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## Publications

Publications (528)

John Barrow wrote dozens of books and hundreds of papers, including more than 10 papers and one book during his final illness, addressing a grand problem: why is the universe the way it is? What is the fundamental nature of physics, and what are its cosmological outcomes? His most famous book was on the Anthropic Principle with Frank Tipler, and hi...

The value and use of Trümper’s formulation of the Bianchi identities in terms of the decomposition of the Weyl tensor into electric and magnetic parts are considered.

We prove here a long standing conjecture in general relativity, that if barotropic perfect fluid is moving in a shear free way, then it must be either expansion free or rotation free.

Kurt Gödel opposed the reductionist viewpoint of logical positivism. The arguments I give below show he is correct. The reductionist explanation he opposed is doomed to failure.

Significant challenges exist globally regarding literacy teaching and learning. To address these challenges, key features of how the brain works should be taken into account. First, perception is an active process based in detection of errors in hierarchical predictions of sensory data and action outcomes. Reading is a particular case of this non-l...

In this paper we show in a covariant and gauge invariant way that in general relativity, tidal forces are actually a hidden form of gravitational waves. This must be so because gravitational effects cannot occur faster than the speed of light. Any two body gravitating system, where the bodies are orbiting around each other, may generate negligible...

Significant challenges exist globally regarding literacy teaching and learning, particularly in poor socio-economic settings in countries of the Global South. In this paper we argue that to address these challenges, major features of how the brain works that are currently ignored in the educational literature should be taken into account. First, pe...

In this paper we present a brain-inspired cognitive architecture that incorporates sensory processing, classification, contextual prediction, and emotional tagging. The cognitive architecture is implemented as three modular web-servers, meaning that it can be deployed centrally or across a network for servers. The experiments reveal two distinct op...

Significant challenges exist globally regarding literacy teaching and learning, particularly in poor socio-economic settings in countries of the Global South. In this paper we argue that to address these challenges, major features of how the brain works that are currently ignored in the educational literature should be taken into account. First, pe...

The causal closure of physics is usually discussed in a context free way. Here I discuss it in the context of engineering systems and biology, where strong emergence takes place due to a combination of upwards emergence and downwards causation (Ellis, Emergence in Solid State Physics and Biology, 2020, arXiv:2004.13591). Firstly, I show that causal...

There has been much controversy over weak and strong emergence in physics and biology. As pointed out by Phil Anderson in many papers, the existence of broken symmetries is the key to emergence of properties in much of solid state physics. By carefully distinguishing between different types of symmetry breaking and tracing the relation between brok...

This paper responds to claims that causal closure of the underlying microphysics determines brain outcomes as a matter of principle, even if we cannot hope to ever carry out the needed calculations in practice. Following two papers of mine where I claim firstly that downward causation enables genuine causal powers to occur at higher emergent levels...

The causal closure of physics is usually discussed in a context free way. Here I discuss it in the context of engineering systems and biology, where strong emergence takes place due to a combination of upwards emergence and downwards causation [Ellis 2020]. Firstly, I show that causal closure is strictly limited in terms of spatial interactions bec...

In this paper we present a brain-inspired cognitive architecture that incorporates sensory processing, classification, contextual prediction, and emotional tagging. The cognitive architecture is implemented as three modular web-servers, meaning that it can be deployed centrally or across a network for servers. The experiments reveal two distinct op...

This paper argues in favour of moral realism, and hence distinguishes ethics (socially determined ideas of good and bad) from morality (eternal and unchanging standards of what is in fact good and bad). Morality cannot be determined by any argument based in scientific understandings, for it is of a completely different nature; there is no scientifi...

Contextual emergence was originally proposed as an inter-level relation between different levels of description to describe an epistemic notion of emergence in physics. Here, we discuss the ontic extension of this relation to different domains or levels of physical reality using the properties of temperature and molecular shape (chirality) as detai...

