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86 of 86 people found the following review helpful
5.0 out of 5 stars
Great Lectures. Requires Math Background.,
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This review is from: Elementary Particles and the Laws of Physics: The 1986 Dirac Memorial Lectures (Paperback)
This short book, Elementary Particles and the Laws of Physics, offers two lectures: Richard Feynman's The Reason for Antiparticles and Steven Weinberg's Toward the Final Laws of Physics. These two talks comprise the 1986 Dirac Memorial lectures at Cambridge University. Both presentations are cogently structured and make fascinating reading.
The talks were directed at an advanced audience, one that was familiar with quantum mechanics. Unlike many popular presentations by Feynman and Weinberg, these lectures are not suitable for the general layman. However, these lectures are accessible to a persistent (perhaps, stubborn) layman with a calculus background and a deep interest in particle physics. I am not a physicist, but I did take my share of physics, chemistry, and math courses several decades ago. I encountered Schrodinger's equation in more than one class, but not relativistic quantum mechanics. However, having recently read Bruce Schumm's wonderful review of particle physics (titled Deep Down Things), I was sufficiently motivated to work my way through both Dirac memorial lectures. Richard Feynman's lecture, The Reason for Antiparticles, is decidedly the more difficult. Feynman first demonstrates that quantum mechanics and relativity together require the existence of antiparticles, and then shows that they also establish the spinstatistics connection. Within a few pages advanced mathematical expressions appear and then persistently stay in the foreground for nearly the entire talk. Although understanding Feynman's mathematics is critical for a full and deep appreciation of his exposition, with careful, repeated readings the stubborn layman will have sudden moments of enlightenment and can come away with a deeper understanding of antiparticles and spin statistics. For readers engaged in some selftutorial readings, it may prove helpful to return occasionally to this classic Feynman lecture to qualitatively measure progress. I have no doubt that, on a deeper level, Feynman's lecture will similarly challenge and enlighten physics majors as well. Steven Weinberg discusses his speculations on the shape of a final underlying theory of particle physics. Initially, his talk is deceptively easy as few mathematical expressions are used. However, about midway a Lagrangian density equation appears, ratcheting the difficulty several notches, as Weinberg considers a theoretical framework based on quantum mechanics and a few symmetry principles, that is also mathematically consistent with the Lagrangian dynamical principle. After discussion of some limitations of the Standard Model, Weinberg concludes his talk with a somewhat mathematical introduction to string theory.
36 of 37 people found the following review helpful
3.0 out of 5 stars
five stars for the lectures, one star for the book,
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This review is from: Elementary Particles and the Laws of Physics: The 1986 Dirac Memorial Lectures (Paperback)
This slender volume comprises the first two Dirac Memorial Lectures, endowed by St. John's College, Cambridge, in honor of one of its most distinguished alumni, Paul Dirac, one of the originators of quantum mechanics, and the first to successfully meld quantum mechanics with special relativity to produce what eventually became quantum field theory and the Standard Model of particle physics. The first lecture is by Richard Feynman, who helped perfect quantum electrodynamics, that portion of quantum field theory dealing with interactions of electrons and photons, the modern view of electricity and magnetism. The second is by Steven Weinberg, who pioneered the unification of electromagnetism with the weak nuclear force, pointing the way towards the Standard Model and beyond to an asyetunrealized dream of a Grand Unified Theory encompassing all of physics including gravity.
