question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>We know that gravitational waves are emitted (at least in GR) when the system has a time-varying quadrupole (or higher) moment. My question is</p>
<p><em>Is it possible to easily tell (e.g. just by looking) if a system has such moments?</em></p>
<p>Is there some kind of symmetry to look for that lets you know that... | g11940 | [
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<p>For instance evidence that a highly energetic laser beam attracts objects nearby?</p>
<p>In the framework of Einstein's general relativity all energy curves spacetime and hence exerts an attraction, but my question is whether it is an experimentally verified fact that energy that doesn't come from mass (such as pho... | g512 | [
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<p>I would like to know if light is affected by gravity, also, I would like to know what is the correct definition of gravity:</p>
<p>"A force that attracts bodies with mass" or "a force that attracts bodies with energy, such as light"?</p>
<p>Is light massless after all?</p> | g143 | [
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<p>Suppose that a hollow truncated cone is placed in a wind tunnel with a steady wind speed $V$. The cone is placed in such a way that it's base of area $A_1$ faces the wind (rather than the other side of area $A_2$ for which $A_1>A_2$). Here's a contradiction:</p>
<p>Supposing that $V_2$ is the speed for which win... | g11941 | [
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<p>Consider a situation where a wheel is rolling without friction on a level surface. Call the center of the wheel $C$, the point where the wheel contacts the ground $G$, and some arbitrary other point on the rim of the wheel $P$.</p>
<p>The normal force has no torque when $G$ or $C$ is picked as the axis of rotation,... | g11942 | [
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<p>I'm wondering is there any way to decompose the deformation of an object into different components? For example, into stretching, bending and twisting part respectively? The decomposition could be applied to any description of deformation, either to deformation gradient tensor, strain tensor or stress tensor.</p>
<... | g11943 | [
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<p>I was informed that in a circuit, the current will stay the same, and this is why the lightbulbs will light up (because in order for the current to stay the same, the drift speed of the electrons need to get faster). However, I do not understand why the current needs to stay the same from point to point.</p>
<p>Wh... | g11944 | [
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<p>If the universe started from Big Bang and everything is expanding outwards and actually accelerating away from each other, than "<strong>How is it possible for two galaxies to collide as they all are moving in the same direction</strong>". To collide they must in opposite direction!</p>
<p>Edit:<strong>How is it po... | g11945 | [
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<p>I use the sign convention:</p>
<ul>
<li>Heat absorbed by the system = $q+$ (positive)</li>
<li>Heat evolved by the system = $q-$ (negative)</li>
<li>Work done on the system = $w +$ (positive)</li>
<li>Work done by the system = $w -$ (negative)</li>
</ul>
<p>Could anyone please tell me, that volume increased in sys... | g11946 | [
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<p>Ok so I understand the PN junction, and how when 2 Semiconductor materials are placed together the Electrons will jump into the Holes near the junction creating a Negatively Ionized Atoms on the P-Side (Near the Junction) and Positively Charged Atoms near the Junction on the N-Side.</p>
<p>Makes sense.</p>
<p>HOWE... | g11947 | [
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<p>When a sink drains it forms a vortex. Does that vortex speeds drainage. If yes, how does the vortex speed drainage?</p>
<p>The only relevant thing I could find was an <a href="http://www.sciencedirect.com/science/article/pii/S0378437103005946">expensive article</a> and a <a href="http://www.usc.edu/CSSF/History/201... | g11948 | [
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<p>I want to prove the Bethe-Bloch stopping power formula but I don't know where to start. Any one can offer a book or paper?</p>
<p>Related: <a href="http://en.wikipedia.org/wiki/Bethe_formula" rel="nofollow">http://en.wikipedia.org/wiki/Bethe_formula</a></p> | g11949 | [
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<p>I'm currently reading up on quantum computing and it seems like I have found some contradiction about how to represent <a href="http://en.wikipedia.org/wiki/Qubit" rel="nofollow">qubits</a>.</p>
<p>It is often stated that a qubit is represented as $a|0\rangle + b|1\rangle = (a, b)$ with both a and b being complex n... | g11950 | [
