Qm Definition and 1000 Threads

Many books in QM (eg: Sakurai) mention that the stern-gerlach experiment provides enough motivation for the mathematical structure of QM, Sakurai even mentions Gottfried's book. Point is, i didnt find Gottfried's book, so i am looking for other books that develop the math of quantum mechanics...

What math should a person know to THOROUGHLY understand everything in this textbook(J. J Sakurai. Modern Quantum Mechanics)? (For refrence) cal2 cal3 diffeq1(ode) diffeq2(pde) linealg vectorcalc realanal1 realanal2

spacetime is classical and continuous.. so when quantum system form superposition or entanglement, how is time treated esp in qft? how does spacetime keep track of the particles of fields? or how does the fields or particles able to jump in spacetime.. how is this handle in qm or qft?

I am trying to learn the formalism of qm, so i am following the book linear algebra done right but is it worth it to study every proof? I mean what is the attitude to follow with such a proof oriented book to eventually have a solid basis in the libear algebra of qm?

Homework Statement A quantum particle of mass ##m## is bound in the ground state of the one-dimensional parabolic potential well ##\frac{K_0x^2}{2}## until time ##t=0##. Between time moments of ##t=0## and ##t=T## the stiffness of the spring is ramped-up as ##K(t) = K_0...

I am considering the following question and I want you to agree (but perhaps you don’t):Rutherford wrote a letter to Bohr, as an answer to a previous letter from Bohr containing one of the first of Bohr’s descriptions of the atomic model, saying that he understood the atom model Bohr advocated...

Consider a piece of conductor which is under a DC bias. Solving time-independent Schrodinger equation we have electron wave function which is time-independent and shows special probability for being in each position of the system. How can one say about transmission of electron from one point to...

What would be the virtual particle force acting on a wire, which go's from say Earth to any part of the universe reseeding away from us at near light speed, or grater ?, would it break, and how would we compute it ? Lachlan

i go to school, and it's quite far away (3 hours per day, return), so, i'd like to use this time wisely and learn QM, but unfortunately, i can't read books on transportation, i get dizzy... when i read things for prolong period of time.. i've only learned about the special relativity, and am...

So if we "look" at a particle, then its wave function collapses. Does "look" mean, hitting that particle with another particle (a light particle?). A simple Yes/No answers first please. I mean, does its wave function collapse because we first need to hit that particle with an electron or a...

Homework Statement Starting from E^1_{fs} = \left<n l m_l m_s| (H_r + H_{so})| n l m_l m_s \right> and using E_r^1 = -\frac{(E_n)^2}{2mc^2}\left[\frac{4n}{l+1/2} - 3\right] and H_{so} = \frac{e^2}{8\pi\epsilon_0}\frac{S\cdot L}{m^2c^2r^3} and \left<\frac{1}{r^3}\right> =...

As the title says I am looking for some book to read and understand this world. I know many people say its impossible and that we can learn it by learning the math bluh bluh.. But i have passed 4 quantum courses and i know the math. I just can't get the touchable concepts ( i don't really know...

Hi guys, I'm a newbie in this area of physics and like many other unfamiliar territories, I've had anxiety and confusion when I first heard the intriguing concepts of this theory. I hope someone can help me understand it better though it is evident that it's very difficult and...

Homework Statement The problem asks me to find the expectation value of W. Homework Equations The given ψ[x,t] is Asin(πx/a) e^((-i Eot)/ħ). By QM postulate 2 the QM operator of W is: iħ δ/δt or equivalently -ħ/i δ/δt. The Attempt at a Solution <w>=∫ψ*iħδ/δtψ= iħδ/δt 1/(2e^(-iEot/)ħ)...

This article about a recent experiment was just published the other day: http://phys.org/news/2015-02-hindsight-foresight-accurately-quantum-state.html I can't help but think that this is at least weak evidence in favour of the retrocausal interpretation. Of course other interpretations aren't...

i am currently self studying qm, and i am trying to plan ahead since i am relatively over with griffiths part1 (which is the theory part) and i was wondering if i should go ahead to part 2 (applications) or should i just keep this for later and attempt to stregnthen my basics in qm from another...

