question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>How much knowledge of maths is required for learning <a href="http://en.wikipedia.org/wiki/Lagrangian_mechanics" rel="nofollow">Lagrangian mechanics</a>? Also from where can I learn this math?</p> | g98 | [
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<p>So I know that Einstein and general relativity had huge impacts on the way we view the world, but how crucial were these scientific advancements to the success of our space programs? Would Newtonian physics sufficed, or would using those formulas and methodologies when travelling off-earth and to the moon resulted i... | g8617 | [
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<p>so this might have some duplicated inquiry that <a href="http://physics.stackexchange.com/questions/1586/what-if-physical-constants-were-increased-or-decreased">this question</a> <a href="http://physics.stackexchange.com/questions/78684/why-is-it-meaningless-to-speak-about-changes-in-a-dimensional-constant">or this ... | g283 | [
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<p>If I understand Roger Penrose's theory, as the Universe expands and cools, matter is consumed by black holes. Eventually the black holes collide and evaporate so that there is only energy and the Weyl tensor (which relates to matter) heads to zero. He argues at zero, there is no effective space-time (my paraphrase)... | g8618 | [
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<p>I was told that the name 'Milky Way' first came about when people observered the milky looking stretch of sky; that is, before telescopes came about and we realised it wasn't a milky cloud, but rather a collection of stars, our galaxy.</p>
<p>So strictly speaking, Milky Way refers to that visible milky patch in the... | g8619 | [
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<p>In the text, it reads that the momentum of a particle will change if it is moving at speed close to light speed. In the general case, the wavelength is given as
$$
\lambda = \frac{h}{p}
$$
and
$$p = \frac{mv}{\sqrt{1-v^2/c^2}}$$
when $v \to c$, $p\to\infty$, so is it say that the wavelength is ZERO? I don't unde... | g8620 | [
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<p>Given a light pulse in vacuum containing a single photon with an energy $E=h\nu$, what is the peak value of the electric / magnetic field?</p> | g742 | [
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://physics.stackexchange.com/questions/11136/what-has-been-proved-about-the-big-bang-and-what-has-not">What has been proved about the big bang, and what has not?</a> </p>
</blockquote>
<p>I know the expansion of the universe is the most compe... | g284 | [
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0.0488... |
<p>Would it be possible to create a habitable in terms of gravity planet that would rotate with the black hole acting as a center of gravity? The rotation of the structure would lessen the gravitational force, so it would be much harder to access it from outside. Would the rotation of the planet be sufficient to lessen... | g8621 | [
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<p>I'm trying to write a program to procedurally generate solar systems at a reasonably high level (I'm not interested in doing an n-body dust particle formation simulation).</p>
<p>Is there some sort of distribution that defines where I am most likely to find mass inside a solar system? i.e. should I expect heavier p... | g8622 | [
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<p>According to a book I'm reading, the <a href="http://en.wikipedia.org/wiki/Fourier_transform" rel="nofollow">Fourier transform</a> is widely used in <a href="http://en.wikipedia.org/wiki/Fourier_transform#Uncertainty_principle" rel="nofollow">quantum mechanics</a> (QM). That came as a huge surprise to me. (Unfortuna... | g8623 | [
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<p>Suppose Winger's friend is placed into a black box, thoroughly isolated from the outside world.</p>
<p>He constantly observes an atom with a delay of some microseconds. According to Zeno effect, atom's lifetime will increase.</p>
<p>He writes his observations to a log.</p>
<p>After a day passed, the box is opened... | g8624 | [
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<p>Trying to understand Schutz's AFCIGR, where does the minus sign appear from in the metric tensor?</p>
<p><img src="http://i.stack.imgur.com/jXilu.gif" alt="metric"></p>
<p>I understand that this expresses the invariance of the spacetime interval. Schutz says (I think) that the metric is a (0,2) tensor. I assume th... | g8625 | [
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<p>I have often heard neighbours talking things like in a multi storied apartment, the upper flats are more hot in summer then lower flats (or vice versa?) and similarly for some comparison in winter? and similarly something for basement..</p>
<p>I have never understood these things well, even though people talk as if... | g8626 | [
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<p>I'm reading chapter 3 of Peskin and Schroeder and am stuck on page 43 of P&S. They have defined the Lorentz generators in the spinor representation as:
\begin{equation}
S^{\mu \nu} = \frac{i}{4}[\gamma^\mu,\gamma^\nu]
\end{equation}
such that a finite transformation is given by:
\begin{equation}
\Lambda_{1/2}=e^... | g8627 | [
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... |
<p>How does a <a href="http://en.wikipedia.org/wiki/Tesla_coil" rel="nofollow">Tesla Coil</a> exactly work? I am currently making a Tesla Coil in school but before I start, I want to know exactly how does a Tesla Coil work? I understand the various electrical components used in it, but what I don't understand is how do... | g8628 | [
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<p>I have been learning about time and the different dilation effects of gravity and relative velocity. I was wondering, are there any other factors that can affect time?</p> | g8629 | [
