Self-Organization and Emergence

Heinz von Foerster 100

Organizing Institutions:

Heinz von Foerster Gesellschaft / Wien

ASC – American Society for Cybernetics

WISDOM – Wiener Institut für

sozialwissenschaftliche Dokumentation und Methodik

Institut für Zeitgeschichte | Universität Wien

AINS – Austrian Institute for Nonlinear Studies

Heinz von Foerster Gesellschaft / Wien

ASC – American Society for Cybernetics

WISDOM – Wiener Institut für

sozialwissenschaftliche Dokumentation und Methodik

Institut für Zeitgeschichte | Universität Wien

AINS – Austrian Institute for Nonlinear Studies

Bei-Lok Hu

Emergence, Gravity and Thermodynamics

University of Maryland, College Park

I present some latest thoughts on three inter-related subjects:

1) Emergence: After describing three different senses of emergence, I point out that effective

field theory (EFT) or renormalization group (RG) is a necessary but not sufficient set of conceptual

means for describing emergence. EFT or RG [1] may suggest how different physics manifest at

different scales, but we also need to identify the mechanisms or processes whereby different

levels of structures and the laws governing them, including the symmetry principles, emerge.

That depends on deeper interplay of collectivity, complexity, stochasticity and self-organization.

2) Emergent Gravity: There are at least two intimately related veins in viewing gravity as emergent:

a) `General Relativity as Hydrodynamics’ [2] in the sense that gravity is an effective theory valid

only at the long wavelength, low energy limit of some underlying theory (quantum gravity) for the
microscopic structures of spacetime and matter. b) Gravity as Thermodynamics [3], where such a view
is often shaped by considering the effects of an event horizon on the quantum fluctuations of a field,
first shown by Bekenstein and known today as the holography principle.

3) Gravity and Thermodynamics: Since both gravity and thermodynamics are classical theories of

macroscopic structures, if a deep connection exists, we should be able to see their direct relation

at this level, without relying on arguments invoking the microscopic structure of matter

(quantum fluctuations). This is posed as a challenge [4], one which physicists in the 19c

in principle may be able to resolve. If we can meet this challenge we may see the simpler and

deeper connection between gravity and thermodynamics without invoking quantum mechanics. If we
fail we will perhaps see more clearly the essential role of quantum physics in explaining gravity
and the necessary implication that a) either the macroscopic world is fundamentally quantum [5] or

b) quantum mechanics is also emergent from a deeper structure or as a form of organizational rules
like statistical mechanics.

[1] For a recent meeting on this topic, see, e.g.,

http://www.perimeterinstitute.ca/Events/Emergence_and_Effective_Field_Theories/ Schedule/

[2] This view can be traced to Sakharov (1968). For references to writings of the major proponents
see, e.g., B. L. Hu, “Emergent /Quantum Gravity: Macro/Micro Structures of Spacetime” Invited talk

DICE 2008. J. Phys. Conf. Ser. 174 (2009) 012015 [arXiv:0903.0878]

[3] For references and critiques, see, e.g., B. L. Hu, “Gravity and Nonequilibrium Thermodynamics of
Classical Matter” Int. J. Mod. Phys. D 20:697-716 (2011) [arXiv:1010.5837]

[4] B. L. Hu, “Gravity and Thermodynamics: What exactly do we want?” Invited talk at ESF Exploratory
Workshop: Gravity and Thermodynamics, SISSA Sept 8, 2011

[5] E.g, B. L. Hu, “Can Spacetime be a Condensate?” Int. J. Theor. Phys. 44 (2005) 1785-1806

[arXiv:gr-qc/0503067v2]