We study three quark systems in Maximally Abelian (MA) and Maximal Center (MC) projected QCD on quenched SU(3) lattice, and also in the monopole/photon part, where only the color-electric/magnetic current exists, using the Hodge decomposition. First, we perform the quantitative study of the three-quark (3Q) potential V_{3Q} and the string tension sigma_{3Q} in baryons. For MA projected QCD, the monopole part and MC projected QCD, we find that the confinement potential in V_{3Q} obeys the Y-Ansatz and the string tension sigma_{3Q} is approximately equal to that in SU(3) QCD. The universality of the string tension, sigma_{3Q} simeq sigma_{Qbar Q}, is also found between the 3Q and the Qbar Q potentials. We find a strong similarity of the inter-quark potential between the monopole part and MC projected QCD. In contrast, almost no confinement force is found in the inter-quark potential in the photon part. Next, we study the spectrum of light hadrons in MA projected QCD and the monopole/photon part, paying attention to the N-Delta mass splitting. We find that the N-Delta mass splitting is significantly reduced in MA projected QCD and the monopole part, where the one-gluon-exchange effect or the Coulomb-potential part is largely reduced due to the Abelianization or the Hodge decomposition. This fact seems to indicate that the main origin of the mass splitting is one-gluon exchange.
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