I stand on a su... | g10575 | [
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<p>I am tring to find the eigenvectors of a two spin system, with $j_1=3/2$ and $j_2=1/2$. To start,
$$m_1 =-3/2,-1/2,1/2,3/2$$
$$m_2=-1/2,1/2$$
For $j_1$, there are 4 possible states, and 2 possible states for $j_2$. $(2j+1)$. Now, I get confused. I am looking for
$$|S,m\rangle=\sum_{m_1+m_2=m}CG|s_1m_1\rangle|s_... | g10576 | [
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<p>How much of a difference would it make if every roof, road and vehicle were painted white? This would certainly reduce the urban heat island effect but how much of a difference would it make to total scattered insolation? Apologies in advance for this the bizarre question.</p> | g10577 | [
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<p>It is well known that stable, traversable wormholes require exotic matter that violate the dominant energy conditions.</p>
<p>For the purpose of the question, let's assume enough exotic matter can be created for a brief period of time, where the wormhole mouths are stable and traversable. Additionally, suppose that... | g10578 | [
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<p><strong>Problem statement</strong>: The Hamiltonian of a system is given by the formula:</p>
<p>\begin{equation*}
H = \frac{p_r^2}{2m} + \frac{p_\theta^2}{2mr^2} + V(r,\theta).
\end{equation*}</p>
<p>Under what condition is $f=p_\theta^2$ an integral of motion?</p>
<hr>
<p><strong>Attempted solution</strong>:</p... | g10579 | [
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<p>While mapping out the position, distance and movement of galaxies and <a href="http://en.wikipedia.org/wiki/Quasar" rel="nofollow">quasars</a> at the limits of the observable universe, have astronomers ever observed the motion of these object due to gravitational sources that may reside outside the limits of the obs... | g10580 | [
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<p>I would like to learn how scientists go about measuring the large-scale curvature of the universe to determine if the universe is closed 'i.e. spherical', flat, or open 'i.e. saddle shaped'.</p>
<p>My simplistic thought is that you could measure the corner angles of a really large triangle and see if they add up to... | g10581 | [
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<p>How does the optical zoom works..</p>
<ol>
<li>Does it brings the light closer to the object... Or</li>
<li>Does it just enlarges the picture of the object.</li>
</ol>
<p>In other words... Suppose I have telescope with 1 light-year zoom capacity, could I see stars 1 year ahead of its light reaching earth...</p>
<... | g10582 | [
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<p>I know that we have some solar system analogs. But is there a limit to it?</p> | g10583 | [
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<p>Provided that I have the instantaneous positions and velocities of two particles that can separate in 3D with respect to time. I would like to characterize the change in length. What could be a good formulation for that? Thanks.</p> | g10584 | [
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<p>How can I reduce the double image seen when looking through binoculars? I recently got a new pair, but have been having troubles using them because I am seeing double...</p> | g10585 | [
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<p>It's known that single spherical lens cannot focus parallel beam of monochromatic light into single point.</p>
<p>Could you suggest how should aspherical lens look like to be able to focus in single point (again, light is monochromatic)? Do we need conic factor, or higher components?</p>
<p>Could you suggest any d... | g10586 | [
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<p><strong>Background:</strong> I'm in a legal academic discussion about the status of electronic 'goods' and whether they qualify as 'goods' in the same way a chair and a pen do. In this context (and specifically at the exact circumstance under discussion), it matters if electricity is 'tangible'. So far, most authors... | g10587 | [
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<p>To be more specific, what I mean is to measure it in a experiment.
And if the answer is no, I want to know if it is principally impossible, or just impossible due to the technic limitation of our time. </p>
<p>I am sorry I wan't clear enough at first.
