143,258 research outputs found
The ground state and the long-time evolution in the CMC Einstein flow
Let (g,K)(k) be a CMC (vacuum) Einstein flow over a compact three-manifold M
with non-positive Yamabe invariant (Y(M)). As noted by Fischer and Moncrief,
the reduced volume V(k)=(-k/3)^{3}Vol_{g(k)}(M) is monotonically decreasing in
the expanding direction and bounded below by V_{\inf}=(-1/6)Y(M))^{3/2}.
Inspired by this fact we define the ground state of the manifold M as "the
limit" of any sequence of CMC states {(g_{i},K_{i})} satisfying: i. k_{i}=-3,
ii. V_{i} --> V_{inf}, iii. Q_{0}((g_{i},K_{i}))< L where Q_{0} is the
Bel-Robinson energy and L is any arbitrary positive constant. We prove that (as
a geometric state) the ground state is equivalent to the Thurston
geometrization of M. Ground states classify naturally into three types. We
provide examples for each class, including a new ground state (the Double Cusp)
that we analyze in detail. Finally consider a long time and cosmologically
normalized flow (\g,\K)(s)=((-k/3)^{2}g,(-k/3))K) where s=-ln(-k) is in
[a,\infty). We prove that if E_{1}=E_{1}((\g,\K))< L (where E_{1}=Q_{0}+Q_{1},
is the sum of the zero and first order Bel-Robinson energies) the flow
(\g,\K)(s) persistently geometrizes the three-manifold M and the geometrization
is the ground state if V --> V_{inf}.Comment: 40 pages. This article is an improved version of the second part of
the First Version of arXiv:0705.307
A generic application for corpus management and administration
Our corpus project is building a digital collection of both written and spoken texts. The corpus is a publicly available resource, mounted on and searchable via the Web.
This paper will describe the corpus management and workflow administration methods that the project has developed and the technologies used. We believe that the structures we have created to manage the different parts of the administration of the project are the basis for a re-usable, generic package for scholars building an online corpus from new linguistic materials
Determination of the masses of the Moon and Venus and the astronomical unit from radio tracking data of the Mariner II SPACECRAFT
Masses of Venus and Moon, and astronomical unit determined by Mariner II radio tracking dat
Experimental tests of relativistic gravitation theories
Experimental tests were studied for determining the potential uses of future deep space missions in studies of relativistic gravity. The extensions to the parametrized post-Newtonian framework to take explicit account of the solar system's center of mass relative to the mean rest frame of the Universe is reported. Discoveries reported include the Machian effects of motion relative to the universal rest frame. Summaries of the JPL research are included
M-1 engine test complex data acquisition systems
Instrumentation and data acquisition system for development testing of liquid hydrogen/liquid oxygen M-1 rocket engin
Evaluation of postural mechanisms under dynamic conditions
A stimulus delivery and data acquisition system for assessment of human posture was developed based on a digital computer and a translating platform. The movement of the platform acts to displace the subject's base of support while the computer tracks the corrections which are made by the subject to maintain balance. Various stimuli are used ranging from fast transients to sine waves
Development of methodologies for vestibular experimentation with man and animals
Calculations on the possibilities for an animal centrifuse which will be useful in the study of the otolith organs in space research are presented with discussion on the design of such a centrifuse
Properties of the Scalar Universal Equations
The variational properties of the scalar so--called ``Universal'' equations
are reviewed and generalised. In particular, we note that contrary to earlier
claims, each member of the Euler hierarchy may have an explicit field
dependence. The Euler hierarchy itself is given a new interpretation in terms
of the formal complex of variational calculus, and is shown to be related to
the algebra of distinguished symmetries of the first source form.Comment: 15 pages, LaTeX articl
A Mission to Test the Pioneer Anomaly
Analysis of the radio tracking data from the Pioneer 10/11 spacecraft has
consistently indicated the presence of an anomalous small Doppler frequency
drift. The drift can be interpreted as being due to a constant acceleration of
a_P= (8.74 +/- 1.33) x 10^{-8} cm/s^2 directed towards the Sun. Although it is
suspected that there is a systematic origin to the effect, none has been found.
The nature of this anomaly has become of growing interest in the fields of
relativistic cosmology, astro- and gravitational physics as well as in the
areas of spacecraft design and high-precision navigation. We present a concept
for a designated deep-space mission to test the discovered anomaly. A number of
critical requirements and design considerations for such a mission are outlined
and addressed.Comment: Final changes for publication. Honorable Mention, 2002 Gravity
Research Foundation Essay
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