question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
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<p>Starting with Euclidean space, suppose I make a number of copies of a coordinate system all coincident at the origin, together with copies of a standard unit length.</p>
<p>For any space interval common to all the coordinate systems, all the observers will count the same minimum number of times their unit length ca... | g6843 | [
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<p>(c.f Di Francesco, Conformal Field Theory chapters 2 and 4).</p>
<p>The expression for the full generator, $G_a$, of a transformation is $$iG_a \Phi = \frac{\delta x^{\mu}}{\delta \omega_{a}} \partial_{\mu} \Phi - \frac{\delta F}{\delta \omega_a}$$
For an infinitesimal special conformal transformation (SCT), the co... | g6844 | [
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<p>Has subatomic particles ever been seen in a state of superposition or do we just detect information like qubits about the state of the particle? So is actual matter in superposition or is it just information about matter that's in a state of superposition?</p> | g6845 | [
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<p>I have a homework problem:</p>
<blockquote>
<p>The Sun emits $ \sim5 x 10^{23}$ photons per second with $hν > 13.6$
$eV$. If the density of hydrogen atoms in interplanetary space is $n =$
$109 m^{-3}$, what is the size of the <a href="http://en.wikipedia.org/wiki/Str%C3%B6mgren_sphere" rel="nofollow">Str... | g6846 | [
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<p>In the Weyl basis we can separate the spinor field into 2 components: the right-chiral spinor and the left-chiral spinor. Each of these fields has again 2 components which are coupled. What is the physical interpretation of these 2 components that make up the left-chiral (or right-chiral) field?</p>
<p>In the Dirac... | g6847 | [
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<p>If an ferromagnetic object is heated and reaches Tc the magnetization gradually drops as we get closer to Tc or it's a instant drop?
Can I assume as I heat the object, the magnetization is weakening gradually? Likewas as it cools?</p> | g6848 | [
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<p>I am trying to model a pressure sensor in COMSOL. The basic work is that there is current flowing inside it, if the pressure of the gas around it drops down, the temperature goes down as well (ideal gas law) , hence there is a variation in the conductivity (described by the temperature coefficient of resistivity) so... | g6849 | [
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<p>Please help. My example:</p>
<p>You take a sheet of steel and suspend it in the air.</p>
<p>Then you take a permanent magnet (i.e. a neodymium magnet) and attach it to the sheet of steel and from that you suspend a 1kg weight. The weight and magnet will stay put providing that the room doesn’t change and that grav... | g6850 | [
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<p>I'm slightly confused with the following situation:</p>
<p>Suppose you have an electron in a tight-binding model, and let's say we are in one dimension with $N$ lattice sites. </p>
<p>Add to this a single impurity at a specific site $i$. </p>
<p>The pure system is translationally invariant and has as eigenfunctio... | g6851 | [
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<p>Arguably the most well-known and used system of units is the SI-system. It assigns seven units to seven ‘fundamental’ quantities (or dimensions). However, there are other possible options, such as Gaussian units or Planck units. Until recently, I thought that these different systems differed only in <em>scale</em>, ... | g6852 | [
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<p>Given for example, Hydrogen electron in ground state. What is probability to find that electron at certain distance (not interval of distances) from center of nucleus, for example at radial coordinate $r=0.5 \cdot 10^{-10}$ (and any angle)? </p> | g6853 | [
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<p>Is possible estimate the needed size of an geodesic dome (like in the Eden project) for creating an real hydrosphere - especially clouds (and rain)?</p>
<p>With other words, under what circumstances can happen clouds formation in an closed space -isolated from the outer atmosphere?</p> | g6854 | [
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<p>The de Donder gauge is often used to simplify the linearised equations of motion of general relativity. If the metric is linearised as $g_{ab} = \bar g_{ab} + \gamma_{ab}$, then the de Donder gauge reads<br>
$\nabla^a(\gamma_{ab} - \frac{1}{2}\bar g_{ab}\gamma) = 0$.</p>
<p>The partial differential equation for the... | g6855 | [
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<p>Obviously electrons annihilate with positrons, but can a muon annihilate with an positron, or can an anti-taon cancel with a muon? similarly for quarks of different species, e.g. u and anti-strange.</p>
<p>I think this is possible as long as quantum numbers like charge and spin are conserved, with the excess energy... | g6856 | [
