State Definition and 1000 Threads

Can someone explain the meaning of the k vector and the general meaning of this equation?

Homework Statement [/B] Estimate the lifetime of the excited state of an atom whose natural emission line width is 3.00 × 10−4 eV. Homework Equations $$ \Delta E \Delta t = \frac{1}{2} \times \frac{h}{2\pi} $$ $$ \Delta E \Delta t = \frac{h}{2\pi} $$The Attempt at a Solution I think all I...

Hi there. I am working on some exercises where they ask about the steady state of a pendulum. I have had quantum mechanics, where the steady state meant a time independence. But I don't really see what this means for a pendulum. Is it steady when it's velocity is zero so there is no time...

Biohackers are mostly "amateur" molecular biologists who (often) want to make new things through genetic engineering. They have been developing their methods and on-line communities. Here is a fairly long NY Times article that gives some background and discusses different sides of regulatory...

There are two types of finite state machines (at least that I know about), mealy and Moore. What are the practical differences between them. I understand that mealy machines take the input into account for the output logic, but are the two machines used for different purposes? Or can the same...

Homework Statement One end of a solid cylindrical copper rod 0.200 m long and 0.0250 m in radius is inserted into a large block of solid hydrogen at its melting temperature, 13.84 K. The other end is blackened and exposed to thermal radiation from surrounding walls at 500.0 K. (Some telescopes...

How does one determine the state of a system from observations? Let us look at a simple example: the spin of a fermion. Any state of the system is a superposition of up and down eigenstates. Denote the coefficients in this superposition by a and b. The question here amounts to determining a...

Hello! If the Library of Babel has 10^(2,000,000) books, does anyone think that it is possible to create a quantum state (with a quantum computer) that represents this Library? I think that in a classical way it is impossible, but in a quantum way? I find it quite interesting! What about you? :)

Homework Statement Considering the molecule of ##C_2^+## in an excited state with valence configuration ##2\sigma_g^2## ##2\sigma_u^2## ##1\pi_u^2## ##3\sigma_g^1##. Finding all the possible term symbol. Homework Equations Term symbol ##^{2S+1}\Lambda## ##L=0 \rightarrow \Sigma## ##L=1...

In Zettili's Quantum Mechanics, page 477, he wants to determine the energy and wave function of the ground state of three non-interacting identical spin 1/2 particles confined in a one-dimensional infinite potential well of length a. He states that one possible configuration of the ground state...

Homework Statement I have derived the differential equations of a system. They are like the following: a\ddot{\theta} - b\ddot{x} + c \theta = 0 \\ d\ddot{\theta} + e\ddot{x} = F(t) where a,b,c,d,e are constants. I'm having trouble putting it into state space form, since I have the highest...

Hi. I have read somewhere that cubic equations of state seem to have convergence issues when vapor pressure calculations are done near the critical point. Sadly, I have forgotten where I have have read it :( I would like to ask some knowledgeable people regarding this, or can people point me I...

im curious as this question came up in a chemistry forum and it's more of a physics question I believe . State changes between elements of near similar number , what constitutes the extreme phase changes ? It was answered that there is no real answer for why the phase differences occurs at...

Homework Statement Calculate the output function and draw a graph of output voltage in the function of the input voltage of the following digital circuit: Homework Equations 3. The Attempt at a Solution [/B] By analysis of what happens when inputs A and B are on the logical "1" i have...

Homework Statement If possible could someone have a look at my working for this problem, I am not sure if I have carried out part b) correctly. I have done all three problem and carried through my solution to b) just to see if it did simplify out, which it didn’t which make me think I may have...

Hi physicsforums, I am an undergrad currently taking an upper-division course in Quantum Mechanics and we have begun studying L^2 space, state vectors, bra-ket notation, and operators, etc. I have a few questions about the relationship between L^2, the space of square-integrable complex-valued...

Actually while studying the inflation phenomenon the transition of the slowly rolling scaler field from from the false vacuum to true vacuum state to a more classically stable state I actually didn't understand this transition from false vacuum to true vacuum and what actually they mean? Another...

Okay, so I've been set this homework to find the normalisation constant, N, for the radial wave function in the 2s state for hydrogen (my title was too long to fit that vital information in). thing is; I'm having a bloody hard time and in the process confusing myself with trying to take out all...

