question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
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<p>In discussions around a recent <a href="http://physics.stackexchange.com/questions/4172/what-does-john-conway-and-simon-kochens-free-will-theorem-mean/4227#4227"> Stack answer</a> which covered axiomatic quantum mechanics, Bell's Theorem and Random Fields (related to axiomatic QFT) the phrase "Heisenberg Cut" was us... | g8887 | [
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<p>How do you go about creating a stream of single file atoms?</p>
<p>The aim is to fire a stream of single file atoms (hydrogen, helium) down a vacuum and detect there arrival on the opposite end. Any tips/papers would be a great help. </p> | g8888 | [
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<p>How do we measure mean part or time average of a (known) velocity field?</p>
<p>In other words, if I know velocity field how can I measure its time average or mean part?</p>
<hr>
<p>What is time average in general?</p> | g8889 | [
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://physics.stackexchange.com/questions/12175/book-recommendations">Book recommendations</a> </p>
</blockquote>
<p>So I'm a Junior level math major. I've seen some abstract algebra, some differential geometry, and some lie theory. I'm curren... | g98 | [
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<p>I was reviewing a paper of coupling to vector field and tensor field. I have got stuck with the term $$A_k \varepsilon^{kmn}\partial_mV_n=V^{T}.(\nabla\times A^{T})-\nabla.(A^{T}\times V^{T})+V^{T}.(\nabla\times A^{L})-\nabla.(A^{L}\times V^{T})$$ Where $A^T$ and $V^T$ are the transverse part of vector $A$ and $V$ ... | g8890 | [
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<p>How could electric fields in these waves propagate through space although in space there's no electrons for the electric field to be formed? is there another type of charged particles that carry the electric field?</p>
<p>How could the electric field exist without charges?</p> | g8891 | [
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<p>It is well known that in special relativity observers can disagree on the time ordering of two events.</p>
<p>It is also well known that entangled particles exhibit so called spooky action at a distance.</p>
<p>Today I read in the <a href="http://www.newscientist.com/article/mg21528834.700-new-maths-triggers-a-cal... | g8892 | [
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<blockquote>
<p><em>A racing car driver drives his car on a flat circular track of radius $\frac{25}3 m$ and a coefficient of friction $0.5$. Find the magnitude of its tangential acceleration (in $ms^{-2}$) at an instant when car starts slipping at a speed of $5 ms^{-1}$.</em> </p>
</blockquote>
<p>I found the centr... | g8893 | [
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<p>Is it possible for a particle trapped in a 1D finite potential well to evolve from a even state to an odd state and vice-versa? Why?</p> | g8894 | [
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<p>How could the potential difference be constant across all the resistors of parallel connecting resistors although each resistor has a specific resistance?</p> | g8895 | [
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<p>In the first SuSy lecture last week following theory of two real scalar fields has been considered as a first example: </p>
<p>$$\mathcal{L}=(\partial_\mu \phi_1)^2/2+(\partial_\mu \phi_2)^2/2-m^2(\phi_1^2+\phi_2^2)/2$$</p>
<p>which has the usual equation of motion $$(\Box+m^2)\phi_i=0;\quad i=1,2$$ Then the profe... | g8896 | [
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<p>What is a good example of a simple, physically useful <em>nonlinear</em> symplectomorphism $\kappa: \mathbb{R}^{2n} \rightarrow \mathbb{R}^{2n}$? I'm not much of a physicist, and all the examples I've worked have been purely mathematical and not connected to any physical problems. Obviously linear examples are well ... | g8897 | [
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<p>I'm having a hard time to find a good (and modern) classification scheme for phase transitions and related universality classes. Can someone recommend a paper/book/site? Detailed mathematical aspects are very much welcome.</p> | g8898 | [
