8,828 research outputs found
The Minimum Total Mass of MACHOs and Halo Models of the Galaxy
If the density distribution \rho (r) of MACHOs is spherically symmetric with
respect to the Galactic center, it is shown that the minimal total mass
M_{min}^{{ MACHO}} of the MACHOs is 1.7\times 10^{10}\sol \tau_{-6.7}^{{ LMC}}
where \tau_{-6.7}^{{ LMC}} is the optical depth (\tau^{{ LMC}}) toward the
Large Magellanic Cloud (LMC) in the unit of 2\times 10^{-7}. If \rho (r) is a
decreasing function of r, it is proved that M_{min}^{{ MACHO}} is 5.6\times
10^{10}\sol \tau_{-6.7}^{{ LMC}}. Several spherical and axially symmetric halo
models of the Galaxy with a few free parameters are also considered. It is
found that M_{min}^{{ MACHO}} ranges from 5.6\times 10^{10}\sol \tau_{-6.7}^{{
LMC}} to \sim 3 \times 10^{11}\sol \tau_{-6.7}^{{ LMC}}. For general case, the
minimal column density \Sigma_{min}^{{ MACHO}} of MACHOs is obtained as
\Sigma_{min}^{{ MACHO}} =25 \sol { pc}^{-2}\tau_{-6.7}^{{ LMC}}. If the clump
of MACHOs exist only halfway between LMC and the sun, M_{min}^{{ MACHO}} is
1.5\times 10^9\sol. This shows that the total mass of MACHOs is smaller than 5
\times 10^{10}\sol , i.e. \sim 10\% of the mass of the halo inside LMC, either
if the density distribution of MACHOs is unusual or \tau^{{ LMC}}\ll 2\times
10^{-7}.Comment: 5 pages, 5 Encapsulated PostScript figures, Latex, Accepted for
publication in Apj. Letter
Shape of Deconstruction
We construct a six-dimensional Maxwell theory using a latticized extra space,
the continuum limit of which is a shifted torus recently discussed by Dienes.
This toy model exhibits the correspondence between continuum theory and
discrete theory, and give a geometrical insight to theory-space model building.Comment: 10 pages, 2 figures, RevTeX4. a citation adde
Minimizing sum of completion times on a single machine with sequence-dependent family setup times
This paper presents a branch-and-bound (B&B) algorithm for minimizing the sum of completion times in a singlemachine scheduling setting with sequence-dependent family setup times. The main feature of the B&B algorithm is a new lower bounding scheme that is based on a networkformulation of the problem. With extensive computational tests, we demonstrate that the B&B algorithm can solve problems with up to 60 jobs and 12 families, where setup and processing times are uniformly distributed in various combinations of the [1,50] and [1,100] ranges
Theory of the Three-Group Evolutionary Minority Game
Based on the adiabatic theory for the evolutionary minority game (EMG) that
we proposed earlier[1], we perform a detail analysis of the EMG limited to
three groups of agents. We derive a formula for the critical point of the
transition from segregation (into opposing groups) to clustering (towards
cautious behaviors). Particular to the three-group EMG, the strategy switching
in the "extreme" group does not occur at every losing step and is strongly
intermittent. This leads to an correction to the critical value of the number
of agents at the transition, . Our expression for is in agreement
with the results obtained from our numerical simulations.Comment: 4 pages and 2 figure
The JPL telerobotic Manipulator Control and Mechanization (MCM) subsystem
The Manipulator Control and Mechanization (MCM) subsystem of the telerobot system provides the real-time control of the robot manipulators in autonomous and teleoperated modes and real time input/output for a variety of sensors and actuators. Substantial hardware and software are included in this subsystem which interfaces in the hierarchy of the telerobot system with the other subsystems. The other subsystems are: run time control, task planning and reasoning, sensing and perception, and operator control subsystem. The architecture of the MCM subsystem, its capabilities, and details of various hardware and software elements are described. Important improvements in the MCM subsystem over the first version are: dual arm coordinated trajectory generation and control, addition of integrated teleoperation, shared control capability, replacement of the ultimate controllers with motor controllers, and substantial increase in real time processing capability
Can Recovery-Oriented Mental Health Services be Created in Hong Kong? Struggles and Strategies
Recovery has been adopted as either the national policy or guiding principle for reforming mental health services in many countries. Development and implementation of the concept of recovery is still in its infancy in most Asian countries, and Hong Kong is no exception. The present authors propose three strategies to guide the transformation of Hong Kong mental health services toward becoming more recovery-oriented. © 2011 The Author(s).published_or_final_versio
X-ray Dichroism and the Pseudogap Phase of Cuprates
A recent polarized x-ray absorption experiment on the high temperature
cuprate superconductor Bi2Sr2CaCu2O8 indicates the presence of broken parity
symmetry below the temperature, T*, where a pseudogap appears in photoemission.
We critically analyze the x-ray data, and conclude that a parity-breaking
signal of the kind suggested is unlikely based on the crystal structures
reported in the literature. Possible other origins of the observed dichroism
signal are discussed. We propose x-ray scattering experiments that can be done
in order to determine whether such alternative interpretations are valid or
not.Comment: final version to be published in Phys Rev B: some calculational
details added, clarification of XNLD contamination and biaxiality, more
discussion on possible space groups and previous optics result
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