Collapse Definition and 466 Threads

Hi, I was wondering whether we are sure (I know, strong word) that decoherence is the mechanism that takes us from the quantum world to our classical world. Correct me if I'm wrong, but basically decoherence is a phenomenon where we have a bunch of quantum states that, when piled onto each...

So at some point nuclear fusion in a star becomes unable to sustain the core against its own gravity pressure, then the core collapses and the surface explodes in supernova explosion. What actually happens when the core collapse that makes the surface explode, and why would the core not explode...

Hi Everyone I am not sure of what exactly happens when a wavefunction collapses but I have some ideas about which I would be grateful for your thoughts. Firstly, it is often said that wavefunctions collapse when they are "observed" or "measured". To be honest, I do not think that...

Now I'm trying to imagine the wavefuction before and after collapse when measured at either slit. Before the particle enters the slits I imagine the wavefunction more as a planar wave with no definite position (single wavenumber and a superposition of positions). If no measurement is made then...

Hey everyone.I have a couple of question regarding wave function collapse. I can accept that one cannot make a measurement with absolute precision and have a usable wave function afterwards due to the uncertainty principle... Consider a particle moving along the x-axis with a wave function...

Pardon me for my ignorance. This is a question of curiosity. I look for a concise logical argument as to why the community believes the following hypothetical situation and explanation is wrong. What justification is there for believing in waveform collapse at time of measurement? Is it...

Does the measurement problem ("wave function collapse") or something similar somehow manifest itself in QED and other quantum field theories? Is it somehow built-in into the propagators etc. "away from sight"? If so, how does it affect the theories and is this a problem, which needs to be...

I am looking for a mathematical solution of the following "paradox" regarding the Oppenheimer-Snyder collapse of a finite sphere of dust. Suppose the sphere of mass M has just collapsed to its Schwarzschild radius R_S(M) = \frac{2GM}{c^2} 1) Suppose there is another thin shell of dust...

After a measurement a wavefunction collapses. You measure the position of a particle, the particles assumes a definite position, let's say point C. The coefficient of C is let's say c, so the probability that it takes that value is c² Wavefunction collapses at C (actually in the vicinty of C...

Hey. Given that if you measure the energy of a wave function, the wave function must collapse to the eigenstate corresponding to the eigenvalue measured. Does that mean when you measure the energy of a wave function it must collapse the wave function into one of these stationary states...

Hope this isn't too simplistic, but; Type 1a supernovae tell us gravity is constant for as far as we can observe Type 1a also provide evidence that the rate of cosmic expansion is accelerating Wouldn't the early universe have at some point been below the density required by the...

Hi, I've know that accelerated charge generates electromagnetic radiation which eventually should cause the electron to crash into the atom nuclear, until Bohr atom model. Suppose that we have a mass which cause to gravitation field. If this mass will be accelerated, will it radiate...

I know several raytraycing results for static Schwarzschild black holes, but I have never seen something similar for collapse models like Oppenheimer-Snyder or Vaidya. Are there reliable raytraycing results showing the effect on light rays from far distant light emitters observed by (far...

I'm sitting on a bench in a park. I exert a force of H Newtons and the bench exerts a reactive force of H Newtons back and we're in equilibrium. Next to me a 10ft tall short-faced bear sits on an identical bench with B Newtons. After about 20 seconds the bench gives in and collapses. I...

Once a wavefunction has collapsed, can the system change to a new state if we disturb the system? For example, if we have a particle in a state of well defined energy (e.g. ground state) and then suddenly change the potential of the particle, can it change to a new state (e.g. excited state)...

I know there are many wavefunction collapse models - but with regards to the Copenhagen interpretation the idea is that a measurement will cause something to collapse into a particular state. What does the term "measurement" refer to? It makes one think of only something that a conscious being...

Hi. I was wondering about this. In the "Star Trek" movie of 2009, the destruction of the planet Vulcan is shown, by a black hole being formed in its core. I'm curious: supposing you had some means to create, or collapse part of the planet to form, a black hole in its core, what would, according...

Hello physics forums, Say you had a hollow steel sphere of thickness 1 mm and diameter of 1 meter (from outside to outside)? Inside the sphere is gas at 1 atm pressure. Outside is 1 atm of pressure. How much gas would I have to remove from the inside until the sphere collapsed from...

Homework Statement Calculate the kinetic energy generated when a white dwarf in a binary system accretes enough material to increase its mass beyond the Chandrasekhar limit (1.4 solar masses) and collapse to the radius of a neutron star. radius of white dwarf- 5520 km radius of neutron...

Homework Statement So say I have a 1 qubit normalised state |ψ> = 1/√N(c1|z+> - c2|z->) and I make the measurement Sx and the measurement yields +hbar/2 as |x+> is a superposition of both z+ & z- basis eigenstates does the collapsed state end up the same as the original state? Or would I need...

I came across this statement by bhobba in another thread and it got me to thinking, if the "environment" itself is capable of collapsing the wave function, then how is it possible to produce an interference pattern in a double slit experiment? After all, the particle isn't traveling through a...

How does the Copenhagen interpretation motivate its claim that the wave function of a quantum system collapses when a property of the system is being measured? I mean, was there some problem they were trying to solve by introducing the notion of wave function collapse? What would happen if the...

In the "closed" Friedmann model, there is a Big Bang in the past and Big Collapse in the future. Big Bang singularity is something different than a Black Hole singularity. Now my question: is the Big Collapse singularity mathematically equivalent to a Black Hole (localized) singularity, or is...

Homework Statement Using physics knowlege, why do some electricity pylons collapse in extreme temperatures. Homework Equations The Attempt at a Solution Don't know the physics formulas or equations that could be used. High winds would force the pylons to collapse as the structure hasn't been...