The paper "On the Topic of Emergence from an Effective Field Theory Perspective" by Luu and Meissner [arXiv:1910.13770] criticizes claims of strong emergence in physics and biology, such as those in [Ellis 2016], inter alia challenging the idea that there is purpose in living systems. They argue on the basis of the power of Effective Field Theories...

Microphysical laws are time reversible, but macrophysics, chemistry and biology are not. This paper explores how this asymmetry (a classic example of a broken symmetry) arises due to the cosmological context, where a non-local Direction of Time is imposed by the expansion of the universe. This situation is best represented by an Evolving Block Univ...

Stephen Hawking's contributions to the understanding of gravity, black holes and cosmology were truly immense. They began with the singularity theorems in the 1960s followed by his discovery that black holes have an entropy and consequently a finite temperature. Black holes were predicted to emit thermal radiation, what is now called Hawking radiat...

George Ellis and Julien Larena highlight the possibility that the universe could be curved and closed, and explore the theoretical importance of this possibility.

We review current theoretical cosmology, including fundamental and mathematical cosmology and physical cosmology (as well as cosmology in the quantum realm), with an emphasis on open questions.

In this paper we show in a covariant and gauge invariant way that in general relativity, tidal forces are actually a hidden form of gravitational waves. This must be so because gravitational effects cannot occur faster than the speed of light. Any two body gravitating system, where the bodies are orbiting around each other, may generate negligible...

Microphysical laws are time reversible, but macrophysics, chemistry and biology are not. This chapter explores how this asymmetry (a classic example of a broken symmetry) arises due to the cosmological context, where a non-local Direction of Time emerges due to the expansion of the universe. This situation is best represented by an Evolving Block U...

In this paper we draw inspiration from the human visual system, and present a bio-inspired pre-processing stage for neural networks. We implement this by applying a log-polar transformation as a pre-processing step, and to demonstrate, we have used a naive convolutional neural network (CNN). We demonstrate that a bio-inspired pre-processing stage c...

Digital computers carry out algorithms coded in high level programs. These abstract entities determine what happens at the physical level: they control whether electrons flow through specific transistors at specific times or not, entailing downward causation in both the logical and implementation hierarchies. This paper explores how this is possibl...

Sensory predictions by the brain in all modalities take place as a result of bottom-up and top-down connections both in the neocortex and between the neocortex and the thalamus. The bottom-up connections in the cortex are responsible for learning, pattern recognition, and object classification, and have been widely modelled using artificial neural...

We review current theoretical cosmology, including fundamental and mathematical cosmology and physical cosmology (as well as cosmology in the quantum realm), with an emphasis on open questions.

This article proposes the following themes: 1. Space time must be discrete at the micro level. 2. Holonomy is central to any foundational approach to relating spacetime and quantum mechanics. 3. The gravitational field equations should be trace free: gravity is essentially a conformal theory. 4. Times passes; past, present, and future are fundament...

Digital computers carry out algorithms coded in high level programs. These abstract entities determine what happens at the physical level: they control whether electrons flow through specific transistors at specific times or not, entailing downward causation in both the logical and implementation hierarchies. This paper explores how this is possibl...

Standard artificial neural networks model key cognitive aspects of brain function, such as learning and classification, but they do not model the affective (emotional) aspects; however primary and secondary emotions play a key role in interactions with the physical, ecological, and social environment. These emotions are associated with memories whe...

Stephen Hawking's contributions to the understanding of gravity, black holes and cosmology were truly immense. They began with the singularity theorems in the 1960s followed by his discovery that black holes have an entropy and consequently a finite temperature. Black holes were predicted to emit thermal radiation, what is now called Hawking radiat...

Current cosmological models require the universe to be in a very smooth initial state before the onset of inflation, a situation to which Penrose ascribes a vanishingly small probability, leading to his proposal of a conformal cyclic cosmology. We present an alternative paradigm, in which the Higgs plays the role of dilaton and resolves this proble...

