State Definition and 1000 Threads

As a non-Physics major, like many others, I read science-fiction, hard science-fiction, have undergraduate/graduate courses on Astronomy and college physics. I also participated in R&D that produced electric rockets able to power small space vehicles (very slowly, but surely). I deal with...

If I'm using the basis vectors |u> and |r> for two polarisation states which are orthogonal in state space, I've seen the representation of a general state oriented at angle theta to the horizontal written as $$\lvert\theta\rangle = \cos(\theta) \lvert r \rangle + \sin(\theta) \lvert u...

As far as I know we can express the position and momentum operators in terms of ladder operators in the following way $${\begin{aligned}{ {x}}&={\sqrt {{\frac {\hbar }{2}}{\frac {1}{m\omega }}}}(a^{\dagger }+a)\\{{p}}&=i{\sqrt {{\frac {\hbar }{2}}m\omega }}(a^{\dagger }-a)~.\end{aligned}}.$$...

Most molecules are in singlet ground state which is of higher energy than triplet lower energy state .According to thermodynamics molecule tend to remain in lower energy state.Therefore,I presume molecules should remain in triplet state .Could anyone clarify my point

Do electrons have motion or they just accelerate when they get enough energy?

I'm reading a book about analytical mechanics and in particular, in a chapter on hamiltonian Mechanics it says: "In the state space (...) the complete solutionbof the canonical equations is pictured as an infinite manifold of curves which fill (2n+1)-dimensional space. These curves never cross...

I would like to apply a General Lorentz Boost to some Multi-partite Quantum State. I have read several papers (like this) on the theory of boosting quantum states, but I have a hard time applying this theory to concrete examples. Let us take a ##|\Phi^+\rangle## Bell State as an example, and...

I was recently working on a problem of Griffiths and in the solution's manual it used an argument to solve a diffential equation that caught my attention. It said that it would look first to the steady state solution of the ODE. I tought "All right, I get that" but when I got to translate the...

I have a Hamiltonian ##H_{\lambda(t)}##, where ##\lambda (t)## characterizes a time dependent path in parameter space. The parameter is changed in finite time from ##\lambda (t_i)## to ##\lambda(t_f)## . At ##t = t_i## the system is in the intial state ##|\Psi>##. What is the work done on the...

I’m not sure if this belongs in classic or quantum physics... but here it is...Is it possible to calculate the “voltage” between an electron and a proton in a ground state hydrogen atom?I know the ionization energy is 13.6 eV, so I assume it's safe to say the voltage is 13.6 volts at a certain...

I'm reading Tim Maudlin latest book "Philosophy of Physics: Quantum Theory". In the following descriptions, it is not akin to holographic? "In the context of the quantum recipe, the mathematics of the wavefunction suggests that the quantum state (whatever it is) is a fundamentally global sort...

Somewhat embarrassingly as a third year undergrad, this question has been completely stumping me for far too long now (2 hours). The solution is 1.42 Å and the working is given as |r2| = 2cos(30)*1/3(2.46) or alternatively |r2| = (1/2|a|)/cos(30) But I cannot grasp where this comes from...

Hello, https://www.physicsforums.com/lib/Eqn026.pngI have the pressure (P)-volume (V) Birch-Murnaghan equation of state coeffcients (V_{0},K_{0}, K^{'}_{0}, K^{''}_{0}) for a number of different compositions. I'm interested in the volume at very specific pressures only and ideally I would like...

Given a box made of perfectly conducting material. At some part of it at t=0 there is a localized magnetic field. It's sourceless and there aren't any dissipation. After t=0 it starts to spread and fill the box. What is the equilibrium state? Thanks for the answer(s), Robert

I mean the first question has derivative form and the second is linear form so what the difference here in steps of converting both to transfer function... please need some ellaboration to make sure i am solving correctly or not... is it correct to apply the same rule on both: Transfer function=...

