question stringlengths 37 38.8k | group_id int64 0 74.5k |
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<p>I need to solve this problem as part of my review in college physics. The task is to find the value of 5 branch currents using Kirchhoff's laws and elimination method (or maybe called elimination by substitution BUT not using any matrix method).</p>
<p>The circuit is:
<img src="http://i.stack.imgur.com/DNVkI.png" ... | 5,001 |
<p>I have come across a very new idea for me concerning nuclear weapons effects, check <a href="http://en.wikipedia.org/wiki/Talk%3aEffects_of_nuclear_explosions#Units_and_blast_absorption_due_to_destructive_work" rel="nofollow">this</a> please.</p>
<p>In brief, that person states that blast overpressure attenuates/de... | 5,002 |
<p>I tried deriving the expression for chemical potential of a Relativistic Fermi Gas using asymptotic expansion (for large z) in :</p>
<p>$$ N = \frac{V}{h^3}4\pi (KT)^3g_s \int \frac{p^2 dp}{e^{p-\nu}+1} $$
where $ z = e^\nu $ and $ \nu =\frac{\mu}{KT} $</p>
<p>After evaluating the integral by asymptotic expansion... | 5,003 |
<p>This is a quite specific question continuing the problems I have with computing the expectation value of intersecting Wilson loops I laid out <a href="https://physics.stackexchange.com/questions/119529/intersecting-wilson-loops-in-2d-yang-mills">here</a>. Using the tools from the answer there, I quite quickly arrive... | 5,004 |
<p>It is well known that in Schwarzschild space-time, a torque-free gyroscope in circular orbit at <em>any</em> permissible angular velocity at the photon radius will, if initially tangent to the circle, remain tangent to the circle everywhere along its world-line. This is usually explained as follows. Say I'm describe... | 5,005 |
<p>Would a rotating sphere of magnetic monopole charge have electric moment ? </p>
<p>In a duality transformation E->B.c etc. how is the magnetic moment translated m = I.S -> ?
Mel = d/dt(-Qmag/c).S ? </p>
<p>A more general question would a sphere charged with monopoles have other moments that the monopole in the mul... | 5,006 |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://physics.stackexchange.com/questions/17741/how-does-electricity-propagate-in-a-conductor">how does electricity propagate in a conductor?</a> </p>
</blockquote>
<p>I have read that in an electrical wire electrons movement is very slow while ... | 174 |
<ol>
<li><p>Why non integer spins obey Fermi statistics?</p></li>
<li><p>Why is fractional statistics and non-Abelian common for fractional charges?</p></li>
</ol> | 5,007 |
<p>I came across a contraction which is not giving the desired result. This is a toy problem in how to get a supergravity theory in low energy limit of a superstring theory using the vanishing of beta function in the $\sigma$ model, however there is no use of this context.</p>
<p>What I want to ask is contracting d an... | 5,008 |
<p>Suppose we have a simple harmonic oscillator, let's consider the ground state, $|0\rangle$ and the first excited state $|1\rangle$.</p>
<p>$\langle 0|\hat p|0 \rangle$ is zero right? Since the particle can either be travelling to the left or right, where $\hat p$ is the momentum operator.</p>
<p>Similarly, I think... | 5,009 |
<p>When studying from the book by Wise and Manohar, <em>Heavy Quark Physics</em> (pg 102), I came across a seemingly simple identity that I am not able to prove. It's likely an easy problem but I can't for the life of me figure out why. </p>
<p>First they define the transverse covariant derivative,</p>
<p>$$D_\perp \... | 5,010 |
<p>So, the way I understand this is as follows :</p>
<p>The alveoli (pretend they're bubbles) have diameters of the order of microns implying a massive pressure required to inflate them by the Young-Laplace equation.</p>
<p>$p_{in}-p_{out}=\frac{2\gamma}{r}$</p>
<p>However, the presence of pulmonary surfactant molec... | 5,011 |
<p>How to calculate electric field between two electrodes - square and circular?</p> | 5,012 |
<p>The question is the same as the one I put in the title but here it is in more words.</p>
<p>I was wondering if there were any substances that allowed sound to travel more efficiently. For example water is obviously a much worse way to transport sound then air. </p> | 5,013 |
<p>I'm reading <a href="http://www.sciencedirect.com/science/article/pii/0040609082905909" rel="nofollow">this paper</a> which is essentially about connecting the complex permittivity $\epsilon$ with the microstructure of a thin film. They talk about how you can place limits on the possible values of $\epsilon$ dependi... | 5,014 |
<p>In <a href="http://de.wikipedia.org/wiki/Stefan-Boltzmann-Gesetz#Beispiel" rel="nofollow">a German Wikipedia page</a>, the following calculation for the temperature on the surface of the Sun is made:</p>
<p>$\sigma=5.67*10^{-8}\frac{W}{m^2K^4}$ (Stefan-Boltzmann-constant)</p>
<p>$S = 1367\frac{W}{m^2}$ (solar cons... | 5,015 |
<p>If we can think about the universe as a wave function then many particles should be entangled with many other particles in the universe. The obvious question arises why we don't see those entanglements in everyday circumstances. One standard explanation given is those entanglements average out and cancel so we can i... | 5,016 |
<p>What velocity would a small body moving towards a large body reach under gravity alone?
