States Definition and 1000 Threads

Hello all. I'm having trouble finding anywhere but my (unclear) lecture notes about the total number of states in a band. I'm getting a little muddled between my different models and am just wondering if the number of states in a band is equal to the number of atoms in the solid. In this case, a...

Hey, I've been looking into different aspects of distinguishing two pure quantum states. I've ended up reading a lot of books/papers covering things like "accessible information", but there haven't been too many explanations on how to find optimal measurements. The book by (Kaye, Laflamme...

Just to clarify - non equilibrium states in semiconductor means that the semiconductor is affected by external factors such as light?

The question is True/False. The answer is false, and I don't know why. All those oxidation #s seemed to make sense to me, and I couldn't think of any others. Any thoughts as to why that's not true?

http://www.nytimes.com/2009/08/26/business/economy/26deficit.html http://www.americanbankingnews.com/2009/08/25/white-house-predicts-1-6-trillion-dollar-deficit-in-2009/ If you need more stories then google it. (I posted the New York Times article because they're notorious for liberal spin and...

For those of you aspiring scientists and engineers in the United States, here arehttp://www.payscale.com/best-colleges/degrees.asp" . This is the kind of information I wished I had when I was in school, so I wanted to share. For those with a bachelor's degree alone [such as myself] the...

So, I'm doing some undergraduate research in quantum spin systems, looking at the ground states of the Heisenberg Hamiltonian, H=\sum{J_{ij}\textbf{S}_{i}\textbf{S}_{j}}. But I think I have a critical misunderstanding of some fundamental quantum mechanics concepts. (I'm a math major, only had...

I live in Wisconsin and I am looking for a wind tunnel where I can conduct a number of airfoil experiments. Since I am in high school, I am not yet affiliated with a university, so it is difficult for me to get in touch with lab technicians at universities. I have successfully contacted the...

Hello all, This may be my very first post on Physics Forums. I am a 1st year physics grad student and need some help on something that's been bugging me. Suppose we have two spin half particles in a bound state. The total spin will either be 0 or 1. The spin 0 state, for example, would be...

In quantum mechanics we learn that the states of a system described by eigen states which they are perpendecular. why should be this?

I was thinking about bound and unbound states the other day and want to know: Is unboundedness a requirement for a traveling wave? That is, if you were to build a beams from bound states, would they become standing waves?

A question for the more theoretically oriented forum users... but please feel free to suggest an answer to the puzzle anyways. In the book of selected works by Glimm & Jaffe, on page 4 (they discuss the massive scalar interacting filed in 1+1 dimension and give an overview of the divergences...

Homework Statement The ρ- meson has a charge of -e, a spin quantum number of 1, and a mass 1507 times that of the electron. The possible values for its spin magnetic quantum number are -1, 0, and 1. Imagine that the electrons in atoms were replaced by ρ- mesons. Select all of the following...

With normal I mean the age when most engineers receive their degree. I have a feeling that it is quite late compared to most other countries?

Hi, I would like to know what local density of states (LDOS) is and what differences it has with projected density of states? Also, when we choose a smaller isolevel we have a denser local densities of states, why? Regrds,

Hi. I've found the following relation (in a book about the qm 3-body scattering theory): <\Omega^{\pm}^{\dagger} \Psi_n|p>= ... = 0 where |p> is a momentum eigenstate. So it is shown, that the inner Product is zero. Then they conclude that \Omega^{\pm}^{\dagger}|\Psi_n> = 0 because the...

Hey all, My year 13 physics students stumped me with this one: Why don't Neutron-Neutron (or P-P for that matter) states exist? Thanks in anticipation... Mr T

1. Homework Statement [/b] There are N 3-dimensional quantum harmonic oscillators, so the energy for each one is: E_i = \hbar \omega (\frac{1}{2} + n_x^i + n_y^i + n_z^i). What is the total number of states from energy E_0 to E, and what is the density of states for E? The Attempt at a...