For most of the times, in the progress of experiment, the syste... | g10588 | [
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0.... |
<p>In the case of the B-mode detected in BICEP2, at first they assumed there was no circular polarization and then the Q and U stocks parameter of the CMB is given by E-mode and B mode. If we have circular polarization too, what is relation between the B-mode and circular polarization? Does this B- mode include... | g10589 | [
-0.007216800469905138,
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0.06511823832988739,
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-... |
<p>In all text books (and papers for that matter) about QFT and the classical limit of relativistic equations, one comes across the "minimal substitution" to introduce the magnetic potential into the equation (Schrödinger/Dirac/Klein-Gordon) through:
$$ \hat{p}^2 \rightarrow (\hat{p} - e \hat{A})^2$$</p>
<p>The wordin... | g10590 | [
0.0248319823294878,
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0.027847548946738243,
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0.0007340004667639732,
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... |
<p>I know that integrating acceleration twice will give me position (acceleration-->velocity-->position) but how can I do all this when I all I have are a set of data points (ex: 1 second = some # m/s^2); how can I take these data points and integrate them?</p>
<p>Does this have something to do with <a href="http://en... | g10591 | [
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0... |
<p>Why is straight gasoline (or whetever the mixture was before the introduction of ethanol) more efficient (ie, more miles/gallon) than E85? I've known since it's introduction that E85 was less efficient, but why is it?</p> | g10592 | [
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0.014487959444522858,
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<p>Our galaxies are speeding apart from each other and that is because of dark energy, but we don't know where it comes from right? If I'm not mistaken could dark matter have dark energy? (If they are the same thing please correct me.) Matter has gravity so could <a href="http://en.wikipedia.org/wiki/Dark_matter" rel="... | g337 | [
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<p>I'm looking for a pedagogic introduction to d-wave superconductivity.</p>
<p>Ideally, this would involve a derivation of d-wave superconductivity and the form of the gap parameter from some fundamental Hamiltonian (if such a derivation is even possible).</p>
<p>Books and papers are welcome.</p> | g10593 | [
0.014518262818455696,
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0.0017195973778143525,
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<blockquote>
<p>If $55 034.175 \rm{kJ }$ of heat are transferred to $150 \rm{kg}$ of ice at a temperature of $-12.15 ^\circ \rm{C}$, calculate the temperature of the resulting water.</p>
</blockquote>
<p>Using $Q = mc(t_2-t_1)$ or $t_2 = \frac{Q}{mc}+t_1$,</p>
<p>$$t2 = \frac{55034.175}{150 \times 2.135} + (-12.1... | g10594 | [
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0.044063977897167206,
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<p>A point-like particle $A$, coming from minus spatial infinity, heads at another one, $B$, with an <a href="http://en.wikipedia.org/wiki/Impact_parameter" rel="nofollow">impact parameter</a> of $b$.
Initial momenta are $p_A$ and $p_B=0$.</p>
<p>They repel each other via a <a href="http://en.wikipedia.org/wiki/Yukawa... | g10595 | [
0.05483775585889816,
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<p>I have never understood what's the meaning of the sentence "rolling without slipping". Let me explain.</p>
<p>I'll give an example. Yesterday my mechanics professor introduced some concepts of rotational dynamics. When he came to talk about spinning wheels he said something like: </p>
<blockquote>
<p>"If the whe... | g10596 | [
0.03926275670528412,
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0.032082... |
<p>Goldstein's mechanics book, on the chapter on relativistic mechanics says that "We cannot assume that all observers make the same division into time and space in the same way." What does it mean to "divide" spacetime?</p> | g10597 | [
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0.0... |
<p>Im looking for some references here. I hope it is the right place to ask.</p>
<p>I need to find a table of (or a formula from which to extrapolate) the matrix elements of the radial functions of the hydrogen atom evaluated in powers of $r$ for both diagonal and off-diagonal elements. That is, I need this guys:</p>
... | g10598 | [
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0.025572439655661583,
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-... |
<p>I read somewhere what performing an orbifolding (i.e. imposing a discrete symmetry on what would otherwise be a compactification torus) is equivalent to "gauging the discrete symmetry". Can anybody clarify this statement in any way? In particular what does it mean to gauge a discrete symmetry if no gauge bosons and ... | g10599 | [
0.03019215352833271,
0.07333417236804962,
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-0.0250524... |
<p>I know that <a href="http://en.wikipedia.org/wiki/Classical_XY_model" rel="nofollow">XY statistical model</a> for $d=2$ doesn't show a regular phase transition , while the $3d$ has, I was wondering what is the behaviour for $2< d < 3$.</p>
<p>If it is simpler one could consider another model in its class of u... | g10600 | [
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<p>Newton's ring apparatus consists of a Plano-spherical glass which rests on its vertex on top if a horizontal surface. Reflection-interference occurs along the air wedge, and is seen as a series of concentric rings from above. You may assume the radius of convergence is much larger than the thickness of the wedge. </... | g10601 | [
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<p>If we want to transform to another inertial frame of reference using <a href="http://en.wikipedia.org/wiki/Galilean_transformation" rel="nofollow">Galilean transformation</a> in 4-dimensional space-time, what is the Jacobian matrix of Galilean transformation?</p> | g10602 | [
0.00410150783136487,
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0.03636385127902031,
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0.024006493389606476,
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0.029406758025288582,
0.004... |
<p>I was wondering if we have the chance to run on the Moon's surface, how would you expect it look like?
