Quantum Theory

Imagine that you had one photon traveling alone in space. Because of the particle-wave duality of photons (and pretty much every type of particle), this photon would not only travel as a particle, but as a wave too. There are 2 ways that I can imagine this, and I'd like to know which one seems more accurate. 1) As a wave, the photon propagates from a central point of emmission in all directions, and as a particle, it exists at a point somewhere on the crest of the propagating wave. It doesn't have an exact position being in a state of superposition, and only has a probable position. 2) As a particle and as a wave, it is at a precise position in space and traveling…

In the classic experiment, particles sent through a single slit behave as if they've been sent through a single slit, while even if sent one at a time in a direction with two slits, they display an interference pattern after enough have been sent to make a pattern show up. That still dosn't explain really how each individual particle KNOWS it has a choice of two slits... right? How is this mathmatical change distributed through the path of the experiment? It must happen instantly, therefore the effect travels faster than light - but no force can travel faster than light - as it needs carriers of that force to interact with. What if the very act of creating an…

http://www.bottomlayer.com/bottom/reality/chap2.html#n2 The above site describes what I presume is the classical scenario, i.e. an electron emitter, two slits, an electron detector at each slit and a screen at the back. Several variations are presented, the following two for example: 1) The electron detector at each slit is kept on but the information not recorded. The back screen still indicates a wave distribution, showing that the electron detectors by themselves did not interfere with the results. 2) The electron detector at each slit is kept on and the information *is also recorded*, but before the back screen is examined, the detector info is erased. T…

What I really wanted to ask about was how they derived those funny looking shapes for orbitals. I understand it has something to do with quantum physics (hence the reason I posted this in QM). The funny looking shapes I'm refering to are the regions of highest probability where you'll find an electron around a nucleus. It used to be described as a spherical cloud of negative charge surrounding a nucleus, but now you've got some that look like donuts, others that look like light bulbs stemming off one side of the nucleus. Some have several such light bulbs stemming 90 degrees from each other, and so on. How did they derive these shapes?

hello, I would like to know briefly how the Bloch wave is simliar to a wave function of an electron and what's the difference between them also how did the Bloch wave affect the energy of the electronic band I hope you can understand what I ask as I was just reading some elementary books about it thanks

what is the division between quantum rules and classical rules? atoms, molecules, ect.? is there a blurry area where it is kinda both or is it a division at x size?

I read somewhere that the tension and therefore energy of a particular string, namely the graviton, is some enourmously large tension (don't recall exact number). Therefore, the string has a tremendous amount of energy and thus mass, however the book also says the mass is cancelled by quantum uncertainty, how is this accomplished? Wouldn't the quantum flux be upward toward a higher mass/energy just as it would be downward towards zero mass?

I possess varius textbooks about QM, and in them they always show the Hamiltonian of simple things, like electrons or harmonic oscillators, but I wonder which is the hamiltonian of a more complex thing, for example a human body

Hi y'all, Working myself at walking pace through Shankar's "Principles of Quantum Mechanics", there is some intreguing jump towards Hamiltons canonical equations that I'm missing. It could be something obvious, since Wikipedia doesn't provide any additional info either. So far, the canonical momentum in Lagrangian formalism was defined as p= dL/dq(dotted) Terribly sorry, but I can't get the LaTex working... and I know that should be partial derivates, and also imagine the p and q's being indexed. A certain deduction, which I still understand results in dH/dq = -dL/dq The strange thing, which I don't understand at all, is that dL/dq is equalled t…

Quantum mechanics boldly points at several contradictions from many references. First the atom wave duality experiment gives us reference that there is no reality, the inhibitions of accuracy, and the endless debate on causality or predetermined universe. Is anyone still currently studing this field and why?

This is a spin-off from the FTL/entangement thread: I've been reading papers describing a series of undergraduate experiments with entangled photons and they employ laser-fed down-converters to ensure conditions for coincidence counting to work, etc... and, well, doesn't the physical process within the laser cavity itself create entangled photons? I guess I''m thinking the partial reflection of the light produced and the small size of modern lasers (as pointed out in another thread) might produce a variety of entanglements..?

To all who dare: This thread is not a disertation claiming any QM inclusion. The topics are QM in scope and there are many obvious similarities in problem recognition, but this isn't QM, so I will not be responding to QM responses unless critically relevant. Nonllocal force centers are localized in the chasnnel obstructions of Stern_Gerlach segments when performiong standard S-> T -,> S trransition experiments. The following is part instructional (we all need to pseak the same lanuage) and part formal descriptioon of physical systems. The transitions are seen in the sideview of the segments (3rd and 4ty figuress_ segment. However, for those unfamiliar wi…

Right... I understand quantum tunneling, I understand how it is used in quantum tunneling transistors, but I do not get how quantum tunneling is related to these pressure cables or buttons as seen here: Cable: http://www.maplin.co.uk/Module.aspx?ModuleNo=44296&doy=11m5 Pressure button: http://www.maplin.co.uk/Module.aspx?ModuleNo=44202&doy=11m5 How is tunneling, which is to do with particles crossing potential barriers or wells which they don't classically speaking have the energy to do, related to wires which: Can anyone help?

