State Definition and 1000 Threads

Homework Statement I am always confused about how to correctly write the functions U, H, F, G when they're not depending on the usual variables p, V, T, S - same question for Q and W. For example, we have to calculate the temperature variation of a small surface of water when we isentropically...

why ##\ln(\frac{V}{Nλ^3})## Equal to ##\ln(E^{3/2})##? so ##E^{3/2}=\frac{V}{Nλ^3}## ? i think ##λ∝\frac{N^{1/2}}{E^{1/2}}## and ##E^{3/2}∝\frac{N^{3/2}}{λ^3}##

Can anyone tell me, What quantum state really is? Is it applicable for all sub atomic particles? Then, Can anyone explain how two electron are never in same quantum state. And Does proton or neutron follows the same law as electron for obtaining unique quantum state.

Homework Statement [/B] (Working through a problem from a practice set for which I have a solution available, but still don't understand. I get the same answer as they do for part a, but get lost in part b, I think. Relevant portions below) Consider a two-state quantum system. In the...

Sir Roger Penrose in his book Cycles of Time on page 19 states the result of a calculation of probability of mixing red and blue balls as an illustration of entropy as state counting and the Second Law. He assumes an equal number of each. There is a cube of 10^8 balls on an edge subdivided into...

Hi, there's no particular question I need help on - just a few things I need clarifying. To determine the max shear stress, I know max shear stress = (max normal stress - min normal stress)/2, but are these equations true for a 3D stress state? (please look at attached image) Thank you

Hello, The state | W \rangle = \frac { 1 } { \sqrt { 3 } } ( | 001 \rangle + | 010 \rangle + | 100 \rangle ) is entangled. The Schmidt decomposition is : What would the Schmidt decomposition be for | W \rangle ? I am also intersted in writing the reduced density matrix but I need the basis...

MODERATOR NOTE: NO TEMPLATE BECAUSE THREAD WAS ORIGINALLY STARTED IN NON-HOMEWORK FORUM I'm struggling with a question on an assignment about thermodynamics: Nitrogen gas, initially at a temperature of 170 K and a pressure of 100 bar, escapes from a thermally isolated tank with a volume of...

Dear all, I am aware that a weakly driven dipole can be modeled as a damped driven simple harmonic oscillator. If I have to model the dipole as being driven by a classical monochromatic electromagnetic wave, would the corresponding simple harmonic oscillator then be in coherent state ? In...

Homework Statement So in my problem, there's a given of 3 non interacting fermions in a harmonic well potential. I already got the wavefunction but i have problems in obtaining the ground state energy and its 1st excited state energy for 3 fermions (assuming they are non interacting and...

When I was an undergrad doing research in a university lab, the director of the lab also consulted at a Nuclear Fusion company. I remember like it was yesterday him making a statement that commercial Nuclear Fusion was going to be a reality within 10 years. That was 1977. What happened? Lack...

Homework Statement One way to establish which transitions are forbidden is to compute the expectation value of the electron’s position vector r using wave functions for both the initial and final states in the transition. That is, compute ∫ΨfrΨidτ where τ represents an integral over all space...

Sorry if that title doesn't match up well with my question. I think it captures roughly what I'm wondering about. My uncertainty is to do with how much of mathematics is certainly true. Like, if I picked up any undergrad or grad textbook in mathematics, would everything in it be true based on...

Homework Statement Let ##U_t = e^{-iHt/\hbar}## be the evolution operator associated with the Hamiltonian ##H##, and let ##P=\vert\phi\rangle\langle \phi\vert## be the projector on some normalized state vector ##\vert \phi\rangle##. Show that $$\underbrace{PU_{t/n}P\dots PU_{t/n}}_{n\text{...

Hello, I don't understand how can electrons in triplet state can have the same value of spin? Shouldn't the spins be different because two fermions can't have the same state? The following picture explain my question in more detail.

Homework Statement Let ##\vec{e}\in\mathbb{R}^3## be any unit vector. A spin ##1/2## particle is in state ##|\chi \rangle## for which $$\langle\vec{\sigma}\rangle =\vec{e},$$ where ##\vec{\sigma}## are the Pauli-Matrices. Find the state ##|\chi\rangle## Homework Equations :[/B] are all given...

