Dear Prof.Ed Gerck,

I think this is a good idea. We can model social collective behavior by fluid physics. However, human psychology is an extremely complex activity, so our model is complex.

I found some helpful materials :

Mathematical Modeling of Collective Behavior in Socio-Economic and Life Sciences:

https://www.google.com.vn/search?hl=vi&tbo=p&tbm=bks&q=isbn:0817649468

The Physical Modelling of Human

Social Systems:

http://www.uvm.edu/~cmplxsys/wordpress/wp-content/uploads/reading-group/pdfs/2007/ball2003a.pdf

The physical modelling of society:

https://www.philipball.co.uk/articles/physics-of-society/73-the-physical-modelling-of-society

Hello Lam,

Thank you for the references in your reply. I verified them with interest and the usual statistical model appears, for example as used in the kinetic theory gases, a theory with "features analogous to those that characterize the notion of universality in statistical physics".

None of the references, however, used the physics of fluids, where statistics can be used but is a second fiddle. To contrast, the statistical physics model deal with quantities that are predictable per se, ignoring the reasons for their influence or their effects if not statistical.

In physics of fluids, however, the reasons for thixotrpoic (e.g.) behavior are based on a model of cause-effect, not expectation-effect as in statistics. This precludes the common (correct) criticism of the use of statistical methods, that "expectation is not causation", and, at the same time, presents a cause-effect model that seems to be missing in social collective studies, and is offered in the non-statistical physics of fluids [1-3].

Thus, our motivation is to use a non-statistical physics model, as given by the physics of fluids. 

Cheers, Ed Gerck 

[1] For example of an application, see "Principle of Soil Physics" at https://books.google.com/books?id=XSkvi33OMFwC&pg=PA246&lpg=PA246&dq=physics+of+fluids+thixotropic&source=bl&ots=2mNV9TNoMp&sig=7YJ-liOo-UZ3yFkpY1MKBVilOMg&hl=en&sa=X&ved=0ahUKEwiQ7tjbq77WAhVR42MKHVsyCzE4ChDoAQgmMAE#v=onepage&q=physics%20of%20fluids%20thixotropic&f=false

[2] http://aip.scitation.org/doi/10.1063/1.3536654

[3] https://en.m.wikipedia.org/wiki/Fluid_mechanics

Hello Lam and all,

Complementing my previous answer,  we are trying to find first something that, mutatis mutandis, plays the role of the Knudsen number in physics.

Citing Wikipedia, "The Knudsen number (Kn) is a dimensionless number defined as the ratio of the molecular mean free path length to a representative physical length scale. This length scale could be, for example, the radius of a body in a fluid." 

The Knudsen number is important in physics because it determines whether statistical physics or fluid physics could be used to model a situation. If the Knudsen number is near or greater than one, when the mean free path of a molecule is comparable to a length scale of the problem, then statistical methods should be used. Of course, statistical physics can be applied also for all ranges of Knudsen numbers.

In social collective behavior, if we are dealing with a situation where a person's mean  path length between interactions (i.e., when it is free) is much smaller than a typical length of the problem, we expect their "Knudsen number" to be very low (i.e. less than unity).

Low "Knudsen number" is relatively easy to occur in mass phenomena, and one should, thus, expect to use physics of fluids there, not just statistics. When one is dealing with individual behavior, however, statistical methods should prevail. 

One should find that social collective behavior is well-modelled by fluid physics.

Cheers,  Ed Gerck 

Hello all,

I want to reflect on two private comments.

1. Why would a fluid model be better than a gas model for a socio-economic model of collectives?

Because a gas model would lead to a statistical treatment, while the fluid model can lead to a cause-effect model without obscuring the cause and maintaing the causation model by the conservation laws:

• Conservation of mass
• Conservation of energy
• Conservation of momentum

and others, explicitly.

