What is Mwi: Definition and 129 Discussions

In another thread, @Nugatory asked "how exactly does it turn out that both spacelike-separated observers end up in the same world without some appeal to non-locality?" Worlds are defined by their observed macroscopic values. They separate through decoherence. It is a physical process. Since...

I am sorry to bore you people with a very, very simple question (there is no catch unless QM throws it :nb) ): ?:) If we have a half silvered mirror and we fire a single photon at it at an angle of 45°, it either passes or reflects from the mirror. To be more precise, the photon becomes in a...

Forgive my novice question; but, how does one explain the fact that decoherence doesn't contradict the evolution of the wavefunction in every world? Meaning, how is causality preserved in each world and what concept of time is professed wrt. to each world in the MWI? In other words, it seems...

I believe that anything is possible. If technology became so advanced, that it was suddenly possible to peer into any of the other worlds (in the infinite number of many worlds suggested by MWI) and see what was happening. What do you think we would see? What technology would be needed? What...

Hi guys, I am new to physics forums and am an undergrad who is really interested in the philosophical implications of quantum physics. I know this isn’t a philosophy forum but upon skimming older threads regarding MWI I have come across an interesting number of posts by a few members named...

Hi all, Suppose we have some particle in state $$|\Psi\rangle=\frac{1}{\sqrt{2}} (|U\rangle + |D\rangle)$$ It starts interacting with its environment, including Experimenter 1 (E1). From Experimenter 2's viewpoint, this can be represented as: $$|\Psi\rangle=\frac{1}{\sqrt{2}} (|U\rangle...

The wave function as it approaches the screen in the double split experiment is extended all over space. How does the MWI (multi worlds interpretation) account for the energy hf of the particle being deposited on a very small area and producing a spot there rather than in a more extended area...

I'd like to see an instance where experiments can end in mwi because it seems it never ends... example.. if the radioactive source emits alpha, it triggers an explosion and Schrodinger is dead. If it didn't he is alive (we often use Schrodinger's Cat example with the consequence we never think...

My question is, "Is superposition necessarily and only related to the time between triggering and observation?" And further on that point, in the MWI theory, as opposed to the Copenhagen interpretation, do quantum particles actually enter and "exist" in a superposed realm before observation? Or...

When a system gets entangled to the environment or to the observer and the world (or observer) is duplicated. What happens to the potential and Hamiltonian, does it gets duplicated or entangled too. I'd like an actual example of a system with a potential or Hamiltonian where I can analyze this...

There seems to be a lot of discussion on the Many Worlds Interpretation here at the present time and it's something that I personally can't get into very deeply. The reason I can't be bothered too much about it is because I can't help feeling that the whole concept is nonsensical. I base this...

Suppose there are two independent experiments taking place \left\vert \Phi\right\rangle =\alpha _{1}\left\vert \phi _{1}\right\rangle +\beta_{1}\left\vert \phi _{2}\right\rangle and \left\vert \Psi \right\rangle=\alpha _{2}\left\vert \psi _{1}\right\rangle +\beta _{2}\left\vert...

It seems many people even experts don't understand the basic of MWI. In the double slit.. what is wrong with the statement that "that observer will "split" as well--one version of him for each way the double slit experiment came out.". Peterdonis wrote it. And I included it in a thread as...

Did you notice MWI assumes the brain is classical and when we watched the double slit, "that observer will "split" as well--one version of him for each way the double slit experiment came out." MWI assumes the so called easy problems only. Before I proceed. Please read short paragraph of...

Just a reminder to you all, I am just a layman... These experiments were both done is what is called a penning trap. I think this only proves the version of MWI where the universe doesn't actually split. The "bare" theory, where no new matter is created. According to MWI an electrons...

For the difficulty of getting a preferred basis in the unitary only MWI. I saw this message by Fredrik: "If we just let it go, it seems very natural to me to (if we insist on trying to interpret QM as a description of the universe) postulate something like "every 1-dimensional subspace of the...

How does MWI deal with the destruction of interference in the double slit experiment when a detector is placed at the slits? Since the wave function never collapses, and the universe doesn't actually split in MWI, how does the interference go away? Does the measuring device at the slits reshape...

Doesn't the Many Worlds Interpretation violate Lorentz symmetry when the universe splits?

Just wanted to check if my understanding is correct. So, it is not important who makes the measurement first of the entangled pair, Bob and Alice decohere the particle with each other independently, creating a "spectrum" or Alices and Bobs on each side. This is trivial, local and there are no...

So in MWI, the electron takes many paths through the double slit experiment and each path is in a different world. So if electrons are fired one at a time, what makes an electron go on a certain path. Say it goes on some weird path that would have implied that a force exist when viewed...

The purpose of this post is to describe what may be a useful way of viewing some aspects of QM. It probably doesn't rise to the point of a testable theory. Over a year ago I argued against the Many Worlds Interpretation based on quantum conservation of information. My argument was this: Any...

I am just looking for an answer to this question-- Does the Many-Worlds Interpretation demand that every physically possible scenario has to be played out somewhere in the Multiverse? David Deutsch has told me that yes this is true (including absurd/ unlikely scenarios...although those would...

I have a long-standing question regarding the fundamental nature of macroscopic QM in combination with MWI. First, generally speaking, what does the Born rule say about macroscopic objects and experiments (without superfluids and other traditional examples of quantum behavior on the large...

Suppose we measure a normalized state ##|\Psi \rangle = \alpha _0 | \lambda _0 \rangle + \alpha _1 | \lambda _1 \rangle + \alpha _2 | \lambda _2 \rangle + ...## with ##| \lambda _i \rangle## the eigenvalues of the measured observable. Is it true that, in the CI, the wavefunction collapses into...

