This book is a survey of the range of apparently miraculous accidents of nature that have enabled the universe to evolve its familiar structures (atoms, stars, galaxies, and life itself) concludes with an investigation of the so-called anthropic principle.
Recent advances in string theory and inﬂationary cosmology have led to a surge of interest in the possible existence of an ensemble of cosmic regions, or “universes”, among the members of which key physical parameters, such as the masses of elementary particles and the coupling constants, might assume diﬀerent values. The observed values in our cosmic region are then attributed to an observer selection eﬀect (the so-called anthropic principle). The assemblage of universes has been dubbed “the multiverse”. In this paper (...) we review the multiverse concept and the criticisms that have been advanced against it on both scientiﬁc and philosophical grounds. (shrink)
In this sweeping survey, acclaimed science writers Paul Davies and John Gribbin provide a complete overview of advances in the study of physics that have revolutionized modern science. From the weird world of quarks and the theory of relativity to the latest ideas about the birth of the cosmos, the authors find evidence for a massive paradigm shift. Developments in the studies of black holes, cosmic strings, solitons, and chaos theory challenge commonsense concepts of space, time, and matter, and demand (...) a radically altered and more fully unified view of the universe. (shrink)
The generalized second law of thermodynamics states that entropy always increases when all event horizons are attributed with an entropy proportional to their area. We test the generalized second law by investigating the change in entropy when dust, radiation and black holes cross a cosmological event horizon. We generalize for ﬂat, open and closed Friedmann–Robertson–Walker universes by using numerical calculations to determine the cosmological horizon evolution. In most cases, the loss of entropy from within the cosmological horizon is more than (...) balanced by an increase in cosmological event horizon entropy, maintaining the validity of the generalized second law of thermodynamics. However, an intriguing set of open universe models shows an apparent entropy decrease when black holes disappear over the cosmological event horizon. We anticipate that this apparent violation of the generalized second law will disappear when solutions are available for black holes embedded in arbitrary backgrounds. (shrink)
Paul Davies explains the significance of the amazing quantum universe, where fact is stranger than any science fiction. He takes us into a world where commonsense notions of space, time, and causality must be left behind as the realm of solid matter dissolves into vibrating patterns of ghostly energy, and where mind and matter are interwoven in a subtle and holistic manner. An Australian physicist and author of GOD AND THE NEW PHYSICS, Davies writes for the lay reader in simple (...) language. (shrink)
We study the response of a uniformly accelerated model particle detector in a spacetime with compact spatial sections. The basic thermal character of the response re-emerges, in spite of the fact that the spacetime does not possess event horizons. Our model also permits a study of detector response to twisted field states.
The massless Thirring model of a self-interacting ferinion field in a curved two-dimensional background spacetime is considered. The exact operator solution for the fields and the equation for the two-point function are given and used to examine the radiation emitted by a two-dimensional black hole. The radiation is found to be thermal in nature, confirming general predictions to this effect. We compute the particle spectrum of the Thirring fermions at finite temperature in Minkowski space and point out errors in a (...) previous attempt at this calculation. Finally we calculate the vacuum expectation value of the stress tensor in an arbitrary two-dimensional spacetime by exploiting the connection between the thermal Hawking radiation from a black hole and the value of the so-called conformal trace anomaly. The latter is also computed quite independently, using dimensional regularization, from general considerations of the renormalization group. (shrink)
of a logarithmic time dependence of the fine structure constant is apparently within the limits discussed if there is a corresponding logarithmic time dependence of the strong coupling constant also. Moreover the recent discover> of naturally occurring ' Pu places the Gamow hypothesis of e' r much nearer the allov'able limits than had previously been supposed.
