670 research outputs found
Periodicity and criticality in the Olami-Feder-Christensen model of earthquakes
Characteristic versus critical features of earthquakes are studied on the
basis of the Olami-Feder-Christensen model. It is found that the local
recurrence-time distribution exhibits a sharp -function-like peak
corresponding to rhythmic recurrence of events with a fixed ``period'' uniquely
determined by the transmission parameter of the model, together with a
power-law-like tail corresponding to scale-free recurrence of events. The model
exhibits phenomena closely resembling the asperity known in seismology
Zone diagrams in Euclidean spaces and in other normed spaces
Zone diagrams are a variation on the classical concept of Voronoi diagrams. Given n sites in a metric space that compete for territory, the zone diagram is an equilibrium state in the competition. Formally it is defined as a fixed point of a certain "dominance” map. Asano, Matoušek, and Tokuyama proved the existence and uniqueness of a zone diagram for point sites in the Euclidean plane, and Reem and Reich showed existence for two arbitrary sites in an arbitrary metric space. We establish existence and uniqueness for n disjoint compact sites in a Euclidean space of arbitrary (finite) dimension, and more generally, in a finite-dimensional normed space with a smooth and rotund norm. The proof is considerably simpler than that of Asano etal. We also provide an example of non-uniqueness for a norm that is rotund but not smooth. Finally, we prove existence and uniqueness for two point sites in the plane with a smooth (but not necessarily rotund) nor
Equivalence Classes of Boundary Conditions in Gauge Theory on Orbifold
We study equivalence classes of boundary conditions in gauge theory on the
orbifold . Orbifold conditions and those gauge transformation
properties are given and the gauge equivalence is understood by the Hosotani
mechanism. Mode expansions are carried out for six-dimensional singlet
fields and a triplet field, and the one-loop effective potential for
Wilson line phases is calculated.Comment: PTPTEX,17 page
Search for a Realistic Orbifold Grand Unification
We review the prototype model of a grand unified theory on the orbifold
and discuss topics related to the choice of boundary conditions; the
dynamical rearrangement of gauge symmetry and the equivalence classes of BCs.
We explore a family unification scenario by orbifolding.Comment: 19 pages, 4 figures, to appear in the proceeding of International
Workshop on Grand Unified Theories: Current Status and Future Prospects
(GUT07), December 17-19 2007, Kusatsu, Japa
Distance k-Sectors Exist
The bisector of two nonempty sets P and Q in a metric space is the set of all
points with equal distance to P and to Q. A distance k-sector of P and Q, where
k is an integer, is a (k-1)-tuple (C_1, C_2, ..., C_{k-1}) such that C_i is the
bisector of C_{i-1} and C_{i+1} for every i = 1, 2, ..., k-1, where C_0 = P and
C_k = Q. This notion, for the case where P and Q are points in Euclidean plane,
was introduced by Asano, Matousek, and Tokuyama, motivated by a question of
Murata in VLSI design. They established the existence and uniqueness of the
distance trisector in this special case. We prove the existence of a distance
k-sector for all k and for every two disjoint, nonempty, closed sets P and Q in
Euclidean spaces of any (finite) dimension, or more generally, in proper
geodesic spaces (uniqueness remains open). The core of the proof is a new
notion of k-gradation for P and Q, whose existence (even in an arbitrary metric
space) is proved using the Knaster-Tarski fixed point theorem, by a method
introduced by Reem and Reich for a slightly different purpose.Comment: 10 pages, 5 figure
Asperity characteristics of the Olami-Feder-Christensen model of earthquakes
Properties of the Olami-Feder-Christensen (OFC) model of earthquakes are
studied by numerical simulations. The previous study indicated that the model
exhibits ``asperity''-like phenomena, {\it i.e.}, the same region ruptures many
times near periodically [T.Kotani {\it et al}, Phys. Rev. E {\bf 77}, 010102
(2008)]. Such periodic or characteristic features apparently coexist with
power-law-like critical features, {\it e.g.}, the Gutenberg-Richter law
observed in the size distribution. In order to clarify the origin and the
nature of the asperity-like phenomena, we investigate here the properties of
the OFC model with emphasis on its stress distribution. It is found that the
asperity formation is accompanied by self-organization of the highly
concentrated stress state. Such stress organization naturally provides the
mechanism underlying our observation that a series of asperity events repeat
with a common epicenter site and with a common period solely determined by the
transmission parameter of the model. Asperity events tend to cluster both in
time and in space
ABO-incompatible living-donor pediatric kidney transplantation in Japan
The Japanese ABO-Incompatible Transplantation Committee officially collected and analyzed data on pediatric ABO-incompatible living-donor kidney transplantation in July 2012. The age of a child was defined a
Physically Consistent Preferential Bayesian Optimization for Food Arrangement
This paper considers the problem of estimating a preferred food arrangement
for users from interactive pairwise comparisons using Computer Graphics
(CG)-based dish images. As a foodservice industry requirement, we need to
utilize domain rules for the geometry of the arrangement (e.g., the food layout
of some Japanese dishes is reminiscent of mountains). However, those rules are
qualitative and ambiguous; the estimated result might be physically
inconsistent (e.g., each food physically interferes, and the arrangement
becomes infeasible). To cope with this problem, we propose Physically
Consistent Preferential Bayesian Optimization (PCPBO) as a method that obtains
physically feasible and preferred arrangements that satisfy domain rules. PCPBO
employs a bi-level optimization that combines a physical simulation-based
optimization and a Preference-based Bayesian Optimization (PbBO). Our
experimental results demonstrated the effectiveness of PCPBO on simulated and
actual human users.Comment: 8 pages, 10 figures, accepted by IEEE Robotics and Automation Letters
(RA-L) 202
Finite spin-glass transition of the XY model in three dimensions
A three-dimensional XY spin-glass model is investigated by a
nonequilibrium relaxation method. We have introduced a new criterion for the
finite-time scaling analysis. A transition temperature is obtained by a
crossing point of obtained data. The scaling analysis on the relaxation
functions of the spin-glass susceptibility and the chiral-glass susceptibility
shows that both transitions occur simultaneously. The result is checked by
relaxation functions of the Binder parameters and the glass correlation lengths
of the spin and the chirality. Every result is consistent if we consider that
the transition is driven by the spin degrees of freedom.Comment: 11 pages, 8 figures, incorrect arguments are delete
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