Exchange Definition and 262 Threads

i guess in the wigner crystal, the exchange interaction between the electrons can be neglected. What is your opinion?

I had some mildly not very nice words for a moderator on Stack Exchange. I tried to end a long conversation that we were having in the comments section in a cordial way. It was my fault for dragging it on so long. But his response just came across as condescending, so I told him that I didn't...

Imagine a block of wood resting on two supports at each end. You point a gun upward under the block and shoot the block upwards. One scenario is you shoot the block upwards in the exact center. Another scenario is you shoot upwards near one of the support ends. The block is thick enough that...

Consider the Feynman diagram below from, http://hyperphysics.phy-astr.gsu.edu/hbase/particles/expar.html where I assume time runs upwards and the gluon in the graphic runs horizontal and is labled as a green_antiblue gluon. If the gluon runs horizontal can one still label a gluon as being...

I know that the strong force is viewed as the exchange of virtual pions between two nucleons, with the mass and range of them confirmed by the energy-time uncertainty principle. But if the momentum of the pion is transferred from one nucleon to the other in the interaction, wouldn't that give an...

Hi guys, I'm looking for advice... I study physics and math (7th semester in a 9 semester program) and it's very likely that I get the chance to study abroad. The thing is it would mean at least an extra semester for me... Do you think it's worth the delay? Or I should graduate earlier and...

Photons are referred to as the field quanta for the electromagnetic field. I would like to understand how the exchange of field quanta such as photons can create an attractive force. For example, I can see that an electron could repel another electron by hitting it with photons...

I might be asking a question who's answer is way beyond my level but ill give it a shot. In QED, an electric or magnetic field is described in terms of exchanged photons, right? But if a photon itself is made of electric and magnetic fields... a paradox to my ill-informed brain. :mad:

Hi! Could you tell me the idea of using Jordan exchange for the Simplex Method?

Here's an alternative solution to solving the integral:\int_0^1\frac{\log(1+x)\log(1-x)}{(1+x)}\,dx[Original post: calculus - A challenging logarithmic integral $\int_0^1 \frac{\log(1+x)\log(1-x)}{1+x}dx$ - Mathematics Stack Exchange] I'll post a link on there so the OP can see my work...

Hi, I would like to ask about how the exchange rates are determined. I understood the concept of supply and demand, but my question is more technical than conceptual, i mean where is the information of the rates are coming from? Is there any center that keeps the track of, for example every...

In Quantum Mechanics, when we exchange identical particles the physics doesn't change. I wonder what stuff is conserved when this symmetry is demanded. I asked my professor but he didnt/couldnt answer. Google is no help either.

We are taught that a reason for the stability of half filled or fully filled orbitals is due to the high exchange energy. Now i get why the exchange energy would be higher compared to other configurations but i don't understand why electrons present in degenerate orbitals would want to exchange...

Why is the cation exchange always carried out before anion exchange in softening of hard water by ion exchange resins? Plz. Help:(

I wonder if there is any law for heat exchange. I have learned that heat exchange between systems occurs when the temperature of respective systems differ. But in case of evaporation, the process creates a cooling effect even in an isothermal condition ( I mean by isothermal condition to be a...

Anyone who trades in the stock exchange, can I get some advice on books, websites, or any other resource to learn the basics of investing? Also is there any general tips you could give me? Thank you :confused:

In the well known Ising model, without any external field (H=0), the energy (E), spins (s) and exchange interaction (J) are related as in the following equation $$ E = -\sum_{<ij>}J_{ij}s_{i}s_{j} $$ Jij is site dependent and consists of three components JAA, JBB and JABwhere A is say up...

Homework Statement A counterflow, concentric tube heat exchanger is used to cool the lubricating oil for large industrial gas turbine engine. The flow rate of cooling water through the inner tube (Di = 25 mm) is 0.2 kg/s, while the flow rate of oil through the outer annulus (Do = 45 mm) is...

