arXiv subjects
Publications and source records attributed to M. Kato.
We present the lattice models with exact fermionic symmetries relating fermions and link variables. The plaquettes are distributed in an Ichimatsu pattern (chequered). We explain this peculiar structure allows us to have a translation in the algebra of the fermionic symmetries.
We proposed an `Ichimatsu'-decomposed lattice gauge theory with fermionic symmetries. The vacuum structures of the gauge sector with two coupling constants ($β_p,β_c$) are investigated for 3-dimensional Z$_2$ and 4-dimensional SU(2) cases using mean-field approximation and numerical simulation. We found two phases on the ($β_p,β_c$) phase diagram for 3-dim. Z$_2$ case, while the diagram is a single phase for the latter.
High-resolution bulk-sensitive photoemission has been measured for pyrochlore oxide Cd2Re2O7. Temperature variations of the spectral shapes between 20 and 250 K are obviously observed for the Re 4f inner core and the valence band spectra. The Re 5d states are dominant for the DOS near the Fermi level.
We present a new lattice super Yang-Mills theory and its SUSY transformation. After our formulation of the model in a fundamental lattice, it is extended to the whole lattice with a substructure of modulo 2.
Differential and integral cross sections of the muon are calculated in the materials: water, standard rock, iron and lead with and without the LPM effect. The corresponding cross sections are also calculated with dielectric supression effect (Ter-Mikaelian effect), in addition to the LPM effect. To demonstrate the importance of the LPM effect in the bremsstrahlung process, depth intensity relation of muon, energy spectrum, range distribution and survival probability are calculated taking into account bremsstrahlung spectrum.
Observations suggest that the properties of Type Ia supernovae (SNe Ia) may depend on environmental characteristics, such as morphology, metallicity, and age of host galaxies. The influence of these environmental properties on the resulting SNe Ia is studied in this paper. First it is shown that the carbon mass fraction X(C) in the C+O white dwarf SN Ia progenitors tends to be smaller for lower metallicity and older the binary system age. It is then suggested that the variation of X(C) causes the diversity in the brightness of SNe Ia: a smaller X(C) leads to a dimmer SN Ia. Further studies of the propagation of the turbulent flame are necessary to confirm this relation. Our model for the SN Ia progenitors then predicts that when the progenitors belong to an older population or to a low metallicity environment, the number of bright SNe Ia is reduced, so that the variation in brightness among the SNe Ia is also smaller. Thus our model can explain why the mean SN Ia brightness and its dispersion depend on the morphology of the host galaxies and on the distance of the SN from the center of the galaxy. It is further predicted that at higher redshift (z >~ 1) both the the mean brightness of SNe Ia and its variation should be smaller in spiral galaxies than in elliptical galaxies. These variations are within the range observed in nearby SNe Ia. In so far as the variation in X(C) is the most important cause for the diversity among SNe Ia, the light curve shape method currently used to determine the absolute magnitude of SNe Ia can be applied also to high redshift SNe Ia.
We have calculated the mass accumulation efficiency during helium shell flashes to examine whether or not a carbon-oxygen white dwarf (C+O WD) grows up to the Chandrasekhar mass limit to ignite a Type Ia supernova explosion. It has been frequently argued that luminous super-soft X-ray sources and symbiotic stars are progenitors of SNe Ia. In such systems, a C+O WD accretes hydrogen-rich matter from a companion and burns hydrogen steadily on its surface. The WD develops a helium layer underneath the hydrogen-rich envelope and undergoes periodic helium shell flashes. Using OPAL opacity, we have reanalyzed a full cycle of helium shell flashes on a 1.3 M_\odot C+O WD and confirmed that the helium envelope of the WD expands to blow a strong wind. A part of the accumulated matter is lost by the wind. The mass accumulation efficiency is estimated as η_{He} = -0.175 (\log \dot M + 5.35)^2 + 1.05, for -7.3 < \log \dot M < -5.9, where the mass accretion rate \dot M is in units of M_\odot yr^{-1}. In relatively high mass accretion rates as expected in recent SN Ia progenitor models, the mass accumulation efficiency is large enough for C+O WDs to grow to the Chandrasekhar mass, i.e., η_{He} = 0.9 for \log \dot M = -6.3, and η_{He}=0.57 for \log \dot M = -7.0. The wind velocity (\sim 1000 km/s) is much faster than the orbital velocity of the binary (< 300 km/s) and therefore, the wind cannot be accelerated further by the companion's motion.
We report on a global CCD time-series photometric campaign to decode the pulsations of the nucleus of the planetary nebula NGC1501. The star is hot and hydrogen-deficient, similar to the pre-white-dwarf PG 1159 stars. NGC1501 shows pulsational brightness variations of a few percent with periods ranging from 19 to 87 minutes. The variations are very complex, suggesting a pulsation spectrum that requires a long unbroken time series to resolve. Our CCD photometry of the star covers a two-week period in 1991 November, and used a global network of observatories. We obtained nearly continuous coverage over an interval of one week in the middle of the run. We have identified 10 pulsation periods, ranging from 5235 s down to 1154 s. We find strong evidence that the modes are indeed nonradial g-modes. The ratios of the frequencies of the largest-amplitude modes agree with those expected for modes that are trapped by a density discontinuity in the outer layers. We offer a model for the pulsation spectrum that includes a common period spacing of 22.3 s and a rotation period of 1.17 days; the period spacing allows us to assign a seismological mass of 0.55+/-0.03 Msun.
The discrete states in the $c=1$ string are shown to be the physical states of a certain topological sigma model. We define a set of new fields directly from $c=1$ variables, in terms of which the BRST charge and energy-momentum tensor are rewritten as those of the topological sigma model. Remarkably, ground ring generator $x$ turns out to be a coordinate of the sigma model. All of the discrete states realize a graded ring which contains ground ring as a subset.
A similarity transformation, which brings a particular class of the $N=1$ string to the $N=0$ one, is explicitly constructed. It enables us to give a simple proof for the argument recently proposed by Berkovits and Vafa. The $N=1$ BRST operator is turned into the direct sum of the corresponding $N=0$ BRST operator and that for an additional topological sector. As a result, the physical spectrum of these $N=1$ vacua is shown to be isomorphic to the tensor product of the $N=0$ spectrum and the topological sector which consists of only the vacuum. This transformation manifestly keeps the operator algebra.