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<p>Let's say you have two bodies at are held at rest relative to each other exchanging (real, not virtual) photons back and forth. Then we let them go (maybe push them apart slightly), so they will begin to move apart at some velocity. Now, if they have a relative velocity between them, the photons absorbed will be o... | g8630 | [
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<p>Last year I attended an introductory particle physics course, in which the <a href="http://en.wikipedia.org/wiki/Eightfold_Way_%28physics%29">Eigthfold Way</a> for classifying hadrons has been discussed.</p>
<p>The main idea consists in grouping hadrons in <a href="http://en.wikipedia.org/wiki/Multiplet">multiplets... | g8631 | [
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<p>Conservation of energy in an electrical circuit can be expressed by Ampere's law $$\nabla \times \textbf{B} = \mu_o
\textbf{J} + \epsilon_o \mu_o \frac {\partial \textbf{E}} {\partial t}$$ when both sides of the equation are dotted with $\textbf{E}$ and the input power is placed on the left side of the equation... | g8632 | [
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0.044... |
<p>I am trying to compute the amount of oblateness that is caused by planetary rotation. I picture the force of gravity added to the centrifugal force caused by the rotation of the planet as follows:</p>
<p>$\hspace{4cm}$<img src="http://i.stack.imgur.com/Nfv6f.png" alt="forces"></p>
<p>That is, at the point in quest... | g8633 | [
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-0.0... |
<p>If we consider a balloon full of air submerged in water then we all know that it will rise rapidly. I am having trouble understanding this at the level of individual molecules of air and water. What is a molecular/microscopic explanation for this phenomenon?</p> | g8634 | [
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<p>For instance, if we choose the following scalar field Lagrangian, which is (I hope) Lorentz-invariant, where $l$ is a a length scale, and with a $(-1,1,1,1)$ metric: </p>
<p>$$ \mathfrak{L}(x) \sim l^{-6} \int d^4y \space e^{\frac{- y^2}{ l^2}} (\Phi(x + y)\Phi(x - y) - \Phi(x) \Phi(x)) $$</p>
<p>There are no... | g8635 | [
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<p>I'm looking for a reference, journal article, paper, etc. that supports the idea that classical mechanics, in particular rigid body dynamics, is largely <a href="http://en.wikipedia.org/wiki/Predictability" rel="nofollow">predictable</a>.</p>
<p>A view coming from the background of computer physics simulations woul... | g8636 | [
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<p>I need to know the mathematical argument that how the relation is true $(C^{-1})^T\gamma ^ \mu C^T = - \gamma ^{\mu T} $ .
Where $C$ is defined by $U=C \gamma^0$ ; $U$= non singular matrix , $T$= transposition, $\gamma^0= $Dirac gamma matricx = $\beta$ </p>
<p>I need to know the significance of these equation i... | g8637 | [
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<p>I was reviewing the first few chapters of Weinberg Vol I and found a hole in my understanding in page 112, where he tried to show in the asymptotic past $t=−∞$, the in states coincide with a free state. In particular, he argued the integral</p>
<p>$$\tag{1} \int d\alpha\frac{e^{-iE_{\alpha}t}g(\alpha)T_{\beta\alpha... | g8638 | [
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<p>I have a sphere (mass = 3 kg), constrained to a fixed length rope, rotating (radius = 5 m) on a vertical plane.
My textbook ask me about the minimum speed in the highest point in order to keep the circular trajectory.</p>
<p>Now, I know that in the highest point (v=speed):</p>
<p>$$F_c=mg+T$$
$$\frac{mv^2}{r}=mg+... | g8639 | [
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<p>The theory of QEC with stabilizer codes defines an alternative way to represent a quantum state in terms of operators.
To understand better what I am concerning about, let's consider the 7-qubit Steane code:</p>
<p>$$
\left|0\right\rangle_L \equiv \frac{1}{\sqrt{8}}(\left|0000000\right\rangle + \left|1010101\right... | g8640 | [
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... |
<p>Has the <a href="http://www.enwp.org/Standard_Model_%28mathematical_formulation%29" rel="nofollow">Standard Model of Particle Physics</a> been experimentally verified? Or is it still waiting for experimental verification? OR,</p>
<p>What aspects/predictions of the Standard Model have been experimentally ver... | g8641 | [
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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>I am currently in the 11th grade (I am an Indian student) and I am looking forward to studying pure mathematics and theoretical ... | g98 | [
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<p>I have read about this and what I surmise is that when charged particles such as electrons accelerate they produce time-varying electric fields. These E-fields produce H-fields and the process goes on. </p>
<p>1.) Are the EM fields really moving. My textbooks says it's changes in field that is moving. I don't under... | g8642 | [
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0.01148711983114481,
-0.00020323526405263692,
0.016261620447039604,
0.09151016175746918,
0.06495825946331024,
0.0548015795648098,
0.060061901807785034,
-0.027008699253201485,
-0.008944064378738403,
-0.07602981477975845,
0.04887400567531586,
0.016470007598400116,
0.01639... |
<p>Why was the <a href="http://en.wikipedia.org/wiki/Luminiferous_aether" rel="nofollow">Ether Theory</a> refused by Modern Physics? If you please explain me, I just wanted to understand it more. </p> | g761 | [
0.021998025476932526,
0.056260354816913605,
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0.08748418092727661,
-0.00814683735370636,
0.01572323590517044,
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-0.06945662200450897,
0.053829606622457504,
-0.032044682651758194,
0.0868927389383316,
0... |
