Collapse Definition and 470 Threads

Can anybody explain what is the difference between apparent collapse and collapse? I've read that decoherence leads to apparent collapse but what does that mean, is there an eigenstate after decoherence but its not known why did it occur. I don't understand it all.

I studied lots of points of view, and lots of how physicists actually use quantum mechanics in the applications. I came to the conclusion that there is an objective and a subjective side to quantum mechanics. The collapse belongs to the subjective side, since it is associated with ''knowledge''...

Beta decay, quantum fluctuations, even random vacuum polarizations are all manifestation of collapse, isn't it? The arguments being that in pure unitary wave function, there will be no phase randomization of any kind. Do you consider beta decay as example of decoherence? For decoherence to...

According to the EPR-paradox, if we have a pair of two entangled spin-1/2 fermions A and B and measure z-component of A, B collapses immediately as well(i'm using these letters for both particles and their observers). The 'canonical' solution is then to state that it is not possible to transfer...

I have seen a number of references to apparent experimental "proof" of wavefunction collapse www.nature.com/articles/ncomms7665 However, I am still seeing propagation of the "Many Worlds" theory, which, and I admit that my understanding is limited, but the MW hass at its very core, a necessary...

Suppose I measure the position of a particle, and I find it to be at point C. By deterministic, I mean if we know the wave function of the measuring instrument (and of course also the wave function of the particle before measurement) then we can, in principle, know that the particle is going to...

Homework Statement I'm not sure if this belongs here, sorry if it does not. I am trying to find the most amount of mass a bridge can hold before deforming/collapsing. I was trying to factor stress/ultimate tensile strength into it in a way. Is there a way I can calculate ultimate tensile...

How does the collapse of a wave function influence the results of an energy measurement or a position measurement taken immediately after another energy or position measurement?

I have been learning about the different interpretations of QM, and I am trying to build a taxonomy of them in my mind (I find that trying to build taxonomies is a good way of learning about things). I have read about collapse theories and non-collapse theories. If I have got this right, the...

Upon a measurement of the position, the wavefunction collapses to a spike centered at x0 https://farside.ph.utexas.edu/teaching/315/Waveshtml/img3240.png I encounter similar spike pictures numerous times, but there is an uncertainty in position , it can't be a spike right. First thing I see...

Sorry if this is a silly question, I was just womdering about it. So instead of putting Schrodinger's cat in a box we put in a room and instead of realising poison and thus killing it we push it from from one end of the room to the other end. We will be able to notice that the force of...

This paper;http://arxiv.org/abs/1510.01733, Detecting Direct Collapse Black Holes: making the case for CR7, announce potential detection of a direct collapse black hole. Such a detection would shed light on questions such as the origins of SMBH and galaxies in the early universe.

If they are so insanely dense and their gravity is so mind-numbingly great, what prevents a neutron star from immediately collapsing into a black hole?

Let's suppose you had an electromagnet generating a magnetic field. That field would expand at the speed of light. However, once upon a time, I was told that if this electromagnet were turned off, the field would completely instantaneously collapse, instead of collapsing at the speed of light...

Hi, I've been reading some (very) basic texts on decoherence and have some questions about it: 1. What is the difference between decoherence and dephasing? 2. Assuming decoherence, can we completely do away with collapse theories (i.e. theories in which wavefunction collapse must be...

What are we going to do about it? arXiv:1508.00631 [pdf, other] The fate of a Universe driven by a linear potential Ricardo Z. Ferreira, Pedro P. Avelino Comments: 6 pages, 3 figures Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology...

Excuse my ignorance. I've been googling trying to understand but they always seem to just state it without explaining why. They say the electron could be anywhere within this area of probability but we don't know why until we look and then the wave function 'collapses' and we know where it is...

I read yesterday about a double-slit experiment in which the researchers set up the device ready to make the measurement, but didn´t make the measurement and the wave function collapsed. Then they did it by taking the measurement and it also collapsed. What does it mean that just by setting up...

Why does everyone say gravity collapses and the star explodes? wouldnt the constant tug of gravity never allow this to happen. The fuel burns out and the star collapses why isn't it the fuel is burns out little by little and gravity condenses the star little by little as the fuel burns out.

The modern view of the measurement problem is that any interaction of a particle (say an electron) will cause its wavefunction to 'collapse' in the process called decoherence. No need for conscious observers, interaction with any other particle will cause decoherence hence collapse of the...

I am wondering if there are some views on this. One of the key mysteries of the double slit experiment boils down to when the observation mechanism is placed by one of the slits - and switched on it triggers the change from wave-like outcomes to particle-like outcomes. Is it the observation or...

Suppose the system is in a state of superposition of two determinate states (of an observable) and has equal probability of getting each determinate state, when observed. An observation forces the collapse of the wave function to either one of the determinate state (say, states A and B). Since...

I was just wondering, when particles interact with a force (which would be all the time) , does it cause the wave function to collapse? If so does that mean particles interact with forces in small time periods, since we know particles exist as a probability function? I just assumed that fields...

In the GRW spontaneous collapse model (for example) the wave-function evolves by linear Schrödinger equation, except, at random times, wave-function experiences a jump of the form: \psi_t(x_1, x_2, ..., x_n) \rightarrow \frac{L_n(x)\psi_t(x_1, x_2, ..., x_n)}{||\psi_t(x_1, x_2, ..., x_n)||}...

What does it mean below that in order to keep these theories from violating the principle of the conservation of energy, the mathematics requires that any collapse be incomplete? What is the meaning of complete collapse vs incomplete (and the "tails")...