More importantly, is there a 'terminal velocity' for the small body due to the increasing energy required to accelerate the body as its velocity increases?</p>
<p>Assumptions: No other forces, gravity acts over infinite distance... | 5,017 |
<p>Seiberg traced the nonrenormalization of supersymmetric theories to holomorphy of the superpotential in chiral superspace. However, this overlooks the fact that with a different number of supersymmetric generators, supersymmetry can be real or symplectic, instead of complex. But yet, even for those cases, we still h... | 5,018 |
<p>My question refers to an overview of the biggest stars we know: <a href="http://farm5.static.flickr.com/4138/4820647230_faba1c9f3b_o.jpg" rel="nofollow">http://farm5.static.flickr.com/4138/4820647230_faba1c9f3b_o.jpg</a></p>
<p>Why are some of those blue?</p> | 5,019 |
<p>What does it mean that the Higgs has a nonzero vacuum expectation value? Are there any other important field with nonzero VEV? How is this related to the 100-orders magnitude wrong prediction?</p> | 5,020 |
<p>For one of my experimental setup I need to place a mirror perfectly parallel to a wall. It can be placed at any distance from the wall. I would like to use any method other than direct measurement. I am free to use the following:</p>
<p>a webcam</p>
<p>a secondry mirror</p>
<p>Edit: It's not necessary to use all ... | 5,021 |
<p>This has always puzzled me. Yesterday (in London) it started hailing despite it being about $20^oC$. A couple of years ago I experienced hail in Sicily when it was about $35^oC$ in the shade!. How is this possible?</p> | 5,022 |
<p>I have a question regarding the <a href="http://en.wikipedia.org/wiki/Mass%E2%80%93energy_equivalence" rel="nofollow">energy-mass</a> conversion. Well, when a particle starts moving with a speed comparable to that of light, its (relativistic) mass increases that means some matter is created and that too of the same ... | 5,023 |
<p>I know this is essentially a mathematic question, but I received no answer on math SE. Moreover it has a direct application in physics, so I thought to ask this here too.</p>
<p>The momentum operator in one dimension in quantum mechanics is $P=-i\frac{d}{dx}$ (with $\hbar=1$). Consider it as an operator on $L_2(0,2... | 5,024 |
<p>I want to describe the interaction between a target and a probe and know that this is described by some unitary operator that acts on both systems.</p>
<p>My operator needs to implement a $\pi/q$ rotation in the equatorial plane. I need to perform a Von Neumann measurement on the probe which is described by a proje... | 5,025 |
<p>In addition, to get light to other side of the wall, could it be converted to radio waves and then back to light waves?</p>
<p>Edit: My idea was if there was a special material that was painted on both sides of a wall that converted radio waves to light waves and light waves to radio waves would the wall appear inv... | 5,026 |
<p>To give context to this question, I am currently looking into non-locality / hidden variables / Bell's Theorem, EPR / etc.</p>
<p>I've noticed the assertion that the values / state of something when measured aren't what the values / state would be if the measurement were not made.</p>
<p>How is this known? Or is ... | 5,027 |