My questions are now... Do the steps of converting this space to transfer function include any laplace ? or just we do get [SI-A]-1 and then transfer function is = C* [SI-A]-1 * B As [1 0] * [s-1/det -0.5/det ; 0.5/det s-0.5/det] * [0; 1] = -0.5/s^2+s+0.5 I mean do we need any laplace after that...

Hi, I have to study for a solid state physics course and I'm not sure what textbook would be the best. Our professor suggested "Principles of the theory of Solids" by Ziman, or "Solid state physics" by Ashcroft. I'll intend to use both: one I buy, the other one I borrow from the library. But...

I started and successfully showed that the expectation of X_1 and X_2 are zero. However the expectation value of X1^2 and X2^2 which I am getting is <X1^2> = 0.25 + \alpha^2 and <X2^2> = 0.25. How do I derive the given equations?

Does ##w## = -1 by itself imply that spacetime is flat, or is it only due to ##\Omega##Matter + ##\Omega##Λ = 1 ?

Let's consider Bohm's paradox (explaining as follows). A zero spin particle converts into two half-spin particles which move in the opposite directions. The parent particle had no angular momentum, so total spin of two particles is 0 implying they are in the singlet state. Suppose we measured Sz...

Should I treat ψ1 as ψ and ψ 2 as ψ*?

Let K=2Lfs and Pin=Pout, Have, (Vin-Vo)/k D^2 Vin =Vo ^2/R (I am fine up to this part. I am equating input power to output power) V^2=D^2 + D^2 R/2 Vo Vin - R/k D ^2 Vin =0 (This is where the instructor takes over. Can’t figure out how he got to V^2. Where did that come from? Thought I was...

What I know is the following: The total angular momentum of the nucleus is just the total sum of the angular momentum of each nucleon. If the nucleons are even the total angular momentum in the ground state will simply be ##0+##. If the odd number of nucleons is close to one of the magic...

I believe It's fission, but am Unsure. As for X I will try solve later.

Hello I could use some help understanding a statement / sentence within my Griffiths Quantum Mechanics book. The same statement is made within video lecture I found surfing to understand the Griffiths text. I have the 2nd edition. (On page 185) Discussing addition of angular momenta – 2 spin ½...

Hi All, Considering a set of many many small hard balls which start colliding inside a box. The velocities of these balls being mostly greater than c/2. Is it possible, in this case, to speak of convergence to a thermal state in the same sense of ordinary thermodynamics (i.e., using...

Summary: Please does anyone has a lecture note dat explain solid state electronic I need a lecture note or a textbook dat explain solid state electronic especially band gap Crystal growth Diffusion of semiconductor Fermini level

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hey :) assume I have an operator A with |ai> eigenstates and matching ai eigenvalues, and assume my system is in state |Ψ> = Σci|ai> I know that applying the measurement that corresponds to A will collapse the system into one of the |ai>'s with probability |<Ψ|ai>|2. with that being...

1. My book states that an increase in pressure on ice causes temporary melting. Could you explain the reasoning behind this/ the law that predicts this? 2. My book also states that if water is boiling in a flask and the outlet is blocked then temperature drops and boiling would stop unless more...

I understand that quantum objects have wave and particle properties. I know that k = 2π / lamda. I am simply not understanding the x-axis of a bandstructure plot of E(k) vs. k. I've read parts of a book by Roald Hoffman on this subject. In the book it is shown that there are infinite chain of...

what would cause the phase difference ?

For my own understanding, I am trying to computationally solve a simple spinless fermionic Hamiltonian in Quantum Canonical Ensemble formalism . The Hamiltonian is written in the second quantization as $$H = \sum_{i=1}^L c_{i+1}^\dagger c_i + h.c.$$ In the canonical formalism, the density...

Problem Statement I was watching a YouTube video regarding the calculation of expected return time of a Markov Chain. I haven't understood the calculation of ##m_{12}##. How could he write ##m_{12}=1+p_{11}m_{12}##? I have given a screenshot of the video.