<p>I know that if the integral is convergent we can always make a change of variable to make it better, however what happens with DIVERGENT integrals? can we make a change of variable into a divergent integral after having it regularized?</p>
<p>I mean we insert the regulator $(q+a)^{-s}$ or similar on each variable a... | g8643 | [
0.03425003960728645,
-0.015478866174817085,
-0.0026408659759908915,
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0.015004160813987255,
-0.02702139876782894,
-0.002614524681121111,
0.0069207665510475636,
-0.024212758988142014,
0.00799582526087761,
-0.11045746505260468,
0.044629525393247604,
-0.01846182346343994,
... |
<p>I notice in the <a href="http://en.wikipedia.org/wiki/Electromagnetic_spectrum" rel="nofollow">EMS</a> chart that only half of the IR range will travel through the earth's atmosphere. So in the range of frequencies that penetrate the atmosphere what frequency travels farthest?</p> | g8644 | [
-0.012195225805044174,
0.037751950323581696,
-0.0014396742917597294,
0.005054393783211708,
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0.020107783377170563,
-0.04130812734365463,
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-0.04130768030881882,
0.06169329211115837,
0.02447417378425598,
-0.0034883380867540836,
-0... |
<p>I have been trying to find an equation (or some solution) of how to calculate the electric field strength (in N/C) of a conducting rectangular (nearly flat) plate which has non-zero potential to it, say the plate has a potential of 5V. </p>
<p>I have searched over the internet (and read Griffiths book on the method... | g8645 | [
0.051136042922735214,
0.04465087130665779,
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0.0726841539144516,
0.01777326874434948,
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0.017931899055838585,
-0.025444170460104942,
0.0458308681845665,
-0.03604171425104141,
0.04788... |
<p>I really can't understand the power loss law. If we have a wire carrying a $15\:\mathrm{V}$ and $1\:\mathrm{ A}$ going into an inverter, giving $150\:\mathrm{V}$ and $0.1\:\mathrm{A}$, if we want to calculate the power loss as heat in wires, we use $P = I^2 R$ or simple $P=VI$, does that mean that all power is lost... | g8646 | [
0.01269991509616375,
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0.011645507998764515,
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0.022580217570066452,
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0.0038416290190070868,
-0.01679384894669056,
0.03015827015042305,
-0.08304684609174728,
... |
<p>In the standard model (omitting the QCD part), we start off with the set of generators </p>
<p>$T_1$, $T_2$, $T_3$, $Y$ </p>
<p>for the four-parametric gauge group $SU(2)_L \times U(1)_Y$.</p>
<p>We then define a new generator $Q= T_3+Y$ and make the transition to the four-parametric gauge group $SU(2)_? \times U... | g8647 | [
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0.020451080054044724,
0.006413744296878576,
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0.006509528961032629,
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-0.... |
<p>I am not sure whether it is some well-known named model in statistical physics.
I could not find it in any standard text-book that I know of. </p>
<p>Let there be $N$ identical classical particles occupying a square lattice of $2N$ sites with at most one particle per site. Let the alternate sites be names $A$ and ... | g8648 | [
-0.0056195431388914585,
0.04310747981071472,
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0.020824579522013664,
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-... |
<p>It's my understanding that <a href="http://en.wikipedia.org/wiki/General_relativity" rel="nofollow">General Relativity</a> abstracts away the concept of gravity as a force, and instead describes it as a feature of spacetime by which massive objects cause curvature. Then it follows that what we experience as a force... | g8649 | [
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0.003542... |
<p>There is a small area element of size $da$ and normal vector $\hat n$. </p>
<p>I understand that the particles with speed $|\vec v|$ that hit this area element in the time interval $(t,t+\delta t)$ lie in a spherical shell with radius $r=|\vec v|t$ at $t=0$. Let the number of particles with energy $E(|\vec v|)$ wit... | g8650 | [
0.058330487459897995,
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-0.01... |
<p>A naïve observational viewpoint doesn't automatically try to correct for signal delays. In other words, the time co-ordinate is <a href="http://en.wikipedia.org/wiki/Retarded_time" rel="nofollow">retarded</a>. </p>
<p>For example:</p>
<p>In popular expositions of relativity you'll find things like "moving observer... | g8651 | [
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0.01625927910208702,
-0.0375332348048687,
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0.0173356831073761,
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0.05703684315... |
<p>I am unclear about the adjective "first" or "second" used in phase transitions. Take the liquid-gas transition for example. If we vary the volume of the system at constant T, at some point we will have two phases co-existing. The relevant free energy of the complete system (liquid+gas), the Helmholtz free energy $A... | g8652 | [
0.03561898693442345,
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0.00467162299901247,
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-0.0... |
<p>There is a possible CP-violating term in the strong sector of the standard model proportional to $\theta_\text{QCD}$. In the absence of this term, the strong interactions are CP-invariant. In the weak interactions, there is CP-violation that comes from the lone phase $\delta$ appearing in the CKM quark-mixing matr... | g8653 | [
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0.... |
<p>The other day in my string theory class, I asked the professor why we wanted to quantize gravity, in the sense that we want to treat the metric on space-time as a quantum field, as opposed to, for example, just leaving the metric alone, and doing quantum field theory in curved space-time. Having never studied it, i... | g8654 | [
