Quantum Mechanics

[james blunt]

 

[shunyadragon]

No, field density.

Probably both.

 

[james blunt]

Probably both.

Well yea, I was just adding a point. Don't want to spoil the thread , it is good reading material.

 

[sealchan]

Yes I thought it was quite neat. I see Polymath is saying that while gamma emission may be induced in a similar way to what I have been describing, alpha decay is another kind of randomness, due to the probability of the alpha particle tunnelling out of the potential well that keeps it inside the nucleus.

Both processes are thus attributable to purely QM concepts and are intrinsically random, i.e. each individual event is "uncaused", although as you rightly point out we do have a "cause" in terms of the QM mechanism behind the process.

This is all rather good stuff, I must say.

What's interesting about randomness is that on the classical level it too is a form of order but not with respect to the system of concern. For many adaptive systems they have developed in the context of their immersion in disorderly systems such that prediction is not required for their successful interaction. You can't define a system that is perfectly random only identify or even create systems that seem random.

Now on the quantum level there appears to be a kind of background in which "throwing dice" is the order itself. Our mathematics of statistics is obeyed rather than an underlying mechanism suggested...or perhaps there is this neat separation at the level of the quantum background fluctuation that is a neatly defined limit to our ability to see beyond that limit.

Quantum mechanics suggests a kind of digital realm operating in a kind of analog background...and there are so many other polarities and balances which all seem to play the role of making the walls that is our cage/Universe without giving us any hope of penetrating that wall.

But even if If we can find a pattern in the noise that gives us a peak into the order behind the randomness (of those phenomenon which "reflect" the quantum vacuum fluctuation) chaos theory hints that only an inaccessibly precise knowledge of initial conditions would allow us the ability to make practical use of such knowledge.

Our cage that is the Universe begins to seem to be constructed of the very concepts we use to understand it. In an endlessly circular way it seems our very minds have grown out of the structure of the universe and that universes character is our own character. Alternately our scientific concepts rooted in the reality at our scale seem to be dissolving as we look at our reality beyond our scale (in either direction) as if the knit of our minds is tied up in our "objective" understanding.

Are we prisoners in our own Matrix and is there a way out through some hole that we refuse to see because our very sense of truth itself shields us from it?

 

[shunyadragon]

What's interesting about randomness is that on the classical level it too is a form of order but not with respect to the system of concern. For many adaptive systems they have developed in the context of their immersion in disorderly systems such that prediction is not required for their successful interaction. You can't define a system that is perfectly random only identify or even create systems that seem random.

It is more descriptive and accurate to describe the outcomes of cause and effect events as fractal according to chaos theory, and not use random nor appearance of randomness, becuse it is misleading.

Now on the quantum level there appears to be a kind of background in which "throwing dice" is the order itself.

First of all at the Quantum level "throwing dice" is NOT the order itself. Odd statement.

 

[Al Ibn Al Amra]

You arrive here to be treat .

 

[sayak83]

I didn't exactly skip over classical theory, but I did QM early enough that the classical intuitions hadn't gelled yet. Similarly for relativity. So there are a lot of aspects of the quantum world that don't seem to strange to me but seem strange to others.

On the other hand, the way angular momentum works is often pretty strange.

I think that the classical intuition is that there exists objects with intrinsic properties that interact during the course of their existence to create events that can be observed and studied. So it is an object centered view of the world. When I learnt QM, I began to believe that it is better to think of events as central. There exists a web of events out of which various observable properties and actions coagulate to give us object-like stuff of various stabilities (from evanescent virtual particles to electrons) and probabilities. The Feyman event-diagrams seems to suggest that such a route may be more "natural" to nature. So, as if instead of "I am walking on the road" ...we have " there is a walking event out of which the road and I come to be in a relational existence."

Speculative...but what do you think?

 

[sayak83]

I also ponder the situations where a single type of particle, say a tau particle has several different decay modes, each with a different half-life. So, two tau particles that are otherwise the same in all characteristics might have one decay into a muon and associated neutrinos or a pion with associated neutrinos. In fact, there are several dozen different decay modes for a tau particle. In what sense are the decay products 'caused' by the initial tau particle?

