question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
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<p>why in higgs field drag cause mass?
drag is force in general not mass
<a href="http://www.fnal.gov/pub/inquiring/questions/higgs_boson.html" rel="nofollow">Higgs field- Inquiring Minds - Questions About Physics</a>
how drag of higgs field cause mass?</p> | g15927 | [
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<p>I'm looking at a problem involving a simplified rollercoaster with only 3 cars (connected with weightless rods) for which the friction and distance from the carts to the rails can be ignored. The part I was thinking about is the following: at a certain moment cart 2 is situated on top of an arc as I have drawn here.... | g15928 | [
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<p>Wikipedia states in QFT all fields generally exist in superpostion. Is this correct? So my question is in quantum field theory, are the fields in quantum field theory existing persistently in superposition? or are there times they don't? If they do, would it prove Many worlds interpretation of quantum mechanics?</p> | g811 | [
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<p>I've read somewhere that disconnected diagrams do not contribute to the S-matrix. I don't see why this is the case. I do know why vacuum bubbles do not contribute: given a generating functional for a scalar field the n-point correlation function follows from:
$$
G(x_1, \dots,x_n) = \frac{1}{i^n}\frac{\delta}{\delta ... | g15929 | [
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<p>The Earth orbits around the Sun because it has angular momentum. If we stopped the Earth in orbit and then let it fall straight towards the Sun, how long would it take to reach the Sun in seconds?</p>
<p>Details and assumptions</p>
<pre><code>The mass of the sun is 2*10^30 Kg.
The mass of the earth is 6*10^24 Kg.
... | g15930 | [
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<p>There are two things light and dark. Is there any system where the thing is neutral, i.e we see light and dark together in same ratio. Is it possible practically/theoretically ?</p> | g15931 | [
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<p>I want to start reading Griffiths <a href="http://en.wikipedia.org/wiki/Classical_electromagnetism" rel="nofollow">electrodynamics</a> during my holidays. But I am not sure of the math I need to know to start reading and understand the text thoroughly. So any advice would be thoroughly appreciated.</p> | g490 | [
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<p>The equations of motion of a <a href="http://en.wikipedia.org/wiki/Foucault_pendulum" rel="nofollow">Foucault pendulum</a> is given by: </p>
<p>$$\ddot{x} = 2\omega \sin\lambda \dot{y} - \frac{g}{L}x$$
$$\ddot{y} = -2\omega \sin\lambda \dot{x} - \frac{g}{L}y$$</p>
<p>where $\omega$ is the rotational frequency of t... | g15932 | [
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<p>In pair production, we get a positron and electron from a photon. The photon should have 1.02Mev energy to carry out this process</p>
<p>When the energy of positron and electron is added, we get the energy of photon. </p>
<p>hf = E- + E+ = (m0c2 + K.E-) + (m0c2 + K.E+) = K.E- + K.E+ + 2m0c2</p>
<p>mc2 for electro... | g15933 | [
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<p>Suppose an aircraft is moving at a certain fixed altitude above the ground. It follows a path defined by latitude and longitude. Now if we want to define the position of an aircraft at any point in the air, three variables are required for example X for latitude, Y for longitude and Z for the altitude. Suppose an ai... | g15934 | [
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<p>In my opinion, "grounded" means having the same potential as the potential at infinity, which is usually set to zero. Now if we consider a conductor inside a uniform electric field, what is the meaning of a conductor being <a href="http://en.wikipedia.org/wiki/Ground_%28electricity%29" rel="nofollow">"grounded"</a>?... | g15935 | [
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<p>I have been reading a online-book/blog/material on Quantum Mechanics, when I encountered a notation on a page and I have no idea what it means. See if you can help.</p>
<p><a href="http://thisquantumworld.com/wp/the-mystique-of-quantum-mechanics/indistinguishable-particles/" rel="nofollow">Here</a>'s the link and f... | g15936 | [
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<p><img src="http://i.stack.imgur.com/QkMLC.png" alt="enter image description here"></p>
<p>My problem is finding the equation of motion for the block. Using Newton's Second Law, I did:
$$4g-T-R=4\frac{dw}{dt}$$
But the mark scheme says:
$$4g-T-R=0.2*4\frac{dw}{dt}$$
And I don't understand why the radius has anything ... | g15937 | [
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<p>Imagine an object moving in a straight line in space, perhaps shaped like a yo-yo (to make rotational effects negligible). Suddenly a constant force is exerted at right angles to the direction of motion, such that the object is now deflected into a circular path.</p>
<p>What is the energy required (or work done) to... | g15938 | [