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<p>Is it correct to visualize operators existing as matrices parameterized by spacetime coordinates in the context of QFT?</p> | g8899 | [
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<p>During discussion on another question, the question of singularties in modern physical theories arose. The big-bang is an obvious singularity in modern conceptions of the cosmos. Is it a goal of modern theories to find a way to remove the big bang singularity from theory, and how is that accomplished in theories be... | g8900 | [
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<p>In a semiconductor diode. There is a depletion region formed, it is formed when electrons from n type side migrate to p type side, now which electrons transfer? Valence band ones present at the boundary or the conduction band ones? If the conduction band ones only migrate, then are there enough present on the bound... | g8901 | [
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<p>When beginning my education, I regarded nearly everything as continuous and analog in nature: </p>
<ul>
<li>Physical objects could have any mass on a continuous scale</li>
<li>Light sources could emit any intensity of light on a continuous scale</li>
</ul>
<p>The more I learn, the more I find what I regarded as co... | g114 | [
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<p>The Feynman-Kikuchi Partition function is given as</p>
<p>$$Z_{FK}=K_\beta \int dx \eta(x) \exp \left(-\frac{x}{\beta}\right) $$</p>
<p>where $K_\beta$ is a normalization constant and </p>
<p>$$\eta(x)=\frac{1}{N!}\sum_P \delta\left(x-(R_0-PR_0)^2/4\lambda^* \right)$$</p>
<p>where $R_0$ is a set of particle coo... | g8902 | [
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<p>The planck length is defined as $l_P = \sqrt{\frac{\hbar G}{c^3}}$. So it is a combination of the constants $c, h, G$ which I believe are all Lorentz invariants. So I think the Planck length should also be a Lorentz invariant!
But there seem to be some confusion about that, see e.g. the following paper
<a href="htt... | g8903 | [
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<p>Can two electrons be in the <em>same state,</em> when they belong to two different atoms, which are "far enough" (whatever that means) apart from each other?
With "same state" I mean that (as far as specifiable) the states are really identical, except for the position of the electrons.</p>
<p>More specifically:<br... | g8904 | [
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<p>Let's imagine a molecule and put it in a 3D space. Let's also imagine an electronic transition for this molecule.
I know how an electronic transition works, how to value if it is possible (using the rules derived from the symmetry of the molecule and so on). My question is: how do I understand how the electron moves... | g8905 | [
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<p>I was studying <a href="http://en.wikipedia.org/wiki/Black-body_radiation" rel="nofollow">black body radiation</a> and how quantization of energy solves the problem of ultraviolet catastrophe. But I have a very fundamental doubt. A black body can be assumed as a cavity with a small hole with radiation leaking out of... | g8906 | [
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<p>Can any red coloured transparent paper be used as an optical filter that only allows red colours through it?</p> | g8907 | [
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<p>Consider a relativistic train of weight $W_t$ in its rest frame.
Force transformation equations say that in the planet's frame its weight is reduced to $W_p=\frac{W}{\gamma}$.</p>
<p>My question is: what is the reaction force experienced by the ground?
We cannot say that in every frame the reaction force is equal t... | g8908 | [
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<p>In the physics tutorial topic on current electricty it defines the positive terminal as the high potential terminal and the negative as the low potential. When talking about positive test charges this analogy makes sense, the charge moves from the +ve to the -ve where it loses potential till it has to be "topped" up... | g8909 | [
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<p>In the Zeeman effect, when we observe along the $B$ field, the polarization of light should be circular polarized. It can be understood by the conservation of angular momentum. $\Delta m=0$ can not be observed and $\Delta m=\pm1$ can be observed and thus circular polarization. </p>