1. Is there any reason to interpret the wave function as probabilities of specific states rather than an actual interference of those states? Or are there some types of measurements that are better thought of as probabilities? For example, thinking of the particle as a point-like object with the...

While browsing Wikipedia I bumped into this sentence that seemed partially wrong to me but maybe I didn't understand what it is referring to so would like for some expert to help me elucidate it: "Even if an elementary particle has a delocalized wavepacket, the wavepacket is in fact a quantum...

https://www.amazon.com/dp/9384007447/?tag=pfamazon01-20 I cannot find any reviews for this book, yet i found in a nearby library literally hundreds of copies.. So anyone heard of the author or that publisher med tec? I actually bought it and i found it quite easy but radically different from...

Homework Statement ##\int_0^\pi \sin^{2l+1}\theta~d\theta## Homework EquationsThe Attempt at a Solution I have no idea how to proceed with integrals of this type, and I can't find any similar examples online. If someone could give me some info on these types of integral, or direct me towards...

Does anyone know how Wheeler understood QM? Here are some well-known sayings of his (slightly paraphrased): "the wave function does not represent the electron- it represents what we know about the electron; the joint product of all the evidence that is available to those who communicate" "it is...

I want to read a book on mathematics behind QM and by that, I don't mean just functional analysis. Its been a long time that I hear about things like *-algebra, C*-algebra, Weyl algebra, Heisenberg group, Stone-von Neumann theorem and things like these and I want to understand them. Can anyone...

1. Problem: Consider the composed system of two particles of spin ##s=1## where their angular momenta is ##l=0##. What values can the total spin take if they identical? What changes when they are distinguishable? The Attempt at a Solution : The problem I have here is incorporating the fact...

1. After finding out that the wave function ##\Psi(z) \sim Ae^{\frac{-z^{2}}{2}}## in the limit of plus or minus infinity Griffiths separates the function into two parts ##\Psi(z)=h(z)e^{\frac{-z^{2}}{2}}## My question will be about a certain aspect of the function ##h(z)## After solving the...

Hello, I recently read that MIT redesigned its EECS program. It redesigned it about 30 years ago to include more mathematics and solid-state physics but this time they are adding more QM. At my university, we study basic QM in freshman year physics and then again in third year in an EE subject...

In non-relativistic QM, the probability postulate works very well in position and momentum space. But, I have read that in relativistic QM (Dirac or QFT), the probability postulate in position space does not work because the corresponding probability density function is not Lorentz covariant...

1. In Griffiths, in the section where he discusses the 'total' spin of two spin 1/2 particles (''Addition of angular momenta'') he starts of using a notation new to me. Namely ##\chi=\chi_1\chi_2## where I know what ##\chi_1## and ##\chi_2## represent independently, which has been discussed in...

In QM, the energy operator is proportional to the time derivative E ~ d/dt So higher energy particles have higher frequencies, i.e. their wave functions change more often per time than when at rest But in SR, higher energy particles seem to exist in slow motion, appearing to age little How...

There is soooo much misinformation out there that for the non-physicist, it is difficult to know whether to trust one source or not. So, one thing I do not understand is, based on what I've read, how QM does or does not require consciousness. It seems a debate that has been going on almost...

Can anybody tell me about the book 'Quantum Physics' by Stephen Gasiorowicz? You can give some comparison with other books such as Griffiths or Shankar's QM book.

Hey guys, I love to read and learn about Quantum Physics and have been looking for good suggestions on books. I don't want a complete beginners book, I am an Electrical Engineer so I have a decent background in math and physics, by no means am I am expert. I love all the theory behind QM but...

This question is about both quantum mechanics and special relativity, so I wasn't sure which forum to post it in. If mods think it's in the wrong forum then please move it as you see fit! My understanding is that in special relativity, we live in a four-dimensional "block universe" of...

I think it's the idea that things exist even before we measure them, correct?

Let's say Bob and Alice are passing through a lab on their way to lunch. In the center of the lab is a big table with some kind of experimental set up. They are curious about it and both silently examine the whole thing (there is an unrelated lecture going on nearby so they are silent and...

