What is State: Definition and 1000 Discussions

Ondo State is a state in southwestern Nigeria. Created in February 1976 from the former Western State, Ondo State borders Ekiti State (formally part of the state) to the north, Kogi State to the northeast, Edo State to the east, Delta State to the southwest, Osun State to the northwest, and Atlantic Ocean to the south. The state's capital is Akure, the former capital of the ancient Akure Kingdom.
Nicknamed the "Sunshine State", Ondo State is the 18th largest state in the country. The state is predominantly Yoruba, and the Yoruba language is commonly spoken. The state economy is dominated by the petroleum industry, with cocoa production, asphalt mining, and activities utilizing the state's extensive coastline also serving as major economic factors.

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1. Mathematica Mathematica : NDSolve on 2-D steady state heat eqn

I am trying to implement this equation ##−k∇^2 u = e^{-(x^2+y^2)}## using NDSolve in Mathematica. The idea is to solve for the temperature of a plate 10 x 10 units, with heat inputs as per the RHS. Here is my attempt: NDSolve[{ - Laplacian[u, {x, y}] == Exp[-(x^2 + y^2)], u[x, -5] == 0, u[x...
2. I Double Check Normalization Condition

Consider the state ##\ket{\Psi} = \sum_{1 \leq n_{1} \leq n_{2} \leq N} a(n_{1},n_{2})\ket{n_{1},n_{2}}## and suppose $$|a(n_{1},n_{2})| \propto \cosh[(x-1/2)N\ln N]$$ where ##0<x=(n_{1}-n_{2})/N<1##. The claim is that all ##a(n_{1},n_{2})## with ##n_{2}-n_{1} > 1## go to ##0## as...
3. I Spin state, base transformation

how do i write the z spin state using the spin state on x or on y?
4. B Extremely elementary questions about QM

Im trying to learn QM on my own and I just want to clear some things up. I feel dumb writing some out but Id rather clear my confusion than believe im interpreting what I read correctly. From what I've read, every measurement of a system gives us values that are the eigenvalues of a certain...
5. I Singlet Halperin State Construction

Hi all, I'm reading through David Tong's Fractional Quantum Hall Effect notes right now and am stumped by how he constructs the singlet Halperin state (the last equation in this document: https://www.damtp.cam.ac.uk/user/tong/qhe/three.pdf, on page 116 as per the document page number at the...
6. Requesting Resources and Animations to understand Solid State Physics

TL;DR Summary: I need animations to understand physics better. Any links and animations would be very appreciated. I have started learning Solid state physics and I am struggling somewhat to understand and imagine certain things. I feel like this is one area of physics which needs extensive...
7. I Bra-Ket Notation Manipulations: Quantum State Expansion

I suspect it will help if you know about my background: I did some linear algebra in university but never used it and am now in my mid 60s. I am interested in understanding the mathematics of quantum physics. I have read a number of layman's texts on quantum mechanics, but they all gloss over...
8. A Deriving Non-linear acoustic wave models, equilibrium state assumption

The standard derivation in obtaining a single wave equation involves making use of the heat equation with a Taylor expansion of the equation of state, then differentiating this equation and the continuity equation with respect to time, and combining with the divergence of the NS equation...
9. Trouble solving for end state of two control volumes in a rigid tank

TL;DR Summary: Struggling to structure the problem and derive an analytical solution for gas expanding into other gas in a rigid tank. Preferred formulation is fixed control volumes. This is not a homework problem. The problem: Two control volumes (A and B) are in a rigid tank filled with air...
10. I What is the calculation for value B in Penrose's entropy model?

In the book "Cycles of Time" by Roger Penrose, there is a part of the explanation of entropy that I don't understand. There are 10^24 balls, half of which are red and the other half blue. The model is to arrange the balls in a cube with 10^8 balls on each edge. It also divides the cube into...
11. Symmetrical parallel inductors, different currents? State Preparation

We have there parallel inductors (i.e. having the same voltage) with the same inductance, having different currents at a particular time. It appears that this is only possible if the current phasors have different phases See bottom left of video below, ##I_1, I_2, I_3## (time already set to...
12. A Something is wrong in the state of QED...?