<p>However, I can't understand wh... | g8910 | [
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<p>I'm making a little UV exposure box and I'm looking for a way to evenly spread out the UV light.</p>
<p>I've used Fresnel lenses to do just this in the past, but that was for visible light. But from what I've read, not all things work at all wavelengths and some materials will block UV.</p>
<p>So my first question... | g8911 | [
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<p>I just read about how LCD displays were based only on black&white contrasts, and only colour filters on each subpixel generated the colour of a pixel. However, how does that happen for a <a href="http://en.wikipedia.org/wiki/Cathode_ray_tube" rel="nofollow">CRT</a>? </p>
<p>Is it the same process? If not, durin... | g8912 | [
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<p><img src="http://i.stack.imgur.com/fqcvC.png" alt="enter image description here"></p>
<p>Hi, I was just reviewing some slides from my thermodynamics class, and in one of the slides the professor asks what is the "physical meaning of the slopes" of the isobaric line in a T-v diagram. Can anyone help me understand t... | g8913 | [
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<p>Firstly, most definitions of angular momentum assume a point about which you define angular momentum. I realize that you can consider the angular momentum about any point, and have many angular momentums, and that if they are all useful and all conserved then maybe it doesn't matter if there are lots of different on... | g8914 | [
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<p>I was pondering this question after I read this review:</p>
<blockquote>
<p>M. Zahid Hasan and Charles L. Kane. “<a href="http://dx.doi.org/10.1103/RevModPhys.82.3045" rel="nofollow">Colloquium: topological insulators</a>.” <em>Reviews of Modern Physics</em> <strong>82</strong>, no. 4 (2010): 3045. (<a href="http... | g8915 | [
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<p><strong>Context</strong>: The question refers to computational physics of non linear systems with <em>Mathematica</em>.</p>
<p><strong>Excercise</strong>:
Given the system $\{f_1: \dot{x} = a x + y + x^3, f_2: \dot{y} = x - y \}$:</p>
<ol>
<li>Find the equilibrium points and classify them.</li>
<li>What kind of bi... | g8916 | [
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0.04623635485768318,
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0.026313623413443565,
0.04232271760702133,
0.0... |
<p>Assume you're talking to someone ignorant of the basic facts of astronomy. </p>
<p>How would you prove to them that the Earth orbits the Sun? Similarly, how would you prove to them that the Moon orbits the Earth?</p> | g8917 | [
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0.02214... |
<p>In other words, could there be higher dimensional entanglements between entanglements? For instance, this could allow us to entangle two entangled-far-away pairs to create a system of four entangled particles.</p>
<p>I am sorry if this sounds like a silly question.</p> | g8918 | [
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<p>In a paramagnetic system, where $N = N_\uparrow + N_\downarrow$ is fixed, how does one calculate the average number of spin-up particles $\langle N_\uparrow \rangle$?</p>
<p>You can assume we have the canonical partition function. The Hamiltonian for this system is:</p>
<p>$$ H = \sum_{i=1}^N {\frac{(p_i - b s_i)^... | g8919 | [
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<p>A <a href="http://www.cencophysics.com/planar-diode/p/IG0044534/" rel="nofollow">planar diode</a> in a vacuum bulb can support current in only one direction. To even get current flowing, you have to heat up the cathode filament to excite the electrons. However, once current is flowing, there is a certain limit impos... | g8920 | [
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0.0158... |
<p>What are the typical power densities in conventional boiling water nuclear reactor per cubic centimeter of fission material?</p> | g8921 | [
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... |
<p>Consider the gauge covariant derivative defined by
$$
D_z = d_z + \Delta_z
$$
or explicitly
$$
(D_z)^a{}_c = \delta^a_c d_z + (\Delta_z)^a{}_c = \delta^a_c d_z + f_{bc}{}^a A_z^b
$$
Here, $d_z$ is the covariant derivative w.r.t. to the metric