<p>How important are proofs in physics? If something is mathematically proven to follow from something we know is true, does it still require experimental verification? Are there examples of things that have been mathematically proven to some reasonable degree of rigor (eg satisfy a mathematician) that turned out to be... | 5,028 |
<p>Say you have two planes flying next to each other at the same speed and one decides to pick up speed by burning a tank of rocket fuel.</p>
<p>If someone on the ground wanted to know that plane's new speed after burning the fuel and knew the plane's mass, initial speed, and energy stored in the fuel, he could calcul... | 5,029 |
<p>We know, that one-particle states can be earned from relativistic fields, which can be interpreted as functions determined on Minkowski space-time. Field must satisfy some conditions, by which we classify them as massive/massless, spin/helicity, etc. Electron can be represented as one-particle state of bispinor fiel... | 5,030 |
<p>I'm trying the following:</p>
<p>The filament inside a 100 W lightbulb has an absorption coefficient of 0.25, and while operating, it is at a temperature of 2,573 K. What's the size of the surface of the filament? (done with Stefan-Boltzmann) At what wavelength does it emit the highest intensity? (done with Wien di... | 5,031 |
<p>The notes state that $N=mg$. However, if I have a $4\text{kg}$ box on a table, taking upward as positive
$$N=-mg=-4*-9.81$$
Is this correct? If it is correct, why do the notes state that $N=mg$. Should I only use the magnitude of gravity?</p> | 5,032 |
<p>I have a problem with this exercise because I really don't know how to proceed. It's related with the "S-matrix".</p>
<p>In class we saw this example:</p>
<p>Consider the spherically symmetric potential:</p>
<p>$$V(r)=\begin{cases}
-V_{0}, & 0\leq r\leq a\\
0, & r>a
\end{cases} $$</p>
<p>We know that ... | 5,033 |
<p>Accelerating away from a mass mitigates gravity's pull on the accelerating object. Would the same be true for an object accelerating towards the center of the mass?</p> | 5,034 |
<p>can anyone help me to determine the heat flux (Kw/m2) on a focal point of a parabolic dish having a diameter of 1.5 meter and a focal length 60 cm ???
please awaiting your soonest reply for my senior project :(
Regards</p> | 175 |
<p>Why is it that currents don't flow at the speed of light, but rather significant ratios of the speed of light.
I don't have any formal reasoning as to why they would flow at the speed of light-I just feel as if it would make sense.
That being said, the fact that they do move at near the speed of light is also pecu... | 5,035 |
<p>When one travels in a bus, if he's sitting at any window, he will feel that the air is coming inside. If someone is standing at the open door of the bus, he'll also feel that the air is coming inside.
If so much air is coming inside, why doesn't the bus blow due to internal pressure?</p> | 858 |
<p>Why is it that we can use the Poynting Vector to find the power dissipated in a Coaxial Cable? Unlike the situation with light, where the c makes sense, inside the coaxial cable I see no reason why there should be a factor of c considered, and while we have both electric and magnetic fields, it's just not light!
