Customer Reviews

The Little Book of String Theory (Science Essentials)

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I quite enjoyed Dr. Gubser's effort to explain in words what can only make sense in higher mathematics. Cutting edge physics is, in this layperson's opinion, a mess of theories premised on ideas that nobody has even begun to figure out how to prove. The author effectively uses simile and metaphor to illustrate an exceptionally difficult topic. As an attorney whose scientific quest came to a crashing halt in second semester Calculus, I think I understood his argument that modern physics is like pre-Mendeleevian chemistry. We are finding all manner of new particles and ideas regarding their relationships and interactions but have not yet found a framework to make sense of the new discoveries as did the Periodic Table of Elements to chemistry. Now, that idea I can understand; not since Dr. Michio Kaku's book on Hyperspace have I encountered an author who is both willing and able to bring such thorny ideas into focus.

If you pick up this book and think you'll even begin to understand string theory--try again. However, my understanding of the field advanced more from this book than from any of the other general science offerings out there. While challenging, it was much easier to read and to understand than any textbook or scientific paper. I believe that anyone who truly masters a field of understanding can teach it to anyone else--the ability to teach is a measure of the teacher's understanding. I sympathize with those who say that the field cannot be taught without equations; however, that should not prevent the physicists from making an attempt to do so and I felt that Dr. Gubser succeeded admirably in breaking some new ground with this book.

That said, it can always be done better and if we ever hope to redirect the youth of tomorrow away from JDs and MBAs into a life of discovery that can truly make a difference, then readers should wholeheartedly endorse general science offerings such as this Little Book of String Theory. Rather than quibble about whether the book should have gone for depth over breadth, whether it should have attempted more mathematical explanations--I hope that more physicists and publishers will take up the challenge.

I like to imagine a world where gravity was as understood and as easy to manipulate as electricity--they are both forces that mystified observers before yielding secrets to the scientists, we just have to keep exploring and that was the spirit I choose to take from this wonderful little book.

This book starts with a brief introduction to the basic laws of physics, and the search for an ultimate theory to explain the physical reality. When the author starts describing the string theory, things get complicated. The reader must bear in mind that this is not an easy field to appreciate since it involves multi-dimensions of space and one time dimension; string theory has 26 dimensions, and superstring theory has 10 dimensions. Besides this, the fundamental particles exist as different vibrations of strings in multi spacetime. It is hard to envision how a four dimensional space would look like, and it would be even harder to appreciate the subject given the amount of mathematics that goes into constructing the theory. Although the book doesn't involve any mathematics but the author does his best to make the difficult subject interesting.

A brief summary of the book is as follows: In string theory, the myriad of fundamental particle types is replaced by a single fundamental building block, a string. These strings can be closed, like loops, or open, like a hair. A string is infinitely thin and has an infinitesimal length of 10e(-34) meters. As the string moves through time it traces out a tube or a sheet (the two-dimensional string worldsheet). Furthermore, the string is free to vibrate, and different vibrational modes of the string represent the different particle types. The particles known in nature are classified according to their spin into bosons (integer spin) or fermions (odd half integer spin). The bosons carry forces, for example, the photon carries electromagnetic force; the gluon carries the strong nuclear force, and the graviton carries gravitational force. Fermions make up the matter like the electron or the quark. The string theory described bosons, it does not describe fermions. By introducing supersymmetry to string theory, we can obtain a new theory that describes both bosons and fermions: This is the theory of superstrings. This theory requires that there must be a special kind of symmetry called supersymmetry, which means for every boson (particle that transmits a force) there is a corresponding fermion (particle that makes up matter). But the problem with this theory is that there are five different superstring theories that display no mathematical inconsistencies and seem to explain bosons and fermions. It turns out that these five are different aspects of one single theory called M theory. This theory is also viewed as an 11 dimensional theory that looks 10 dimensions in spacetime, and propose a membrane as opposed to a string as the fundamental building block. The 11th dimension of the string expands infinitely into a floating membrane. According to this theory, our universe exists on a floating membrane, along with infinite parallel universes on their own membranes. Calculations also suggest that gravity might "leak" into our membrane from another nearby membrane. Thus, accounting for its relatively weak force in comparison to the other three forces (weak nuclear force, strong nuclear force, and electromagnetic force.) One would like to question how could a superstring theory with ten spacetime dimensions turn into a supergravity theory with eleven spacetime dimensions? The duality relations between two superstring quantities relate very different theories; they equate large distance of one theory with small distance of another theory, and exchange strong coupling of one theory with weak coupling of another theory. This seems to suggest that there is another fundamental theory lurking behind this mystery that holds the key for physical reality. Another interesting feature is the compactification of six spaces (out of nine) to allow three spatial dimensions of our world, also lead to the generation of all the known particles of matter.

