This tag is for questions relating to what, if anything, the quantum mechanical formalism and experimental results say about the way the world works.

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2answers
104 views

Do conservation laws contradict quantum mechanics? [on hold]

Take for example the double-slit experiment interpreted in the Copenhagen sense. The particle leaves as an object with mass, yet passes through the slits as a massless wave, only to collapse again as ...
-1
votes
0answers
66 views

Quantum mechanics and probability quick question [closed]

After reading some articles about quantum mechanics and probability I came up with a conclusion - there is a nonzero probability of existence for every world which is deemed as a fantasy world, with ...
5
votes
1answer
163 views

Calculate the entropy per atom in Bohmian Mechanics

Bohmian mechanics description of a large number of interacting atoms would require a large phase space due to the large number of classical degrees of freedom. The entropy per atom is given as the ...
2
votes
3answers
276 views

Is Bohmian Mechanics incompatible with loop corrections?

For those who continue to be unsatisfied with Quantum Mechanics (QM), Bohmian Mechanics (BM) is an alternative worth considering. It is sometimes claimed that BM is equivalent to QM, but Lubos Motl ...
1
vote
1answer
79 views

How is no-conspiracy theory compatible with determinism? [closed]

Bell's theorem states that any physical theory that incorporates local realism and the no-conspiracy assumption cannot reproduce all the predictions of quantum mechanical theory. Hence, we cannot ...
5
votes
5answers
134 views

What is the explanation for the interference patterns in MWI?

In Young's double-slit experiment, MWI states that in some "worlds" the particle goes through one slit, and in others it goes through the other. If this is so, why do we get an interference pattern? ...
-1
votes
1answer
51 views

What is the difference and/or similarity between multiple universes in inflation and in quantumphysics? [duplicate]

Some theories propose that there are more universes. In one of them it is said that there are parallel universes, due to inflations after the big bang that created them. But in the two-slit ...
0
votes
1answer
83 views

In the many worlds interpretation of q.m. what makes a superposition af states split in two sepearate ones?

I was wondering, what agent makes a superposition of, let´s say, the two spins of an electron, máke them split into two separate ones (up and down). And is this not in contradiction to the law of ...
5
votes
2answers
142 views

Bell's theorem and fluid-mechanical experiments using droplets: are local hidden-variable theories possible after all?

Recent fluid-mechanical experiments by the groups of Couder in Paris and Bush at MIT, mimic a surprisingly wide range of quantum effects. The essential ingredient of these fluid-mechanical systems is ...
0
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0answers
66 views

Can't many-worlds interpretation explain wavefunction collapse?

According to the many-worlds interpretation when universe splits in interaction, the observer in each universe measures corresponding pure state thus seeing collapse. Well, it may be an ...
6
votes
4answers
2k views

Does physics claim that every possible world has or will exist? [closed]

Has physics proven that every possible world has or will exist? Someone on-line, who actually seems fairly intelligent, but troll-ish, claims that there is good reasons for it, not from any ...
1
vote
0answers
64 views

Why not measure the velocity of a quantum particle by $\frac{\Delta \vec{x}}{\Delta t}$

Why is it not possible in quantum mechanics to measure the velocity (and thus momentum) of a particle just by two position and time measurements and get it approximately by $$ \vec{v} = ...
0
votes
1answer
46 views

Multiple measurements and the any worlds interpretation

My question has some similarities to but also differs significantly from this question which was described in many of its answers as not being a quantum mechanical measurement and was I think, ...
3
votes
2answers
119 views

When does the world split in MWI

I've been reading Eliezer Yudkowsky's blog post regarding decoherence and many worlds, and although he is not a physics but a strong proponent of MWI, I can basically see why he feels that MWI is a ...
0
votes
0answers
42 views

Interpretation of a case of the double square well

Consider a 'double square well' potential (where $E < 0$) defined as: $$V(x) :=\begin{cases} -V_0~~~~~~~~~~~~~\text{for }\frac{b}{2} < x < \frac{b}{2} + a \text{ and } -a - \frac{b}{2} < ...
0
votes
0answers
29 views

Statement of vector model of angular momentum in Eisberg and Resnick

While serving as a teaching assistant for a sophomore-level Quantum Physics course, I came across the following paragraph in Eisberg and Resnick regarding orbital angular momentum (section 7-8, page ...
3
votes
1answer
81 views

Is the trajectory of a quantum particle a well defined concept and how does this depend on the interpretation of quantum mechanics?

