Collapse Definition and 470 Threads

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...

Hello, As I understand, the following formula describes the Jeans length. \lambda_j = \sqrt\frac{15k_BT}{4\pi G \mu P} Where \mu is the mass per particle. Forgive me if this question may come across as relatively stupid, I imagine that each of the particles within the cloud...

Hello, Does a star collapse directly to form a black hole without creating a supernova or whether a supernova forms some neutron stars which after crossing the TOV limit forms a black hole? Thanks.

I don't want to argue about whether the notion of "wave function collapse" is a good way of understanding quantum mechanics, or not. For the purposes of this discussion, let's just adopt uncritically the naive approach to quantum mechanics, that: Between measurements, the system evolves...

Hi, I've done a lot of personal research on the internet trying to understand what exactly is happening in this experiment but I keep seeing contrasting information about what the role of observation actually had on the experiment. What I understand is that when they try to figure out which...

Have you recently came across and remember titles of papers about real experiments concerning the famous double slit electron behaviour? I have found some about electron diffraction, but I'm still looking for those that showed how interference pattern is broken when we watch where the...

I was trying to understand wave function collapse in terms of superposition, but I ran into some problems when relating back to information theory/entropy. It is given in the definition of information in terms of entropy energy is needed to transfer information. That is something we have always...

Homework Statement A particle is in the state 1/2 |1> - 1/2 |2> + 1/2 |3> - 1/2 |4> A detector is placed to measure state |4>. What the particle's wave function collapses into, if the detector does not find a particle Homework Equations <i|j> = delta (i, j) The Attempt at a...

This comes from this thread https://www.physicsforums.com/showthread.php?t=647627&page=7 discussion in posts #103,#104,#107 and #108. The Oppenheimer-Snyder model was mentioned by PeterDonis as a more plausible model than the Schwarzschild spacetime, well this has an element of subjectivity...

Let's assume: - we have standard civilization collapse (let's ignore the reasons, but assume that whatever the event was it devastated everything quickly and there are no serious additional lingering effects like significant fallout) - there is low amount of remaining people and they are...

Hey guys, I was reading a book about the philosophy of science, and in the chapter about QM the author uses a well known example in order to explain quantum entaglement and illustrate the non-separability of individual system in QM. He describes a system composed of two spin-1/2 particles...

Here is a question I would like answered. The wave function I am going to use for this example is the ground state of the infinite well but I assume the outcome to this problem will apply to any wave function. Ground State: ψ = √(2/a)*sin(∏nx/a) , where 0 < x < a Lets say that I know a...

I need to show that the critical (Jeans') mass for a hydrogen cloud of uniform density to begin gravitational collapse can be expressed as: M=(v^4)/((P^.5)(G^1.5)) Where v is the isothermal sound speed, and P is the pressure associated with the density ρ and temperature T. I don't...

Does anyone know of a review article on astrophysical collapse to a black hole? There are several statements I've picked up from WP that either surprise me or that I'm not sure I understand. This Penrose diagram http://en.wikipedia.org/wiki/File:PENROSE2.PNG shows the singularity as being...

i was going through the quantum mechanics book by griffith and on the very first chapter i read that the wavefunction of the quantum particle collapse on measurement. and if the interval between the succesive measurement is shorter the particle will be found at the very same location. the...

I have some doubts about the implications of the orbital angular operators and its eigenvectors (maybe the reason is that I have a weak knowledge on QM). If we choose the measurement of the z axis and therefore the Lz operator, the are the following spherical harmonics for l=1...

Hi all, I'm doing a practice question in which we have a hydrogen atom in the state: \psi = (2\psi_{100} + \psi_{210} + \sqrt{2}\psi_{211} + \sqrt{3}\psi_{21 -1})/\sqrt{10} It says that, now a measurement is taken and we find the angular momentum variables to be L = 1 and L_z = 1. The...

So, in QM making a measurement collapses the state into an eigenstate of that observable. Thus, if the system is properly isolated, then the same measurement should return the same value. But the eigenvalue for that state is degenerate, then does that mean the state might actually collapse to a...

Are there any well-known/well-studied examples of an ecological collapse of two species that interact in a obligately mutualistic kind of way? As in, an extinction (or severe decrease in population) in the two species Also acceptable is a sudden increase in population (but that seems less...

I'm curious as to whether or not there is a connection to be drawn between the phenomenon of wave function collapse and the idea of Bayesian inference. I began thinking about this within the context of one of the variants of the Monty Hall problem. If you have one kid, what's the probability...

I don't know if I got this right, but as far as I know, if you are able to deduce through which slit the particle went through, it behaves classically, if you have no way of deducing through which slit the particle went through, it behaves in a quantum way (interference pattern). Now, I don't...

I know very little about QM, so forgive me if this question is a bit difficult to comprehend. I understand that there is some debate about whether a conscious observer is necessary to collapse the wave function. But I was wondering if there was any experimental evidence showing to what degree a...

I've read that string theory suggests that black holes may be stringy fuzzballs without a singularity at the center. Instead, strings pile up all the way to the event horizon. My understanding of non-stringy black holes is that the gravitational compressive force overcomes all known repulsive...

I have what is probably a very basic question about the Schrödinger's cat thought experiment. As I understand it, in order for the counter tube to break and release the deadly poison, the Geiger counter must measure whether or not an atom decays. So, why doesn't that measurement collapse the...