Any... | 5,036 |
<p>When receiving servers (while playing tennis), I've noticed that the tennis ball seems to bounce up higher on me when the server uses a topspin serve than when the server hits a flat serve. Why is that?</p>
<p>Is it because of something about how the spin affects the bounce of the ball (i.e., the effect of the spi... | 5,037 |
<p>I'm attempting to approach this using the identity
$$F/A = I/c$$
I can solve for Area easily enough
$$A = F(c/I)$$
and I know the distance $d$ is
$$d=1/2(at^2)$$</p>
<p>But I'm having difficulty trying to relate this to the time it would take to reach mars.</p>
<p>Any ideas where to go from here?</p> | 5,038 |
<p>I came across the use of the unit barn and inverse barn while reading about the operation of LHC. What is an inverse femtobarn ? What does it tell about the experiment being described ? </p> | 5,039 |
<p>I've heard it said many times that you're more likely to burn food on an electric stove than a gas one, but I can't tell a difference. This seems to me to be a fallacy perpetuated by the natural gas industry, and I would expect the issue to just be people are not sure how to accurately adjust the system they're not ... | 5,040 |
<p>Quite often I go out in the morning and I'm in Milton Keynes, so I would expect the moon to rise in the east and set in the west. Sometimes at about 2, 3, 4 o’clock in the morning the moon is low in the east. I was just wondering how that worked out?</p> | 5,041 |
<p>Fluorescent lights are already efficient when they’re running but I’ve heard that it takes a lot of energy to turn a fluorescent light tube on. So is it more efficient to turn off a fluorescent tube immediately when you’ve finished using it or is it better to leave it on and then wait until you’re more likely to not... | 5,042 |
<p>On every ductless mini-split air conditioner I've ever seen, both the high and low pressure lines are insulated between the compressor and the building. </p>
<p>It seems like the liquid refrigerant coming out of the condensing coil can never be cooler than the outdoor ambient air temperature because the outdoor air... | 5,043 |
<p>So I have a question about what i should do with my path to learning quantum physics. I just have no idea where to start or to continue from where I left off. I have been studying quantum mechanics for a good year now. I dont know what level my knowledge of QM is but I finished Griffiths qm and i have gone through m... | 5,044 |
<p>Angular momentum causes the <a href="http://en.wikipedia.org/wiki/Event_horizon" rel="nofollow">event horizon of a black hole</a> to recede. At maximum angular momentum, $J=GM^2/c$, the <a href="http://en.wikipedia.org/wiki/Schwarzschild_radius" rel="nofollow">Schwarzschild radius</a> is half of what it would be if ... | 5,045 |
<p>I am confused about Newton's 3rd Law. If a person jumps off the ground a force is applied both to the person and to the ground. However, as $F=ma$ acceleration experienced by the Earth is much less than that experienced by the person.</p>
<p>But: I press with gravitation force on the ground so it should press with ... | 5,046 |
<p>When an atom bomb goes off some matter is converted to energy according to $E = m c^2$.</p>
<p>I'd like to know exactly what matter in the original atom bomb is converted to energy. Is it protons, neutrons, electrons? Is it a collection of atoms? What goes?</p> | 5,047 |
<p>Related: <a href="http://physics.stackexchange.com/questions/79212/which-green-spectral-lines-are-emitted-in-a-thomson-tube">Which green spectral line(s) are emitted in a Thomson tube?</a></p>
<p>After reading Lisa Lee’s OP on an electron deflection tube, although she had some misunderstandings on its operation, I ... | 5,048 |
<p>Why is it that solids on compression [As in striking a hammer etc.] heat up,
but liquids and gases on compression [Pressurizing liquids causes them to freeze or gases to liquify] cool down?
Can someone explain this please?</p> | 5,049 |
<p>I am very sorry for posting these problems in this forum, but i don't know where to post otherwise... I have a weird special relativity problem where i get a relative speed $u$ which is larger that $c$. I dont need an solution but rather some guidance towards my understanding of the special relativity...</p>
<block... | 5,050 |
<p>One way Wikipedia <a href="http://en.wikipedia.org/wiki/Ohm_%28unit%29" rel="nofollow">defines Ohm</a> is (this is also teached in school):
$$1\Omega =1{\dfrac {{\mbox{V}}}{{\mbox{A}}}}$$
They describe this definition in words, too:</p>
<blockquote>
<p>The ohm is defined as a resistance between two points of a c... | 5,051 |
