Ivancevic_Applied-Diff-Geom

Introduction 33theory itself existed at an energy so far from earthly energies that it took aleap of enormous faith to imagine the day when an experiment could evertest it. Quite simply, string theory seemed an excessively esoteric pursuit,which it still is.1.1.8.2 String Theory in ‘Plain English’With modern (super)string theory, 46 scientists might be on the verge of fulfillingEinstein’s dream: formulating the sought for ‘theory of everything’,which would unite our understanding of the four fundamental forces of Nature47 into a single equation (like, e.g., Newton, or Einstein, or Schrödingerequation) and explaining the basic nature of matter and energy.Fig. 1.2 All particles and forces of Nature are supposed to be manifestations of differentresonances of tiny 1D strings vibrating in a 10D hyper–space: (a) An ordinary matter;(b) A molecule; (c) An atom (around ten billionths of a centimeter in diameter; (d) Asubatomic particle (e.g., proton – around 100.000 times smaller than an atom); (e) Asuper–string (around 10 20 times smaller than a proton).In simplest terms, string theory states that all particles and forces of Natureare manifestations of different resonances of tiny 1–dimensional strings(rather than the zero–dimensional points (particles) that are the basis ofthe Standard Model of particle physics), vibrating in 10 dimensions (see46 Recall that ‘superstring’ means ‘supersymmetric string’. The supersymmetry (oftenabbreviated SUSY) is a hypothetical symmetry that relates bosons (particles thattransmit forces) and fermions (particles of matter). In supersymmetric theories, everyfundamental fermion has a bosonic ‘superpartner’ and vice versa.47 Recall that the four fundamental forces are: (i) Gravity (it describes the attractiveforce of matter; it is the same force that holds planets and moons in their orbits and keepsour feet on the ground; it is the weakest force of the four by many orders of magnitude);(ii) Electromagnetism (it describes how electric and magnetic fields work together; italso makes objects solid; once believed to be two separate forces, could be described bya relatively simple set of Maxwell equations); (iii) Strong nuclear force (it is responsiblefor holding the nucleus of atoms together; without it, protons would repel one anotherso no elements other than hydrogen, which has only one proton, would be able to form);(iv) Weak nuclear force (it explains beta decay and the associated radioactivity; it alsodescribes how elementary particles can change into other particles with different energiesand masses).