929 research outputs found
The lattice QCD simulation of the quark-gluon mixed condensate g<\bar{q} \sigma G q> at finite temperature and the phase transition of QCD
The thermal effects on the quark-gluon mixed condensate g<\bar{q} \sigma G
q>, which is another chiral order parameter, are studied using the SU(3)c
lattice QCD with the Kogut-Susskind fermion at the quenched level. We perform
the accurate measurement of the mixed condensate as well as the quark
condensate for 0MeV<=T<=500MeV. We observe the sharp decrease of both the
condensates around T_c \simeq 280MeV, while the thermal effects below T_c are
found to be weak. We also find that the ratio m_0^2 = g<\bar{q} \sigma G
q>/ is almost independent of the temperature even in the very
vicinity of T_c, which indicates that the two condensates have nontrivial
similarity in the chiral behaviors. We also present the correlation between the
condensates and the Polyakov loop to understand the vacuum structure of QCD.Comment: Talk given at the XXII International Symposium on Lattice Field
Theory (LATTICE 2004), Fermilab, Batavia, Illinois, USA, 21-26 June 2004,
Lattice2004(non-zero), 3 pages, 3 figure
Bi-maximal mixing at GUT, the low energy data and the leptogenesis
In the framework of the minimum supersymmetric model with right-handed
neutrinos, we consider the Bi-maximal mixing which is realized at the GUT scale
and discuss a question that this model can reproduce the low energy phenomena
and the leptogenesis.Comment: Talk given by E. Takasugi at NuFact04, Osaka, Japan, July 26 - August
1,2004 - 3 pages, 4 figure
Generation of Seed Magnetic Field around First Stars: the Biermann Battery Effect
We investigate generation processes of magnetic fields around first stars.
Since the first stars are expected to form anisotropic ionization fronts in the
surrounding clumpy media, magnetic fields are generated by effects of radiation
force as well as the Biermann battery effect. We have calculated the amplitude
of magnetic field generated by the effects of radiation force around the first
stars in the preceding paper, in which the Biermann battery effects are not
taken into account.In this paper, we calculate the generation of magnetic
fields by the Biermann battery effect as well as the effects of radiation
force, utilizing the radiation hydrodynamics simulations. As a result, we find
that the generated magnetic field strengths are ~ 10^{-19}G-10^{-17}G at ~
100pc-1kpc scale mainly by the Biermann battery, which is an order of magnitude
larger than the results of our previous study. We also find that this result is
insensitive to various physical parameters including the mass of the source
star, distance between the source and the dense clump, unless we take unlikely
values of these parameters.Comment: 19 pages, 7 figures, Accepted for publications in Ap
Grazing on Microcystis (Cyanophyceae) by testate amoebae with special reference to cyanobacterial abundance and physiological state
We examined the growth of testate amoebae preying on Microcystis whose physiological states were different in laboratory experiments and a hypertrophic pond. We prepared three experimental systems using water samples dominated by Microcystis aeruginosa: light incubation (control), dark incubation (dark), and light incubation with addition of nitrogen and phosphorus (+NP). In all the systems, the colony density of M. aeruginosa decreased slightly during incubation. Physiological activity of phytoplankton as determined by chlorophyll fluorescence was high and almost constant in the control and +NP systems, whereas it decreased in the dark system. Cell densities of testate amoebae increased in the control and +NP systems, whereas in the dark system they remained low. Thus, growth of the amoebae was low in the systems where physiological activity of Microcystis was low. In a hypertrophic pond, cell density of testate amoebae increased and remained high when M. aeruginosa predominated. Cell density of testate amoebae increased remarkably, simultaneously with the increases in M. aeruginosa colony density and phytoplankton physiological activity. We also found a significant correlation between densities of M. aeruginosa colonies and testate amoebae. We suggested that the physiological activity of Microcystis is one important factor affecting the growth of testate amoebae grazing on Microcystis
Large Late-time Asphericities in Three Type IIP Supernovae
Type II-plateau supernovae (SNe IIP) are the results of the explosions of red
supergiants and are the most common subclass of core-collapse supernovae. Past
observations have shown that the outer layers of the ejecta of SNe IIP are
largely spherical, but the degree of asphericity increases toward the core. We
present evidence for high degrees of asphericity in the inner cores of three
recent SNe IIP (SNe 2006my, 2006ov, and 2007aa), as revealed by late-time
optical spectropolarimetry. The three objects were all selected to have very
low interstellar polarization (ISP), which minimizes the uncertainties in ISP
removal and allows us to use the continuum polarization as a tracer of
asphericity. The three objects have intrinsic continuum polarizations in the
range of 0.83-1.56% in observations taken after the end of the photometric
plateau, with the polarization dropping to almost zero at the wavelengths of
strong emission lines. Our observations of SN 2007aa at earlier times, taken on
the photometric plateau, show contrastingly smaller continuum polarizations
(~0.1%). The late-time H-alpha and [O I] line profiles of SN 2006ov provide
further evidence for asphericities in the inner ejecta. Such high core
polarizations in very ordinary core-collapse supernovae provide further
evidence that essentially all core-collapse supernova explosions are highly