Does anybody here have any experience with Michigan State’s undergraduate physics program? If so, what stuck out to you and what did you like/dislike about it?

Does anybody here have any experience with Ohio States’s undergraduate physics program? If so, what stuck out to you and what did you like/dislike about it?

I understand that ##\dot m=\rho Q## and ##{\dot m}_{in}= {\dot m}_{out}## . So one can say that ##\rho Q_1 = \rho Q_2##. But I'm not sure if that equation is correct. I don't know if the density remains constant, or the volume flow rate. And then how I'm also supposed to tie a state equation in...

My work was as follows: The first law states ##dU = TdS - PdV##, and thus $$p =- (\partial U/\partial V)| _S$$ $$U = -RT \ln(V-b) + f(S)$$ To determine ##f(S)##, I reasoned that in the ideal gas limit of ##b = 0##, ##U## should take the form of the ideal gas' molar internal energy ##\frac{3}{2}...

The definition of coherent state $$|\phi\rangle =exp(\sum_{i}\phi_i \hat{a}^\dagger_i)|0\rangle $$ How can I show that the state is eigenstate of annihilation operator a? i.e. $$\hat{a}_i|\phi\rangle=\phi_i|\phi\rangle$$

One thing about terminology that I think c/should be changed for Continuum Mechanics: 1) 'Ideal Fluid' Describe Behavior of Matter in Phase States of liquid/gas and sometimes Bulk-Solid: -continually deform under applied shear stress or external force -usually zero shear modulus -behavior can...

What are some good solid state/condensed matter theory schools in Europe ?

I'm a senior in high school and have been accepted to the University of Arizona - which would cost around $14,000 - and Michigan State University - which would cost around $30,000. That difference in price would hit my family and I hard, but from what I can tell the difference in program quality...

According to textbooks, an atom in ground state doesn't radiate. Yet I got some other idea after reading Wu Ta-you's theoretical physics book. I hold the viewpoint that the atom does radiate, and at the same time it absorbs energy from heat radiation in its environment. The energy it radiates...

Hi, I'm looking for someone who take the university of physics which is 251, 251L from the Mayville state university.. Is it hard to study? I'm trying to find the lab result about that but they said need a kit which is 600 bucks to buy.. I'm considering do I really have to buy, or just looking...

Theoretical problems often begin with "given a system in state ψ0" For example, the 2-slit experiment begins with the assumption of a plane wave incident on the slits. I had always understood to this mean some prior set of measurements had been made to determine the initial state. But how can...

Homework Statement Question: https://imgur.com/a/EmGDW87 Homework Equations Q =VC V = IR The Attempt at a Solution I don't understand how the capacitor C_2 is in parallel with R, which would dictate that they have the same p.d, but then again the circuit is in stead state and so no current...

We all know that the state of matter can be changed by increasing temperature or by applying pressure. And, all of these, in some way lead to a change in the particles' speed. The speed of the particle decides the state of matter. So, if we were to throw an object at very high speeds, like 50%...

I am learning for my exam in particle physics. One topic is statistical physics. There I ran into this question: Consider an atom at the surface of the Sun, where the temperature is 6000 K. The atom can exist in only 2 states. The ground state is an s state and the excited state at 1.25 eV is a...

Let us consider QFT in Minkowski spacetime. Let ##\phi## be a Klein-Gordon field with mass ##m##. One way to construct the Hilbert space of this theory is to consider ##L^2(\Omega_m^+,d^3\mathbf{p}/p^0)## where ##\Omega_m^+## is the positive mass shell. This comes from the requirement that there...

A physicist prepares a box and tells us that in the box there is a cat that is in a superposition of being alive and being dead. How can we be sure whether they're telling the truth? Is the state a superposition or a mixture? If we open the box and measure only whether the cat is alive, using...