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<p>The <a href="http://en.wikipedia.org/wiki/Clebsch%E2%80%93Gordan_coefficients" rel="nofollow">Clebsch-Gordan coefficients</a> can only be non-zero if the triangle inequality holds:
$$\vert j_1-j_2 \vert \le j \le j_1+j_2$$
In my syllabus they give the following proof:
$$-j \le m \le j$$
$$-j_1 \le m_ \le j_1$$
and $... | g11951 | [
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<p>EDIT: I found both answers to my question to be unsatisfactory. But I think this is because the question itself is unsatisfactory, so I reworded it in order to allow a good answer.</p>
<hr>
<p>One take on contextuality is to develop an inequality on measurement outcomes that is satisfied for any ontological noncon... | g11952 | [
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<p>I hope someone can help me find the page or chapter where Helstrom discusses his famous measurement for distinguishing between two mixtures in the textbook <em>Quantum Detection and Estimation Theory</em>.</p>
<p>Thanks in advance.</p> | g11953 | [
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<p>A pneumatic cylinder is kept vertically straight on a weighing scale, which is set at 0 for the setup.</p>
<p>now a force of 1000 N is applied on the cylinder.</p>
<p>what is the reading of scale.</p>
<p>assume the outlet/ inlet to be blocked hence the mass of air inside the cylinder shall remain constant all the... | g11954 | [
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<p>In the first days of July 1997, after a long driving effort, crossing all of Europe to come to a meeting in Peñiscola, Vladimir Gribov fell fatally sick and he passed away one month later. His paper "<em>QCD at large and short distances</em>" was uploaded posthumously to arXiv:hep-ph/9708424 and, in edited version, ... | g11955 | [
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<p>If $|0 \rangle$ is the vacuum state in quantum mechanics and $\alpha$ is any complex number, what is $\langle 0 | \alpha | 0 \rangle$? I need to have that $\langle 0 | \alpha | 0 \rangle = \alpha$, but this seems to imply that $\langle 0 | 0 \rangle = 1$. Is this true? If so, why? </p> | g11956 | [
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<p>I have a doubt about a couple of exercises tha asks to find the work done on introducing a dieletric between the plates of a capacitor. Yes, this question is in the general case, how do we procede? I really don't know how to start those questions. I know how to find the new capacitance, the new field between the pla... | g11957 | [
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<p>I am trying the following problem. A resistor with $295\Omega$ and an inductor are connected in series across an AC source that has voltage amplitude of $550V$. The rate at which electrical energy is dissipated in the resistor is $224W$. </p>
<p>What is the impedance of the circuit. </p>
<p>I tried this: $224W=I^... | g11958 | [
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<p>Recently there is renewed interest in the ideas of Vasiliev, Fradkin and others on generalizing gravity theories on deSitter or Anti-deSitter spaces to include higher spin fields (utilizing known loopholes in the Weinberg-Witten theorem by including infinitely many higher spin fields and by working with asymptotic c... | g11959 | [
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<p>How can parts of a laser beam be made visible while others left invisible using something electronically controllable (for example, another laser beam crossing it, or a magnetic field, or heat, etc).</p> | g11960 | [
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<p>I understand that the <a href="https://en.wikipedia.org/wiki/Electromagnetic_tensor" rel="nofollow">Electromagnetic Tensor</a> is given by</p>
<p>$$F^{\mu\nu}\mapsto\begin{pmatrix}0 & -E_{x} & -E_{y} & -E_{z}\\
E_{x} & 0 & -B_{z} & B_{y}\\
E_{y} & B_{z} & 0 & -B_{x}\\
E_{z} &... | g11961 | [
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<blockquote>
<p><em>Consider the product of vectors coordinated relative to a given coordinate frame, defined by</em>
$$\vec{a}\square\vec{b}=((a_{1},b_{1})\square(a_{2},b_{2})):=(a_{1}b_{1},a_{2}b_{2})$$
<em>Explain why that in the context of vectors this is no good.</em></p>
</blockquote>
<p>My work:</p>
<p>... | g11962 | [
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<p>I asked a version of this question over on <a href="http://math.stackexchange.com/questions/667027/naming-and-meaning-of-exponential-power-functions">Math.SX</a>, and never received a response… perhaps it will be more appropriate here.</p>
<p>I'm looking at spectroscopic data (specifically a $T_2$ coherence decay c... | g11963 | [
