Among the finest, most comprehensive treatments of theoretical physics ever written, this classic volume comprises a superb introduction to the main branches of. Oct 12, Theoretical physics. by: Joos, Georg, urn:acs6: theoreticalphysi00joos:epub:7a1dcdfefc Dec 31, Publication date: Topics: NATURAL SCIENCES, Physics, Fluid mechanics in general. Mechanics of liquids (hydromechanics). Publisher.

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Editorial Reviews. Language Notes. Text: English, German (translation). About the Author. JOHN FREEMAN is an award-winning writer and book critic who has . Jan 6, Theoretical Physics (Dover Books on Physics) 3rd Revised ed. Edition Among the finest, most comprehensive treatments of theoretical physics. Among the finest, most comprehensive treatments of theoretical physics ever written, this classic volume comprises a superb ePUB (mobile friendly). Book info.

Marder Michael P. Maugin Gerard A. Narlikar Jayant V. Neuenschwander Dwight E.

Quantum physics meets biology

Notaros Branislav M. Okhotnikov Oleg G. Pandhamaban T. Rai Choudhuri A. Rand Stephen C. Sattler Klaus D. Full 7 volume set: ISBN Schommers W. Smith Walter F. Stacey W. Story Troy, iUniverse Trefil J. Ulaby Fawwaz T.

Wulfman Carl E. Young Donald F. Zee A.

Theoretical Physics

Zuckerman DanielM. Year Auletta G. Bacciagaluppi G. Baker G. Barnett Stephen M. Becker W. Quantum physics, on the other hand, was initially centered on microscopic phenomena with photons, electrons, and atoms. But objects of increasing complexity have attracted a growing scientific interest, and since the size scales of both physics and the life sciences have approached each other, it is now very natural to ask: what is the role of quantum physics in and for biology?

He anticipated a molecular basis for human heredity, which was later confirmed to be the DNA molecule Watson and Crick, Since the early days of quantum physics, its influence on biology has always been present in a reductionist sense: quantum physics and electrodynamics shape all molecules and thus determine molecular recognition, the workings of proteins, and DNA. Also van der Waals forces, discrete molecular orbitals, and the stability of matter: all this is quantum physics and a natural basis for life and everything we see.

But even years after its development, quantum physics is still a conceptually challenging model of nature: it is often acclaimed to be the most precisely verified theory of nature and yet its common interpretation stands in discrepancy to our classical, i. Is there a transition between quantum physics and our everyday world? And how will the life sciences then fit into the picture—with objects covering anything from molecules up to elephants, mammoth trees, or the human brain?

Still half a century ago, the topic had some rather skeptical reviews Longuet-Higgins, But experimental advances have raised a new awareness and several recent reviews e. The number of proven facts is still rather small. We can however outline a few of them here in a preliminary way.

Theoretical physics

Though the quantum theory treats statistical ensembles in a satisfactory way, we are unable to describe individual quantum processes without bringing in unsatisfactory assumptions, such as the collapse of the wave function.

There is by now the well-known nonlocality that has been brought out by Bell [2] in connection with the EPR experiment, 3. Above all, there is the inability to give a clear notion of what the reality of a quantum system could be.

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All that is clear about the quantum theory is that it contains an algorithm for computing the probabilites of experimental results. But it gives no physical account of individual quantum processes.

Indeed, without the measuring instruments in which the predicted results appear, the equations of the quantum theory would be just pure mathematics that would have no physical meaning at all. And thus quantum theory merely gives us generally statistical knowledge of how our instruments will function. And from this we can make inferences that contribute to our knowledge, for example, of how to carry out various technical processes.

That is to say, it seems, as indeed Bohr [3] and Heisenberg [4] have implied, that quantum theory is concerned only with our knowledge of reality and especially of how to predict and control the behaviour of this reality, at least as far as this may be possible. Or to put it in more philosophical terms, it may be said that quantum theory is primarily directed towards epistemology which is the study that focuses on the question of how we obtain our knowledge and possibly on what we can do with it.

