Green Definition and 306 Threads

Homework Statement Show that the explicitly covariant expression: GR(x-y) = θ(x0-y0)δ((\vec{x}-\vec{y})2)/2\pi agrees with the retarded Green function: δ(x0-y0-|\vec{x}-\vec{y}|) / (4\pi|\vec{x}-\vec{y}|) Homework Equations N/A The Attempt at a Solution I know that the...

I am having trouble understanding something that I am sure is very basic. Let's say I have a particle that is hopping on a 1d lattice with a hard wall at x=0 in the presence of some potential - anything, say linear ##H_0=F*i## or Coulomb ##H_0=C/i## where i is the label of the site the particle...

Is chlorophyll "green" or green? Something I can't find a precise answer on is if chlorophyll reflects only green light. Each color has an associated wavelength, but as shown in a CIE chromaticity diagram, you can combine different wavelengths of light to create the perception of a single...

Homework Statement The generalized Green function is $$ G_g(x, x') = \sum_{n\neq m}\frac{u_n(x)u_n(x')}{k_m^2 - k_n^2}. $$ Show G_g satisfies the equation $$ (\mathcal{L} + k_m^2)G_g(x, x') = \delta(x - x') - u_m(x)u_m(x') $$ where \delta(x - x') = \frac{2}{\ell}\sum_{n =...

The generalized Green function is \[ G_g(x, x') = \sum_{n\neq m}\frac{u_n(x)u_n(x')}{k_m^2 - k_n^2}. \] Show \(G_g\) satisfies the equation \[...

Hi you all. I have to diagonalize a hermitian operator (hamiltonian), that has both discrete and continuous spectrum. If ψ is an eigenvector with eigenvalue in the continuous spectrum, and χ is an eigenvector with eigenvalue in the discrete spectrum, is correct to say that ψ and χ are always...

I had made a post in the past about the same problem and unfortunately I wasn't clear enough so I am trying again. I am studying an article and there I found without any proof that the solution of: Let ##g \in \mathbb{C}## and let ##u:(0,\infty)\to \mathbb{C}## $$ -u''+\lambda^2u=f\,\, on...

Hello everyone:(Please forgive my poor English.) I've been learning many-body theory for a year or so, however, I'm quite confused with different Green's functions (GF) there. One of the most things I want to get clear is about zero-temperature GF and imaginary-time GF (or Matsubara GF), both...

hello all ! my teacher told me to do a research on examples of problems that has connection with green function on solving differential equations (with programmed numerical solutions) in my final year project , can you give me such problems to work on as an undergraduate ? , thank you !

Homework Statement I would like to calculate the electric potential in all the space in the following set up: Conductor sphere of radius a whose surface is kept at a zero potential. 1 point charge ##q_1## at distance ##d_1## from the center of the sphere. 1 point charge ##q_2## at a distance...

Solve... \frac{d^2}{dt^2}G(t,t') + \omega^2G(t,t') = \delta(t-t') Solve (above) if G=0 and \frac{dG}{dt}=0 at t=0 to obtain: G(t,t')=\begin{cases} 0 & 0<t<t' \\ \frac{1}{\omega}\sin\omega(t-t') & 0<t'<t \end{cases} I'm supposed to use Laplace Transforms to figure this out. (I'm going out of...

Hi everybody. Does someone know the solution of the following differential equation in two dimensions: 1) \Big(\frac{\partial^2}{\partial\,r^2}+\frac{ \partial^2}{\partial\,z^2}\Big)G(r,z)=\delta(r-ro)\delta(z-zo) and 2)...

The solution of the problem \left(\nabla^2 + k^2 \right)\psi(\mathbf{r})=f(\mathbf{r}) is, using green function \psi(\mathbf{r})=-\int G(\mathbf{r},\mathbf{r}_1) f(\mathbf{r}) where for the tridimensional case the Green function is...