0.01252820435911417,
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0.06459713727235794,
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... |
<p>Firstly, I understand that we have no observational evidence for 'wormholes'. They are theorised solutions to general relativity equations.</p>
<p>That said, if macroscopic wormholes do exist---how do they work? I've been thinking about this for the past couple of days, and I have some questions.</p>
<ul>
<li>What... | g8655 | [
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0.06036849319934845,
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0.029525119811296463,
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-0.005760315805673599,
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0.00442567327991128,
0.013932379893958569,
... |
<p>I understand that the Biot number is essentially the ratio of the convective effects to the conductive effects in transient conduction but what if there is some sort of radiation from a heat source like a heat lamp (neglecting surface to ambient radiation)</p>
<p>Would the Biot number then be the ratio of the conve... | g8656 | [
0.044460806995630264,
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0.008286375552415848,
0.014690376818180084,
0.04779810830950737,
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0.04675346985459328,
0.0437118299305439,
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-0.02074386551976204,
0.007579805329442024,
0.06439175456762314,
0.04033893346786499,
0.0291... |
<p>Does photon have size measurement because of its particle nature like electron's 3.86*10^-13m etc..</p> | g982 | [
0.01414795033633709,
0.06579329073429108,
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0.005455552600324154,
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0.014328762888908386,
0.0038317504804581404,
-0.006460372358560562,
0.016454730182886124,
0.02435523271560669,
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0.01... |
<p>Consider the following experiment. I take a spin-$\frac{1}{2}$ particle and make a $\sigma_x$ measurement (measure the spin in the $x$ direction), then make a $\sigma_y$ measurement, then another $\sigma_x$ one, then $\sigma_y$, and so on for $n$ measurements. The formalism of quantum mechanics tells us that the out... | g288 | [
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0.0004591707547660917,
0.010983064770698547,
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0.013953110203146935,
0.004692240618169308,
0.019973691552877426,
0.04208368435502052,
0.027532296255230904,
-0.04611542820930481,
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0.0018417479004710913,
... |
<p>Suppose we have a 2D polymer model described by a set of 2D vectors {$\mathbf{t}_i$} ($i=1,2,\dots N$) of length $a$. </p>
<p>The energy of the polymer is given by:
$$
\mathcal{H}~=~-k\sum^N_{i=1}\mathbf{t}_i\cdot\mathbf{t}_{i+1}
~=~-ka^2\sum^N_{i=1}\cos\phi_i.
$$</p>
<p>The constant $k$ is a measure of bending ri... | g8657 | [
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0.03564209118485451,
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0.0027699689380824566,
0.02832934260368347,
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... |
<p>My test paper asked me which way a dipole should be orientated in an electric field to minimize its potential energy. My answer was that the dipole should lie parallel to the electric field with the positive end of the dipole pointing in the direction of the electric field because that way, the positive end would be... | g8658 | [
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0.006333806551992893,
0.012136503122746944,
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... |
<p>In the book "Kinetic theory in the expanding Universe" (J. Bernstein, 1988, Camb. Univ. Press), it was stated that </p>
<blockquote>
<p>"for nonstationary Robertson-Walker
matrixes [sic] there is no spacelike
Killing vector."</p>
</blockquote>
<p>(page 6, footnote.)</p>
<p>But we know this is not true, sinc... | g8659 | [
0.025991098955273628,
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0.017621584236621857,
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0.006149617955088615,
0.033292777836322784,
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0.022469455376267433,
0.014237836003303528,
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0.04242519661784172,
0.0... |
<p>Given: Law of Conservation of Angular Momentum.</p>
<ul>
<li>Reverse spinning with dense atmosphere (92 times > Earth & CO2 dominant sulphur based).</li>
<li>Surface same degree of aging all over.</li>
<li>Hypothetical large impact is not a sufficient answer.</li>
</ul>
<p>Assuming any object large enough to a... | g231 | [
0.024474455043673515,
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0.017324263229966164,
0.027032164856791496,
0.05190296098589897,
0.0504029355943203,
0.005510115530341864,
0.04640422761440277,
-0.030671201646327972,
0.002033111173659563,
0.0017280607717111707,
0.07101134210824966,
-0.07... |
<p>Critical point is the transition temperature of a second order phase transition. But what does tricritical point mean? <a href="http://en.wikipedia.org/wiki/Tricritical_point#cite_note-1" rel="nofollow">WIki</a> says that a tricritical point is a point in the phase diagram of a system at which three-phase coexistenc... | g8660 | [
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0.0036392859183251858,
0.01673932932317257,
0.030237095430493355,
0.07213462144136429,
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0.04476932808756828,
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0.04548456519842148,
-0.03352998197078705,
-0.010177006013691425,
0.006494924891740084,
-0.0... |
<p>I want to calculate the tensor of the moment of inertia. Consider this situation:</p>
<p><img src="http://i.stack.imgur.com/lGUw1.png" alt="situation"></p>
<p>The dot represents a points mass, in size equal to $\frac{5}{4}m$. $m$ is the mass of the homogenous circle. I'm trying to calculate the tensor of inertia. ... | g8661 | [
