Exchange Definition and 245 Threads

Dear Forum members! I'm wondering, what is an exact definition of the exchange energy in atomic physics and/or quantum chemistry ? For the best of my knowledge, the case is quite simple for correlation energy, namely E_{corr} = E_{exact} - E_{HF}, where E_{exact} is the exact solution of...

Hi all, I'm a phys junior in Spain thinking of doing my final undergrad year in another country in the EU, assuming I maintain my grant status in my senior year. My uni offers an exchange program at Copenhagen university which really caught my eye. There are many final year electives/grad...

I wondered about the photon exchange mechanism when my AP physics teacher taught about it. Essentially, it's like shooting a basketball back and forth. I don't see the attractive part, but's that what the analogy was on the internet thing used. I assume it's in the math, anyway. But my...

How does the exchange of virtual photons result in an attractive force (for example between a proton and electron)?

First, let me point out that this is probably wrong. Anytime I hear faster than light travel I am automatically skeptical. I just haven’t figured out why it’s wrong yet. Any ideas? 1. Two devices situated in between Bob and Alice produce two streams of entangled pairs of qubits. Each pair...

Hello, my name is William Moore; I am aspiring to be an Aero-Nautical/Aerospace-Engineer when I have completed my educational career. I would like to know, under what other branch of Engineering; is engineering alternative fuel sources?

I let the aircon cleaning crew wash my window airconditioner.. and after it was washed.. it is less cool.. maybe from a micro leak they caused. Bad. Anyway. I'm researching how aircon work and went to over a dozen sites. I'll summarize it thus and ask something. The compressor turns the...

Hi all, My university has an exchange program, and I am thinking to apply for it Some of the notable choices (in Europe) are: -ETH Zurich -EPFLausanne -TU Munich -TU Darmstadt -U Stuttgart -Utrecht -KTH -Chalmers I am a Physics Major (undergraduate) and do not speak any...

I'm struggling with the relation between particle exchange and parity with the case of para- and ortho-hydrogen. The overall wavefunction must be antisymmetric with respect to particle exchange and so for para-hydrogen (an antisymmetric spin state) the spatial part of the wavefunction must be...

The exchange operator P is hermitian--therefore it corresponds to some observable of the system. I've read on Wikipedia that this means "... we can, in principle, perform a measurement to find out if a state is symmetric or antisymmetric," but I have some doubts whether that is absolutely...

Hello everyone, This is my second year as a physics, math double major, and I am an international student (not in the US). For 2012 fall and 2013 spring (or maybe just fall, I don't exactly know the policies, but I know I can do it multiple times), I plan to go to UCB as an exchange student...

I am having some trouble understanding particle exchange symmetry and I'm working on the most basic problem with 2 spin-1/2 particles in a 1D infinite square well. I understand that a singlet state requires a symmetric spatial wave function and a triplet requires an antisymmetric wave...

If i have let's say have 1 cubic meter of water at a temperature of 23 degree, in a closest system connected to a 1 cubic meter of air of 20 degree, how long time does it take for the heat to balance out, the surface between the two a 1 square meter.

Looking thru some notes one this, I came across something which I can't get my head around. The Hamiltonian of the system (Helium atom) is H = H_1 + H_2 + W, the energies (kinetic and electron-nucleus) of electron 1, electron 2 and the interaction between the electrons themselves. To find...

Heat Exchanger? Greetings, after two days of testing my idea of using a stainless steel elbow as a heat exchanger and blowing the hot air into the shop does not work. On the plus side the gravity feed pellet burner works very well. I did find that considerable heat is radiating from the top of...

hi everybody, I´m a physics international student and i m planing to spent a year in a exchange program in the US. Most of the universities i have the possibility to go to are not very famous (at least i don't know very much about them ), so i would appreciate some help choosing the best ones...

I am going to modified the pristine montmorillonite (MMT) by using cationic surfactant. However I am confusing on the way to calculate the weight of the surfactant. I have been searching hundred of journals but couldn't get any information on how to calculate it. For example: MaterialsThe...