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<p>What is the difference between <a href="http://en.wikipedia.org/wiki/Isospin" rel="nofollow">isospin</a> and <a href="http://en.wikipedia.org/wiki/Weak_isospin" rel="nofollow">weak Isospin</a>? What is the difference between <a href="http://en.wikipedia.org/wiki/Hypercharge" rel="nofollow">hypercharge</a> and <a hre... | g11964 | [
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<p>As we all know temperature of space is near to absolute zero.Then why super conductors aren't used there?</p> | g11965 | [
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<p>Here is a question that a friend asked me. He had to an experiment in school and do some calculations afterwards. Those calculations require maximal current that the DC source can produce. He has measured the maximal currents for two separate sources but forgot to measure it for both connected in series.</p>
<p>If ... | g11966 | [
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<p>If molecules at the surface of a liquid have higher energy and want to minimise the surface area, then why is a mensicus formed which of course increases the surface area?</p> | g11967 | [
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<p>I'm looking for unique and illustrative ways to explain the phenomenon of interference to a tour group consisting of all types of people, from elementary school kids to adults. I run into this problem from time to time at the <a href="http://www.ligo-la.caltech.edu/" rel="nofollow">LIGO Livingston Observatory</a>. ... | g11968 | [
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0.030483894050121307,
-0.006894577760249376,
0.0336679108440876,
-0.02420756220817566,
-0.0018111204262822866,
0.... |
<p>The wikipedia page "<a href="http://en.wikipedia.org/wiki/Force_carrier">Force Carrier</a>" says:</p>
<blockquote>
<p><em>The electromagnetic force can be described by the exchange of virtual photons.</em></p>
</blockquote>
<p>The virtual photon thing baffles me a little. I get that <a href="https://en.wikipedia... | g808 | [
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<p>I apologize if this question is naive. I am wondering about what would happen with the following experiment.</p>
<p>Start with a standard Bell's Theorem setup: We have two quibits entangled in a particular way and sent in opposite directions, where they are measured by independent observers. The distribution of joi... | g11969 | [
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<p>Lightning strike is categorized as DC because of its electrostatic nature. The negative flash/stroke is found to have 200KA of current with a voltage close to 300KV (cloud to ground). But why is it referred to as a High frequency source, since it does not have a frequency component? In an electric circuit diagram ... | g11970 | [
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<p>My wife made Rose-hip syrup and the final part was boiling it in a saucepan. While still hot she placed it in a glass bottle. To keep it sterile she plugged it with a wine-saver top and sucked out some of the air - so the (inch or so) space in the bottle is at lower than atmospheric pressure. Large bubbles are spon... | g11971 | [
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<p>This is probably a stupid and simple question, but does the heisenberg uncertainty principle set this upper bound? That knowledge of the momentum is limited, so it can't reach a very low value and thus have a very large (visible) debroglie wavelength? I am figuring if you wanted to test this on a macroscopic particl... | g379 | [
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<p>I'm not sure if this is a duplicate.</p>
<p>Whenever physics buffs talk about Einstein's relativity (I forget which kind) at high speeds, they always talk about "length contraction", or shortening of the object due to the high speeds. This happens even at the relatively low speeds we travel at every day, but there ... | g11972 | [
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<p>A bug eats through an apple and forms a vertical, infinitesimally thin canal parallel to the vertical diameter at a distance $\frac{R}{2}$ from the center. The apple rotates at angular velocity around that center equal to $\sqrt{\frac{g}{R}}$. As the bug attains the other side of the apple it slips and falls through... | g11973 | [
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<p>The mathematical formula for <a href="http://en.wikipedia.org/wiki/Work_%28physics%29" rel="nofollow">work</a> says that work is force into displacement, but what is the philosophy behind it? I mean what does the quantity suggest?</p> | g380 | [
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<p>It seems that popular textbooks on electrodynamics do not discuss how to solve the <a href="http://www.google.com/search?as_q=Laplace+equation+ellipsoidal+coordinates" rel="nofollow">Laplace equation</a> in <a href="http://en.wikipedia.org/wiki/Ellipsoidal_coordinates" rel="nofollow">ellipsoidal coordinates</a>. I c... | g11974 | [
