question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>I get the front part, but why is the back curved too? I do not see a problem with the back being flat.</p> | g8981 | [
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<p>I'm wonder what precisely is meant by the renormalizability of the standard model. I can imagine two possibilities:</p>
<ol>
<li><p>The renormalizability of all of the interaction described by the Lagrangian before <a href="http://en.wikipedia.org/wiki/Spontaneous_symmetry_breaking" rel="nofollow">spontaneous symme... | g8982 | [
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<p>Let us choose to postulate (e.g. considering the analogy of the Hamiltonian being a generator of time evolution in classical mechanics)
$$
i\hbar \frac{d\hat{U}}{dt}=\hat{H}\hat{U}\tag{1}
$$
where $\hat{U}$ is the (unitary, linear) evolution operator and $\hat{H}$ the Hamiltonian (the most general version of which; ... | g8983 | [
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<p>Are all baryons from decuplet resonances?? Because all resonances decay by strong interaction; but omega minus baryon can't decay via strong, because any other bound state with strangeness -3 exists.
Thanks</p> | g8984 | [
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<p><a href="http://en.wikipedia.org/wiki/Hopf_algebra" rel="nofollow">Hopf algebra</a> appears in recent papers that systematize renormalization of quantum field theory (QFT). For example see <a href="http://www.google.com/search?q=connes+hopf+site%3Aarxiv.org&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-U... | g8985 | [
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<p>I am currently taking a graduate level class on lasers. The primary focus of the class is on the design and engineering aspects of lasers, e.g. resonator design. However the first portion of the class is an overview of the quantum mechanics of laser processes in semi-classical terms: transition probabilities for a 2... | g8986 | [
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<p>We tied a helium filled balloon to a counterweight and it floats aimlessly in the room. I asked if the balloon were to be outside the building (all things considered no wind same temperature) would the balloon float at the same level?</p> | g8987 | [
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<p>In other question, Ron Maimon says that he thinks string theory is the <em>physical</em> regulator. I did not know that string theory regularize divergencies.</p>
<p>So, <strong>Q1</strong>: How does string theory regularize the ultra-violet divergencies of the "low-energy" (Standard Model) fields? And <strong>Q2</... | g8988 | [
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<p><s>Proper orthochronous Loentz transform are Lorentz transforms that satisfy the conditions (sign convention of Minkowskian metric $+---$)
$$\det \Lambda=+1, \qquad \Lambda^0{}_0 \geq +1.$$
How to prove they form a subgroup of Lorentz group? All books I read only give this result, but no derivation.</s></p>
<p>Why ... | g8989 | [
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<p>How did people determine the proton number for each element from experiment in each decade of 20th century?</p> | g8990 | [
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<p>I'm starting to wonder if the description of Mass given to us when we hear physicists talk about Mass created by the Higgs field is the same type of mass we ordinarily think of, like inertial mass for example. I am wondering if they are talking about a field that stops the energy in "mass" from just flying apart and... | g229 | [
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<p>I've been wondering about microcausality for some time now (a <a href="http://physics.stackexchange.com/q/33225/955">recent question</a> of mine regarding the topic) and i'm wondering if its possible to devise an experiment to detect potential violations</p>
<p>I thought something like this: the hypothesis to test ... | g8991 | [
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<p>The following questions are based on these lectures, <a href="http://arxiv.org/abs/hep-th/9108028" rel="nofollow">http://arxiv.org/abs/hep-th/9108028</a></p>
<ul>
<li><p>I would like to know what is the relationship between the last equation on page 82 ($(L_0)_{cyl} = L_0 - \frac{c}{24}$) and the last 2 sets of equ... | g8992 | [
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<p>According to my physics book, if an electron were accelerated with 15 MeV of (kinetic?) energy and collided into a 100g thermally insulated copper block (not sure if the fact it is thermally insulated is relevant) the energy would transfer into thermal energy on the copper block and the copper block would heat up by... | g8993 | [