This question was posed by algorithmshark and not yet solved on math.stackexchange.com: He has posted some thoughts on his question: real analysis - Evaluating $\sqrt{1 + \sqrt{2 + \sqrt{4 + \sqrt{8 + \ldots}}}}$ - Mathematics Various members (including myself) have shown this expression...

How would I calculate thermal exchange rate of Air for different amounts of humidity? I'd like to create a graph to show how much radiant heat air would absorb, (at some temperature (10°C) changes depending on the humidity amount, 0 - 100%

Sorry if this post seems short, I had to write it in a hurry. I'm currently reading Leonard Susskind's 'The Cosmic Landscape'. In it, he describes how electrons and protons both emit photons, which is what gives them their charge. The explanation is really awesome, but I have one thing I...

What is the deferences between Exchange and correlation and also what is Exchange-correlation hole?

I'm thinking of taking one of my semesters, autumn 2013, in China. I would need to take something equivalent to a statistical physics course while there, but most universities with a physics degree should have that. I'm a Norwegian and will be at the end of a bachelor if that has any relevance...

##\hat{c}_{i\sigma}=\frac{1}{\sqrt{N}}\sum_{\bf{q}}e^{i\bf{q}\cdot \bf{R}_i}\hat{c}_{\bf{k}\sigma}## ##\hat{c}^+_{i\sigma}=\frac{1}{\sqrt{N}}\sum_{\bf{q}}e^{-i\bf{q}\cdot \bf{R}_i}\hat{c}^+_{\bf{k}\sigma}## Then ##-J\sum_{i}\hat{S}_i^z\hat{c}^+_{i\sigma}\hat{c}_{i \sigma}## in...

Hi everyone, I realize this is only loosely related to mathematics, but I didn't know where else to ask this question (if I post it in a finance forum I'll get 100 different answers from people who probably didn't really understand the question). I think mathematicians are the kind of people...

Hi everyone, I'm working with quantum dot (PbS). However, I'm actually not a chemist, so could anyone help me to address some issues regarding quantum dots especially related to ligand exchange process. My questions are: 1. anyone can address about what kind of functionality (e.g: thiol...

Homework Statement An aluminum container with a mass of 400 g contains 200 g of water at a temperature of 18°C. After a block of iron at a temperature of 90°C is placed in the water, the final temperature of the mixture changes to 28°C. Find the mass of the iron, assuming that there is no...

I know there are many deep issues that come up in attempts to do quantum gravity, but I suspect that the following is not deep but easily explained by someone who knows more about this than I do. Suppose two neutrons are interacting gravitationally. The Feynman diagram that I would naively draw...

I know that the virtual exchange particle between two electrons is the photon and this explains why they repel each other (ie virtual photon is spontaneously emitted from one electron A causing it to recoil. As the virtual photon hits electron B, it imparts momentum causing it to move away so...

I am trying to calculate the amount of water that would have to pass through a 200 litre tank (water inlet temp is 20degrees c) in order to cool water by 10degrees in a closed loop (in a coiled copper pipe) suspended in the tank the coil has a total length of 30 lineal m and a diametre of 20mm...

I have recently started my phd on ab-initio simulations, and have several confusions about the calculations (lets say with a method like DFT) of solid crystal structures. 1. what exactly are the exchange and correlation phenomena. I have read texts and books which describe its physical...

Homework Statement Hi all! I was wondering in two Feynman diagrams (1 and 2) 1) in an electron positron annihilation two photons are created. Now, is the virtual electron the exchanged particle? I'm having problems understanding the diagrams. 2) A proton decays to a neutron as a...

How can I figure out how to calculate the heat/cooling exchange rate of water inside pex tubing? I want to build a ground source cooling system simular to a chiller system but I want a closed loop system. My game plan is to pump ground water into a holding tank that is constantly flowing ground...

Are ALL ligand exchange reactions reversible? Therefore, if the Kstab of one complex is LESS than that of the other complex, would it ONLY be possible to form the LESS stable complex by 'flooding' the mixture with the appropriate ion. (these values are not real but they illustrate what I...