<p>I got really confused about real gases volume and ideal gas volume. Ideal gas molecules take up no space, if we put gas into a 2.4L water bottle, we know that all the gas will expand all over the bottle and we say at this moment the gas has volume of 2.4L. So what is this volume? </p> | 5,052 |
<p>I'm wondering how can one formally justify the electromagnetic response of a system which does not verify local U(1) gauge invariance.</p>
<p>A good example of what I would like to consider is given by the two-body interaction term discussed in relation with superconductivity as I'll elaborate below, but many examp... | 5,053 |
<p>If I place a solenoid connected to a bulb inside a bigger solenoid which is connected to a power source, will the bulb glow?</p> | 5,054 |
<p>I am reading 't Hooft's noted on Black holes, where he quotes the Kerr metric for a black hole rotating about the z-axis as follows:
<img src="http://i.stack.imgur.com/rW8v0.png" alt="enter image description here"></p>
<p>He later says:
"The parameter a can be identified with the angular momentum i.e. $$J=aM$$"</p... | 5,055 |
<p>I am studying for an exam, and this is part of a problem in my book.</p>
<p>A projectile is launch from level ground and is intended to hit a target 100m away. Instead, it explodes into two fragments of equal mass, one of which lands 100m beyond the target. If the fragments don't take the same amount of time to la... | 5,056 |
<p>Can substances other than H2O have a triple point, where the three usual phases of matter (solid/liquid/gas) can exist?</p> | 5,057 |
<p>Is the electric field between two positively charged parallel infinite plates one with a charge density twice the other effect the electric field on the outside of the plates? I am thinking no, because the field lines cannot cross in the field between the plates since they have positive charges. What does the electr... | 5,058 |
<p>How to easily, using standard <a href="http://en.wikipedia.org/wiki/DIY">DIY</a> equipment measure the strength of magnetic field generated by a permanent magnet?</p>
<p>Narrowing down the "loose language" of the above:</p>
<p>strength of magnetic field: either flux density <strong>B</strong> at given point relati... | 5,059 |
<p>I'm sorry for this question but, I just don't get it. According to the electromagnetic field theory, electrons repel each other by exchanging photons. How do protons attract electrons, by photon exchange?</p> | 5,060 |
<p>We are conscious to live in a 3 dimension universe. Maybe it has more than 3 spatial dimensions (like the 10 mentioned in the string/M-theory) but that is not my concern here. My question is the following.</p>
<p>Is this number of (at least) 3 related with our cognitive process? I mean: in a cognitive process, ther... | 5,061 |
<p>Suppose an object is thrown parallel to the ground. The gravity acts downward (ie. perpendicular to the direction of motion of the object). The work done by gravity on that object will be given by : </p>
<p>$\text{Work}, W = F \cdot S = FS\times\cos \theta$</p>
<p>$\implies W=FS \cos 90$ ($\because$ direction of g... | 5,062 |
<p>According to the Wikipedia page on the Standard Model, the Higgs field interact with fermions through a Yukawa interaction coupling only left to right chiralities. What is the reason for that? Is that the case with all Yukawa couplings?</p> | 5,063 |
<p>What is the motivation for including the compactness and semi-simplicity assumptions on the groups that one gauges to obtain Yang-Mills theories? I'd think that these hypotheses lead to physically "nice" theories in some way, but I've never, even from a computational perspective. really given these assumptions much... | 5,064 |
<p>In a textbook about semicoductor physics, I came across a passage about deriving the carrier concentration at thermal equilibrium in semiconductors I didn't quite grasp:</p>
<blockquote>
<p>The recombination $R(T,n,p)$ rate depends on the ionization energy, temperature $T$, and carrier concentrations $n$, $p$. A... | 5,065 |
<p>What is the name for a particle with zero mass, zero charge, no strong force, no weak force and has no energy?</p> | 5,066 |
<p>Plant X has a radius of 5000 km and is composed of two layers. </p>
<p>The first inner layer ranges from the centre to 2000 km from centre, it's density is 8 kg / dm^3. </p>
<p>The second layer ranges from 2000 km to 5000 km from the centre, it's density is 4 kg/ dm^3. </p>
<p>What is the gravitational accelerati... | 5,067 |
<p>After reading about light polarization I understood, that if light is polarized:</p>
<ul>
<li>circularly left then the spin of each photon is parallel to the velocity</li>
<li>circularly right then the spin of each photon is antiparallel to the velocity</li>
<li>elliptically - then there's more one photons, then th... | 5,068 |