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<p>Why do different wavelength get impeded more or less when in different materials? Moving with the same speed, but a longer physical distance would imply that the fields oscillate less times in the material, but I don't know why a difference in the number of oscillations would impede the wave- I don't even know why t... | g298 | [
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<p>I have a question after reading a section from Goldstein's Classical Mechanics. The question deals with equation 1.43 in the text (given below):</p>
<p>$$ \tag{1.43} \sum\limits_{i} {\bf F}_i^{(a)}\cdot \delta{\bf r}_i ~=~ 0.$$</p>
<p>Just below the equation in the text, Goldstein says </p>
<blockquote>
<p>[...... | g8994 | [
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<p>I recently came across an article indicating that the half life of DNA in the most ideal situations is 521 years (<a href="http://www.nature.com/news/dna-has-a-521-year-half-life-1.11555" rel="nofollow">http://www.nature.com/news/dna-has-a-521-year-half-life-1.11555</a>). However, since human's DNA is 99.9% identica... | g8995 | [
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<p>I came across a <a href="https://courses.physics.illinois.edu/phys598PTD/fa2013/L5.pdf" rel="nofollow">lecture note</a> on weak localisation by Prof. A. J. Leggett. In this note, he wrote down his first equation as follows: $$\sigma = \lim_{\omega\rightarrow 0} \lim_{q\rightarrow 0} \frac{1}{i\omega}\frac{\delta j(q... | g8996 | [
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<p>Specifically, I would like to know the general formula, in terms of $n$ and $l$, assuming the electron is in an orbital (i.e. simultaneous eigenstate of $H$, $L^2$, and $L_z$).</p>
<p>I understand that it involves integrating an associated Laguerre polynomial, but I wasn't able to find the formula for the integral.... | g8997 | [
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<p>Assuming you place an object so heavy on a table that it breaks it, then according to newtons third law the forces must cancel out (equal magnitude and opposite direction), but if this is true, then how can the object break the table in the first place?</p> | g8998 | [
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<p>I have a question about how would seasons and the moon cycle be affected in a system where one planet orbits Sun #1, and Sun #1 orbits a second sun. Online I found this description:</p>
<blockquote>
<p>"Type II: "Close Stars" - The suns may occupy different parts of the sky, indicating that one sun orbits the oth... | g8999 | [
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<p>What is the <a href="http://en.wikipedia.org/wiki/Land%C3%A9_g-factor" rel="nofollow">Landé g factor</a>?</p>
<p>I know that it gives the relation between magnetic moment and angular moment, but i wanted to know why are those magnitudes related to each other and why is the magnetic moment operator defined proportio... | g9000 | [
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<p>I never understood the relationship between Infrared and Heat. Is IR emitted when heat is generated, is heat generated when IR is made, and how do the two relate?</p> | g9001 | [
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<p>The Hamiltonian of an atom coupled to an EM field, both described quantum mechanically is:
$$H = \frac{1}{2m}(\hat{p}-q\hat{A})^2 = \frac{\hat{p}^2}{2m} -\frac{q}{m}\hat{p}\hat{A}+\frac{q^2}{2m}\hat{A}^2$$
Under the condition of transversality ($\hat{p}$ and $\hat{A}$ are vectors). I have only seen it treated in the... | g9002 | [
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<p>Always when we want to represent the magnetic field of the earth we see a similar image:</p>
<p><img src="http://i.stack.imgur.com/BRFM7.gif" alt="enter image description here"></p>
<p>My question is, what exactly does this show? What are the blue and orange lines, what do they represent? Why are they curved like ... | g9003 | [
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<p>With multipole expansions, we speak only of monopoles, dipoles, and $2^n$-poles. Why is there nothing like a tripole? So how would something like $rsin(3 \theta)$ be expressed with a multipole expansion? Is the reason for not having terms like this in a multipole expansion that it is redundant, or is there some more... | g9004 | [
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<p>There are several ways to make charges on an object evenly distributed. For example, if the surface of the object is infinite or the object is a sphere. There is one more way which I am not sure if it is a good way: if the object is made out of an insulating material. </p>
<p>I would like to know if there are other... | g9005 | [
