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DVD Editorial Reviews From Publishers Weekly The concept of additional spatial dimensions is as far from intuitive as any idea can be. Indeed, although Harvard physicist Randall does a very nice job of explaining--often deftly through the use of creative analogies--how our universe may have many unseen dimensions, readers' heads are likely to be swimming by the end of the book. Randall works hard to make her astoundingly complex material understandable, providing a great deal of background for recent advances in string and supersymmetry theory. As coauthor of the two most important scientific papers on this topic, she's ideally suited to popularize the idea. What is absolutely clear is that physicists simply do not yet know if there are extra dimensions a fraction of a millimeter in size, dimensions of infinite size or only the dimensions we see. What's also clear is that the large hadron collider, the world's most powerful tool for studying subatomic particles, is likely to provide information permitting scientists to differentiate among these ideas soon after it begins operation in Switzerland in 2007. Randall brings much of the excitement of her field to life as she describes her quest to understand the structure of the universe. Copyright Reed Business Information, a division of Reed Elsevier Inc.
See all Editorial Reviews Product Details * Hardcover: 512 pages * Publisher: Ecco (August 30, 2005) * Language: English * ISBN: 0060531088 * Product Dimensions: 93 x 64 x 15 inches * Shipping Weight: 18 pounds.
learn more) First Sentence: The word "dimension," like so many words that describe space or motion through it, has many interpretations-and by now I think I've heard them all.
Lisa Randall's new book, Warped Passages, is a grand tour of some of the most important recent developments in high-energy physics. The book is intended for a popular audience, but is also a very interesting read for anybody with a background in theoretical physics (like myself). The first part contains an overview of modern physics - Einstein's theories of relativity, quantum mechanics and the Standard Model of particle physics. The last part concentrates on the idea of extra dimensions beyond the standard four we know about, which can be motivated by string theory and its discovery of the so-called D-branes. Specifically, she explains the work, pioneered by herself, Raman Sundrum and others, on the so-called "braneworld scenarios". Basically, this is the idea that our four dimensional space-time is embedded in some higher dimensional space, usually called the "bulk". You might think, that extra dimensions are just part of a set of crazy ideas? You should know, that the idea of extra dimensions is actually not at all new. Already in 1884, the original book, "Flatland: A Romance of Many Dimensions" (written by the English mathematician Edwin Abbott) described a world of two-dimensional beings, who only have indirect knowledge of the extra third space-dimension. But, from a mathematical point of view, one can imagine as many dimensions as one wants to. In physics, there are basically two distinct ways in which one can add extra dimensions to our four-dimensional universe. Already in the 1920's, Klein suggested that our universe is five-dimensional, where the extra dimension is rolled up in a circle, which is so tiny, that the universe looks four-dimensional at long enough distance-scales. The motivation was to give a unified geometrical description of electromagnetism and gravitation using Einstein's general theory of relativity. Today we know, that there are other forces which should be included in a unified theory: namely the weak and strong nuclear forces. Presently there is only one theory which can possibly do the work, and this is string theory. Perturbative string theory tells us, that our space-time is ten-dimensional, and that the extra six dimensions should be rolled up in a small but complicated shape (which is determined by some mathematical restrictions). Another way to achieve hidden extra dimensions of space is to suppose, that all normal matter, as well as the light by which we see the world, is confined to a four-dimensional "brane" embedded in a five-dimensional "bulk" - or larger universe. These so-called braneworld theories are the ones of Lisa Randall, Raman Sundrum and others. Warped Passages explains - in excellent style - the logic behind these seemingly fancy ideas. What I particularly liked about the first part of this book is how Prof. As Randall writes, "we are not physiologically equipped to envision more than three dimensions of space", so it might be difficult for the general reader to comprehend this idea. Randall also explains, readers need not imagine a dimension only in spatial terms. Here is an example from the book: If you are buying a house, the factors you might consider include its location (specified by three numbers), price (one number), size (one number), and possibly many other things. So, the number of dimensions in your house search simply equals "the number of quantities you find worth investigating". Randall describes in the last part is - in more technical terms - her work with Raman Sundrum on solving the flavor-changing problem, the gaugino mass problem (and other things) that occur in supersymmetric models with the supersymmetry breaking sector on another brane, separated from ours, or in the bulk; the Randall-Sundrum warped geometry with two branes (a so-called "weak-brane", where we are supposed to live, and a "gravity-brane") and the Randall-Sundrum warped geometry with an infinite extra dimension, using so-called AdS geometry. The main point guiding Randall's research - described in the last part of the book - is the fact that gravity is such a profoundly weak force. Indeed, gravity is the puniest of the fundamental forces governing the matter in the universe, by a huge margin (typically a 10^36 times weaker than the electromagnetic force between two charged particles). Randall suggests, is because we live in a universe containing at least one extra dimension beyond those we can perceive. And gravity is weak because it has been "diluted" into this extra space. Randall's original models are not inherently string-theoretical; it is just that her models have an elegant and simple interpretation in string theory. So you don't need to know *anything* about string theory to understand this book). The breakthrough research by Randall and Sundrum proposed that gravity's dilution can be explained in terms of a cosmic configuration featuring two branes - or two infinite planes, separated by a higher dimensional bulk space. Roughly speaking, the "center of gravity" is on the "gravity-brane" - and some gravity leaks out of this brane, through the bulk, and onto the other brane, usually called the "weak-brane", which is where we live, and which contain the Standard Model fields. Later on, Randall and Sundrum found, that their concept is also theoretically consistent with a configuration which includes only one brane. Usually, one would think that Newton's 1/r^2 law of gravitation implies that there are four and only four non-compact dimensions of infinite extend. The fact that branes are an important part of modern string theory meant that string theorists took an early interest in the Randall-Sundrum models. Randall's research did not directly challenge string theory models, the string theory community actually accepted and recognized the profound significance of her work very early on. One of the long outstanding problems of the Standard Model of particle physics, that braneworlds do provide an interesting answer for, is the "hierarchy problem", or why the weak and Planck scales are so disparate (10^2 GeV compared with 10^19 GeV). In these scenarios, the fundamental gravitational scale is not the Planck scale, but something closer to the weak scale. The conjecture is that gravity is not weak because the Planck scale is so large, but because braneworlds provide various geometrical mechanisms for making the gravitational force much weaker than the others. All this would of course be pointless speculation unless the...
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