States Definition and 1000 Threads

I would really like to take a logic class, but I can only find philosophy classes that have logic. Have you ever taken a logic class with philosophy? If so, did it cover logic exhaustively? Do you know if there are any classes that have logic solely? If so, what was the course code for that...

I'm doing a project where I need a sensor to monitor a standard green LED and determine if it is ON, OFF, or BLINKING. I have been considering using a phototransistor or photodiode, but I am not sure how I would use one of these to tell the difference in the LED being on or blinking. Does...

Hey, there is something I don't really understand about the path integral (functional integral) formalism in QFT: Why do you need to introduce a coherent-state representation of the Dirac fields in order to evaluate their path integral? Where is the crucial point why it doesn't work like...

Homework Statement It is shown in the following two equations that any nonpure state operator can be decomposed into a mixture of pure states in at least two ways. Show, by constructing an example depending on a continuous parameter, that this can be done in infinitely many ways.Homework...

Towards the end of http://www.youtube.com/watch?v=IAgV-LKTiMI&feature=channel" video at 54:55, the professor defines the four possible states of two entagled electrons as follows: singlet |0,0> = |u,d> - |d,u> triplet |1,1> = |u,u> |1,0> = |u,d> +...

Homework Statement Give the full designation (e.g. 3P0) for all possible singlet, doublet, triplet and quartet S, P and D atomic states. The Attempt at a Solution I don't understand this question at all! Up to which values does the angular momentum (supscript) and multiplicity...

Is there any way of proving <p> = 0 for a discrete (bound) state given it's wave function? I've seen proofs using the hermitian properties of p but I'm interested in proving that the integral of Psi*(x) Psi'(x) is identically zero regardless of Psi(x) as long as it's a solution of Schroedinger's...

Principle stress states question, anyone help?? Homework Statement Neutron diffraction is used to measure the residual strains near to a weld in an aluminium plate. The aluminium has a young’s modulus E of 70GPa and a poisons ratio of 0.3. The three principal strains obtained are ε1= 2400 με...

This question is from an example taken from Zurek 1991 (Decoherence and the Transition from Quantum to Classical). Start with a spin state of an electron, \Psi= a|+> + b|-> Question 1: Why is this considered a pure state? I figured it would not be called "pure" since it is a superposition...

I would like some advise about what universities to apply to in the states for PhD programmes in physics. In particular what level of university (as defined by school rankings etc). I've been told that the high end universities can be overly stressful and that they foster a highly competitive...

Hi All, I am trying to remember the logical argument that leads from Heisenberg's uncertainty principle to the existence of quantum superposition states. Here's my sketchy version: 1) postulate of Quantization leads to non-commuting operators 2) This leads to Heisenberg Unc. Principle...

I was just wondering because it seems there is a contradiction in qm. If a quantum state can only be represented by an abstract statistic then would not gravity be equally subjective until decoherence occurs? And what about entanglement? It appears to act as a constant (an immediate one)...

Effing Virtual States -- How do they work? I want to talk to a scientist because this is pissing me off. >:-( So, I'm learning about CARS and Raman spectroscopy. Since Day 1 of Modern Physics I've been told that atoms have discrete energy levels and only the only way to get an electron from...

I'm pretty sure the answer to this will be more than obvious, but I've been wondering about the following. Isospin invariance is assumed to be an (approximate) symmetry of the strong interactions. Ratios of cross sections for strong interactions are then given by the appropriate SU(2)...

Hi, for my quantum mechanics course I'm confronted with the following question: Homework Statement A spin 1/2 particle has the following eigenstates of Sz: |+> = (1 0) and |-> = (0 1). A magnetic field is pointing in the z direction, B = (0,0,B). The Hamiltonian is H = -B * n, with n =...

Imagine viewing the world from state X at 1 pm, and viewing the world from state Y at 2 pm. State Y is required to be in existence in principle at the viewing of state Y, and at state X equally. This is because neither is more valid of a state to view the world from. Neither can claim it is more...

Homework Statement According to the non-relativistic quantum mechanics of a particle of mass m in a cubic box ov volume V = L3, the single particle energy levels are given by Ek=\hbar2k2/2m where k is the magnitude of the wavevector K = (kx,ky,kz) and where the components of k are...