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<p>The photoelectric effect is the historic origin of the quantum particle description of light. From it we learn that when light is shone onto a metal single photons interact with single electrons in the metal which are ejected if the absorbed energy is larger than the binding energy of the metal. </p>
<p>The (free) ... | g9006 | [
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<p>Considering $X$ and $Y$ such that $[X,Y]=\lambda$, which is complex, and $\mu$ is another complex number, prove: $$e^{\mu(X+Y)}=e^{\mu X} e^{\mu Y} e^{-\mu^2\lambda/2}$$
My attempt (so far) is: Expand the exponent. $$\mu(X+Y)=\mu X+ \mu Y$$ and then split it. How can I introduce $\lambda$?</p>
<hr>
<p>Taylor expa... | g9007 | [
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<p>Australia's history has been littered with the problem of how to manage safety in bushfires. The local fire authority recommend consideration be given to preparing a bushfire management plan, deciding whether to stay and defend, or leave early.</p>
<p>A back- up plan is also suggested, which may include the use of ... | g9008 | [
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<p>Temperature is related to average of particles kinetic energy.</p>
<p>I would like to ask about a singular state of a particle system of a little time interval.</p>
<p>The question is:</p>
<p>If all particles were going same direction, same speed, same mass, for that while they were avoiding external forces, inte... | g9009 | [
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<p>Questions about the temperature of something in space are often very hard to pin down (<a href="http://physics.stackexchange.com/questions/10449/what-are-the-temperatures-of-objects-in-leo">example</a>), since there is radiative transfer to/from many different regions in the field of view at dramatically different t... | g9010 | [
0.03886750340461731,
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-0.0... |
<p>I have a (possibly) fundamental question, which is driving me crazy.</p>
<p><strong>Notation</strong></p>
<p>When considering the Dirac action (say reading Peskin's book), one have</p>
<p>$\int dV\;\bar{\psi}\left(\imath\not\partial-m\right)\psi,$</p>
<p>or (following Weinberg)</p>
<p>$\int dV\;\bar{\psi}\left(... | g9011 | [
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0.02039659209549427,
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... |
<p>Can someone help me or guide me how the <a href="http://en.wikipedia.org/wiki/Lens_%28optics%29" rel="nofollow">thin lens formula</a>:</p>
<p>$$\frac{1}{s_1}+\frac{1}{s_0}=\frac{1}{f}$$</p>
<p>can be proven?</p>
<p>I was trying to prove it on my own using similar triangles, only to fail.</p> | g9012 | [
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0.0025724268052726984,
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0.0... |
<p>I'm looking at a solution in my book that says $[xp_{y},x]$ commutes.<br>
Does bracket notation imply:</p>
<p>$[A,B]=AB-BA$</p>
<p>so that </p>
<p>$[xp_{y},x]=xp_{y}x-xxp_{y}$ </p>
<hr>
<p>Taking the comment from Max Graves and solving a slightly different commutation relation:</p>
<p>\begin{align}
-[yp_{x},x]... | g9013 | [
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0.03658851608633995,
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<p>I am trying to learn about optics and I am having a hard time understanding the meaning of "real" vs "virtual" image.</p>
<p>My understanding is that for a concave mirror, the image focuses on the same side as the object so it is a real image.</p>
<p>For a convex mirror, the image focuses on the opposite side of t... | g209 | [
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0.0411878265440464,
0.07494145631790161,
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<p>I have read that the mass term appearing in the electroweak Lagrangian stops it (the Lagrangian) from becoming gauge invariance. Can someone explain where and why this term is creating the problem?</p> | g9014 | [
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<p>I have a following optical system: 3 cams (left and top, which is orthogonal to the left, and right, which is parallel to the left and orthogonal to the top) and the 2 cubes in the 3D-space with following coordinate system:
<img src="http://i.stack.imgur.com/ox5l0.png" alt="optical system">
Each of the points $P_t$,... | g9015 | [
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0.07032213360071182,
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-... |
<p>Interaction of particle with Higgs field provides mass to the particles, then why still some particles are massless?</p> | g9016 | [
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<p>Can someone help me understand my mistake here?