What exactly is the so-called "Ground State Lamb Shift". It seems to have been an 'in vogue' quantity up till 1995 or so - then vanished from the literature ?? It's the 'self energy' or something like that of an electron in H 1S orbital. A scientist (at NIST) told me it's a term that has gone...

If the universe was in an energy eigenstate then d<A>/dt = 0 for any dynamic variable A. Stuff moves which implies that the Universe isn't in an eigenstate. What factors drive the energy spread?

So if string theory is to be correct it must be able to come up with the observed value for the energy density of empty space which is pretty close to zero? A naive understanding of the compact spaces of string theory tells me that an "energy audit" of the highly curved compact manifolds of...

I am having a doubt that if Id lho potential is Given of the form λ2px2/2m+.5kx2 then whether the ground state energy of the system is λ2/4ħω+1/4ħω

Homework Statement Show that any plane wave can be written as the sum of a left-circularly polarized wave and a right-circularly polarized wave of suitable amplitudes and phase Homework EquationsThe Attempt at a Solution If I assume the plane wave polarizes in the z direction. It is possible...

Hi all, There is this question; Firstly, I am new to quantum mechanics and there are a lot of terms I am unfamiliar with. So there is this question that asks me to develop a method to reconstruct state and I have no clue how I should start with. Any help or steps to solve this type of...

I've heard that the average homeowner in the state of Massachussetts (MA) pays about $15,000 in state property taxes per year. I believe that the standard deduction on Federal income taxes is $6,400 per year. State property taxes can be itemized on Federal income taxes. It seems to me that...

how to calculate , oxidation state of polyatomic ions like " acetate" C2H3O2 2(4)-3-4= +1 ? how do we know when carbon or hydrogen are sharing x electrons

Homework Statement For the state ##(4|00\rangle+3i|11\rangle)\otimes (|0\rangle+i|1\rangle) + (2|01\rangle -i|10\rangle)\otimes(|0\rangle-|1\rangle)## What's the probability of zero being the outcome of measuring the second bit and what is the state of the other two qubits after measurement...

Definition 1 The von Neumann entropy of a density matrix is given by $$S(\rho) := - Tr[\rho ln \rho] = H[\lambda (\rho)] $$ where ##H[\lambda (\rho)]## is the Shannon entropy of the set of probabilities ##\lambda (\rho)## (which are eigenvalues of the density operator ##\rho##). Definition 2 If...

[Update December 2021: This is an old thread. I updated it to add a factoid (go to the last post).] I’m on the road again, this time to Florida. Meet a couple of friends of mine in Harlem, Georgia...

I've been reading these notes: http://www.vcpc.univie.ac.at/~ian/hotlist/qc/talks/bloch-sphere-rotations.pdf And on slide 11, to check what the rotation operator is doing, the state is pre- and post-multiplied by the operator so that the calculation performed is ##\rho' = R\rho R^{\dagger}## Why...

There are few thing I'm not sure of and be happy for clarifications. In general: at steady state, what are the electric-field,potential, and current boundary conditions between a conductor and a dielectric medium? more specific: a) When dealing with a perfect conductor there exist a surface...

New to set and graph theory and need help on how to approach these exercise questions: For each of the following relations, state whether the relation is: i) reflexive ii) irreflexive iii) symmetric iv) anti-symmetric v) transitive Also state whether the relation is an equivalence or partial...

Homework Statement Is the statement ”Given a two-fermion system, and two orbitals φ labeled by quantum numbers a, b, the two-body wavefunction (1,2 represent the particle variables) $$\psi(1,2) = \phi_a(1) \phi_a(2) - \phi_b(1) \phi_b(2) + \phi_a(1) \phi_b(2) - \phi_b(1) \phi_a(2) $$...

Bondi K-Calculus very depend on who was send the signal. If two twin A and B make a journey, A send a signal and B receiving the signal then yes after the journey A will see B younger, and this applied too for the case B sending a signal and A reflecting, then after the journey A will younger.

Homework Statement Given the following Hamiltonian: And the observable: Calculate the probability of measuring any of the possible values of A in the fundamental state. The attempt at a solution I have calculated the eigenvectors and eigenvalues of the Hamiltonian, being the eigenvalues...