I recently read the published article: Stuart Hameroff, How quantum brain biology can rescue conscious free will. Front Integr Neurosci. 2012; 6: 93. PMCID: PMC3470100 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3470100/ From this it seems that current neuroscience views consciousness as an...

Hi I was watching a TV program about QM on BBC4 given by Jim Khalili. I am a little confused by two aspects. First, he attempted to draw an analogy about polarisation of entangled particles always being opposite when measured, by using a card game where a dealer deals cards in pairs. I think it...

Just to clarify: I only have very rudimentary knowledge of Physics, so please correct me if I am wrong. This thought came to my mind after I discovered some youtube videos and articles on the double slit experiment: AFAIK, if the information of which path the electron takes is obtained, there...

Homework Statement Find <r> and <r2> for an electron in the ground state of hydrogen. Express in terms of Bohr radius. Homework Equations We know the relevant wave functions are: R_{10} = \frac{c_0}{a}e^{r/a}Y^0_0 and Y^0_0 = \frac{1}{\sqrt{4\pi}} The Attempt at a Solution As I...

Hey guys, I'd like to ignore Hamiltonian mechanics and use a specific example of the many particle Schrodinger equation in Griffith's chapter 5.4 to try to get to statistical mechanics, and see what happens, I need help making sense of it: Given 3 non-interacting particles in a 1-d potential...

Hi everyone, so I need someone to go to a public library and 'steal' somehow (scanning or simply photo with a smart phone) pages 34 and 56 of Dirac's original edition of his groundbreaking 1930 book called <The Principles of Quantum Mechanics>. I myself cannot do that from where I am, not to...

Am I correct in assuming that if there is a potential present and it is not infinite then integrals will always be made from minus infinity to infinity, but where an infinite potential exists then the integral will depend on the size of the confinement area? Sorry to be a little disambiguous...

Often I see QFT texts introduce dirac spinors by comparing them to the two component spin states (which I have come to accept are also spinors) in NRQM. And arguing that since the NRQM spinors transform via SU(2), our desired quantum fields for spin 1/2 particles should be some higher...

Homework Statement A particle in one dimensional space, $$H=\frac{p^2}{2m}$$ in time ##t=0## has a wavefunction $$ \psi (x)=\left\{\begin{matrix} \sqrt{\frac{15}{8a}}(1-(\frac{2x}{a})^2) &,|x|<\frac a 2 \\ 0 & , |x|>\frac a 2 \end{matrix}\right.$$ a) Calculate the expected values of ##x##...

I have read many explanations of Bell’s proof that mention in passing something like “According to QM, the correlation between measurements of spin at different angles should be given by the cosine of the angle between them.” Sometimes they talk about 1-cos(x)/2. Sometimes they talk about...

Generally, all that matters is the amplitude of the wavefunction. You usually can't even MEASURE the phase unless you are making a particle interfere with itself. With photons, however, the real & complex components seem to appear as electric and magnetic fields. Is there anything equivalent...

In quantum mechanics, the position operator(for a single particle moving in one dimension) is defined as Q(\psi)(x)=x\psi(x) , with the domain D(Q)=\{\psi \epsilon L^2(\mathbb R) | Q\psi\epsilon L^2 (\mathbb R) \} . But this means no square-integrable function in the domain becomes...

I'm looking for good books to give me some more "taste" on beautiful aspects of QM. I'm actually studying for my undergraduate exam on the 27th november that comes in a strong academic flavour and would love a relaxed but deep reading. For example i totally loved Robbins's "What is...

When a changed body is accelerated in EM field, it is just a macroscopic net effect of multiple interactions of charged particles in that body with the other changed particles outside. When we say "particle accelerator", it is still a simplification, because particle is not being accelerated in...

Hello =) I have a question regarding the conservation of probability in quantum mechanics. We know that the probability of a measurement of a given observable, is preserved in time if the observable commutes with the Hamiltonian. But this is also true if the value of the measurement...

Hello. I was told that "in QM the information doesn't disappear". Does it mean that, in QM, the trajectory in the phase-space can't split? [The typical example is a vertical simple pendulum, with the mass above the spin-point; in classical mechanics you can't know if the pendulum will fall one...