Qm Definition and 1000 Threads

I've been looking for a good QM book for a while, and I'm considering purchasing Morrison's book. I've already completed an undergrad QM course with Griffith's. I would like to find a book that is strongly oriented towards relating QM theory to the real world, rather than just explaining how to...

Hi, In QM, when we make a measurement, our wavefunction collapses into one of the eigenstates of the operator. This process is supposed to be random for any single measurement but obeys some statistics if we make a large number of measurements. Could someone explain how we know that it is...

I'm looking for a text with loads of worked examples , plenty of exercises, and since I'm working alone , a solutions manual - or some access to the answers - is vital. Currently working Griffiths. The only way to master this demon is by doing dozens of problems. Any suggestions appreciated...

reading this http://uk.arxiv.org/abs/1004.2529 about supposed parallels between the mathematical structure of probability in QM and some problems in economics question is that are there really any violations of classical probability theory, such as Pr(A) > Pr(A \cup B) in QM? The supposed...

Hi there, I'm reading Dirac's Principles of QM, but I think I miss something... 1)When he derives the Poisson quantic bracket, he states that u_1v_1-v_1u_1=i\hbar[u_1,v_1] and says that hbar must be real since we introduced the imaginary unit. The thing is, since uv-vu is real, because we are...

Commutators on a discrete QM lattice = ? Please let me know if any of the following is unclear: I was thinking about how you could go about doing QM not in a continuous space but instead on a lattice, take 1D for simplicity. Let's use a finite (not countably infinite) number of positions say...

Homework Statement Show that: [p,x] = -iħ, Show that: [p,x^n] = -niħ x^(n-1), n>1 Show that: [p, A] = -iħ dA/dx Where p = -iħ d/dx, and A = A(x) is a differentiable function of x. Homework Equations [p,x] = px - xp; The Attempt at a Solution So far I understand part of each...

Sorry if this had been already discussed: http://arxiv.org/abs/1008.1066 So, what I see (assuming that Universe is infinite, this is an important assumption, not proven of course, but if this is true): 1. The 'Interpretation war' is over, amen, the most important weakness of MWI has...

I have been wondering if I should take Graduate level QM as an undergraduate. I'm currently signed up for a two quarter QM series, I have already taken a one quarter introduction to QM. I am a bit apprehensive as I am unsure if they assume vast QM knowledge (which I would sort of expect seeing...

Where I can read about Bohmian interpretation of QM? I need a good , solid book.

Dear All, This is my first post. I appreciate your help. I have the following question which i am struggling to understand, let alone solve. Consider a quantum mechanical particle with the mass m moving in one-dimensional described by the following Hamiltonian; (1)\hat{H} =...

I'm reading vol. 3 of the Feynman lectures on physics, and in chapter three he describes his third general principle of quantum mechanics as follows: "The third general principle: When a particle goes by some particular route the amplitude for that route can be written as the product of the...

What are the active questions/topics in QM?

A beam of neutrons with energy E runs horizontally into a crystal. The crystal transmits half the neutrons and deflects the other half vertically upwards. After climbing to height H these neutrons are deflected through 90 degrees onto a horizontal path parallel to the originally transmitted...

To my understanding you can believe in the multiverse theory without subscribing to many-worlds interpretation of quantum mechanics. But can you subscribe to the many-worlds interpretation while also believing there is only this one universe (and that it just has hidden dimensions). Can...

QM: The "double square well" potential Homework Statement Consider the "double square well" potential below. Qualitively (no calculations) how do the energies of the ground state and the first excited state vary as b goes from zero to infinity (i.e. the two wells become further and further...

some, like momentum appear to be, but are all of them?

Hi everybody, I have been looking over a number of papers by Alexey Kryukov and I have some questions. I have been in some brief correspondence with him about some of my questions but I wanted to ask the forums. Consider this paper...

http://www.esa.int/esaCP/SEM5B34TBPG_index_0.html "ESA’s Integral gamma-ray observatory has provided results that will dramatically affect the search for physics beyond Einstein. It has shown that any underlying quantum ‘graininess’ of space must be at much smaller scales than previously...

I'm reading Daniel T. Gillespie's A QM Primer: An Elementary Introduction to the Formal Theory of QM. In the section on continuous eigenvalues, he admits to playing "fast and loose" with the laws of calculus, with respect to the Dirac delta function. I'd like to understand it better, or, if such...

hello I started to read ‘QFT in a Nutshell’ by A. Zee. In the introduction to the path integral formulation of quantum mechanics there is the story about a particle going through a series of screens with holes drilled through them. Then the number of holes in each screen is increased. This...

Hi there, I am on high school physics level and came here to have a few questions answered that keep boggling my mind and challenging my standards of logic... please keep explanations simple, since I don't have any extensive knowledge of QM and English is not native to me, thanks...

In Fredrik's recent thread: https://www.physicsforums.com/showthread.php?t=506326 some questions arose about this paper: J. B. Hartle, "Quantum Mechanics of Individual Systems", Am. J. Phys., vol 36, no 8, (1968), pp704-712. [For other readers, you'll need to have read or be able to...

I think I may be over-thinking this as I have had one formal course in QM and an independent study course in QM, but any help is MORE THAN GREATLY APPRECIATED! Homework Statement Prove that |-V> = -|V> Homework Equations He instructs us to begin with |V> + (-|V>) = 0|V> = |0>...

As far as explaining the refraction of light through glass (as an example), does the Huygens-Fresnel principle serve any purpose in the quantum mechanical (or the quantum electrodynamical) model? http://en.wikipedia.org/wiki/File:Refraction_-_Huygens-Fresnel_principle.svg Is the Huygens...