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0.017854... |
<p>According to Darcy's Law, the volumetric flow rate Q of a fluid occuring due to a pressure difference $\Delta p$ over a distance L and through a cross-sectional area A of a porous medium (volume V) is given by:</p>
<p>$$Q = \frac{k\cdot A}{\mu}\cdot \frac{\Delta p}{L}\tag{1}$$</p>
<p>When calculating the pressure... | g11975 | [
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<p>A friend asked me if it would be possible to make soap bubbles out of a gas like hydrogen and if you did, would they float higher, faster. Due to the lower mass of light gases (compared to the air) I know they will float up faster (buoyancy). I wonder how stable they would be though.</p>
<p><strong>My question is... | g11976 | [
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... |
<p>If I have two pieces of steel that I would like to weld with a laser (say $d$ in diameter). If I wanted to melt the two pieces to a depth of $d$ along the edge and then combine them together, how much power for the laser would I need?</p>
<p>Is this simply $ P = A*\sigma * T_{\text{melting}}^4$?</p>
<p>Also how fa... | g11977 | [
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<p>[This is a version of the question that I've revised based on helpful comments from Dan.]</p>
<p>I haven't studied inflation at a technical level. My picture of the process is that we have an inflaton field $\phi$ which is a scalar and has a potential $V(\phi)$. Before inflation, the field starts at some $\phi_o$ t... | g11978 | [
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<p>Poiseuille's Law relies on the fact that velocity is not constant throughout a cross-section of the pipe (it is zero at the boundary due to the no-slip condition and maximum in the center). By Bernoulli's Law, this means that pressure is maximum at the boundary and minimum at the center. But in the book I have it ... | g11979 | [
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<p>I am trying to understand how is it possible for electric force to behave like this (path independence)?</p>
<p>I am repeatedly failing to get an intuitive meaning behind its (electric field) nature of doing the work.</p>
<p>Does it have to do with the radial direction of electric force ? or Its inverse-square law... | g11980 | [
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<p>I am writing an article and the central results are summarized in a graph so I want it to be very beautiful and physically intuitive. It has 3 regions in which a certain quantity is conserved, partially conserved or not conserved so I want them to be respectively green, yellow/orange and red. The problem is that I c... | g11981 | [
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<p>Many quantum-gravity theories are strongly interacting. It is not clear
if they produce the gravity as we know it at low energies. So I wonder, is there
any quantum-gravity theory that</p>
<p>a) is a well defined quantum theory at non-perturbative level (ie can be put in a computer to simulate it, at least in princ... | g11982 | [
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<p>I am very puzzled by the motivation for Mohr's circle in Wikipedia <a href="http://en.wikipedia.org/wiki/Mohr%27s_circle" rel="nofollow">here</a>. Please, explain why we need something called <em>"Mohr's circle"</em>. Use as little words as possible and be precise.</p>
<p><strong>Helper questions</strong></p>
<blo... | g11983 | [
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<p><img src="http://i.stack.imgur.com/SIL3d.jpg" alt="enter image description here"></p>
<ol>
<li><p>What is $V_{\alpha\beta}$? </p></li>
<li><p>And what is a symmetric, <a href="http://en.wikipedia.org/wiki/Positive-definite_matrix" rel="nofollow">positive definite</a> potential energy matrix? </p></li>
<li><p>And wh... | g395 | [
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<p>Suppose I can compute interaction energy of two rigid bodies as a function of their coordinates of centers of masses and Euler rotation angles (total 6 + 6 degrees of freedom). Now I can numerically compute force acting on the center of mass of the body by calculating numerical derivatives e.g. $F_x = (E(x + dx) - E... | g11984 | [
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<p>My friend keeps telling me that according to physics...</p>
<p><em>"The sun attracts a grain of sand on the earth with the same force that the grain of sand attracts the sun"</em></p>
<p>or</p>
<p><em>"A grain of sand on the earth attracts the sun"</em></p>
<p>Is that true? Does in theory a grain of sand really ... | g11985 | [
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<p>Gentlemen I have a similar yet very practical problem that might provide further insight.