This is too wild to post on beyond standard model but I am not proposing anything here. Just want to know your thoughts. Is it reasonably possible to conceive particles as solitons corresponding to metastable states of a unique universal matter field?

Homework Statement Suppose that a particle of mass m is confined to move in the x-y plane in a 2-dimensional box of length Lx = L and LY = ½ L. Calculate the energies of the six lowest states. Homework Equations not sure to set up this problem? The Attempt at a Solution the most...

Hi there, I would be most grateful if someone would explain how do we calculate the spin function χ(s_1,s_2 )=1/√2 [α(s_1 )β(s_2 )±α(s_2 )β(s_1 )] both the symmetric and antisymmetric α(s_1 )β(s_2 )+α(s_2 )β(s_1 ) = ? α(s_1 )β(s_2 )-α(s_2 )β(s_1 ) = ? knowing that α( + 1 / 2) = β(...

Since there have now been directly observed superpositions in laboratory experiments, meaning of course that superposition is not an interpretative issue but an observed aspect of nature, does this have any consequences for certain interpretations of QM? I particurlarly had in mind hidden...

regarding the density of states: how I GET THE FOLLOWING EQUALITY? \langle E_n\mid \delta(E-\widehat{H}) \mid E_n \rangle = \sum_n \delta(E-E_n)

Hi all. Is there any place where I can check how to derive the DOS of bilayer graphene subject to an external field. I have got the Hamiltonian right and solved the eenrgies but then I am not sure how to obtain the DOS right.. Thanks

Hi Why does Ni only form NiO with oxidation state of +2 whereas the other transition metals form a wide range of oxides with variable oxidation states Thanks

as we know when a particular energy is given to a neutral atom an electron from ground state jump to upper state (absorbing the energy). and that excited electron after sometime by releasing energy jump again to its ground state. my confusion is that firstly does this transition of electron...

given two arbitrary states of a spin of 1/2 we can always find a rotation to link these two states however, given two arbitrary states of a spin of 1 this is not so for example, (0,1,0) and (1,0,0) can not be linked by a rotation the former has vanishing expectations of sx, sy, sz so in...

Sorry if this question is very general/vague, but I would prefer a general answer rather than a specific solution... I'll put more detail in if necessary though. So, say we have a Hamiltonian for a system (of fermions, spin 1/2); then we find its eigenvalues and hence eigenstates. These are...

Hi everyone, I have the following question about coherent states: It is known that the creation operator has no eigenket. However, the action of a creation operator a^{\dagger} on a coherent ket |\alpha\rangle can be written as a^{\dagger}|\alpha\rangle = \left( \frac{\partial}{\partial...

What I know: In stationary states the time dependence is factored out so it is of the form phi(q) * e^(-i omega t), thus in its appearance there is no wave function spread. However I recall from texts that wave packet spread is considered a universal phenomena in quantum mechanics, so I am...

I can only imagine 3 states, the angular momentum adding constructively either in the positive or negative, or acting destructively. specifically what is the difference between the state with no total angular momentum and destructive angular momentum (singlet state) and the one with a positive...

Hi, I asked this question in the quantum physics forum https://www.physicsforums.com/showthread.php?t=406171 but (afaics) we could not figure out a proof. Let me start with a description of the problem in quantum mechanical terms and then try to translate it into a more rigorous mathematical...

Hi I am interested in the change in the stability of the oxidation states of manganese with pH Mn is a stronger oxidising agent in acid than in base which would lead you to believe that the higher oxidation states of Mn are more stable in alkaline conditions. Does anyone have a reason...

Hi, I discussed this with some friends but we could not figure out a proof. Usually when considering bound states of the Schrödinger equation of a given potential V(x) one assumes that the wave function converges to zero for large x. One could argue that this is due to the requirement...

Dear all, can you point me to a book reference where the hybridization states of the 8 orbitals (*) of Xe and Os in these 2 compounds \mbox{XeF_{8}} and \mbox{OsF_{8}} are justified in agreement with the quantum theory? Do these 16 bonds involve the "f" orbitals or not ? Thank you...