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<p>I've been trying to get my head around the formalisms used in the Standard Model. From what i've gathered Dirac Spinors are 4 component objects designed to be operated on by Lorentz Transformations much like 4-Vectors are in Special Relativity. However they also incorporate additional information: Spin and "Handedne... | g6857 | [
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<p>My question is what is the relation between N=2 super Yang-Mills and its twisted version topological field theory? After twisting N=2 super Yang-Mills, i.e. diagonally embedding $SU(2)'_R$ into $SU(2)_R \times SU(2)_I$, we get a topological field theory. My question is since N=2 SYM and TQFT are different i.e. one... | g6858 | [
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<p>I had a question on a dimensional regularization identity. A reference or a quick sort of derivation will be greatly appreciated. I looked at some textbooks of QFT, but couldn't find the one I was looking for.</p>
<p>I found in <a href="http://www.maths.tcd.ie/~cblair/notes/list.pdf" rel="nofollow">http://www.maths... | g6859 | [
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<p>Water (and other substances) can exist in many distinct solid phases (with different crystallic micro-structure), but only in two fluid phases - liquid and gaseous, in which the molecules are oriented randomly (they is no long range order). Is there an explanation in the molecular theory, why there are just two "dis... | g6860 | [
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<p>Let's have generating functional $Z(J)$:
$$
Z(J) = \langle 0|\hat {T}e^{i \int d^{4}x (L_{Int}(\varphi (x)) + J(x) \varphi (x))}|0 \rangle , \qquad (1)
$$
where $J(x)$ is the functional argument (source), $\hat {T}$ is the chronological operator, $\varphi (x)$ - some field. </p>
<p>I want to understand the reasons ... | g6861 | [
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://physics.stackexchange.com/questions/1775/why-is-there-no-absolute-maximum-temperature">Why is there no absolute maximum temperature?</a> </p>
</blockquote>
<p>Is there any upper limit of the temperature that can be achieved? Is the speed o... | g237 | [
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<p>I have recently been looking into the <a href="http://en.wikipedia.org/wiki/Multiple_time_dimensions">two-time theories</a> and the implied concepts.</p>
<p>For me this seems slightly hard to grasp.</p>
<p>How can I see the basic concept in this theory in a fundamental way based on its implied interaction with nor... | g6862 | [
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<p>This may be a stupid question but I am having trouble getting the same result in CGS units as I would if I used SI units for a unitless calculation. </p>
<p>I have to calculate $E_c=\frac{m_e c\, \omega_c}{eB}$ I have in CGS units that $\frac{e}{m_ec}$ is $(1.76\times10^{7}s^{-1}G^{-1})$ and $B=10^{-4}G=10^{-8}T$ a... | g6863 | [
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<p>This posting is directly related to the issue in <a href="http://physics.stackexchange.com/questions/32385/the-system-and-the-measuring-gadget">The System and the Measuring Gadget</a>.</p>
<p>The QM expectation is given by:</p>
<p>$$\langle\sigma_{1}.\vec{a}{\;}\sigma_{2}.\vec b\rangle=-\vec a.\vec b$$</p>
<p>In ... | g6864 | [
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<p>I've already searched Physics StackExchange for some similar question but I didn't find anything about this.</p>
<p>Assumptions:</p>
<ul>
<li>Earth is a perfect sphere with it's core (X,Y,Z) -> (0,0,0) as a reference-frame center</li>
<li>Air resistance can be ignored</li>
<li>Earth rotation can be ignored</li>
<l... | g6865 | [
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<p>Perhaps an elementary questions. Given a time limited measurement situation, would it be better for one to measure more averages or more data points?</p>
<p>More averages will increase the SNR by $$\sqrt{n}$$ , i.e., making the data point more reliable, but more data points may make the fitting better. </p>
<p>Con... | g6866 | [
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<p>What is the capture cross-section of a black hole region for ultra-relativistic particles? I have read that it is </p>
<p>$$\sigma ~=~ \frac{27}{4}\pi R^{2}_{s}$$ </p>
<p>for a Schwarzschild BH in the geometric optics limit. Where does the coefficient come from?</p>
<p>Edit - Sources:</p>
<ol>
<li><a href="http:... | g6867 | [
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<p>At the introduction to quantum mechanic <a href="http://en.wikipedia.org/wiki/Phase_velocity" rel="nofollow">phase</a> $v_p$ and <a href="http://en.wikipedia.org/wiki/Group_velocity" rel="nofollow">group</a> $v_g$ velocities are often presented. I know how to derive $v_p$ and get equation:</p>
<p>$$
\scriptsize
v_p... | g6868 | [
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<p>Im designing a model for Kelvin Method. Some of my calculation results are as follows: </p>
<ol>
<li>Radius of the membrane : 50 micron </li>
<li>thickness of the membrane : 3.25 micron </li>
<li>resonate frequency : 1.32MHz</li>
