In 1961 M. Gell-Mann published a report entitled The Eightfold way: a theory of strong interactions symmetry. He wrote: “It has seemed likely for many years that the strongly interacting particles, grouped as they are into isotopic multiplets, would show traces of a higher symmetry that is somehow broken. Under the higher symmetry, the eight familiar baryons would be degenerate and form a super-multiplet.

We have now collected all the building blocks to write down the most up-to-date theory of particle physics. As we have seen in the previous chapters, it took several decades to develop it, basically in several stages during the second half of the 20th century. Its current form was finalized during the 1970s. The Standard Model (SM) describes the electromagnetic, weak, and strong interactions (but not gravity) among fundamental fermions of Nature.

The SM is without doubt a great success of particle physics. It describes a very wide range of precise experimental measurements remarkably well. Nonetheless, it is still considered as a model based on perturbative quantum field theory constructed on fundamental gauge symmetries that are spontaneously broken.

In 1766, Cavendish wrote a paper called “On factitious airs” [11]. He is attributed the discovery of what he called inflammable air, known today as hydrogen. Hydrogen was mainly characterized by its physico-chemical properties in order to study in detail its behavior in combustion reactions. In 1855 Ångström, one of the founders of spectroscopy, published the results of his investigations on the line spectrum of hydrogen.

Quantum chromodynamics (QCD), the theory of the strong interaction, was formulated in the early 1970s as a non-Abelian gauge field theory of quarks that interact by the exchange of spin-1 massless gluons. Today QCD is part of the Standard Model of particle physics and is one of the pillars on which our understanding of Nature rests.

We review in this chapter the foundations of non-relativistic quantum mechanics (see also ), which we like to call “classical quantum mechanics” as opposed to the relativistic quantum mechanics.

Neutrinos can be considered as special particles under a certain point of view. They are elementary fermions which are exceptionally elusive and penetrating (e.g., capable of traversing the Earth unaffected, although at energies above tera-electronvolts, the Earth starts to become less transparent). This puzzling property comes from the fact that neutrinos do not carry color and are electrically neutral, hence do not feel the strong nor the electromagnetic force and interact only via the weak force (not considering gravity). Neutrinos are also very light, practically massless, and so far, no one has succeeded in measuring their rest (absolute) masses.

The understanding of 𝐶𝑃 violation in particle physics is a key input ingredient to the cosmology of the early Universe. It is required to explain the observed dominance of matter over antimatter in the Universe (see Section 32.3). In 1967, Sakharov proposed a set of three necessary conditions that a baryon-generating interaction must satisfy to produce matter and antimatter at different rates.

The last three chapters were concerned with substantive law: the rules that governed everyday life and its transactions. But, in the end, the question whether a person enjoys a particular right comes down to whether he or she is able to enforce it in practice. This is where the issue of procedure, of litigation, is important. The first section of this chapter gives a sketch of the workings of the various Roman civil procedures in the classical period; to a large extent, this is confined to the bare facts. The second section then attempts to draw out the significance of the procedural rules for the vindication of rights in practice. It also deals briefly with access to the courts and legal representation.

To begin with what is not in this book may seem odd; but that will otherwise remain unknown until the end, which seems unsatisfactory. This is not a comprehensive account of Roman law or even of Roman law in its social setting. It is highly selective. Its focus is on the so-called classical period of Roman law, from about the end of the Roman republic in 31 bc until the death of the Emperor Severus Alexander in ad 235. There is not much here about post-classical law; and there is almost nothing about pre-classical law.