# Book Review УDID TIME BEGIN WILL TIME END Maybe the Big Bang Never OccurredФ Paul H.

код для вставкиСкачатьAnn. Phys. (Berlin) 522, No. 8, 608 – 610 (2010) / DOI 10.1002/andp.201010459 Book Review “DID TIME BEGIN? WILL TIME END? Maybe the Big Bang Never Occurred” by Paul H. Frampton, World Scientific, Singapore (2009), ISBN: 978-981-4280-58-7, 116 pages, USD 28.00 Friedemann Queisser∗ Institut für Theoretische Physik, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany Published online: 28 June 2010 The knowledge of our universe has increased rapidly during the last decades. Therefore it is important that not only the scientific community is enabled to learn about the modern world view. Rather the progress of research in cosmology should be also accessible to a broad public. This is of course not a trivial task since many conclusions that lead to the modern world view are not easily accessible. When I read the blurb of Frampton’s “Did time begin, will time end?”, I was very curious about a book that sought to provide twenty-first century knowledge about cosmology in a simple and comprehensible form. Moreover, I wanted to learn about the cyclic model of the universe that is presented in the book. Frampton begins with an explanation of cosmic distances starting from everyday length scales. Thereafter follows a brief explanation of the cornerstones in modern cosmology. Within the first chapter the reader is confronted with Hubble’s law and cosmological red shift, the Big Bang and steady state theory, the cosmological principle and topological issues related to the low multipoles in the cosmic microwave background radiation (CMB), quantum gravity, cosmological singularities and inflation. Although this is certainly a good overview on the subject, it might be too advanced for a reader who has never heard of these issues before. Fortunately in the subsequent chapters many of those crucial points are discussed more thoroughly. The author turns to the large scale structure of the universe which can be related to quantum physics during inflation. Quantum fluctuations in the early universe provide a possible explanation for the observed structures in the universe. For this purpose the author introduces briefly the concepts of quantum mechanics and quantum field theory. Frampton explains in detail the horizon problem and its solution by means of the theory of inflation. Especially the role of the cosmic microwave background radiation, which supports an inflationary period, is highlighted. One is confronted with a lot of technical terms and issues concerning the standard model of particle physics, which are required for a deeper understanding though not necessary for a first understanding of the subject. In order to complete the so-called concordance model of cosmology, the author addresses the great mysteries of cosmology: dark matter and dark energy. The dark matter problem leads naturally to the supersymmetric extensions of the standard model and dark matter candidates like neutralinos and axions. Frampton combines this theoretical topic with the question of how to detect these particles. At the end of this section he focusses on the seventy-two percent of energy that are uniformly distributed in the universe and known as dark energy. Since the experimental verification of a theory is of great importance, Frampton dedicates one chapter to the cornerstones of experimental cosmology that support the well-established concordance model. The author discusses the observations of supernovae of Type 1A, the detection of acoustic peaks in the CMB ∗ E-mail: fsq@thp.uni-koeln.de c 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Ann. Phys. (Berlin) 522, No. 8 (2010) 609 spectrum and the large scale galaxy survey leading in the end to the knowledge of the the energy distribution in the universe. In chapter six Frampton turns to his central concern: The future of the universe and whether time has a beginning and an end. Since the dark energy equation of state that determines the future of the universe is unknown so far, there is plenty of room for model building and speculations. Though a certain knowledge of the state parameter and our universe’s fate is experimentally not deducible, Frampton hopes for a more definite theory of quantum gravity that could predict the future. Unfortunately, he takes only string theory to be a serious candidate of quantum gravity throughout the whole book and does not mention other approaches like canonical quantum gravity or loop quantum gravity. In the following, I will address Framptons somewhat far-fetched speculations on cyclic cosmologies. The author concentrates on a state parameter for the cosmological constant below minus one which is in agreement with observations. (However, a state parameter larger than or exactly equal to minus one seems to be equally possible). With this choice, the scale factor of the universe becomes infinite at a finite time due to an unbounded growth of the dark energy density. This scenario is called the Big Rip singularity [1] and can be seen as counterpart of the Big Bang singularity. The author states that those singularities can be avoided by a model that was conceived by himself and one of his students [2]: A cyclic model with no beginning and no end. Framptons cyclic universe contains a finite minimal scale factor for the bounce and a finite maximal scale factor for the turnaround that is achieved by introducing a non-standard term in the Friedmann equation. Such a correction term can be motivated from braneworld scenarios [3]. Additionally one needs to solve an entropy problem. Since the entropy is always increasing due to the second law of thermodynamics, entropy will increase from cycle to cycle. Thus, extrapolation into the past will lead again to an initial singularity which was already understood by Tolman [4]. How does Frampton solve this problem? He states that the universe disintegrates at turnaround into more than 10103 disjoint and causal patches. A single causal patch contains only a few number of photons and has entropy which is roughly equal to zero. Afterwards, each causal patch contracts until the dark energy density reaches some critical value and the next cycle of cosmic evolution starts with an inflationary period. Of course, Framptons scenario of a cyclic cosmology is highly speculative and creates severe problems as already noted by Zhang [5]. Although the scale factor of the universe is always a smooth function of time, the author states on page 96: “At a time somewhat later than the unbinding of a system, the bound components become causally disconnected, meaning that they cannot communicate even at the speed of light before the universe ends. Eventually we may regard the universe itself as disintegrating into a huge number > 10103 of causal patches which are disjoint and separate. The idea now is to delay the brane induced turnaround until a trillion trillionth of a second or less before the would be Rip.” The consequence of this delay, though ignored by the author, is the reentering of all modes that have left the horizon. Zhang noticed correctly that a similar scenario is the inflationary period in the early universe: scales on which causal physics took place left the horizon during inflation and reentered later. (This explains the observed thermalization of the cosmic microwave background radiation.) Since the scale factor of the cyclic universe is always a smooth function, a shrinking to an effective scale factor â = f a, with f < 10−28 (see [2]) and the number of causal patches (see [6]) cannot be deduced from the model. Frampton finishes with the statement that a cyclic universe is the most likely scenario. The origin of this conviction remains a trade secret. Apart from the last two chapters, Frampton’s book is more or less a summary of different topics in cosmology. Due to the significant accumulation of technical words, I would not recommend it to readers that are completely unfamiliar with this subject. For readers having some previous knowledge of modern cosmology, the condensed explanations might be far from satisfactory. www.ann-phys.org c 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 610 F. Queisser: Book Review References [1] R. R. Caldwell, Phys. Lett. B 545, 23 (2002); R. R. Caldwell, M. Kamionkowski, and N. N. Weinberg, Phys. Rev. Lett. 91, 071301 (2003). [2] L. Baum and P. H. Frampton, Phys. Rev. Lett. 98, 071301 (2007). [3] Y. Shtanov and V. Sahni, Phys. Lett. B 557, 1 (2003). [4] R. C. Tolman, Phys. Rev. 38, 1758 (1931). [5] X. Zhang, Eur. Phys. J. C 59, 755 (2009). [6] L. Baum, P. H. Frampton, and S. Matsuzaki, J. Cosmology Astropart. Phys. (JCAP) 0804, 032 (2008). c 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.ann-phys.org

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