Dear all, recently I came across this paper by one Oliver Consa, https://arxiv.org/abs/2110.02078 The recap is I'm curious whether experts think this is historically right. To me it seems that the author is mainly rephrasing critical sounds from the past regarding renormalization, before...
13. I Finding ##\partial^\mu\phi## for a squeezed state in QFT

I'm trying to apply an operator to a massless and minimally coupled squeezed state. I have defined my state as $$\phi=\sum_k\left(a_kf_k+a^\dagger_kf^*_k\right)$$, where the ak operators are ladder operators and fk is the mode function $$f_k=\frac{1}{\sqrt{2L^3\omega}}e^{ik_\mu x^\mu}$$...
14. A Steady state confined flow field: Is it cyclic?

For a fluid that is confined to a finite region with no sources and sinks, are the only options for the flow field a) static, and b) cyclic? The example I have in mind is Rayleigh convection in a shallow dish heated from below, where convection cells are formed beyond a certain temperature...
15. State whether the distance x for the block would be greater/less/same

I was able to solve for a, b, c, and d. I don't know whether I'm saying it right for part e. The first scenario is a perfectly inelastic collision. After impact, the bullet transfers momentum to the block, causing the block to move (it was initially at rest), and the bullet + block fall at a...
16. I Understanding Diffraction Condition in Kittle's Intro to Solid State Physics

I am going over the diffraction condition section in Kittle's Introduction to Solid State Physics physics and I am having a hard time understanding why the phase difference angle for the incident wave is positive while the phase angle difference for the diffracted wave is negative. Thank you...
17. Incompatibility between ideal gas equations of state

To solve this problem I used two equations: $$PV=nRT,$$ where ##P## is the pressure, ##V##the volume, ##R##the gas constant, ##T##for temperature and is##n##the number of moles, related to the mass ##m## and molar mass ##M## by $$n=\frac{m}{M}.$$ It will be also necessary consider the...
18. A Ballentine on the "multicomponent state function"

I have just finished reading Ballentine Chapter 7.2 and I am positively baffled, perhaps because Ballentine is being sloppy for the first time. I attach the discussion in Ballentine at the end of this post if it helps, though I hope my writing will be independent thereof. This question is...
19. Sending drive Pulse in CQED and visualize the state by QuTip

[Mentor Note -- This thread is a continuation of a previous thread, with the emphasis in this new thread on the programming implementation. Previous thread is here: https://www.physicsforums.com/threads/can-anyone-give-me-the-details-of-creating-a-cat-state-in-circuit-qed.1048821/ ] Hello...
20. A Can anyone give me the details of creating a cat state in Circuit QED?

I am so new to circuit quantum electrodynamics. As far as I know, there are few things I could manipulate, like resonator, qubit resonance frequencies, Hamiltonian, coupling strength, Hilbert-space cutoff, dissipation rate, but they do not make sense to me and I do not how they can relate to my...
21. I The left-right symmetry and forbidden triplet spin state

Suppose that we have a system including two single (and identical) orbitals as shown in the attached image. Then, consider the states that we have two different spins on the two orbitals. It seems that because of the left right symmetry of the system the special part of teh wave function can not...
22. Equations of State in Modern Classical Physics (Thorne/Blandford)

TL;DR Summary: Questions regarding the book "Modern Classical Physics" by Thorne/Blandford Hello, I'm going through this book and on pg. 127, regarding equations of state, there is a parameter, t (explicitly stated: "not to be confused with time"), that uses hyperbolic functions to relate the...
23. I The collapse of a quantum state as a joint probability construction