$$
ds^2 = \gamma_{z{\bar z}} \left( dz \otimes d{\bar z} + d {\bar z} \oti... | g8922 | [
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0.03438528999686241,
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-0.0210... |
<p>So, I have been having a hard time understanding why there is even a complex phase for EM waves:</p>
<p>$$\phi=\exp[i\omega t]=\cos(\omega t)+i\sin(\omega t)$$</p>
<p>Don't understand why it is there? Any one have an explanation?</p> | g295 | [
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-0.... |
<p><a href="http://proj-cngs.web.cern.ch/proj-cngs/Download/CNGSDGVE/cngsdgve.pdf" rel="nofollow">http://proj-cngs.web.cern.ch/proj-cngs/Download/CNGSDGVE/cngsdgve.pdf</a></p>
<p>on page 13 I read that "the present plan is to provide nu_mu neutrinos with an energy between 5 and 30 GeV."</p>
<p>Wikipedia neutrino arti... | g8923 | [
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0.014432508... |
<p>For some reason this question is giving me a hard time :(</p>
<p>The vector $r$ points from $P'(x',y',z')$ to $P(x,y,z)$.</p>
<p>(a) Show that if $P$ is fixed and $P'$ is allowed to move, then $\nabla'(\frac{1}{r})=\frac{\hat{r}}{r^2}$ </p>
<p>(b) (a) Show that if $P'$ is fixed and $P$ is allowed to move, then $\... | g8924 | [
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0.003886826802045107,
0.0460... |
<p>I am looking at a 2D harmonic oscillator
$$H=\frac{1}{2m}(p_x^2+p_y^2)+\frac 12m(\omega_x^2x^2+\omega_y^2y^2)$$
Where $\omega_x=5\omega_y$. I am told that the oscillator is prepared in a coherent state with the following qualities:
$$\langle x(0)\rangle=x_0$$
$$\langle p_x(0)\rangle=0$$
$$\langle y(0)\rangle=0$$
$$... | g8925 | [
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0.... |
<p>With respect to special relativity, I was wondering how the spatial dimensions would differ between the rest and LAB frame of an electron beam.</p>
<p>System: Electron bunch/beam traveling in linear motion. How large/long would the bunch appear in the point of view of an electron (rest frame). How large/long would ... | g8926 | [
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<p>First of all many here will might say that it is Chemistry question.If you think so then read <a href="http://web2.physics.miami.edu/~zuo/class/spr_14/Chemical%20potential.pdf" rel="nofollow">this article</a> and then answer question.</p>
<p>Question is --- We know chemical potential is defined as $\mu_i =\mu_i^{st... | g8927 | [
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0.008754890412092209,
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0.0... |
<p>In relativity, the symmetric energy-momentum tensor is given by
$$
T^{ij},
$$
where $T^{00}$ is the energy density and $\frac{1}{c}T^{10}$ is the momentum density. Thus:
$$ \left(\frac{1}{c}T^{00}dV, \frac{1}{c}T^{10}dV\right)^{T}$$
is the 4-momentum.
Under a Lorentz transformation, this should transform like 4-ve... | g8928 | [
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0.01819131150841713,
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0.011268542148172855,
-0.017... |
<p>I'm working on a problem in which a star of mass M1, radius R1 is surrounded by a thin shell of mass M2, , radius R2. I want to find the solutions to the gravitational potential h in the region in between the star and the shell and region outside both. </p>
<p>Can we assume the mass is stationary, and not too large... | g8929 | [
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0.0026855794712901115,
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0.02044271118938923,
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0.004651878494769335,
0.025286726653575897,
0.... |
<p>This is a quite simple question: quarks do mix (through the CKM matrix), neutrinos do mix (through the PMNS matrix).</p>
<p>Then <strong>why do charged leptons not mix?</strong></p> | g8930 | [
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<p>Can anyone provide me with a rigorous mathematical definition of the <a href="http://en.wikipedia.org/wiki/Standard_Model" rel="nofollow">fundamental particles</a> (all fundamental bosons and fermions), reflecting the analogy of action of groups with interaction of particles, isospin and mediating forces? An answer ... | g8931 | [
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0... |
<p>Precision is usually understood as the number or significant figures in some experiment.
