Quantum mechanics Definition and 994 Threads

I'm trying to solve a problem where I am given a few matrices and asked to determine if they could be density matrices or not and if they are if they represent pure or mixed ensembles. In the case of mixed ensembles, I should find a decomposition in terms of a sum of pure ensembles. The matrix...

I'm just starting my journey into physics. I am looking for good quantum mechanics books or articles if anyone has some ideas be sure to let me know.

"Physicists are attempting to map the distribution of the prime numbers to the energy levels of a particular quantum system." https://www.quantamagazine.org/20170404-quantum-physicists-attack-the-riemann-hypothesis/

This is an interesting QM video. It would be interesting to get opinions about it from the QM students and experts alike.

The photoelectric effect is usually presented as an example disproving classical electromagnetism as viable model for interaction of light with matter and as evidence of quantization of energy in the electromagnetic field, i.e. the existence of photons. I would like to discuss a thought based on...

Homework Statement Homework Equations I'm not sure. The Attempt at a Solution I started on (i) -- this is where I've gotten so far. I am asked to compute the Fourier transform of a periodic potential, ##V(x)=\beta \cos(\frac{2\pi x}{a})## such that...

Homework Statement Homework EquationsThe Attempt at a Solution These are what i solved except (e), I have no idea how to solve (e).

I know the key tenants of quantum mechanics, and am not interested in the measurement problem. What we do know is that a particle has a wave function that describes the likelihoods of it having certain EXACT values when we measure it. That's all good, but I am still confused how the classical...

I'm interested in understanding the key physical differences between classical and quantum dynamics. I understand that spin (intrinsic angular momentum) is one major physical difference.* So I wonder whether all else flows from this? Or are there other major (unrelated) physical differences...

The title kind of says it all, but I'm searching for a textbook that has a heavy theoretical approach. Could someone help me with a recommendation?

Forgive me if this question is a bit amateurish but i am no physicist. I know in general terms that GR and QM aren't compatible with one another, but my question is...Do they even need to be? can it not be a handoff scenario? why can't GR govern what it is supposed to govern and QM govern what...

Homework Statement Homework EquationsThe Attempt at a Solution I tried to solve (a), but i don't know which approach is right ((1) or (2)) and how to solve (b).[/B]

Is there a possibility that none of the current interpretations of QM are right? Or is the current interpretations all that there will be on the table?

Heads up, I only recently got into quantum mechanics and don't feel like I got a solid grasp on the material yet. 1. Homework Statement Given is the wave function of a free particle in one dimension: \begin{equation} \psi(x,0) = \left( \frac{2}{\pi a^2} \right)^{1/4} e^{i k_0 x} e^{-x^2/a^2}...

I'm looking to just do some great reading on my own and want some suggestions. I could only use one prefix.

Can anybody tell me some of the best book for quantum mechanics which starts from basics to advance level

Hey! I posted this thread hoping that there are experts about quantum physics here. Please if you do not know a lot about the subject, don't answer this question: First things first, to be clear: I’m NOT building a quantum suicide machine and I’m NOT trying to kill myself. I’m just curious...

Hello! I am trying to write a program that solves the Schrodinger Equation for a particle in an infinite square well. I did a lot of research regarding the methods that could be used to accomplish this. I am writing this program in Matlab. The method I am using is called the Shooting Method. In...

I just came across this book and it seems to be very well written http://www.worldscientific.com/worldscibooks/10.1142/8534 Here is the amazon link https://www.amazon.com/gp/product/9814412902/?tag=pfamazon01-20 for self-learners, it also has a solution manual for sale in amazon...

Hi all, I'm trying to compute the solutions to a general case for a Schroedinger equation with a radial potential but I'm stuck on a rather small detail that I'm not sure about. It's well known that I can perform the change of variables to spherical coordinates and express the radial part of the...

Homework Statement Find the first-order corrections to energy and the wavefunction, for a 1D harmonic oscillator which is linearly perturbed by ##H'=ax##. Homework Equations First-order correction to the energy is given by, ##E^{(1)}=\langle n|H'|n\rangle##, while first-order correction to the...

Hello! I would really appreciate it if somebody could recommend to me any books on geometric phases especially on Berry's phase. Thanks!

In the book of Modern Quantum physics by Sakurai I wonder how 1.6.26 can be 1.6.27.

Has anyone read the 7-book series http://amzn.to/2lwgn66 by Andrew Thomas? Just wondering what you think of his conjectures / speculations at the final sections of each book, i.e. on the link between relativity and quantum mechanics, equation of the universe, etc... I like that he...

Hey guys, Hope all is well. I'm trying to get my head round some of the Quantum Mechanics of spin. I fully understand why the Pauli equation acts on a two component spinor wavefunction, where I'm a little confused is why the Dirac equation then acts on a 4 component spinor...

I'm trying to prove that the wave function of Hydrogen for the fundamental state is normalized: $$ \Psi_{1s}(r)=\frac{1}{\sqrt{\pi a^3}}e^{-\frac{r}{a}} $$ What I tried is this: $$ I= \int_{-\infty}^{\infty} | \Psi^2(x) | dx = 1$$ $$ \int_{-\infty}^{\infty} \frac{1}{\pi...

Hi all, I have a question about the quantum nature of ionic bonds. I know some ideas about molecular bonding which can combine two ground state of H atom to get a bonding state and an anti-bonding state which in the case of H2 molecules it correspond to the covalent bonding (sharing of...