I am trying to determine the expected heat exchange between flowing ground water in gravel/clay soil (that runs on top of blue clay) and glycol fluid in plastic pipe (1 1/4"). For my current interest, estimated ground water temperature of 60 degrees seems best. I am trying to determine the...

Homework Statement Multiply the following matrices Multiply A * B * C A = 0 0 1 0 1 0 1 0 0 B = 1 2 3 4 5 6 7 8 9 C = 0 0 1 0 1 0 1 0 0 The Attempt at a Solution Why not just exchange row 1 with row 3 and then you get an identity matrix and the answer will be 7...

Im reading through Griffiths' Intro to QM book right now, and I can't quite understand a statement he makes about the symmetrization of the states of identical fermions and bosons explaining the covalent bonding between two hydrogen to make an H2 molecule. The book says that (based on the...

Imagine a bell that has only 3 ideal resonant frequencies (no damping) and I am hitting it with a point like ideal hammer, does this mean that all of the energy of the hammer is distributed among those 3 resonances? I think not, i.e. the energy stored in the resonant modes are less than the...

Hi folk, I am new to electrochemistry and I am currently trying to find values for the exchange current densities of a range of pure metals. I have had some success from books such as the encyclopedia of electrochemistry of the elements, however I can't seem to find any values for chromium. Can...

Exchange splitting of energy levels of a system?? Hey guys, I was just reading my QM book and came across this; Homework Statement Determine the exchange splitting of energy levels of a system of two electrons, regarding the interaction of the two electrons are a perturbation. My...

Homework Statement A glass containing water is initially of temperature 20oC. The mass of the glass is 100 g and of specific heat 0.16 cal/g-co and water is of mass 200g. If 5 cubes of ice each of mass 15g will be added to the glass of water, solve for (a) The temperature of the mixture. (b)...

This is a simple problem. Picture a ball dropping from great height such that it reaches terminal velocity. Its KE will not increase anymore, but mgh is still being lost. That energy has to go somewhere. 1) My friend and I believe the energy is lost to heating the surrounding fluid (what a...

Homework Statement A 3 kg ball is dropped from a height of 0.8 m above the top of the spring onto a vertical coiled spring sitting on the floor. The spring constant of the spring is 1200 N/m. Determine the maximum compression of the spring as the ball comes momentarily to rest before rising...

I'm currently getting the paperwork done to request admission into an Erasmus exchange program. I've narrowed my options down to University College and Imperial College in London and Copenhaguen University in Denmark, as afaik they have the most reputable physics faculties with courses taught in...

Dear all, I need some help with Gaussian. I would like to know if it is possible to make cube file of the density of the single molecular orbital in Gaussian (not just overall or alpha and beta spin density) and if it is possible, wuold you be so kind to tell me how to do that? And also, is...

Hi, all. I'm wondering if anyone's done some simulation of magnetic material with LLG equation. The question is where can I find the value of exchange constant for a material. In LLG equation, the exchange constant is in the unit of "J/m", and the typical value is 10^-11 J/m, for some...

This is a rather general question but I'm studying for my thermodynamics final and wanted to clarify this topic. Is it possible for there to be a change in entropy in a cycle without a net exchange of heat into or out of the system? If so what may be some of the examples of this and how would...

I thought Gingrich's statements and demeanor helped him more than the Paul's and Romney's helped them. http://news.yahoo.com/blogs/ticket/yahoo-readers-rate-debate-10-000-more-people-044851269.html It's the third video as you scroll down the page in the section sub-titled "The Palestinian...

I would like to understand what is "exchange splitting" in atomic orbitals. For which orbitals does it happen ? Is there any similarity between this phenomenon and the Zeeman effect (which breaks the degeneracy on the magnetic quantum number and then splits the orbital into sub-orbitals having...

My question is about the energy exchange between gas particles and the walls of their container... If you consider a collection of gas molecules enclosed in a container, if the whole system is cooled (ie. like a balloon dipped in liquid nitrogen) as the gas particles collide with the inner...