Accuracy is the difference between the best measurement and the real value. </p>
<p>How are <a href="http://en.wikipedia.org/wiki/Accuracy_and_precision" rel="nofollow">precision and accuracy</a> determined from a given experi... | g8932 | [
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0.06577935069799423,
-... |
<p>There are two Casimirs of the Poincare group:</p>
<p>$$ C_1 = P^\mu P_\mu, \quad C_2 = W^\mu W_\mu $$</p>
<p>with the Pauli-Lubanski vector $W_\mu$. This implies the Poincare group has rank 2. </p>
<p>Is there a way to show that there really are no other Casimir operators other than trying to build all possible c... | g8933 | [
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... |
<p>Consider an ideal steam turbine.</p>
<p>The power generated by a steam turbine comes down to the torque and the angular velocity, which is ultimately dependent on the velocity at which the flow enters the turbine (and turbine factors, but will only consider the flow properties). Similarly, the power needed by a tur... | g8934 | [
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0.0... |
<p>I the following (american) test</p>
<blockquote>
<p>Vacuum testing consists of placing samples from the packiging operation into a jar filled with water. A lid is placed over the samples to fully immerse them in the water. A container lid is applied to create a seal effective enough to create approximately <stron... | g8935 | [
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0.04004979506134987,
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-0.04332339018583298,
0.03041074238717556,
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-0... |
<p>If photon is an elementary particle, how can different photons have different energy, if <a href="http://en.wikipedia.org/wiki/Mass%E2%80%93energy_equivalence" rel="nofollow">$E=mc^2$</a> and all photons have (or don't have) the same mass and the speed of photon is constant shouldn't it mean all photons have the sam... | g8936 | [
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0.012378288432955742,
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0.0... |
<p>While reading the amazing things that the <a href="http://en.wikipedia.org/wiki/Mantis_shrimp" rel="nofollow">mantis shrimp</a> can do, such as moving two of their limbs so quickly that the water around them <a href="http://en.wikipedia.org/wiki/Supercavitation" rel="nofollow">'supercavitates'</a>, a friend of mine ... | g8937 | [
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0.002704676240682602,
0.0326029509305954,
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0.030485084280371666,
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0.005655947141349316,
0.04207896441221237,
0.046215... |
<p>The baryon number B or lepton number L violation in the standard model arise from triangle anomaly. Right? Triangle diagrams are perturbative diagrams. Then why the B or L violation in Standard model is said to be a non-perturbative effect? I'm confused.</p> | g8938 | [
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0.017939986661076546,
0.05115956813097,
0.001623351126909256,
0.014743... |
<p>For example in the models for holographic superconductors we can calculate the conductivity. Also there is an energy gap. I can understand that it describes a superconductor. However I have also heard people talk about superfluidity in holographic QCD. I believe they are talking about the condensates such as the pio... | g8939 | [
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0.03426821902394295,
-0.0024223634973168373,
-0.00047083647223189473,... |
<p>What is the correct definition of the energy of a string ?</p>
<p>I suddenly get confused with the definition of the energy of a string. Considering, for instance, a bosonic open string in the light-cone gauge, We have $H = p^-=p_+$, the hamiltonian, and we have $p^0$, which appears in the expansion of the string... | g8940 | [
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0.021546505391597748,
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0.007431569043546915,
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0.006655569188296795,
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-0.0... |
<p>When looking at a Schwarzschild black hole, for instance, we know that we may apply <a href="http://en.wikipedia.org/wiki/Black_hole_thermodynamics" rel="nofollow">black hole thermodynamics</a>. We may define a entropy of the black hole which scales like the area of the horizon : $$S \sim R_s^2$$. </p>
<p>It is und... | g8941 | [
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0.0039285654202103615,
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0.025291454046964645,
0.026328343898057938,
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-0.031276654452085495,
-... |
<p>So I was introduced to this "perpetual motion" riddle a few weeks ago. The problem goes like this: we all know perpetual motion machines are not possible, but this riddle <em>seems</em> like it should work as a perpetual motion machine - the problem is to explain <em>why it doesn't work</em>.</p>
<p><strong>Here's ... | g8942 | [