I expect our velocity will increase for the same work we do on Earth, but not sure if this will be multiples in term of gravity variations.</p>
<p>How do you think our maximum speed would reach?</p> | g10603 | [
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<p>Can we calculate the number of photons emitted per second by a radioactive source (gamma) ?
we can take 100g of barium-133 as an example</p> | g10604 | [
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0.05809115618467331,
0.01184943225234747,
-0.0... |
<p>Gravitational lensing is an observed phenomenon. Can one have a gravitational mirror? </p>
<p>A slightly unrelated question: Can gravitational waves be reflected?</p> | g10605 | [
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0.025... |
<p>So, I understand that for a NPN transistor to work the emitter-base junction needs to be forward biased and the collector-base junction needs to be reverse biased. I understand how current flows from the emitter to the base when forward biased, but I can't seem to wrap my head around how it flows from the emitter, ... | g10606 | [
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<p>I'm working on a science project and need to know what makes a strong electromagnet - more wire turns or more voltage? I understand energy can be lost to heat with too many wire turns.</p> | g10607 | [
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<p>Are there any packages that can simplify functional derivatives in path integrals? For instance the expression (integrate over, $x,y,z,u,v,r,s$): </p>
<p>$$\int\delta_{J_{A}^x}\delta_{J_{B}^x}\delta_{J_{B}^x}\int{J_{B}^y}\Delta^{yz}_B{J_{B}^z}\int{J_{B}^u}\Delta^{uv}_B{J_{B}^v}\int{J_{A}^r}\Delta^{rs}_A{J_{A}^s},$$... | g10608 | [
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<p>Suppose I have two neutrally-buoyant macromolecules diffusing in water. They have the same radius of gyration (i.e. same root-mean-square distance from their center of mass), but one of them is compact (its mass is roughly the cube of its size) and the other is extended (its mass is roughly the square of its size).<... | g10609 | [
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-0... |
<p><a href="http://physics.stackexchange.com/a/9910/22775">Kostya answered a question</a> that was asking what the diffraction pattern looks like for a hexagonal aperture in front of a lens. He lists an equation which was derived using a Heaviside function to describe the shape of the aperture.</p>
<p>I was wondering... | g10610 | [
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<p>Given a Hamiltonian of the form</p>
<p>$H=\sum_k \begin{pmatrix}a_k^\dagger & b_k^\dagger \end{pmatrix}
\begin{pmatrix}\omega_0 & \Omega f_k \\ \Omega f_k^* & \omega_0\end{pmatrix} \begin{pmatrix}a_k \\ b_k\end{pmatrix}$</p>
<p>where $a_k$ and $b_k$ are bosonic annihilation operators, $\omega_0$ and $\... | g10611 | [
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<p>I am nothing but a curious layman so don't go too technical on me.</p>
<p>First of all, I am well aware that a lot of people consider the question of determinism vs indeterminism to be unsolved and others claim it is solved. That is not what this post is about, so let's not digress into heated debates over the vali... | g10612 | [
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<p>I would like to compute the heat distribution of a piece of metal with some surrounding material. The heat is assumed to propagate by diffusion, so inside the metal piece and also on the outside, the governing law would famously be
$$
\rho c_p \frac{\partial u}{\partial t} = \nabla(\kappa \nabla u).
