Log in
Register
Search
Search titles only
By:
Search titles only
By:
Forums
New posts
Forum list
Search forums
Leaderboards
Games
Our Blog
Blogs
New entries
New comments
Blog list
Search blogs
Credits
Transactions
Shop
Blessings: ✟0.00
Tickets
Open new ticket
Watched
Donate
Log in
Register
Search
Search titles only
By:
Search titles only
By:
More options
Toggle width
Share this page
Share this page
Share
Reddit
Pinterest
Tumblr
WhatsApp
Email
Share
Link
Menu
Install the app
Install
Forums
Discussion and Debate
Discussion and Debate
Physical & Life Sciences
Non-Mainstream and Controversial Science
Parallel universe theory in quantum mechanics
JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an
alternative browser
.
Reply to thread
Message
<blockquote data-quote="FrumiousBandersnatch" data-source="post: 74745701" data-attributes="member: 241055"><p>These aren't theories, they're generally called 'interpretations'; they're ways of describing in physical terms what is described by the mathematics of the quantum formalism. In principle, they should all conform to that formalism. The only evidence for any of them is QM itself.</p><p></p><p>The USP for 'Many Worlds' is that it is the simplest interpretation, i.e. it adds nothing to the quantum formalism, whereas the other mainstream interpretations introduce unexplained ad-hoc extras. For example, the Copenhagen variations introduce the idea of wavefunction collapse, an instantaneous change of state of the wavefunction, which doesn't appear at all in the formalism. All that's needed for MW is to accept the wavefunction as a complete description of the state of things in the world, which it appears to be, and follow its unitary evolution according to the Schrodinger equation.</p><p></p><p>The QM formalism describes how quantum systems in superposition interact - they become 'entangled' - their states combine additively so that their wavefunctions (actually parts of the universal wavefunction) must be considered together, i.e. they become a single quantum system. So, for example, particle A in a superposition of spin-up and spin-down, might interact and become entangled with particle B, so that the resulting system is described by a combination of [spin-up A with B] and [spin-down A with B] (in <a href="https://en.wikipedia.org/wiki/Bra%E2%80%93ket_notation" target="_blank">bra–ket notation</a>, something like this: ⎥A↑〉⎥B〉 + ⎥A↓〉⎥B〉. These <strong>⎥</strong>X<strong>〉</strong> states represent the vectors in Hilbert space).</p><p></p><p>This should be the same for all interpretations, but it's how this situation then develops that shows the differences. In MW, this process simply continues deterministically, with more and more particles joining the entanglement until the superposed states rapidly become so entangled with the environment they can no longer interfere with each other, becoming separate non-interacting branches of the wavefunction that continue to develop independently, i.e. effectively separate 'worlds'. This process is called decoherence. In Copenhagen interpretations, when systems large enough to be described classically (a rather fuzzy boundary), e.g. a person or a measuring device, interact with a quantum system in superposition, the wavefunction instantaneously 'collapses' so that all but one of the superposed states (randomly) cease to exist.</p><p></p><p>So Copenhagen accounts for our macro-scale observation of a single outcome for a quantum measurement by somehow throwing away all but one state of the superposition, whereas Many Worlds says the observer simply joins the superposition like any other quantum system, branching with it and participating in each of the non-interacting branches that result.</p><p></p><p>For its supporters, the simplicity of MW makes it preferable to wavefunction collapse interpretations and the tricky additional questions that accompany them.</p><p></p><p>Whether we can ever determine which interpretation (if any) reflects what 'really' happens is a moot point, but MW would be falsified if wavefunction collapse could be demonstrated or shown to be necessary...</p></blockquote><p></p>
[QUOTE="FrumiousBandersnatch, post: 74745701, member: 241055"] These aren't theories, they're generally called 'interpretations'; they're ways of describing in physical terms what is described by the mathematics of the quantum formalism. In principle, they should all conform to that formalism. The only evidence for any of them is QM itself. The USP for 'Many Worlds' is that it is the simplest interpretation, i.e. it adds nothing to the quantum formalism, whereas the other mainstream interpretations introduce unexplained ad-hoc extras. For example, the Copenhagen variations introduce the idea of wavefunction collapse, an instantaneous change of state of the wavefunction, which doesn't appear at all in the formalism. All that's needed for MW is to accept the wavefunction as a complete description of the state of things in the world, which it appears to be, and follow its unitary evolution according to the Schrodinger equation. The QM formalism describes how quantum systems in superposition interact - they become 'entangled' - their states combine additively so that their wavefunctions (actually parts of the universal wavefunction) must be considered together, i.e. they become a single quantum system. So, for example, particle A in a superposition of spin-up and spin-down, might interact and become entangled with particle B, so that the resulting system is described by a combination of [spin-up A with B] and [spin-down A with B] (in [URL='https://en.wikipedia.org/wiki/Bra%E2%80%93ket_notation']bra–ket notation[/URL], something like this: ⎥A↑〉⎥B〉 + ⎥A↓〉⎥B〉. These [B]⎥[/B]X[B]〉[/B] states represent the vectors in Hilbert space). This should be the same for all interpretations, but it's how this situation then develops that shows the differences. In MW, this process simply continues deterministically, with more and more particles joining the entanglement until the superposed states rapidly become so entangled with the environment they can no longer interfere with each other, becoming separate non-interacting branches of the wavefunction that continue to develop independently, i.e. effectively separate 'worlds'. This process is called decoherence. In Copenhagen interpretations, when systems large enough to be described classically (a rather fuzzy boundary), e.g. a person or a measuring device, interact with a quantum system in superposition, the wavefunction instantaneously 'collapses' so that all but one of the superposed states (randomly) cease to exist. So Copenhagen accounts for our macro-scale observation of a single outcome for a quantum measurement by somehow throwing away all but one state of the superposition, whereas Many Worlds says the observer simply joins the superposition like any other quantum system, branching with it and participating in each of the non-interacting branches that result. For its supporters, the simplicity of MW makes it preferable to wavefunction collapse interpretations and the tricky additional questions that accompany them. Whether we can ever determine which interpretation (if any) reflects what 'really' happens is a moot point, but MW would be falsified if wavefunction collapse could be demonstrated or shown to be necessary... [/QUOTE]
Insert quotes…
Verification
Post reply
Forums
Discussion and Debate
Discussion and Debate
Physical & Life Sciences
Non-Mainstream and Controversial Science
Parallel universe theory in quantum mechanics
Top
Bottom