Homework Statement First sorry for the traduction mistakes. Prove that any wave function of a particle in a 1 dimensional infinite double well of width a, returns to its original state in time T=4ma2/(πħ) . Homework Equations Ψ(x,t)=∑cnψn(x)·exp(-i·Ent/(ħ)) En=n2π2ħ2/(2ma2) The Attempt at a...

Homework Statement Homework EquationsThe Attempt at a Solution This is a solved example in my Physics textbook . I don't understand how this problem can be done without specifying the battery VBB in the Base Emitter loop . The author assumes that the 20 V battery is connected between both...

Hi. My question is a general one but I will use an infinite well as an example. Without knowing details of the exact wavefunction I presume it can exist as a linear superposition of an infinite number of energy eigenstates ? Without knowing the exact wavefunction ; does that mean that when the...

Every year since the 90's I come back to some of my pet topics in physics, like statistical physics. This time it was the reading of a Wikipedia article on entropy that surprised me. The derivation of the second law from the Gibbs entropy was unknown to me. I didn't know how heat, how change of...

A free scalar field with Lagrangian density $${\cal L}=\frac{1}{2}g^{\mu\nu}\partial_{\mu}\phi\partial_{\nu}\phi$$ has the energy momentum tensor with the equation of state ##p=\rho##, i.e. ##w=1##. The Lagrangian density above is a very natural Lagrangian, yet the equation of state ##w=1##...

I'm working on an assignment where I'm required to numerically find the energy of a delta-potential's bound state. To do this, we've converted the time-independent schrödinger equation to an eigenvalue problem with E the eigen value, ψ the eigen vector and H a matrix as follows: with ##t =...

A question I have faced in exam to calculate ground state energy Given Hamiltonian 1/2m(px2+py2)+1/4mw2(5x^2+5y^2+6xy) ground state energy has to be obtained Its clear that the Hamiltonian is a 2D LHO Hamiltonian but what for the term 3/4(x+y)2

1. Problem Statement Find the steady state output yss(t) for the input u(t)=t-π in terms of an infinite sum of sinusoids. We are given the transfer function as: 2. Homework Equations G(i) = ... |G(ik)| = ... Φ(ik) = ... (this is the angle) yss(t) = βk||G(ik)|ei(kt+Φ(ik)) ***check that this...

Hello, Suppose that the angular momentum of a system can take the values 0, 1, 2. One carries out a measurement of ##J_z## on this system. What can be said about the state of the system after the measurement? To what extent can it be perfectly certain if ##J_y## and ##J_x## do not commutate...

Homework Statement I am trying to understand what the difference in the two questions (linked) are. I understand how to find the steady state response for x. Is the second question just asking for the first and fourth element in the Xss matrix? Homework Equations Xss=[q1 q2 q1dot q2dot] The...

I am trying to read through this paper discussing what quantum fluctuations mean in their various contexts, particularly in de Sitter space. I have come across this passage and am curious to what it actually means? https://arxiv.org/pdf/1405.0298.pdf pg. 10, second paragraph: "If a quantum...

Homework Statement The coefficient of thermal expansion and isothermal compressibility of a gas are given by ##\alpha_P =\frac{V-b}{TV}## and ##\kappa_T = \frac{V-b}{PV}## find: a) The equation of state b) If the heat capacity at constant volume ##C_V## is constant, what is ##\delta U##? c)...

What methods other than Light Dependent Resistor incorporation are there to determine the 'bulb state'? I'm guessing it's going to include the use of another type of optoelectric component? Thanks

Homework Statement A hydrogen atom is in the 7f state. What is the magnitude of its orbital angular momentum? Homework Equations L=sqrt(L(L+1)hbar The Attempt at a Solution L= Sqrt(3(3+1)Hbar) 1.41hbar (we want J*S) 1.41*1.054*10^-34 1.47*10^-34J*S

1. The problem statement Consider a particle of mass m under the action of the one-dimensional harmonic oscillator potential. The Hamiltonian is given by H = \frac{p^2}{2m} + \frac{m \omega ^2 x^2}{2} Knowing that the ground state of the particle at a certain instant is described by the wave...