My difficulties are as much in how to define the terms 'cause' and 'effect' as anything else. OK, we set up initial conditions and call them the 'cause' and see what happens and call that the 'effect'. So, is causality simply one event (or collection of events) happening before a different event (or collection of events)?

Is being able to predict probabilities enough to say there is causality?



I interpret the macroscopic causality as being an averaging process over the probabilities from the lower levels. A trivial example is to imagine a coin. Flip it one time and you have a 50/50 chance of a head or a tail, with little predictability (well...this is a classical system, so...). But, if you flip a trillion coins, the number of heads will be very close to 50%. Yes, there is a spread, but as a percentage that spread is small.

If you have Avagadro's number of coins to flip, that 50% is accurate to within our ability to measure. And for macroscopic measurements, we are always dealing with an average over many, many quantum particles. So the predictability is very high. And that is why classical causality works for macroscopic objects.

yes, good contribution!

In special relativity, the time-like part of the light cone contains the set of events that are in the absolute past of the event being observed and all things influencing the progress of the current event must reside within this past lightcone. If, among this set, a few past events have outsize influence in how the current event is expected to proceed (probabilistically, taking QM into account)...can these past events be called the causes of the current one?

 

[exchemist]

In special relativity, the time-like part of the light cone contains the set of events that are in the absolute past of the event being observed and all things influencing the progress of the current event must reside within this past lightcone. If, among this set, a few past events have outsize influence in how the current event is expected to proceed (probabilistically, taking QM into account)...can these past events be called the causes of the current one?

Well I would say yes, such events are contributory causes. I see nothing wrong with the term contributory cause. It has a well understood common usage that seems clear enough to me. But the strict one-to-one between cause and effect is not present of course.

I notice that the Wiki definition of "causality" is expressed in terms of partial causes, not just one-to-one cause and effect: Causality - Wikipedia

 

[shunyadragon]

Well I would say yes, such events are contributory causes. I see nothing wrong with the term contributory cause. It has a well understood common usage that seems clear enough to me. But the strict one-to-one between cause and effect is not present of course.

I notice that the Wiki definition of "causality" is expressed in terms of partial causes, not just one-to-one cause and effect: Causality - Wikipedia

In Quantum Mechanics I believe that that the cause is dominated by the underlying Natural Laws, and not the chain of cause and effect outcomes that we see in the macro world.

 

[Polymath257]

I think that the classical intuition is that there exists objects with intrinsic properties that interact during the course of their existence to create events that can be observed and studied. So it is an object centered view of the world. When I learnt QM, I began to believe that it is better to think of events as central. There exists a web of events out of which various observable properties and actions coagulate to give us object-like stuff of various stabilities (from evanescent virtual particles to electrons) and probabilities. The Feyman event-diagrams seems to suggest that such a route may be more "natural" to nature. So, as if instead of "I am walking on the road" ...we have " there is a walking event out of which the road and I come to be in a relational existence."

Speculative...but what do you think?

Yes, this is actually fairly close to what happens in the math. All modern Quantum Field Theories are based on Lagrangians which, essentially describe the strength of interaction of the different fields. So, charge is related to the strength of interaction with photons (hence, the E&M force), mass the stength of interaction with gravitons (hence, gravity), etc.

One curious aspect, though, is that each Feynman diagram represents a term in the calculation of the total interaction. Different Feynman diagrams can 'interfere' with each other.

 

[james blunt]

Yes, this is actually fairly close to what happens in the math. All modern Quantum Field Theories are based on Lagrangians which, essentially describe the strength of interaction of the different fields. So, charge is related to the strength of interaction with photons (hence, the E&M force), mass the stength of interaction with gravitons (hence, gravity), etc.

One curious aspect, though, is that each Feynman diagram represents a term in the calculation of the total interaction. Different Feynman diagrams can 'interfere' with each other.

Oh dear, it is worse than I thought and I now feel the need to step in and correct you all.
Let me start with mass, a 1kg object is only really 0.5kg. Secondly there is no such thing as gravitons.
Gravity is 0 is attracted to 0 through a medium of 0 . Yes you will not understand that right away.

 

[Polymath257]

Well I would say yes, such events are contributory causes. I see nothing wrong with the term contributory cause. It has a well understood common usage that seems clear enough to me. But the strict one-to-one between cause and effect is not present of course.