As a firm believer in causal determinism, the (frustratingly inseperable) probabilistic nature of quantum always irked me. I had always relegated the Heisenberg Uncertainty Principle to a strictly observational problem and thought of the Schrodinger Equation as an observational abstraction which provided a model for generating probabilistic distributions to account for unobservable information. I recently read a paper by Gerard 't Hooft of Utrecht University (http://www.phys.uu.nl/~thooft) entitled How Does God Play Dice? (Pre-)Determinism at the Planck Scale (PDF). There's also an accompanying presentation. He asserts an "information loss" hypothesis for non-deter…

This was partially proposed in this thread: http://www.scienceforums.net/forums/showthread.php?t=10803 And it really got me thinking. So here's a quick proposal. We have locations A, B, and C, with AB and BC being equidistant (let's say they're one light day each) Our goal will be to quasi-instantaneously transmit a message between A and C. B is a setup containing the following: A laser emitting single photons at short and regular intervals, fired through a beam splitter which in turn passes either path through down converters. The photons streaming out of this device travel a day until they reach their destinations. C directs the two possible b…

I've heard of it, but I've never really been sure what it is. As far as I know, it is the fact that when two particles interact they are forever effected by each other no matter how separated by space they become. So, if you did something to one particle, the other particle would be effected even it was half way across the galaxy. Am I on the right track?

I read somewhere that this symmetry somehow connects fermions and bosons together, how does it do it? What exactly is supersymmetry? (sorry if this has been asked already)

hey guys im new, and erm im 15 so go easy k? im only just into quantum physics an im still learning but if u guys cud tech me i'd be grateful to learn more (thanks!) neway on to the thread, u guys think im a pathetic little kid with pathetic sci-fi ideas. but hear me out, im working on a theory (based on einsteins wormhole theory) about a) whether its possible to travel thru time and b) how it is possible. now the idea is still in fuition so ill need data, specifically how much (or an equation wud be nice) energy does it take to create a black hole of minimum size? (dont take de mickey plz guys, im only lil lol)

From the Quantum Gravity thread we had: Ed's Quantum Gravity paper can be found here I understand about virtual photons, but how can a virtual photon be turned into a real photon???

Simple Enough, Who's smarter? Neils Bhor by far in my opinion, his revoloutionary ideas on quatum mechanics have acctually proved Albert Einstein wrong, and so if Albert Einstein was to acctually accept Quantum Mechanics, then he would have to abandon e=mc^2. (Warning, Intellect may be required!)

If every time we collapse the wave function of an electron and know for a fact where the little bastard is, how did we come up with the idea of a probability wave in the first place?

Do you think it is possible, in principle at least, to build a particle accelerator which will collide protons at super-high energies of up to 10 PeV? In order to test superstring theory we'll probably need to 're-create the creation'. This is not possible with current technology because the energies required are trillions of trillions of times larger than the hydrogen bomb. Although such a complex design will probably not be finished in my lifetime (and probably not before 2100), i believe this is achievable. Also the problem is that the structure might take the size of half the solar system. The greatest mystery is what really happenes at temperatures of…

I've doing some research of QM, and this specific topic has confused me some. According to a website I read, light act as a wave due to the probility of a photon being in a certain location that exhibits properties of waves. At least, that's what I think it said... here's the site http://www-theory.chem.washington.edu/~trstedl/quantum/quantum.html It gave this analogy to explain this phenomenon. I'm not sure if this is the greatest example, but I still don't understand it completely. I have a hard time grasping the concept of the propabilty of a particle acting as a wave. Can someone explain any better please?

Is the emission spectrum of an element the same spectrum of light that it will emit when photons emit light after excitation? For example, is hydrogen's emission spectrum the same as the light it emits when excited (or two-step upconverted, etc)? If not, how can one go about finding the emission spectra from de-excitation of an electron in an atom at the first and second energy levels (up from natural state, in other words, the first and second excitation levels)? Sorry if my terminology is a bit... Off.

Sorry if this is in the wrong forum. I was reading several books on the topic of time and was wondering what are your thoughts on the question: "does time move" Do you think its just SciFi or fantasy or do you think this is an actual occurence. Also what is your thoughts on multiple universes.