I'm trying to model a moving plunger in a syringe (something like a piston in a cylinder).
At time zero the plunger is at rest, the pressure (behind the plunger) is atmosphere and the volume zero. Then I open (hydrogen) gas whi... | g11986 | [
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<p>Why does Quantum Field Theory use usually Lagrangians rather than Hamiltonains?</p>
<p>I heard many reasons, but I'm not sure which is true. </p>
<p>Some say it's just a matter of beauty, so Lagrangians are more beautiful because they don't break/separate the space-time variables (so space-time is a single variabl... | g381 | [
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<p>From my understanding of relativity, gravity is not a force, but a result of the curvature of spacetime. If Object1 moves past Object2, even though it's moving in a straight line, its direction may change due to the distortion caused by Object2's mass.</p>
<p>However, what about the situation where Object1 is not m... | g11987 | [
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<p>Is there any generalized Schwarzschild solution for an arbitrary number of dimensions? Is it necessary to calculate each individually, or is there a relationship between them?</p> | g11988 | [
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<p>Let's say you have a point charge inside a conducting shell with an inner radius of 5cm and an outer radius of $7cm$. The point charge has a chard of $-4C$ and the shell a charge of $6C$. This means that the $-4C$ point charge attracts $4C$ worth of charge from the shell to the shell's inner surface. This leaves $2C... | g11989 | [
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<p>The <strong>E.M.F</strong> of a cell is the work done in moving a unit positive charge in a loop or from the terminal to the same terminal. The force it experiences is a <strong><em>conservative force</em></strong>. Therefore, the work-done in a loop should be zero which means the <strong>E.M.F</strong> of any cell ... | g11990 | [
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<p>How can you use the relaxation method to model negative dielectrics?</p>
<p>The relaxation method is usually used to model electrostatics problems but negative dielectrics are only see in dynamic systems.</p>
<p><strong>EDIT:</strong> To my knowledge at frequency, $f=0$, no materials act like they have a negative ... | g11991 | [
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<p>When an object is in free fall, we have:</p>
<p>$a(t) = g - \frac{c}{m}v(t)^2$</p>
<p>where $g$ is acceleration due to gravity, $m$ is the mass of the object, and $c$ is the coefficient of air resistance.</p>
<p>How does one get the distance traveled after t seconds? I tried integrating it, giving</p>
<p>$v(t) =... | g11992 | [
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<p>I am trying to understand this, and want to be very very clear. This is a homework question but I <strong>already attempted to answer it</strong>, so please don't put this question on hold.</p>
<p>The question </p>
<blockquote>
<p>What atomic terms are possible for the electronic configuration ns1nd1? Which term... | g11993 | [
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<p>so the question is:</p>
<blockquote>
<p>I whirl a mass m attached to a wire with length L and diameter d
around my head in the horizontal plane. The mass takes t seconds to
move around a circle. How far do the atoms in the wire move apart,
compared to their spacing at rest? Young's modulus is given as Y.</p... | g11994 | [
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-0.029885774478316307,
-0.02835853397846222,
0.02878027968108654,
-0.03936324641108513,
-0.03468535095453262,
0.012719286605715752,
-0.05219697207212448,
-0.006738999392837286,
-0.060930702835321426,
-... |
<p>All discussions of Pauli exclusion principle I read usually talked about antisymmetric wavefunctions, from which the princinple appears. But I would like to see a Hamiltonian for multiple fermions, which would have Pauli exclusion principle already incorporated into its eigenstates. I've looked into <a href="http://... | g11995 | [
0.038008108735084534,
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<p>I have the basic question that why so many superconducting materials are s-wave and d-wave pairing, but the p-wave superconductors are so rare in nature? An equivalent question may be that why topological materials are so rare in nature, but the answer to the this question may be more complicated then my first ques... | g11996 | [
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0.0288... |