I notice that the Wiki definition of "causality" is expressed in terms of partial causes, not just one-to-one cause and effect: Causality - Wikipedia

One aspect of classical notions of causality that has to be given up is contiguity. So, if the formation of an unstable nucleus is the 'cause' of its decay, the cause and the effect may well be separated by billions of years with no other causal factor between. The more classical notion would require a *chain* of events, each in causal relation, between the formation and the decay.

And, as @sayak83 pointed out, anything in the past light cone could potentially be a 'cause'.

So, if we focus on an unstable nucleus, what, if anything, do we want to say the cause is of the decay? Do we want to say it is having an extra neutron? That would, again, take us back to the formation of the nucleus. Also, there is no way to say *which* neutron is the 'cause' of the instability. ALL of them are, in a sense.....

 

[james blunt]

M0 = A + B

M1=M0 + M0'

 

[Polymath257]

In Quantum Mechanics I believe that that the cause is dominated by the underlying Natural Laws, and not the chain of cause and effect outcomes that we see in the macro world.

Could you elaborate a bit?

 

[shunyadragon]

Could you elaborate a bit?

I do not agree with the 'anything' in the below citation.

And, as @sayak83 pointed out, anything in the past light cone could potentially be a 'cause'.

I believe the 'anything' is Natural Law.

 

[Polymath257]

I do not agree with the 'anything' in the below citation.



I believe the 'anything' is Natural Law.

OK, so if I'm reading you right, it is the natural laws that are causes, not events or objects?

 

[exchemist]

One aspect of classical notions of causality that has to be given up is contiguity. So, if the formation of an unstable nucleus is the 'cause' of its decay, the cause and the effect may well be separated by billions of years with no other causal factor between. The more classical notion would require a *chain* of events, each in causal relation, between the formation and the decay.

And, as @sayak83 pointed out, anything in the past light cone could potentially be a 'cause'.

So, if we focus on an unstable nucleus, what, if anything, do we want to say the cause is of the decay? Do we want to say it is having an extra neutron? That would, again, take us back to the formation of the nucleus. Also, there is no way to say *which* neutron is the 'cause' of the instability. ALL of them are, in a sense.....

The slight problem I have with the "event" - or interaction? - view of this is that you have succeeded in convincing me there are some processes that are uncaused, the decay of a given atom of a radioisotope being one of them. While we have a cause for the instability of a radioactive nucleus, i.e. for the tendency to decay, the individual decays are random, which implies or suggests the events are individually uncaused.

This it seems to me is a different case from that of stimulated emission, in which a passing photon acts as a trigger for emission, but only with a certain probability. That is a direct cause but one that only sometimes produces an effect.

 

[Bob the Unbeliever]

I think that the classical intuition is that there exists objects with intrinsic properties that interact during the course of their existence to create events that can be observed and studied. So it is an object centered view of the world. When I learnt QM, I began to believe that it is better to think of events as central. There exists a web of events out of which various observable properties and actions coagulate to give us object-like stuff of various stabilities (from evanescent virtual particles to electrons) and probabilities. The Feyman event-diagrams seems to suggest that such a route may be more "natural" to nature. So, as if instead of "I am walking on the road" ...we have " there is a walking event out of which the road and I come to be in a relational existence."

Speculative...but what do you think?

That's quite interesting. And it also seems to fit within string theory (which hasn't been proven, but has many attractive features).

 

[Polymath257]

The slight problem I have with the "event" - or interaction? - view of this is that you have succeeded in convincing me there are some processes that are uncaused, the decay of a given atom of a radioisotope being one of them. While we have a cause for the instability of a radioactive nucleus, i.e. for the tendency to decay, the individual decays are random, which implies or suggests the events are individually uncaused.

This it seems to me is a different case from that of stimulated emission, in which a passing photon acts as a trigger for emission, but only with a certain probability. That is a direct cause but one that only sometimes produces an effect.

I think I agree. There is at least *some* aspect of causality when the probabilities are affected. One interesting point here is that events may be 'partially caused' and not 'fully caused'. We can have 'contributory causes', perhaps several of them, no collection of which are *sufficient* for the event to occur.

This is, yet again, a distinct difference from classical causality where the collection of all contributory causes *is* sufficient for the event to occur. The case of events with no cause is an extreme case of this difference.