4,440 research outputs found
Flat 3-webs of degree one on the projective plane
The aim of this work is to study global -webs with vanishing curvature. We
wish to investigate degree foliations for which their dual web is flat. The
main ingredient is the Legendre transform, which is an avatar of classical
projective duality in the realm of differential equations. We find a
characterization of degree foliations whose Legendre transform are webs
with zero curvature.Comment: 14 page
Multi-site H-bridge breathers in a DNA--shaped double strand
We investigate the formation process of nonlinear vibrational modes
representing broad H-bridge multi--site breathers in a DNA--shaped double
strand.
Within a network model of the double helix we take individual motions of the
bases within the base pair plane into account. The resulting H-bridge
deformations may be asymmetric with respect to the helix axis. Furthermore the
covalent bonds may be deformed distinctly in the two backbone strands.
Unlike other authors that add different extra terms we limit the interaction
to the hydrogen bonds within each base pair and the covalent bonds along each
strand. In this way we intend to make apparent the effect of the characteristic
helicoidal structure of DNA. We study the energy exchange processes related
with the relaxation dynamics from a non-equilibrium conformation. It is
demonstrated that the twist-opening relaxation dynamics of a radially distorted
double helix attains an equilibrium regime characterized by a multi-site
H-bridge breather.Comment: 27 pages and 10 figure
Invariant Connections with Torsion on Group Manifolds and Their Application in Kaluza-Klein Theories
Invariant connections with torsion on simple group manifolds are studied
and an explicit formula describing them is presented. This result is used for
the dimensional reduction in a theory of multidimensional gravity with
curvature squared terms on . We calculate the potential of
scalar fields, emerging from extra components of the metric and torsion, and
analyze the role of the torsion for the stability of spontaneous
compactification.Comment: 13 pages, LATEX, UB-ECM-PF 93/1
The end-to-end testbed of the Optical Metrology System on-board LISA Pathfinder
LISA Pathfinder is a technology demonstration mission for the Laser
Interferometer Space Antenna (LISA). The main experiment on-board LISA
Pathfinder is the so-called LISA Technology Package (LTP) which has the aim to
measure the differential acceleration between two free-falling test masses with
an accuracy of 3x10^(-14) ms^(-2)/sqrt[Hz] between 1 mHz and 30 mHz. This
measurement is performed interferometrically by the Optical Metrology System
(OMS) on-board LISA Pathfinder. In this paper we present the development of an
experimental end-to-end testbed of the entire OMS. It includes the
interferometer and its sub-units, the interferometer back-end which is a
phasemeter and the processing of the phasemeter output data. Furthermore,
3-axes piezo actuated mirrors are used instead of the free-falling test masses
for the characterisation of the dynamic behaviour of the system and some parts
of the Drag-free and Attitude Control System (DFACS) which controls the test
masses and the satellite. The end-to-end testbed includes all parts of the LTP
that can reasonably be tested on earth without free-falling test masses. At its
present status it consists mainly of breadboard components. Some of those have
already been replaced by Engineering Models of the LTP experiment. In the next
steps, further Engineering Models and Flight Models will also be inserted in
this testbed and tested against well characterised breadboard components. The
presented testbed is an important reference for the unit tests and can also be
used for validation of the on-board experiment during the mission
Knudsen Effect in a Nonequilibrium Gas
From the molecular dynamics simulation of a system of hard-core disks in
which an equilibrium cell is connected with a nonequilibrium cell, it is
confirmed that the pressure difference between two cells depends on the
direction of the heat flux. From the boundary layer analysis, the velocity
distribution function in the boundary layer is obtained. The agreement between
the theoretical result and the numerical result is fairly good.Comment: 4pages, 4figure
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