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与敖平继续讨论统计物理问题【3】

已有 3889 次阅读 2012-3-13 21:51 |个人分类:杂谈评论|系统分类:科研笔记| 统计, 物理, Technical, potential, situation

与敖平继续讨论统计物理问题【3】
 
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Dear Prof. Bi and Fang:

In response to the inquiry for our construction of potential function in generic situations, here I list our key technical work here, which I didn't in my prevous message.
The pdf of 2) is attached here, which deals with a situation most people in nonequilibrium thought not possible: Existence and construction of potential function in limit cycle dynamics.
The potential function has all the properties in physics.
As far as I know, this was also regarded impossible by Prigogine school (I would be happy to be corrected).

1) On the Existence of Potential Landscape in the Evolution of Complex Systems,
P. Ao, C. Kwon, and H. Qian, Complexity 12 (2007) 19-27.
http://arxiv.org/PS_cache/q-bio/pdf/0703/0703044v1.pdf

2) Limit Cycle and Conserved Dynamics,
X.-M. Zhu, L. Yin, P. Ao, Int. J. Mod. Phy. B20 (2006) 817I h-827.
http://ejournals.wspc.com.sg/journals/ijmpb/20/2007/S0217979206033607.html

3) Structure of Stochastic Dynamics near Fixed Points,
C. Kwon, P. Ao, and D.J. Thouless,
Proc. Nat’l Acad. Sci. (USA) 102 (2005) 13029-13033.
http://www.pnas.org/content/102/37/13029.full.pdf+html

4) Potential in Stochastic Differential Equations: Novel Construction,
P. Ao, J. Phys. A37 L25-L30 (2004).
http://www.iop.org/EJ/abstract/0305-4470/37/3/L01/

Again, my intension here is not to argue which approach would be better.
Rather, I wish to stimulate the research in China to seize a unique opportunity to make lasting contribution.
My feeling is that, this is also the gaol in your 2010 paper on network science and statistical mechanics.

Look forward to hearing your feedback.

Best,

Ao, Ping


----- 原始邮件 -----
发件人: "ping ao" <az5842@yahoo.com>
收件人: "qiao bi" <biqiao@gmail.com>
抄送: "fang jinqing" <fangjinqing@gmail.com>, aoping@sjtu.edu.cn
发送时间: 星期二, 2012年 3 月 13日 下午 1:33:32
主题: Re: hi, ao ping

Dear Prof. Bi:

Thanks for your interesting questions.
See my response in the context below.

Ao, Ping


From: qiao bi <biqiao@gmail.com>
To: ping ao <az5842@yahoo.com>
Sent: Tuesday, March 13, 2012 11:13 AM
Subject: Re: hi, ao ping


Hi, Prof. A. Ping,

(1) I think the potential function is not only the Hamiltonian in the non-equilibrium situation, question is what is its rigorous math. and phys. meaning?

Yes, it is rigorous math, with all the usual physics meaning. In fact, the latter is its big merit of our approach, comparing with those previous proposals.

Could you give more clear description to it in the non-equilibrium situation?

A good place to get a start on our approach is the paper sent you early:
Emerging of Stochastic Dynamical Equalities and Steady State Thermodynamics from Darwinian Dynamics,
P. Ao, Communications in Theoretical Physics 49 (2008) 1073-1090.
http://ctp.itp.ac.cn/qikan/Epaper/zhaiyao.asp?bsid=2817
Let me know if you have any questions on it.


(2) You said there is a candidate tentatively named Darwinian dynamics for non-equilibrium statistical physics , many thanks for your message and works although in this stage I am not sure about this, but I am interested to study. How about it is related to the negative entropy?

As you may observe from above paper, the connection to the negative entropy ( not a good term in my opinion) should be simple, because both energy and usual entropy are naturally in our framework.

Which kinds of parameters can generally determine the potential function in a non-equilibrium statistical system?

There is NO need for additional parameters.
There are lots of confusions in literature on non-equilibrium statistical system, which we can discuss more later.
In our framework, potential function (or Hamilonian, depending on context) is a necessary concept to describe such systems.

(3) About chaotic map related to the complex spectral decomposition of koopman operator which is not Hamiltonian operator, if there is no the concept of extension Hilbert space, the Feymann approaches could be very difficult, this may be a reason there seems be no one has done these before. So, I am not sure Feymann approach could do it except using some extension tech. of Hilbert space, if that sort of extension happens, that would be exact what I said meaning of "did correct calculation then get the same result", which implying "extension".

Path integral can be, and have been extended, to discrete situations.
It would be an interesting project for students to construct the potential function or Hamilotnian out of dynamical processes described by koopman operator.

(4) But of course I don't think it is completely the same as subdynamics, but they may be the same in some crossing field. If you have great passion to study the both differences during recent time, that is welcome, but I would point out, I don't think the power of the Feymann approaches can be beyond any kind of (famous) projected operators approach such as Ziwanzig projected method, but the subdynamics is for beyond. Therefore for me here there is no big apple even if I can find some differences. I am sorry I said this, which seems too proud, and hope you could not misunderstand I am against you to do this or any no respect to the Feymann approaches, because I only want to point the fact that has been tried and done by the Brussels school in past 30 years. Several hundreds papers have been published, which should be evidences to allow you see the both differences if you have enough time.

As far as I know, subdynamics has not yielded new physics predictions yet. Most work is on mathematics side.
I can be wrong on this, due to my limited knowledge. Will be happy to be corrected.
On the other hand, there are quite a few new predictions from Fyenman type description of subsystems.