<p>I'm trying to design a quasi-simple vertical axis wind turbine, and a coworker came up with <a href="https://docs.google.com/drawings/d/1B-NzCTWUyBIhNcv9b46hKvyk6R-l4NXiVzGHsb01fTI/edit?hl=en&authkey=CNeWgdwL" rel="nofollow">this design</a> to focus the wind as it reaches the turbine in a wind tunnel. He says t... | 5,069 |
<p>Given I have two identical balloons on earth, how will the buoyancy compare between the one filled with helium and another filled with hydrogen?</p>
<p>How can I calculate the ratio of buoyancy given two different substances and identical balloons?</p>
<p>I am also interested in the equations relating to this prob... | 5,070 |
<p>I have recently come across some cosmological assertions (based on empirical data) about the universe being self contained in the sense that it is entirely capable of coming into existence from a zero-energy initial state . This is based on the observation that at grand scale the positive and negative gravity/energ... | 5,071 |
<p>Title says it all - recently I encountered a strange homework exercise on de Broglie dual theory with an electron wavelength of few millimeters - which implies the velocity lower than 1 m/s. I personally considered the problem very artificial and unrealistic, but it made me wonder - what is the smallest electron vel... | 5,072 |
<p>Just need a clarification here, how the current is produced due to the movement of electrons, in an external circuit,having a very slow drift speed.</p>
<p>Normally in a battery there is high potential terminal and low potential. Using these two terminals the external circuit is closed. Now within the battery the d... | 5,073 |
<p>How did Kepler arrive at his <a href="http://en.wikipedia.org/wiki/Kepler%27s_laws_of_planetary_motion">laws</a>? If one already knows the distances to the planets (and the eccentricity of the orbits etc.) it is understandable how one might proceed to establish the second and the third Kepler's laws. However how did... | 5,074 |
<p>We have some discussions in Phys.SE. about the <a href="http://physics.stackexchange.com/questions/90257/braiding-statistics-of-anyons-from-a-non-abelian-chern-simon-theory">braiding statistics of anyons from a Non-Abelian Chern-Simon theory, or non-Abelian anyons</a> in general. </p>
<p>May I ask: <strong>under wh... | 5,075 |
<p>An object sits on an inclined plane. The weight of the object will have a normal and parallel component. I always thought that the reaction of the plane was simply the negative of the normal component of the weight.</p>
<p>Similarly, an object swings on a pendulum. The weight of the object can be decomposed into a ... | 5,076 |
<blockquote>
<p>[I]f you want a universe with certain very generic properties, you seem forced to <em>one</em> of three choices: (1) determinism, (2) classical probabilities, or (3) quantum mechanics. [My emphasis.]</p>
</blockquote>
<p><sup>Scott Aaronson, <a href="http://www.cambridge.org/9780521199568" rel="nofol... | 5,077 |
<p>my question concerns the interaction of light and matter in a semi-classical approach.
(Quantized Atoms, Classical Fields)</p>
<p>In the Coulomb gauge (div A = 0 , $\phi$=0) we have $E = -\frac{1}{c}\partial_{t}A$ and
$B = rot(A)$. </p>
<p>Let's now consider a system of N charged particles (all denoted by an ind... | 5,078 |
<p>For a missile travelling from (0,0) at angle $\theta$ (to the horizontal) and initial velocity $u$, the y (vertical) position at time t is given by</p>
<p>$s_{y} = u\sin (\theta) t - 0.5gt^{2}$</p>
<p>and the x position id</p>
<p>$s_{x} = u\cos(\theta)t$,</p>
<p>but I am struggling to calculate the angle $\theta... | 5,079 |
<p>I have read many descriptions of electron double slit experiment but I could not find the description from the first principles of quantum mechanics. Most of the descriptions makes comparison with light waves or water waves and after some arguments from optics explain why the interference happens. Light waves and wa... | 5,080 |
<p>Quantum dots are quantum systems that are confined by definition on the nano scale. Why didn't people study similar systems on a much smaller scale, something as small as the dimension of the nucleus? Is it practically difficult? or useless?</p>
<p>R.</p> | 5,081 |
<p>Can anyone explain why $T_{\mu \nu} = \frac{2}{\sqrt{-g}} \frac{\delta \mathcal{L}_M}{\delta g^{\mu \nu}} $, other than justifying it from the Einstein field equations?</p> | 5,082 |
<p>$\newcommand{\ket}[1]{\left| {#1} \right> }$
I have no academic background in physics, but I'm attempting to study quantum computation.</p>
<p>I have read that a quantum system of two qubits is represented by normalized combinations of the basis $\left\{ \ket{00},\ket{01},\ket{10},\ket{11} \right\} $.
