Vertex in quantum electrodynamics.

However, attempts to quantize electromagnetic theory entirely were stymied throughout the 1930s by theoretical formulations yielding infinite energies. This situation was not considered adequately resolved until after World War II ended, when Julian Schwinger, Richard Feynman, and Sin-Itiro Tomonaga independently posited the technique of “renormalization”, which allowed for an establishment of a robust quantum electrodynamics (Q.E.D.).

2. Meanwhile, new theories of fundamental particles proliferated with the rise of the idea of the quantization of fields through “exchange forces” regulated by an exchange of short-lived “virtual” particles, which were allowed to exist according to the laws governing the uncertainties inherent in the quantum world. Notably, Hideki Yukawa proposed that the positive charges of the nucleus were kept together courtesy of a powerful but short-range force mediated by a particle intermediate in mass between the size of an electron and a proton. This particle, called the “pion”, was identified in 1947, but it was part of a slew of particle discoveries beginning with the neutron, the “positron” (a positively-charged “antimatter” version of the electron), and the “muon” (a heavier relative to the electron) in the 1930s, and continuing after the war with a wide variety of other particles detected in various kinds of apparatus: cloud chambers, nuclear emulsions, bubble chambers, and coincidence counters. At first these particles were found primarily by the ionized trails left by cosmic rays, but were increasingly produced in newer and more powerful particle accelerators.

3. Thousands of particles explode from the collision point of two relativistic (100 GeV per ion) gold ions in the STAR detector of the Relativistic Heavy Ion Collider; an experiment done in order to investigate the properties of a quark gluon plasma such as the one thought to exist in the ultrahot first few microseconds after the big bang.

4. The interaction of these particles by “scattering” and “decay” provided a key to new fundamental quantum theories. Murray Gell-Mann and Yuval Ne’eman brought some order to these new particles by classifying them according to certain qualities, beginning with what Gell-Mann referred to as the “Eightfold Way”, but proceeding into several different “octets” and “decuplets” which could predict new particles, most famously the Ω⁻, which was detected at Brookhaven National Laboratory in 1964, and which gave rise to the “quark” model of hadron composition.

Figure 13 - Theories of fundamental particles

While the quark model at first seemed inadequate to describe strong nuclear forces, allowing the temporary rise of competing theories such as the S-Matrix, the establishment of quantum chromodynamics in the 1970s finalized a set of fundamental and exchange particles, which allowed for the establishment of a “standard model” based on the mathematics of gauge invariance, which successfully described all forces except for gravity, and which remains generally accepted within the domain to which it is designed to be applied.

5. The “standard model” groups the electroweak interaction theory and quantum chromodynamics into a structure denoted by the gauge group SU(3)×SU(2)×U(1). The formulation of the unification of the electromagnetic and weak interactions in the standard model is due to Abdus Salam, Steven Weinberg and, subsequently, Sheldon Glashow. After the discovery, made at CERN, of the existence of neutral weak currents, mediated by the Z boson foreseen in the standard model, the physicists Salam, Glashow and Weinberg received the 1979 Nobel Prize in Physics for their electroweak theory.

6. While accelerators have confirmed most aspects of the standard model by detecting expected particle interactions at various collision energies, no theory reconciling the general theory of relativity with the standard model has yet been found, although “string theory” has provided one promising avenue forward. Since the 1970s, fundamental particle physics has provided insights into early universe cosmology, particularly the “big bang” theory proposed as a consequence of Einstein’s general theory. However, starting from the 1990s, astronomical observations have also provided new challenges, such as the need for new explanations of galactic stability (the problem of dark matter), and accelerating expansion of the universe (the problem of dark energy) [10, http://en.wikipedia.org/wiki/History_of_physics].

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