States Definition and 1000 Threads

Hello, I am a physics major and my friend is on a research vessel in the Arctic and can only operate email from the limited internet access there. I do not know organic chemistry so I was hoping someone could tell me if this was right (it is for homework when she returns; not in relation to her...

35g of h2o(g) at 380K flows into 300g of h2o(l) at 300K. Cp(l)=4.18kJ/K*kg and ΔH(condensation)= -2257kJ/kg. I need to calculate the final temperature when the system reaches equilibrium. Is the heat capacity for the h2o gas different than h2o liquid? Can you calculate heat capacity using...

I was watching some Steve Spicklemire QM videos and had a question/check my knowledge.. When we measure a the state of a system, say a particle in a box or a quantum harmonic oscillator (QSHO), we "collapse" the superposition of the system and end up with one eigenstate and one eigenvalue...

Is there any way to find the density of states from the IV graph

Homework Statement Two particles, their spin are 1/2. The hamiltonian is ##H=\gamma s_1 \cdot s_2## At t=0, the state ##|\alpha(0)>## is such as ##s_{1z}|\alpha(0)>=\hbar/2 |\alpha(0)>## and ##s_{2z}|\alpha(0)>=\hbar/2 |\alpha(0)>##. Find the state ##|\alpha(0)>##.2. The attempt at a...

Hey all, I'm reading through an anecdotal work about the philosophical foundations of quantum field theory and the authors keep referring to states having the ability to be "sharp." As in it's possible for P to be sharp if the system is mixed, where P is some property of the system. Thanks! IR

I'm doing some personal research on how matter interacts with radiation. Specifically, I am looking through the treatment of Bransden and Joachain. I've taken two semesters of quantum in the past (a while ago), but now I'm coming across something that I've either never seen or never stopped to...

Homework Statement Case, P[bar], T[C], v[m3/kg], u[kJ/kg], x[quality], State a) 1.5, ?, ?, 3000, ?, ? b) ?, 120, .6, ?, ?, ? c) 3, ?, ?, 2543.6, ?, ? d) ?, 190, ?, ?, 20%, ? e) 25, 100, ?, ?, ?, ? f) ?, 240, ?, ?, 0, ? Homework Equations We are supposed to use the steam tables in the back of...

All textbooks and material that I've read on the topic state that the deuteron being a weakly bound system, has no excited state. They also go on to state that the deuteron exists as a mixture of ##^3 S_1## and ##^3D_1## states. So, are these states degenerate in energy? That is, are both of...

Doesn't quantum teleportation show us that there are in fact at most 4 possible quantum states for a single qbit? I mean, you are guaranteed to reproduce the completely arbitrary and unknown teleported state by doing one of 4 possible operations with your side of the entangled pair. You can even...

Mesons: hadrons with integer spin, usually quark-antiquark states I came across this statement in a pdf of a powerpoint. Unfortunately the presentation is so badly formatted (missing images, content overlapping content, etc.) that it's hard to follow and I can't see if he ever describes mesons...

Hi, if we adopt the convention, a^{\dagger}_\textbf{p} |0\rangle = |\textbf{p}\rangle then we get a normalization that is not Lorentz invariant, i.e. \langle \textbf{p} | \textbf{q} \rangle = (2\pi)^3 \delta^{(3)}(\textbf{p} - \textbf{q}) . How do I explicitly show that this delta...

I'm a litte confused about spin triplet and singlet states. How do we know that for ↑↓+↓↑ the total spin S is 1, and for ↑↓-↓↑ the total spin S is 0? Also, how is total ms computed for these two states? (I understand that they are both 0, but not sure where that comes from) Thank you very much...

two questions: 1. besides using Ehrenfests theorem, is there another way of showing that the expectation value of momentum is zero in a stationary state ? (I don't see it when simply applying the definition on the stationary solution) 2. If we have a state that is a superposition of...

Hey! How are the two m=0 spin states (<up,down> + <down,up>) and (<up,down> - <down,up>) physically different? I realize that according to the math, the first one has a total spin of ##2 \hbar## while the second has a total spin of ##0##. But wouldn't you, intuitively, expect both states to...

Hi everyone! I'm a freshman in the Physics BSc at the university of Rome, and I've been reading here and there threads talking about courses, minors, majors and else, and I was just wondering how does this work, because I can't get out of my confusion while trying to understand it lol. In my...

