Ivancevic_Applied-Diff-Geom

38 Applied Differential Geometry: A Modern IntroductionFig. 1.4 An elementary particle split (a) and string split (b). When a single elementaryparticle splits in two particles, it occurs at a definite moment in space–time. On theother hand, when a string splits into two strings, different observers will disagree aboutwhen and where this occurred. A relativistic observer who considers the dotted line tobe a surface of constant time believes the string broke at the space–time point P whileanother observer who considers the dashed line to be a surface of constant time believesthe string broke at Q.String theory is a possible solution of the core quantum gravity problem,and in addition to gravity it can naturally describe interactions similar toelectromagnetism and the other forces of nature. Superstring theories includefermions, the building blocks of matter, and incorporate the so–calledsupersymmetry. 51 It is not yet known whether string theory will be able51 In a world based on supersymmetry, when a particle moves in space, it also canvibrate in the new fermionic dimensions. This new kind of vibration produces a ‘cousin’or ‘superpartner’ for every elementary particle that has the same electric charge butdiffers in other properties such as spin. Supersymmetric theories make detailed predictionsabout how superpartners will behave. To confirm supersymmetry, scientistswould like to produce and study the new supersymmetric particles. The crucial stepis building a particle accelerator that achieves high enough energies. At present, the