$$
What would be... | g10613 | [
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<blockquote>
<p><em>Two point charges a distance $d$ apart in free space exert a force of $1.4\times10^{-4}N$. When the free space is replaced by a homogeneous dielectric medium, the force becomes $0.9\times10^{-4}N$. What is the dielectric constant $\epsilon_r$ of the medium?</em></p>
</blockquote>
<p>I have been s... | g10614 | [
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<p>When work is done on a positive test charge by an external force to move it from one location to another, does the potential energy increases or decreases, and does the electric potential increases or decreases?</p> | g10615 | [
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<p>I have a given Lagrangian: </p>
<p>$$L= e^{st}\cdot\frac12\cdot(mv_y^2-ky^2)$$</p>
<p>And are asked to identify the equations of motions, the constants of motions and physical system. </p>
<p>Without the exp-time-term, this wold be a harmonic oscillator with the solution</p>
<p>$$\frac{d^2y}{dt^2} = -\left(\frac... | g10616 | [
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<p>I have been studying scattering theory in Sakurai's quantum mechanics. The phase shift in scattering theory has been a major conceptual and computational stumbling block for me.</p>
<p>How (if at all) does the phase shift relate to the scattering amplitude?</p>
<p>What does it help you calculate?</p>
<p>Also, an... | g10617 | [
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... |
<p>Can someone please help me explaining how to convert units in problems like the one below? I've done many things, but I am very unsure of all my methods. Could you tell me what steps should I take?</p>
<p>$$5.66\ \frac{\mathrm{hm}}{\mathrm{min.}} \frac{\hspace{2cm}}{}\frac{\mathrm{km}}{\mathrm{hr.}}$$</p>
<p>Thank... | g156 | [
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<p>I have read that the fine structure <a href="http://www.physorg.com/news202921592.html">constant may well not be a constant</a>. Now, if this were to be true, what would be the effect of a higher or lower value? (and why?)</p> | g10618 | [
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<p>Another Noether's theorem question, this time about electrical charge.</p>
<p>According to Noether's theorem, all conservation laws originate from invariance of a system to shifts in a certain space. For example conservation of energy stems from invariance to time translation.</p>
<p>What kind of symmetry creates ... | g823 | [
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<p>When it rains and water flows down an inclined street, ripples may form that are carried along with the current. Here's a picture with an example of what I'm talking about</p>
<p><img src="http://i.stack.imgur.com/b3rj5.jpg" alt="enter image description here"></p>
<p>I'd like to know what the fluid mechanical mech... | g10619 | [
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0.0345066... |
<p>So in wired/wireless networking and radio, signals are sent in form of wave. Then the concept of bandwidth comes in, which is the difference between highest frequency and lowest frequency in a signal. But I do not get why bandwidth determines the maximum information per second that can be sent. If we are able to sen... | g10620 | [
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<p>What formula defines a curve for a nose cone with the minimal possible drag?</p>
<p>The nose cone is attached to a cylinder (assume it goes on forever).
The volume of the nose cone is not relevant.
The nose cone isn't near the ground. And the object will be traveling at 20m/s max.</p>
<p>So far, I've been using t... | g10621 | [
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<ol>
<li><p>Which transformations are <a href="http://en.wikipedia.org/wiki/Canonical_transformation" rel="nofollow">canonical</a>? </p></li>
<li><p>Why do canonical transformations <a href="http://en.wikipedia.org/wiki/Liouville%27s_theorem_%28Hamiltonian%29" rel="nofollow">preserve</a> the measure of integration in p... | g10622 | [
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<p>I have the following setup:
<img src="http://i.stack.imgur.com/DTy61.png" alt="Tightening a string"></p>
<p>The string of negligible mass, causing little friction, is shown in dark blue and is fixed at the red circle. The taut string is shown in light blue (with excess string removed). I have shown an orange arrow ... | g10623 | [
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... |
<p>What's the difference between Feynman rules in momentum space for $\phi^3$ theory and for $\phi^4$ theory?</p>
<p>I know it's only a slight difference and perhaps found in the vertex factor? But for some reason I can't seem to find this difference anywhere.</p> | g10624 | [
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<p><strong>Is there anyway to recreate this experiment with <em>detectors</em> at home?</strong></p>
<p>I want detectors because I want to get non interference pattern too.