The titular paper can be found here, https://doi.org/10.1088/1751-8121/ac6f2f, and on arXiv as https://arxiv.org/abs/2101.10931 (which is paginated differently, but the text and equation and section numbers are the same). Please see the abstract, but in part this 24 page paper argues that we...
24. Calculations using the Standard Solar Model & Solar Equations of State

Assuming the Sun’s core has a mass of 0.35 Msolar_mass and taking values for other quantities from a internet background search or from the following figures (i.e.: Radius "solar core" = 0.25 Rsolar_radius ): ------------------------------------------------------------------------...
25. Einstein solid state model exercise

I tried to solve it considering the canonical ensemble (since the system is at the equilibrium with temperature T) and started finding the partition function:The problem is I am not sure if I have done it correctly and need help because I don't really know where to check.
26. Upper bound for first excited state - variational principle

I'm solving problem number 5 from https://ocw.mit.edu/courses/8-05-quantum-physics-ii-fall-2013/resources/mit8_05f13_ps2/. (a) Here I got: $$\beta = \frac{\hbar^{\frac{1}{3}}}{(\alpha m)^\frac{1}{6}}$$ and: $$E = \left ( \frac{\alpha \hbar^4}{m^2} \right )^\frac{1}{3}e$$ (b) Using Scilab I...
27. A Quantum projection when measuring state population

Hello! I have two energy levels of opposite parity close by (we can assume they are far from all the other levels in the system) and an off-diagonal term in the 2x2 matrix Hamiltonian that weakly couples them. I initially populate only one parity state, say the positive one, and after a while...
28. I Spectral Decomposition of the State Space

I'm looking to check my understanding of the information below and ultimately get a better understanding of it. Is spectral decomposition a mathematical procedure? Does "the state space of the measured system" refer to the possible values that the system could take, when measured?
29. I What is the smallest possible state change in the Universe?

Hello everyone! I was wondering what is the fundamental state change in the universe? I.E the universe is in one state, then it goes into another state, what is the state change? Has science determined what it is? Do we know the dimensional units of the quantity? I'm not sure if this has a...
30. I Quantum mechanics stationary state

Hi, I have hard time to really understand what's a stationary state for a wave function. I know in a stationary state all observables are independent of time, but is the energy fix? Is the particle has some momentum? If a wave function oscillates between multiple energies does it means that the...
31. Vibrational Levels in Molecular Electronic State

##K = \frac{N}{m} = \frac{3eV}{bondlength^2} = \frac{4.806*10^-19 J}{(2*10^-10)^2} = 12.015## Then I know that ##H = \frac{1}{2}mωx^2 ## where ## k = mω^2 ## and also ##H=ħω(n+\frac{1}{2}) ## Therefore, ## \frac{1}{2}kx^2 = ħω(n+\frac{1}{2})## Solving for n, ## n = \frac{1/2kx^2}{ħω} -...
32. I Vector operator acting on a ket gives a ket out of the state space

Definition of linear operator in quantum mechanics "A linear operator ##A## associates with every ket ##|\psi\rangle \in \mathcal{E}## another ket ##\left|\psi^{'}\right\rangle \in\mathcal{E}##, the correspondence being linear" We also have vector operators ##\hat{A}## (such as a position...
33. I Electron transitions within the same excited state?

Hi, I am have trouble finding whether or not the topic is possible. It concerns an electronic dipole. I am well familiar with the general rules: https://en.wikipedia.org/wiki/Selection_rule Is it possible for transitions to occur from e.g. ^4P_1/2 and ^4P_2/3, which are both in n=3? If they...
34. I How do we determine complex state equations for substances?

Hello. I am reading about state equations from a physics textbook, Physics by Frederick J. Keller, W. Edward Gettys, Malcolm j. Skove (Volume I). I don't understand some parts but since I have the Turkish translation of the book I must translate it as good and clear as possible. "State...
35. A Magnetic bound state in classical mechanics

Seven years ago, I wanted to share and discuss my experiments results there but it was not possible since there was no published peer review paper yet and apparently not fulfilling forum requirements. Now we have such a publication, but still not sure the subject can be discussed here. Anyway...
36. Is Moore's Law Still Relevant in the Age of Semiconductors and Robosourcing?