A common statement about quantum physics is that the "trajectory" of a particle is no longer a well defined concept because of the uncertainty relations for position and momentum. If one interprets ...
2
votes
1answer
46 views

Question about Bell's Theorem and hidden variable equations [closed]

I am trying to understand Griffiths explanation of Bell's theorem in chapter 12 of 2nd edition Intro to QM (or the afterword section A.2 in the 1st edition). He starts with given two detectors ...
0
votes
2answers
82 views

Quantum mechanics interpretation clarification

My question is based upon this video here: https://www.youtube.com/watch?v=PC0zHIf2Gkw From 9:00-10:00 Max Tegmark says an isolated galaxy with an observer inside will not evolve according to ...
0
votes
3answers
65 views

Einselection locality in decoherence theory

Consider two polarity-wise entangled photons A and B in an EPR experiment. The process of measuring the polarization of photon A by Alice is described by the decoherence of the 2-photons system ...
0
votes
1answer
121 views

How can all information be localized if local realism is dead?

I'm confused about whether quantum mechanics is local or not. The authors of a recent, much publicized experiment argue that their results "imply statistically significant rejection of the ...
3
votes
3answers
123 views

Does the canonical commutation relation relate to the fact that momentum is the generator of spatial translations?

In classical mechanics momentum is the generator of spatial translations. This remains true in quantum mechanics. The way we define the momentum operator in one-dimension, for example, already shows ...
1
vote
0answers
96 views

What is the justification for continuing to model space-time as a manifold in string theory?

Background The question I have arises from taking seriously the idea that, in a physical theory, one should first define all physical quantities via (thought) experiment. Justification and ...
2
votes
3answers
206 views

What's so confusing about quantum physics? [closed]

Okay, just right off the bat, I want to make it clear that this is a stupid question. Check out this graph, from SMBC: Ignore the 'political discourse' part and replace it with 'talking about ...
2
votes
2answers
302 views

Does recent paper show Bohmian mechanics is correct?

The following paper was recently featured in a German science magazine (Spektrum der Wissenschaft): "Experimental nonlocal and surreal Bohmian trajectories" (DOI:10.1126/science.1501466) The abstract ...
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votes
5answers
209 views

Quantum Theory just lazy physics?

Is it true that physicists decided that because they couldn't predict with certainty the location of an electron at any given time, that they just created equations using probability instead, still ...
1
vote
1answer
95 views

Controlling the universe through the “Many-worlds” interpretation [closed]

I was reading upon a comic when I found some interesting content concerning the "Many-worlds" interpretation and how it could be used in quite an extreme manner. Imagine we had a "END" machine. When ...
2
votes
2answers
72 views

Many worlds and “extreme” worlds

I assume there are worlds in the MWI where extremely improbable things (improbable according to our world) have happened repeatedly. Broken eggs reform themselves repeatedly etc... Will scientists in ...
2
votes
4answers
160 views

Many worlds interpretation of quantum mechanics

From my layman's perspective, it feels like the many worlds interpretation is invoked out of the inability to explain why one observation occurs out of many possibilities. Given no explanation why one ...
5
votes
3answers
163 views

Successor to Copenhagen Interpretation as Orthodox Interpreation of Quantum Mechanics

First, I read the questions FAQ for this and I hope this does not violate the rules. I am not asking for personal opinion, but for observations of hard evidence of trends on this subject. When I ...
5
votes
1answer
121 views

Help needed to understand “On the reality of the quantum state”

I am having trouble to understand the reasoning in the following paper, On the reality of the quantum state. MF Pusey, J Barret and T Rudolph. Nature Phys. 8, 475–478 (2012); arXiv:1111.3328. ...
3
votes
0answers
78 views

Decoherence and interpretations

With quantum decoherence, are there still any "gaps" in our knowledge of quantum mechanics that hint (either in terms of the physics, philosophy, or otherwise) at the need for further interpretation? ...
3
votes
2answers
148 views

How does the Physics work for the Quantum Suicide thought experiment?

