Abstract ‘Black Holes and the Edge of Physics’ delves into the mysteries of black holes, and shows how these enigmatic objects may transcend quantum physics. We begin with a review of how black holes form and eventually evaporate, resulting in the notorious problem of ‘information loss’. We show how pilot-wave theory could solve the problem by allowing information to escape at superluminal speeds. We describe an experiment that could test these and related ideas, involving astrophysical black holes in space. The chapter ends with an account of the life cycle of black holes and the role they may play in ‘reprocessing’ our quantum universe.
Abstract ‘Black Holes and the Edge of Physics’ delves into the mysteries of black holes, and shows how these enigmatic objects may transcend quantum physics. We begin with a review of how black holes form and eventually evaporate, resulting in the notorious problem of ‘information loss’. We show how pilot-wave theory could solve the problem by allowing information to escape at superluminal speeds. We describe an experiment that could test these and related ideas, involving astrophysical black holes in space. The chapter ends with an account of the life cycle of black holes and the role they may play in ‘reprocessing’ our quantum universe.
Abstract Beyond the Quantum offers a panoramic rethink of quantum physics, with potentially revolutionary implications for cosmology, quantum gravity, and quantum technology. Properly understood, ‘pilot-wave theory’ provides a deeper foundation for quantum mechanics, while also going beyond it. First proposed in the 1920s by French aristocrat and physicist Louis de Broglie, and revived in the 1950s by American physicist David Bohm, the theory posits hidden particle motions we cannot currently see or control. The theory is usually regarded as merely an alternative account of the same physics we already know. In fact, pilot-wave theory implies a wealth of new and radical physics beyond the reach of quantum mechanics. Pilot-wave theory tells us that quantum physics is a special case of something broader and deeper. In more general ‘nonequilibrium’ conditions, Einstein’s relativity and Heisenberg’s uncertainty break down. Superluminal signalling becomes possible, and quantum particles can be clearly seen and controlled. This new physics could have left traces in the early universe, and it might be visible today in radiation from exploding primordial black holes. Harnessing this new physics would have transformative technological implications, in particular for communication, cryptography, and computing. Drawing intriguing parallels between the present era of quantum physics and past episodes of scientific confusion, this book tells the story of how pilot-wave theory was discovered and abandoned, revived and reconstructed, and how today it can pave the way to a new and radical physics beyond the quantum.
Abstract ‘Seeing the Impossible’ delves into the details of pilot-wave theory and of how it can account for the mysteries of quantum physics. We begin with the iconic two-slit experiment and show how it can be understood in terms of particles moving through one hole or the other (despite widespread claims to the contrary). We give a clear explanation for so-called quantum randomness in terms of unknown ‘initial conditions’. We also show how Born’s usual formula, for quantum probability, can emerge from the peculiar particle motions predicted by the laws of pilot-wave theory. The chapter ends with a detailed discussion of how pilot-wave theory explains nonlocality, or spooky action at a distance, between widely separated particles.
Black hole evaporation is one of the most striking phenomena at the interface between gravity and quantum physics. In Hawking's semi-classical treatment, where matter is quantum mechanical and the spacetime is definite and classical, evaporation leads to an apparent loss of unitarity of the overall evolution, and to the so-called black hole information paradox. Here, we go beyond this semi-classical treatment and formulate a toy quantum model of black hole evaporation that allows the black hole to evolve into a superposition of being fully evaporated and not fully evaporated, consistent with the Hawking particles being in a coherent superposition of different energy levels. We model Hawking particle production by the repeated action of quantum-controlled unitaries, generating emission from the quantum black hole and accounting for a quantum coherent back-reaction on the black hole matter state. We show that the probability of full annihilation of the black hole matter increases with time until the black hole is, asymptotically, fully evaporated in every branch of the quantum superposition. We prove that under natural assumptions, this evaporation model is unitary, such that the initial state can in principle be recovered from the final asymptotic state of the radiation.
The black hole information paradox arises from an apparent conflict between the Hawk-ing black hole radiation and the fact that time evolution in quantum mechanics is unitary. The trouble is that while the former suggests that information of a system falling into a black hole disappears, the latter implies that information must be con-served. In this work we discuss the current divergence in views regarding the paradox, we evaluate the role that objective collapse theories could play in its resolution and we propose a link between spontaneous collapse events and microscopic virtual black holes. 1
In 1976 Stephen Hawking proposed that information may be lost from our universe as a pure quantum state collapses gravitationally into a black hole, which then evaporates completely into a mixed state of thermal radiation. Although this proposal is controversial, it is tempting to consider analogous processes that might occur in certain theories of consciousness. For example, one might postulate that independent degrees of freedom be ascribed to the mental world to help explain the feeling of a correlation between one's desires and one's choice of actions. If so, one might ask whether information in the physical world can be lost to such postulated degrees of freedom in the mental world. Or, one might hypothesize that the mental world can affect the physical world by modifying the quantum action for the physical world in a coordinate-invariant way (analogous to the alpha parameters in wormhole theory).
I am immensely pleased with this wonderful volume, and humbled by it. It demonstrates the incredible vibrancy of fundamental physics, both theoretical and experimental, as a new century gets under way. Just as unimagined vistas of the physical world were revealed in the early years of the twentieth century, so too we are encountering unimagined wonders a hundred years later. If there is an end to physics, an end to understanding the reasons for existence, it lies far in the future. Who would have guessed in 1925, or even in 1950, that quantum mechanics would remain for so many decades such a fertile field of research? Who would have guessed then that its reason for being would remain mysterious for so long? Like many of the authors in this book, I remain convinced that some deeper reason for quantum mechanics will one day emerge, that eventually we will have an answer to the question, “How come the quantum?” And to the companion question, “How come existence?” And who could have guessed in 1975 – when the black hole was coming to be accepted, when an explanation of pulsars was at hand, when primordial black-body radiation had been identified – who could have guessed then that an incredible confluence of deep thinking and stunning experimental techniques would push our understanding of cosmology – of the beginnings, the history, and the fate of the universe – to its present astonishing state?