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0.08928775787353516,
0.00020735115685965866,
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-0.054793909192085266,
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-0.004617132246494293,
0.0034230409655719995,
... |
<p>In a newtonian universe, one can talk of a "time slice", that is, the state of the universe at a given point in (global) time. In a "typical" classical universe, a time slice would contain enough information to fully compute the state of the universe at any other point in time, backwards or forwards.</p>
<p>So, dis... | g8943 | [
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0.03679417818784714,
0.07163480669260025,
0.012192944064736366,
-0.039767876267433167,
... |
<p>A few years ago, when i studied the casimir effect interpretation as the filtering out of vacuum modes with appropiate boundary conditions, i had the following dilemma; supposedly the derivation of the force between the walls was <strong>entirely</strong> equivalent to just calculating Van der Waals forces. This, as... | g8944 | [
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0.044118478894233704,
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0.... |
<p>I've variously heard the shape of the universe being described as multi-dimensional, like a helix or mobius strip, and super string theorem seems to say there are lots of universes all piled up next to each other in vibrating planes.</p>
<p>My question is, can the edges of our universe ever join up? Are they alread... | g8945 | [
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0.041405268013477325,
0.01... |
<p>I've been reading <a href="http://en.wikipedia.org/wiki/Electrolysis_of_water" rel="nofollow">http://en.wikipedia.org/wiki/Electrolysis_of_water</a> and other related questions on physics.stackexchange, but I fear I don't have a decent enough understanding of math and science to understand and decipher into laymen t... | g8946 | [
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<p>What prevents a static black hole from accumulating more charge than its maximum? Is it just simple Coulomb repulsion?</p>
<p>Is the answer the same for rotating black holes?</p>
<h3>Edit</h3>
<p>What I understand from the answers given so far, is that <strong>maximum charge</strong> is a <strong>moving target</s... | g8947 | [
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<p>I am reading an optics book (<em>Physics of Light and Optics</em> by Peatross and Ware) that asserts this:</p>
<blockquote>
<p>A beam of light can always be considered as an intensity sum
of completely unpolarized light and perfectly polarized light:</p>
<p>$$I=I_{Pol}+I_{Un}$$</p>
</blockquote>
<p>How do... | g8948 | [
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<p>If a neutrino has mass then it travels less than the speed of light. Suppose I boost myself to the rest frame; i.e. bring it to rest in the laboratory. Now if it oscillates between different states and masses sitting there, where does the oscillating excess/loss energy and mass reside? In some internal state? I ... | g8949 | [
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... |
<p><img src="http://i.stack.imgur.com/7GRZp.png" alt="enter image description here"></p>
<p>Is the nyquist plot of the open control loop. The starting point (not shown in the figure) is in the negative infinity of the imaginary axis.</p>
<p>What is the order of the process ?</p>
<p>What is the maximum gain of the co... | g8950 | [
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<p>In differential geometry, the differential forms are anti-symmetric tensors. </p>
<p>So, why is the anti-symmetric tensor like
$ d x_1 \otimes dx_2 - d x_2 \otimes d x_1 $, more important than the symmetric tensor like $ d x_1 \otimes dx_2 + d x_2 \otimes d x_1 $ for the theory?</p>
<p>Why do we need anti-symmetr... | g8951 | [
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<p>The density matrix $\hat{\rho}$ is often introduced in textbooks as a mathematical convenience that allows us to describe quantum systems in which there is some level of missing information.</p>
<p>$\hat{\rho} = \sum_{i=1}^N c_i \rvert\psi_i\rangle \langle \psi_i \rvert$</p>
<p>I have two questions regarding densi... | g8952 | [
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<p>In a couple weeks, I will conduct a lab experiment where I measure the lifetime of the muons from the secondary cosmic radiation. For that, we have two detectors above each other, one will give a start signal, the other will give a stop signal, assuming the muon came to rest in the second detector and decayed.</p>
... | g8953 | [
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<p>Suppose that a someone decided to calculate, for a given amount of heat added into a planet's atmosphere(<strong>an ideal gas</strong>), how much is the corresponding temperature rising of the atmosphere, $\Delta T$. Assuming that the whole heat transforms into the internal energy of the gas and distributes uniforml... | g8954 | [