<li>spring constant : 1.81*10^4 N/m</li>
<li>mass : 1.045*10^-8 Kg</li>
</ol>
<p><img... | g6869 | [
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<p>A spring is a mechanical flexible element and has to absorb energy from outside gradually. We are manufacturing springs in helical shapes on a large scale. What is the reason behind this?</p> | g238 | [
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<p>What is the difference between implicit and explicit time dependence e.g. $\frac{\partial \rho}{\partial t}$ and $\frac{d \rho} {dt}$?</p>
<p>I know one is a partial derivative and the other is a total derivative. But physically I cannot distinguish between them. I have a clue that my doubt really might be understa... | g362 | [
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<p>You have the following energy maps for 14 different structures so about 4-5 pixels for one unit. The color density represents energy.</p>
<p><img src="http://i.stack.imgur.com/4VNj3.png" alt="enter image description here"></p>
<p>I am thinking that you can set multivariate time series models from energy maps by <c... | g6870 | [
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<p>Let's say the objects are marble size or even single atoms or quarks. They are placed in an otherwise empty universe(expanding or non-expanding) at opposite ends of the universe with an arbitrarily large distance between them. With a combination of great enough distance and small enough mass will the gravitational p... | g6871 | [
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<p>There are many applications for orbital space mirrors in astronomy (better telescopes) and space propulsion (solar power for deep space probes), but this is limited by the minimum beam divergence achievable with current technology</p>
<p>So, i'm trying to understand what physical and technological limits exists in ... | g6872 | [
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<p>I have a problem in which the tell me that you drop a bag of 50 kg of sand from 10 meters high, and you have to caltulate the entropy difference of the sand, asuming that the speific heat of the sand is so high that its temperature (298K) doesn't change. My result is 16.5 J/K, and my problem is with the sign. The bo... | g6873 | [
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<p>What force do the arms have to generate to do a pushup? Let us look a this simplified model:</p>
<p><img src="http://i.stack.imgur.com/ueWHS.jpg" alt="pushup physics"></p>
<p>The body can be represented by the green plank of mass B. Its angle to the ground is $\theta$. </p>
<p><em>This question was asked on <a hr... | g6874 | [
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<p>Person A in reference frame A watches person B travel from Star 1 to Star 2 (a distance of d). Of course, from person B's reference frame, he is at rest and is watching Star 2 traveling to him. </p>
<p>Now we know from the principle of relativity, each one will measure the other one’s clock as running slower than... | g6875 | [
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<p>Is it possible to predict what the final temperature will be by taking temperature samples. For example, an object is 0ºC and moved to a room above 0ºC. I'm taking temperature of the object using a thermometer every second. Can I predict (approximation) on what the final temperature would be after a few samples? I g... | g6876 | [
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<p>Most derivations I have seen of the Born-Oppenheimer approximation are made using wave-functions. To understand it better, I was trying to write a derivation using Dirac notation, but I am stuck. I am going to post what I have done so far so you guys can help me out.</p>
<p>The hamiltonian of the molecule can be wr... | g6877 | [
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<p>The many-worlds interpretation of quantum physics is built around a configuration space, where the position of a particle is three components of the position of that universe.</p>
<p>What happens with particle-antiparticle creation or annihilation? It can't just change the number of dimensions, can it?</p> | g6878 | [
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<p>According to an answer in <a href="http://skeptics.stackexchange.com/questions/1664/it-is-not-the-voltage-that-kills-you-it-is-the-current/1667#1667">this thread</a> on Skeptics:</p>
<blockquote>
<p>If you take one of the little 12V
garage door opener batteries and short
out (directly connect) the two
termi... | g6879 | [
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<p><strike>Science and science fiction alike</strike>Science fiction describes black holes as these amazingly different entities in space that don't behave according to the same laws of physics that the rest of the universe is bound to. I've heard them described as wormholes to other universes, singularities, or tears ... | g6880 | [
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<p>I know that there are a lot theses being published on lives of physicists. Is there a history/non-fiction book that tracks the development of a problem chronologically? Like pieces of a puzzle.