Hello there, I would like to obtain the Green function for the operator F, F [u(x)] = u '''', and the boundary conditions u(0) = u'(0) = u (1) = u' (1) = 0. I am looking for a function G ( x, s ) such that G'''' (x,s) = delta (x-s) (the apecis referring to differentiation w.r.t. x, and...

Hye everyone! An unknown thick-and-sticky green liquid was found leaked from 2 out of 9 feeders, of our 132 kV Switchgear. The liquid was leaked through the cable gland that connected to the Secondary Terminal Board insulating cap of the Current Transformer, at the GIS. I had done: 1)...

On the internet there is only information on how to get rid of the trianglethat indicates an error in the formula in the cell. But in my workplace I need to upload data to a program and sometimes a successful upload requires that the data in my excel cells be marked by this error-triangle...

Hello, Can anyone explain to me the next settence, found http://relativity.livingreviews.org/open?pubNo=lrr-2011-7&amp;page=articlese16.html in section 1.4: "The causal structure of the Green’s functions is richer in curved spacetime: While in flat spacetime the retarded Green’s function...

Why don't you support them? At least, statistically, you don't. If you do, then I'm equally interested in hearing why you support them. I find myself agreeing with them on a lot of the issues the more I look into them.

This being a physics forum, I'm sure many of you have heard of the 1998 computer game Half-Life. If you don't know, the game is set within a top secret research laboratory deep within the deserts and mesas of Arizona. All hell breaks loose after a massive screwed-up experiment. The...

Homework Statement The problem is attached in the first picture, the provided solutions are in the second.The Attempt at a Solution I got to where they are, but aren't they missing an additional term of sin(t)*cos(∏)*f(∏) from the second integral in dx/dt ?

will, Red, Green and blue lasers wen crossed create the spectrum we crossed ?? hia, if i get red, green and blue lasers, and cross them at one point, and change the intensity of each one accordingly, will at the point of where they cross, display different colours relevant to the mixture...

“Great Green Fleet” and $26/gal fuel http://www.foxnews.com/politics/2012/07/02/gop-in-congress-critical-navy-great-green-fleet/#ixzz1zX8phjVc?test=latestnews I'm surprised the navy pays as much as $3.60/gal for the fuel it normally uses. I would have thought it much lower. Don't they get a...

Hello, I'm a rising junior undergraduate physics major and I'd like to get some kind of green job in physics, maybe in alternative energy. I was wondering what kind of options are out there. I switched majors a few times from theater to environmental science to physics and decided to...

So I have a hilarious idea waiting to be exploded onto the world and I need a green light bulb. I have this bulb that is a 2.5V 0.3A incandescent bulb. I'm not entirely sure I know how to determine the type of base, but I could probably grab a micrometer and some diagrams and figure it out...

dear all, as a newbie in solid mechanics modelling, i always come across these few terms, Cauchy-Green strain tensor Green Lagrange strain tensor isochoric Cauchy green strain tensor. Consider a cubic, when we move the top face, while fixing the bottom face, we will able to see the...

If any group of people can help me with this interesting one it's you folks. So I hope most of you have seen that wonderful video of the ISS flyover of the Earth. In case you haven't for reference... Other than being blown away like everyone else something particular caught my eye, and after...

Assume we have a solid state hamiltonian, which is ellectrons plus nuclei plus all possible interactions: H = T_{el} + V_{el-el} + T_{n} + V_{n-n} + V_{n-el} Is it wrong to write down a self-consistent system of Green functions for electrons and phonons? G_{el}=g + gSG_{el} G_{ph}=g +...

i know what is green house effect but don't know whether there is any mathematical relation for finding the temperature rise due to green house? i am asking this because i am working on my college project on analysis of flat plate solar collector and want to calculte the correct values of...

Homework Statement I'm trying to self study Green function and I can't follow the very last step of a demonstration in an online notes (that I attach in this post). Page 7 to 8. Basically he says that from G_{tt}(t,t')+\omega G(t,t')=0 for all t>t' with the conditions G(t,t'+\varepsilon)=0...