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<p>If I place two positive charges of different magnitudes on the x-axis (one at the origin, one at the some position x), as the two charges repel each other are the forces that they impart on each other the same? Why?</p>
<p>Edit: I'm working on a problem that has that situation, and the problem asks for me to find t... | g15939 | [
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<p>CCDs are getting pretty good these days, but all systems are subject to noise. A typical value for a CCD seems to be 20 electrons RMS per pixel. <a href="http://qsimaging.com/ccd_noise.html">This article from qsimaging.com</a> says</p>
<blockquote>
<p>CCD Read Noise is a fundamental trait of CCDs, from the one ... | g15940 | [
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<p>In the first order formulation of general relativity, the frame field $e_{\mu}^a$ and $\mathrm{SO}(3,1)$ spin connection $\omega_{\mu c}^b$ are independent variables. In the Hamiltonian formulation of this theory, one finds that there are second-class constraints. </p>
<p>According to Dirac, the way to deal with th... | g15941 | [
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<p>I read several textbooks of QFT and found that there are two kinds of definition of $S$ operator (or <a href="http://en.wikipedia.org/wiki/S-matrix" rel="nofollow">S matrix</a>).</p>
<ul>
<li><p>First kind:</p>
<p>Define $\hat{S}$ is map from out space to in space
$$\hat{S}\left|\beta,\text{out}\right\rangle：=\lef... | g15942 | [
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<p>In the quantization of electromagnetic field the physical states $|\psi\rangle$ are found to obey the following relation:</p>
<p>$[a^{(0)}(k)-a^{(3)}(k)]|\psi\rangle=0$</p>
<p>It is explained as the physical states are admixtures of longitudinal and timelike photons. What does longitudinal and timelike photons phy... | g15943 | [
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<p>diodes are made of silicon, which have been enriched in phosphorus and boron to create the PN junction. Since the electrons are always going in the same direction, from N to P in the junction, I was wondering whether a diode had a given lifetime after which there is no electrons anymore to move in the PN junction (n... | g15944 | [
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<p>When trying to intensify a beam of light by refracting it through a lens, (as in a lighthouse fresnel system or similar railroad style switch lamp from years past), is the beam intensity increased by moving the lens closer to the beam? That is, refracting it as close as possible to the light source? Or of a similar ... | g15945 | [
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<p>First of all, sorry if my question is dumb, I have very little understanding of physics. Also, English is not my native language.</p>
<p>If two gases, initially with different pressures, are mixed in a closed vessel, do they (the mixture being treated as a single gas) generally reach uniform pressure?</p>
<p>Now, ... | g15946 | [
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<p>I am considering spinors in a space-time which is $\mathbb{R}^{1,3}\times{}B$ being $B$ a compact manifold of $D$ dimensions. </p>
<p>I know that in ordinary 4 dimensional space-time spinors are representations of $O(1,3)$. Now, in my case, are spinors expected to be reps of $O(1,3+D)$?</p>
<p>Does the compactness... | g15947 | [
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<p>I am trying to understand Herbert Goldstein's introduction to 4-vectors. He describes a 1-D curve in spacetime $ P_(\lambda) $ then he says a 4 vector is defined as the tangent vector to this curve $$ v = \biggr ( \frac {dP} {d\lambda}\biggr)_{\lambda =0} $$ </p>
<p>why is $ \lambda $=0? what does that have to ... | g15948 | [
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<p>If I have an arbitrary (closed?) conducting surface and a nearby charge density, is there a simple numeric way of computing the induced charge distribution on the surface?</p> | g15949 | [
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<p>Ok so I have this problem where I have a system of two lenses. All I know is that the distance between the object and the first lens is 30cm, the distance between the object and the final image is 70cm, the focal distance of the first lens is 20 and the total magnification is -0.666. I need to find the focal dista... | g15950 | [
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<p>I read the term field gradient in most of the article about magnetic field. I search it online but most of the explanation is about the math. I wonder in physics, what the gradient field really mean? To my understanding, I think a gradient field means the magnitude of field is position dependent, is that right? I re... | g15951 | [
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<p>I have a question regarding a homework problem for my quantum field theory assignment.</p>
<p>For the purposes of the question, we can just assume the Lagrangian is that of a real scalar field:
$$\mathcal{L}=\frac{1}{2}\left( \partial _\mu \phi\right) ^2-\frac{1}{2}m^2\phi ^2$$.</p>
<p>The first part of the proble... | g15952 | [