I have a little know-how in electronics so If I need to buy a detector there wouldn't be a problem using it. The thing is I don't know which detec... | g10625 | [
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<p>If $S_F(x-y)$ is the Green's function for the Dirac operator $(i\gamma^\mu\partial_\mu-m)$, that is, I assume the following matrix equation holds: $$ (i\gamma^\mu\partial_\mu-m)S_F(x-y)=i\delta(x-y) $$</p>
<p>The adjoint dirac equation is:
$$ -i\partial_\mu\bar{\psi}\gamma^\mu -m\bar\psi=0 $$</p>
<p>I am looking f... | g10626 | [
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<p>Schwarschild found his solution to Einstein's field equations for vacuum ($T_{\mu \nu}=0$) by placing a point-mass in the center of origin.</p>
<p>Since the Ricci tensor $R_{\mu \nu}$ and the Einstein tensor $G_{\mu \nu}$ are trace-reversed, meaning they vanish identically:</p>
<p><strong>Which point of a universe... | g10627 | [
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<p>I am studying diagonalization of a quadratic bosonic Hamiltonian of the type:</p>
<p>$$ H = \displaystyle\sum_{<i,j>} A_{ij} a_i^\dagger a_j + \frac{1}{2}\displaystyle\sum_{<i,j>} [B_{ij} a_i^\dagger a_j^\dagger + B_{ij}^* a_j a_i ]
$$</p>
<p>in second quantization.<br>
Also, $A = A^\dagger$ and $B ... | g10628 | [
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<p>The <a href="http://en.wikipedia.org/wiki/Renormalization_group">renormalization group</a> equation is given by:
\begin{equation}
\left[\mu \frac{\partial}{\partial \mu} + \beta \frac{\partial}{\partial g} + m \gamma_{m^2} \frac{\partial}{\partial m} - n \gamma_d \right] \Gamma^{(n)}(\{p_i\};g,m,\mu) = 0
\end{equa... | g10629 | [
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<p>I have always thought that the time is discrete (jumping), not continuous and the shortest time is <code>Planck Time</code>. One reason for that was the information on <code>Wikipedia</code> and another was the following note I read in a book:</p>
<blockquote>
<p>If you throw a rock to a tree, the rock will go ha... | g10630 | [
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<p>This is what I understand so far: in a conductor, the ions have a weak pull on the valence electrons. So when an electric field is applied, the free electrons are able to easily move about. Makes sense.</p>
<p>In a neutral conductor with no electric field, the free electrons aren't bound to any ions. Why? I underst... | g10631 | [
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<p>I am a n00b to physics. What physics I know comes from high school and popular science books.</p>
<p>At school we were taught about atoms and what make up atoms, but we weren't actually told what the particles were!</p>
<p>So sure an atom has electrons orbiting around a nucleus made of protons and neutrons, but wh... | g10632 | [
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<p>This calculation is for a double slit experiment setup which is experiencing a far field radiation from an extended monochromatic thermal source. I assume the source is 1-D and it's length is $b$. Here is the schematics.</p>
<p><img src="http://i.stack.imgur.com/VRbiW.jpg" alt="enter image description here"></p>
<... | g10633 | [
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<p>I am looking for an expression for the velocity of a micron sized (1 - 10 micron diameter) sized particles under accelerating forces.</p>
<p>I have aerosols in mind.</p>
<p>This is what I have in mind
The resisting force acting on the particle is </p>
<p>$F_D = 3 \pi \mu Vd$ so its (mechanical) mobility is $\frac... | g10634 | [
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<p>Suppose that a spherical metal sphere with mass $m=10^{-16}kgr$ radius $R=10μm$ charge $Q=10^{-9}C$ travels with $v=c/3$ and is trapped in the earth's magnetosphere at a distance around $r = 1000km$. <em>The exact numbers are not that important, I am providing them for order of magnitude considerations</em>. </p>
<... | g10635 | [
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<p>Is it true that every point in the universe is connected or could be so theoretically? If so how is this mediated?</p>
<p>Is it through the quantum nature of the fabric of space or is it through the interrelationships of the gravity fields throughout the universe. From the gravity fields of single solar systems aff... | g10636 | [
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<p>I am performing a simulation involving growth of bacteria. This is an agent-based simulation where the solutes (glucose, oxygen etc.) are represented as a concentration field discretised over space, and the bacteria are discrete objects in a continuous space (spherical blobs with a size, mass and position).</p>
<p>... | g10637 | [
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... |
<p>If an external EM field (a laser, for example) act on a dielectric (a glass, for example) what will be the effect of this field on the dielectric constant and on the refractive index of the material? How, mathematically speaking, could I explain what is happen? </p> | g10638 | [
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<p>I am looking for interesting ways to introduce the Doppler effect to students. I want some situations in nature or every day life, where a student is possibly surprised and may ask "how could it be"?</p>
<p>The common example for Doppler effect of sound waves is the siren of a moving emergency vehicle. Clearly the ... | g10639 | [
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<p>This question is in reference to the first ~15 minutes of this String Theory lecture by Prof.Shiraz Minwalla,</p>
<p><a href="http://theory.tifr.res.in/Videos/strings28_24sep08.mp4" rel="nofollow">http://theory.tifr.res.in/Videos/strings28_24sep08.mp4</a></p>
<p>Can one give a reference (paper/review/book) for thi... | g10640 | [
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<p>Why are these states called as such, and how do they differ? I vaguely understand that when $E > 0$ you obtain a scattering state, but when $E < 0$ you have a bound state.</p> | g10641 | [
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<p>I need to process some images taken from a telescope to determine the intensity of an astroid.