aspherical, even if the outer parts of the ejecta show only small deviations
from spherical symmetry.Comment: 15 pages, 13 figures, minor revisions to match published version
(2010, ApJ, 713, 1363
Crystallographic texture- and grain boundary density-independent improvement of corrosion resistance in austenitic 316L stainless steel fabricated via laser powder bed fusion
Improvement of corrosion resistance of austenitic 316L stainless steel via laser powder bed fusion (LPBF) is currently a prominent research topic; however, the effects of crystallographic texture and the related grain boundary density on the corrosion resistance of LPBF-fabricated parts have not been elucidated. For biomedical applications, crystallographic texture control from a single crystalline-like to randomly oriented polycrystalline microstructure is highly attractive for optimizing the mechanical properties (particularly the Young's modulus) of implants. An investigation of the impacts of crystallographic planes and grain boundaries exposed to the biological environment on corrosion behavior is necessary. 316L stainless steels with different crystallographic textures and grain boundary densities were successfully fabricated via LPBF. The corrosion resistances of the LPBF-fabricated specimens were comprehensively assessed by anodic polarization, dissolution, and crevice corrosion repassivation tests. The LPBF-fabricated specimens showed extremely high pitting potentials in the physiological saline compared with the commercially available counterparts, and importantly, excellent pitting corrosion resistance was observed irrespective of the crystallographic planes and grain boundary density exposed. Moreover, the LPBF-fabricated specimens did not show metastable pitting corrosion even in an accelerated test using an acid solution. The repassivation behavior of the specimens was not affected by LPBF. Such a drastic improvement in the corrosion resistances of the LPBF-fabricated specimens might be attributed to suppression of inclusion coarsening owing to the rapid cooling rate during solidification in LPBF. By using LPBF, the desired crystallographic texture can be introduced based on the desired mechanical properties without concern for corrosiveness.Tsutsumi Y., Ishimoto T., Oishi T., et al. Crystallographic texture- and grain boundary density-independent improvement of corrosion resistance in austenitic 316L stainless steel fabricated via laser powder bed fusion. Additive Manufacturing, 45, 102066. https://doi.org/10.1016/j.addma.2021.102066
Quantum Magnetization Plateau in Spin-1 Triangular-Lattice Antiferromagnet BaNiSbO
We report the results of magnetization and specific heat measurements on
BaNiSbO, which is a quasi-two-dimensional spin-1 triangular-lattice
antiferromagnet. We observed a nonclassical magnetization plateau at one-third
of the saturation magnetization that is driven by spin frustration and quantum
fluctuation. Exact diagonalization for a 21-site rhombic cluster was performed
to analyze the magnetization process. Experimental and calculated results agree
well.Comment: published in Journal of the Physical Society of Japan 80 (2011)
09370
The Optical/Near-Infrared Light Curves of SN 2002ap for the First 140 Days after Discovery
Supernova (SN) 2002ap in M74 was observed in the bands for the
first 40 days following its discovery (2002 January 29) until it disappeared
because of solar conjunction, and then in June after it reappeared. The
magnitudes and dates of peak brightness in each band were determined. While the
rate of increase of the brightness before the peak is almost independent of
wavelength, the subsequent rate of decrease becomes smaller with wavelength
from the to the band, and is constant at wavelengths beyond . The
photometric evolution is faster than in the well-known ``hypernovae''
SNe~1998bw and 1997ef, indicating that SN 2002ap ejected less mass. The
bolometric light curve of SN 2002ap for the full period of observations was
constructed. The absolute magnitude is found to be much fainter than that of SN
1998bw, but is similar to that of SN 1997ef, which lies at the faint end of the
hypernova population. The bolometric light curve at the early epochs was best
reproduced with the explosion of a C+O star that ejects 2.5~M_\sun with
kinetic energy . A comparison of the
predicted brightness of SN 2002ap with that observed after solar conjunction
may imply that -ray deposition at the later epochs was more efficient
than in the model. This may be due to an asymmetric explosion.Comment: 15 pages, 6 figures, quality of figure1 is reduced for smaller
filesize, accepted for publication in Ap
Electronic States and Superconducting Transition Temperature based on the Tomonaga-Luttinger liquid in PrBaCuO
An NQR experiment revealed superconductivity of
PrBaCuO (Pr247) to be realized on CuO double chain
layers and suggests possibility of novel one-dimensional(1D) superconductivity.
To clarify the nature of the 1D superconductivity, we calculate the band
dispersions of Pr247 by using the generalized gradient approximation(GGA). It
indicates that Fermi surface of CuO double chains is well described to the
electronic structure of a quasi-1D system.
Assuming the zigzag Hubbard chain model to be an effective model of the
system, we derive tight binding parameters of the model from a fit to the
result of GGA. Based on the Tomonaga-Luttinger liquid theory, we estimate
transition temperature () of the quasi-1D zigzag Hubbard model from the
calculated value of the Luttinger liquid parameter . The result of
is consistent with that of experiments in Pr247 and it suggests that the
mechanism of the superconductivity is well understood within the concept of the
Tomonaga-Luttinger liquid.Comment: 4 pages, 5 figure
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