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The Principles Of Quantum Mechanics 1930 1930 [Hardcover]
eng, Pages 269. Reprinted in 2015 with the help of original edition published long back[1930]. This book is in black & white, Hardcover, sewing binding for longer life with Matt laminated multi-Colour Dust Cover, Printed on high quality Paper, re-sized as per Current standards, professionally processed without changing its contents. As these are old books, there may be some pages which are blur or missing or black spots. If it is multi volume set, then it is only single volume. We expect that you will understand our compulsion in these books. We found this book important for the readers who want to know more about our old treasure so we brought it back to the shelves. (Customisation is possible). Hope you will like it and give your comments and suggestions. Original The Principles Of Quantum Mechanics 1930 1930 [Hardcover], Original P A M Dirac
269 pages, Hardcover
Published January 1, 2015
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About the author
Paul A.M. Dirac
21 books146 followersPaul Adrien Maurice Dirac was an English theoretical physicist who made fundamental contributions to the early development of both quantum mechanics and quantum electrodynamics. He was the Lucasian Professor of Mathematics at the University of Cambridge, a member of the Center for Theoretical Studies, University of Miami, and spent the last decade of his life at Florida State University.
Among other discoveries, he formulated the Dirac equation which describes the behaviour of fermions and predicted the existence of antimatter. Dirac shared the 1933 Nobel Prize in Physics with Erwin Schrödinger "for the discovery of new productive forms of atomic theory". He also made significant contributions to the reconciliation of general relativity with quantum mechanics.
Among other discoveries, he formulated the Dirac equation which describes the behaviour of fermions and predicted the existence of antimatter. Dirac shared the 1933 Nobel Prize in Physics with Erwin Schrödinger "for the discovery of new productive forms of atomic theory". He also made significant contributions to the reconciliation of general relativity with quantum mechanics.
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June 24, 2024
A FAMOUS PRESENTATION OF THE “NEW PHYSICS” (as of 1930)
Paul Adrien Maurice Dirac (1902-1984) was an English theoretical physicist who shared the 1933 Nobel Prize in Physics with Erwin Schrödinger.
He wrote in the Preface to the First Edition (1930) of this book, “The classical tradition … led to a physics whose aim was to make assumptions about the mechanism and forces connecting these observable objects, to account for their behavior in the simplest possible way. It has become increasingly evident in recent times, however, that nature works on a different plan. Her fundamental laws do not govern the world as it appears in our mental picture in any very direct way, but instead they control a substratum of which we cannot form a mental picture without introducing irrelevancies. The formulation of these laws requires the use of the mathematics of transformations… From the mathematical side the approach to the new theories presents no difficulties… For this reason a book on the new physics… must be essentially mathematical… In this book I have tried to keep the physics to the forefront, by beginning with an entirely physical chapter and in the later work examining the physical meaning underlying the formalism wherever possible.”
He explains, “Causality applies only to a system which is left undisturbed. If a system is small, we cannot observe it without producing a serious disturbance and hence we cannot expect to find any causal connection between the results of our observations. Causality will still be assumed to apply to undisturbed systems and the equations which will be set up to describe an undisturbed system will be differential equations expressing a causal connection between conditions at one time and conditions at a later time… There is an unavoidable indeterminacy in the calculation of observational results, the theory enabling us to calculate in general only the probability of our obtaining a particular result when we make an observation.” (Pg. 4)
He notes, “quantum mechanics is able to effect a reconciliation of the wave and corpuscular properties of light. The essential point is the association of each of the transactional states of a photon with one of the wave functions of ordinary wave optics. The nature of this association cannot be pictured on a basis of classical mechanics, but is something entirely new… The association can be interpreted only statistically, the wave function giving us information about the probability of our finding the photon in any particular place when we make an observation of where it is.” (Pg. 9)
He states, “The general principle of superposition of quantum mechanics … requires us to assume that between these states there exist peculiar relationships such that whenever the system is definitely in one state we can consider it as being partly in each of two or more states... The original state must be regarded as the result of a kind of superposition of the two or more new states, in a way that cannot be resolved on classical ideas… The nature of the relationships which the superposition principle requires to exist between the states of any system is of a kind that cannot be explained in terms of familiar physical concepts… There is a entirely new idea involved, to which one must get accustomed and in terms of which one must proceed to build up any exact mathematical theory, without having any detailed classical picture.” (Pg. 12)
He observes, “Most quantum problems … cannot be solved exactly with the present resources of mathematics, as they lead to equations whose solutions cannot be expressed in finite terms with the help of the ordinary functions of analysis… There are two distinct methods in perturbation theory. In one of these the perturbation is considered as causing a modification of the states of motion of the unperturbed system. In the other w do not consider any modification to be made in the states of the unperturbed system, but we suppose that the perturbed system, instead of remaining permanently in ONE of these states, is continually changing from one to another, or making transitions, under the influence of the perturbation. Which method is to be used in any particular case depends on the nature of the problem to be solved.” (Pg. 167)
He says, “we shall investigate problems connected with a particle which, coming from infinity, encounters or ‘collides with’ some atomic system and, after being scattered through a certain angle, goes off to infinity again. The atomic system which does the scattering we shall call … the ‘scatterer.’ … The scatterer is usually assumed to be of infinite mass and to be at rest throughout the scattering process… We must take into account the possibility that the scatterer, considered as a system by itself, may have a number of different stationary states and that if it is initially in one of these states when the particle arrives from infinity, it may be left in a different one when the particle goes off to infinity again. The colliding particle may this induce transitions in the scatterer.” (Pg. 185)
He points out, “If a system in atomic physic contains a number of particles of the same kind, e.g., a number of electrons, the particles are absolutely indistinguishable one from another. No observable change is made when two of them are interchanged. This circumstance gives rise to some curious phenomena in quantum mechanics having no analogue in classical theory, which arise from the fact that in quantum mechanics a transition may occur resulting in merely the interchange of two similar particles, which transition then could not be detected by any observational means.” (Pg. 207)
He concludes, “Quantum mechanics may be defined as the application of equations of motion to atomic particles… The domain of the applicability of the theory is mainly the treatment of electrons and other charged particles interacting with the electromagnetic field---a domain which now includes most of low-energy physics and chemistry. Now there are other kinds of interactions, which are revealed in high-energy physics and are important for the description of atomic nuclei. These interactions are not at present sufficiently well understood to be incorporated into a system of equations of motion… It is to be hoped that with increasing knowledge a way will eventually be found for adapting the high-energy theories into a scheme based on equations of motion, and so unifying them with those of low-energy physics.” (Pg. 312)
This book will be “must reading” for those seriously studying the development of contemporary physics.