0.007924729958176613,
-0.006069655064493418,
-0.004925874061882496,
-0.010165919549763203,
0.05161317437887192,
-0.014885315671563148,
0.12553659081459045,
0.00488086836412549,
-0.05857113003730774,
0.03915690258145332,
-0.046389348804950714,
0.007676922250539064,
0.029950283467769623,
-0.... |
<p>When talking about the rest energy of a composite particle such as a proton, part of the rest energy is accounted for by the internal kinetic energy of its constituent quarks. But what is physically meant by the rest energy of non-composite particles such as quarks?</p> | g8662 | [
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0.00015311846800614148,
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0.020615791901946068,
0.014312351122498512,
-0.025820773094892502,
0.06737496703863144,
-0.0055235037580132484,
-0.03823269531130791,
-0.0019645944703370333,
-0.04371888190507889,
-0.05736270174384117... |
<p>What is the definition of "precession"? How is it applicable to abstract objects such as Spinors? I understand the mathematics, but don't understand what one means by "precession angle" etc when it applies to abstract objects such as two spins?</p>
<p>In my (naive?) view, precession is defined as the rotation of a ... | g8663 | [
0.02511557564139366,
0.030497729778289795,
0.005732228979468346,
-0.00017365804524160922,
0.023346973583102226,
0.013468943536281586,
0.04987306520342827,
0.025776304304599762,
-0.02364535443484783,
0.024020470678806305,
-0.034144435077905655,
-0.014305248856544495,
-0.008641480468213558,
... |
<p>Can there only be a critical temperature if there is some natural unit for an observable in the model, i.e. if there is a natural scale for something? Otherwise I don't see how for a system there could be a rule how the value of $T_c$ gets actually terminated. And do this transitions vanish from the model, if one do... | g8664 | [
0.016456875950098038,
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0.018447645008563995,
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0.06472106277942657,
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0.002776102628558874,
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0.006316078826785088,
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0.010956008918583393,
0.... |
<p>In <a href="http://pra.aps.org/abstract/PRA/v23/i5/p2673_1" rel="nofollow">this</a> paper it is described how the turbulent kinetic energy spectrum and the <a href="http://physics.stackexchange.com/q/59788/2751">flatness</a> (a measure for intermittency) are governed by the position of the (dominant) singularities o... | g8665 | [
-0.02401728183031082,
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0.030734160915017128,
0.014037241227924824,
0.03333783894777298,
0.06336688250303268,
-0.0687258243560791,
0.00035952203324995935,
-0.005403501447290182,
0.0034953011199831963,
-0.01972297579050064,
0.... |
<p>This is a problem that has bothered me for a couple of weeks now, and I can't seem to wrap my head around it and understand it.</p>
<p>Let's say we have a planet with a mass of <strong>m</strong>. We also have an object of relatively small mass (so small that its gravitational field would not affect the planet), an... | g8666 | [
0.0672830194234848,
0.06706538796424866,
0.0051388973370194435,
0.011326272040605545,
0.014374644495546818,
0.019443707540631294,
0.04113539308309555,
0.015200449153780937,
-0.10065686702728271,
-0.01855136640369892,
-0.0014268729137256742,
0.032869502902030945,
0.036752112209796906,
-0.00... |
<p>The shuttle craft "Galileo" travels at a constant velocity of $2.73*10^3$ m/s up for $34.0$ min. and then turns around to travel $1.45*10^3$ m/s down for $15.0$ min.</p>
<p>a) Find its average speed.</p>
<p>b) Find its average velocity</p> | g8667 | [
0.006210444029420614,
0.05073856934905052,
0.0030369656160473824,
0.026690667495131493,
0.009202418848872185,
0.005857144948095083,
0.05823167413473129,
-0.021281342953443527,
0.0028648078441619873,
-0.030035585165023804,
0.029987890273332596,
0.026781976222991943,
0.01726011373102665,
0.0... |
<p>I have this problem:</p>
<blockquote>
<p>If the constant of gravity is measured to be $g_0$ in an earth fixed
coordinate system, what is the difference $g-g_0$ where $g$ is the
real constant of gravity as measured when the earth stands still.</p>
</blockquote>
<p>The earth fixed coordinate system is rotating... | g8668 | [
0.041297975927591324,
0.03944925591349602,
0.013282331638038158,
-0.029559969902038574,
0.042719386518001556,
0.04680794104933739,
0.09810750931501389,
0.0108664995059371,
-0.0851520299911499,
-0.0028625340200960636,
-0.033035606145858765,
0.042875077575445175,
-0.025743138045072556,
0.024... |
<p>In some PSE questions or answers such as <a href="http://physics.stackexchange.com/questions/67037/is-it-possible-to-have-uniform-proper-acceleration-along-a-large-object-without/68733#68733">here (and comments below)</a> there appears the notion of "<i>accelerating frame</i>" or (more or less equivalently) "<i>noni... | g285 | [
0.009238705039024353,
-0.012475411407649517,
0.000092696187493857,
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0.05154937133193016,
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0.07019279152154922,
0.03588409721851349,
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0.03827815502882004,
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0.0... |
<p>If we consider an object undergoing who has an acceleration proportional to the displacement of the object, it is going simple harmonic motion.</p>
<p>In terms of Newton's second law, this is $$ -\dfrac k mx = \dfrac{d^2 x}{dt^{2}} $$ where $k/m := \omega^2$, the frequency. </p>
<p>For an object floating because o... | g8669 | [
0.05077815428376198,
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<p>I'm reading some literature on mass loss in the RGB/AGB branches and so far I'm getting a lot of information regarding mass loss via dusty-winds/pulsations but almost no explanation of mass loss by 'chromosphere activity'. I asked my mentor about it and he couldn't come up with anything so I'm turning to whomever mi... | g8670 | [