Biology differs fundamentally from the physics that underlies it. This paper 1 proposes that the essential difference is that while physics at its fundamental level is Hamiltonian, in biology, once life has come into existence, causation of a contextual branching nature occurs at every level of the hierarchy of emergence at each time. The key featu...

In general relativity, the parallel transfer of a vector around a closed curve in spacetime, or along two curves that together form a closed loop, usually results in a nonzero deficit angle between the vector’s initial and final positions. We show that such holonomy in the McVittie spacetime, which represents a gravitating object imbedded in an exp...

Viele Kosmologen fasziniert die Idee, es gebe unzählige Paralleluniversen mit jeweils eigenen Naturgesetzen. Doch das Problem ist: Niemand wird je nachprüfen können, ob ein solches Multiversum überhaupt existiert (aus Spektrum der Wissenschaft 11/2011).

This paper is an in depth implementation of the proposal (Ellis 2012 Ann. Phys. NY 327 1890-932) that the quantum measurement issue can be resolved by carefully looking at top-down contextual effects within realistic measurement contexts. The specific setup of the measurement apparatus determines the possible events that can take place. The interac...

The present day standard cosmological model is a great theoretical achievement. This chapter surveys the main themes that have arisen and issues that are still oustanding.

A problem in general relativity is, how the gravitational field can transfer energy and momentum between different distant places. The issue is that matter stress tensor is locally conserved, with no explicit interaction with the free gravitational field, which is represented by the Weyl tensor. In this paper we explicitly construct an interaction...

Holonomy in general relativity results from the parallel transfer of a vector field around a closed curve in spacetime, or along two curves which together form a closed loop. We show that holonomy in the McVittie spacetime, which represents a gravitating object imbedded in an expanding universe, can in principle be used to measure the expansion of...

David Hilbert famously argued that infinity cannot exist in physical reality. The consequence of this statement — still under debate today — has far-reaching implications.

This paper is an in depth implementation of the proposal that the quantum measurement issue can be resolved by carefully looking at top-down contextual effects within realistic measurement contexts. The specific setup of the measurement apparatus determines the possible events that can take place. The interaction of local heat baths with a quantum...

The purpose of this investigation is to demonstrate that one is unable to understand the operation of the brain without taking top-down effects into account. This is demonstrated by looking in turn at evolutionary and developmental aspects, then at functional aspects related to sensory systems, learning processes, and motor processes that lead to a...

This paper revisits the controversy concerning whether gravitational lensing effects make a significant difference to estimation of distance to the Cosmic Microwave Background last scattering surface in cosmology. A recent paper by Kaiser and Peacock supports a previous paper by Weinberg stating that such affects average to zero because of energy c...

How can a universe that is ruled by natural laws give rise to aims and intentions? Whether or not a human observer exists, the natural laws would continue to operate as they are indefinitely. The key difference between physics and biology is function or purpose. There is, in the standard scientific interpretation, no purpose in the existence of the...

A problem in general relativity is, how the gravitational field can transfer energy and momentum between different distant places. The issue is that matter stress tensor is locally conserved, with no explicit interaction with the free gravitational field, which is represented by the Weyl tensor. In this paper we explicitly construct an interaction...

Spekulative Theorien bedürfen laut einigen Forschern keiner experimentellen Überprüfung, um als wissenschaftlich zu gelten. Dieser Ansatz untergräbt die Wissenschaft.

A conflict exists between field biologists and physiologists ("functional biologists" or "evolutionary ecologists") on the one hand and those working in molecular evolution ("evolutionary biologists" or "population geneticists") on the other concerns the relative importance of natural selection and genetic drift. This paper is concerned with this i...

Physical emergence - crystals, rocks, sandpiles, turbulent eddies, planets, stars - is fundamentally different from biological emergence - amoeba, mice, humans - even though the latter is based in the former. This paper points out that the essential difference is that causation in biological systems has a logical nature at each level of the hierarc...

In this paper we derive a general solution for the most general rotating and twisting locally rotationally symmetric spacetimes. This is achieved in three steps. First we decompose the manifold via 1+1+2 semi-tetrad formalism that yields a set of geometrical and thermodynamic scalars for the spacetime. We then recast the Einstein field equations in...