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<p>As many books tells that the magnetic field can be illustrated by a bunch of field lines, which start from one pole and end up at the other. If I have a strong uniform field with field lines along horizontal direction. What happen if I place a small magnet somewhere away from the field line, will it change the direc... | g15953 | [
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<p>I want to design and build a small semi-rigid airship/dirigible. It will be controlled with RC so I will install motors, arduino, battery etc. Filled with helium.</p>
<p>Weight of the equipment is about 2kg and weight of the dirigible itself (envelope, light internal scaffold...) is unknown since I don't know how b... | g15954 | [
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<p>Why does the stale smell disappears in a crowded room if you cool it via air-condition ? What's the physics ?</p> | g15955 | [
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0.04446985200047493,
0.00114945019595325,
0.016358882188796997,
0.038718... |
<p>At some point in the history of quantum mechanics, it was accepted that a single particle is described by a wavefunction which is a function of the position of the particle $\mathbf{r}$, denoted:
$$\psi(\mathbf{r})\,.$$
At some (possibly later) point it was also accepted that <em>two</em> particles are described by ... | g15956 | [
0.03255992382764816,
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0.041915569454431534,
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<p>I know that when an object collides onto the helmet, it causes an inelastic collision so that energy is absorbed by the structure of the helmet, so what exactly does the softer inner layer do? Does it prevent the energy from being transferred into the head?</p> | g15957 | [
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<p>I'm looking for an intuitive understanding of the factor $$e^{-E/kT}$$ so often discussed. If we interpret this as a kind of probability distribution of phase space, so that $$\rho(E) = \frac{e^{-E/kT}}{\int_{0}^{\infty}e^{-E'/kT}dE'}$$ then what, precisely, does this probability correspond to? Is its physical signi... | g817 | [
-0.00419112853705883,
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<p>I am trying to determine the mathematical difference between mean free path and root-mean-square free path. For an ideal gas, the relaxation time is $$\tau=\frac{1}{\sqrt2 \pi nd^2 \bar v}$$ and the mean free path is $$\Lambda=\tau \bar v $$ so the velocities cancel. When I am calculating the RMS free path, I am ass... | g15958 | [
0.024925684556365013,
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<p>Is spacetime a function of itself, objects within it, or both? I am struggling to understand just what is spacetime without objects in it (or theoretical reference points) and thus no frame of reference except itself. It seems that spacetime without objects (on its own) is more of an abstraction and would be hard if... | g15959 | [
-0.003080912632867694,
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<p>Presently I am reading about "Introduction to dynamical process theory and simulation" which uses the notion of <a href="http://en.wikipedia.org/wiki/Master_equation" rel="nofollow">Master Equations</a> to solve Markov process.
I am very new to this. Can someone provide me the references so that I can learn about m... | g15960 | [
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<p>I watched a TED talk by the scientist Aaron D. O'Connell about actually seeing quantum superposition. The link to the talk is :-</p>
<p><a href="http://www.ted.com/talks/aaron_o_connell_making_sense_of_a_visible_quantum_object" rel="nofollow">http://www.ted.com/talks/aaron_o_connell_making_sense_of_a_visible_quantu... | g15961 | [
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<p>If gravity at a place increases or decreases, does it affect the sound wave propagating through that place. If for certain place gravity increases on earth will there be change in direction or wavelength of the sound wave. </p> | g491 | [
0.026947293430566788,
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<p>Do gravitational waves have a certain speed? Is it the speed of light or infinite, or am I misunderstanding what a gravitational wave is? I think it is a ripple in spacetime caused by interactions between objects, but i could be wrong.</p> | g4 | [
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<p>Suppose I have a variable $x$ and a constant $a$, each having the dimension of length. That is $[x]=[a]=[L]$ where square brackets denote the dimension of the physical quantity contained within them. </p>
<p>Now, we wish to take the derivative of $u = log (\frac{x^2}{a^2})-log (\frac{a^2}{x^2})$. Here, we have take... | g15962 | [
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<p>A beam of light of wavelength $\lambda$ and width $W$ needs to be focused at a distance $D$ to a spot not bigger than $w_S$, which stands for 'width of sail'.</p>
<p>Now, the diffraction limit says it clearly that a coherent beam will diverge at a rate no less than $\frac{\lambda}{W}$, and that the minimal target s... | g15963 | [
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<p>I'm attempting to siphon boiling water into another container for a school project. I have researched the physics of a siphon but I can't seem to make my boiling water siphon out of its initial pot.