In QM theory entangled particles or photons are in superposition for spin (spin up or spin down) or for polarization angles. When one of the space like separated pair is measured for a spin or polarization observable, the wave function collapses and the other particle is then in a...

Hi all, I was wondering mathematically ,what causes wave function collapse? and why does it exist in all it's Eigen states before measurement? Thanks for any help and please correct my question if I have anything wrong.

I have read about the Stern-Gerlach experiment in Wikipedia, this experiment proved that electron spin could only take two discrete values. The experiment consist in sending neutral charged atoms through a inhomogeneous magnetic field so it would change the particle’s direction a quantity...

Is this a proper summary of a minimal-no-collapse interpretation? (I like to call it the fuzzy world interpretation, but I suppose I'm the only one) When objects entangle, it constrains their degrees of freedom. As they entangle with more and more objects, their degrees of freedom are...

A few new student questions: following collapse of the waveform, does the waveform ever reform? If so, and if entangled particles are involved, does the entangled twin reform as well? And if so, does this require forward progression in time, in other words, might the entangled twin decollapse...

In flat spacetime, there isn't any problem with wave function collapse. I think that's the "textbook" position, although the only citation I have off the top of my head is the discussion in http://arxiv.org/abs/0706.1232 (section 1.1). How about in curved spacetime (working in the regime where...

I understand how conservation of momentum leads to planet formation and planet rotation. However, after studying this model, I have ran into a point of confusion that I cannot find the answer to: Why don't the planets collapse into the sun just as dust particles collapsed inward via...

Assuming a planet suddenly got enough mass to be a few orders of magnitude more massive than the sun, the planet would collapse to form a black hole, right(irrespective of the core material?)?

Homework Statement An interstellar cloud, made up of an ideal gas, collapses with its radius decreasing as $$R = 10^{13} \left(\frac{-t}{216}\right)^{2/3} \text{m}$$ with ##t## measured in years. The time ##t## is taken to be zero at zero radius so that ##t## is always negative. The cloud...

I'm otherwise pretty comfortable with the postulates of quantum mechanics, but I find it difficult to understand situations where a measurement causes only incomplete collapse of the wave function... Suppose we have an electron in a state described by some wave function. Then we measure its...

Apologies if these questions have been answered before - I didn't have any luck with google. Something has bugged me for a while about quantum experiments like Schrödinger's cat where a 'black box' system is theorized to be in a superposition of states until observation causes wave function...

Relativistic Quantum Mechanics exist. But I don´t understand, it would must be see contradictory. He has the locality postulate, contradicting the collapse in a extensive system objects entangled. Yes, it is and old question: EPR, Bell Iniqualities. But I don´t know what is the final solution to...

I am just starting out in self-study for quantum theory, so forgive me if my question seems elementary or completely misguided. In quantum mechanics, every wave function ψ can be decomposed into a linear combination of basis functions in the following manner: \Psi = \Sigma{c_{n}\Psi_{n}}...

Is there an exact solution for the spherical symmetric collaps of pressureless dust? Can one see a Schwarzschild solution for r > Rdust with shrinking Rdust(t) ?

Consider a macroscopic Bose-Einstein condensate. Are there experimental results regarding the propagation (in space and time) of the collapse of this state caused by a point-like perturbation?

I have read in several places (such as this StackExchange reply) that wavefunction collapse is 'non-physical'. The explanations I have read seem clear and understandable to me and have helped me to understand EPR and the implications of Bell's Theorem. I am trying to reconcile this in my mind...

Hey I heard somewhere that bubbles underwater that are collapsed by sound waves produce light, to me this in no way makes sense can anyone explain is it like swamp gas that the fabled UFOs are

I propose a simple thpught experiment; A scientist A measure the spin of an electron and finds it "up". After that he removes all evidence of his experiment and goes away, only to die in a road accident. Another scientist, obviously unaware of the experiment done by A come and measures the...

Hi , I want to read the following paper : S. W. Hawking, \Breakdown of Predictability in Gravitational Collapse," Phys. Rev. D 14, 2460 (1976). But can't find a free version . It's not on arXiv so if someone can help me out , It would be appreciated . By the way ,Another paper that I need...

Hello All, I am trying to understand how stars are formed and thereby came across Jeans instability. I am new to this subject, however I went through concepts of molecular clouds, nuclear fusions and things like that. The Virial theorem says E=(1/2)U As sum of potential energy U and...

When the sun is collapsed will it form a black hole?

I think space-time exerts a pressure on substance and it makes star to transorm black hole.I think this can be possible becuse we know that space-time is something which it can be tiltled and it can creates virtual matters.Space-time is real thing.So Can be space-time exert pressure on substance ?

Phase of the star's death ,when star's fuel ended,we know that it will collapse into itself Why do stars collapse in on itself ? How to collapse in on itself ? Although the end of the fuel in the star,how to collapse in on itself? Because inside the star there is no...

Homework Statement A cloud consists of 8 solar masses of hydrogen gas (H2). Its temperature is 20 K and its radius is 0.6 light years. Will it collapse? Homework Equations Mj=3kTR/2Gm 3/2kT<GMm/R The Attempt at a Solution m=2 x 1.67 x 10^-27 G=6.67 x 10^-11 k=1.38 x 10^-23 T=20...

Homework Statement A cloud consists of 8 solar masses of hydrogen gas (H2). Its temperature is 20 K and its radius is 0.6 light years. Will it collapse? Homework Equations jeans mass [b]3. The Attempt at a Solution [/b I've tried to use jeans mass to solve this however I am finding...

1. In the many statements of the QM postulates that I've seen, it says that if you measure an observable (such as position) with a continuous spectrum of eigenvalues, on a state such as then the result will be one of the eigenvalues x, and the state vector will collapse to the...