Homework Statement In the circuit shown, C1= 1 microfarad, C2=3 microfarad, in steady state, the energy stored in these capacitors are? Homework Equations Kirchoff's laws, E=0.5CV^2, V=IR The Attempt at a Solution At steady state, no current passes through the capacitors, so current is...

I’ve seen the uncertainty principle used to calculate the ground state energy for things like hydrogen and the harmonic oscillator, but can this be done for the Yukawa potential where you have an exponential?

If I diagonalize the hamiltonian matrix ,I can get the eigenvalues , does the smallest eigenvalue always be the ground state energy?

Hey guys, I am looking for a database on gamma emission from the first few excited states of known isotopes for a piece of software we are putting together. Any format is fine. Thanks!

Homework Statement An electron in a hydrogen atom falling from an excited state to the ground state has the same wavelength than an electron moving at a speed of 7821 ms^-1. From which excited state did the electron fall from? Homework Equations I used the kinetic energy equation: K = (m...

Hi good day. I am trying to find the general Inverted Pendulum on a cart nonlinear state space equations with two degrees of freedom with x, x_dot, theta, theta_dot which represents displacement, velocity, pendulum angle from vertical, angular velocity. However from research, I am seeing...

Can anyone post here quotes from academically validated physicists that state outrageous facts? I realize that Bohr said that if one isn't shocked by QM one doesn't understand it. But I am looking for something more specific. For example a quote about superposition , entanglement etc. The idea...

Is it possible to expand a state vector in a basis where the basis vectors are not eigenvectors for some observable A? Or must it always be the case that when we expand our state vector in some basis, it will always be with respect to some observable A?

The figure below is from a textbook. It is explaining what excited states are using carbon as an example. I don't necessarily agree that the the state labeled as "example excited state 1" is really an excited state. Since the electrons in the 2p orbitals are unpaired, and in the absence of a...

Every derivation from the MWI of the born rule is circular. http://fmoldove.blogspot.com/search?q=MWI So my question is, can the MWI state the born rule as a postulate (without deriving) and still be a coherent interpretation of probability? The most famous argument against this notion is by...

Homework Statement How should I calculate the expectation value of momentum of an electron in the ground state in hydrogen atom. Homework Equations The Attempt at a Solution I am trying to apply the p operator i.e. ##-ihd/dx## over ##\psi##. and integrating it from 0 to infinity. The answer I...

Homework Statement For the given circuits, identify state variables and derive a state-space model for each. Assume the input is v(t) and the output is vL(t). Homework EquationsThe Attempt at a Solution [/B] So my issue is that I solved this problem using two different methods. First...

For the half harmonic oscillator the ground state wave function is of the form x*exp(-x^2/2) But sir how to check it's parity and with respect to with point As this function is valid for positive x only Thank you

Homework Statement The ground state energy of 5 identical spin 1/2 particles which are subject to a one dimensional simple harkonic oscillator potential of frequency ω is (A) (15/2) ħω (B) (13/2) ħω (C) (1/2) ħω (D) 5ħω Homework Equations Energy of a simple harmonic oscillator potential is En...

Homework Statement [/B] A particle of mass 'm' is initially in a ground state of 1- D Harmonic oscillator potential V(x) = (1/2) kx2 . If the spring constant of the oscillator is suddenly doubled, then the probability of finding the particle in ground state of new potential will be? (A)...

Imagine a two-state system, e.g., a single nucleus that can be aligned or anti-aligned with an external magnetic field. If that nucleus is in a "mixed state" at time zero, such that it's wavefunction is 50% up and 50% down at time zero, why can that nucleus absorb a "quanta" of radiofrequency...

Homework Statement Is the following matrix a state operator ? and if it is a state operator is it a pure state ? and if it is so then find the state vectors for the pure state. If you don't see image here is the matrix which is 2X2 in MATLAB code: [9/25 12/25; 12/25 16/25] Homework...

In the four-observation method of Gauss for orbit determination, the right ascension and declination of an asteroid is observed at specified times, and the heliocentric position of Earth is obtained from tables (or JPL Horizons) for those same times. I can follow the procedure to the point...

