Average phase factor in the PNJL model

The average phase factor of the QCD determinant is evaluated at finite quark chemical potential ({\mu}_q) with the two-flavor version of the Polyakov-loop extended Nambu-Jona-Lasinio (PNJL) model with the scalar-type eight-quark interaction. For {\mu}_q larger than half the pion mass at vacuum m_{\pi}, the average phase factor is finite only when the Polyakov loop is larger than 0.5, indicating that lattice QCD is feasible only in the deconfinement phase. A critical endpoint (CEP) lies in the region of the zero average phase factor. The scalar-type eight-quark interaction makes it shorter a relative distance of the CEP to the boundary of the region. For {\mu}_q < m_{\pi}/2, the PNJL model with dynamical mesonic fluctuations can reproduce lattice QCD data below the critical temperature.Comment: 8 pages, 6 figure

Vector-type four-quark interaction and its impact on QCD phase structure

Effects of the vector-type four-quark interaction on QCD phase structure are investigated in the imaginary chemical potential region, by using the Polyakov-loop extended Nambu-Jona-Lasinio (PNJL) model with the extended Z3 symmetry. In the course to this end, we clarify analytically the Roberge-Weiss periodicity and symmetry properties of various quantities under the existence of a vector-type four-quark interaction. In the imaginary chemical potential region, the chiral condensate and the quark number density are sensitive to the strength of the interaction. Based on this result, we propose a possibility to determine the strength of the vector-type interaction, which largely affects QCD phase structure in the real chemical potential region, by comparing the results of lattice simulations and effective model calculations in the imaginary chemical potential region.Comment: 8 pages, 11 figure

Massive gene losses in Asian cultivated rice unveiled by comparative genome analysis

<p>Abstract</p> <p>Background</p> <p>Rice is one of the most important food crops in the world. With increasing world demand for food crops, there is an urgent need to develop new cultivars that have enhanced performance with regard to yield, disease resistance, and so on. Wild rice is expected to provide useful genetic resources that could improve the present cultivated species. However, the quantity and quality of these unexplored resources remain unclear. Recent accumulation of the genomic information of both cultivated and wild rice species allows for their comparison at the molecular level. Here, we compared the genome sequence of <it>Oryza sativa </it>ssp. <it>japonica </it>with sets of bacterial artificial chromosome end sequences (BESs) from two wild rice species, <it>O. rufipogon </it>and <it>O. nivara</it>, and an African rice species, <it>O. glaberrima</it>.</p> <p>Results</p> <p>We found that about four to five percent of the BESs of the two wild rice species and about seven percent of the African rice could not be mapped to the <it>japonica </it>genome, suggesting that a substantial number of genes have been lost in the <it>japonica </it>rice lineage; however, their close relatives still possess their counterpart genes. We estimated that during evolution, <it>O. sativa </it>has lost at least one thousand genes that are still preserved in the genomes of the other species. In addition, our BLASTX searches against the non-redundant protein sequence database showed that disease resistance-related proteins were significantly overrepresented in the close relative-specific genomic portions. In total, 235 unmapped BESs of the three relatives matched 83 non-redundant proteins that contained a disease resistance protein domain, most of which corresponded to an NBS-LRR domain.</p> <p>Conclusion</p> <p>We found that the <it>O. sativa </it>lineage appears to have recently experienced massive gene losses following divergence from its wild ancestor. Our results imply that the domestication process accelerated large-scale genomic deletions in the lineage of Asian cultivated rice and that the close relatives of cultivated rice have the potential to restore the lost traits.</p