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From: Luyang Han on 21 Jun 2010 16:25
Hello,

One question comes into my mind. Is there any fundamental interaction which
shows a hysteresis or a memory effect?

If we consider the framework of Newton, the evolution of the system just
depends on the interaction and its state at a certain time, but does not
depends on how the system reached this state.

Lots of macroscopic phenomena show memory effect. But the memory is only due
to the reason that the microscopic description is ignored and a statistical
macroscopic view is taken. Consider the typical example of a magnet. The
response of the magnet to the external field depends on its history. But
here just the magnetization of the material is considered. If we know the
microscopic configuration of the magnetic moment, the behavior of the magnet
can be predicted without knowing its history.

So the question is, is there any fundamental interaction, whose influence to
the system evolution depends on the history of its interaction?

Is this problem related to the concept of arrow of time in physics?

Han
From: jon on 22 Jun 2010 17:34

"Luyang Han" <luyang.han(a)gmail.com> wrote in message
news:4c1fcb21(a)news.uni-ulm.de...
> Hello,
>
> One question comes into my mind. Is there any fundamental interaction
> which
> shows a hysteresis or a memory effect?

yes, magnetics.



> Is this problem related to the concept of arrow of time in physics?

no.

>
> Han


From: Luyang Han on 23 Jun 2010 03:47
jon wrote:

>> One question comes into my mind. Is there any fundamental interaction
>> which
>> shows a hysteresis or a memory effect?
>
> yes, magnetics.
>

No. Magnetic hysteresis is not a fundamental hysteresis or memory effect. I
have already explained that in the original post. The apparent macroscopic
hysteresis effect is due to the lack of complete information on microscopic
scale. The microscopic description, which can be modeled by Landau–Lifshitz–
Gilbert equation. If one knows the magnetic moment configuration, the
magnetic behavior can be predicted without knowing its history.
From: mordent on 24 Jun 2010 13:47

"Luyang Han" <luyang.han(a)gmail.com> wrote in message
news:4c21bc59$1(a)news.uni-ulm.de...
> jon wrote:
>
>>> One question comes into my mind. Is there any fundamental interaction
>>> which
>>> shows a hysteresis or a memory effect?
>>
>> yes, magnetics.
>>
>
> No. Magnetic hysteresis is not a fundamental hysteresis or memory effect.
> I
> have already explained that in the original post. The apparent macroscopic
> hysteresis effect is due to the lack of complete information on
> microscopic
> scale. The microscopic description, which can be modeled by
> Landau-Lifshitz-
> Gilbert equation. If one knows the magnetic moment configuration, the
> magnetic behavior can be predicted without knowing its history.

Wrong.
The first computer memory was Magnetic core memory.
http://en.wikipedia.org/wiki/Magnetic_core_memory
One cannot predict magnetic behavior without knowing its history.

A good learning lesson for you.


From: Edward Green on 24 Jun 2010 14:35
On Jun 21, 4:25 pm, Luyang Han <luyang....(a)gmail.com> wrote:
> Hello,
>
> One question comes into my mind. Is there any fundamental interaction which
> shows a hysteresis or a memory effect?
>
> If we consider the framework of Newton, the evolution of the system just
> depends on the interaction and its state at a certain time, but does not
> depends on how the system reached this state.
>
> Lots of macroscopic phenomena show memory effect. But the memory is only due
> to the reason that the microscopic description is ignored and a statistical
> macroscopic view is taken. Consider the typical example of a magnet. The
> response of the magnet to the external field depends on its history. But
> here just the magnetization of the material is considered. If we know the
> microscopic configuration of the magnetic moment, the behavior of the magnet
> can be predicted without knowing its history.
>
> So the question is, is there any fundamental interaction, whose influence to
> the system evolution depends on the history of its interaction?

That's pretty much ruled out by semantics: if the system has a
"memory", then the memory is part of the current state of the system.
A better question is, what kinds of "states" do we have in mind when a
system is said to display memory?

> Is this problem related to the concept of arrow of time in physics?

You mean that no system has a memory effect associated with its
future? Yes, there would seem to be some relation there. So? :-)


> Han

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