343 research outputs found
Running Boundary Condition
In this paper we argue that boundary condition may run with energy scale. As
an illustrative example, we consider one-dimensional quantum mechanics for a
spinless particle that freely propagates in the bulk yet interacts only at the
origin. In this setting we find the renormalization group flow of U(2) family
of boundary conditions exactly. We show that the well-known scale-independent
subfamily of boundary conditions are realized as fixed points. We also discuss
the duality between two distinct boundary conditions from the renormalization
group point of view. Generalizations to conformal mechanics and quantum graph
are also discussed.Comment: PTPTeX, 21 pages, 8 eps figures; typos corrected, references and an
appendix adde
Many-Brane Extention of the Randall-Sundrum Solution
Recently, Randall and Sundrum proposed a static solution to Einstein's
equations in five spacetime dimensions with two 3-branes located at the fixed
points of to solve the hierarchy problem. We extend the solution and
construct static and also inflationary solutions to Einstein's equations in
five spacetime dimensions, one of which is compactified on , with any
number of 3-branes whose locations are taken to be arbitrary. We discuss how
the hierarchy problem can be explained in our model.Comment: PTPTeX 1.0(preprint style), 8 pages, no figures, references and typos
correcte
Spontaneous Supersymmetry Breaking from Extra Dimensions
We propose a new spontaneous supersymmetry breaking mechanism, in which extra
compact dimensions play an important role. To illustrate our mechanism, we
study a simple model consisting of two chiral superfields, where one spatial
dimension is compactified on a circle . It is shown that supersymmetry is
spontaneously broken irrespective of the radius of the circle, and also that
the translational invariance for the -direction and a global symmetry are
spontaneously broken when the radius becomes larger than a critical radius.
These results are expected to be general features of our mechanism. We further
discuss that our mechanism may be observed as the O'Raifeartaigh type of
supersymmetry breaking at low energies.Comment: 10 pages, No figur
Spontaneously Broken Translational Invariance of Compactified Space
We propose a mechanism to break the translational invariance of compactified
space spontaneously. As a simple model, we study a real model
compactified on in detail, where we impose a nontrivial
boundary condition on for the -direction. It is shown that the
translational invariance for the -direction is spontaneously broken when
the radius of becomes larger than a critical radius and also
that the model behaves like a model on a single kink background for . It is pointed out that spontaneous breakdown of translational
invariance is accompanied by that of some global symmetries, in general, in our
mechanism.Comment: 9 pages, No figur
Epigenetic regulation of mammalian sex determination
Epigenetics is the study of changes in gene function that cannot be explained by changes in DNA sequence. A mammalian body contains more than two-hundred different types of cells, all derived from a single fertilized egg. Epigenetic gene regulation mechanisms essentially contribute to various processes of mammalian development. The essence of epigenetic regulation is the modulation of gene activity through changes in chromatin structure. DNA methylation and histone modifications are the major epigenetic mechanisms. Sex determination is the process of establishing a gender. Sry, the sex-determining gene in therian mammals, initiates testis differentiation. Recent studies have provided evidence that epigenetic mechanisms contribute to Sry regulation
Improvement of odometry for omnidirectional vehicle using optical flow information
Our research goal is to realize a robust navigation in indoor and outdoor environment for autonomous vehicle. An omnidirectional vehicle driven by four Mecanum wheels was chosen for our research platform. Mecanum wheel has 16 tilted rollers (45 degrees against the direction of wheel rotation) around the wheel, so the vehicle moves omnidirectionally by controlling these wheels independently. However, it has a disadvantage in odometry because of wheel slippage. Particularly, when the robot moves laterally, same wheels' rotations generate different traveling distance depending on friction of ground surface. To cope with the problem, we estimate robot's position by detecting optical flow of ground image using vision sensor (visual dead-reckoning). The estimation method is inaccurate comparing with odometry, but it is independent from friction of ground surface. Therefore, the estimated vehicle position can be improved by fusing odometry and visual dead-reckoning based on maximum likelihood technique. This paper describes an odometry method and a visual dead-reckoning method for omnidirectional vehicle, and fusion technique to improve the estimated position of the vehicle. Finally, experimental results support above technique </p
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