I would like it to be mathematical and trying to get into the heads of people trying to solve that problem.</p>
<p>Someth... | g6881 | [
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<p>I understand that in nature wind would never get high enough, but I am just curious as to whether physics would allow this to occur or not.</p> | g6882 | [
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<p>What are the conditions in order for the equations: <a href="http://en.wikipedia.org/wiki/Entropy" rel="nofollow">Entropy</a> $dQ = TdS$ and <a href="http://en.wikipedia.org/wiki/Work_%28thermodynamics%29" rel="nofollow">Work</a> $dW = -p dV$ to work?</p>
<p>I think for $dQ = T dS$, it must be a reversible process... | g6883 | [
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<p>I am not sure in which SE site I have to put this question. But since I have learnt Shannon Entropy in the context of Statistical Physics, I am putting this question here.</p>
<p>In the case of Shannon Information theory, he defines information $I$ for an $i^{th}$ event as,</p>
<p>$$ I_i = -\ln P_i \qquad \qquad ... | g6884 | [
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<p>I am looking for a site that publishing riddles and problems such as <a href="https://projecteuler.net/">Project Euler</a>
publishes problems in computer science. Is there any similar site that is hardcore in the area of physics? </p>
<p><a href="http://www.feynmanlectures.info/">This site</a> has some good proble... | g6885 | [
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<p>Any entangled state represents a quantum possibility that is classically impossible.<br>
Is the converse true?<br>
That is, are all states that are quantum mechanically possible but classically impossible entangled in some way?<br>
If so, can you give a proof, or a reference to a proof?<br>
If not, can you give a co... | g6886 | [
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<p>I'm looking at <a href="http://www.math.ias.edu/QFT/fall/faddeev4.ps" rel="nofollow">this reference</a> (sorry it's a postscript file, but I can't find a pdf version on the web. <a href="http://www.srv2.fis.puc.cl/~mbanados/Cursos/TopicosRelatividadAvanzada/FaddeevJackiw.pdf" rel="nofollow">This paper</a> describes... | g6887 | [
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<p>With all the hype of the impending "2012 Mayan doomsday" I was thinking it might be interesting to see what principles of physics prevent the theories of doomsday from occurring. One overarching theory is that on December 21, 2012, the two magnetic poles will reverse as a result of a solar flare equivalent to 100 bi... | g6888 | [
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<p>Find the displacement and velocity of horizontal motion in a medium in which the retarding force is proportional to the velocity.</p>
<p>I kind of understand how to do this problem.</p>
<p>We know that the resistive force $F_r \propto v$. Since $F_r$ is the only force present in the x-direction, Newton's second la... | g6889 | [
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<p>Are all wavelengths absorbed in the semiconductor regardless of material's absorption band? </p> | g6890 | [
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<p>I am stumped by a mundane A Level Physics question (teacher of physics here obviously a bit short of practice!). My colleagues and I are stumped and were wondering if any one could help us.</p>
<p>It concerns the change in KE of a satellite in orbit, if a satellite drops it’s orbit to that of a lower radius, it’s c... | g6891 | [
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... |
<p>I am doing an experiment to show the effect on the velocity of a falling mass due to change in mass. How can i justify my prediction that the velocity of the falling mass will increase as i increase the mass. </p>
<p>For my experiment i am dropping masses between 100-800g threw 1000ml of water and timing how long t... | g6892 | [
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0.00815784651786089,
0.09132... |
<p>$\newcommand{\v}[1]{\vec #1}\newcommand{\i}{\hat i}\newcommand{\j}{\hat j}$