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<p>Why does a quantum field theory invariant under dilations almost always also have to be invariant under proper conformal transformations? To show your favorite dilatation invariant theory is also invariant under proper conformal transformations is seldom straightforward. Integration by parts, introducing Weyl connec... | g385 | [
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<p>I'm looking for something to supplement my Physics II class. Last year I started using <a href="http://www.teach12.com/tgc/courses/course_detail.aspx?cid=1007" rel="nofollow">these video lectures</a> to supplement my Calculus class and it helped tremendously.</p>
<p>I also turned to <a href="http://www.thinkwell.co... | g8955 | [
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... |
<p>I stumbled onto this page</p>
<p><a href="http://mylifeisaverage.com/story/1364811/" rel="nofollow">http://mylifeisaverage.com/story/1364811/</a></p>
<p>and the post states that they were</p>
<blockquote>
<p>all making strings and shapes with
these sets of 216 really small
spherical earth magnets. What did ... | g8956 | [
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<p>Let's have a definition of massive particle as an irreucible representation of the Poincare group. Then, let's have a spinor field $\psi_{\alpha \alpha_{1}...\alpha_{n - 1}\dot {\beta} \dot {\beta}_{1}...\dot {\beta}_{m - 1}}$, which is equal to $\left( \frac{m}{2}, \frac{n}{2}\right)$ representation of the Lorentz ... | g8957 | [
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<p>How can we force a particle (let's say that we know this particle has spin up) to be in a superposition of spin up and down?</p>
<p>Wouldn't literally any interaction of it with anything cause it to be in superposition, since we can never know the exact position/speed of the thing it is interacting with, so surely ... | g8958 | [
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<p>The other day in class the professor was explaining non-inertial reference frames. We were working out how to find the acceleration of a point as measured from the non-inertial reference frame, and one problem was finding the time derivatives of the unit vectors as measured from the non-inertial reference frame.</p>... | g8959 | [
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<p>Person A is on Earth and a train (or whatever you want to imagine) travels past him at near the speed of light. How would person A perceive movement on the ship? If time is slowed on the ship from the perspective of Person A, then if Person B were washing the windows or something (moving his hands up and down), woul... | g8960 | [
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<p>Permutation for classical particle
$$\Omega=\frac{N!}{\Pi n_i!}$$
By using Lagrange method of undetermined multiplier, we get
$$n_i=Ae^{\frac{-E}{kT}}$$
Probability, $$p=\frac{n_i} {Z}$$
where we define $Z$ as
$$Z_{classical}≡∑e^{\frac{-E}{kT}}$$</p>
<p>But for fermion, $$n_i=(Ae^{\frac{E}{kT}}+1)^{-1}$$
My questio... | g8961 | [
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... |
<p>I heard that neon signs contain plasma, why aren't they hot?
is it because the electrons and ions do not hit the lamp's wall?
Is it because it is non thermal plasma and electrons and ions are not in thermal equilibrium?
If that is the case do the electrons and ions and neutral atoms (all of them) hit the lamps wall... | g8962 | [
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<p>I have a very simple question. In our project we store an object's orientation as a 3x3 matrix which holds the orthonormal base of that object's local space. For instance if the object is aligned with the axis of the world, then its orientation matrix is :</p>
<pre><code>1 0 0
0 1 0
0 0 1
</code></pre>
<p>Now we s... | g8963 | [
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<p>I read that all bosons contribute to the casimir effect with an attractive force.</p>
<p><a href="http://math.ucr.edu/home/baez/physics/Quantum/casimir.html" rel="nofollow">http://math.ucr.edu/home/baez/physics/Quantum/casimir.html</a></p>
<p>Does the Higgs boson contribute to the Casimir effect? Could it be the m... | g8964 | [
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<p>A commercial airplane travels at a speed which is 85% of the speed of sound. The wings of the
airplane are designed such that the bottoms of the wings are flat and the tops of the wings are
curved so that air travelling above the wings follows a path which is 15% longer than the straight
path of the air below the... | g8965 | [
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<p>I thought for a long time that the Boltzmann formula for entropy, $S = k_B \ln W$, was a universally true statement, or rather <em>the</em> definition of entropy from the perspective of statistical mechanics. However, I have since come to understand that it is only applicable for an isolated system (i.e. the microca... | g8966 | [
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<p>I have recently read an article about <a href="http://en.wikipedia.org/wiki/Gravity_assist" rel="nofollow">gravitation slingshot assist</a> used by <a href="http://blogs.discovermagazine.com/sciencenotfiction/2010/06/22/traversing-the-cosmos-with-a-little-help-from-my-friends-pt-ii/#.U9VLXvldUX8" rel="nofollow">Voya... | g8967 | [