The lectures themselves are terrific. This review is focussed on Feynman's lecture, which is the reason I bought the book. The target audience for the Dirac lectures according to Weinberg (page 67) was "undergraduates who have had a first course in quantum mechanics". Such a course would typically not include a lot of the material covered by Feynman. His lecture concerns itself with two very deep topics in quantum electrodynamics: how the inclusion of special relativity predicts antiparticles, and the relationship between a particle's spin and its behavior in aggregates (statistics). Basically, he starts by showing how a simple mathematical theorem requires that if we restrict our analysis of particle interactions to include only particles with positive energies, then particles travelling faster than the speed of light must be included in the analysis. It is then shown that in some reference frames these particles will be seen to travel backwards in time, which can be interpreted as antiparticles. Using a particularly simple particle interaction as an example, he then shows how in order for the probabilities of all the possible variations which must be included in the analysis to add up to one, particles with spin zero (and other whole integer numbers of spin) obey one kind of behavior in groups (BoseEinstein statistics, hence the name bosons), whereas particles with spin 1/2 (and other halfinteger spin numbers) follow a different kind of behavior in groups (Fermi statistics, hence the name fermions). He shows that a particle obeying BoseEinstein statistics enhances the probability of a copy of itself spontaneously appearing, whereas a particle obeying Fermi statistics suppresses the probability of a copy of itself spontaneously appearing. The former behavior leads to a phenomenon called stimulated emission, which is the basis for lasers (not discussed further in this lecture). The latter behavior is the basis of the Pauli exclusion principle, whereby no two electrons can occupy the same state in an atom, which in turn is the basis for the periodic table of the elements and all the phenomena of chemistry. Feynman presupposes that the audience is familiar with the basic mathematical formalisms of quantum mechanics, such as the arithmetic of complex numbers, calculation of amplitudes, and their relation to probability. He also presupposes an acquaintance with special relativity, Minkowski diagrams, etc. He uses ingenious simplifications to make the calculation of the amplitudes and probabilities in his simple example more clear. Which brings me to why I give this book as opposed to the lectures only one star. It's not suitable for the general reader. Yet it masquerades as such. The name Feynman is displayed in large letters across the top, as bait. Look in the science section of any good general bookstore and only four scientists will have any prominence: Darwin, Einstein, Feynman, and Hawking. These are the only four who have achieved significant name recognition with a general audience. Anyone who buys this book thinking they're getting something on the level of "Surely You're Joking" or "Six Easy Pieces" or "QED" will be disappointed. No attempt has been made to add any material which will improve the comprehension for the general reader. Not so much as a simple statement that i times i equals 1, let alone any definition of amplitudes, or their relationship to probability, or what a light cone is, etc., etc. This is a disservice and smacks of exploitation of the Feynman name. Then the publisher uses the trick of shrinking the size of the pages to try to hide the fact that if the book had regularsized pages it would be too thin without supplementary material to look worth the price being charged. Plus, despite having gone through at least 8 printings since first published in 1987, there are still typos! Not trivial ones, either. On page 7, Figure 1 has x1 and x2 labelled backwards. On page 14, Figure 3, the sign of the sum on the left hand side should be positive, not negative. On page 18, line 11 should read "those from Fig 7c, d, and f should cancel", not Fig 7c, d, and e.
42 of 48 people found the following review helpful
5.0 out of 5 stars
Physics by two of the very best!,
By qed100@hotmail.com Mark Martin "Mark Martin" (Bainbridge, Indiana, U.S.A.)  See all my reviews
This review is from: Elementary Particles and the Laws of Physics: The 1986 Dirac Memorial Lectures (Hardcover)
As usual, the best physics books are short and to the point, as is this one. The two Dirac lectures may serve as a perfectly good mini physics course all by themselves. I always enjoy a Feynman lecture, and this is no exception. He cuts to the chase without sacrificing the plot. But, I must say, in this case the Wienberg lecture is the better of the two. Weinberg's style has a particular grace & beauty about it that gently exposes the aesthetic meaning of the search for a picture of nature.
20 of 24 people found the following review helpful
3.0 out of 5 stars
Summary of Paul Dirac Memorial Lectures,
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This review is from: Elementary Particles and the Laws of Physics: The 1986 Dirac Memorial Lectures (Paperback)
This book is a summary of 1986 Paul Dirac memorial lectures delivered by physicists, Richard Feynman and Steven Weinberg. This book requires the knowledge of undergraduate level physics and perturbation theory, and it is described in two chapters; the first is by Feynman under the title "The reason for antiparticle." This section describes the first attempt of Dirac in 1928 to "wed" newly discovered quantum mechanics and theory of relativity. When relativity was included into Schrodinger's pure wave equations, the relativistic equation (Dirac equations) would only be satisfied if there were two solutions corresponding to positive and negative energy states, and in the case of the electron, an electron with a positive charge was required for negative energy state. Thus the existence of antiparticles (positron) was predicted as a direct result of combining the relativity with quantum mechanics. Paul Dirac was also able to explain the origin of the electron magnetic moment and spin. Feynman postulated one of the revolutionary thought in quantum field theory, that antiparticles could be viewed as particles going back in time. This should not be taken as a physical reality in which cause  effect sequence could be revered. Because during the Lorentz transformation the time sequence of two events gets reversed, one of them could not have been the cause of the other because the two events are outside each other's sphere of influence. In frame A, if event 1 occurs first and event 2 occurs after event 1, but in frame B, event 2 occurs before event 1. This is possible in relativity because the time ordering of two events is not an absolute concept; one event can be in the past of another event in one frame, and in its future in a different frame. An observer in frame A will see an electron before event 1, an electron between events 1 and 2, and an electron after event 2, but in frame B, he will see one electron before event 2 and only one electron after event 1.