I'm thinking of a photon travelling with momentum $p=h/\lambda$ which reflects off a solar sail of mass $m$ travelling with momentum $p_0$ in the same direction. Before the reflection, the total momentum is $p+p_0$ and after it is $-p'+p_1$ where $p'$ is the magnitude ... | g9017 | [
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<p>In the photoelectric effect the electrons are supposed to be removed from the plate if light of appropriate wavelength hits the plate. </p>
<p>If electrons are removed, the plate should get ionized (positively). If this is true, does the plate change its properties?</p> | g9018 | [
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0.01242... |
<p>The cross product $\vec{a} \times \vec{b}$ can be written as the determinant of the matrix:</p>
<p>$$\left| \begin{matrix}
\vec{i} & \vec{j} & \vec{k} \\
a_i & a_j & a_k \\
b_i & b_j & b_k
\end{matrix}\right|$$</p>
<p>Is there any physical significance to this matrix, or is it just some mat... | g9019 | [
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0.025633325800299644,
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0.0... |
<p>The definition of current is flow of electric charge. But recently I have heard that the electrons cannot move, that they just transmit energy to the other electrons and so on.</p> | g9020 | [
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0.0401008203625679,
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... |
<p>I've tried to find an answer for this but couldn't find one. Whats the problem with matter being created with little or no antimatter</p> | g9021 | [
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0.03287362... |
<ul>
<li>Are photons units of energy?</li>
<li>What is the relation between EM force, EM energy and the photon?</li>
<li>Do EM forces carry energy, do they carry the photon (as unit of energy)?</li>
</ul> | g9022 | [
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... |
<p>[This question was inspired by a identical question asked on a other forum]</p>
<p>Note that we may morally include general relativity in the gauge theories. </p>
<p>We may have several (some are deliberately contradictory) remarks : </p>
<p>1) Gauge invariance is only a mathematical redundancy, which is unphysic... | g9023 | [
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0.019313910976052284,
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0.012661345303058624,
0.048145... |
<p>I know that on the smallest scales, general relativity predicts that space-time is flat. But I've also read that space-time can be described as a sort of "quantum foam" for distances smaller than the Planck length. Isn't this something of a contradiction (one more way in which quantum mechanics and general relativit... | g9024 | [
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<p>In the book (Supergravity - Daniel Z.Freedman & Antoine Van Proeyen - Cambridge), there are (Chapters 16-17) a presentation of pure supergravity or supergravity with matter, from a SuperConformal approach.</p>
<p>The "simplest" link, is to begin with a Superconformal gauge multiplet coupled to a chiral multiple... | g9025 | [
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0.029... |
<p>If we look at the Einstein vacuum equations, that is without matter (there is the possibility or curvature without matter), for instance we may consider gravitational waves. The question is: Is there some link between the Riemann curvature tensor, and/or the Weyl tensor, and some gravitational "physical" quantities ... | g9026 | [
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0.0046947794035077095,
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0.04842602089047432,
0.01... |
<p>I came across some notation that I can't quite understand:</p>
<p>$$ \hat{r}\hat{r} - \textbf{1}_3$$</p>
<p>where $\textbf{1}_3$ is the 3$\times$3 identity matrix, $\hat{r}$ is a unit 1$\times$3 vector, and the result is supposed to be a 3$\times$3 matrix. What is the operation (implied) in the juxtaposition $\hat... | g9027 | [
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0.03613875433802605,
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0.001878592069260776,
-... |
<p>Is there an intuitive geometrical picture behind the <a href="http://en.wikipedia.org/wiki/Dirac_equation">Dirac equation</a>, and the gamma matrices that it uses? I know the <a href="http://en.wikipedia.org/wiki/Geometric_algebra">geometric algebra</a> is a Clifford algebra. Can the properties of geometric algebra,... | g9028 | [
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0.01822401024401188,
0.039088472723960876,
-0.... |
<p>Wikipedia has this to say about the discovery of the aberration of light:</p>
<blockquote>
<p>In 1728, while unsuccessfully attempting to measure the parallax of Eltanin, James Bradley discovered the aberration of light resulting from the movement of the Earth. Bradley's discovery confirmed Copernicus' theory tha... | g9029 | [
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0.07701937854290009,
0.0417... |
<blockquote>
<p>"Optical lattice requires a very low temperature scale to enter magnetism regime." </p>
</blockquote>
<p><em>Why is that?</em></p>
<p>What I know:</p>
<ol>
<li>optical lattice systems suppress kinetic energy (hopping parameter: $t$ small);</li>
<li>superexchange is a second order process;</li>
<li>... | g9030 | [
0.03307545185089111,
0.08656501024961472,
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0.011931865476071835,
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-0.012510275468230247,
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0.06613530218601227,
-0.000580759602598846,
-0... |
<p>Please consider the publication</p>
<blockquote>
<p><a href="http://arxiv.org/abs/1104.0699" rel="nofollow">Invariant Mass Distribution of Jet Pairs Produced in Association with a W boson in $p\bar{p}$ Collisions at $\sqrt{s} = 1.96$ TeV</a></p>
</blockquote>
<p>by the <a href="http://en.wikipedia.org/wiki/Colli... | g879 | [
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-0.... |
<p>Very basic question: When to use $s=vt$, $s=\frac{1}{2}vt$, $s=at$ and $s=\frac{a}{t^2}$?