It follows from this that quantum mechanics can say little or nothing about reality itself.

In philosophical terminology, it does not give what can be called an ontology for a quantum system. Ontology is concerned primarily with that which is and only secondarily with how we obtain our knowledge about this in the sense, for example, that the process of observation would be treated as an interaction between the observed system and the observing apparatus regarded as existing together in a way that does not depend significantly on whether these are known or not.

However, we now feel that these terms are too restrictive. First of all, our variables are not actually hidden. For example, we introduce the concept that the electron is a particle with well-defined position and momentum that is, however, profoundly affected by a wave that always accompanies it see chapter 3. Far from being hidden, this particle is generally what is most directly manifested in an observation. The only point is that its properties cannot be observed with complete precision within the limits set by the uncertainty principle.

Nor is this sort of theory necessarily causal. For, as shown in chapter 9, we can also have a stochastic version of our ontological interpretation. The question of determinism is therefore a secondary one, while the primary question is whether we can have an adequate conception of the reality of a quantum system, be this causal or be it stochastic or be it of any other nature.

In chapter 14 section Some theories may be more nearly determinate, while others are less so. The way is open for the constant discovery of new theories, but ultimately these must be related coherently. However, there is no reason to suppose that physical theory is steadily approaching some final truth.

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It is always open as has indeed generally been the case that new theories will have a qualitatively different content within which the older theories may be seen to fit together, perhaps in some approximate way.

Since there is no final theory, it cannot be said that the universe is either ultimately deterministic or ultimately in-deterministic. Therefore we cannot from physical theories alone draw any conclusions, for example, about the ultimate limits of human freedom.

It will be shown throughout this book that our interpretation gives a coherent treatment of the entire domain covered by the quantum theory. This means that it is able to lead to the same statistical results as do other generally accepted interpretations.

In particular these include the Bohr interpretation and variations on this which we shall discuss in chapter 2 e. For the sake of convenience we shall put these altogether and call them the conventional interpretation.

Although our main objective in this book is to show that we can give an ontological explanation of the same domain that is covered by the conventional interpretation, we do show in the last two chapters how it is possible in our approach to extend the theory in new ways implying new experimental consequences that go beyond the current quantum theory.

Such new theories could be tested only if we could find some domain in which the quantum theory actually breaks down. In the last two chapters we sketch some new theories of this kind and indicate some areas in which one may expect the quantum theory to break down in a way that will allow for a test.

Partly because it has not generally been realised that our interpretation has such new possibilities, the objection has been raised that it has no real content of its own and that it merely recasts the content of the conventional interpretation in a different language.

Firstly we make the general point that the above argument could be turned the other way round. Thus de Broglie proposed very early what is, in essence, the germ of our approach. But this met intense opposition from leading physicists of the day.

This was especially manifest at the Solvay Congress of [7].

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This opposition was continued later when in one of us [5] proposed an extension of the theory which answered all the objections and indeed encouraged de Broglie to take up his ideas again. For a discussion of the history of this development and the sociological factors behind it, see Cushing [8] and also Pinch [9].

What then would have happened, if 25 years later some physicists had come along and had proposed the current interpretation which is at present the conventional one? Clearly by then there would be a large number of physicists trained in the de Broglie interpretation and these would have found it difficult to change.

This is the kind of answer that we are giving now to this particular criticism of our own interpretation. Let us then consider what we regard as the main advantages of our interpretation.

Firstly, as we shall explain in more detail throughout the book but especially in chapters 13, 14 and 15, it provides an intuitive grasp of the whole process. This makes the theory much more intelligible than one that is restricted to mathematical equations and statistical rules for using these equations to determine the probable outcomes of experiments.

Even though many physicists feel that making such calculations is basically what physics is all about, it is our view that the intuitive and imaginative side which makes the whole theory intelligible is as important in the long run as is the side of mathematical calculation.

Secondly, as we shall see in chapter 8, our interpretation can be shown to contain a classical limit within it which follows in a natural way from the theory itself without the need for any special assumptions.