Homework Statement Find the wavelength of the radiation emitted when a hydrogen atom makes a transition from the n = 6 to the n = 3 state. Give answer in µm. Homework Equations z^2 / n^2 x 13.6ev delta E = E2 - E1 = hv The Attempt at a...

Homework Statement I have to show that the Fock states are eigenstates for the operators {{\hat{a}}^{\dagger }} and/or {\hat{a}} And I'm not totally sure how to show this. Homework Equations ? The Attempt at a Solution I know that if I use the operators on a random Fock...

Hi, Here's my problem, probably not that difficult in reality but I don't get how to approach it, and I've got an exam coming up soon... An atom with total angular momentum l=1 is prepared in an eigenstate of Lx, with an eigenvalue of \hbar. (Lx is the angular momentum operator for the...

Homework Statement I am trying to understand how we go about calculating the density of states in situations where the available quantum states are continuous, e.g. electrons in a white dwarf. I am happy to accept the uncertainty relation (we learned to derive it as the product of the...

Hi, when we consider an N-particle (assume non-interacting) system, say putting them in a box; why do we always say the states of the system (e.g. when counting them to find the "density of states as function of energy") are just the products of single particle stationary states (i.e. energy...

Homework Statement If the energy separation of two states is known for some atom, how can the same energy separation be calculated for the same two states for an ionized atom? i.e. if we know that the difference between the 1s^2 and the 1s2s states in Helium is something like 25eV, how could...

Hi all, I'm doing some test prep for a Nuclear Physics course and working on a past paper. I've attached a photo of the question. The diagram is 3.19 in Krane. The course is based on Krane, and so the relevant chapter is Chp 5: Nuclear Models. Problem description The problem is to explain...

Homework Statement The components of the initial state |\psi_i> of a quantum system are given in a complete and orthonormal basis of three states |\phi_1>, |\phi_2>, |\phi_3> by <\phi_1|\psi_i>=\frac{i}{\sqrt{3}} <\phi_2|\psi_i>=\sqrt{\frac{2}{3}} <\phi_3|\psi_i>=0 Calculate the probability...

i have two questions that i am struggling with and i have tried all i can think of with them and i am still not getting the answers correct. 1)Estimate, using the Uncertainty Principle, the kinetic energy of an electron if it were bound in the nucleus. Answer: ∼ 200 MeV for R ∼ 1 fm...

Can someone help me prove that tr(\rho^2) \leq 1 ? Using that \rho = \sum_i p_i | \psi_i \rangle \langle \psi_i | \rho^2 = \sum_i p_i^2 | \psi_i \rangle \langle \psi_i | tr(\rho^2) = \sum_{i, j} p_i^2 \langle j | \psi_i \rangle \langle \psi_i | j \rangle Where do I go from here? Thanks guys.

If I have SO42-, I can figure out that the oxidation state of each O ion is 2- and the sulfur ion must then be 6+. What does this number mean? What does it tell you about the electrons in that molecule?

Homework Statement Explain why 2-bromopropane reacts with NaI in acetone over 10^4 times faster than bromocyclopropane. (Hint: examine the transition state for each of the reactions) Homework Equations The Attempt at a Solution I understand this is a sn2 type reaction and...

Homework Statement Give the number of states (energy of the state smaller than E<0) \Phi(E) of a spinless particle with mass m in the central potential V(\vec{r})=-\frac{a}{\left|\vec{r}\right|}. Homework Equations The Attempt at a Solution Hi, the hamiltonian of this problem...

When in history did we go from the States being sovereign and over the Federal government to the Federal government being sovereign and over the States? The founders like Jefferson, Adams, Hamilton, Marshall and Webster all understood the States as sovereign with the right to secede.

It'd be great if you could help me clarify a few things in my head. Firstly I've got written in my notes "quantum mechanics forbids spontaneous transitions from one energy level to another because energy eigenfunctions are time independent". However this seems a bit of a circular...

Hi guys In some articles I've read, they all mention that the (local) density of states is related to the retarded Greens function for a non-interacting system by -(1/π)Im[G(r,ω)] = LDOS(r,ω), i.e. the imaginary part of the Greens function. The above relation holds because in k-space the...