2,789 research outputs found

    Topological susceptibility at zero and finite temperature in the Nambu-Jona-Lasinio model

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    We consider the three flavor Nambu-Jona-Lasinio model with the 't Hooft interaction incorporating the U(1)_A anomaly. In order to set the coupling strength of the 't Hooft term, we employ the topological susceptibility χ\chi instead of the eta' meson mass. The value for χ\chi is taken from lattice simulations. We also calculate χ\chi at finite temperature within the model. Comparing it with the lattice data, we extract information about the behavior of the U(1)_A anomaly at finite temperature. We conclude that within the present framework, the effective restoration of the U(1)_A symmetry does not necessarily take place even at high temperature where the chiral symmetry is restored.Comment: 9 pages, 14 figures, to be published in Phys.Rev.

    Electronic charges and electric potential at LaAlO3/SrTiO3 interfaces studied by core-level photoemission spectroscopy

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    We studied LaAlO3/SrTiO3 interfaces for varying LaAlO3 thickness by core-level photoemission spectroscopy. In Ti 2p spectra for conducting "n-type" interfaces, Ti3+ signals appeared, which were absent for insulating "p-type" interfaces. The Ti3+ signals increased with LaAlO3 thickness, but started well below the critical thickness of 4 unit cells for metallic transport. Core-level shifts with LaAlO3 thickness were much smaller than predicted by the polar catastrophe model. We attribute these observations to surface defects/adsorbates providing charges to the interface even below the critical thickness

    Spectroscopy of SrRuO/Ru Junctions in Eutectic

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    We have investigated the tunnelling properties of the interface between superconducting Sr2RuO4 and a single Ru inclusion in eutectic. By using a micro-fabrication technique, we have made Sr2RuO4/Ru junctions on the eutectic system that consists of Sr2RuO4 and Ru micro-inclusions. Such a eutectic system exhibits surface superconductivity, called the 3-K phase. A zero bias conductance peak (ZBCP) was observed in the 3-K phase. We propose to use the onset of the ZBCP to delineate the phase boundary of a time-reversal symmetry breaking state.Comment: To be published in Proc of 24th Int. Conf. on Low Temperature Physics (LT24); 2 page

    High Metallicity of the X-Ray Gas up to the Virial Radius of a Binary Cluster of Galaxies: Evidence of Galactic Superwinds at High-Redshift

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    We present an analysis of a Suzaku observation of the link region between the galaxy clusters A399 and A401. We obtained the metallicity of the intracluster medium (ICM) up to the cluster virial radii for the first time. We determine the metallicity where the virial radii of the two clusters cross each other (~2 Mpc away from their centers) and found that it is comparable to that in their inner regions (~0.2 Zsun). It is unlikely that the uniformity of metallicity up to the virial radii is due to mixing caused by a cluster collision. Since the ram-pressure is too small to strip the interstellar medium of galaxies around the virial radius of a cluster, the fairly high metallicity that we found there indicates that the metals in the ICM are not transported from member galaxies by ram-pressure stripping. Instead, the uniformity suggests that the proto-cluster region was extensively polluted with metals by extremely powerful outflows (superwinds) from galaxies before the clusters formed. We also searched for the oxygen emission from the warm--hot intergalactic medium in that region and obtained a strict upper limit of the hydrogen density (nH<4.1x10^-5 cm^-3).Comment: Typo corrected. The published version is available on-line free of charge by the end of 2008. http://pasj.asj.or.jp/v60/sp1/60s133/60s133.pd

    Chemical potential shift induced by double-exchange and polaronic effects in Nd_{1-x}Sr_xMnO_3

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    We have studied the chemical potential shift as a function of temperature in Nd1−x_{1-x}Srx_xMnO3_3 (NSMO) by measurements of core-level photoemission spectra. For ferromagnetic samples (x=0.4x=0.4 and 0.45), we observed an unusually large upward chemical potential shift with decreasing temperature in the low-temperature region of the ferromagnetic metallic (FM) phase. This can be explained by the double-exchange (DE) mechanism if the ege_g band is split by dynamical/local Jahn-Teller effect. The shift was suppressed near the Curie temperature (TCT_C), which we attribute to the crossover from the DE to lattice-polaron regimes.Comment: 5 pages, 6 figure

    Earthquake fault rock indicating a coupled lubrication mechanism

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    International audienceA pseudotachylyte bounded by a carbonate-matrix implosion breccia was found at a fossilized out-of-sequence thrust in the Shimanto accretionary complex, Japan. This occurrence resulted from the following events: first implosion of host rock due to interstitial fluid pressure increase and asymmetric fracturing; second, Ca-Fe-Mg carbonate precipitation; and third, frictional melting. The rock-record suggests that these events took place in a single seismogenic slip event. Resulting from abrupt drop in fluid pressure after implosion, hydro-fracturing and fluid escape, recovered high effective friction promoted melting during fault movement. Coexistence of fluid implosion breccia and pseudotachylyte has never been reported from continental pseudotachylytes, but might be characteristic from hydrous seismogenic faults in subduction zones
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