On the other hand, in the conventional interpretation, it is necessary to presuppose a classical level before the quantum theory can have any meaning see Bohm [10]. The correspondence principle then demonstrates the consistency of the quantum theory with this presupposition. But this does not change the fact that without presupposing a classical level there is no way even to talk about the measuring instruments that are essential in this interpretation to give the quantum theory a meaning.

Because of the need to presuppose the classical level and perhaps eventually an observer , there is no way in the conventional interpretation to give a consistent account of quantum cosmology.

For, as this interpretation now stands, it is always necessary to assume an observer or his proxy in the form of an instrument which is not contained in the theory itself. If this theory is intended to apply cosmologically, it is evidently necessary that we should not, from the very outset, assume essential elements that are not capable of being included in the theory. Our interpretation does not suffer from this difficulty because the classical level flows out of the theory itself and does not have to be presupposed from outside.

Finally as we have already pointed out our approach has the potentiality for extension to new theories with new experimental consequences that go beyond the quantum theory. However, because our interpretation and the many others that have been proposed lead, at least for the present, to the same predictions for the experimental results, there is no way experimentally to decide between them.

Arguments may be made in favour or against any of them on various bases, which include not only those that we have given here, but also questions of beauty, elegance, simplicity and economy of hypotheses.

However, these latter are somewhat subjective and depend not only on the particular tastes of the individual, but also on socially adopted conventions, consensual opinions and many other such factors which are ultimately imponderable and which can be argued many ways as we shall indeed point out in more detail especially in chapters 14 and There does not seem to be any valid reason at this point to decide finally what would be the accepted interpretation.

But is there a valid reason why we need to make such a decision at all? Would it not be better to keep all options open and to consider the meaning of each of the interpretations on its own merits, as well as in comparison with others?

This implies that there should be a kind of dialogue between different interpretations rather than a struggle to establish the primacy of any one of them. This point is discussed more fully in Bohm and Peat [11]. The book may be divided roughly into four parts. The first part is concerned with the basic formulation of our interpretation in terms of particles. We begin in chapter 2 by discussing something of the historical background of the conventional interpretation, going into the problems and paradoxes that it has raised.

In chapter 3 we go on to propose our ontological interpretation for the one-body system which however is restricted to a purely causal form at this stage see Bohm and Hiley [12]. We are led to a number of new concepts, especially that of active information, which help to make the whole approach more intelligible, and we illustrate the approach in terms of a number of key examples. In chapter 4 we extend this interpretation to the many-body system and we find that this leads to further new concepts.

The most important of these are nonlocality and objective wholeness. That is to say, particles may be strongly connected even when they are far apart, and this arises in a way which implies that the whole cannot be reduced to an analysis in terms of its constituent parts. In chapter 5 we apply these ideas to study the process of transition. In both cases we see that these transitions can be treated objectively without reference to observation or measurement.

Moreover the process of transition can in principle be followed in detail, at least conceptually, in a way that makes the process intelligible whereas in the conventional interpretation, as shown in chapter 2, no such account is possible. This sort of insight into the process enables us to understand, for example, how quantum transitions can take place in a time that is very much shorter than the mean life time of the quantum state.

In the next part of the book we discuss some of the more general implications of our approach. Thus in chapter 6 we go into the theory of measurement. We treat this as an objective process in which the measuring instrument and what is observed interact in a well-defined way.

The other channels are shown to become inoperative. And yet everything behaves as if the wave function had collapsed to one of the channels.

The probability of a particular result of the interaction between the instrument and the observed object is shown to be exactly the same as that assumed in the conventional interpretation.

But the key new feature here is that of the undivided wholeness of the measuring instrument and the observed object, which is a special case of the wholeness to which we have alluded in connection with quantum processes in general. Rather what actually happens is that the process of interaction reveals a property involving the whole context in an inseparable way. Indeed it may be said that the measuring apparatus and that which is observed participate irreducibly in each other, so that the ordinary classical and common sense idea of measurement is no longer relevant.