I have some troubles in finding coefficients of superposition of states. I have 2 particles, their spins are s1=3/2 and s2=1/2. At t=0, the system is described by |a(0)>=|3/2, 1/2, 1/2, 1/2> I have to find |a(t)>. I have thought to proceed in the following way: 1) use the basis |s, s_z>...

Hello everybody. I'm interested in some problems of bound states in external fields in QFT (especially QED). I wonder are there any lectures/books or reviews which provide modern treatment of this subject? I would like to learn more about general formalism and applications in QED (I allready...

Can you please explain the difference between ground state and stationary state? In the stationary state, are the electrons at rest inside the atom?

Hoping this is in the right section! The module is nuclear and atomic physics but it crosses over into quantum occasionally. I've attached an image of the bit I'm trying to work out. I've got an exam on this topic in just over a week, so sorry if these posts get annoying, I have a feeling I'm...

In the U.S.A., states have been divided into red and blue. Who got to choose this? If I were a decider for a political party, I would want the "other guy" to be red. There have been notorious regimes that have had a red flag. A map with an increasing hord of red looks disturbing. Is there...

as you have learned about the states of matter in high school, there are three states of matter (just assume i know nth about plasma or any other things else first), and when change of states occur energy is supplied to the matter to increase its potential energy while keep kinetic energy...

I have been following a series of Leonard Susskind's lectures called 'Quantum Entanglements' (Part 1). In general, he explains how to find the probabilities of measurements of spin ½ particles' states, both single particles and pairs of them. I have learned the following: how to use the 2x2 spin...

Why can not the density of states of a metal at Fermi level be zero? Thanks!

The Purcell effect is when an atom placed inside a high finesse cavity with a very small mode volume gets an increase in the spontaneous emission rate. I've tried to find correct explanation for this effect, but it seems hard to find, except that it comes from an increase in the vacuum density...

Max Tegmark in his paper “Many worlds in context” http://arxiv.org/abs/0905.2182 Argues that …. .“Everett’s MWI is simply standard QM with the collapse postulate removed, so that the Schrödinger equation holds without exception”. He also argues that from this we can deduce that not only...

Homework Statement A quantum-mechanical harmonic oscillator with frequency ω has Hamiltonian eigenstates |n with eigenvalues En = (n + 1/2) ħω. Initially, the oscillator is in the state (|0> + |1>)/√2. Write down how the state of the oscillator evolves as a function of time t. Calculate the...

Dear all, In his book chapter " Green’s Function Methods for Phonon Transport Through Nano-Contacts", Mingo arrives at the Green's function for the end atom of a one dimensional lattice chain (each atom modeled as a mass connected to neighbouring atoms through springs). He gives the green...

It came to me just now that because we can always take the Fourier transform of a well-behaved function, this means we can think of any such state as a superposition of free-particle momentum eigenstates. E.g., the Hermite polynomial eigenfunctions of the harmonic oscillator. They have a...

If we have a system of two electrons, addition of angular momentum tells us that the spin states of the composite system can be decomposed into those of the two electrons as follows |1,1>=|+>|+> |1,0>=(|+>|-> + |->|+>)√2 |1,-1>=|->|-> |0,0>=(|+>|-> - |->|+>)√2 where the states are |s,ms> for the...

Homework Statement Homework EquationsThe Attempt at a Solution for ##r \le a## and ##l = 0##, the radial equation is $$- \frac {\hbar^{2}}{2m} \frac {d^{2}u}{dr^{2}} - V_{0} = Eu $$ $$- \frac {\hbar^{2}}{2m} \frac {d^{2}u}{dr^{2}} - [V_{0} + E]u = 0$$ call ##k^{2} = \frac...

I am trying to calculate the density of energy states in a two dimensional box. The way my professor did this is by first calculating the amount of states with their energy less than some energy e and taking its derivative with respect to e. In order to see how many energy states there are with...

Look at the following attached picture, where they prove the coherent states are eigenfunctions of the annihiliation operators by simply proving aexp(φa†)l0> = φexp(φa†)l0>. I understand the proof but does that also prove that: aiexp(Σφiai†)l0> = φiexp(Σφiai†)l0> ? I can see that it would if you...