I've seen several posts with questions regarding transfer of energy and momentum through a gear box. Following is a problem I'm trying to work out but I clearly don't understand the physics involved: A flywheel with inertia of Ifw initial velocity of ωfwi = 10,000 rpm is connected (assume...

pan proto experientialism and the quantum exchange interaction. Would the quantum exchange interaction explain how (proto)experiences among particles are intimately shared to form what we perceive as an experience?

No-one on the general board seems to have an answer. I really would like help on this one. I am told that two static electrical charges exert a force on each other by the exchange of photons. Nowhere have I read the answers to the following: what are the frequencies/energies of the...

Hello Everybody, I am trying to understand the concept of symmetric and antisymmetric wave functions in QM. Now the Griffiths and other textbooks I have introduce the exchange operator as an operator that switches two particles in a given two particle wave function. But then an eigenvalue...

I have to pick the best cell culture vessel: For my experiments, the vessel initially contains 0% CO2. Then it's placed in an incubator set to 37 degreesC and 5% CO2. There is a 1 micron filter i can attach to a port in the vessel that can be 10mm wide or a .2 micron filter can be attached to a...

Homework Statement I have been working on a University Physics thermodynamics problem for over a week now, day and night. I've consulted two physics PhDs, posted on Yahoo Answers (nobody took the bait) and I'm still stuck. I just wasted an hour and a half carefully posting my problem and...

First let me apologize for any spelling mistakes as I am on a mobile device. Second I do have a few questions regarding thermodynamics for a project I would like to begin. 1) is there a way to calculate a volume of water in either the amount of time and the amount of energy required to make...

Homework Statement \int \frac {2+z^{-1}}{z^{2}} dz The Attempt at a Solution Let: u = 2 +z^{-1} du = -z^{-2} dz dz = -z^{2} du so now its \int \frac {u}{z^{2}} (-z^{2}) du \int \frac {(u)(-z^{2})}{z^{2}} du \int (u)(-1) du and then the...

Homework Statement \int \frac {1}{\sqrt{x}(1+\sqrt{x})} dx The Attempt at a Solution So let u = 1 + \sqrt{x} then du = \frac {1}{2}x^{-1/2} dx So dx should be this: dx = 2x^{1/2} du right? So now the Problem looks something like this: \int \frac...

Homework Statement Find: \int \frac {-1}{x^{2}(1+\frac{1}{x})^{2}} dx Homework Equations Same as before: \int f(u)du = F(g(x)) + C The Attempt at a Solution Let u = 1 + \frac {1}{x} then du = -\frac{1}{x^{2}} so \frac {-1}{x^{2}(1+\frac{1}{x})^{2}}...

Homework Statement This is only an example but I do not understand what they are doing... \int (4x+1)^{3} + (4x+1)^{2}+(4x+1) dx Homework Equations \int f(u) du = F(g(x)) + C The Attempt at a Solution Let u = 4x+1 then du = 4 dx and dx = \frac...

Homework Statement I was trying to work through some quantum physics questions and I was getting a bit confused. I know that for fermions the wavefunction must consist of spin and spatial parts of the fermionic wavefunction with opposite exchange symmetry (ie antisymmetric spin and symmetric...

Homework Statement Consider a collection of 100 oscillators, each with an average of 10 quanta. a) By what factor would \Omega(microstate) change if the total energy were increased by a factor of 2? b) By what factor would \Omega change if one more oscillator were added to the original...

Today in class, by the existence of an operator that exchanges the states of two indistinguishable particles, we attempted to derive the existence of fermions and bosons & how this relates to the symmetries of multiparticle wave functions. The argument given in my textbook is: define an...

Hi,all, I am wondering, momentum can expressed as energy, so: dxdP can expresses as dxdE ? then position, momentum, energy,time are all related, and they all form uncertainty relations?? in the view of commute the operators, all these four operators can NOT commute?? where am I...

derive Coulombs law of electrostatic force by using virtual photon exchange theory of electrostatic field

I have a motor I wish to evaluate. I wish to measure the Joules input and output. I believe I am making several errors. Right now I measure the voltage and amperage, calculate watts, and assume that for every second this wattage stays the same. So V*A*seconds = Joules input To...

