Symmetries and Their Breaking in the Fundamental Laws of Physics

Abstract

Symmetries in the Physical Laws of Nature lead to observable effects. Beyond the regularities and conserved magnitudes, the last few decades in particle physics have seen the identification of symmetries, and their well-defined breaking, as the guiding principle for the elementary constituents of matter and their interactions. Flavour SU(3) symmetry of hadrons led to the Quark Model and the antisymmetric requirement under exchange of identical fermions led to the colour degree of freedom. Colour became the generating charge for flavour-independent strong interactions of quarks and gluons in the exact colour SU(3) local gauge symmetry. Parity Violation in weak interactions led us to consider the chiral fields of fermions as the objects with definite transformation properties under the weak isospin SU(2) gauge group of the Unifying Electro-Weak SU(2) × U(1) symmetry, which predicted novel weak neutral current interactions. CP-Violation led to three families of quarks opening the field of Flavour Physics. Time-reversal violation has recently been observed with entangled neutral mesons, compatible with CPT-invariance. The cancellation of gauge anomalies, which would invalidate the gauge symmetry of the quantum field theory, led to Quark–Lepton Symmetry. Neutrinos were postulated in order to save the conservation laws of energy and angular momentum in nuclear beta decay. After the ups and downs of their mass, neutrino oscillations were discovered in 1998, opening a new era about their origin of mass, mixing, discrete symmetries and the possibility of global lepton-number violation through Majorana mass terms and Leptogenesis as the source of the matter–antimatter asymmetry in the universe. The experimental discovery of quarks and leptons and the mediators of their interactions, with physical observables in spectacular agreement with this Standard Theory, is the triumph of Symmetries. The gauge symmetry is exact only when the particles are massless. One needs a subtle breaking of the symmetry, providing the origin of mass without affecting the excellent description of the interactions. This is the Brout–Englert–Higgs Mechanism, which produces the Higgs Boson as a remnant, discovered at CERN in 2012. Open present problems are addressed with by searching the New Physics Beyond-the-Standard-Model.

Fundamental Cause of Bio-Chirality: Space-Time Symmetry—Concept Review

“…It is beyond this article's scope to elucidate the physical significance of STS in the mathematical language of the Standard Model (SM) and String Theory (StrT) (see, [37][38][39]), but the logical ground for understanding is provided. The family of SM elementary particles (EPs) (see Figures 1 and 2) adequately describes the physical world at microscopic and cosmological scales [40][41][42][43].…”

Fundamental Cause of Bio-Chirality - Space-Time Symmetry: Concept Review

“…It is beyond the scope of this article to elucidate the physical significance of STS in the mathematical language (see, [Bernabeu 2020;Qadir & Camci. 2022], but the logical ground for understanding is provided.…”

Chirality and the Origin of Life

“…Living systems are predominantly based on CHNOPS atoms; thus, those atoms and their subatomic particles influence the properties of complex molecules of life. One of the theories which could strongly contribute to explaining the chirality of molecules of life is the theory of parity violation in weak interactions [94][95][96][97]. Until 1956, it was generally believed that all physical laws were the same for the image as for the mirror image; in other words, parity was conserved.…”