In the second part under the title, Toward the final laws of physics, Steven Weinberg discusses the developments in physics to explain physical reality with one set of physical laws. This has lead to several unsuccessful theories to unify relativity and quantum physics, finally leading to String theory. Paul Dirac believed that physical laws should have mathematical beauty. Both Feynman and Weinberg have made beautiful theories. Weinberg played a key role in the unification of electricity and magnetism with the weak forces of radioactivity, and Feynamn expanded the understanding of quantum electrodynamics; they were best suited to deliver the Paul Dirac memorial lectures. 1. Paul Dirac: The Man and his Work 2. Paul Adrien Maurice Dirac: Reminiscences about a Great Physicist 3. Dirac: A Scientific Biography 4. Lectures on Quantum Mechanics 5. Surely You're Joking, Mr. Feynman! (Adventures of a Curious Character) 6. Classic Feynman: All the Adventures of a Curious Character 7. Positron Physics (Cambridge Monographs on Atomic, Molecular and Chemical Physics) 8. Dreams of a Final Theory: The Scientist's Search for the Ultimate Laws of Nature 9. QED: The Strange Theory of Light and Matter (Princeton Science Library) 10. Cosmology
7 of 8 people found the following review helpful
5.0 out of 5 stars
Tougher than the Lectures on Physics,
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This review is from: Elementary Particles and the Laws of Physics: The 1986 Dirac Memorial Lectures (Paperback)
When I readThe Feynman Lectures on Physics including Feynman's Tips on Physics: The Definitive and Extended Edition, I was hoping to understand the reasoning behind the exclusion principle, and was disappointed to find that RPF felt that this was too complex for undergraduates, so he asked them to take it on faith for the moment.
Here he is talking to a more advanced audience, and explains it  he was right, it's tough. I'm still struggling to understand it, but I have confidence that this is a good book to help. [Added nearly a year later] Having reread the book several times, I finally understand Feynman's lecture! As is often the case, once I understand the principle, I see relationships to various other things I had not fully understood before. I should also comment on Weinberg's lecture: he's talking about more speculative areas than Feynman, which is perhaps one reason I found him less enlightening than Feynman, but in a rather vague way I follow what he's saying. Certainly these are fascinating ideas, but they don't sing to me like Feynman's lecture.
4 of 4 people found the following review helpful
5.0 out of 5 stars
Great book,
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This review is from: Elementary Particles and the Laws of Physics: The 1986 Dirac Memorial Lectures (Paperback)
Feynman's lecture is the simplest and the most intuitive explanation of the connection between spin and statistics that I have ever seen! This is a very readable book, no knowledge of quantum field theory is required, but a good understanding of relativity and quantum mechanics is essential for understanding the book. I think every physicist should read these lectures, although very simple, they add a lot to our understanding and even to our knowledge of fundamental physics.
2 of 2 people found the following review helpful
4.0 out of 5 stars
Definitely worth readingbut you should temper your expectations somewhat,
By Ulfilas (Washington, DC)  See all my reviews
This review is from: Elementary Particles and the Laws of Physics: The 1986 Dirac Memorial Lectures (Paperback)
Richard Feynman and Steven Weinberg, giants in the world of physics, and especially in quantum field theory, obviously have a great deal to offer. In order to compress or synopsize their thoughts, however, many important concepts must necessarily be glossed over. That said, there is still much to like in these two lectures, with Feynman's entitled "The reason for antiparticles" and Weinberg's "Towards the final laws of physics." Together these two lectures constitute a sort of Alpha and Omega, with Feynman considering the importance of Dirac's prediction of the existence of antiparticles and Weinberg wondering where Dirac's work may ultimately lead us.