Does the pot need to be airtight to increase the pressure? Is 3/8" tubing too thick for this to work?</p> | g15964 | [
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<p>In what circumstances can negative energy cancel out energy? If a positron and electron are created they cancel out as one of them has negative energy.
Are there any other ways that negative energy and energy cancel out? Is negative energy everywhere around us or somewhere else?</p> | g15965 | [
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<p>I know that conventionally the unit of $E$ in $E=mc^2$ is taken as joules when mass is in $\mathrm{kg}$. But I am doing some calculations of my own with different units of energy ($\mathrm{keV}$,$\mathrm{MeV}$ etc.). So my question is whether we have to convert $\mathrm{keV}$ or $\mathrm{MeV}$ to joules in order to ... | g15966 | [
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<p>I was told recently that "it is well known that processes like $WW\to t\bar{t}$ ($t$ being a top, or any massive fermion) grows linearly with the energy in the absence of an Higgs boson." Does anyone know of a reference? The only ones I can find regarding the growth of $WW \to f\bar{f}$ are about the old argument fo... | g15967 | [
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<p>For what longest possible time it was possible to hold light in a closed volume with mirrored walls? </p>
<p>I would be most interested for results with empty volume but results with solid-state volume may be also interesting.</p> | g1035 | [
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<p>I'm a freshman undergraduate. I've got my sight on mathematical physics. I love math but I don't have the talent nor the inclination for purely abstract mathematics. I also love physics.</p>
<p>The only math for physics I know is cook-book calculus 1. (I have deep interest in mathematics, I have finished an intro t... | g15968 | [
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<p>Consider a supersymmetric theory with 3 chiral superfields, $X, \Phi_1$ and $\Phi_2,$ with canonical Kahler potential and superpotential
$$ W= \frac12 h_1 X\Phi_1^2 +\frac12 h_2 \Phi_2\Phi_1^2 + fX.$$
One can show, by doing calculations, that
(i) supersymmetry is spontaneously broken, but
(ii) one-loop corrections d... | g15969 | [
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<p>According to <a href="http://rarenergia.com.br/" rel="nofollow">this site</a>, it seems so. </p>
<p>Power generator powered exclusively by gravity:</p>
<p><img src="http://i.stack.imgur.com/scWcR.jpg" alt="enter image description here">
<img src="http://i.stack.imgur.com/L7ObN.jpg" alt="enter image description her... | g15970 | [
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<p>I try to calculate the age of the universe with the FLRW model:
$$ H(a) = H_0 \sqrt{\Omega_{\mathrm{R},0} \left(\frac{a_0}{a}\right)^4 + \Omega_{\mathrm{M},0} \left(\frac{a_0}{a}\right)^3 + (1-\Omega_{\mathrm{T},0}) \left(\frac{a_0}{a}\right)^2 + \Omega_{\Lambda,0}}. $$</p>
<p>I set $\Omega_{\mathrm{M},0} = 0.317$ ... | g15971 | [
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<p>Since mass and charge behave similarly, so, just like center of mass, I define a point center of charge, that is defined by</p>
<p>$$\vec r_{qm} = \frac {\sum{q_i \vec r_i}} {\sum{q_i}}$$</p>
<p>where $\vec r_i$ is a position vector w.r.t. the origin.</p>
<p>Now suppose just like momentum,there is a quantity we c... | g15972 | [
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<p>I aks you if this reasoning has a base in what we know of universe. There are many articles about so called "vacuum metastability event". As I understand this happens (can happen) with an enormous low probability in every place of the universe. A bubble is produced that then expands with speed of light 'eating' all ... | g15973 | [
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<p>How does one measure the pressure at the end of the manometer tube when the manometer tube itself is having a variable area?</p>
<p><img src="http://i.stack.imgur.com/ZMAcK.gif" alt="manometer with variable area tube"></p> | g15974 | [
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<p>For example, electric, gravitational field decreases with $1/r^2$. Is it like decrease of energy of an object when goes it is moving with friction/air drag etc?</p>
<p>Does it mean that field's strength is being consumed by space or some other objects?</p>
<p>Can we have space where fields' strength don't decrease... | g492 | [
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0.002097013872116804,
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<p>For calculating electric field outside a nonconducting sphere with a hollow spherical cavity. When I use the rule (Charge density= $dQ/dV$), I don't know exactly what is $dV$, is the volume here refers to the volume of the Gaussian surface ($V= 4/3 \pi r^3$) so that $dV$ will be = $ \pi r^2 dr$, or the $V$ is the vo... | g300 | [
