They will be mutually supportive but have minimal overlap and no repetition. I have learnt numerous conceptual and technical details and many deep insights from them and also from other theorists who were active in the early s through email exchanges. I also had long conversations with two experimenters Jerome Friedman of MIT and Gunter Wolf of DESY, and learnt from them various details of crucial experiments which led to the discovery of scaling and three-jet events. The SLAC archives was very helpful and provided me with the whole set of the original documents without which I would have no way to know how the deep inelastic scattering experiments were actually conceived, planned, performed, and interpreted.

Critical exchanges with two historians of science, Charles Gillispie of Princeton and Paul Forman of the Smithsonian Institution greatly helped me in the general conception of the project. Most memor- able was a whole-day small workshop around 20 participants at Princeton, on April 20, , chaired by Stephen Adler, at which I reported my pre- liminary researches on the history of QCD.

## From Current Algebra to Quantum Chromodynamics

Murray Gell-Mann, Arthur Wightman, Charles Gillispie and Paul Benacerraf, together with those from the Institute, took an active part, examined various issues raised by those preliminary results, made helpful comments, provided much background information, and had interesting exchanges of judgments.

To all those institutions and scholars I owe my most sincere gratitude. My research was interrupted several times by emotional turbulences caused by my mothers death and several deaths of close relatives and friends in the last few years. In the difficult times unfailing support from my wife Lin Chun and sister Nanwei helped me recover from depression and carry the project ahead. I am deeply grateful to them. Attempts were made to take some particles, such as the proton, neutron and lambda particle, as more fundamental than others, so that all other hadrons could be derived from the fundamental ones Fermi and Yang, ; Sakata, But the prevailing understanding was that all elementary particles were equally elementary, none was more fundamental than others.

This general consensus was summarized in the notion of nuclear democracy or hadronic egalitarianism Chew and Frautschi, a, b; Gell-Mann, As to the dynamics that governs hadrons behavior in the processes of strong interactions, early attempts to model on the successful theory of quantum electrodynamics or QED, a special version of quantum field theory, or QFT, in the case of electromagnetism , namely the meson theory, failed, and failed without redemption cf.

Cao, , Section 8.

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More general oppositions to the use of QFT for understanding strong interactions were raised by Landau and his collaborators, on the basis of serious dyna- mical considerations Landau, Abrikosov, and Khalatnikov, a, b, c, d; Landau, The resulting situation since the mid s was characterized by a general retreat from fundamental investigations to phenomenological ones in hadron physics. The prevailing enquiry was phenomenological because no detailed understanding of what is going on in strong interactions was assumed or even aspired to, although some general principles such as those of crossing, analyticity, unitarity, and symmetry abstracted from some model dynamical theories were appealed to for reasoning from inputs to outputs; thereby the enquiry enjoyed some explanatory and predictive power.

The unanimous consensus in the physics community and, through popularization, in the general public became as follows. First, all hadrons were composed of quarks that were held together by gluons; and second, the dynamics of quarkgluon interactions was properly understood and mathematically formulated in quantum chromodynamics or QCD. As to the strong interaction among hadrons, it could be understood as the uncancelled residual of the quarkgluon super-strong interaction, a kind of Van der Waals force of the hadrons. Such a radical change in our conception of the fundamental ontology of the physical world and its dynamics was one of the greatest achievements in the history of science.

The intellectual journey through which the conception was remolded is much richer and more complicated than a purely conceptual one in which some ideas were replaced by others. The journey was fascinating and full of implications, and thus deserves comprehensive historical investi- gation. However, even the conceptual part of the story is illuminative enough to make some historical and philosophical points.

### Escape From Every day Life

While a full-scale historical treatment of the episode is in preparation, Cao, forthcoming the present enquiry, as part of the more comprehensive project, has a more modest goal to achieve. That is, it aims to give a concise outline of crucial conceptual developments in the making of QCD. More precisely, its attention is restricted to the journey from the proposal of current algebra in to the conceptual and mathematical formulation of QCD in As a brief conceptual history, its intention is twofold.

For the general readers, it aims to help them grasp the major steps in the reconceptualization of the fundamental ontology of the physical world and its dynamics without being troubled by technical details.

However, it is not intended to be a popular exposition. For experts who are familiar with the details original texts and technical subtleties , it promises to offer a decent history, in which distorted records will be straightened, the historical meaning of each step in the development clarified, and significance properly judged, on the basis of present understanding of the relevant physics and its historical development, that is, helped by hindsight and present perspective.

The preliminary investigations pursued so far have already revealed some- thing of deep interest, and thus provided a firm ground for making some claims about the objectivity and progress of scientific knowledge, the central topics in contemporary debate about the nature of scientific knowledge and its historical changes.

## Quantum chromodynamics - Wikipedia

Pivotal to the debate is the status of unobservable theoretical entities such as quarks and gluons. Do they really exist in the physical world as objective 2 Introduction entities, independently of human will, or exist merely as human constructions for their utility in organizing our experiences and predicting future events? If the former is the case, then a related question is whether we can have true knowledge of them, and how? Lectures , pages : Geometry of gauge fields notes on this are kind of sketchy , abelian Higgs model and vortices, local discrete symmetry, anyons , abelian Chern -Simons theory, fractional quantum Hall effect.

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Lectures , pages : Magnetic Cheshire charge, Strings ending on monopoles, walls bounded by strings, topological classification of gauge fields, cohomology with integer coefficients, U 1 bundles, first Chern class, torsion classes, flat connections on nonorientable manifolds, G-bundles. Lectures , pages : Yang-Mills theory and its quantization, theta vacua and CP nonconservation , theta-dependent dyon charge, nonabelian monopoles and global gauge transformations.

Part IV: Anomalies. Lecture 32, pages : Chiral anomaly in two and four dimensions as chiral pair production in electromagnetic fields, vector and axial Ward identities, anomalies and massless particles.

### 5 editions of this work

Chapters Chapter 1, Quantum Mechanics: states, observables, measurements, dynamics, spectra. Chapter 2, Time-Dependent Scattering Formalism: asymptotic states, wave operators, S-matrix, cross section, optical theorem. Chapter 3, Analytic functions: derivative, integrals, power series, residue theorem, analytic continuation, Riemann surfaces. Chapter 5, Methods of Approximation: Born series, Born approximation, convergence, Yukawa potential, Fredholm method, quasiparticle method.

Chapter 6. Chapter 7, Complex Angular Momentum and Regge Poles: analytic continuation in angular momentum, Regge poles, Coulomb potential, Sommerfeld -Watson transform, Regge poles in relativistic scattering, Froissart bound. Chapter 8, Dispersion Relations: forward amplitude, partial-wave dispersion relations, nonzero momentum transfer, fixed energy, Mandelstam representation.