This way I can determine the rotation period of this asteroid. </p>
<p>The pictures were taken the usual way (I guess, I'm not an astronomer, this is a school project), setting the telescope to track a nearby star. I wou... | g10642 | [
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<p>As an aeroplane accelerates through the Earth's B-field, it experiences a changing flux $d\phi \over dt$ and a potential difference is induced along its wings. </p>
<p>Given the wings are made of metal and act as a continuous conductor, current flows along the wings in a direction perpendicular to the vertical comp... | g10643 | [
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<p>I wonder if there is some simple theory of what determine <strong>efficiency ( speed, energy end force required )</strong> of cutting by edge ( <strong>blade , knife, sword</strong> )</p>
<hr>
<p>At least something phenomenological like in case of <strong>friction</strong> ( which I guess is very much related to c... | g10644 | [
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<p>When calculating time period of simple pendulum (an approximation of SHM at small amplitudes) we take gravitational force greater than tension in string and resolve gravitational force in two orthogonal components and equate one of them with tension.While in case of conical pendulum we take tension greater than grav... | g10645 | [
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<p>I've been tasked to do a simple experiment on the elasticity of collisions. For this experiment I used two "pucks" (very light circular metal pieces of certain height but hollow) and a table that works like air hockey tables (decreases friction by blowing air from underneath). One puck was placed on this board and t... | g10646 | [
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<p>People always talk about finding good dark matter (DM) candidates of beyond Standard Model (SM) theories. To be a proper candidate the particles should not decay into the SM particles and could potentially be weakly interacting mass particles (WIMPs), but this doesn't need to be the case. If DM is not composed of WI... | g10647 | [
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<p>Consider a two-level energy gap with electronic energy states $E_1$ & $E_2$ and associated population densities $n_1$ and $n_2$ with $E_2>E_1$.</p>
<p>In the derivation of the Einstein coefficients for <em>Absorption</em>, <em>Spontaneous Emission</em> and <em>Stimulated Emission</em>, textbooks/notes quite ... | g10648 | [
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<p>According to Newton, if no external net force acting on a system then the system will keep its initial condition whether at rest or moving uniformly in a straight line.</p>
<p>Let's consider a boy riding a bicycle. He exerts a force to the bicycle and the bicycle reacts with the same magnitude but opposite directio... | g10649 | [
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<p>I've been looking for the relation between moment of a tennis racket and its maneuverability. If I define maneuverability as the easiness to get in position for quick reaction strokes like volleys and returns, does low moment indicate high maneuverability? I seem to get the answer from this site <a href="http://www.... | g10650 | [
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<p>I would like to know the probability of return to the initial point in three dimensional Brownian motion. Does someone know an expression for the diffusion constant? (Suggestions of books on this would also be welcome)</p> | g10651 | [
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<p>In <a href="http://motls.blogspot.com/2012/04/is-lhcs-125gev-higgs-boson-extra.html#more" rel="nofollow">this</a> article, Lumo introduces and explains the idea (presented by the original authors in <a href="http://prl.aps.org/abstract/PRL/v108/i14/e141602" rel="nofollow">this</a> paper) that the LHC signal at abou... | g10652 | [
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<p>I don't know if this is the place to ask this kind of questions but I'm sure you guys can help me. I'm looking for a small (4 pages max.) technical explanation of nuclear energy, preferably of an academic source. It would be best if the physics and mathematics involved is understandable by last-year high school stud... | g10653 | [
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