<p>I am learning dynamics in <strong>special relativity</strong> and come across the <a href="http://en.wikipedia.org/wiki/Stress-energy_tensor" rel="nofollow">stress-energy tensor</a>. I have real trouble understanding it. I would love answers on </p>
<ol>
<li>How to motivate the definition of this tensor. </li>
<li>... | g11997 | [
0.048076122999191284,
0.12533223628997803,
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0.026797950267791748,
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-0.... |
<p>Some sources suggest that the <a href="http://en.wikipedia.org/wiki/Andromeda_Galaxy">Andromeda Galaxy</a> is likely to collide with our own in approximately 3 to 5 billion years.</p>
<p>We can estimate the distance to the Andromeda Galaxy using various techniques, including measuring the apparent brightness of <a ... | g11998 | [
0.017898136749863625,
0.008430837653577328,
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0.00391... |
<p>Whenever I did calculations in high school physics involving gravity, it was either "a ball falling to the earth" type scenario, or a basic measurement of the gravitational attraction between two planetoids. </p>
<p>I think I read somewhere recently that gravitational changes "aren't reflected instantly across the ... | g4 | [
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0.0297... |
<p>Why is it such a good idea to plot the logarithm of the form factor vs $Q^2$ in Guinier plots. It seems arbitrary to me.</p>
<p>Thanks</p> | g382 | [
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0.06823153793811798,
-0... |
<p>We know that the theory of heat engines is that, if you accept the second law of thermodynamics,
$\Delta S > 0$
then you can define temperature using
$\frac{1}{T} = \frac{\partial S}{\partial E}$
And you would arrive at the conclusion that heat can only go from higher temperature to lower temperature reservoirs.... | g11999 | [
0.08448635041713715,
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0.06614331156015396,
-0.0485... |
<p>sorry for reposting.</p>
<p>I dont get why it is such a good idea to plot the logarithm of the form factor vs $Q^2$ in Guinier plots. It seems arbitrary to me.</p> | g382 | [
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0.0654008612036705,
-... |
<ul>
<li><p>Einstein has suggested that light can behave as a wave as well as like a particle i.e, it has dual character. In 1924, de-Broglie suggested that just as light exhibits wave and particle properties, all microscopic material particles such as electrons, protons , atoms, molecules, etc. also have dual charac... | g379 | [
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0... |
<p>I was reading a thread about <a href="http://astronomy.stackexchange.com/questions/1182/if-the-earth-didnt-rotate-how-would-a-foucault-pendulum-work/1183#1183">how a pendulum would be affected if the Earth did not rotate</a> and Larian's answer made me wonder if all planets rotate necessarily due to physics.</p>
<p... | g12000 | [
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0.022587956860661507,
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0.004945551976561546,
-0.0... |
<p>Does anyone know any way of estimating the net baryon density in collision experiments, e.g. in LHC, RHIC, or the upcoming ones at GSI-FAIR?</p>
<p>I have comes across many hand-waving arguments, sample - </p>
<ol>
<li><p>Electron-positron colliders start with $\rho_B = 0$, and since conservation laws have to resp... | g12001 | [
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0.034... |
<p>Consider a string stretched between a D0-brane and an anti-D0-brane. In this case as the stretching energy is greater than the quantum zero point energy the string will have a positive mass. But, as the D0-brane and the anti-D0-brane come closer to annihilate the string becomes a tachyon as now the major is from qua... | g12002 | [
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<p>A string which doesn't have any kind of vibrations will have mass whose square is negative due to quantum zero point energy. But why does it contribute negative rather than positive mass to strings? </p> | g12003 | [
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0.... |
<p>I was reading Wikipedia about the <a href="http://en.wikipedia.org/wiki/St._Francis_Dam" rel="nofollow">St. Francis Dam</a> and came across this sentence.</p>
<blockquote>
<p>Water that collected in the drainage pipes under the dam to relieve
the hydrostatic uplift pressure was carried off in this manner as
w... | g12004 | [
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<p>So I noticed for a few years ago while I'm riding on the bus and as we stop at a corner i tend to just look at the road while I'm listening to music, I noticed that as the bus driver had stopped i would see the ground shift forwards as if the bus is going backwards, but we are stopped and not in reverse. Also I have... | g12005 | [