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<p>To introduce magnetic monopoles in Maxwell equations, Dirac uses special strings, that are singularities in space, allowing potentials to be gauge potentials. A consequence of this is the quantization of charge.</p>
<p>Okay, it looks great. But is this the only way to introduce magnetic monopoles? </p> | g15975 | [
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<p>Suppose that we have a system of Silicon nanoparticles embedded in ZnO dielectric matrix. i'm thinking about how to construct the energy band structure of this system , suppose that we already have all the values of electron affinity, work function and energy bandgap of c-Si and ZnO. So i will align the Fermi level... | g15976 | [
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<p>Scenario:</p>
<p>You ride in a train, you have this helicopter toy. The train is not yet running when you flew your helicopter on a constant altitude (say 1 meter above the train's floor).</p>
<p>Question:
What will happen on the flying helicopter toy when the train accelerates?</p>
<ol>
<li><p>Will it stay relat... | g506 | [
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<p>I'm trying to reproduce a result from a paper (T. Thatcher, <a href="http://www.engr.uvic.ca/~struchtr/2008ICMMES06_G13BC.pdf" rel="nofollow">Boundary Conditions for Grad's 13 moment equations</a>, equation (32), page 6), however, I haven't been able to do so. Hopefully someone can provide some help.</p>
<p>The gen... | g15977 | [
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<p>What happens if you perform a double slit experiment near an event horizon, if one of the slits is outside, one is inside the event horizon?</p> | g15978 | [
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<p><a href="http://en.wikipedia.org/wiki/Temperature">Temperature</a> is just an indication of the combined property of mass of the molecules and their random motion. We can explain no effective energy transfer between two conducting solid bodies in contact by the condition in terms of mass of molecules and their speed... | g15979 | [
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0.01674557477235794,
0.029628796502947807,
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<p>How would I figure out the Cartesian graph that describes a bar clamped flat for a length on one end with downward force being applied to the other?</p>
<p>I have an idea that the bar will try to average out the stress over the free length. Does it in fact evenly distribute stress over the whole free length? If s... | g15980 | [
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<p>Is there a "quantum mechanical version" of the classical Maxwell-Boltzmann speed distribution for monatomic ideal gases? I'm quite new to thermodynamics, but I just wanted to know. If there is such a distribution, can it be used to calculate the average speeds (such as the most-probable speed, or rms speed classical... | g15981 | [
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<p>Let me assume, that I have an arbitrary electric field. Is there any way to determine what happens to this electric field if it is appolied to a charge in let me say water with natrium chloride in it? I guess there is some kind of response to the electric field by the ions, so that it will just "die out", as the ele... | g15982 | [
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<p>The earth is not a sphere, because it bulges at the equator. </p>
<p>I tried fiddling with centripetal force equations and gravity, but I couldn't derive why this bulge occurs. </p>
<p>Is there </p>
<p>(a) a mathematical explanation using forces (not energies) and </p>
<p>(b) a simple intuitive explanation to e... | g15983 | [
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0.008788932114839554,
0.021921606734395027,
0.046427492052316666,
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<p>This recent paper by <a href="http://arxiv.org/abs/1306.0913" rel="nofollow">Weinberg et al.</a> discusses that one potential problem with our current model of Cold Dark Matter (CDM) is that is predicts a greater number of satellite galaxies for the Milky Way than are actually observed, and satellite galaxies with l... | g15984 | [
-0.035838156938552856,
-0.005765224806964397,
0.015076176263391972,
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0.... |
<p>Say we have two qubits $|a\rangle$ and $|b\rangle$ both initialized to $|0\rangle$. We then apply the rotation gate $R_{x}(\frac{\pi}{2})$ of matrix representation </p>
<p>$\left( \begin{array}{}
\frac{1}{\sqrt2} & \frac{-i}{\sqrt2} \\
\frac{-i}{\sqrt2} & \frac{1}{\sqrt2} \end{array} \right)$ </p>
<p>to ge... | g15985 | [
0.025575781241059303,