I start by outlining the little I know about the basics of quantum field theory. The simplest relativistic field theory is described by the Klein-Gordon equation of motion for a scalar field ##\large \phi(\vec{x},t)##: $$\large \frac{\partial^2\phi}{\partial t^2}-\nabla^2\phi+m^2\phi=0.$$ We...

I know that Bragg reflection in solid states at the edge of e.g. the first Brillouin Zone causes standing waves at these edges, which creates a gap between the energy bands. In this picture below you can see the probability density of a symmetric (+) and anti-symmetric (-) standing wave. The...

Hi. Please excuse my ignorance but this entire volume translation formulas for EOS confuses me to no end. Could someone tell me how the volume-translated Peng-Robinson exactly works? How do I calculate the fugacity expression of VTPR? Do I integrate the V + c terms against dV or do i integrate...

In the last paragraph of these notes, https://ocw.mit.edu/courses/physics/8-04-quantum-physics-i-spring-2016/lecture-notes/MIT8_04S16_LecNotes3.pdf, it says how a state with large number of photons is not classical. Why is that? I thought quantum mechanics' laws were most applicable when we...

Homework Statement A certain odd-parity shell-model state can hold up to a maximum of 4 nucleons. What are its values of J and L? What about an odd-parity shell-model state with a maximum of 6 nucleons? Homework Equations Parity = (-1)L J = L+S Total angular momentum, J, is equal to orbital...

I got invited to visit Washington on winter next year. Not knowing the geography of the states, I checked on the map and my immediate reaction to my friend was: "Uff! That's almost in the North Pole!" :DD I'll have to think about it. Cold and me do not mix well. Jokes aside, I realized how...

@mfb From this thread - https://www.physicsforums.com/threads/why-doesnt-the-plate-interact-with-the-particle-in-double-slit.949489/ Post #2 - "It is not feasible to keep such a large and especially a biological object in a state without measurement" How does one keep a multi-particle...

WHERE is the refrigerant stored in the refrigeration system when the system is in OFF and in WHAT state Gas or Liquid ?

Hi. Is it correct to say that an inductor with a state, that is some level of current inside it, and a capacitor with some voltage, are equivalent to a current source (in the case of an inductor) and a voltage source (in the case of a charged capacitor) respectively at that instant of time? Of...

Hi everyone, I am doing a time dependent perturbation theory, in a case when the electron is prepared in a state of the continuous part of the energy spectrum. Existence of the discrete part and the degeneracy of the continuous part is irrelevant at the moment and will not be considered...

I'm watching a lecture and the professor is talking about generic quantum states as |\psi> He's making the point that this state is very generic. It can represent anything. He references some examples like the polarization of a photon and the path of a photon and the spin of an electron...

If we consider a singlet state : $$(|+-\rangle-|-+\rangle)/\sqrt{2}$$. And operators $$A=B=\textrm{diag}(1,-1)$$ I saw in a lecture that we can consider $$A\otimes B$$, it has multiple eigenvalues 1 and -1. It was then said : we can choose orthonormal basis vectors in each eigenspace. Hence...

How do i apply the laws of refraction to plane and curved surfaces. I have absolutely no idea how to even start on this one, its got nothing to do with the course, i am going to study. i need to understand this to move on but i genuinely have absolutely no interest in optics. I really can not...

> Operator $$\hat{A}$$ has two normalized eigenstates $$\psi_1,\psi_2$$ with > eigenvalues $$\alpha_1,\alpha_2$$. Operator $$\hat{B}$$ has also two > normalized eigenstates $$\phi_1,\phi_2$$ with eigenvalues > $$\beta_1,\beta_2$$. Eigenstates satisfy: > $$\psi_1=(\phi_1+2\phi_2)/\sqrt{5}$$ >...

Homework Statement The isobaric expansion coefficient and the isothermal compressibility are given by: $$\alpha_p = (1/V)(\partial V/\partial T)_p \quad \kappa_T = -(1/V)(\partial V / \partial p)_T$$ Suppose they have experimentally been determined to be: $$ \alpha_p = \frac{1}{T} +...

I was wondering how the rules work for observation in a quantum system. Particularly, about what happens if two separate entities try measuring at the same time. And also, what kinds of interactions are happening all the time that are considered measurements, for example in quantum...