I need yr help in Green theorem, please please please Dear Frends and Teachers, This is Issam, I'm really need your help to solve anyone of the following 2 questions as shown in attached files, it's about Green theorem on Abstract Algebra I'm really in critical time and I hope to get any...

In the green box in the paint doc it says " The motion diagram shows that the particle's acceleration points to the right... Umm what are they reffering to because it looks to me like the green arrows are pointing to the left...

Homework Statement Calculate the solution to \triangle u (r, \phi )=1 in a circle of radius a with u(r=a)=0. Homework Equations Green function I think, the exercise is listed with other exercises related to Green function. So even though separation of variables works here or any other...

Hey guys! So I'm reading Jackson's Classical Electrodynamics, and I'm trying to get a sense of what Green Functions really are. The book says that "the potential due to a unit source and its image(s), chosen to satisfy homogeneous boundary conditions, is just the Green function appropriate for...

Uh... what do I say now? Do I repeat it, like a dolt? Why do pedestrian crossing signals count down then the traffic light stays green?

If we have Green function g(x,s)=exp[-\int^x_s p(z)dz] we want to think about that as distribution so we multiply it with Heaviside step function g(x,s)=H(x-s)exp[-\int^x_s p(z)dz] Why we can just multiply it with step function and tell that the function is the same. Tnx for the answer.

Making your home more "green"? So we're closing on a house in about a week though we don't plan on moving in until the beginning of January. It was built in 1986 so it's not that old. The windows are fine (Except one in the garage), and we have to put more insulation in the attic. 2 -Story...

Taken from the BBC website - good news though :)

Hey, everyone. I'm new here. This is a continuum mechanics question. If it's the wrong forum, please let me know, of course. The question is pretty simple, but since I haven't been able to find an answer, I'm looking for "crowd help". Green strain \mathbf{E} is usually defined implicitly by...

More: http://news.yahoo.com/blogs/lookout/man-finds-150-000-garden-225554517.html I can't imagine it's anything other than drug money, but who knows. Anyway, I want to be next in line for such a find.

I am Looking for a green color molecule less than 3 angstrom in size... I have found Cr2O3 but its greater than 3.5 angstrom... so anything smaller will do the job :) Thanks in advance.

Please , can anyone recommend me to a reference containing Full proof of Green theorem. Thank you.

Homework Statement **The book I'm working from doesn't have solutions for even numbered problems and the two problems I'm about to show you guys are even, so if you guys don't mind, I would just like to know if I have the right concept, or if I messed up anywhere. I wouldn't have a way of...

Hi there. I have the next exercice: Verify the Green theorem with the field F(x,y)=(x+y,2x-y), and the path which its image is the boundary positively oriented for the region between x^2+y^2=9 y |x|+|y|=1 At first I've drawn this: Then I've parametrized the path...

When looking at my computer table, I notice that when i look at the glass from above it appears to be clear/transparent to all visible colors, but when I look at the edge of the table, the glass appears to be some kind of green color. Why does this happen, and why only this color?

Surely black would be better.

Seems odd there is a big hole in the spectrum between where they absorb red and blue light?

Hey guys, I'm wondering.. If I were to reflect a green laser pointer to the mirror, will the reflected laser be hot too? Or will I be heating the mirror?

So our continental guests expressed the desire to witness a maritieme sunset. And they certainly did not complain about our efforts to forfill such. This is what you only can hope for The sunset was exceptionally brilliant, you could not look directly in the sun for a long time...

Please teach me this: Why the electromagnetic potential obeys the Callan-Symazik equation in renormalization group theory like propagator functions.By the way,are there any relation between classical potential and interaction Haminton(the product of different field operators). Thank you very...

I've seen quite a few videos in youtube (like http://www.youtube.com/watch?v=woiTedSKPrk&feature=relmfu ) and I wonder why we can easily see the laser in the air, as if there was some diffusion of it in the air.