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<p>In QFT, specifically in scattering processes, what is the physical significance of the poles / residues of the $N$-point correlation function? And why?</p> | g15986 | [
-0.013820941559970379,
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<p>My understanding is that the exchange of Z bosons could yield an attractive or repulsive "force" between two fermions. For most combinations the electromagnetic or strong interactions will take place.</p>
<p>However, if we have two neutrinos, or a neutrino and a charged lepton, only the weak interaction comes into ... | g15987 | [
0.00971562322229147,
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<p>Does magnetic propagation follow the speed of light? E.g. if you had some magnet of incredible strength and attached an iron wire that is one light year long to it, would the other end of the iron wire begin to show a magnetic field in a year, or could it possibly be faster than a year?</p> | g906 | [
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<p>I understand the double slit experiment up until the point that we begin "detecting" single photons. What does it mean to detect. You cant place a camera in the slit because that would capture the photon just like the photosensitive plates would.</p>
<p>I've also heard that you can do the double slit experiment wit... | g15988 | [
0.013400374911725521,
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<p>1) The field outside a solenoid is approximated to be zero, because of opposites points "cancelling out". Does this approximation of the field being almost zero become worse as the diameter of the solenoid increases? (since the opposite sides are further apart) I'm looking for an answer for two cases: 1) Only the di... | g15989 | [
0.07229532301425934,
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0.0... |
<p>Does charge of a metal charged by induction determine by which part of the metal is ground to? I draw a diagram to make it simple to understand:<img src="http://i.stack.imgur.com/dyAHZ.png" alt="enter image description here"></p>
<p>Right diagram: When ground is touched with the positive side of the metal, electron... | g15990 | [
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0.023875584825873375,
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0.00358... |
<p>This is how I understand batteries and capacitors. The terminals produce an electric field which causes the electrons to move in random directions. The surface charge builds up causing new electric fields to be created, which forces the electrons to move in the direction of the wire, creating current.</p>
<p>But wi... | g15991 | [
0.019735179841518402,
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0.02459872141480446,
0.02115505374968052,
0.011... |
<p>I am familiar with the equation $$\vec{F}=m \vec{a}$$
I am wondering as to whether it is possible for something to exert a force on another object without changing the momentum of said object. My question is: is force defined as a change of momentum? If that is the case, my question is pointless. But if it is not. W... | g15992 | [
0.04835127666592598,
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<p>Would it be theoretically possible for a high energy neutrino and another high energy anti-neutrino to annihilate into a boson?<br>
Which boson(s) would be possible theoretically?<br>
- one or more photons ?<br>
- the Higgs boson ?<br>
- Z boson ? </p> | g15993 | [
0.0022035902366042137,
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<p>I am confused about the age of the Universe. </p>
<p>If you calculate it by $1 / H_0$, won't the answer be roughly the same today as it will be 30 billion years from now?</p>
<p>I know $H_0$ is a parameter, not a constant, but it doesn't change that much, does it?</p>
<p>And if the expansion is accelerating then ... | g452 | [
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<p>No doubt it's been questioned before so what is the theory or experiment? If there is an experiment. </p> | g15994 | [
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0.02406088262796402,
0.013359849341213703,
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0.00... |
<p>Expression for kinetic energy in Cartesian coordinate:</p>
<p><img src="http://chart.apis.google.com/chart?cht=tx&chl=T%3D%20%5Cfrac%7B1%7D%7B2%7Dm%20%5Cdot%7Bx%7D%5E2%20%20%2B%20%5Cfrac%7B1%7D%7B2%7D%20m%20%5Cdot%7By%7D%20%5E2%0A%0A"></p>
<p>Expression for kinetic energy in polar coordinate (applying the tran... | g15995 | [
0.04619511961936951,
0.016240984201431274,
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0.03133897855877876,
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0.005197607912123203,
0.05020252242684364,
0.002242207294330001,
0.043468669056892395,
-0.0324... |