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0.009865... |
<p>I'm trying to learn more about momentum and I'm a little confused. Based on my understanding, in an isolated system, total momentum is conserved in a collision. Today in class the professor went over an example of a car on a ferry driving from one end to the other, in the opposite direction of the ferry. According t... | g12006 | [
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0.015479526482522488,
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0.0110... |
<p>As per newton's first law, only an external force can bring any change in the acceleration of a body, internal forces cannot. So, when we apply brakes to an accelerating car, aren't those brakes(opposing force) part of internal forces? How can they put the car to a halt?</p> | g12007 | [
0.02694966457784176,
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<p>What really <em>is</em> the <a href="http://en.wikipedia.org/wiki/Maxwell_stress_tensor" rel="nofollow">Maxwell Stress Tensor</a>? I understand that it's derived from $$\mathbf {F} = \int _V ( \mathbf E + \mathbf v \times \mathbf B )\rho \ d \tau$$</p>
<p>Griffiths describes this as "total EM force on the charges i... | g12008 | [
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<p>I am looking for an estimate on the relationship between the rate of increase of power usage as the frequency of the processor is increased.</p>
<p>Any references to findings on this would be helpful.</p> | g12009 | [
0.039633557200431824,
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0.0073417904786765575,
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0... |
<p>I recently bought a new phone (Samsung Galaxy 3) and when the battery is fully loaded, it says like "Battery fully loaded, pull out the chord".
Is this a typo from Samsung, or would there theoretically be any reason (for battery saving purposes) to always have it going from the battery, and not from the chord.</p>
... | g12010 | [
0.06308301538228989,
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<p>I read some posts on this forum and some articles which repeatedly state that it is not impossible to build q-comps but to make it successful, physics needs a great breakthrough.
I tried finding but most of the material talks about how it works and what are current limitations, but how physics is going to help solv... | g12011 | [
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-0.0... |
<p>Perhaps this is a very basic question.</p>
<p>In chapter 14 of Srednicki's QFT textbook (2007), $O(g^2)$ loop corrections to the propagator of $\phi^3$ theory is discussed. However, I don't know how to derive the Eq. 14.34 on page 103 (I can't present the full context as it would be too long).
From
\begin{equation... | g12012 | [
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0.02770993486046791,
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0.05200422927737236,
0.0048547713086009026,
... |
<p>I remember reading this passage in the "Feynman Lectures", where Dr. Feynman describes an experiment in which a theoretical metal rod of length equal to the distance between Mars and Earth is arranged between mars and earth. Then the "rod handler" on earth gives the rod a push upwards. So the question posed is, will... | g4 | [
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0.0805669054389,
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0.01346906740218401,
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0.005855... |
<p>Suppose I have a pot with diameter $D$ containing a volume of water $V$, being heated by a flame under it. If the ambient air temperature is $T$ and relative humidity is $R$, how can I calculate the expected rate of loss due to evaporation over a period of time, $t$? Assume the period of time begins once the water b... | g12013 | [
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0... |
<p>It is known that <a href="http://physics.stackexchange.com/questions/65893/why-we-call-the-ground-state-of-kitaev-model-a-spin-liquid">the Kitaev Hamiltonian and its spin-liquid ground state both break the $SU(2)$ spin-rotation symmetry</a>. So what's the spin-rotation-symmetry group for the Kitaev model?</p>
<p>I... | g12014 | [
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0.0024353875778615475,
0.0004174952337052673,
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... |
<p>I'm told that if the total energy of an object near the Sun is negative, then it comes from the Solar System; if positive, it is extrasolar.</p>
<p>I don't understand why. Can someone please explain this?</p> | g12015 | [
