16,209 research outputs found
The Anisotropy in the Cosmic Microwave Background At Degree Angular Scales
We detect anisotropy in the cosmic microwave background (CMB) at degree
angular scales and confirm a previous detection reported by Wollack et al.
(1993). The root-mean-squared amplitude of the fluctuations is K. This may be expressed as the square root of the angular power spectrum
in a band of multipoles between . We find K. The measured spectral
index of the fluctuations is consistent with zero, the value expected for the
CMB. The spectral index corresponding to Galactic free-free emission, the most
likely foreground contaminant, is rejected at approximately .
The analysis is based on three independent data sets. The first, taken in
1993, spans the 26 - 36 GHz frequency range with three frequency bands; the
second was taken with the same radiometer as the first but during an
independent observing campaign in 1994; and the third, also take in 1994, spans
the 36-46 GHz range in three bands. For each telescope position and radiometer
channel, the drifts in the instrument offset are K/day over a period
of one month. The dependence of the inferred anisotropy on the calibration and
data editing is addressed.Comment: 16 pages, 2 figures. Saskatoon 1993/1994 combined analysi
Software Engineering Laboratory (SEL). Data base organization and user's guide, revision 1
The structure of the Software Engineering Laboratory (SEL) data base is described. It defines each data base file in detail and provides information about how to access and use the data for programmers and other users. Several data base reporting programs are described also
Diversity-induced resonance in a system of globally coupled linear oscillators
The purpose of this paper to analyze in some detail the arguably simplest
case of diversity-induced reseonance: that of a system of globally-coupled
linear oscillators subjected to a periodic forcing. Diversity appears as the
parameters characterizing each oscillator, namely its mass, internal frequency
and damping coefficient are drawn from a probability distribution. The main
ingredients for the diversity-induced-resonance phenomenon are present in this
system as the oscillators display a variability in the individual responses but
are induced, by the coupling, to synchronize their responses. A steady state
solution for this model is obtained. We also determine the conditions under
which it is possible to find a resonance effect.Comment: Reported at the XI International Workshop "Instabilities and
Nonequilibrium Structures" Vina del Mar (Chile
Black Hole Motion in Entropic Reformulation of General Relativity
We consider a system of black holes -- a simplest substitute of a system of
point particles in the mechanics of general relativity -- and try to describe
their motion with the help of entropic action: a sum of the areas of black hole
horizons. We demonstrate that such description is indeed consistent with the
Newton's laws of motion and gravity, modulo numerical coefficients, which
coincide but seem different from unity. Since a large part of the modern
discussion of entropic reformulation of general relativity is actually based on
dimensional considerations, for making a next step it is crucially important to
modify the argument, so that these dimensionless parameters acquire correct
values.Comment: 6 page
Measuring software technology
Results are reported from a series of investigations into the effectiveness of various methods and tools used in a software production environment. The basis for the analysis is a project data base, built through extensive data collection and process instrumentation. The project profiles become an organizational memory, serving as a reference point for an active program of measurement and experimentation on software technology
Locating Overlap Information in Quantum Systems
When discussing the black hole information problem the term ``information
flow'' is frequently used in a rather loose fashion. In this article I attempt
to make this notion more concrete. I consider a Hilbert space which is
constructed as a tensor product of two subspaces (representing for example
inside and outside the black hole). I discuss how the system has the capacity
to contain information which is in NEITHER of the subspaces. I attempt to
quantify the amount of information located in each of the two subspaces, and
elsewhere, and analyze the extent to which unitary evolution can correspond to
``information flow''. I define the notion of ``overlap information'' which
appears to be well suited to the problem.Comment: 25 pages plain LaTeX, no figures. Imperial/TP/93-94/2
Gravitational Theory with a Dynamical Time
A gravitational theory involving a vector field , whose zero
component has the properties of a dynamical time, is studied. The variation of
the action with respect to gives the covariant conservation of an
energy momentum tensor . Studying the theory in a
background which has killing vectors and killing tensors we find appropriate
shift symmetries of the field which lead to conservation laws. The
energy momentum that is the source of gravity is different
but related to and the covariant conservation of determines in general the vector field . When is chosen to be proportional to the metric, the theory
coincides with the Two Measures Theory, which has been studied before in
relation to the Cosmological Constant Problem. When the matter model consists
of point particles, or strings, the form of , solutions for
are found. For the case of a string gas cosmology, we find that
the Milne Universe can be a solution, where the gas of strings does not curve
the spacetime since although , , as a model for the early universe, this solution is also free
of the horizon problem. There may be also an application to the "time problem"
of quantum cosmology.Comment: 21 pages, discussions extended, some more explicit proofs included,
more references include
GEMINGA'S SOFT X-RAY EMISSION AND THE STRUCTURE OF ITS SURFACE
We present a model to explain the decrease in the amplitude of the pulse
profile with increasing energy observed in Geminga's soft X-ray surface thermal
emission. We assume the presence of plates surrounded by a surface with very
distinct physical properties: these two regions emit spectra of very distinct
shapes which present a crossover, the warm plates emitting a softer spectrum
than the colder surrounding surface. The strongly pulsed emission from the
plates dominates at low energy while the surroundings emission dominates at
high energy, producing naturally a strong decrease in the pulsed fraction. In
our illustrative example the plates are assumed to be magnetized while the rest
of the surface is field free.
This plate structure may be seen as a schematic representation of a
continuous but very nonuniform distribution of the surface magnetic field or as
a quasi realistic structure induced by past tectonic activity on Geminga.Comment: 10 pages, AASTeX latex, + 3 figures (compressed 7 uuencoded).
Submitted to Ap. J. Let
The platinum nuclei: concealed configuration mixing and shape coexistence
The role of configuration mixing in the Pt region is investigated. For this
chain of isotopes, the nature of the ground state changes smoothly, being
spherical around mass and and deformed around the
mid-shell N=104 region. This has a dramatic effect on the systematics of the
energy spectra as compared to the systematics in the Pb and Hg nuclei.
Interacting Boson Model with configuration mixing calculations are presented
for gyromagnetic factors, -decay hindrance factors, and isotope shifts.
The necessity of incorporating intruder configurations to obtain an accurate
description of the latter properties becomes evident.Comment: Accepted in Physical Review
Numerical modeling of dynamic powder compaction using the Kawakita equation of state
Dynamic powder compaction is analyzed using the assumption that the powder behaves, while it is being compacted, like a hydrodynamic fluid in which deviatoric stress and heat conduction effects can be ignored throughout the process. This enables techniques of computational fluid dynamics such the equilibrium flux method to be used as a modeling tool. The equation of state of the powder under compression is assumed to be a modified version of the Kawakita loading curve. Computer simulations using this model are performed for conditions matching as closely as possible with those from experiments by Page and Killen [Powder Metall. 30, 233 (1987)]. The numerical and experimental results are compared and a surprising degree of qualitative agreement is observed
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