On Friday, April 27, 2018 at 4:24:44 AM UTC, agrays...@gmail.com wrote:
>
>
>
> On Friday, April 27, 2018 at 1:43:30 AM UTC, Brent wrote:
>>
>>
>>
>> On 4/26/2018 6:21 PM, agrays...@gmail.com wrote:
>>
>>
>>
>> On Friday, April 27, 2018 at 1:10:25 AM UTC, Brent wrote: 
>>>
>>>
>>>
>>> On 4/26/2018 4:14 PM, agrays...@gmail.com wrote:
>>>
>>>
>>>
>>> On Thursday, April 26, 2018 at 10:25:29 PM UTC, Brent wrote: 
>>>>
>>>>
>>>>
>>>> On 4/26/2018 2:33 PM, agrays...@gmail.com wrote:
>>>>
>>>>
>>>>
>>>> On Thursday, April 26, 2018 at 9:09:48 PM UTC, Brent wrote: 
>>>>>
>>>>>
>>>>>
>>>>> On 4/26/2018 7:23 AM, agrays...@gmail.com wrote:
>>>>>
>>>>>
>>>>>
>>>>> On Thursday, April 26, 2018 at 4:12:41 AM UTC, Brent wrote: 
>>>>>>
>>>>>>
>>>>>>
>>>>>> On 4/25/2018 7:44 PM, agrays...@gmail.com wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>> On Thursday, April 26, 2018 at 2:17:31 AM UTC, Brent wrote: 
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On 4/25/2018 6:39 PM, agrays...@gmail.com wrote:
>>>>>>>
>>>>>>>
>>>>>>> *On its face it's absurd to think the SoL is invariant for all 
>>>>>>> observers regardless of the relative motion of source and recipient, 
>>>>>>> but it 
>>>>>>> has testable consequences. The MWI has no testable consequences, so it 
>>>>>>> makes no sense to omit this key difference in your historical 
>>>>>>> comparisons 
>>>>>>> with other apparent absurdities in physics. Moreover when you factor 
>>>>>>> into 
>>>>>>> consideration that non locality persists in the many worlds postulated 
>>>>>>> -- 
>>>>>>> assuming you accept Bruce's analysis -- what exactly has been gained by 
>>>>>>> asserting the MWI? Nothing as far as I can tell. And the loss is 
>>>>>>> significant as any false path would be. AG*
>>>>>>>
>>>>>>>
>>>>>>> It's one possible answer to the question of where the Heisenberg cut 
>>>>>>> is located (the other is QBism).  It led to the theory of decoherence 
>>>>>>> and 
>>>>>>> Zurek's theory of quantum Darwinism which may explain Born's rule.
>>>>>>>
>>>>>>> Brent
>>>>>>>
>>>>>>
>>>>>> * I've always found the Heisenberg Cut to be a nebulous concept, a 
>>>>>> kind of hypothetical demarcation between the quantum and classical 
>>>>>> worlds. *
>>>>>>
>>>>>>
>>>>>> That's the problem with it; it doesn't have an objective physical 
>>>>>> definition.  Bohr regarded it as a choice in analyzing an experiment; 
>>>>>> you 
>>>>>> put it where ever was convenient.
>>>>>>
>>>>>> *What kind of boundary are we talking about, and how could the MWI 
>>>>>> shed any light on it, whatever it is? AG *
>>>>>>
>>>>>>
>>>>>> In MWI there is no Heisenberg cut; instead there's a splitting of 
>>>>>> worlds which has some objective location in terms of decoherence.
>>>>>>
>>>>>> Brent
>>>>>>
>>>>>
>>>>> The Heisenberg Cut is too vague and ill-defined to shed light on 
>>>>> anything, and to say the MWI is helpful is adding another layer of 
>>>>> confusion. AG
>>>>>
>>>>>
>>>>> Decoherence is a specific well-defined physical process and it 
>>>>> describes the splitting of worlds.  There is still some question whether 
>>>>> it 
>>>>> entails the Born rule, but at worst the Born rule remains as a separate 
>>>>> axiom.
>>>>>
>>>>> Brent
>>>>>
>>>>
>>>> Let's say an electron goes through an SG device. IIUC, its spin state 
>>>> becomes entangled with the spin wf's of the device. How do you infer 
>>>> splitting of worlds from this? AG
>>>>
>>>>
>>>> I don't.  Why should I?
>>>>
>>>> Brent
>>>>
>>>
>>> I could swear that you wrote above that decoherence describes the 
>>> splitting of worlds, so I gave you an example of decoherence 
>>>
>>>
>>> You didn't give an example of decoherence.  Where's the decoherence in 
>>> an electron flying through a divergent magnetic field?
>>>
>>> Brent
>>>
>>
>> That's what I figured you would write and maybe you're correct. I thought 
>> decoherence means that the wf of the system being measured, gets entangled 
>> with the wf's of the environment, in this case the SG device. Why is this 
>> not decoherence, and if it isn't, what is?  TIA, AG
>>
>>
>> Decoherence happens when the particle is detected in one path or the 
>> other, not when going thru the SG.  It's a classic experiment to show that 
>> particle wf can be coherently recombined after going through SGs.  So if 
>> you set up a detector on one leg of the SG then the world splits when there 
>> is a detection vs no detection.
>>
>> Brent
>>
>
> I am not considering a singlet state; just an electron passing through a 
> SG device and being measured, spin up or down. Are you saying no 
> decoherence in this case? From what I gather from descriptions of 
> decoherence, it occurs when a measurement occurs, and the particle's wf 
> gets entangled with the measurement device. This is a detection, and I 
> think you're saying the world splits. If so, why would it? If there's no 
> detection for whatever reason, what are we to conclude? I would guess, 
> nothing. AG
>

Maybe you thought I meant an electron flying through an SG device and NOT 
be measured. No, I meant a measurement of Up or Down, and I think whenever 
we have a measurement, there is decoherence. But why this leads to a 
splitting of worlds is above my pay grade. AG 

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