We construct models of static spherical distributions of perfect fluid in trace--free Einstein gravity theory. The equations governing the gravitational field are equivalent to the standard Einstein's equations however, their presentation is manifestly different which motivates the question whether new information would emerge due to the nonlineari...

In this paper we investigate whether the holographic principle proposed in string theory has a classical counterpart in general relativity theory. We show that there is a partial correspondence: at least in the case of vacuum Petrov type D spacetimes that admit a non-trivial Killing tensor, which encompass all the astrophysical black hole spacetime...

Downward causation (first defined by Campbell, 1974) is both a philosophical concept and an apparent phenomenon of nature attracting great controversy. Most scientists usually assume that all observable phenomena derive from elemental fundamental physics, so that even human behaviours ultimately result from interactions of subatomic particles, via...

Recent advances suggest that the concept of information might hold the key to unravelling the mystery of life’s nature and origin. Fresh insights from a broad and authoritative range of articulate and respected experts focus on the transition from matter to life, and hence reconcile the deep conceptual schism between the way we describe physical an...

We establish the existence and find the necessary and sufficient conditions for a new class of solutions of locally rotationally symmetric spacetimes that have nonvanishing rotation and spatial twist simultaneously. We transparently show that the existence of such solutions demands nonvanishing and bounded heat flux and these solutions are self-sim...

We present the particle creation probability rate around a general black hole as an outcome of quantum fluctuations. Using the uncertainty principle for these fluctuation, we derive a new ultraviolet frequency cutoff for the radiation spectrum of a dynamical black hole. Using this frequency cutoff, we define the probability creation rate function f...

Numerical studies of gravitational collapse to black holes make use of apparent horizons, which are intrinsically foliation-dependent. We expose the problem and discuss possible solutions using the Hawking quasilocal mass. In spherical symmetry, we present a physically sensible approach to the problem by restricting to spherically symmetric spaceti...

We establish the existence and find the necessary and sufficient conditions for a new class of solutions of Locally Rotationally Symmetric spacetimes that have non vanishing rotation and spatial twist simultaneously. We transparently show that the existence of such solutions demand non vanishing and bounded heat flux and these solutions are self si...

The issue of whether the unfolding of events in the world can be considered a computation is explored in this paper. We come to different conclusions for inert and for living systems ('no' and 'qualified yes', respectively). We suggest that physical computation as we know it exists only as a tool of complex biological systems: us.

One of the most astonishing things in the physical world is the way that mind emerges from matter.

This chapter looks at the basis of emergent complexity in physical systems, including life, as well as in logical systems.

Top-down causation is a generic concept. The previous chapters have given many examples.

The previous chapters have given numerous examples of top-down causation. They appear to make the case for existence of top-down causation unshakeable.

At the bottom level, what happens is based on physics: it enables the emergence of higher level entities, which then in turn act down on the lower level components.

This chapter looks broadly at how the overall thesis of the book relates to the human mind and brain, which develop to be what they are because they are located in a specific society. The main claim will be that one cannot begin to understand the brain properly without taking top-down causation into account. An example is that you are able to read...

This chapter considers issues of emergence and causation in the case of digital computers, as a warm-up example before giving a general viewpoint on these topics in the next chapter. It will be shown that top-down causation is central to their functioning.

The conclusion arising from the arguments given in this book is that there are other forms of causation than those encompassed by physics and physical chemistry alone, or even in genetics and neuroscience.

Based on a recent proposal for the gravitational entropy of free gravitational fields, we investigate the thermodynamic properties of black hole formation through gravitational collapse in the framework of the semitetrad 1+1+2 covariant formalism. In the simplest case of an Oppenheimer-Snyder-Datt collapse we prove that the change in gravitational...