What was the difference between those?</p> | g9031 | [
0.04106782004237175,
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0.026982109993696213,
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0.03349952772259712,
0.04847234487533569,
0.02... |
<p>In the classic (and morbid) <em>Schrodinger's Cat</em> thought experiment, we imagine putting a cat into a box with a vial of poison which will be triggered by a quantum detectors. We set up a radioactive nucleus or an excited ion, and set up a detector to look for radiation resulting from radioactive decay or drop ... | g9032 | [
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0.009714607149362564,
0.032742924988269806,
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0.05757792294025421,
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-0.056019801646471024,
-0.001309433951973915,
0.024828631430864334,
0.045811884105205536,
... |
<p>The Coleman-Mandula theorem states that under certain seemingly-mild assumptions on the properties of the S matrix (roughly: one particle states are left invariant and the amplitudes are analytic in external momenta) the largest possible Lie algebra of symmetries of a (non-trivial) S matrix is given by Poincaré time... | g9033 | [
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0.020213905721902847,
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0.026993466541171074,
-0.04682719707489014,
-0.02414744347333908,
-0.015781424939632416,
... |
<p>Some background info on what an evaporator is:
It is a system of metal pans set over a heat source. Sap constantly enters the first pan controlled by a float valve to keep a constant depth. The pans have channels which are open to each other at alternating ends, so that the sap flows back and forth in a serpentine... | g9034 | [
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0.008382577449083328,
0.006591093726456165,
0.015126416459679604,
0.030542640015482903,
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0.012776858173310757,
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-0.06347338110208511,
0.017678994685411453,
0.06665103882551193,
0.... |
<p>Apologies if too specific.</p>
<p>Watched a documentary <a href="http://natgeotv.com/nl/mega-factories-2/videos/bugatti-veyron" rel="nofollow">National Geographic Megafactories Bugatti Veyron</a></p>
<p>I told an colleague (engineer) about the need to warm the car up and then unleash it on the long stretch to be a... | g9035 | [
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0.00291784037835896,
0.007200951222330332,
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0.0564563013613224,
-0.003... |
<p>The Metropolis-Hastings algorithm is an efficient way of simulating classical ensembles using the Monte Carlo method. Is there a generalization of this algorithm to quantum systems? What I DON'T have in mind is Wick rotation to a classical Euclidean system.</p> | g9036 | [
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<p>I have readings of colors from a spectrophotometer that records across the human visible color spectrum 390nm to 790nm intervals. I'd like to convert this into any color space, could be CIE XYZ, HSL, CIE-Lab, etc. Any color temperature is okay.</p> | g9037 | [
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... |
<p>A sonar continuously emits x(t), a general but known waveform that is reflected by a target and received by the sonar. Both the sonar and the target move in the 3-dimensional space in a general but known manner. That is the positions of the sonar and the target are known. What would be the relation between and t... | g9038 | [
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0.07280310243368149,
-... |
<p>How exactly can you measure the atomic radius of a noble gas such as Neon or Helium accurately? Would liquefaction help? I also heard that the aforementioned gases are the only common elements which have not been measured accurately as they don't bond with anything.</p> | g9039 | [
0.004958626348525286,
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0.023385239765048027,
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0.03301879018545151,
0.029661482200026512,
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0.07534438371658325,
0.013037877157330513,
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0.019390633329749107,
0.02904413640499115,
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0.0... |
<p>I have been recently reading a paper on dust removal and I have a few basic questions regarding it. </p>
<p>First off, I am citing this paper - "<a href="http://www.slideshare.net/sauravdhar1/electrostatic-dust-removal" rel="nofollow">Dust removal system with static electricity</a>" </p>
<p>Basically, an electric... | g9040 | [
0.07353629916906357,
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0.015585070475935936,
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0.054960619658231735,
0.01632562279701233,
0.01... |
<p>In doing second order time-independent perturbation theory in non-relativistic quantum mechanics one has to calculate the overlap between states </p>
<p>$$E^{(2)}_n ~=~ \sum_{m \neq n}\frac{|\langle m | H' | n \rangle|^2}{E_n^{(0)}-E_m^{(0)}}$$ </p>
<p>(where $E^{(k)}_n$ represents the kth order correction to the ... | g9041 | [
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0.013968592509627342,
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0.016040872782468796,
0.040836136788129807,
