Collapse Definition and 470 Threads

If you were to measure an electron's spin, for example, will the wavefunction associated with its position also collapse?

I've always been confused about something -- I'd love for someone to clear up my ignorance. I understand that the position of a particle can be modeled as a wavefunction (a probability distribution, to my understanding) where we can describe the position as fundamentally random, but it takes on...

in a double slit experiment, if we find which-way and then stop observing the photon and send it again through another double slit (kept in, say, series), would an interference pattern occur?...the second time around

Why dark matter can not collapse into a black hole under it's own weight?

Hello, I am a beginner on the sbject so please correct if I'm using some sloppy terminology. I'll try to be clear. Consider a Hamiltonian with degenerate energy eigenstates (say the degeneracy is on angular momentum as in hydrogen atom). Which of the degenerate eigenstates would the wave...

Hi, I'm an 11 year old kid so I won't get any mathematics too complicated, but I don't want an answer simplified too much. So in schrodingers cat experiment, the cat and the Geiger counter used to detect the decaying atom do not decohere the system because they are a part of that closed...

Can you give example of systems that self collapse? For example, is radioactive decay an example of self measurement? How about 13 billion years ago when stars were just being formed, is it an example of self measurement? Because I can't imagine how stars can form when all things are in...

since erasure of which-way can "restore" the entangled photons back to the "wave-state" can we conclude that the information (of the wave state stays) even during collapse?or let me explain via double slit if we get which-way...we can expect disappearance of interference pattern however if we...

non-locality and the collapse of the wave-function of a single photon I'm a bit of a layman on english and on physics, so here it is. My questions are about the collapse of the wave-function of a single photon in the general sense. I will mention where I mean to pose a question. If we may...

I’ve been fascinated with the different QM interpretations since I discovered them… but I want to sort of restrict my imagination to more solid ideas. I know about the Double-Slit experiment and that there are many misconceptions about the correct definition of an ‘observer’ and what role the...

Hello: I know it's a rather subjective title. But I am no expert in the subject and I've read a lot of information in the Internet that is contradictory. I have read that the collapse of the wave function requires interaction with an observer. But is that collapse in any way related to the...

Can you make a measurement that doesn't make the particle completely collapse into a single state, but partially collapse dismissing just some of the possible states?

Hello, there is a subject of wave propagation and collapse that has plagued me for some time, and although i must have heard about it, my memories are probably skewed ( i studied EE and had high frequency, physics of materials and nuclear/quantum physics sometime in 1970s :) as subjects). In...

Hi! I have a plan to build my own version of young's experiment using various household items, a laser, and my physics textbook. My question is about what I could use as a "detector" to observe and collapse the wave function? I had the idea of making a tiny inductor to go around one of the...

Is it possible for the wave function collapse to be partial because you don't measure everything at once. Can you cite an example? I read someone mentioned that it's only the superposition relating to the measured quantity that collapses and the superpostion is just expressing the state...

Hello everydody. Well i need to write a repor (5 pages maximum) about Core Collapse of Massive Stars to my discipline Stellar Structure and Evolution . The problem is that i have read some books like https://www.amazon.com/dp/0387580131/?tag=pfamazon01-20 and i have no ideias. I gained...

　 We know Copenhagen settles for computational rules connecting human observations rather than striving to comprehend the nature of the underlying reality. Heisenberg eventually did try to form a coherence picture of what is actually happening. But how come this Heisenberg Interpretation is not...

Scientists/Physicists/Truth-seekers, I am looking for answers to some questions, which I confess are issues of gobbledygook debates. But this time I want serious and simple answers. So no debates please. My questions are as under:- Is wave-function collapse a REAL incident or just a...

Homework Statement Estimate the gravitational potential energy released in the collapse of a 1.2 solar-mass core from an initial density of 10^9 g/cm^3 to a final 10^15 g/cm^3. Homework Equations The Attempt at a Solution The book doesn't provide much guidance on this. I was thinking of...

Would it be fair to say that before an observation, a wave-particle is in a superposition of many possible states but that after the observation, the wave-particle is found only in one state? Would that be analogous to saying that it goes from behaving in a very wave-like manner to behaving...

Hi, I'm currently studying GR from Wald's book. The book is fine, but I want to know more details about the collapse of stars, e.g., more about white dwarfs, neutron stars, mass limits, the use of Fermi-Dirac statistics in this cases, etc. What book, paper or website would you recommend?. (I'm...

Understanding that the reason for keeping the water inside of an upside down water bottle is negative pressure and gravity, I decided to make a water feeder for my chickens. I had a shutt-off valve on the water bottle. Set it upside down at waiste high. Then I attached a long plastic hose to...

The Schwarzschild solution to the field equations is a vacuum solution for a spherically symmetric mass and provides the Schwarzschild radius: rs = 2Gm / c^2. Is there a similar treatment for a cylinder that would give its radius and height as a function of mass?

Hi all, I recently came across one of the proposed mechanisms by which black hole could be formed as stated above.Can someone please explain me what is it all about? Also what's their relationship with type IA supernovae? I always thought that, a black hole is formed only when a main sequence...

Hello, I was reading a book on Quantum Mechanics by Manjit Kumar, and read at the part of the Bohr–Einstein debates about Einstein's box to measure the weight of a photon. Now I was wondering, how can a Star collapse if it's constantly losing so much weight?