I'm sure this gets asked a lot. CPUs and GPUs still kind of mystify me, since I do not know their science. It came to me after studying some computational linguistics that it might be possible that in the next 100 years, we might have smart-translating, smart-talking machines without a theory...
37. I What happens to the other particle in an entanglement state?

if I have two particles in an entangled state, I make them travel in different directions, and I measure the state of only one of them then I know the outcome of the measurement of the other. But when I take a measurement on the first particle, what happens to the second? Does it undergo a...
38. I Dimensions of quantum cell automata's state space

In the paper C. S. Lent and P. D. Tougaw, "A device architecture for computing with quantum dots," in Proceedings of the IEEE, vol. 85, no. 4, pp. 541-557, April 1997, doi: 10.1109/5.573 about quantum dots, it is stated that the basis vectors in the space of quantum states for a single cell...
39. I The quantum state of the Universe

The dimension of the space of quantum states of multiple particles grows exponentially as the number of particles increases. I would have expected to more likely find the quantum state of many particles in a strange state (such as an entangled one) but it is not so, why? Why isn't the universe...
40. B Resonance state - Alternating current

In alternating current, is the resonance state that the phase angle of the current is 0?
41. Solving Equation to Analyze Steady State Current

I set up the equation ##V-iR-L\frac{di}{dt}=0##, with ##i(0)## and by solving it I got ##i(t)=\frac{V}{R}(1-e^{-\frac{R}{L}t})##. Then, since the steady state current is ##i_s=\frac{V}{R}## I imposed the condition ##i(t_1)=\frac{9}{10}\frac{V}{R}\Leftrightarrow...
42. Finding Probability of Two-Identical-Particle System in a Given State

Problem: A system contains two identical spinless particles. The one particle states are spanned by an orthonormal system ##|\phi_k>##. Suppose that particle states are ##|\phi_i>## and ##|\phi_j>## (##i \neq j##). (a) Find the probability of finding the particle in the state ##|\xi>## and...
43. A Homodyne detection quantum state tomography

In balanced homodyne detection, it is claimed that one can do state tomography. I understand most of the derivation except one part. Here is a figure describing homodyne detection. the operator that is being measured is $$R=N_{1}-N_{2}=a^{\dagger} b+b^{\dagger} a$$. taking the mode b to be...
44. I Microstates of an atom in an energy state

I have a question about a sentence in the book Introduction to Thermal Physics (Daniel v. Schroeder). So in chapter 6, Schroeder talks about an atom isolated. This means its energy is fixed. The atom is in some state. The energy states of the atom have degenerated. All microstates with that...

47. I Operator acting on ket state n

I tried playing with the number's operator eigenvalues equation but couldn't get anywhere, can s/b help me out?
48. A Schmidt decomposition - How do I find the matrix related to the state?

Hello, I am currently studying the Schmidt decomposition and how to use it to determine if a state is entangled or not and I can't understand how to write the state as a matrix so I can apply the Singular Value Decomposition and find the Schmidt coefficients. The exercise I am trying to complete...
49. Schools College Decision Debate -- Purdue, Penn State or Illinois for Engineering?

I am currently a high school senior and intend to study engineering in college next year. I am currently considering 3 schools: Purdue, Penn State, and Illinois. All three are excellent schools with solid engineering programs, and all have different benefits and drawbacks. I was admitted to the...
50. Refrigerant state in/at saturation

Hey everyone. Bit of a random question. So when refrigerant has been fully condensed I understand that it's a liquid, just like a glass of water, albeit under pressure and with no gas above it. When the refrigerant has been superheated it's just a gas, like you would get if you took a sealed...