Hey guys this is my first post so I hope this doesn't come out stupid since I only know slightly more than a layman. Recently I have been trying to wrap my mind around what happens inside an event horizon. Specifally I have been confused with the matter which resided inside the schwarzchild...

Hello, I need a help for making a short visual presentation of superposition and wavefunction collapse. It will be a power-point presentation for young students. I have an idea to show a superposition as a "perfect noise", which can be visually achieved as a uniform gray background or total...

MIT researchers forecast "global economic collapse" by 2030 http://news.yahoo.com/blogs/sideshow/next-great-depression-mit-researchers-predict-global-economic-190352944.htmlAnything we don't already know? Can anyone find the actual study?

i am an A-level physics student (high school if you're american) and for a research topic i have chosen wave particle duality. i have been able to explain the ideas of diffraction, double slit experiments, photo electric effects and electron diffraction easily enough, but we are expected to take...

Ok so when observed, the wavefunction collapses, can someone delicately explain the maths behind it? Or send me to a page with a coherent explanation, that is followable for a first year undergrad? I've covered Eigenvectors briefly in my algebra course last semester and i find that the...

I have a question regarding Young's double slits experiment. To my understanding, wave function of a photon somehow collapses according to the probability function (which has a interference pattern). But at the very moment the wave hits the screen, it seems to me that there should be no...

This question has gone unanswered by our friends in nuclear/atomic threads. My question relates to a solitary Tc^99m decay in particular, and to gamma rays in general. If light is a collapse able wave function, are different wavelength energies the same, ie gamma, x, radio, etc. My...

Hello, I was wondering what exactly happens when you observe part of the wavefunction of a particle, does this always cause collapse? Or only when the probability distribution decides that the particle is indeed there? What I mean is, is an observation in the form of photons interacting with...

As I understand it, the term "collapse" is a little over-exaggerated, but why is it that we measure things as points and not waves even though particles exist as waves?

Homework Statement Hi, I have been given a question where they want me to find out the time at which gravitational collapse occurs for a given radius. So for reference I had a read through my notes... most of it I understand with the exception of a bit which I will highlight below. Thanks...

Collapse of WTC towers... Hi all, I am a Layman in physics unfortunately, this is my first post so be kind please. I Know that an object accelerating downward exerts less force on the part below than if it were being held in place, But how does this relate to the top section of the WTC...

I'm guessing if Quantum Mechanics get modified to allow for physical collapse, the Schrodinger equation is modified. But whatever has already verified Quantum Mechanics thus far, the new theory needs to account for those results but, I would assume, make different predictions in other areas that...

I'm trying to at least understand what decoherence can and cannot explain about how quantum mechanics works, the more I read, the less clear I am about what is known and what is merely speculative. So I finally decided the only way to get any further was to try and clarify what I think is...

How does one obtain a collapse of the wave function in Bohm Mechanics? The pilot wave is guided by the Scrodinger equation - but how do definite states arise?

consider a atom who's single electron is made to jump into conduction band ,after some time the electron will come into it's valence band by releasing the quanta of energy but if an observer observes the electron in it's excited state continuously it's wave function will collapse to bring about...

Simple question. So the energy of a particle is observed to be E_1 (for example) at time t=0. At time t=0 the wavefunction psi(x) collapses to phi(x)exp(-i(E_1)t/h). At time t>0 the wavefunction is also in this state (right?). Is it in this state until it interacts with another particle or...

The postulates of quantum mechanics include: (1) Schrodinger's equation describes how the wave function of a system changes over time, and appears to make the wave function continuous over time. (2) When a measurement is made of quantity m, the wave function instantly changes to an...

The Oppenheimer Snyder Collapse into a black hole does it happen in finite time for local and remote observers? Does a trapped surface really form in finite time?

1. Will wave functions collapse in a photon double-slit experiment after we place a detector at one of its slits and detect one photon? 2. Will wave functions collapse in a photon double-slit experiment after we detect a photon on the screen? 3. Will wave functions collapse in an electron...

I know dumb question but If you observe with your eyes using a laser pen and two microscope slits does the wave collapse as opposed to closing your eyes while the light passes through the slits and then observing the defraction pattern on the wall? Also is it the measuring device that causes the...

What is the experimental evidence that a wavefunction will collapse to a dirac delta function, and not something more 'smeared' out?

Dear generous and helpful physicists, A number of threads here contemplate strategies for transmitting information faster than light by observing an entangled particle in one place, allegedly causing the wave function of its entangled twin to instantly collapse in another, far away place...

So, if our observable universe was less than a centimeter across, why didn't it collapse into a super black hole? The gravitational field of all that matter... inflation seems weird when you think that it could become into a big black hole (and it didn't; right?)

What's this? http://finance.yahoo.com/blogs/daily-ticker/now-u-postal-belly-153600714.html They have 650,000 people on the payroll (1 person serving every 461 Americans). One would think at least a few of those 650k have the training and smarts to figure out how to restructure the post...

If consciousness causes collapse, then wouldn't physics shortly after the big bang be different?

Imagine body that has mass and volume such that it is just a bit short of turning into the black hole. Now let's say that the body has been around for some time and has reached present state in some smooth process so that it can be in equilibrium state if such an equilibrium exists. I assume...