Problem statement <sup>(<a href="http://i.imgur.com/pM6NQNa.jpg" rel="nofollow">1</a>,<a href="http://i.imgur.com/TP36dQo.jpg" rel="nofollow">2</a>)</sup></p>
<blockquote>
<p>A shopper at the supermarket follows the path indicated by vect... | g6893 | [
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0... |
<ol>
<li><p>What would be a good Internet link that would properly explain <a href="http://en.wikipedia.org/wiki/Fermi_energy" rel="nofollow">Fermi Energy</a>? </p></li>
<li><p>How does the Fermi Energy of a material vary with external influence, such as doping of the material, and applied electric and magnetic fields ... | g6894 | [
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0.02637... |
<p>My quantum mechanics textbook says that when a particle (in the classical case) comes across a potential-step barrier of finite height, if it has sufficient energy to surmount the barrier, it will continue on with reduced kinetic energy. </p>
<p>I'm finding this hard to understand since force is given by $$F=-\frac... | g6895 | [
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0.... |
<p>Suppose you have two stationary people, A and B, who are equally effective in terms of hearing ability, and A emits a sound that is heard by B at a certain intensity. If they remain stationary, and B makes the exact same sound, does A hear the sound at the same intensity as B?</p> | g6896 | [
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<p>A lepton is an elementary particle. The best known of all <a href="http://en.wikipedia.org/wiki/Lepton" rel="nofollow">leptons</a> is the electron which governs nearly all of chemistry as it is found in atoms and is directly tied to all chemical properties.</p>
<p>The heavier <a href="http://en.wikipedia.org/wiki/M... | g6897 | [
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-0.01779... |
<p>Recall the normal ordering of bosonic operators in QFT is defined by a re-arrangement of operators to put creation operators to the left of annihilation operators in the product. This is designed to avoid accidentally annihilating $|0\rangle$ when looking at an expectation value in relation to the vacuum state. </p>... | g6898 | [
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<p>Say that we have an irreversible expansion process which extracts energy, like a turbine. Isentropic efficiency is commonly defined by the following relation, which applies in a similar fashion for pumps. Here, state 1 refers to the inlet conditions and state 2 refers to the outlet conditions, while the "s" indicat... | g6899 | [
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<p>Due to differences in air pressure, temperature, and other factors, the speed of sound varies with altitude on Earth. Does this affect the pitch of the sound in any meaningful way?</p>
<p>For example, if I had a tuning fork that vibrates at around 262 Hz, would I hear the same "<a href="https://en.wikipedia.org/wi... | g6900 | [
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-0.01064319... |
<p>Does Kepler's law only apply to planets? If so why doesn't it apply to other objects undergoing circular motion?</p>
<p>By Kepler's law I'm referring to $T^2 \propto r^3$</p> | g6901 | [
0.01373900007456541,
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-0.0265... |
<p><img src="http://img84.imageshack.us/img84/4082/collision.jpg" alt="Branes Collision - Big Bang">
Imagine universe occurred when two parallel branes collided, Momentum of Branes converted to big bang kinetic energy after Collision. Thus, high-energy quanta are high-Vibrating strings.</p>
<blockquote>
<p>what cosm... | g6902 | [
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0.00815870612859726,
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0.014019646681845188,
0.0135... |
<p>If I were to try to find pi using a ruler and a compass, I would first try to find out how many rational line segments of the diameter I could fit around the interior circumference and then continue to refine until I began converging on some number. Before the foundations of Non-Euclidean geometry were made, people... | g6903 | [
0.02520226500928402,
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0.026367181912064552,
