Unification of Fundamental Forces: Strengths and Limitations of Leading Quantum Gravity Approaches
Keywords:
Unification of Forces, Quantum Gravity, String Theory, Grand Unified Theory, Loop Quantum Gravity, Asymptotic Safety, Gauge Coupling Unification, SupersymmetryAbstract
The unification of fundamental forces represents the ultimate goal of theoretical physics, seeking a single framework encompassing gravitational, electromagnetic, weak, and strong interactions. This study presents a comprehensive comparative analysis of leading quantum gravity approaches—String Theory, Loop Quantum Gravity (LQG), Asymptotic Safety, and Causal Dynamical Triangulations (CDT)—evaluating their capacity for force unification, mathematical consistency, and experimental testability. The Standard Model gauge group is embedded within Grand Unified Theories through groups such as , , and , with supersymmetric extensions achieving precise gauge coupling unification at GeV with . String Theory, based on the worldsheet action with mass spectrum , automatically incorporates gravity and gauge interactions through D-brane configurations. LQG, built on the Ashtekar–Barbero connection with discrete area spectrum , addresses quantum gravity but requires separate matter coupling. Asymptotic Safety posits a non-trivial ultraviolet fixed point with . CDT constructs spacetime from discrete simplices maintaining causal structure. We evaluate proton decay predictions ( ) against current bounds years, analyze black hole entropy corrections, and assess Loop Quantum Cosmology’s bounce scenario through the modified Friedmann equation . Experimental prospects including gravitational wave astronomy, CMB measurements, and proton decay searches are discussed as paths toward empirical discrimination.
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