<p>In Matt Strassler's recent post (<a href="http://profmattstrassler.com/2013/09/24/quantum-field-theory-string-theory-and-predictions-part-2/">here</a>) he makes the statement that scale invariant (I assume he means conformally invariant, more generally) theories have no particles in them. What's the reason for this... | g15996 | [
0.056145910173654556,
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0.03974616155028343,
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0.007743320893496275,
0... |
<p>How does the <a href="http://en.wikipedia.org/wiki/Fraunhofer_diffraction" rel="nofollow">Fraunhofer</a> <a href="http://en.wikipedia.org/wiki/Irradiance" rel="nofollow">irradiance</a> distribution look for a double slit aperture with $d$ = integer multiples of $b$?</p> | g15997 | [
0.02682952955365181,
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0.06577246636152267,
0.053221311420202255,
0.0... |
<p>We all know that stuff can't go faster than the speed of light - it's length becomes negative and all kinds of weird stuff happens. </p>
<p>However, this is in relation to what? If two objects, each moving at 0.51 times the speed of light in relation to some point pass each other, do they disappear?</p> | g109 | [
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0.031883250921964645,
0.006621892563998699,
0.016181742772459984,
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<p>I just read in some class notes for a crystallography class that there are no refractive lenses for X-rays because the index of refraction of most materials is close to 1. Is the index of refraction dependent on the wavelength of the light then? Like, a material has different indices for different types of electroma... | g15998 | [
0.018764754757285118,
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0.07581313699483871,
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0.004154965281486511,
-0.038685... |
<p>What is a good place to learn the details of symmetry breaking? What I am looking for is a more serious exposition than the wiki-article, which explains the details, especially the mathematical part, but at the same time less detail than the typical quantum field theory book. Preferably I would like to see a clean m... | g15999 | [
0.04522475227713585,
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0.04362345114350319,
0.030146518722176552,
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0.0019065738888457417,
-0.00... |
<p>I've recently started studying the <a href="http://en.wikipedia.org/wiki/K%C2%B7p_perturbation_theory">$k\cdot p$ method</a> for describing electronic bandstructures near the centre of the Brillouin zone and I've been finding it hard to find any pedagogical references on the subject.</p>
<p>In every paper I read th... | g16000 | [
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0.009089140221476555,
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0.0432513989508152,
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0.04965... |
<p>Apologies if I have this completely wrong (and for the general long-windedness). I've searched online but can't find anything helpful/relevant. </p>
<p>I'm trying to use the geodesic equation</p>
<p>$$\frac{D^{2}\xi^{\mu}}{D\lambda^{2}}+R_{\phantom{\mu}\beta\alpha\gamma}^{\mu}\xi^{\alpha}\frac{dx^{\beta}}{d\lambda... | g16001 | [
0.034460678696632385,
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<p>BCS theory, in which electrons form Cooper pairs, has been successful in explaining conventional superconductivity. Physicists have adopted similar pairing mechanism in an attempt to explain high-temperature superconductivity (HTS).</p>
<p>Is there any HTS theory that is not based on pairing? If not, what experimen... | g16002 | [
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0.02442... |
<p>I am reading <a href="http://dao.mit.edu/~wen/pub/cll.pdf" rel="nofollow">this paper</a>(pdf) and on page 11, the chiral boson theory on a cylinder is studied when both edges of the cylinder are brought in close proximity so that electron is allowed. </p>
<p>Why is it that for large tunneling amplitudes, $g$, the f... | g16003 | [
0.03370286524295807,
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0.0193176232278347,
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<p>In this <a href="http://inspirehep.net/record/24933?ln=en" rel="nofollow">paper by Dijkgraaf, Vafa, Verlinde, Verlinde</a>, orbifold CFT is discussed.</p>
<p>In that paper, it outlined that orbifold CFT provides a way to generate the new theories from the old known ones. (i.e. "... it would be very interesting to d... | g16004 | [
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0.005297791212797165,
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0.03647841140627861,
-... |
<p>For equilibrium/ground state systems, a (Wilson) renormalization group transformation
produces a series of systems (flow of Hamiltonians/couplings $H_{\Lambda}$ where $\Lambda$ is the cut-off) such that long-wave/asymptotic behaviour of $H_{\Lambda}$