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<p>What are some important examples of paradoxes in physics which are still currently unresolved?</p> | g9042 | [
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<p>I am taking an introductory lab course in which we've done an experiment on the physical pendulum.</p>
<p><img src="http://i.stack.imgur.com/PkD3g.jpg" alt="drawing of physical pendulum"></p>
<p>We've seen that for small oscillations, the period is </p>
<p>$$T=2\pi\sqrt{\dfrac{I_S}{Mgd_{cm}}}\tag{1}$$</p>
<p>whe... | g9043 | [
0.0826532319188118,
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<p>The Chinook Helicopter has 2 rotors to counteract the torque generated by spinning the blade. </p>
<p>Theoretically, could you use a smaller "back" rotor that is farther away from the main rotor to achieve the same result, ie no twisting?</p> | g9044 | [
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<p>let be the problem </p>
<p>$$ -\frac{d^{2}}{dx^{2}}y(x)+f(x)y(x)=E_{n}y(x)$$</p>
<p>however we have a problem, we do not know the potential but its inverse</p>
<p>$$ f^{-1}(x)=g(x) $$</p>
<p>we know $ g(x) $ but not $ f(x) $ what happense then since</p>
<p>a) the function $ f(x) $ may be multi-valued</p>
<p>b)... | g9045 | [
-0.03488927334547043,
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<p>After September,I will be a sophomore.During the vocation, I am learning optics by myself. And I learn it by reading Ajoy Ghatak's <strong><em>Optics</em></strong>(<a href="http://books.google.de/books/about/Optics.html?id=jStDc2LmU5IC&redir_esc=y" rel="nofollow">http://books.google.de/books/about/Optics.html?id... | g299 | [
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<p>In Dirac's The Principle of Quantum Mechanics he makes the general assumption that "if the measurement of the observable $\xi$ for the system in the state corresponding to $|x\rangle$ is made a large number of times, the average of all the results obtained will be $\langle x|\xi|x\rangle$, provided $|x\rangle$ is no... | g9046 | [
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<p>What's the evidence, if any, for some local concentration(s) of dark matter in some region(s) smaller than a galaxy?</p>
<p>Galactic-sized--or larger--gravitating halos seem to get all the attention. I'm just wondering about the status of smaller halos/concentrations; if any.</p> | g9047 | [
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<p>Suppose there is one rod and a force F is applied in two cases:<br>
<strong>Case 1:</strong> exactly at the middle on center of mass<br>
<strong>Case 2:</strong> at one end of rod
<img src="http://i.stack.imgur.com/3w7Mt.png" alt="enter image description here"></p>
<p>In which case would the center of mass of rod b... | g789 | [
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<p>In nonrelativistic quantum mechanics the state of a system is characterized by a vector of a Hilbert space. </p>
<p>To characterize a state we need a complete set of commuting observables, and once we have that we label the state using some set of quantum numbers.</p>
<p>Now, in field theory I have been told that ... | g9048 | [
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<p>I ask this because it occurred to me that the inertial property of mass only actually arises in the context of forces (such as the EM force) as a resistance to their accelerating effect. Inertia plays no role in gravity (which as per General Relativity is not really a force, though does resemble a force in certain r... | g9049 | [
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0.03915721923112869,
0.05616540461778641,
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<p>Does anyone know where I could find and purchase the book "Statistical Mechanics" by R. Pathria, in 1st edition (the 2nd and the 3rd are readily available, but I really need the first). I believe the first edition was published in 1972. I have searched high and low for it, but can't seem to find it even on Amazon.</... | g9050 | [
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0.03900015726685524,
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<p>When presenting the stress tensor (say in a non-relativistic context), it is shown to be a tensor in the sense that it is a linear vector transformation: it operates on a vector $n$ (the normal to a surface), and returns a vector $t_n$ which is the traction vector. It is then shown that conservation of angular momen... | g9051 | [
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<p>I am working with a rotary damper (paddle hanging off a shaft attached to the bottom of a rotary table and into a vat of fluid). I know the viscosity of the current Newtonian fluid, I know the flow is laminar, and I know the Q-factor of the damping in this fluid. I need to find a way to get a relation between them t... | g9052 | [
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<p>Does a quark, for example a up-quark has a fixed energy? The <a href="https://commons.m.wikimedia.org/wiki/File:Standard_Model_of_Elementary_Particles.svg" rel="nofollow">standard model</a> gives well defined masses in MeV which is energy too.</p> | g9053 | [
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<p>This is probably a simple question: I see this claims in many books, but I can't figure a reason why this is true. </p>
<p>So my question is why this claim is true:
"If we know that the system is in the ground state, then the temperature is zero".