Homework Statement In most metals, the atomic ions form a regular arrangement called a crystal lattice. The conduction electrons in the sea of electrons move through this lattice. The figure (Intro 1 figure) is a one-dimensional model of a crystal lattice. The ions have mass m , charge e ...

Can someone link me some sort of article or journal that lays out the general process of preparing a mixed state of let's say an electron. I was curious as to how exactly you could know it is in one in the first place.

The epsilon delta rule states \epsilon_{ijk}\epsilon_{pqk}=\delta_{ip}\delta_{jq}-\delta_{iq}\delta_{jp} I am constantly using this but get stuck when it is applied. For example \epsilon_{ijk}\epsilon_{pqk}A_{j}B_{l}C_{m}=(\delta_{ip}\delta_{jq}-\delta_{iq}\delta_{jp})A_{j}B_{l}C_{m}...

I don't know how to distribute large amount of molecules(say a million) to many ro-vibrational states(say 100 states), according to the relative population of these states. As is very important when I want to simulate numerically the classical trajectory of these molecules in a spatially...

Homework Statement "Two non-interacting particles are placed in a one-dimensional harmonic oscillator potential. What are the degeneracies of the two lowest energy states of the system if the particles are a)identical spinless bosons b)identical spin-1/2 fermions? Homework Equations...

what are the classical counterparts of the quantum |nlm> states? in a isotropic potential. i am reading some books on Redberg atoms and i find this question not so trivial.

normalising \psi=|1,-1> is easy as \psi^*=<1,-1| and then \psi^* \psi = <1,-1|1,-1>=2 which gives \psi= \frac{1}{\sqrt{2}} |1,-1> for the normalised ket. but what about \psi=|1,-1>+2|0,0>+|-1,1> i get \psi^*=<1,-1| +2<0,0| + <-1,1| now I am guessing that seeing as i want to normalise...

Hi could someone please explain the what the bloch sphere representation of a quantum state is useful for? thanks Mark

Hi I am looking at Quantum Computation by Neilsen and Chuang at the CHSH inequality. Looking at the spin singlet state they make measurements of for example the observable Z1 and Z2-X1 and then find the expectation value of the product. I am slightly confused here because a) Z and X are...

For the state written as |u, d\rangle where u mean spin-up and d mean spin-down, I know that it is a state for a system which contains two spins: the first one is up and the other is down. But if I write the state as |u\rangle + |d\rangle What does this state mean? To me, I will...

Dear all, I really need help. My question: How do i project the density of states onto orbitals of atoms? this is to do a charge analysis. Can anyone provide me with an eqn or refer me to any relevant text or paper. Greatly apprieciate your help. Thanks nisha

At the top of page 26 here http://www.ph.ed.ac.uk/~pmonthou/Statistical-Mechanics/documents/SM7.pdf when we talk about "summing out" the states of all the other particles, why are we not summing over i_1 in the following sum - where did the i_1 sum go to?

I know there will probably be lots of disagreements with what I am about to say concerning the First amendment of the Bill of Rights, but I will just go ahead in say it: I don't think the founding fathers of the United states wanted the individual to decided whether s(he) wants to choose or...

Homework Statement How many bound states are there quantum mechanically ? We are told to approach the problem semi classically. Consider the Hamiltonian function H : R 2n → R (whose values are energies), and for E0 < E1 the set {(p, x) ∈ R 2n |H(p, x) ∈ [E0 , E1 ]} ⊆ R 2n ...

The current density vanishes for a bound state. I would like to know the proof and its physical significance. I appreciate the responses in advance!

Homework Statement In deriving the Markovian master equation for a weakly coupled system+environment scensario, we have \frac{\partial}{\partial t} P \rho(t) = \alpha^2 \int_{t_0}^t P L(t) L(s) P \rho(s) ds where \alpha is the coupling strenght, P\rho = \left( \mathrm{Tr} \rho \right)...