0.02252138778567314,
0.02225276455283165,
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0.030777186155319214,
0.030612660571932793,
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0.10817567259073257,
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0.06572... |
<p>I have just got a query about how this equation works if its right.</p>
<p>We have <em>Newtonian Physics</em> saying $F=ma$,</p>
<p>According to the '<em>Mass in special relativity</em>' the mass changes according to
$$m= \dfrac{m_0}{\sqrt{1-\frac{v^2}{c^2}}}.$$</p>
<p>So, our </p>
<p>$$F=\dfrac{m_0}{\sqrt{1-\f... | g8671 | [
0.039979398250579834,
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<p>Suppose we have an operator $Q$ with eigenvalue $q$. Expectation value is $\langle Q \rangle$ and dispersion $D(Q) = \sqrt{\langle \left( Q - \langle Q \rangle \right)^2 \rangle} $. I want to find values for the expectation value and dispersion.</p>
<p><strong>Attempt</strong></p>
<p>Expectation value is simply t... | g8672 | [
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0.0036498031113296747,
0.01907213218510151,
... |
<p>Consider a canonical ensemble of $N$ ideal gas atoms, which could have spin up or spin down. Why is it that the probability of finding the particle in a spin up state generally only involves the single partition function?</p>
<p>In a canonical ensemble, $P_i = \frac{e^{-\frac{E_i}{kT}}}{Z}$.</p>
<p>$$P_{up} = \fra... | g8673 | [
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0.039787571877241135,
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<p>The Rabi model describes a two-level system interacting via a linear coupling with a quantized harmonic oscillator, and it is described by the hamiltonian
$$
H_{\rm{Rabi}}=\hbar\omega\, a^\dagger a +\hbar\omega_0\,\sigma_3+\hbar g\,\sigma_1(a+a^\dagger). \tag1
$$
Here $[a,a^\dagger]=1$, $\sigma_i$ are the Pauli matr... | g8674 | [
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<p>I'm reading the following paper:</p>
<blockquote>
<p>Intercomparison of Bulk Aerodynamic Algorithms for the Computation of
Sea Surface Fluxes Using TOGA COARE and TAO Data</p>
</blockquote>
<p>and am having trouble working through some of the equations, I have copied these equations below:</p>
<p><img src="ht... | g8675 | [
0.05282336100935936,
0.021300392225384712,
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0.0248121190816164,
0.005082306917756796,
0.11142653226852417,
0.003427643794566393,
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-0.0009206560207530856,
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0.1029544249176979,
0.028... |
<p>Say I have one LED in a flashlight, it produces some light. </p>
<p>Now, if I have 3 of those LEDs in the same flashlight, <em>each</em> LED receiving the same amount of energy than the single LED was receiving in the model described above (thus producing, individually, the same amount of light), will I get (percei... | g8676 | [
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0.012377765960991383,
0.03149614483118057,
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0.04094173014163971,
0.0036126598715782166,
0.... |
<p>Confinement of antihydrogen might help provide a future answer. <a href="http://arxiv.org/abs/1104.4982" rel="nofollow">http://arxiv.org/abs/1104.4982</a></p> | g286 | [
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<p>When we introduce minimal coupling for the Dirac spinor field, we introduce terms into the Lagrangian, by the substitution $i\frac{\partial}{\partial x^\mu}\mapsto i\frac{\partial}{\partial x^\mu}+eA_\mu$, so that the Lagrangian is invariant under arbitrary changes of phase at every point of space-time, $$\psi(x)\ma... | g8677 | [
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0.005106321536004543,
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... |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://physics.stackexchange.com/questions/9371/why-would-antimatter-behave-differently-via-gravity">Why would Antimatter behave differently via Gravity?</a> </p>
</blockquote>
<p>Regarding the following statement in <a href="http://www.technolog... | g286 | [
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0.023526934906840324,
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0.06469488143920898,
0.023196829482913017,
0.061880093067884445,
0.022718094... |
<p>How to show that if two masses($m_1$ and $m_2$) are connected($r_1<r_2$) with a string moving around a point A( circular motion), they move with same angular velocity? In this special case if $r_1=0.5 m$ and $r_2=0.9 m$, $m_1=m_2=0.15 kg$ => $ \omega = 6.9 rad/s$.</p>
<p>Picure below depicts the situation beside... | g8678 | [
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0.0417463518679142,
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<p>According to black hole complementarity, for an external observer, the interior of the black hole is replaced with a stretched horizon at a Planck distance above where the horizon ought to be. Is this stretched horizon an end-of-space boundary with a Gibbons-York term, or does it have an interior a la fuzzball comp... | g8679 | [
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0.009627961553633213,
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0... |
<p>I'm curious whether I can find the overlap $\langle q | p \rangle$ knowing only the following:</p>
<ol>
<li>$|q\rangle$ is an eigenvector of an operator $Q$ with eigenvalue $q$.</li>
<li>$|p\rangle$ is an eigenvector of an operator $P$ with eigenvalue $p$.</li>
<li>$Q$ and $P$ are Hermitian.</li>
<li>$[Q,P] = i \hb... | g8680 | [
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0.031951695680618286,
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0.021067986264824867,
0.... |
<p>There is no timelike Killing vector for FRW cosmologies. In the path integral formalism, is it possible to Wick rotate for quantum cosmology in quantum gravity? If yes, how? If no, how does one work with nonconvergent Lorentzian path integrals?</p> | g8681 | [