I'm reading T. Padmanabhans General Relativity. In section 7.6, he describes the gravitational collapse of a sphere of pressureless dust(So ## T_{\mu \nu}=\rho u_{\mu} u_{\nu} ##). I should say his argument is the same as Landau's, but reading Landau's didn't help too. At first, he assumes a...

Whats the circumtances which physics rules collapse and don't work.Theres any explanation it to use mathematics. Here I don't mean singularity things.I know in singularity physics rules collapse I want to talk more generally.

I've recently been reading the book The Dancing Wu Li Masters which is supposed to be a very basic introduction to quantum physics. I have a question on the following quote: "Up to now, we have said that the collapse occurs when somebody looks at the observed system. This is only one point of...

The following experiment claims that it has demonstrated the wave-function collapse: http://www.nature.com/ncomms/2015/150324/ncomms7665/full/ncomms7665.html I would have no problem if they have claimed that, the experiment demonstrated the "non-local" (or: precisely quantum) steering effect...

I'm having a hard time understanding why it makes sense to say that the particle has an uncertain position to which it can collapse, but not to say that the particle has an uncertain time to which it can collapse. Similarly, why do we consider when the particle collapses as when we measure it...

This paper http://arxiv.org/abs/1504.00263, Assessing inflow rates in atomic cooling halos: implications for direct collapse black holes, discusses formation of direct collapse black holes in the early universe. Supermassive black holes are the only reasonable explanation for quasers in the high...

I was wondering if consciousness really causes the wave-function to collapse, and if this is the reason why our behavior is not erratic. Thanks!

While I was daydreaming in my boring math class today I came across a weird problem. What ACTUALLY causes a wave function to collapse. I had a discussion with my teacher the week prior and she was telling me that it has something to do with your brain. I didnt really believe her, I just thought...

So I was reading threads and i came across a question on what happens when a black hole collapses. As I was reading the responses, I saw some people commenting in which they asked if the mass the black hole absorbed was released when the black hole collapsed. If it did would the black hole...

Hi everyone When a momentum operator followed by a position operator acts on a wave vector what does it give? (or the other wave around, changing the order) Is this the collapse of a wave function? And if so, can we solve this to predict the answer or not? I tried but got stuck in the math...

Is there any law that prevents us from accurately measuring the momentum of a particle , just like the energy time uncertainty principle makes us observe the system for an infinite amount of time before we can be certain about its energy? I got this doubt because if we can do it, we will...

Neutron stars are supposed to have an upper limit in mass, beyond which they collapse into perhaps a further type of degenerate matter or a singularity. There doesn't seem to be precisely defined upper limit, but the limit is estimated to be 1.5-3 solar masses. However, a hypothetical neutron...

If there is a big crunch will space collapse with the matter?

I was listening to a discuss about Yemen, and it's unraveling is probably worthy of its own thread. US official: US was surprised by collapse of Yemen govt http://news.yahoo.com/us-official-us-surprised-collapse-yemen-govt-205612576.html Western nations and Saudi Arabia are pulling out...

How long does the gravitational collapse of a giant molecular cloud take? The charged particles acquire quite a huge speed before hitting each other with an impact strong enough to cause nuclear forces take over. This implies that the process of acceleration should take a long time, since...

Roger Penrose suggested that wf collapse is an objective phenomenon caused by gravity. Is there any actual model for this? For instance, how would the nonlocal collapse work with relativity?

Is the collapse of the wave function of the electron in the double slit experiment based purely on the act of observation? Or could it be that the way the instrument used to measure the electron caused it to collapse by how it physically interacted with the electron? Keep in mind the delayed...

http://arxiv.org/pdf/1308.5290v2.pdf I'll just highlight some stuff " "We submit: Doesn’t quantum theory itself, which is a local theory, account for its own predictions? As the authors of this quote know very well, experi- mental data contradict Bell’s theorem [22,23], which im- plies that —...

(I assume that the three section headings below form the template referred to below) 1. Homework Statement n identical equi-distant particles are distributed equi-distantly around the circumference of a ring of radius r in space. Each particles is of mass m, so the total mass of the ring is...

Collapse is the sudden change in wave function after a measurement. Unless otherwise stated, I will assume that neither the wave function nor collapse are necessarily physical, and are just calculational tools that are part of the experimental success of quantum mechancs. Collapse is in almost...

I had a question and I found a thread on PF with a nearly identical question ---Slowly add mass to a neutron star till it collapses. I learned some very interesting physics from that thread, namely the Tolman–Oppenheimer–Volkoff limit, and the significance of "9/8 of its Schwarzschild radius"...

I have wondered this for a while now, what stops large elliptical galaxies from collapsing due to their gravity? Their rotational speed is relatively small, at the rotational axis perhaps zero, so what is preventing the stars from being pulled towards the center? Do spherical ellipticals flatten...

Take the famous double slit (thought) experiment. The wave function for the photon is a superposition of two orthogonal states, one for each slit passage. But it is claimed to collapse into one of these two states when the photon hits the screen beyond, and then continue in this one state. But...

Greetings, I was wondering if anybody knew whether or not the moment of wavefunction measurement is always associated with a high energy. I know that we require smaller and smaller wavelengths of light to probe smaller distances, and since energy increases as wavelength decreases, I was...

The hypothesis that a conscious observer collapses the wave function has been discarded, right? The real reason is that the particle you use to measure the other disrupts the wave function, forcing it to choose an eigenvalue. So since we are able to remove the conscious observer as the...