A measurem... | 5,083 |
<p>My understanding from my QFT class (and books such as <a href="http://rads.stackoverflow.com/amzn/click/0521469465" rel="nofollow">Brown</a>), is that many-particle QM is equivalent to field quantization. If this is true, why is it not an extremely surprising coincidence? The interpretation of particles being quanta... | 5,084 |
<p>Quantum search enables square-sped up search for marked element. When there are multiple maked element, grover search provides only superposition of them. If I want to find all the marked elements, not superposition, I could try this:</p>
<p>1) Do Grover search, get superposition of t marked ele, </p>
<p>2) observ... | 5,085 |
<p><a href="http://en.wikipedia.org/wiki/navier-stokes_equations">Navier-Stokes equation</a> is non-relativistic, what is relativistic Navier-Stokes equation through Einstein notation?</p> | 5,086 |
<p>I have a general question concerning a given interacting Lagrangian:</p>
<p>$$\mathfrak{L}_I = \frac{g}{\Lambda^2} \bar{\chi} \ \gamma^\mu \gamma_5 \ \chi \ \partial^\nu F_{\mu\nu}$$</p>
<p>where $F_{\mu\nu}$ is the electromagnetic field strength tensor. $g$ is a coupling constant and $\Lambda$ a cutoff-scale.</p>... | 5,087 |
<p>I am trying to determine the boltzmann constant by using a bipolar junction transistor.</p>
<p>In my circuit (apparently I don't have enough point to join a image sorry), the Ebers and Moll model gives the relation
$ i_c = I_s\exp\left(\frac{V_{BE}}{V_T}\right)$</p>
<p>where</p>
<p>$ V_T= \frac{k_b\cdot T}{q}$
... | 5,088 |
<p>Could a particular Standard Quantum Mechanics representation be a constrained 2 + 1 space-time theory (membrane theory) ?</p>
<p>(i) This question is motivated by a possible (approximative) analogy with Matrix theory for M-Theory (see this <a href="http://hep1.c.u-tokyo.ac.jp/workshop/komaba99/taylor.ps" rel="nofol... | 5,089 |
<p>I would particularly like to know why this process is considered the main search mode for Tevatron but useless for search at LHC.</p> | 5,090 |
<p>I just started learning about vector components and relative motion. I don't understand what relative to something means. I looked online but none of the explanations are helpful. </p>
<p>If someone could give me a very simple explanation, it would be appreciated.</p> | 5,091 |
<p>Introduction:</p>
<p>When toying with gravitational and electromagnetic equations in my undergrad days I stumbled upon this interesting relationship. </p>
<p>With the very childish hopes of unifying gravitation and electromagnetism all by myself;) I thought to equate the classical gravitational field to the class... | 5,092 |
<p>A distance on a straight line from point $a$ to $b$ is $2 km$. A student walks from this line with a speed of 4km/h and another student walks with a speed of 6km/hour. what is the average velocity and average speed of student?</p> | 5,093 |
<p>We all know that subatomic particles exhibit <a href="http://en.wikipedia.org/wiki/Introduction_to_quantum_mechanics#Copenhagen_interpretation" rel="nofollow">quantum behavior</a>. I was wondering if there's a cutoff in size where we stop exhibiting such behavior.</p>
<p>From what I have read, it seems to me that w... | 5,094 |
<p>One explanation I read:</p>
<p>Because of the wing's geometry, the "upper" side of the wing is longer, so the air has to travel faster:</p>
<p><img src="http://i.stack.imgur.com/HDgVA.jpg" alt="enter image description here"></p>
<p><strong>My wondering</strong>: Who said (and what was his/her explanation) that ... | 17 |
<p>In a continuous medium the Lorentz force density is known to be written in the form:</p>
<p>$f_\alpha = F_{\alpha \beta} J^\beta$,</p>
<p>where $F_{\alpha \beta}$ is an electromagnetic field tensor, and $J^\beta$ is a charge-current density.</p>
<p>Whould it be correct saying that the action of this force on char... | 5,095 |
<p>What is the motivation for assuming "Page" scrambling for Hawking radiation?</p>
<p>Obviously, at the semiclassical level, we want the outgoing Hawking radiation to look thermal and mixed. However, surely there are possible pure states which are scrambled enough that it looks effectively thermal when not nearly all... | 5,096 |
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