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<p>In my experiment, I am filling liquid crystal between two glass plates. Nn AC voltage is applied on them. The thickness of the liquid crystal cell is around $200 \mu m$. One glass plate is with +V and another with -V. Liquid crystal is aligned perpendicular to the electric field direction. Now I am inserting a metal... | g8682 | [
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<p>Suppose to have a chain (of size $L$) with bosons, and $\hat{a}_i^\dagger$,$\hat{a}_i$ are the associated creation and annihilation operators at site $i$. A Fock state can be written as:
\begin{equation}
| n_1 \dots n_L \rangle = \prod_{i} \frac{1}{\sqrt{n_i!}} \left( \hat{a}_i^\dagger \right)^{n_i} |\rangle
\end{eq... | g8683 | [
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0.03194660693407059,
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0.05351801961660385,
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0.0... |
<p>Imagine I throw a ball straight upwards with some velocity $v_1$, and filming the ball with a camera, I can estimate a velocity $v_2$ (along the same vector) after the ball has moved a distance $D$. Using the difference between $v_1$ and $v_2$, and assuming constant friction due to air, how well can I estimate the ... | g8684 | [
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<p>I'll be doing Introductory General Relativity and Graduate Quantum Mechanics II next semester. I still need to choose 2 (or maybe 3, but I don't want to overload too much) from the following:</p>
<ul>
<li><p>Algebraic Topology I: Sounds useful in both mathematical physics, and things like string theory, so leaning ... | g8685 | [
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0.0656106173992157,
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0.022921524941921234,
0.04057632014155388,
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<p>What would be the speed of a hypothethetical object created during the big bang, and that has been moving around in the universe and that is now close to the earth, so the time elapsed (from the hypothetical object's perspective) is around 6,500 years, that is the age of the universe according to some people?. </p> | g8686 | [
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0.02658151090145111,
0.009237125515937805,
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... |
<p>What is the furthest object from which non-electromagnetic cosmic rays were detected?</p> | g8687 | [
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<p>Say I have an ideal gas that has a known $P_1$, $P_2$, $T_1$, and $T_2$ undergoing a reversible adiabatic process. I want to find the work done so I must use $PV = RT$ to get the change in $V$, so that's $$\frac {P_1V_1}{T_1} = \frac {P_2V_2}{T_2}$$, and also $$W = \int PdV = P(V_2 - V_1)$$.</p>
<p>My problem is, t... | g8688 | [
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0.006486757192760706,
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0.062321268022060394,
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0.0813278928399086,
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... |
<p>If I have the following metric: </p>
<p>$$ds^2=(1-2\phi)c^2 dt^2 - (1-2 \phi)(dx^2+dy^2+dz^2)$$</p>
<p>$\phi$ being the gravitational potential with $|\phi| << 1$ everywhere. </p>
<p>How do I find a coordinate transformation to a locally inertial coordinate system to first order in $\phi$?</p>
<p>One metho... | g8689 | [
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0.040912967175245285,
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0.02178545482456684,
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0.041203346103429794,
0... |
<p>Suppose we have a helicopter that is able to stay stationary in flight for extended periods of time. If such a helicopter stayed at point A in the sky for 12 hours straight, would it reach the other side of the globe?</p> | g162 | [
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... |
<p>The movement of several metronomes <a href="http://www.youtube.com/watch?v=Aaxw4zbULMs" rel="nofollow">can be synchronised</a> when a movable floor is utilised which couples the movement of the different metronomes.</p>
<p>Is it possible to apply this sort of synchronisation to several swings occupied by people (th... | g8690 | [
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://physics.stackexchange.com/questions/10852/how-are-these-balls-reflected-after-they-hit-each-other">How are these balls reflected after they hit each other?</a> </p>
</blockquote>
<p>I was wondering what sort of physics equations would I ne... | g287 | [
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0.014637685380876064,
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0.03525055944919586,
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0.033229999244213104,
-... |
<p>I'm a retired Physics Professor, but I admit I'm puzzled by this... </p>
<p>Consider two loops of wire, 2 small dipoles B and C , with a common axis z (facing each other) and (say) 30 cm apart B to C. At the speed of light, information (including a change in magnetic field) will require about 1 nanosecond to trav... | g8691 | [
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<p>At the Advanced Photon Source, they use two accelerators before injecting the electrons into the large storage ring. Is the addition of particles to the storage ring done in "batches" (however small/short they may be), or continuously? </p>
<p>By a "batch", I'm thinking where the LINAC would throw however many el... | g8692 | [
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<p>After taking a basic signals & systems class and learning about the frequency domain, I started wondering:</p>
<h3>How the heck do scientists still communicate with Voyagers I and II??</h3>
<p> <br>
Do they send/receive signals in a frequency that is otherwise unusually silent? If not, then how do they se... | g8693 | [
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0.05820484086871147,
... |
<p>Material density is given by $ \rho =m/V$, where $m$ is mass and $V$ is volume.
