560 research outputs found
Zero-dimensional analogue of the global gauge anomaly
A zero-dimensional analogue of Witten's global gauge anomaly is considered.
For example, a zero-dimensional reduction of the two-dimensional \SO(2N)
Yang-Mills theory with a single Majorana-Weyl fermion in the fundamental
representation suffers from this anomaly. Another example is a zero-dimensional
reduction of two- and three-dimensional \SU(2N_c) Yang-Mills theories which
couple to a single Majorana fermion in the adjoint representation. In this
case, any expectation value is either indeterminate or infinite.Comment: 6 pages, uses PTPTeX.cls, the final version to appear in Prog. Theor.
Phy
Non-Adiabatic Transition in Spin-Boson Model and Generalization of the Landau-Zener Formula
Non-adiabatic transitions are studied in a spin-boson model with multiple
scattering points. In order to generalize the Landau-Zener formula, which
describes the case of a single scattering point, we define an ``effective gap''
for a set of scattering points. The generalized formula agrees very well with
numerical results of the non-adiabatic dynamics, which we obtained by a direct
numerical method. This will make the Landau-Zener formula yet more useful in
analyzing experimental data of magnetic-moment inversion.Comment: 17 pages, 18 figure
Frequency Distribution of Intense Rainfall in the Wards of Tokyo and Its Relationship with the Spatial Structure of Building Heights
This study presents the minute spatial structure of both the frequency of intense rainfall (data from the 1991 to 2002, except 1993, were used) and recent trends (15-25 years until 2002) in the special wards of the Tokyo Metropolis in summer (June to September), on the basis of hourly rainfall data from a dense rain-gauge network. As this is the first step in elucidating the relationship between the distribution of the frequency of intense rainfall and that of surface roughness in metropolitan Tokyo, the averaged number of building stories within a certain area, which is referred to as the smoothed building height (SBH), was assumed to be an alternative parameter when deciding surface roughness. The distribution of the ascending rate of SBH (hereafter, the ascending rate of SBH is referred to as ARS) for wind direction was calculated by varying the averaging area for SBH, in order to compare it to the distribution of intense rainfall frequency. The results are summarized as follows. The high-frequency areas of intense rainfall appear in the western to northern parts of the area comprising the wards and along the boundary between the Tokyo Metropolis and SaitamaPrefecture. The frequency of intense rainfall in these areas is two to three times as high as that in the eastern part of the area comprising the wards. Moreover, the maximum areas of intense rainfall frequency are localized in the western, northern to northwestern, and southern part of the area comprising the wards, corresponding to wind direction. These areas are situated 3-5 km from the leeward side of the area, where the ARS derived from the SBH at a 1-2 km scale islarge, that is, the vicinities of Shinjuku (SNJ), Ikebukuro (1KB), and Shibuya (SBY). Accordingly, we suggest that the large surface roughness due to high-rise buildings in the western part of the area comprising the wards has the effect of increasing the frequency of intense rainfall. The increasing trend of intense rainfall is clear in the western part of the area comprising the wards, whereas a decreasing trend, although not statistically significant, is seen in the eastern part of the area comprising the wards. It is noted that observational stations with large increasing trends of intense rainfall, such as Nakano (NKN) and Shinagawa (SNG), are located 3-5 km from the leeward side of SNJ and on the shore of Tokyo Bay in the southern part of the area comprising the wards, respectively, where the ARS for easterly winds derived from the SBH at a 1-2 km scale is large
Discovery of antiferromagnetic chiral helical ordered state in trigonal GdNiGa
We have performed magnetic susceptibility, magnetization, and specific heat
measurements on a chiral magnet GdNiGa, belonging to the trigonal space
group (\#155). A magnetic phase transition takes place at =
19.5 K. By applying a magnetic field along the axis at 2 K, the
magnetization curve exhibits two jumps at 3 kOe and = 45 kOe. To
determine the magnetic structure, we performed a resonant X-ray diffraction
experiment by utilizing a circularly polarized beam. It is shown that a
long-period antiferromagnetic (AFM) helical order is realized at zero field.
The Gd spins in the honeycomb layer are coupled in an antiferromagnetic manner
in the plane and rotate with a propagation vector = (0, 0, 1.485). The
period of the helix is 66.7 unit cells (~nm). In magnetic fields
above 3~kOe applied perpendicular to the helical axis, the AFM helical
order changes to an AFM order with = (0, 0, 1.5).Comment: 7 pages, 12 figure
Seasonal Changes in the Amount of Litter Layer and Soil Erosion in the Forest Floor - an Impoverished Understory by Deer Impact at Doudaira, Tanzawa Mountains
Overlap lattice fermion in a gravitational field
We construct a lattice Dirac operator of overlap type that describes the
propagation of a Dirac fermion in an external gravitational field. The local
Lorentz symmetry is manifestly realized as a lattice gauge symmetry, while it
is believed that the general coordinate invariance is restored only in the
continuum limit. Our doubler-free Dirac operator satisfies the conventional
Ginsparg-Wilson relation and possesses gamma_5 hermiticity with respect to the
inner product, which is suggested by the general coordinate invariance. The
lattice index theorem in the presence of a gravitational field holds, and the
classical continuum limit of the index density reproduces the Dirac genus.
Reduction to a single Majorana fermion is possible for 8k+2 and 8k+4
dimensions, but not for 8k dimensions, which is consistent with the existence
of the global gravitational/gauge anomalies in 8k dimensions. Other Lorentz
representations, such as the spinor-vector and the bi-spinor representations,
can also be treated. Matter fields with a definite chirality (with respect to
the lattice-modified chiral matrix) are briefly considered.Comment: 22 pages, uses PTPTeX.cls, the final version to appear in Prog.
Theor. Phy
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