Wave function collapse in the macro world

[runninglama1130]

Do material objects and beings in the macro world exist in a state of probability and only come into existence when observed?

[exchemist]

Just now, runninglama1130 said:

Do material objects and beings in the macro world exist in a state of probability and only come into existence when observed?

No. And nor do QM entities either, at least in the most prevalent interpretations. The so-called wave function collapse is due to interaction, not necessarily "observation" by a conscious "observer".  Observation requires interaction with a detector, but interactions with things other than detectors, i.e. that don't result in observation, have the same effect. According to my understanding at least.   

[studiot]

5 minutes ago, runninglama1130 said:

Do material objects and beings in the macro world exist in a state of probability and only come into existence when observed?

Observation means any interaction whatsoever with the environment/surroundings.

So just how difficult is it for a macro object not to interact with its surroundings ?

[runninglama1130]

Umm, good point.

[geordief]

What happens  when the waveform "collapses"?

Is a new waveform created?

What ,then is the relationship  of the new waveform to the old?

There is no throwing of the dice in this process ,is there?

 

[MigL]

5 hours ago, studiot said:

So just how difficult is it for a macro object not to interact with its surroundings ?

As it is impossible to entangle six hunderd billion trillion molecules ( in one mole ) with the same wavefunction, self interaction must also be considered in the collapse, not just the surroundings.

Edited July 31, 2022 by MigL

[studiot]

10 hours ago, geordief said:

What happens  when the waveform "collapses"?

Is a new waveform created?

What ,then is the relationship  of the new waveform to the old?

There is no throwing of the dice in this process ,is there?

 

No collapse is really a poor term.

What happens is that the interaction selects a particular solution from all the possible ones in the superposition.

This is just like you choosing which square root you want when you select -2 (or +2) and use it as the square root of 4.

MigL also make a good point +1

7 hours ago, MigL said:

As it is impossible to entangle six hunderd billion trillion molecules ( in one mole ) with the same wavefunction, self interaction must also be considered in the collapse, not just the surroundings.

That there with a complicated macro system there may be (probably will be) many small self interactions between parts of the 'collapsing' system.
Rather as some parts of a large structure fail before others when it collapses structurally.

I don't know if there is any quantum situation similar to the transition from elastic failure to plastic failure which works like this. That would be an intersting speculation to pursue.

Edited July 31, 2022 by studiot

[exchemist]

20 minutes ago, studiot said:

No collapse is really a poor term.

What happens is that the interaction selects a particular solution from all the possible ones in the superposition.

This is just like you choosing which square root you want when you select -2 (or +2) and use it as the square root of 4.

MigL also make a good point +1

That there with a complicated macro system there may be (probably will be) many small self interactions between parts of the 'collapsing' system.
Rather as some parts of a large structure fail before others when it collapses structurally.

I don't know if there is any quantum situation similar to the transition from elastic failure to plastic failure which works like this. That would be an intersting speculation to pursue.

Is that entirely right? Surely even a single solution to Schrödinger's equation is still a "monochromatic" wave function, describing in effect a probability density over space, rather than a specific location at which the QM entity might be detected. In which case, "collapse" represents detection (or interaction) at a specific location, with a likelihood  predicted  statistically by the (single) solution (wave function).

[studiot]

2 minutes ago, exchemist said:

Is that entirely right? Surely even a single solution to Schrödinger's equation is still a "monochromatic" wave function, describing in effect a probability density over space, rather than a specific location at which the QM entity might be detected. In which case, "collapse" represents detection (or interaction) at a specific location, with a likelihood  predicted  statistically by the (single) solution (wave function).

Yes perhaps it was an oversimplified picture. +1

[geordief]

I am still wondering   how one calculates the new waveform 'or rather what is the relationship  between the "ingoing" waveform and the"post interaction" waveform?

Is it again a probabilistic  relationship? Is there any relationship  as such?

[exchemist]

3 hours ago, geordief said:

I am still wondering   how one calculates the new waveform 'or rather what is the relationship  between the "ingoing" waveform and the"post interaction" waveform?

Is it again a probabilistic  relationship? Is there any relationship  as such?

As a chemist, I am conscious that a real physicist my pop up and shoot me down, but I think you have to start again with the system as it is after the interaction. Energies, potentials, momenta etc may have changed, so you have a new state, with a new Hamiltonian (a mathematical description of the total i.e. potential plus kinetic, energy of the system) in the Schrödinger equation. In many cases you can work out what this will be from the nature of the interaction, e.g. absorption of a photon by an electron in an atom. But you generally would need to solve the equation again, I think (except I suppose in very simple cases, like an elastic collision or something, where you may get away with just changing the phase.) The relationship between the two wave functions itself won't be probabilistic, since each is a defined  mathematical expression. But each expression is a probability-based description of the system.  

 

Edited July 31, 2022 by exchemist