is the same as of $H_{\Lambda'}$ after rescaling by $\Lambda/... | g16005 | [
0.00038482362288050354,
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0.018621869385242462,
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0.02473120205104351,
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... |
<p>I consider zero temperature and high lepton number chemical potential $\mu$. This results in a neutrino (or antineutrino, depending on the sign of the potential) "sea" filling a Fermi sphere in momentum space. There are profound effects on particle stability</p>
<p>In the $\mu << 0$ case, the neutron becomes ... | g16006 | [
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<p>I am trying to find the domains in physics where solving large systems of equations is computationally expensive. The sparse systems are of my particular interest, where the input matrix A is in GBs (up to 100 GBs).</p> | g16007 | [
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-0.005499121733009815,
-0.02247522957623005,
0.00877053290605545,
0.006861145608127117,
0... |
<p>I am searching for a microscopy technique in wet conditions. It must be possible to see through the specimen. ESEM is good but can't see through. TEM needs high vacuum which will boil away water. The specimen is embedded inside a gel. The size of the specimen is between 0.5 µm and 20 µm.</p> | g16008 | [
0.001786127919331193,
0.024266168475151062,
0.01184676680713892,
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0.013131056912243366,
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0.03586742654442787,
0.05426310747861862,
0.0033024572767317295,
0.029714183881878853,
-0.00... |
<p>Why is there no analog for $\Theta_\text{QCD}$ for the weak interaction? Is this topological term generated? If not, why not? Is this related to the fact that $SU(2)_L$ is broken? </p> | g16009 | [
0.05065247789025307,
-0.03380940854549408,
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0.024706048890948296,
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0.023621011525392532,
-0.00021769512386526912,
0.05302735045552254,
0.... |
<p>In the case of a bubble, the outside pressure is less then the inside pressure. </p>
<p>If that is the case can bubbles exist in vacuum? I am not sure but this should be true if vacuum has zero pressure</p> | g16010 | [
0.05500301718711853,
0.022392675280570984,
0.02732480689883232,
0.04097655415534973,
0.039936404675245285,
0.0847148448228836,
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0.005884911864995956,
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0.01986715... |
<p>Does the spin of the earth around its axis vary at different distance from the sun?,if so how does it correspond to the length of day and night,?</p> | g16011 | [
0.004787465091794729,
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0.03518722951412201,
0.013747924007475376,
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0.02841763384640217,
-0.... |
<p>A few years ago I read a short little article about how big our eyes would have to be to observe microwaves (or any long-wave radiation for that matter). I don't remember enough about the article, or know enough about observing EM waves to reconstruct the equations, and I can't find the article again.</p>
<p>So my... | g16012 | [
-0.041644155979156494,
0.06876346468925476,
0.003878637682646513,
-0.06382670253515244,
-0.03804333880543709,
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0.012824001722037792,
0.00036558200372383,
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-0.025955509394407272,
0.016344808042049408,
0.0767914354801178,
0.07366327196359634,
0.0355... |
<p>I often see the relation that $\vec v=\vec v_0+ \vec \omega \times \vec r$ in a turning reference frame, but where does it actually come from and how do I arrive at the acceleration being $$\vec a=\vec a_0+ 2\vec \omega \times\vec v+ \vec \omega \times(\vec \omega \times \vec r)+\dot{\vec \omega} \times \vec r\,\,\... | g16013 | [
0.07109356671571732,
0.02265484817326069,
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0.08723630011081696,
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0.02169942483305931,
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0.017069082707166672,
0.064393050968647,
0.0545236... |
<p>In some recent works, I got the information that low rank mixed states need not be bound entangled. In particular, for the system $3\otimes 3$ there is no bound entangled states. Can anyone tell me how to prove it or give a proper reference? </p> | g16014 | [
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0.0060060597024858,
0.02398882992565632,
0.006378237158060074,
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-0.014948064461350441,
-0.008563042618334293,
-0.0601532906293869,
-0.05... |
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