So I wonder how this follows from the statistical definition of temp... | g9054 | [
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<p>If you were able to ride along a photon and a second photon passed you in the opposite direction, would what you observe be twice the speed of light?
And would that change what you would see of the second source of light?</p> | g109 | [
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<p>If a pipe extended from just above the ocean floor to outside the atmosphere, would water be sucked up it by the vacuum beyond the atmosphere? If a hole was made in the pipe, above sea level, how would that affect the flow of water? Would it stop it completely?</p> | g9055 | [
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<p>The title explains it all. Do objects suspended in ice sink over time? You may remember the story of World War 2 planes that were found 260 ft under the ice which would be anachronistic with seasonal ice layering alone. I'm trying to establish other possible mechanisms. I know that ice flows up and down in glaciers,... | g9056 | [
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<p>I was doing some physics homework involving direct current circuits and resistors in series, and I started to question the accuracy of the following property of resistors in series, namely that the voltage across the battery is equal to voltage drop across the resistors. But what about the resistance in the wire its... | g9057 | [
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<p>I need to get rid of water excess in my vacuum chamber, and for that there is the procedure of baking. In order to do that there are several things that one needs to consider, the power, heat load, type of heat tape to use etc. Since I've never done this before, I hope that some of you could share their advice on th... | g9058 | [
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<p>Which of the following were the intentions of M&M?</p>
<ol>
<li>to disprove the existence of aether.</li>
<li>to show that the aether has no effect on matter and energy and therefore is as good as non-existent.</li>
</ol>
<p>Feel free to insert more reasons/intentions.</p>
<p>Which of the following were the c... | g883 | [
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0.052513... |
<p>This question is kind of inspired in this one:</p>
<p><a href="http://physics.stackexchange.com/questions/4359/diffm-as-a-gauge-group-and-local-observables-in-theories-with-gravity">Diff(M) as a gauge group and local observables in theories with gravity</a></p>
<p>The conundrum i'm trying to understand is how is d... | g9059 | [
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<p>What is the full text (and possibly the source) of the summary of the 3 laws of thermodynamics that goes something along the lines of "Can't break even, can't win and can't even stop playing the game"?</p> | g9060 | [
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<p>the values $ \zeta (-1)= -1/12 $ and $ \zeta (-3)= 1/120 $ give accurate results for casimir and to evaluate the dimension in bosonic string theory</p>
<p>so is there a physcial JUSTIFICATION to justify that in phsyics (not mahthematics) every time we see a divergent series like $ 1+2^{s}+3^{s}+......... $</p>
<p>... | g9061 | [
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0... |
<p>In theory do wormholes have a side to their path through space?</p>
<p>What is there at a point in line with the entry and exit, would anything look different at that point in space?</p>
<p>Could a space ant get in through the side of a wormhole?</p>
<p>Update: The wormhole would be an einstein-rosen bridge from ... | g9062 | [
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<p>Suppose we have a chemical reaction of the form</p>
<p>$$n_1 A_1 + \cdots + n_r A_r \leftrightarrow m_1 B_1 + \cdots + m_s B_s$$</p>
<p>where $A_i$ and $B_i$ are molecules, and the $n_i$ and $m_i$ are the integer coefficients of the equation. Let $[X]$ be the concentration of $X$, that is, the amount of moles per ... | g9063 | [
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<p>First question: Does anyone know of any low permeability, low coercivity magnetic compounds? A physics professor told me that I should dig deep in the literature, but that I should look for materials with a Curie temperature ~100K and that I should avoid cubic structures. I haven't had much luck finding anything tho... | g9064 | [
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-... |
<blockquote>
