On Friday, November 30, 2018 at 8:53:43 AM UTC, Bruno Marchal wrote:
>
>
> On 27 Nov 2018, at 22:55, agrays...@gmail.com <javascript:> wrote:
>
>
>
> On Tuesday, November 27, 2018 at 8:43:55 PM UTC, Philip Thrift wrote:
>>
>>
>>
>> On Tuesday, November 27, 2018 at 2:05:04 PM UTC-6, agrays...@gmail.com 
>> wrote:
>>>
>>>
>>>
>>> On Tuesday, November 27, 2018 at 6:49:51 PM UTC, Philip Thrift wrote:
>>>>
>>>>
>>>>
>>>> On Tuesday, November 27, 2018 at 12:17:08 PM UTC-6, agrays...@gmail.com 
>>>> wrote:
>>>>>
>>>>>
>>>>>
>>>>> On Tuesday, November 27, 2018 at 6:00:50 PM UTC, Philip Thrift wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>> On Tuesday, November 27, 2018 at 8:43:35 AM UTC-6, 
>>>>>> agrays...@gmail.com wrote:
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On Tuesday, November 27, 2018 at 9:27:46 AM UTC, Philip Thrift wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> On Monday, November 26, 2018 at 3:43:14 PM UTC-6, 
>>>>>>>> agrays...@gmail.com wrote:
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> *I checked the postulates in Feynman's Sums Over Histories (in 
>>>>>>>>> link provided by Phil) and I see nothing related to waves, as 
>>>>>>>>> expected, and 
>>>>>>>>> thus nothing about collapse of anything. I would suppose the same 
>>>>>>>>> applies 
>>>>>>>>> to Heisenberg's Matrix Mechanics; no waves, no collapse. I suppose 
>>>>>>>>> you 
>>>>>>>>> could say they just produce correct probabilities, and imply nothing 
>>>>>>>>> about 
>>>>>>>>> relative states other than their probabilities (which wave mechanics 
>>>>>>>>> does), 
>>>>>>>>> but certainly nothing about consciousness. To summarize: you're right 
>>>>>>>>> that 
>>>>>>>>> they are "no collapse" theories, but IMO they say nothing about 
>>>>>>>>> consciousness. AG*
>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> In terms of the path-integral (PI) interpretation [ interesting 
>>>>>>>> lecture: 
>>>>>>>> https://www.perimeterinstitute.ca/videos/path-integral-interpretation-quantum-mechanics
>>>>>>>>  
>>>>>>>> ], there is in effect no waves or wave function, just paths, or 
>>>>>>>> histories, 
>>>>>>>> in the sum-over-histories (SOH) terminology.
>>>>>>>>
>>>>>>>> There is still "decoherence" in the SOH (a single history is 
>>>>>>>> ultimately "realized"), but it could be called "selection": a single 
>>>>>>>> history is selected from the total ensemble of multiple and 
>>>>>>>> interfering 
>>>>>>>> histories. E.g. a single point on a screen is "hit" by a photon in the 
>>>>>>>> double-slit experiment.
>>>>>>>>
>>>>>>>
>>>>>>> *Does "selection" add any insight to the measurement problem; that 
>>>>>>> is, why do we get what we get? And if not, what is its value? TIA, AG *
>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>> If you look at it as a "selection of the fittest" (one history 
>>>>>> surviving from an ensemble of histories), then it's like a form of 
>>>>>> quantum 
>>>>>> Darwinism. The quantum substrate is a cruel world where all histories 
>>>>>> (but 
>>>>>> one) die.
>>>>>>
>>>>>
>>>>> That's not an explanation; rather, a vacuous statement of the result. 
>>>>> AG 
>>>>>
>>>>>>
>>>>>>
>>>> But that is a criticism of Darwinism (*natural selection*) in general.
>>>>
>>>
>>> *Ridiculous comparison IMO. Darwinism posits a changing environment and 
>>> competition among species for niches. Nothing comparable in Quantum 
>>> Darwinism other than all outcomes fail except for one which succeeds in 
>>> each single trial, which we knew from the get-go. AG*
>>>
>>>>
>>>> *Quantum Darwinism* is a theory claiming to explain the emergence of 
>>>> the classical world <https://en.wikipedia.org/wiki/Classical_physics>from 
>>>> the quantum world <https://en.wikipedia.org/wiki/Quantum_mechanics> as 
>>>> due to *a process of **Darwinian 
>>>> <https://en.wikipedia.org/wiki/Charles_Darwin> natural selection 
>>>> <https://en.wikipedia.org/wiki/Natural_selection>*; where the many 
>>>> possible quantum states <https://en.wikipedia.org/wiki/Quantum_states> are 
>>>> selected against in favor of a stable pointer state 
>>>> <https://en.wikipedia.org/wiki/Pointer_state>.
>>>> [ https://en.wikipedia.org/wiki/Quantum_Darwinism ]
>>>>
>>>> - pt
>>>>  
>>>>
>>>
>>
>>
>> As for "competition for niches", the histories are in a sense competing. 
>> Perhaps there is some conservation principle at work, so only one history 
>> can win. 
>>
>> I don't know. Physicists don't know. We're even. :)
>>
>
> *Darwin had a theory or proposal to explain why some changes occur and 
> persist, but Quantum Darwinism doesn't, as far as I can tell. AG *
>
>
> I think that the comparison with Darwin makes sense, and in both case, 
> there are many “fittest” entities.
>


*IMO, it's a ridiculous comparison. If you affirm the MWI, then ALL 
histories survive. If you deny the MWI, there's no model whatever of 
"fittest" to explain why all histories cease to exist except the one 
measured for a single trial. The only thing remarkable here is that I have 
to explain this. AG *

Evolution gives a tree, with many branches, and "quantum Darwinism” gives 
> rise too too many locally consistent histories. None select one individual 
> branche, ISTM.
>
> Bruno
>
>
>
>
>> - pt
>>
>
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