Does someone know a textbook that treats QM without relying on representations much? I mean like saying "lets show that this commutator (momentum and position etc.) is reasonable and then derive everything from that without ever talking about representation much". Moreover is it possible to...

At least, according to this paper - http://arxiv.org/ftp/quant-ph/papers/0206/0206190.pdf - nonlocality isn't real in QM. Thoughts?

Homework Statement Consider an electron of mass m=9*10^-30 kg in an infinite box of dimension a=10^-9 m. What is the energy difference between the ground state and the first excited state? Express your answer in eV. Homework Equations E_n = \frac{\hbar^2\pi^2n^2}{2ma^2} The Attempt at a...

Homework Statement The Hamiltonian of a quantum-mechanical system has only two energy eigenstates, namely |1> and |2>. The system has three other properties, denoted by the observables A, B, and C, respectively. The normalized eigenstates |1> and |2> may or may not be eigenstates of A, B, or...

Hi! I got a Barnes & Noble gift card for my birthday yesterday, and am wondering how to spend it on an introductory book or books about QM. My math background was sufficient to get an ME degree in 1958, and that litttle knowledge is now pretty rusty. I would appreciate any advice concerning...

Hi, I understand that we use i\hbar\partial/\partial t and -i\hbar\nabla for the energy and momentum operator but I would like to know how this identification is made. I can see that it works for a wave of the form e^{i(kx-\omega t)} and using the relation E=\hbar\omega and the relation...

Here's an idea I came up with recently, that I wanted to share: No true black holes exist. Every "apparent" event horizon is really a separation of two universes, where the outside universe is entangled geometrically with the inside universe. The Hubble volume is sitting inside of an...

Hello Forum, I've been reading about MWI, the Bohm interpretation, and Feynman QED. Combining elements from these interpretations, I've been building up my own simple mental model of 'how to picture the state of affairs', and I've been speculating about the feasibility of interpretations...

Hello! I'm quite familiar with non-realtivistic QM and particle phenomenology. What I do really miss is a text, which builds on the postulates of quantum mechanics and stresses the similarities and differences between "single particle" nonrelativistic QM and QFT. I want to read about...

Hi, I am new to QM, so advanced apologies for the dumb questions to follow. What does "the spectrum of boundstates is non-degenerate" mean? And why is the time-independent Schrodinger eqn reflection invariant? (I'm not sure I quite know what that means either...) Thanks!

I watched The Elegant Universe, and it was somewhat disappointing. At the current moment, I only know some of the math of SR, no math of GR, and no math of QM. The special kept giving vague overviews of why GR and QM don't mix. I do know some of the concepts for GR and QM, and I do not see why...

Homework Statement Folks, I am looking at a past exam question regarding the Harmonic Oscillator. The question ask 'Justify that the ground state of a harmonic oscillator a_\psi_0=0 equation 2.58 on page 45 of griffiths. THis was not covered in my notes. Any ideas how to justify this...

Hello, I know that blackbody radiation was one phenomenon whose study contributed to the conceptual development of QM early on. My first question is, what other such systems were considered? I want to know this because I'm closely following the actual order of development of QM concepts, the...

Hi, I have a conceptual question concerning causality and locality in QM. Causality plays a role in second quantization when doing QFT, which one calls "micro-causality"; the commutators between fields disappear when the interval between them is spacelike. However, how does this fit in...

Edit: Sorry I posted this in the wrong forum...I intended to post this in the Quantum Physics forum. Mods would you please move this post to the forum you see most appropriate.I am a newbie in learning quantum mechanics, so please view my opinion lightly: After learning a bit of QM, I feel...

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I have completed Quantum Core courses as well as GR and it seems there is something I am missing before taking QFT/QED courses. Is there another subject between?

Homework Statement A spin-1 particle is measured in a stern gerlach device, set up to measure S_{z}. What are the possible outcomes? In this case, the outcome is zero. The same particle is measured by a second deviced which measures S_{x}. What are the possible outcomes of this...

Hi, a brief question from a confused undergrad, I'm about to start a section of a QM course that deals with the QM nature of condensed matter and think I should get a good idea on this before I start it. I fully understand the wave-particle duality of photon's and electrons and the like, but...

Is it wrong to say that QM is random? Aren't we too ignorant of what's going on at the level of QM to claim with certainty what's going on? How could the Universe be deterministic at the level of GR, but we different at the level of QM. They are both connected, only describing different scales.

Homework Statement Hi Say I have a Hamiltonian given by H = δSz acting on my system, where δ is a random variable controlled by some fluctuations in my environment. I have to show that if I start out with <Sx>=½, then the Hamiltonian will reduce <Sx> to <Sx> = ½<cos(δt)> where the <>...

This is a continuation of discussions from another thread: https://www.physicsforums.com/showthread.php?t=490677&page=2 I believe it deserves its own thread instead of hijacking the other one. "Ref 3" in what follows is this paper: L.E. Ballentine, "The Statistical Interpretation of...

I didn't want to hijack somebody else's thread, so thought I would start a new one for this. There are several interpretations/formulations of QM: Copenhagen, TSQM, MWI, and others. Which one currently has the most favor within the physics community? Why Which one currently has the...

I'm at a UC taking upper division QM, and I get the feeling that the course is designed so as to ignore physical interpretations of equations or the true meaning behind the derivation of the wave function, to the point where I'm having doubts of even my professor's real understanding of the...

The concept of "Center of Mass" is mentioned often in QM literature. I saw one blurb stating that a diatomic molecule could be represented as a SHO vibrating about the "center of mass" between the two atoms. But is there a precise definition of center of mass in QM based solely on the state...