2. What could be shear stress in this treatment? 

In physics, it is of the same dimension as pressure. But while pressure causes compression, shear stress causes shear. You could think of it as in effect following the force direction, as an open box sitting on a horizontal, rough table (with friction) and receiving a force parallel to the table, on top of the box. Better yet, shear stress is the component of stress coplanar with a desired material cross section; shear stress arises from the force vector component parallel to that cross section. In the socio-economic case, shear stress is not just in the direction of a component of force applied on the element, but still in the direction of a component of force; in the "open box on the table" example above, the shear stress is perpendicular to the table surface, not in the direction of gravity (the table surface is  horizontal) force, but to the applied force that is perpendicular to the table top.

In a fluid, shear stress is defined as a force per unit area, acting parallel to an infinitesimal surface element. Shear stress is primarily caused by friction between fluid particles, due to fluid viscosity.

Cheers, Ed Gerck 

Hello all,

sharing a private comment,  as it may be helpful, one should find that social collective behavior is well-modelled by fluid physics, and find thus a better alternative to statistical methods in such a case, using methods that deal with causation, not just blind expectations, and explain what we see.

Cheers, Ed Gerck 

Hi Ed,

That's a very interesting idea!

I really don't know about the topic but I have an acquaintance that models the stock exchange market behavior using equations very similar to the Navier-Stokes ones, assuming a turbulent regime. I cannot give you a reference because this is a proprietary model and my acquaintance makes (a lot of) money with it.

The stock exchange is an example of social behavior, isn't it?

Hello Maria,

Thank you. Yes, I would say that the stock market is an example of massive social behavior.  In particular, if something is NOT objectively true, but may have a coherent response that means true to a group that then believes it to be objectively true, the group can act based in that true feeling (for the group, it is true). For example, the mass hysteria in the US case of the wiches of Salem. It happened also in the crash of 1929 and may act now, with stock valuation independent of production, where a phone may cost more than a month's wage.

Cheers,  Ed Gerck 

Hello all,

Recent events In Europe, the USA, and other countries, in reference to refugees specifically, not conflated with immigration, shows a collective effect that cannot be ignored.

Refugees are also not individuals who are forced to move, by violence or otherwise; they show an stimulated cause (such as volcanic eruption, war), not spontaneously, and collective.

It is possible that refugees can be modelled, mutatis mutandis (making necessary alterations while not affecting the main point at issue), by the physics of fluids, as investigated in this question, with elements of mass hysteria present, and other noted points, characteristics of collective movements.

In that analysis, movement can be studied by a Deborah number, and other parameters, showing the resulting strategic weakness of the position of the preventors, even though amply tactically capable, and the collective effect of the refugees in overcoming any acceptable defense.

Recent separation of (mainly) a large and still covert number of mothers and children in the USA, followed similar patterns worldwide, of coercion and intimidaton as reaction forces to prevent refugees from being accepted, and stemming the flow.

Based on these observations, and the numbers of actors, both as refugees and as their preventors, it seems that the physics of fluids provides that the behavior can, indeed, be quite sudden, cumulative, and at first-sight surprising, and risks becoming catastrophic.

A catastrophic result is, for example, the quick overrun of barriers or defenses, visible in several places in Europe, where the existing infrastructure cannot hold the number of refugees, and rapid killing, directly or indirectly, is considered not socially acceptable as a solution.

This is a thixotropic effect that can happen in the USA south frontier, which, geographically presents a confluence of a large border with a deep source, as a supersonic nozzle, which divergence offers least resistance to expanding flow, and increasing porosity.

Social deterrence, through the action of instilling doubt or fear of the consequences, will likely be innefective for refugees, who are not voluntary immigrants per se, but running from an external, unwinnable cause that already instills fear of the consequences, such as a war, while unsustainable (as shown) in the present state of affected societies. It would be like trying social deterrence to stop a one-month old baby from using diapers, good luck with cleaning. 

We suggest that this collective dynamics at the border cannot be effectively contained or prevented, excluding en masse killing. Although it can be delayed, but only at the expense of accumulating pressure, with more flow afterwards. It would help to create effective reduction of creation of refugees, in their original places or far way from the USA border, to prevent the flow from happening, in the first place.

Short of this solution, the system will tend to flow collectively, not individually, to relieve faster the pressure at the source, with ever reducing resistance to the divergent flow inward the USA south border.

Cheers, Ed Gerck