Homework Statement A particle is in the state |\psi \rangle = \frac{1}{{\sqrt 3 }}|U\rangle + \frac{{a\sqrt {(2)} }}{{\sqrt {(3)} }}i|D\rangle . The up state |U\rangle = \left( {\begin{array}{*{20}{c}} 1\\ 0 \end{array}} \right) and the down state |D\rangle = \left(...

Hi, For the past couple of days I've been attempting to derive the equality (for any normalised ##\varphi##) ||(a+za^\dagger+ \lambda)\varphi ||^2 = ||(a^\dagger+\bar{z}a+ \bar{\lambda} )\varphi ||^2 + (|z|^2-1)||\varphi ||^2 First of the summation seemed like a typo. So I first tried to prove...

What is the value of ##\left\langle {{\bf{p}}|{\bf{p}}} \right\rangle ## when ##a_{\bf{k}}^ + k\left| 0 \right\rangle = \sqrt {2{E_{\bf{p}}}} \left| 0 \right\rangle ##? (like in Peskin) I suppose that ##\left\langle {\bf{k}} \right|{a_{\bf{k}}}{\bf{P}}a_{\bf{k}}^ + \left| {\bf{k}}...

In case you haven't come across it yet, there is a very informative overview of the history of physics education in the US, starting all the way from the 1860s. D.E. Meltzer and V.K. Otero, Am. J. Phys. v.83, p.447 (2015). It is 12 pages long, and covers some of the most significant movement...

if in a hydrogen atom the electron is in a excited state, is the net charge the same vs ground state? what is the difference between charge and energy here? thx

Homework Statement Recall the definition of the overlap of wave functions Φ and Ψ: [; (\Psi , \Phi ) = \int\limits_{-\infty}^\infty dx\: \Psi ^{*} (x)\Phi(x);] Let ψ1(x) and ψ2(x) be unit-normalised wavefunctions representing sharp-energy states with different energies (and hence zero...

Here is a thought experiment. Imagine Schrodinger's cat... in the traditional model, there is a single observer outside the box, and the observer creates an entanglement with the catbox device which reveals the quantum superposition of the enclosed cat. The cat is said to be in a superposition...

Hi there! As you might have already guessed, I'm referring primarily to the 'geometrical' difference (is there such geometry in Hilbert space?) between ##n##-dimensional state vectors | \psi \rangle = \left( \begin{matrix} \psi_1 \\ \psi_2 \\ \vdots \\ \psi_n \end{matrix} \right) and their...

Are all quantum states represented by normal vectors?

Hello! I know how to calculate band structure and density of states of photonic crystal (example is pic.1) Does anybody know how to plot such DOS maps? The second picture is from the article about photonic crystal fibers by Rodrigo Amezcua.

According to my thermo textbook the density of states should really be called the density of orbitals because "it refers to the solutions of a one particle problem and not to the states of the N particle system". This makes perfect sense to me but now I'm confused about references to the density...

Hello there, I am just starting quantum physics with the textbook by griffiths. My lecturer has told me that the set of functions representing stationary states in Hilbert space forms an orthogonal set. He was however unable to prove it. Furthermore he said that it is not always the case, but...

Hi. Look at the picture on 1:28 and 1:37 in this video: How is it possible that the fermi-level is between two energy bands? The fermi level is defined as the highest energy level that contains an electron 50% of the time, so how is it possible for the fermi level being in an area that is...

Homework Statement A system has two independent states ##|1\rangle## and ##|2\rangle## represented by column matrices ##|1\rangle \rightarrow (1,0)## and ##|2\rangle \rightarrow (0.1)##. With respect to these two states, the Hamiltonian has a time independent matrix representation...

Hello everyone. Can someone explains me the meaning of quantum state transition? For example consider an electron which is in the superposition of two energy eigenstates of a given hamiltonian, now, if no one perturbs the state with a measure, nothing happens and the superposition remains the...

Homework Statement Show that it is always possible to adjust measurement units such that a; b can be assigned any values you want. This means that e.g. all van der Waals gases look exactly the same if the units are accordingly adjusted. (This is what is called principle of corresponding...

It's known that the number of states in a band is equal to the number of unit cells in crystal. Here is my problem (confusion with trivial concepts) Bloch function is a electronic state, or orbital. The number of orbitals in a band inside the first zone is equal to the number os units cells...