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0.06285324692726135,
0.00... |
<p>I have a number of measurements of the same quantity (in this case, the speed of sound in a material). Each of these measurements has their own uncertainty.</p>
<p>$$ v_{1} \pm \Delta v_{1} $$
$$ v_{2} \pm \Delta v_{2} $$
$$ v_{3} \pm \Delta v_{3} $$
$$ \vdots $$
$$ v_{N} \pm \Delta v_{N} $$</p>
<p>Since they're m... | g892 | [
0.016635477542877197,
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0.01332860067486763,
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-0.... |
<p>By 'wrong reference state' I mean a state which cannot be transformed into desired ones via variational ansatz</p>
<p>$\left|\Psi\left[\mathbf{n}\right]\right\rangle =e^{i\hat{O}\left[\mathbf{n}\right]}\left|ref\right\rangle \;,\; H\left[\mathbf{n}\right]=\left\langle \Psi\left[\mathbf{n}\right]\right|\hat{H}\left|... | g6904 | [
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<p>I need to elaborate the equation ,and need to know what is the physical significance and how matrices will manipulate in the equation $$
\hat{H} = (\hat{\tau_3}+i\hat{\tau_2})\frac{\hat{p}^2}{2m_0}+ \hat{\tau_3}m_0 c^2 =
\left| \begin{array}{ccc}
1 & 1 \\
-1 & -1 \\
\end{array}\right| \frac{\hat{p... | g6905 | [
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0.02853180468082428,
0.04... |
<p>Definition clarification needed, please: I am hoping to get physical sense of an "inertial frame".</p>
<p>Do inertial reference frames all have zero curvature for their spacetime?</p>
<p>So is an inertial frame just a flat metric?</p>
<p>(Sorry that the question is not too profound. I have read the Wiki article ... | g6906 | [
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<p>It is said that we can introduce local inertial coordinates for any timelike geodesic. But why only for timelike geodesics? What about null geodesics? Perhaps it has to do with invertibility or something?</p>
<p>Thanks.</p> | g6907 | [
0.07543870061635971,
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0.0... |
<p>What causes lightning to follow the path it does ?</p>
<p><img src="http://i.stack.imgur.com/U7fBT.jpg" alt="loopy lightning"></p>
<p>picture from BBC news: <a href="http://news.bbcimg.co.uk/media/images/62891000/jpg/_62891901_untitled-1copy.jpg" rel="nofollow">http://news.bbcimg.co.uk/media/images/62891000/jpg/_6... | g6908 | [
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0.0070427278988063335,
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<p>I've not come across any expression involving $\langle\Omega|f|\Omega\rangle$ in <a href="http://web.physics.ucsb.edu/~mark/qft.html" rel="nofollow">Srednicki's QFT book</a> (please correct me if these exist there). On the other hand, they are abound in Chapter 7 of Peskin&Schroeder, in relation to the LSZ reduc... | g6909 | [
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0.051141317933797836,
... |
<p>Since it's convex lens there in our eyes so image formed on our retina is inverted, so how come that we see upright images? </p> | g6910 | [
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<p>The scenario that I'm having is such that a ball of radius $15mm$ is thrown from a location point $\vec{p}=(2, 5, 2)$ in a direction of $\vec{d}=(3, 0, 4)$. The initial velocity is $30m/s$. There were wind velocity at $15m/s$ in the direction of $\vec{v}=(0, 1, 0)$. The mass of the ball is $2kg$ and the gravity is $... | g6911 | [
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<p>In the context of classical physics,is there any renormalization method to avoid infinite energy of point charges?</p> | g6912 | [
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<p>How does repulsion and attraction of a magnet work? I have a hypothesis. We all know that repulsion works when people throw balls at each other. This is used as an analogy of how virtual particles are used to explain how magnets repel each other in some cases. The other idea is that virtual particles have momentum ... | g6913 | [
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<p>There's this "atomic" explanation of the freezing-point phenomena on Wikipedia that leaves me really intrigued.</p>