Paul Adrien Maurice Dirac (1902-1984) was an English theoretical physicist who shared the 1933 Nobel Prize in Physics with Erwin Schrödinger.
He wrote in the Preface to the First Edition (1930) of this book, “The classical tradition … led to a physics whose aim was to make assumptions about the mechanism and forces connecting these observable objects, to account for their behavior in the simplest possible way. It has become increasingly evident in recent times, however, that nature works on a different plan. Her fundamental laws do not govern the world as it appears in our mental picture in any very direct way, but instead they control a substratum of which we cannot form a mental picture without introducing irrelevancies. The formulation of these laws requires the use of the mathematics of transformations… From the mathematical side the approach to the new theories presents no difficulties… For this reason a book on the new physics… must be essentially mathematical… In this book I have tried to keep the physics to the forefront, by beginning with an entirely physical chapter and in the later work examining the physical meaning underlying the formalism wherever possible.”
He explains, “Causality applies only to a system which is left undisturbed. If a system is small, we cannot observe it without producing a serious disturbance and hence we cannot expect to find any causal connection between the results of our observations. Causality will still be assumed to apply to undisturbed systems and the equations which will be set up to describe an undisturbed system will be differential equations expressing a causal connection between conditions at one time and conditions at a later time… There is an unavoidable indeterminacy in the calculation of observational results, the theory enabling us to calculate in general only the probability of our obtaining a particular result when we make an observation.” (Pg. 4)
He notes, “quantum mechanics is able to effect a reconciliation of the wave and corpuscular properties of light. The essential point is the association of each of the transactional states of a photon with one of the wave functions of ordinary wave optics. The nature of this association cannot be pictured on a basis of classical mechanics, but is something entirely new… The association can be interpreted only statistically, the wave function giving us information about the probability of our finding the photon in any particular place when we make an observation of where it is.” (Pg. 9)
He states, “The general principle of superposition of quantum mechanics … requires us to assume that between these states there exist peculiar relationships such that whenever the system is definitely in one state we can consider it as being partly in each of two or more states... The original state must be regarded as the result of a kind of superposition of the two or more new states, in a way that cannot be resolved on classical ideas… The nature of the relationships which the superposition principle requires to exist between the states of any system is of a kind that cannot be explained in terms of familiar physical concepts… There is a entirely new idea involved, to which one must get accustomed and in terms of which one must proceed to build up any exact mathematical theory, without having any detailed classical picture.” (Pg. 12)
He observes, “Most quantum problems … cannot be solved exactly with the present resources of mathematics, as they lead to equations whose solutions cannot be expressed in finite terms with the help of the ordinary functions of analysis… There are two distinct methods in perturbation theory. In one of these the perturbation is considered as causing a modification of the states of motion of the unperturbed system. In the other w do not consider any modification to be made in the states of the unperturbed system, but we suppose that the perturbed system, instead of remaining permanently in ONE of these states, is continually changing from one to another, or making transitions, under the influence of the perturbation. Which method is to be used in any particular case depends on the nature of the problem to be solved.” (Pg. 167)
He says, “we shall investigate problems connected with a particle which, coming from infinity, encounters or ‘collides with’ some atomic system and, after being scattered through a certain angle, goes off to infinity again. The atomic system which does the scattering we shall call … the ‘scatterer.’ … The scatterer is usually assumed to be of infinite mass and to be at rest throughout the scattering process… We must take into account the possibility that the scatterer, considered as a system by itself, may have a number of different stationary states and that if it is initially in one of these states when the particle arrives from infinity, it may be left in a different one when the particle goes off to infinity again. The colliding particle may this induce transitions in the scatterer.” (Pg. 185)
He points out, “If a system in atomic physic contains a number of particles of the same kind, e.g., a number of electrons, the particles are absolutely indistinguishable one from another. No observable change is made when two of them are interchanged. This circumstance gives rise to some curious phenomena in quantum mechanics having no analogue in classical theory, which arise from the fact that in quantum mechanics a transition may occur resulting in merely the interchange of two similar particles, which transition then could not be detected by any observational means.” (Pg. 207)
He concludes, “Quantum mechanics may be defined as the application of equations of motion to atomic particles… The domain of the applicability of the theory is mainly the treatment of electrons and other charged particles interacting with the electromagnetic field---a domain which now includes most of low-energy physics and chemistry. Now there are other kinds of interactions, which are revealed in high-energy physics and are important for the description of atomic nuclei. These interactions are not at present sufficiently well understood to be incorporated into a system of equations of motion… It is to be hoped that with increasing knowledge a way will eventually be found for adapting the high-energy theories into a scheme based on equations of motion, and so unifying them with those of low-energy physics.” (Pg. 312)
This book will be “must reading” for those seriously studying the development of contemporary physics.
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