Hi all, I've just returned from a trip to the US, California... Disneyland...Sequoia and Yosemite Nat. Parks. Incredible! While in Anaheim, I cracked several US $50's and $100's. I was provided with 10 x US $100's at a Sydney Airport currency exchange. I wanted to enhance my foreign...

Homework Statement In natural water containing 0.9 mmol/L calcium and 12 ug/L fulvic acid, determine the fraction of the fulvic acid that is bound to calcium (i.e. the ratio between the concentration of Ca-FA and total concentration of FA binding sites), assuming that calcium is the only metal...

Homework Statement Consider an ideal gas whose volume is initially V_0=1cm^3 that is initially at P_0=1 atmosphere. It goes through a cycle a-b-c-a where b-c is at constant temperature. 1)According to the sketch, does the system absorb or release heat? 2)Calculate the heat exchange in a...

Hi guys, I would like to ask for a few opinions on exchange to German for a Physics major degree. First, I like the German culture. And I would love to learn how Germany study science, especially Math and Physics. I wonder how much it will do for my studies? What is the best year...

Heat transfer is something I've been interested in since studying thermodynamics last semester, although during the course we never really covered anything much to do with what affected heat transfer. I can pretty easily understand that obviously having a higher surface area to exchange across...

how does the exchange coupling mechanism work that produce the ferromagnetic properties of materials?

Are exchange students, that are studying in the US for one year, allowed to enter the Putnam competition?

I(\vec{n}-\vec{m})=\frac{1}{N}\sum_{\vec{k}}I(\vec{k})e^{i\vec{k}(\vec{n}-\vec{m})} I(\vec{n}-\vec{m})=\frac{1}{\sqrt{N}}\sum_{\vec{k}}I(\vec{k})e^{i\vec{k}(\vec{n}-\vec{m})} In which cases is better to use first and in which second relation? N is number of knottes of lattice. And when I can...

Homework Statement You are given 2.5 102 g of coffee (same specific heat as water) at 70.0°C. In order to cool this to 60.0°C, how much ice (at 0.0°C) must be added? Neglect heat content of the cup and heat exchanges with the surroundings. Homework Equations Q=(m ice)(c ice)(delta T...

One of string theory's triumphs is the post-diction of a spin-2 field, which is supposed to represent gravity (GR). Yet, only in the weak field limit ("linearized") can it be shown that GR is a spin-2 field. So here's my question: why are string theorists confident that they have post-dicted...

What is it like to study engineering/technology in Japan? How about USA? I'm considering leaving Norway for a year of exchange, but I can't figure out where. I want to go to a good universiity without having to spend all my time studying.

Homework Statement The sun heats 2.00 x 10^2 kg of ammonia gas that is kept at constant volume in a large tank. Assuming that solar radiation of 6.00 x 10^2 W caused the heating, determine the length of time it took to raise the ammonia's temperature by 12°C. Homework Equations...

Homework Statement A block of steel dimension is 230mm*230mm*40mm=2,116,000cubic millimeters 0.00785 gram/cubic millimeters is the given steel density Using 180 degree celsius oil (density given is 0.9) to heat up the steel from 25 degree celsius to 110 degree celsius in a 10mm diameter...

Hi there, I am dealing with an inelastic, collinear momentum exchange of the form: m1v1+m2v2=m1u1+m2u2 where m1 & m2 are known. v1 & v2 are both 0 u1 & u2 are both unknown, however MOD(u1)+MOD(u2) is known (ie the sum of modulus of each speed, I don't know how to do straight...

Perhaps this is a bit of a naive question, but I'm having trouble with the following issue. It is easy to describe the motion of a test particle near a black hole using classical general relativity. The underlying assumption is that gravity is a geometric manifestation, and the orbits are...

Leaving the physics out of this, I'm working on an idea for an in home MHD generator. I'm trying to figure out a conductive fluid to use. I'm back to the idea of salt water, or H20 + NaCl. I know this is a very conductive solution, but I'm no chemist. What I plan to do is put a MHD generator and...