<p>A rock is thrown towards a window, and hits it. The window does not break and the rock reverses its direction and falls under the window.</p>
</blockquote>
<p>My question is, under this circumstance since the rock reversed it's direction of movement I want to say that the force exerted by the window ... | g9065 | [
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0.002842453308403492,
0.056950461119413376,
0.001779075711965561,
0... |
<p>It is quite easy to compute the first derivative of vapor pressure with respect to temperature from a cubic equation of state at least at the critical point since there is a continuity with the critical isochore. But, is there any way to establish the second derivative or at least its value at the critical point? Fo... | g9066 | [
0.03402800112962723,
-0.04948495700955391,
-0.0009538893355056643,
0.035227805376052856,
0.036240171641111374,
-0.023376060649752617,
-0.017065446823835373,
-0.0016506001120433211,
-0.007578253746032715,
0.024007214233279228,
-0.024402331560850143,
-0.030813392251729965,
0.02147664874792099,... |
<p>When looking at the pressure-temperature diagram along the critical isochore (up to quite high reduced temperatures) a very linear trend can be observed. From a theoretical point of view, is the critical isochore linear or just almost linear ?</p> | g9067 | [
0.02622739039361477,
-0.03163888677954674,
-0.009668177925050259,
0.04526155814528465,
0.010044927708804607,
0.03501706197857857,
0.009119485504925251,
-0.009129461832344532,
-0.050933729857206345,
0.040069591253995895,
-0.022078389301896095,
-0.006143641192466021,
0.021203719079494476,
-0... |
<p>I've been looking for problems to practice on this topic and found a problem asking to use the Maxwell-Boltzmann distribution function to calculate the fraction of Argon gas molecules with a speed of 305 m/s at 500 K. I thought the distribution function could only be used to find the fraction of molecules moving bet... | g9068 | [
0.017723575234413147,
-0.01899784803390503,
0.01412216853350401,
0.0006612144643440843,
0.02705090306699276,
-0.04592322185635567,
0.01971421018242836,
0.014718457125127316,
-0.05551936849951744,
-0.0014100632397457957,
0.04969257488846779,
0.007530077360570431,
0.053207412362098694,
-0.00... |
<blockquote>
<p>In an artificial satellite, a space traveler tries to fill a pen by
dipping it in ink. The amount of ink filled in the pen as compared to
the amount of ink filled on the Earth's surface will be:</p>
<p>A) less</p>
<p>B) more</p>
<p>C) same</p>
<p>D) nil</p>
</blockquote>
<hr>
... | g9069 | [
0.054225433617830276,
0.11200964450836182,
-0.0023300014436244965,
-0.024661457166075706,
0.029659105464816093,
0.04667286574840546,
0.02826637402176857,
-0.025707010179758072,
-0.08028196543455124,
-0.014729306101799011,
0.016130173578858376,
0.04887634143233299,
0.0691051110625267,
0.036... |
<p>What is highest known value been achieved for single atom (artificial atom) cooperativity ($C=\frac{g^2}{\kappa\gamma}$) factor in the strong coupling regime for Cavity and Curciut QED? </p> | g9070 | [
-0.007752403616905212,
-0.01356979925185442,
-0.01462587434798479,
-0.011099756695330143,
0.03353918343782425,
0.06510961055755615,
-0.028666650876402855,
0.027082698419690132,
-0.006317926570773125,
0.019662046805024147,
-0.008446061983704567,
0.051334626972675323,
0.01169500406831503,
-0... |
<p>I am referring to this recent "news feature" by Zeeya Merali from Nature magazine <a href="http://www.nature.com/uidfinder/10.1038/478302a">www.nature.com/uidfinder/10.1038/478302a</a>. Here is the specific quote:</p>
<p>"To make matters worse, some of the testable predictions from string theory look a tad bizarre... | g9071 | [
0.05480768904089928,
0.03407873213291168,
0.002877764869481325,
-0.0025159239303320646,
0.058578971773386,
0.002148747444152832,
-0.031089695170521736,
0.016864126548171043,
0.0017471408937126398,
-0.04202866554260254,
-0.018987491726875305,
-0.01998039521276951,
0.007604093756526709,
-0.0... |
<p>I am studying the piezoelectricity in Gallium arsenide (GaAs), $[110]$ and $[\bar{1}10]$ oriented. Piezoelectricity is usually described microscopically by a 3 index tensor, $d_{ijk}$ where
i,j and k equal to x,y and z.</p>
<p>$[110]$ and $[\bar{1}10]$ have different piezoelectric behaviour but they are linked by a... | g9072 | [
-0.014798243530094624,
0.06460076570510864,
-0.013121549040079117,
-0.027822427451610565,
0.06988894939422607,
-0.06321196258068085,
0.09770441055297852,
0.009175948798656464,
0.06763862818479538,
0.013733855448663235,
-0.07241177558898926,
0.04363454505801201,
0.00997476652264595,
-0.0853... |
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