No, I am not keen to find the difference, either.
One reason is that, when coming down to real physics problems, subdynamics usually involves approximations at very early stages.

In conclusion, named Darwinian dynamics is more meaningful, I hope having further understanding and discussion with you, a nd hope subdynamics or some new progresses can in principle be tested experimentally from the Darwinian dynamics or evolutions .

There are now new experiments to test some of our predictions. For example, as mentioned to you in previous messages, we predict that a new type stochastic integration is needed.
A recent experiment does show that the usual Ito and Stratonovich types are not valid. Instead, a special case of prediction is valid.


Best Wishes,

Biqiao



On Fri, Mar 9, 2012 at 10:39 PM, ping ao < az5842@yahoo.com > wrote:


Dear Prof. Bi:

Thanks for the good questions.

(1). Potential function in our work is indeed, or play the samilar role as, the Hamiltonian in physics, whether or not in equilibirum or not.

Because we need broader dynamical description, what we have shown is that, even in biological, social and other situations, "Hamiltonian" exists.
Such existence guarantees that statistical mechanics type decription can be used in those fields, as, of course, people have been doing successfully so far, though they have not understood the keys yet.


(2) I do not know your definition, hence I cannot say anthing.
On the other hand, the potential function in our work is both dynamical and statonary quantity, exactly the same situation in usual physical systems.

(3) I agree that Feynman type description has its advantages but I am no interested in defending such approach.
I think it is most interest to see whether or not there are any differences in physics: For a given situation, whether or not two approaches would give different predictions. Or, they would be completely equivalent. From a physicist's pespective, I am not sure of the last point.

For technical mathematical problems, such as you posted, can the Feymann approach solve complex spectral problems for chaotic maps?
while I do not know anyone has done that, I believe the answer is yes, Feynman approach can do that. The reason for such assertation is actually simple: Feynman's path integral is a general mathematical framework.

Again, I am more interested in situations which can in principle be tested experimentally.


Ao, Ping



From: qiao bi < biqiao@gmail.com >
To: ping ao < az5842@yahoo.com >
Sent: Saturday, March 10, 2012 5:21 AM
Subject: Re: hi, ao ping

Hi, Prof. A. Ping,
(1) (1) The potential function is quite interested in the Darwinian dynamics, since it can consist of a formula for the canonical ensemble. I understand this formula is correct even for non-equilibrium states in the Darwinian dynamics. Could you give more clear description to the potential function? I believe it is just Hamiltonian in the equilibrium situation, but what is exact meaning in the non-equilibrium situation?
(2) (2) I firstly guess: the potential function = the potential of information density, which may be related to my recently work (J. Phys. A in submission). But I hope this statement will be explained after I truly understand the potential function.
(3) (3) Feymann types of approaches have advantages, especially to the quantum field system, but I believe that if we did correct calculations the subdynamics and the Feymann methods will give the same results. However, I said the correct calculation is not that kind easier, since it needs researchers to have enough skills to handle both sides. Many cases, because implied not correct calculation, we did the wrong result. Furthermore, subdynamics has introduced many new concepts, such as the extension Hilbert or Liouville space, the complex spectral decomposition, the similarity non-unitary transformation, and the differential kinetic equation to the projected density operator and so on, these new concepts have appeared in the subdynamics both in classical and quantum situations to lead it as a candidate to unify equilibrium and non-equilibrium statistics, while in the Feymann formalism my level cannot see this possibility. For example, can the Feymann approach solve complex spectral problems for chaotic maps? Subdynamics is useful to any linear operators not only Hamiltonian or Liouvillian. So in this period, for saving time, I suggest to first consider the Darwinian dynamics, because it may be more meaningful. I think you more know this.

Best Wishes,

Biqiao


On Wed, Mar 7, 2012 at 10:55 PM, ping ao < az5842@yahoo.com > wrote:


Dear Prof. Bi, Qiao:

Let me know if you have not received the 6 paper which you are interested in.

(2) The rigorous approach of Lebowitz and Feynman is completely based on (accepted) quantum mechanis.
Indeed, it generates, in general, a differential and integral equation for sub-system dynamics. It would be interesting to know the samilarity and difference from the differential equation in your subdynamics. In particular, it would be great interest to see whether or not there are differences in physics predictions in some situations.
If there would be no difference in physics, differential equations are indeed usually easier to handle than differential-integral equations.

(3) Two Leggett's representative work in this direction are, if it may be helpful:
A. O. Caldeira and A. J. Leggett, Ann. Phys. (N.Y) v.149, 374 (1983);
A.J. Leggett, et al. Rev. Mod. Phys. v.59, 1 (1987)

Unfortunately, I am not accessible to their pdf files right now.

(4) My 1999 PRB paper with Zhu is on the correct treatment of vortex dynamics, sent you in previous message ( iii) paper ) .
Nonlinear phenomena have emerging entities, such as topological defects (vortices, magenetic monopoles, fractional charges, etc) and solitons.
In my experience, straightforward extension of Green's function from linear limit can be dangerous and can easily lead to incorrect results.
Will be happy to discuss with you what I know.

(5) Darvinian dynamics may be viable candidate for the foundation of nonequilibrium processes.
It naturally contains the idea of (canonical) ensemble.
In my view, the micro-canonical ensemble has nothing to do with stastical mechanics.
It is pleasure to find an active group of scientists in China working on such fundamental and pratically very useful problems.


Best,

Ao, Ping




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