I found Feynman's thoughts on antiparticles as equivalent to their counterparts speeding backwards in time to be intuitively engaging. Feynman also takes up the challenge of explaining some aspects of the differences between Fermions and Bosons that generally fall under the aegis of the Spin Statistics Theorem, but I found his treatment of this complex topic unsatisfying. In Feynman's defense, however, I should observe that proofs of the Spin Statistics Theorem are notoriously difficult, with a number of books largely dedicated to this problem (e.g. Pauli and the SpinStatistics Theorem, PCT, Spin and Statistics, and All That). For an in depth discussion of this topic that includes an assessment of Feynman's analysis, go to the Wikipedia link for the Spin Statistics Theorem and download the paper by Duck and Sudarshan. Weinberg's lecture outlines some aspects of quantum physics and quantum field theory, with an eye to the day when particle physics is no longer primarily constrained by the 17 parameters of the Standard Model, such that a new overarching approach, perhaps that promised by String Theory, might neatly unite gravity with the other forces of nature. Certainly Weinberg's hopeful tone is very appealing, as is his sense of an "inevitability" that something truly wonderful awaits us on the theoretical horizon. As he takes the reader on this grand tour, Weinberg makes quite a few interesting observations, including the statement that Lorentz invariance "is almost incompatible with quantum mechanics, so the combination of the two puts tremendous constraints on the form of any kind of dynamical theory." Unlike Feynman, however, Weinberg maintains a respectful distance from any discussion of the Spin Statistics Theorema somewhat ironic turn of events given the fact that Weinberg published extensively on this topic in the mid to late 1960'sand discusses this subject in depth in his book on quantum field theory The Quantum Theory of Fields, Volume 1: Foundations. Perhaps Weinberg, informed by his own extensive experience with the Spin Statistics Theorem, knows that "discretion is the better part of valor." As to the proper audience for these lectures Weinberg states that "I was told in preparing this lecture that it should be pitched at undergraduates who have had a first course in quantum mechanics." This would place the level of these lectures at those students who are beginning their senior year as physics majors. I would agree with this assessment, although even for someone who has taken the standard twosemester graduate quantum physics course these lectures would still be difficult to follow. In part the difficulty lies in the fact that formal mathematical arguments are often easier to follow than intuitive pictorial arguments such as those employed in these lectures.
1 of 1 people found the following review helpful
4.0 out of 5 stars
A fun exciting read,
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This review is from: Elementary Particles and the Laws of Physics: The 1986 Dirac Memorial Lectures (Paperback)
This books is really cool. Its targeted to someone already kinda familiar with physics and Quantum Mechanics but you only need the most basic understanding. The book gives reasonably precise explanations (without too much math) of why antiparticles must exist. Feynman's style is generally quite readable. Overall, I had fun and learned a lot.
I would not recommend this book for someone who has studied quantum mechanics at all however. It assumes you're familiar with a lot of the terminology and concepts.
2 of 3 people found the following review helpful
3.0 out of 5 stars
The Dirac memorial lectures by Feynman and Weinberg,
By Anilao diver (Mabini)  See all my reviews
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This review is from: Elementary Particles and the Laws of Physics: The 1986 Dirac Memorial Lectures (Paperback)
Two topnotch physicists of the mid20th century give here the P.A.M. Dirac memorial lectures.
Professor Dirac of Cambridge University was a major force in the development of quantum physics and particle physics. The lectures are for physicists, and I as lay person did not much benefit from them. I would rather read the excellent books for the layperson by Steven Weinberg, whose clarity of exposition is amazing.
4.0 out of 5 stars
good read,
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This review is from: Elementary Particles and the Laws of Physics (Kindle Edition)
A good book, but a little difficult to understand in some areas for the 'average' guy. It was probably meant to be that way.

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Elementary Particles and the Laws of Physics by Steven Weinberg
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