This is not the common definition of "emergent properties" in physics. I think most physicists would say that "emergent properties" are properties that we have equations for, but we do not know how to derive those equations from the equations describing the fundamental laws. That in no way means such properties are not governed by the fundamental laws. It just means we don't understand how (yet).Cato said:true emergent properties -- as defined by behavior of matter that cannot be reduced to fundamental physical law
Where? And was whoever told you using the same definition of "emergent property" that you are using? Or were they using a definition more like the one I gave above?Cato said:I have been told that the Fractional Quantum Hall Effect is an example of an emergent property.
One should distinguish between strong emergence and weak emergence. Strong emergence is that something cannot be reduced to fundamental laws in principle. Weak emergence is that something cannot easily be reduced to fundamental laws in practice. In physics, by emergence, one usually means weak emergence. In particular, FQHE is weakly emergent, not strongly emergent.Cato said:TL;DR Summary: I have heard that the Fractional Quantum Hall Effect is a true emergent property. I have never believed that emergent properties exist. Is this an example of one?
I do not think that true emergent properties -- as defined by behavior of matter that cannot be reduced to fundamental physical law -- exist.
Quantum many-body theory is full of "emergent properties". This is of course a buzz word. What's usually meant by this are collective excitations of a many-body system. These can often be described as "quasi particles", i.e., with a formalism of many-body quantum-field theory where these excitations can be approximately described in a similar way as "particle states" are described. These "quasi particles" need not be in any way related to true/elementary particles though. E.g., there are quasi particles with a "fractional charge", although of course there are no elementary particles with charges different from integer multiples of the elementary charge, ##e##.Cato said:TL;DR Summary: I have heard that the Fractional Quantum Hall Effect is a true emergent property. I have never believed that emergent properties exist. Is this an example of one?
I do not think that true emergent properties -- as defined by behavior of matter that cannot be reduced to fundamental physical law -- exist. Yet I have been told that the Fractional Quantum Hall Effect is an example of an emergent property. What is the consensus?
By your definition something is "strongly emerent" simply, if it cannot be understood by contemporarily known physical theories. I think all of condensed-matter physics is pretty far from that, although there are phenomena which cannot be explained entirely "from first principles".Demystifier said:One should distinguish between strong emergence and weak emergence. Strong emergence is that something cannot be reduced to fundamental laws in principle. Weak emergence is that something cannot easily be reduced to fundamental laws in practice. In physics, by emergence, one usually means weak emergence. In particular, FQHE is weakly emergent, not strongly emergent.
Is there anything which is strongly emergent? It's hard to tell, some suspect that consciousness might be strongly emergent, but that's another topic.
The Fractional Quantum Hall Effect is a phenomenon that occurs in two-dimensional electron systems at low temperatures and high magnetic fields. It is characterized by the emergence of fractional charges and quantized Hall conductance, and is considered to be one of the most significant discoveries in condensed matter physics.
The FQHE is considered an emergent property because it arises from the collective behavior of many interacting electrons in a system, rather than being a property of individual electrons. This means that the behavior of the system as a whole cannot be explained by simply understanding the behavior of its individual components.
The FQHE is caused by the strong interactions between electrons in a two-dimensional system, as well as the presence of a strong magnetic field. These interactions lead to the formation of a special type of electron state called a "fractional quantum Hall state", which exhibits the emergent properties of the FQHE.
The FQHE has potential applications in areas such as quantum computing and topological quantum computing. It has also been used in the development of new materials with unique electronic properties, and has implications for our understanding of fundamental physics concepts such as fractional charges and topological order.
The FQHE is related to other quantum Hall effects, such as the Integer Quantum Hall Effect (IQHE), in that they both involve the quantization of Hall conductance. However, the FQHE is distinct in that it involves fractional charges and is only observed in certain conditions, such as at low temperatures and high magnetic fields. Additionally, the FQHE is considered to be a more complex and intriguing phenomenon compared to the IQHE.