Holographic fluctuations and the principle of minimal complexity

We discuss, from a quantum information perspective, recent proposals of Maldacena, Ryu, Takayanagi, van Raamsdonk, Swingle, and Susskind that spacetime is an emergent property of the quantum entanglement of an associated boundary quantum system. We review the idea that the informational principle of minimal complexity determines a dual holographic bulk spacetime from a minimal quantum circuit U preparing a given boundary state from a trivial reference state. We describe how this idea may be extended to determine the relationship between the fluctuations of the bulk holographic geometry and the fluctuations of the boundary low-energy subspace. In this way we obtain, for every quantum system, an Einstein-like equation of motion for what might be interpreted as a bulk gravity theory dual to the boundary system.Comment: 10 pages, 4 figure

Fermionic Hopf solitons and Berry's phase in topological surface superconductors

A central theme in many body physics is emergence - new properties arise when several particles are brought together. Particularly fascinating is the idea that the quantum statistics may be an emergent property. This was first noted in the Skyrme model of nuclear matter, where a theory formulated entirely in terms of a bosonic order parameter field contains fermionic excitations. These excitations are smooth field textures, and believed to describe neutrons and protons. We argue that a similar phenomenon occurs in topological insulators when superconductivity gaps out their surface states. Here, a smooth texture is naturally described by a three component real vector. Two components describe superconductivity, while the third captures the band topology. Such a vector field can assume a 'knotted' configuration in three dimensional space - the Hopf texture - that cannot smoothly be unwound. Here we show that the Hopf texture is a fermion. To describe the resulting state, the regular Landau-Ginzburg theory of superconductivity must be augmented by a topological Berry phase term. When the Hopf texture is the cheapest fermionic excitation, striking consequences for tunneling experiments are predicted

Why gravity is not an entropic force

The remarkable connections between gravity and thermodynamics seem to imply that gravity is not fundamental but emergent, and in particular, as Verlinde suggested, gravity is probably an entropic force. In this paper, we will argue that the idea of gravity as an entropic force is debatable. It is shown that there is no convincing analogy between gravity and entropic force in Verlinde’s example. Neither holographic screen nor test particle satisfies all requirements for the existence of entropic force in a thermodynamics system. As a result, there is no entropic force in the gravity system. Furthermore, we show that the entropy increase of the screen is not caused by its statistical tendency to increase entropy as required by the existence of entropic force, but in fact caused by gravity. Therefore, Verlinde’s argument for the entropic origin of gravity is problematic. In addition, we argue that the existence of a minimum size of spacetime, together with the Heisenberg uncertainty principle in quantum theory, may imply the fundamental existence of gravity as a geometric property of spacetime. This provides a further support for the conclusion that gravity is not an entropic force

Promoting Social Justice with Open Source Software and Service Learning

The open source movement seems to be gaining momentum due to a variety of factors. One beneficial use of open source software is the potential to help promote social justice. By lowering financial and intellectual property barriers, F/OSS can be used to bridge digital divides. At the core of social justice is the notion of equality of opportunity. Through the use of F/OSS, information technology literacy can be promoted among groups that might not otherwise have access to the tools necessary to build such literacy. This paper reports on an ongoing project that embodies this idea within a service learning context. While the project is in its emergent stages, early indications are that it has considerable potential

A model of a trust-based recommendation system on a social network

In this paper, we present a model of a trust-based recommendation system on a social network. The idea of the model is that agents use their social network to reach information and their trust relationships to filter it. We investigate how the dynamics of trust among agents affect the performance of the system by comparing it to a frequency-based recommendation system. Furthermore, we identify the impact of network density, preference heterogeneity among agents, and knowledge sparseness to be crucial factors for the performance of the system. The system self-organises in a state with performance near to the optimum; the performance on the global level is an emergent property of the system, achieved without explicit coordination from the local interactions of agent

Truthmaking and the Mysteries of Emergence

The concept of truthmaking, the idea that when a statement is true, there is typically something about the world in virtue of which it is true, has garnered much interest in recent metaphysics. Often, the motivation has been the thought that truthmaking can provide a new perspective on an important issue. This paper evaluates the claim that truthmaking can play a substantive role in defining an unproblematic notion of emergence. For despite playing an important role in philosophical discourse over the past 100 years, it has often been thought that there is something mysterious about the notion of emergence. It has recently been argued, however, that once emergent properties are characterized as those that, while “ontologically dependent” are yet needed as truthmakers emergence and emergent properties prove unproblematic. In response, I argue that there is reason to doubt that truthmaking can play an important role in formulating an unproblematic yet recognizable notion of emergence. I argue that it is consistent with truthmaking being unable to play a substantive role in emergentism that truthmaking can play a more significant role in characterizing an attractive middle ground between reductive and nonreductive physicalism

Lawson on Veblen on Social Ontology

This paper discusses Lawson’s use of Veblen’s concept of ‘neoclassical economics’ and argument that the category of neoclassical economics should be jettisoned on the grounds that it obfuscates effective critique of mainstream economics. The paper links Lawson’s critique of closed systems and Veblen’s cumulative causation view by offering a reflexivity, feedback loop formulation of the latter aimed at overcoming the pre-Socratic dichotomy between Heraclitian and Parmenidean ontological thinking. The paper then reviews what this implies for three key social ontology doctrines: social reality as processual and highly transient; emergence and the appearance of novelty; the internal relatedness of social reality. Final remarks address the use of the ‘neoclassical economics’ concept

The Compatibility of Downward Causation and Emergence

In this paper, I shall argue that both emergence and downward causation, which are strongly interconnected, presuppose the presence of levels of reality. However, emergence and downward causation pull in opposite directions with respect to my best reconstruction of what levels are. The upshot is that emergence stresses the autonomy among levels while downward causation puts the distinction between levels at risk of a reductio ad absurdum, with the further consequence of blurring the very notion of downward. Therefore, emergence and downward causation are not fit to each other vis-a-vis the concept of level