It is widely accepted that EinstcinRi7;s general theory of relativity is an satisfactory description of gravity 0nly in the macroscopic limit, where quantum eiTcc1;s may be neglected. Presumably this theory is inapplicable at the Planck length, but recently much attention has been devoted to gravitational theory at intermediate length scales where quantum affects 0f matter are inescapable, but where there is an general assumption that the gravitational Held may bc treated as a classical background, augmented if necessary by quamtizcd linearized (...) pertur-. (shrink)
The hypothesis that life’s rapid appearance on Earth justifies the belief that life is widespread in the universe has been investigated mathematically by Lineweaver and Davis (Astrobiol- ogy 2002;2:293–304). However, a rapid appearance could also be interpreted as evidence for a nonterrestrial origin. I attempt to quantify the relative probabilities for a non-indigenous ver- sus indigenous origin, on the assumption that biogenesis involves one or more highly im- probable steps, using a generalization of Carter’s well-known observer-selection argument. The analysis is (...) specifically applied to a Martian origin of life, with subsequent transfer to Earth within impact ejecta. My main result is that the relatively greater probability of a Mar- tian origin rises sharply as a function of the number of difficult steps involved in biogene- sis. The actual numerical factor depends on what is assumed about conditions on early Mars, but for a wide range of assumptions a Martian origin of life is decisively favored. By con- trast, an extrasolar origin seems unlikely using the same analysis. These results complement those of Lineweaver and Davis. Key Words: Origin of life—Mars—Probability theory— Carter—Transpermia. Astrobiology 3, 673–679. (shrink)
We discuss the Starobinskii-Unruh process for the Kerr black hole. We show how this effect is related to the theory of squeezed states. We then consider a simple model for a highly relativistic rotating star and show that the Starobinskii-Unruh effect is absent.
The Unruh-Wald scenario for mining quantum black holes is applied to de Sitter space. The following questions are addressed: Will the generalized second law of thermodynamics be maintained for de Sitter horizons? Does the mining process allow the recovery of unlimited energy from the cosmological gravitational field? The evaporation of a black hole in de Sitter space is also investigated in the context of the second law.
Using a model quantum clock, I evaluate an expression for the time of a nonrelativistic quantum particle to transit a piecewise geodesic path in a background gravitational ﬁeld with small spacetime curvature (gravity gradient), in the case that the apparatus is in free fall. This calculation complements and extends an earlier one (Davies 2004) in which the apparatus is ﬁxed to the surface of the Earth. The result conﬁrms that, for particle velocities not too low, the quantum and classical transit (...) times coincide, in conformity with the principle of equivalence. I also calculate the quantum corrections to the transit time when the de Broglie wavelengths are long enough to probe the spacetime curvature. The results are compared with the calculation of Chiao and Speliotopoulos (2003), who propose an experiment to measure the foregoing effects. (shrink)
two dimensions, quantum radiation production is incompatible with a conserved and traceless Tâ,. We therefore resolve an ambiguity in our expression for Trâ, regularized by a geodesic point-separation procedure.
Inconsistencies in the usual interpretation of the absorber theory of radiation are exposed which invalidate an experiment proposed recently by Heron and Pegg. An earlier experiment by Partridge necessarily gave a null result owing to absorption on the far side of the Earth of any advanced radiation which may have been present.
The ﬁne structure constant α ≡ e2/ c ≈ 1/137 is one of the fundamental parameters of the standard model of particle physics. There is a long history of attempts to derive the measured value of α from an underlying theory, or exhibit it in the form of a compact mathematical expression [2–4, 6, 8, 14–16]. The most signiﬁcant advance in this endeavour was made by Dirac, who showed that if magnetic monopoles exist, with magnetic charge μ, then..
Weak measurements offer new insights into the behavior of quantum systems. Combined with post-selection, quantum mechanics predicts a range of new experimentally testable phenomena. In this paper I consider weak measurements performed on time-dependent pre- and post-selected ensembles, with emphasis on the decay of excited states. The results show that the standard exponential decay law is a limiting case of a more general law that depends on both the time of post-selection and the choice of final state. The generalized law (...) is illustrated for two interesting choices of post-selection. (shrink)
An analogue of Hawking's black hole area theorem is proved for Friedmann-type cosmological models with event horizons. The generalised second law of thermodynamics is investigated in cases where the horizon shrinks.