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0.046338... |
<p>I heard some theory, such as technicolor, predicts the Higgs-like particle discovered at LHC should be a composite particle (correct me if I am wrong). Has this possible been completely excluded already?</p> | g8968 | [
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<p>In episode 7 season 5 of Through the Wormhole, they say that gravity could just be a manifestation of the strong nuclear force and that the force carrier are a pair of Gluons. Is this valid in anyway? </p> | g296 | [
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<p>Lets say you build a steam boiler and then you connect several turbines to the boiler in series. What limits the number of turbines that you can connect to the boiler in this way? In my mind, it seems that the steam still has to escape, so no matter how many turbines are in the way, the steam will still turn all o... | g8969 | [
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<p>Lets say that we made a glove, shirt, pants and a hat out of the most effective thermocouple material available today. How much electricity would be generated by each, by a healthy person, on a cool day (98 degrees F vrs 79 degrees F?)</p> | g8970 | [
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<p>How do magnets work on the atomic level? Is there current inside the magnet?</p> | g297 | [
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-... |
<p>If electrons form a crystal in the Wigner crystal what is the structure of that crystal? cubic, bcc, fcc,...?</p> | g8971 | [
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<p>I try to understand two principles formulated by Leonard Susskind in his book <em>The Black Hole War</em>:</p>
<p>1, To any observer who remains outside a black hole, the stretched horizon appears to be a hot layer of horizon-atoms that absorb, scramble, and eventually emit (in the form of Hawking radiation) every ... | g8972 | [
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0.... |
<p>I was watching a Scott Manley video on youtube and he mentioned that the Sun was loosing 4 million tons of mass a second as it converts to energy. </p>
<p>With a few trillion trillion stars also converting mass to energy, I wonder if that would be a component to the missing "dark matter" mass?</p>
<p>I'm a complet... | g8973 | [
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<p>I would like to know why two forces (of different magnitudes but same direction) that we'd use sequentially on an object to move it by the same amount twice, will produce two different values for the work quantity. </p>
<p>Why is there a mismatch between the maths and the observed physical change?</p>
<p>What exac... | g8974 | [
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<p>The quark mass term in the Standard Model Lagrangian looks like this:</p>
<p>$$ L = - \lambda_d \bar{Q}\phi d_R - \lambda_u \bar{Q} i \tau_2 \phi^* u_R $$</p>
<p>What is the reason for the $ i \tau_2 $ - factor? What keeps me from writing undesirable things like $$\lambda_u \bar{Q} \phi u_R $$ ?</p> | g8975 | [
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<p>Mass and spin of the particle are used in classification of elementary particles. The mass is defined to be a Lorentz invariant quantity. On the other hand, the spin is a spacelike 4-vector and cannot be defined as an invariant quantity.</p>
<p>My question is, what would be a convenient definition of a relativistic... | g8976 | [
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... |
<p>Two resistors are joined as shown. The top resistor receives a current of 3 A. What is the current in the other resistor? What is the current that enters at junction A? I'm confused on how the two currents are 3A and 1A because I thought in a series circuit all the currents are the same. Why is the answer to the cur... | g8977 | [
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<p>Also, is it possible to have electronic displays on the walls of a home? Is there anything in physics that prevents that?
I guess I'm trying to ask if something like this is possible:
<a href="http://www.techcrates.com/transparent-smartphones-our-new-reality/" rel="nofollow">http://www.techcrates.com/transparent-sm... | g8978 | [
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<p>Since synchrotron radiation is created when charged particles are radially accelerated and electrons are definitely orbiting a nucleus (assuming a Bohr model), electron should then logically emit synchrotron radiation. However, if it does, then it lose energy and would unfortunately spiral into the nucleus, which we... | g8979 | [
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<p>I remember reading in an introductory text to phase transition (sorry I don't remember the name) that at a second order phase transition the specific heat and the magnetic susceptibility become infinite and that this implies fluctuations on all length scales.</p>
<p>I understand how this implies strong fluctuations... | g8980 | [
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