On page 5 of this paper written by Max Tegmark, Tegmark discusses a thought experiment called 'Quantum Suicide'. As far as I understand it, this experiment was created to show the experimental ...
2
votes
1answer
63 views

Many-worlds interpretation (MWI) and conservation of energy [duplicate]

I am not an expert of many-worlds interpretation (MWI), and what I say may be stated incorrectly. In that case i welcome corrections. If the MWI is true and it explains quantum theory and it splits ...
2
votes
2answers
136 views

Meaning of “realism” in quantum mechanics

When physicists doing work in quantum measurement, decoherence, Bells' inequalities etc. use the term "realism" what exactly do they mean? I'm looking for answers targeted towards, say, someone whose ...
3
votes
1answer
70 views

Does a particle “exist” between emission and detection?

In considering a simple Young's double slit setup: The classical idea that a particle must exist with defined position and momentum between the source and detection plate leads to philosophical ...
0
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0answers
64 views

How does one intrepret probabilites in the many-worlds interpretation?

Let's say I flip a coin, and don't look. From the copenhagen interpretation, the state of the coin is: $\frac1{\sqrt2}(i|\text{heads} \rangle - |\text{tails}\rangle)$ If I observe the coin, there is ...
2
votes
2answers
176 views

Can multiple timelines exist according to theoretical physics? [closed]

Multiple timelines is not a reality yet (as of 2016's science and technology), but exists only in Marvel/DC universe. It is something that is used to explain the paradox of time-travel. If you go back ...
0
votes
2answers
212 views

Many-world interpretation: simple physics explanation? [closed]

We went a little off topic in physics class today and my teacher was explaining how quantum physics explains the idea of parallel universes. She believes in a idea called many world interpretation ...
2
votes
3answers
147 views

Does valid interpretations of quantum mechanics always reduce to trivial arguments about the equations? [closed]

This is the editted 'short' version of the question :) Interpretation is very important in physics, but physics is governed by equations. With bare equations, physics would be just mathematics. ...
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votes
2answers
169 views

What stands behind the quantum nonlocality appearing in entanglements, and why Bell's inequalities are violated?

I noticed the question whether Bell's inequalities are based on a false premise, (Could Bell's Theorem be based on a false premise?) but I bring another argumentation of the question. Also I ...
2
votes
0answers
90 views

What would be the abilities of a wave function collapsing oracle? [closed]

Although the Bell's theorem dismiss local hidden variables as an explanation of the quantum variability, there is nothing to prevent an observer to see the occurrence of a wave function collapse as ...
-1
votes
1answer
68 views

Probabilistic realism

On consideration of Bell's inequalities and this Why is quantum entanglement considered to be an active link between particles?. Either localism or realism has to be given up. Can't we have a ...
0
votes
1answer
54 views

Does quantum mechanics separate ontology from gnoseology? [closed]

I mean this answer here. Laws present to us what we know (what we may know). But what we know cannot define what is real; it only defines our actions & assumptions. We may know only probabilities ...
5
votes
2answers
449 views

Is the many-worlds interpretation (MWI) of QM inconsistent with quantum field theory

I had recently posted a question on the Philosophy stack exchange about "true" randomness, and a lot of the discussion centered around Quantum Mechanics. One of the responders claimed: MWI has the ...
1
vote
1answer
99 views

Does “sum over all paths” in the path integral imply “sum over all paths” in momentum space when one Fourier-transforms?

How is the Fourier-transformed-field path integral interpreted? Is it still a "sum of all paths" in momentum space? Just that with another action? Consider for instance the (Euclidean) partition ...
1
vote
1answer
88 views

Many worlds probability of getting cancer [closed]

My understanding of probabilities in many worlds is following: If I would decide to start smoking and we know that 10% of smokers get cancer that means that in 10% of all worlds during my lifetime I ...
0
votes
2answers
87 views

Light interference single particle 4 slits experiment - what are interpretations apart from many-worlds interpretation?

Someone knowledgeable about physics advised me to read a book "David Deutsch: The Fabric of Reality, 1997". The book gives experiment like two-slit one, difference is that 2-slits compared to 4-slits ...
2
votes
1answer
161 views

Double slit experiment and pilot waves [closed]

Why do almost all books on quantum start out with the double slit experiment and show how a single particle interferes with itself and say its a wave and particle when Yves Couder has shown on a ...
1
vote
1answer
84 views

Bohmian trajectories vs. Feynman path integrals, continuous paths?

After reading some of the other posts online, I'm clear on the fact that Bohmian trajectories (of the de Broglie Bohm formulation) and the paths of the Feynman path integral formulation are very ...