The author notes three existing problems in physics by M theory; the tension in merging gravity and quantum physics; how strings vibrate and move in spacetime; and the evolution of spacetime from mathematical descriptions of strings. The greatest difficulties in unifying general relativity and quantum physics are due to the concept of renormalizabilty. When an electron is probed very close to it by an electric field, it splits into an electron and positron and a photon. The process multiplies due to its quantum physical uncertainties, and continues to form more photons and a cloud of progeny (virtual particles). The amazing thing is that you can keep track of this multiplicity of particles through renormalization, a mathematical method that tracks them all. The process also reduces (normalizes) the infinite mass and infinite charge of the electron (in the above picture) to its characteristic charge and mass. The trouble with gravitons is that you can't renormalize the cloud of virtual gravitons that surround them. For instance, quantum physical calculation of the force between two gravitons becomes infinite. But unlike particles, strings also respond to one another like gravitons, but they do not form a cloud of virtual particles. This is because the particle interactions occur at a single point of spacetime (at zero distance between the interacting particles) leading to infinities. In string theory, the strings collide over a small but finite distance, and the string breaks smoothly over a distance. Thus we can combine quantum mechanics and gravity, and string excitation that carries the gravitational force with minimal problems.

Another interesting concept that emerges from superstring-graviton discussion is the concept of spacetime itself. Although the superstring theory predicts gravitons from flat spacetime physics (classical physics) alone, but string theory also predicts the Einstein equation will be obeyed by a curved spacetime in which strings propagate. Actually the theory adds an infinite series of corrections to the theory of gravity. At distance scales much larger than a string, these corrections are small. But as the distance scale gets smaller, these corrections become larger until the Einstein equation no longer adequately describes the result. This illustrates that the spacetime is not fundamental according to superstring theory, but it emerges only at large distance scales or weak coupling. This has a far reaching philosophical implication about the nature of physical reality as we understand from our interaction with spacetime and matter.

1. The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory
2. The Shape of Inner Space: String Theory and the Geometry of the Universe's Hidden Dimensions
3. String Theory and M-Theory: A Modern Introduction

I bought this book a long time ago and I can still remember things from it during casual conversations. I sound so smart! hahaha. But really, this is a great book for anyone that wants to learn about String Theory.

"One of my resolutions is before I die to be able to have a general understanding of relativity, cosmology and related topics. This book was highly recommended to me in understanding string theory.....I was told by someone with no science background that she understood after reading this. Stay tuned!

Well, not exactly! Professor Gubser does a spectacular job of introducing the concepts of strings, and "branes" (multidimensional surfaces), as well as explaining the concept of the black hole, which is one of the few constructs in all of this that I do understand. The friend who told me that I would "understand" string theory after reading this book was wrong....I have a better understanding of the concept.

What I, and I suspect many others who are fascinated but somewhat learning disabled in these areas need is a book with some basic explanations, e.g.:

1) If you have an 11 dimensional "thing" and we can only understand 4 dimensions (including time), what are the other 7 dimensions? Are they mathematical constructs which we cannot visualize?

2) We need a concise definition and way to conceive of "spacetime". This is truly right brain "stuff" and while we understand time and space, I don't understand how they are one continuum. I THINKI am beginning to understand the relationship between time and the speed of light, but I need a lot more basics in this area.

3) In regard to string theory, I have heard it said elsewhere that all subatomic particles are strings. Prof. Gubser seems to make this point as well, but I don't feel that he does a great job of the big picture, i.e. what is the role of strings and branes in our world......where are they, is all matter made up of them, are they connected, etc.

The book was valuable as it is well written and very understandable in parts on an unbelievably complex topic. I need the companion volume with all the answers to the questions that he raises.

My "bucket list" item to understand this stuff before I die continues!

Recommendations, anyone????????" (Updated 1 second ago)

"If you pick up this book and think you'll even begin to understand string theory--try again." another reviewer wrote. I agree completely.

I slogged through this book and kept waiting for clear simple explanations, but there were none. In fairness such explanations probably don't exist. But it was disappointing to find that I was more confused by the end of the book than before I started it.

Perhaps someone someday may be able to explain string theory in understandable terms, but this book doesn't do it.

If you are a student in the field then this book may suffice as a review for you. If not, don't bother.

..have passed since the beginning of strings science. The book presents the recent state of mathematical calculations and related speculations about strings, branes and extra dimensions. I truly find a hard time to rate this brave and appreciated attempt by the author. Is it well written? - yes. Is it interesting? - not that much.
The main point is that we are still in the dark, nothing is confirmed 100%. All what we have is just mathematics. Even old "twistor" idea from Roger Penrose, that ignited the latest superstring revolution in 1997 (unfortunately not covered in this book; but twistorians came up with a new alternative strategy capturing symmetries that Feynman's approach does not)did not help. The more calculations, the more questions and uncertaities. Reader will encounter numerous new definitions and nomenclature: relativistic strings, worldsheet string theory, M-theory, IIA/IIB-theories, T- dualities, gauge/string dualitiy, D-branes, solitonic branes,"gauge"-measurements and symmetry, bosonic and fermionic dimensions... just to mention a few. Almost every chapter contains assurance: "this or that" is not well understood or mysterious.
Yet..I finished reading this book. IMO it is a good text for college students who would like to study mathematics and particle physics. Or..it is for absolutely crazy about science and cosmology people, like myself. If you are not one of them, skip it.

The encomiums on the back of the dust jacket seemed just too good to believe. So
I opened the book with great expectations which were rapidly dashed.
This 'little' book should either be even smaller or much larger to meet its
objective. String theories abound, all filled with 5. 9, 10, and 20+dimensions,
dualities, odd and even branes, and more esoteric entities in densely packed text.
Frequently, "as I explained in chapter x, y, or z" is used to reorient the confused reader....well?
How does one rate this: 1 for effort, 5 for results