We argue that if particularly powerful electromagnetic afterglows of the gravitational waves bursts will be observed in the future, this could be used as a strong observational support for some suggested quantum alternatives for black holes (e.g., firewalls and gravastars). A universal absence of powerful afterglows should be taken as a suggestive...

Physics underlies all complexity, including our own existence: how is this possible? How can our own lives emerge from interactions of electrons, protons, and neutrons? This book considers the interaction of physical and non-physical causation in complex systems such as living beings, and in particular in the human brain, relating this to the emerg...

With this article, we initiate a systematic study of some of the symmetry
properties of unimodular gravity, building on much of the known structure of
general relativity, and utilising the powerful technology developed in that
context. In particular, we show, up to four-points and tree-level, that the KLT
relations of perturbative gravity hold for...

We consider the holographic principle in the case of standard General
relativity theory. We show that at least in the case of vacuum Petrov type D
spacetimes that admit a non-trivial Killing tensor and which encompass all the
astrophysical black hole spacetimes, it is equivalent to the null initial value
theorem for general relativity.

We present the particle creation probability rate around a general black hole
as an outcome of quantum fluctuations. Using the uncertainty principle for
these fluctuation, we derive a new ultraviolet frequency cutoff for the
radiation spectrum of a dynamical black hole. Using this frequency cutoff, we
define the probability creation rate function f...

We use the phase plane analysis technique of Madsen and Ellis to consider a
universe with a true cosmological constant as well as a cosmological "constant"
that is decaying. Time symmetric dynamics for the inflationary era allows
eternally bouncing models to occur. Allowing for scalar field dynamic
evolution, we find that if dark energy decays in t...

No. In a number of papers Green and Wald argue that the standard FLRW model approximates our Universe extremely well on all scales, except close to strong field astrophysical objects. In particular, they argue that the effect of inhomogeneities on average properties of the Universe (backreaction) is irrelevant. We show that this latter claim is not...

This is Chapter 1 in the book General Relativity and Gravitation: A
Centennial Perspective, Edited by Abhay Ashtekar (Editor in Chief), Beverly
Berger, James Isenberg, Malcolm MacCallum. Publisher: Cambridge University
Press (June, 2015). It gives a survey of themes that have been developed during
the 100 years of progress in general relativity the...

This article reviews the properties and limitations associated with the existence of particle, visual, and event horizons in cosmology in general and in inflationary universes in particular, carefully distinguishing them from 'Hubble horizons'. It explores to what extent one might be able to probe conditions beyond the visual horizon (which is clos...

Among the different methods to derive particle creation, finding the quantum
stress tensor expectation value gives a covariant quantity which can be used
for examining the back-reaction issue. However this tensor also includes vacuum
polarization in a way that depends on the vacuum chosen. Here we review
different aspects of particle creation by lo...

In a previous paper [arXiv:1308.1852] we showed how a finite system of
discrete particles interacting with each other via Newtonian gravitational
attraction would lead to precisely the same dynamical equations for homothetic
motion as in the case of the pressure-free
Friedmann-Lema\^{i}tre-Robertson-Walker cosmological models of General
Relativity...

Attempts to exempt speculative theories of the Universe from experimental verification undermine science, argue George Ellis and Joe Silk.

This is the text of part of the Cosmology course at the Special Courses at the National Observatory of Rio de Janeiro - CCE. The first part summarises cosmology today, including issues where significant questions reman, and the second part is dedicated to the 1+3 covariant formalism for cosmology.

Based on a recent proposal for the gravitational entropy of free
gravitational fields, we investigate the thermodynamic properties of black hole
formation through gravitational collapse in the framework of the semitetrad
1+1+2 covariant formalism. In the simplest case of an Oppenheimer-Snyder-Datt
collapse we prove that the change in gravitational...

An astrophysical (cosmological) black hole forming in a cosmological context
will be subject to a flux of infalling matter and radiation, which will cause
the outer apparent horizon (a marginal trapping surface) to be spacelike [5].
As a consequence the radiation emitted close to the apparent horizon no longer
arrives at infinity with a diverging r...