I have a few questions regarding Many Worlds Interpretation (MWI) Terminology: QM is just the math, doubted by none; MWI and CI (Copenhagen Interpretation) are ontological interpretations. David Deutsch believes MWI with certainty. He even says that it's "proven" experimentally. How many...

Hi guys, I was listing some older threads regarding mwi and I found an interesting number of posts by a member named vanesch. So let me first say that I don't want to start a philosophical discussion because this is clearly a physics forum, but he analyzed the 'mind body problem' in a...

Hey guys, I want to understand the basic assumptions of MWI in quantum physics. So one of it is that all possible states exist in different universes, and that's relatively understandable although weird. Now my problem is the splitting of the universes and how and when does it happen. Example...

Suppose we fire a photon P at a polarisation filter F1, and it passes the filter, thus forcing the polarisation of P in an eigenstate M1. Subsequently, the photon falls through a polarisation filter F2, forcing P in eigenstate M2. Now, if I understand correctly, the probability of P passing F2...

Please check my logic. 1. Feynman diagram is a tool to calculate 'final state' from an 'original state'. It is mostly used for simple processes, like scattering. 2. 'Final state' usually have a precise meaning due to observation of particles trajectories. 3. However, in MWI there is nothing...

Hello all, On Cosmology webstie I found the article about Time Travel,Uncertainty Principle and Many Worlds. Here is the quote: "DeWitt’s many-worlds interpretation of Everett’s work, posits that there may be a split in the combined observer–object system, the observation causing the splitting...

I'm alittle confused, is it saying that all the fundamental particles in the universe are really just one wave function?

Could someone explain Jan-Markus Schwindt's idea, published under the provocative title Nothing happens in the Universe of the Everett Interpretation please? Frankly I can't even understand the opening paragraph of the abstract. http://arxiv.org/abs/1210.8447 Since the scalar product is the...

And by "this" I mean this article http://arxiv.org/abs/1305.0168

Everett created the Relative State Formulation in order to resolve the contradictions, as he saw it, of QM. He introduced his doctoral thesis by stating that conventional QM works perfectly well - it predicts quantum statistics. However, interpreting conventional QM realistically leads to...

"We can’t make a measurement without influencing what we measure. before we look, there are only probabilities. When we open the box, they give way to a single actuality" It would be more like this, all the time, Until we look...

I did some cursory searching, and I couldn't find this idea being discussed, so I thought it would be a good idea to bring it up here. Is there any reason why a valid explanation for baryon asymmetry isn't that we happen to live in a world branch where there was a significant asymmetry in the...

How would MWI explain the delayed choice quantum eraser? http://en.wikipedia.org/wiki/Delayed_choice_quantum_eraser#The_experiment_of_Kim_et_al._.282000.29 I don't see how this can be explained with MWI. If the idler photon hits detector 1 or 2, an interference pattern can be seen on the...

If the same particle is measured with spin up in one universe and spin down in another (at the same time), is it absolutely required in MWI that they both have the same history? That is. Why couldn't the paired universes have different histories, but the different histories lead up to the same...

Hi to all. :) First of all I'm not cleary a physician, not even an amateur, only a writer and i hope that a so low level of knowledge don't offend anyone ^^' (my bad level and my broken english :look: ) So: I have a question about the MWI. According with the most serious interpretation: we...

Is this evidence for MWI?Or other explanations are possible? http://en.wikipedia.org/wiki/Elitzur%E2%80%93Vaidman_bomb_tester#Step-by-step_explanation Any thoughts?

Do nested quantum events prove the Many Wordls Interpretation of physics 1) First create quantum events that surround other quantum events like a photon path that circles a fissioning element, if the photon usually takes 100 times as long to reach the detector per each fissioned nucleus...

I recently read an article entitled, "The Interpretation of Quantum Mechanics: Many Worlds or Many Words?" authored by Max Tegmark and it raised many questions on the matter as well as curiosity. In the article, Tegmark provides two tenable but diametrically opposite paradigms regarding physical...

Hi Just finished the chapter on the Multiverse in David Deutsche's excellent book The Beginning of Infinity. His explanation of how discrete values change from the multiverse perspective is brilliant. In it he explains that there is no such thing as a 'quantum jump' and that what 'changes'...

According to this link: http://www.stumbleupon.com/su/7ZF6uJ/io9.com/5757404/awesome-discovery-of-the-week-glass-melts-when-it-gets-too-cold ... Glass, it turns out, is the exception. Once it gets close to absolute zero, it melts again. ... My question: “Now, according to what I am...

Many physicists claim that decoherence determines the emergence of the worlds in the Many World Interpretation (MWI). I have always found such a claim elusively proved and actually wrong. Recently I wrote a paper: http://arxiv.org/abs/1008.3708 addressing such a subject, and I sent it to...

In MWI does everytime something splits it splits into an infinite number of worlds? Can something continue to split forever? If MWI is true does this mean for example that every proton in effect consists of an infinite number of indistinguishable protons and that every person consists of...

Can anyone provide it? I just examined wiki article just for fun, it is a mess of different concepts (because, as I understand, there was an attempt to make it interpretation-neutral) So, can anyone provide a definition which is MWI-compatible? For example: in MWI any 'particle' behavior...

The MWI and the Anthropic "Principle" How is it that the MWI and the Anthropic "Principle, " which is especially distasteful, are regarded as compatible? It seems to me they are totally incompatible.

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...

Why is it that MWI's problem with special relativity is rarely discussed? From: http://plato.stanford.edu/entries/qm-everett/ A final problem is that it is unclear how to formulate a splitting-worlds reading of Everett that is compatible with the constraints of special relativity. Suppose...