<blockquote>
<p>Consider the problem in which the solvent freezes to a very nearly pure
crystal, regardless of the presence of the solute. This
typically occurs simply because the solute molecul... | g6914 | [
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<p>I believe the title is straightforward. Evaporating water leaves behind chalk. Assuming you evaporate the same amount of (the same type of) water, does the temperature at which this happens (and so also the time it will take) matter for the amount of chalk that is left behind? </p>
<p>Maybe a little side-question: ... | g6915 | [
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0.027799183502793312,
0.0329... |
<p>I have a system with a number of measurables (in time). Some measurables are discrete some are continuous (within the measurement accuracy). How can I determine whether my system experiences criticality or not?</p>
<p>I am looking for many different ways to (dis)proof criticality.</p>
<p>See here for critical phen... | g6916 | [
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... |
<p>Int he three-mass coupled oscillator problem, we often see it stated that you have three masses, (they can be equal or not, but we'll assume they are equal here) connected by two springs and then another set of springs connecting the masses to the walls on the end. We assume that the spring constants are all the sam... | g6917 | [
0.08550931513309479,
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... |
<p>How does one find the time dependent position expectation value for a wave function? I thought we could simple take the time dependent wave and apply the position operator like normal, but this gave me the wrong answer, as the time dependencies multiplied to one and left me with my solution for $t = 0$. </p>
<p>Add... | g6918 | [
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... |
<p>Hey i am by no means a scientist but i have a idea for a art work using smoke.</p>
<p>Basically what i want to know is whether it is possible to circulate smoke by means of a pump through a transparent box. If the box is completely sealed will the smoke disappear within time? When the smoke is pumped out and back i... | g6919 | [
0.01141570508480072,
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0.0333... |
<p>Is there some condition in the N=1 SUSY algebra telling that the spin of the superpartners of gauge bosons (either for colour or for electroweak) must be less than the spin of the gauge boson?
I am particularly puzzled because sometimes a supermultiplet is got from sugra that contains one spin 2 particle, four spin... | g6920 | [
0.006353695411235094,
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0.01737980544567108,
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0.... |
<p>A gluon string is a particular kind of open string terminated in two particles which are the sources for the field. Is it possible to have a similar arrangement with gluinos? At first glance, it seems to me that such object could not exist, or at least not as an extended object: you need bosons to mediate between th... | g6921 | [
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<p>Is it possible to use the data that is readily available (e.g. of the <a href="http://www2.jpl.nasa.gov/srtm/" rel="nofollow">Shuttle Radar Topography Mission</a>) to predict the flooding of a region?</p>
<p>Would it be necessary to use the refined geoid of Gravity Probe B?</p>
<p>Is there free software that can d... | g6922 | [
0.015910308808088303,
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<p>I am trying to teach myself some particle physics. </p>
<p>There are too many particles and its too much for me. </p>
<p>I hated biology just because of this sort of stuff. Too many names and it was all Greek to me. </p>
<p>Is there a good cheat sheet/ reference sheet of elementary particles? </p>
<p>It will als... | g6923 | [
0.05728398263454437,
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0.04529411718249321,
0.051... |
<p>Someone can explain me what's the rule behind the correct expression of a quantity $K$ with its error $\Delta K$ as $K \pm \Delta K$?
