61,938 research outputs found

### Determining the Supernova Direction by its Neutrinos

Supernova neutrinos, which arrive at Earth earlier than light, allow for the
earliest determination of the direction of the supernova. The topic of this
paper is to study how accurately we can determine the supernova direction. We
simulate supernova neutrino events at the SuperKamiokande detector, using a
realistic supernova model and several realistic neutrino oscillation models.
With the results of our simulation, we can restrict the supernova direction to
be within a circle of radius $9^\circ$. In several neutrino oscillation models,
this accuracy is increased to $8^\circ$. We also discuss the influence of an
accident that occurred at the SuperKamiokande detector. After repair of the
detector, using the remaining PMTs, the accuracy becomes about $12^\circ$ for
no oscillation.Comment: 20 pages, 8 figures, Prog. Theor. Phys., accepte

### Phase Diagram of Gross-Neveu Model at Finite Temperature, Density and Constant Curvature

We discuss a phase structure of chiral symmetry breaking in the Gross-Neveu
model at finite temperature, density and constant curvature. The effective
potential is evaluated in the leading order of the $1/N$-expansion and in a
weak curvature approximation. The third order critical line is found on the
critical surface in the parameter space of temperature, chemical potential and
constant curvature.Comment: 11 pages, Latex. 3 figures (eps files

### Step Bunching with Alternation of Structural Parameters

By taking account of the alternation of structural parameters, we study
bunching of impermeable steps induced by drift of adatoms on a vicinal face of
Si(001). With the alternation of diffusion coefficient, the step bunching
occurs irrespective of the direction of the drift if the step distance is
large. Like the bunching of permeable steps, the type of large terraces is
determined by the drift direction. With step-down drift, step bunches grows
faster than those with step-up drift. The ratio of the growth rates is larger
than the ratio of the diffusion coefficients. Evaporation of adatoms, which
does not cause the step bunching, decreases the difference. If only the
alternation of kinetic coefficient is taken into account, the step bunching
occurs with step-down drift. In an early stage, the initial fluctuation of the
step distance determines the type of large terraces, but in a late stage, the
type of large terraces is opposite to the case of alternating diffusion
coefficient.Comment: 8pages, 16 figure

### Intersecting D-brane states derived from the KP theory

A general scheme to find tachyon boundary states is developed within the
framework of the theory of KP hierarchy. The method is applied to calculate
correlation function of intersecting D-branes and rederived the results of our
previous works as special examples. A matrix generalization of this scheme
provides a method to study dynamics of coincident multi D-branes.Comment: 10 page

### Pion Production Model - Connection between Dynamics and Quark Models

We discuss the difficulties in testing the hadron models by using the N^*
parameters extracted from the empirical amplitude analyses of the pi-N and
gamma-N reaction data. As an alternative or perhaps a more advantageous
approach, we present a Hamiltonian formulation that can relate the pion
production dynamics and the constituent quark models of N^* structure. The
application of the approach in investigating the Delta and N^*(S_{11})
excitations is reviewed. It is found that while the Delta excitation can be
described satisfactory, the pi-N scattering in S_{11} channel can not be
described by the constituent quark models based on either the
one-gluon-exchange or one-meson-exchange mechanisms. A phenomenological
quark-quark potential has been constructed to reproduce the S_{11} amplitude.Comment: 11 pages, 4 figures, to be published in Proceedings of NSTAR2000
workshop held at Jefferson Laboratory, Feb., 200

### Monitoring of the MU radar antenna pattern by Satellite Ohzora (EXOS-C)

As the first attempt among MST (mesosphere stratosphere troposphere) type radars, the MU (middle and upper atmosphere) radar features an active phased array system. Unlike the conventional large VHF radars, in which output power of a large vacuum tube is distributed to individual antenna elements, each of 475 solid state power amplifier feeds each antenna element. This system configuration enables very fast beam steering as well as various flexible operations by dividing the antenna into independent subarrays, because phase shift and signal division/combination are performed at a low signal level using electronic devices under control of a computer network. The antenna beam can be switched within 10 microsec to any direction within the zenith angle of 30 deg. Since a precise phase alignment of each element is crucial to realize the excellent performance of this system, careful calibration of the output phase of each power amplifier and antenna element was carried out. Among various aircraft which may be used for this purpose artificial satellites have an advantage of being able to make a long term monitoring with the same system. An antenna pattern monitoring system for the MU radar was developed using the scientific satellite OHZORA (EXOS-C). A receiver named MUM (MU radar antenna Monitor) on board the satellite measures a CW signal of 100 to 400 watts transmitted from the MU radar. The principle of the measurement and results are discussed

### Point interactions in one dimension and holonomic quantum fields

We introduce and study a family of quantum fields, associated to
delta-interactions in one dimension. These fields are analogous to holonomic
quantum fields of M. Sato, T. Miwa and M. Jimbo. Corresponding field operators
belong to an infinite-dimensional representation of the group SL(2,\Rb) in
the Fock space of ordinary harmonic oscillator. We compute form factors of such
fields and their correlation functions, which are related to the determinants
of Schroedinger operators with a finite number of point interactions. It is
also shown that these determinants coincide with tau functions, obtained
through the trivialization of the $\mathrm{det}^*$-bundle over a Grassmannian
associated to a family of Schroedinger operators.Comment: 17 page

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