The many paradoxes that have arisen out of the attempt to formulate a measurement theory in the conventional interpretation are shown not to arise in our interpretation. These include the treatment of negative measurements i. In chapter 7 we work out the implications of nonlocality in the framework of our interpretation. We include a discussion of the Bell inequality [2] and the EPR experiment [16].

We then go on to discuss how nonlocality disappears in the classical limit, except in the special case of the symmetry and antisymmetry of the wave function for which there is a superselection rule, implying that EPR correlations can be maintained indefinitely even at the large scale. This explains how the Pauli exclusion principle can be understood in our interpretation. Finally we discuss and answer objections to the concept of nonlocality.

In chapter 8 we discuss how the classical limit of the quantum theory emerges in the large scale level, without any break in the whole process either mathematically or conceptually. Thus, as we have already explained earlier, we do not need to presuppose the classical level as required in the conventional interpretation. In the next part of the book we extend our approach in several ways. Firstly in chapter 9, we discuss the role of statistics in our interpretation. We show that in typical situations the particles behave chaotically in a many-body system.

We then go on to treat quantum statistical mechanics in our framework and show how the density matrix can be derived as a simplified form that expresses what is essential about the statistical distribution of wave functions.

Finally we discuss an alternative approach to this question which has been explored in the literature [17], i. In chapter 10 we develop an ontological interpretation of the Pauli equation. We begin with a discussion of the history of this interpretation, showing that the simple model of a spinning extended body will not work if we wish to generalise our theory to a relativistic context.

Instead, we are led to begin with an ontological interpretation of the Dirac equation and to consider its non-relativistic limit. We show that in addition to its usual orbital motion, the particle then has an additional circulatory motion which accounts for its magnetic moment and its spin.

We extend our treatment to the many-body system and illustrate this in terms of the EPR experiment for two particles of spin one-half. In chapter 11 we go on to consider the ontological interpretation of boson fields. We first give reasons showing the necessity for starting with quantum field theories rather than particle theories in extending our interpretation to bosonic systems.

We then develop our ontological interpretation in detail, but from a non-relativistic point of view.

The key new concept here is that the field variables play the role which the particle variables had in the particle theory, while there is a superwave function of these field variables, that replaces the wave function of the particle variables. We illustrate this approach with several relevant examples.

We then go on to explain why the basically continuous field variables nevertheless deliver quantised amounts of energy to material systems such as atoms. Finally we show how our interpretation works in interference experiments of various kinds. In chapter 12 we discuss the question of the relativistic invariance of our approach. We begin by showing that the interpretation is relativistically invariant for the one-particle Dirac equation.

However, for the many-particle Dirac equation, only the statistical predictions are relativistically invariant. Because of nonlocality, the treatment of the individual system requires a particular frame of reference e. The same is shown to hold in our interpretation for bosonic fields [18]. We finally show, however, that it is possible to obtain a consistent approach by assuming a sub-relativistic level of stochastic movement of particles which contains the ordinary statistical results of the quantum theory as well as the behaviour of the world of large scale experience which is Lorentz covariant.

Therefore we are able to explain the covariance of all the experimental observations thus far available at least for all practical purposes.We indicate how this notion is contained mathematically in an algebra which is essentially the algebra of quantum mechanics itself. There does not seem to be any valid reason at this point to decide finally what would be the accepted interpretation.

That is to say, it seems, as indeed Bohr [3] and Heisenberg [4] have implied, that quantum theory is concerned only with our knowledge of reality and especially of how to predict and control the behaviour of this reality, at least as far as this may be possible. One may ask why physicists have felt the need to bring in mind in their attempts to make sense of the quantum theory. In this philosophy, science is not regarded as dealing with what is, so that concepts cannot be regarded as reflecting reality.

And this in turn implied that, at the quantum level of accuracy, there is no way to say what the electron is and what it does, such concepts being applicable approximately only in the classical correspondence limit. Firstly the quantum of action is taken to be indivisible and secondly it is assumed to be unpredictable and uncontrollable.

JULIA from Ann Arbor
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