Again number density given by $n=N/V$, where $N$ is the total number of particle. How can I calculate number density $n$ from material density $ \rho $.</p> | g8694 | [
0.05610256642103195,
0.0027576459106057882,
0.010521912947297096,
0.013233923353254795,
-0.001331777311861515,
0.004921262152493,
-0.016483793035149574,
-0.005981300957500935,
-0.02535857819020748,
0.006356473546475172,
-0.03353716805577278,
-0.009365389123558998,
0.007307555992156267,
0.0... |
<p>I haven't ever studied fluid dynamics before and may mix something here, so please, be patient :). </p>
<p>Given flow potential of the form (homogeneus flow over a dipole): </p>
<p>$$ \phi = u_\infty x -\frac{M}{2\pi} \frac{x}{x^2 + y^2} $$</p>
<p>how do I calculate pressure field? I know the answer is like below... | g8695 | [
0.0006977366865612566,
0.04630323871970177,
-0.012084446847438812,
-0.01329775620251894,
0.062772735953331,
0.018252680078148842,
0.015049559995532036,
0.008288372308015823,
-0.014106540940701962,
-0.0195841696113348,
-0.05765070766210556,
0.011965730227530003,
-0.014566484838724136,
-0.02... |
<p>Why or when does it occur in a circuit? What does it imply when you speak of a voltage drop across a resistor? (Obviously, it probably means that the current's voltage before the resistor is higher than the voltage after the resistor, but why does this drop occur?)</p> | g8696 | [
0.055272992700338364,
-0.03413211554288864,
-0.025705618783831596,
0.006800957955420017,
0.07936591655015945,
0.04526679217815399,
0.05603743717074394,
0.025039521977305412,
-0.041113417595624924,
-0.00005480699837789871,
-0.0666830986738205,
0.06693573296070099,
-0.0318247452378273,
0.042... |
<p>If electric field lines cannot terminate in empty space, in the simple example of two equal charges what happens to the line starting from one of the charges toward the other in the middle? </p> | g8697 | [
0.04834219813346863,
0.011986080557107925,
-0.01813582144677639,
-0.0069840834476053715,
0.0890674740076065,
0.04786018282175064,
-0.04912537708878517,
-0.013822890818119049,
-0.02497917413711548,
-0.032368049025535583,
-0.07232511043548584,
-0.011175361461937428,
-0.028248412534594536,
0.... |
<p>I know this probably varies quite a bit from place to place on earth. But just some rough estimates: if I were to pull power via multiple antennae tuned to a variety of different frequencies, how much "ambient" power could I draw from the atmosphere? Perhaps I'm not asking the right question, but I'm just trying to ... | g8698 | [
-0.01661941222846508,
-0.00030151952523738146,
-0.013307745568454266,
0.013818355277180672,
-0.027952566742897034,
-0.00837463978677988,
-0.02246539294719696,
0.006998182740062475,
-0.041381046175956726,
-0.007222785614430904,
0.003582627745345235,
-0.012900502420961857,
-0.03064238280057907... |
<p>Could anyone help me work through the following set of equations:</p>
<p><img src="http://i.stack.imgur.com/LVAjt.png" alt="enter image description here"></p>
<p>I found these online at</p>
<p><a href="http://marian.fsik.cvut.cz/~bodnar/PragueSum_2012/Staquet_1-2.pdf" rel="nofollow">http://marian.fsik.cvut.cz/~bo... | g8699 | [
0.057132963091135025,
0.014818085357546806,
-0.0028769448399543762,
-0.004638114012777805,
0.05116404965519905,
0.02936151809990406,
0.029781730845570564,
-0.07972375303506851,
-0.09920704364776611,
-0.02217773348093033,
-0.036187414079904556,
0.05114039033651352,
0.062337134033441544,
0.0... |
<p>I am on my way to a <a href="http://en.wikipedia.org/wiki/Shimla" rel="nofollow">shimla</a>, and as it is one of the coldest places of India.</p>
<p>Previously I lived in a warm environment of <a href="http://en.wikipedia.org/wiki/South_India" rel="nofollow">southern india</a>. What would be the correct way to live... | g8700 | [
0.08438856154680252,
-0.030666785314679146,
0.020590765401721,
0.07900737226009369,
0.009958936832845211,
-0.03332462161779404,
0.011740214191377163,
0.046909768134355545,
-0.04803093895316124,
0.021852755919098854,
0.04050973430275917,
0.003697209758684039,
0.03852732852101326,
0.02831086... |
<p>Why 21cm line observations is more helpful compared to other radiation?
Is it only because of its abundance in whole universe or anything else?</p> | g8701 | [
0.004380263388156891,
0.051150426268577576,
-0.013390173204243183,
-0.016096603125333786,
0.028789034113287926,
0.013100816868245602,
-0.0015410836786031723,
-0.01061275415122509,
0.0252335537225008,
-0.09837104380130768,
0.0776119977235794,
0.04729637876152992,
0.02786635421216488,
0.0008... |
<p>Whenever I add milk to my morning coffee I often enjoy watching the patterns which are created. These patterns have a striking resemblance to certain fractals and my question is, "Why?" Oh dear, that is never a good question, so let's try "Why shouldn't they?"</p>
<p>The obvious observations are that the water is v... | g8702 | [
0.02295611798763275,
0.08697749674320221,
0.008390620350837708,
-0.0024550773669034243,
0.06348084658384323,
0.02078927680850029,
0.03938164561986923,
0.013738607056438923,
-0.07940995693206787,
-0.09289231896400452,
0.020303810015320778,
-0.04279031231999397,
0.07297328859567642,
0.104773... |
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