If matter goes from a superposed state to a collapsed state when measured, how did scientists see the interference pattern in the double slit experiment, doesn't the surface that the photons hit after passing through the slits count as a measuring device? Also, is there any updated...

Homework Statement Consider a harmonic oscillator. It is in the ground state. Momentum is measured and is found to be between 0.2 \sqrt{}m\omega hand 1.5 \sqrt{}m\omega h. (h here is h bar) Energy is now immediately measured. What is the probability that the energy is unchanged? You may...

"Decoherence does not generate actual wave function collapse. It only provides an explanation for the appearance of wavefunction collapse. The quantum nature of the system is simply "leaked" into the environment" http://en.wikipedia.org/wiki/Quantum_decoherence I have taken a full year of...

When a body collapses under gravity, its initial gravitational potential energy is converted to kinetic energy and/or other forms of internal energy. At least that is how it is described in Newtonian gravity (not sure if this question is well-formed in GR, sorry). Now say that the collapse...

This is with respect to the Elitzur–Vaidman bomb-tester. Where the of wavefunction of photon is going to collapse is not known accurately. It is said that a given photon takes both paths in the Mach-Zehnder interferometer and MAY collapse if it meets an obstacle (Bomb). few questions: 1...

Say you had a very flimsy canister. Would it be possible for it to collapse or implode even if the pressure inside it and the pressure outside of it were equal, due to the fact that it has thickness and therefor a greater outside surface area than inside surface area? If so, are there real...

Homework Statement To show how conservation of angular momentum applied to to a collapsing MC core implies flattening during cloud collapse consider the equation of motion of a parcel mass m in a rotating initially spherical cloud of total mass M, initial angular speed w0 and radius r0...

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Hi. I have a simple question- Does the wave function describe probability of finding a particle in a certain state upon collapse of the wave function?

N.B. I am not trying to send information back in time or generate infinite free energy (also I couldn't find how to delete the other thread but could a moderator please delete it for me) If you could send classical information signals faster than light, then according to relativity you could...

Okay, so I am no expert in this field, but would like to acquaint myself more with quantum mechanics. As I understand it, the collapse of the wave function according to MWI only appears to occur, when really the observer is copied into as many different histories or worlds as there are possible...

Hi guys, Quantum mechanics gives well-defined probabilistic predictions for the value we get when we measure position or momentum; one simply takes the absolute square of the wavefunction in either the x-basis or the p-basis. However, I am not so clear on how we would predict at what time we...

Homework Statement stars form by gravitational collapse of interstellar gas clouds. use dimensional analysis to estimate how long it takes for a cloud with a density p=Mo pc^-3 to collapse Mo= 1.9898e33 g Homework Equations The Attempt at a Solution I just have no idea how to use...

I have a question I havnt been able to figure out by reading or googling: If we have an entangled pair of particles, and we measure one, thus collapsing its wavefunction, 'when' does the other particle collapse? 'Instantly' begs the question of 'in which reference frame?' For instance...

The question I want to ask is pretty much in the title: Why is string theory becoming less of an excitement amongst the scientific community? I don't want to sound picky, but my background in physics is pretty inferior. I understand that the explanation is mainly in the mathematics, so, just...

Okay, let me begin by saying that I do NOT have a good foundation in quantum mechanics, but I have been completely captivated by the wavefunction collapse. I have looked over many explanations of the double-slit experiment over the course of a few months, and I cannot find that one single...

How much time does it take for wavefunction to start re-evolution after its observation is over? Or how does it evolve? I think, considering feynman path formulation, it should start evolving instantaneously, with wavefunction ending at edge of light cone (light cone that has its tip at the...

I'm still wrestling with the whole uncertainty principal / wave function collapse idea. Obviously a basic building block of QM, I'm having a hard time understanding the real world evidence which supports these QM piles. 1. So from my understanding, the uncertainty principle tells us it is...

A lot has been written about the relative merits of decoherence versus the many-worlds theory in answering the question: where does the extra information go when a superposed state "collapses" to a definite state. However, what about the reverse: when the definite state returns to a new...

I think that the wave function is the description of a particle's position at a point in time. But I'm not precisely sure what an eigenfunction is and how it is different. I know that certain eigenfunctions return certain values, and that even if you do not have a certain eigenfunction you can...

Hi. I've asked the question many times (as I'm sure many others have) why does the particle behave differently once it has been observed? Does that not mean it knows it has been observed? How does it know? The only answer I get is: "observing destroys the wave function" , but that doesn't...

So, rookie question, I know, but I'm having a little trouble with the idea of wavefunction collapse as it pertains to stationary states: If a measurement of energy collapses a wavefunction into an energy eigenstate, it stays there forever (unless perturbed). But my impression is that although...

finding the collapse load "P" i am taking a course on solid mechanics, and we are learning plastic deformations in transverse loading, in this question i am asked to find an expression for the "collapse load P" as a function of its placement on the beam "x" i do not remember learning the...

It is my understanding that a measurement of S_z followed by a measurement of S_y will result in a particle which is in an eigenstate of S_y . But it appears that a measurement of say S_y followed by a measurement of S_x results in zero. I see this from a question in which I am asked to...

If Dark Matter is made of particles, then wouldn't it be possible to have clumps of it collapse into a black hole? Would there be any radiation from that collapse that we could see? Would that radiation be distinct from the formation of normal black holes? Shouldn't we be able to measure the...