Yasunori Nomura works mainly on particle physics theory and cosmology. He has developed the framework of grand unified field theories in higher dimensions (sometimes called “orbifold GUTs”) and proposed it as simultaneous solutions to the problems of 4-dimensional supersymmetric grand unified theories, such as the doublet-triplet splitting, too fast proton decay, and wrong fermion mass problems . Based on this framework, he constructed first fully realistic models in which standard model gauge and Higgs fields, as well as gauge and Yukawa couplings, are unified in higher dimensions .
He also works on new physics theories beyond the standard model at the TeV scale. He proposed a class of models in which the Higgs boson arises as a pseudo Nambu-Goldstone boson from an extra dimensional component of a gauge field in dual higher dimensional warped space (called holographic Higgs models) , identified a region of parameter space in weak scale supersymmetry where the fine-tuning of electroweak symmetry breaking is minimized (called natural supersymmetry) , introduced a framework in which a precise prediction of the Higgs boson mass is obtained because of supersymmetry broken at high energies (the high scale SUSY scenario) , and proposed a scenario in which supersymmetry is broken in multiple separate sectors, leading to rich experimental signatures coming from multiple weakly interacting Goldstone fermion particles (the Goldstini scenario) .
More recently, he has proposed that the eternally inflating multiverse and many worlds in quantum mechanics are the same concept . He has developed a new theoretical framework to describe dynamics of quantum gravity in low energy regimes, preserving locality . This leads to a picture that general relativistic, global spacetime is an only emerging, classical concept arising from a special relativistic, quantum mechanical description of quantum gravity. He has applied this idea to the multiverse, in which the multiverse state does not have a beginning or end and time emerges only locally in branches corresponding to our own universe (the static quantum multiverse) .
 L.J. Hall and Y. Nomura, “Gauge unification in higher dimensions,” Phys.Rev. D64, 055003 (2001); “Grand unification in higher dimensions,” Annals Phys. 306, 132 (2003).
G. Burdman and Y. Nomura, “Unification of Higgs and gauge fields in five dimensions,” Nucl.Phys. B656, 3 (2003).
 R. Contino, Y. Nomura, and A. Pomarol, “Higgs as a holographic pseudo-Goldstone boson,” Nucl.Phys. B671, 148 (2003).
 R. Kitano and Y. Nomura, “Supersymmetry, naturalness, and signatures at the LHC,” Phys.Rev. D73, 095004 (2006).
 L.J. Hall and Y. Nomura, “A finely-predicted Higgs boson mass from a finely-tuned weak scale,” JHEP 03, 076 (2010).
 C. Cheung, Y. Nomura, and J. Thaler “Goldstini,” JHEP 03, 073 (2010).
 Y. Nomura, “Physical theories, eternal inflation, and the quantum universe,” JHEP 11, 063 (2011); “Quantum mechanics, gravity, and the multiverse,” Astron.Rev. 7, 36 (2012).
 Y. Nomura, J. Varela, and S.J. Weinberg, “Low energy description of quantum gravity and complementarity,” arXiv:1304.0448; Y. Nomura, “Quantum mechanics, spacetime locality, and gravity,” arXiv:1110.4630.
 Y. Nomura, "The static quantum multiverse," Phys.Rev. D86, 083505 (2012).