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<p>I am having a hard time picturing waves, the image that comes to mind is a bobbing device submerged in still water which generates pulses in all directions (similarly in air). Then how can a wave be two dimensional? The classic image of an electromagnetic wave is a 3D wave function, x-y represent the electrical comp... | g12016 | [
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0.049050070345401764,
0.038... |
<p>When you flip a coin, you hear a ringing sound. I know that the source of the sound is the thumbnail hitting the coin, but it seems to be filtered by the spinning of the coin. Specifically, the faster the coin spins, the smoother the tone and it seems the spectrum becomes more uniform.</p>
<p>So my question is, phy... | g12017 | [
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0.0044527314603328705,
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0.02660270221531391,
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-0.0... |
<p>let's say I want to model a star of radius $R$ at a distance $r$ from the Earth. I need to show that the apparent luminosity for frequency $\nu$ is equal to</p>
<p>$$\ell(\nu)=\frac{2\pi h}{c^2}\left( \frac{R}{r}\right)^2\frac{\nu^3}{\exp\displaystyle\left(\frac{h\nu}{kT}\right)-1} $$</p>
<p>Which is Planck's law ... | g12018 | [
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-0.... |
<p>In the famous paper by Polchinski where he shows that D-branes are sourcing RR fields, he says (before we known the result) that RR sources must be objects with tension going like $1/g_s$ (page two of the paper). How do we know that? I understand that it must be non-perturbative in $g_s$ (essentially because strings... | g12019 | [
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<p>I remember being taught in elementary physics that while it makes
sense to add volumes, masses, or heat, it makes no sense to add
temperatures.</p>
<p>As I wanted to use that to illustate some other issue, I checked it on
wikipedia, and discovered the concept of intensive and extensive
properties of materials and s... | g12020 | [
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<p>I'm reading the book Gödel, Escher, Bach: an Eternal Golden Braid and on Chapter V, Hofstadter talks about different examples of recursive structures and processes. By page 142 of the 20th anniversary edition, he starts talking about recursion at the lowest level of matter, that is, according to him, related to the ... | g12021 | [
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<p>I know only that it states some variations of the Sun's magnetic fields. What is the <a href="http://www.google.com/search?q=rosenberg+coleman+effect" rel="nofollow">Rosenberg-Coleman effect</a> specifically?</p> | g12022 | [
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<p>Can anybody explain how Rutherford bombarded a 0.0004 cm thick gold foil? How did he put it in a photographic sheet? Wasn't the foil too thin to be held? How did he know that the atoms were deflected at various angles? Did he calculate every alpha particle's angle of deflection?</p> | g12023 | [
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<p>Suppose one knows in full detail the phase and intensity of monochromatic light in a plane. This is basically what a hologram records, at least for some section of a plane. By using this as the boundary condition for the wave equation, you should in principle be able to solve for the phase and intensity of light a... | g12024 | [
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<p>I'm taking a particle physics course and we're using Perkins Introduction to High Energy Physics as the text. I am looking at problem 1.7. It asks whether $$\pi^0\rightarrow e^- + e^+$$ is allowed or forbidden by the Standard Model based off of conservation laws. I feel it doesn't violate any of them. Energy and mom... | g12025 | [
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<p>I have to find the uncertainty of a quantity $Q$ doing two mean values. For example for a set of parameters I measure ten times $Q$, I obtain a mean value $Q_1$ and variance ${\rm Var}(Q_1)$. Then for a different set of parameters I measure ten times $Q$ and obtain $Q_2$ and ${\rm Var}(Q_2)$ etc. At the end I comput... | g12026 | [
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<p>In quantum field theory or condensed matter physics, the fermionic one-loop diagram gives rise to the polarization tensor</p>
<p>$$ Π^{µν} = Tr[ γ^µ G γ^ν G ] $$</p>
<p>If we couple the electrons to an electromagnetic field, we can integrate out the electrons again and obtain an effective action for the ... | g12027 | [
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