They must have the same number of significant figures? Or the error should have in general 1-2 significant figures? For example, if I have:</p>
<p>$$K = 8510.33 \pm 56.97~.$$
This ... | g6924 | [
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0.02568262629210949,
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0... |
<p>Say there is a circuit with two 1.5V cells, and a 100 ohm resistor.</p>
<p>If you connect two cells in series, then the total emf is 3V. And the current will be 3/100 = 0.03 A. (Using V = IR):<br>
<img src="http://i.stack.imgur.com/qQmhp.png" alt="enter image description here"></p>
<p>If you have the cells in para... | g6925 | [
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<p>I am trying to understand <a href="http://en.wikipedia.org/wiki/R%C3%B8mer%27s_determination_of_the_speed_of_light" rel="nofollow">Rømer's determination of the speed of light</a> ($c$). The geometry of the situation is shown in the image below. The determination involves measuring apparent fluctuations in the orbita... | g6926 | [
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<p>Consider fields $\rho \left( \vec{r} \right)$, $\vec{J} \left( \vec{r} \right)$, $\vec{E} \left( \vec{r} \right)$ and $\vec{B} \left( \vec{r} \right)$ in $\mathbb{R}^3$, with their usual meaning as per Electrodynamics. </p>
<p>Take any finite volume $V_s$ outside of which $\vec{J}\left(\vec{r}\right)$ and $\rho\lef... | g6927 | [
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0.015407863073050976,
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0... |
<p>I am watching this <a href="http://upload.wikimedia.org/wikipedia/commons/c/ca/Collision_carts_inelastic.gif" rel="nofollow">example</a> from Wikipedia: </p>
<p><img src="http://upload.wikimedia.org/wikipedia/commons/c/ca/Collision_carts_inelastic.gif" alt=""></p>
<p>I am wondering what factors would indicate that... | g6928 | [
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<p>Is there any tools except helmholtz coil to cancel out earth's magnetic field to calibrate magnetometers in practice.</p> | g6929 | [
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0... |
<p>Can I measure the value of g using only a metre stick and a ball? I am not supposed to use a stopwatch and that has been the problem.
NOTE: I do not know if a solution exists or not.</p> | g6930 | [
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<p>I don't just mean reactions that require heat to proceed, storing surplus energy in chemical bonds. I wonder about strongly endothermic reactions that suck heat out of environment.</p>
<p>You take some substance A (e.g. Ammonium Nitrate), and some substance B (e.g. water), both at room temperature. You mix them tog... | g6931 | [
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<p>I didn't know whether to pose this question on <em>Physics.stackexchange</em> or <em>Math.stackexchange</em>. But since this is the last step of a development involving the eigenfunctions of an Harmonic oscillator and a <em>shift operator matrix</em>, I thought it'd be better to post it here.</p>
<p>I have to calcu... | g6932 | [
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<p>I know it is not safe when viewing a solar eclipse to look directly at the sun. I know you can purchase solar eclipse glasses online but how do you make your own solar eclipse glasses that are safe to use for solar eclipse viewing (and let us throw in the transit of Venus)? </p> | g6933 | [
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<p>Consider spherical symmetric$^1$ masses of radii $R_1$ and $R_2$, with spherical symmetric density distributions $\rho_1(r_1)$ and $\rho_2(r_2)$, and with a distance between the centers of the spheres $d$. What is the exact force between them? I know point masses are a good approximation, but I'm looking for an exac... | g6934 | [
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... |
<p>If the Hubble constant is extremely large, what will happen with quark confinement?</p>
<p>I guess that quarks will remain confined because of asymptotic freedom. But can gravity or dark energy have any effect on asymptotic freedom? Can gravitational collapse, or a huge cosmological constant, rip a proton apart?</p... | g6935 | [
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<p>It was very cold outside, this morning, when I took the car that slept in the snow, with a simple cloth on the windshield. I entered the vehicle, drove a kilometer or so. The air inside was so cold I could see my breath (or maybe I forgot to brush my teeth). Warm air was blowing on the windshield from the inside and... | g6936 | [
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<p>Physicists proposed the idea of multiverses to explain extraordinary fine tuning of the cosmic constant and physical laws which is essential for rise of life on earth.</p>
<blockquote>
<p>Is there any experiment that can test the validity of multiverse hypothesis?</p>
</blockquote> | g6937 | [
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<p>$\int \frac{Q_{rev}}{T} = \Delta(k_B\ln\Omega)=\Delta S$ <BR>
Could anyone give some definite proof for this?</p>
<p>I was able to prove that the two definitions of change in entropy are equivalent for an isothermal process carried out on a gas (by quantizing space and then limiting the quantization to infinity), b... | g6938 | [
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