For someone at my level, the following article is extremely informative. I would like to post a link to it. But first here are a few quotes from the article... Here is his definition of wave-particle duality... And here is his statement on Cognitive Dissonance... "Quantum Mechanics and the...

Is there any interpretation of QM that is Psi-ontic, local, and has wave function collapse?

I'm pretty new to quantum, so I'm pretty sure I'm missing something basic here. I've got a 4x4 Hamiltonian with eigenkets $$\psi_{U} = 1/(\sqrt 2) (\psi_{1up} \pm \psi_{2up})$$ and $$\psi_{D} = 1/(\sqrt 2) (\psi_{1down} \pm \psi_{2down})$$ The only difference between the two states is the spin...

Hello everybody! I am excited to be part of this forum. It's the first time for me. I am 41, from France and with my sons (9, 7 and 6) we love physics. I have studied economics and discovered my interest for physics only a few years ago. I try to learn things by myself with videos from You tube...

I was reading Bransden's Quantum Mechanics 2nd edition, chapter 2 page 61. There,it says "It should be noted that since E =hv (v for nu), the absolute value of the frequency has no physical significance in Quantum mechanics..." Why is that? Isn't this a contradiction?

Homework Statement Consider a particle with angular momentum l=1. Write down the matrix representation for the operators L_x,\,L_y,\,L_z,for this particle. Let the Hamiltonian of this particle be H = aL\cdot L-gL_z,\,g>0.Find its energy values and eigenstates. At time t=0,we make a measurement...

What are some of the practical applications of quantum mechanics that are being utilized to optimize our existence as a species?

in an attempt to get a better understanding of what happens during a measurement i have constructed a gedanken-experiment with two photon interference that regardless of its outcome seems to contradict quantum mechanics in one way or another and i was hoping to get a clarification here where i...

This was off-topic in the thread on vacuum fluctuations where the quote appeared, so I opened a new one. I didn't know the paper before, so first need to read it...

Homework Statement Using the equations given, show that the wave function for a particle in the periodic delta function potential can be written in the form ##\psi (x) = C[\sin(kx) + e^{-iKa}\sin k(a-x)], \quad 0 \leq x \leq a## Homework Equations Given equations: ##\psi (x) =A\sin(kx) +...

From Frank Wilczek's book 'A Beautiful Question' 'Quantum mechanics shows how the poverty of energy imposes structure' P196 Is he saying the poverty of energy imposes structure in the energy of a quantum system or structure in matter? Or both? If we look at an atom it has ordered structure in...

Hello! I will be attending a course on condensed matter physics with emphasis on geometrical phases and I was wondering if the are any good books on gauge transformations, gauge symmetry and geometrical phases that you know of. Thanks in advance!

Homework Statement A particle of mass m, is in an infinite square well of width L, V(x)=0 for 0<x<L, and V(x)=∞, elsewhere. At time t=0,Ψ(x,0) = C[((1+i)/2)*√(2/L)*sin(πx/L) + (1/√L)*sin(2πx/L) in, 0<x<L a) Find C b) Find Ψ(x,t) c) Find <E> as a function of t. d) Find the probability as a...

http://www.nybooks.com/articles/2017/01/19/trouble-with-quantum-mechanics/

Hello, I will be attending an undergraduate course called "Theoretical Physics" and I want to borrow some books from the library that cover the material of this course. I would appreciate any suggestions. The syllabus of the course is the following(I will be translating so I am sorry If...

I am an engineering student with an interest in quantum mechanics : However, I really need to make a flowchart so I can understand where to proceed What I know: Math - Multivariable calculus, Differential Equations including laplace and Fourier series, and Basic Linear Algebra (Spaces...

hi I'm in grade 9 and I have to make a 20 slide slideshow and a 6 page essay or a module I need ideas on what to do

Hi all, I'm reading a paragraph from "Geometric Algebra for Physicists" - Chris Doran, Anthony Lasenby. I'm quite interested in applying GA to QM but I've got to a stage where I am not following part of the chapter and am wondering if someone can shed a little light for me. The part...

Homework Statement An electron in the Coulomb Field of the proton is in the state: |ψ> = (4/5)|1, 0, 0> + (3i/5)|2, 1, 1> with |n, l, m> as the quantum numbers defining the state a) What is <E> for this state? What are <L2> and <Lz>? b) What is |ψ(t)>? Which expectation values...

I was sitting at my bed when I suddenly have an idea. The unification of electromagnetism and gravity was made with General Relativity. For this to happen, one just need to write the energy due to electromagnetic field in "differential geometry" form, through the Electromagnetic tensor, in a...

Homework Statement Using Hund's rules, find the ground state L, S and J of the following atoms: (a) fluorine, (b) magnesium, and (c) titanium. Homework Equations J = L + S The Attempt at a Solution I'm having trouble understanding what L, S and J mean on a basic level. I read the textbook...

Hello all! You'll see, I am self studying physics, and have already finished with Kleppner - Kolenkow mechanics (complemented with Morin) and Griffiths electrodynamics. Now I think I am prepared for QM, but I do not know which textbook is better for me. I have reduced my options to Griffiths...

Hi, Can anyone please explain the physical meaning of coherence(Quantum Mechanics). Thanks is advance