Some state lawmakers fighting federal stimulus http://news.yahoo.com/s/ap/20090302/ap_on_re_us/states_rights_stimulus It will be interesting to see where this goes. Some local prognosticator who publishes something called "Trends", has predicted the break up of the US. I'm sure he and...

solutions to the TISE for "unbound states" Hi! Suppose we have a step potential with boundary at x=0 V=0 for x<0 and V=V for x>0 Suppose V>E I guess I hot pretty far with this problem, I do have one doubt however: We obviously have two solutions: \psi _{I} (x)=Ae ^{ik _{1}x }+ Be ^{-ik _{1}x...

Suppose a particle is subject to a spherically symmetric potential V(r) such that V(r) = -V_0, V_0 > 0, for 0\leq r \leq a and V(r) = 0 elsewhere. If we were considering a non-relativistic particle, we would have bound states for -V_0 < E < 0 (which I understand); however, since the particle is...

As you could probably tell, my question is whether or not a superstring could exist with two different types of spin, if they have a spin at all?

calculate the density of states and average energy for an elctron gas in 1d,2d and 3d I know the number of states is N= \int_{0}^{infinity} g(e)f(e) de and E = \int_{0}^{infinity} g(e)ef(e) de and g(e) =dN/de

Hi every one this is the first time in this wonderful forum :) and i have a question i hope i find an answer ? how can the additiona of a smalll (c/r square)term to the coulomb potential removes the degnerecay of states with different (small) L. (quantum defect)? :confused: thanks

If I look at the energy of the hydrogen atom, the energy is proportional to the mass of the electron (or more precisely, the reduced mass). Does this mean that without a Higgs mechanism, there are no bound states of the hydrogen atom? (Or is it just an artifact of a non-relativistic theory that...

Hello, folks. Q: How can one measure the density of states of a semiconductor and a conductor? I would imagine you want to measure the charge carrier density and then you can calculate the density of states. If so, what observable(s) can yield the charge carrier density? How can you...

Does the quote below (from a textbook) make sense to anyone? The context is that they are introducing mixed states, and the quote below is how they refer to the pure states discussed in previous chapters. Here is the quote: "In quantum mechanics, such maximum information is contained in a...

Suppose you have a system which consists of a number of non-interacting particles in some potential trap. These particles are essentially identical; but each is in a different energy level (in a different energy eigenstate). Such a system is a completely mixed system (also called a 'mixed...

Homework Statement Consider the 3-D infinite potential well (length=L). The energy levels for this system are given by E=(h bar)^2\pi^2/(2ML^2)*(n(sub x)^2+(n(sub y)^2+(n(sub z)^2) There are 10 particles in this potential well. What is the lowest energy of this ten-particle state when the...

spacetime states in Rovelli's book "Quantum Gravity" happy new year everybody, I am reading "quantum gravity" of Rovelli. He introduces functions f(x,t) defined on compact of space time that are zero outside. They correspond to the time and space needed to a measurement. page 168: they...

For the composite system of identical particles only symmetric and antisymmetric states in the tensor-product (from the one-particle spaces) space are allowed to represent particles in nature. Why is that? Is it an experimental fact which is used as an input in the theory of many particle QM...

Hello, What is a quantum state? Put generalised functions/Schwartz distributions to one side, because a) they're not a Hilbert space, and b) they can't be multiplied, so it's hopeless to even begin to think about Feynman diagrams. One-particle quantum states seem to be fairly well...

Two Einstein solids are joined so that they can exchange energy. One contains N_A oscillators, the other N_B oscillators. Apparently, the possible number of quantum states of the combined system is given by, g(n,N) = \sum_{n_A = 0}^n g(N_A,n_A)g(N_B,n-n_A) where n is the principal quantum...

I am looking for resources about the values of undergraduate degrees in States. I mean by value the high quality of teaching and low tuition fees. I have found this site: http://www.ncf.edu/news/?p=868 , but I am unsure whether they apply to foreign students. Collegeboard.com shows that...