14,190 research outputs found
Investigation of a universal behavior between N\'eel temperature and staggered magnetization density for a three-dimensional quantum antiferromagnet
We simulate the three-dimensional quantum Heisenberg model with a spatially
anisotropic ladder pattern using the first principles Monte Carlo method. Our
motivation is to investigate quantitatively the newly established universal
relation near the quantum critical
point (QCP) associated with dimerization. Here , , and are
the N\'eel temperature, the spinwave velocity, and the staggered magnetization
density, respectively. For all the physical quantities considered here, such as
and , our Monte Carlo results agree nicely with the
corresponding results determined by the series expansion method. In addition,
we find it is likely that the effect of a logarithmic correction, which should
be present in (3+1)-dimensions, to the relation
near the investigated QCP only sets in significantly in the region
with strong spatial anisotropy.Comment: 5 pages, 7 figures, 2 table
A Panchromatic View of Brown Dwarf Aurorae
Stellar coronal activity has been shown to persist into the low-mass star
regime, down to late M-dwarf spectral types. However, there is now an
accumulation of evidence suggesting that at the end of the main sequence there
is a transition in the nature of the magnetic activity from chromospheric and
coronal to planet-like and auroral, from local impulsive heating via flares and
MHD wave dissipation to energy dissipation from strong large-scale
magnetospheric current systems. We examine this transition and the prevalence
of auroral activity in brown dwarfs through a compilation of multi-wavelength
surveys of magnetic activity, including radio, X-ray, and optical. We compile
the results of those surveys and place their conclusions in the context of
auroral emission as the consequence of large-scale magnetospheric current
systems that accelerate energetic electron beams and drive the particles to
impact the cool atmospheric gas. We explore the different manifestation of
auroral phenomena in brown dwarf atmospheres, like H, and define their
distinguishing characteristics. We conclude that large amplitude photometric
variability in the near infrared is most likely a consequence of clouds in
brown dwarf atmospheres, but that auroral activity may be responsible for
long-lived stable surface features. We report a connection between auroral
H emission and quiescent radio emission in ECMI pulsing brown dwarfs,
suggesting a potential underlying physical connection between the quiescent and
auroral emissions. We also discuss the electrodynamic engines powering brown
dwarf aurorae and the possible role of satellites around these systems to both
power the aurorae and seed the magnetosphere with plasma.Comment: 26 pages, 17 figures, and 2 tables; accepted to Ap
An optimum settling problem for time lag systems
Lagrange multiplier in Banach space for settling optimal control in time lag syste
Schwinger model on a half-line
We study the Schwinger model on a half-line in this paper. In particular, we
investigate the behavior of the chiral condensate near the edge of the line.
The effect of the chosen boundary condition is emphasized. The extension to the
finite temperature case is straightforward in our approach.Comment: 4 pages, no figure. Final version to be published on Phys. Rev.
Parallel Exhaustive Search without Coordination
We analyze parallel algorithms in the context of exhaustive search over
totally ordered sets. Imagine an infinite list of "boxes", with a "treasure"
hidden in one of them, where the boxes' order reflects the importance of
finding the treasure in a given box. At each time step, a search protocol
executed by a searcher has the ability to peek into one box, and see whether
the treasure is present or not. By equally dividing the workload between them,
searchers can find the treasure times faster than one searcher.
However, this straightforward strategy is very sensitive to failures (e.g.,
crashes of processors), and overcoming this issue seems to require a large
amount of communication. We therefore address the question of designing
parallel search algorithms maximizing their speed-up and maintaining high
levels of robustness, while minimizing the amount of resources for
coordination. Based on the observation that algorithms that avoid communication
are inherently robust, we analyze the best running time performance of
non-coordinating algorithms. Specifically, we devise non-coordinating
algorithms that achieve a speed-up of for two searchers, a speed-up of
for three searchers, and in general, a speed-up of
for any searchers. Thus, asymptotically, the speed-up is only four
times worse compared to the case of full-coordination, and our algorithms are
surprisingly simple and hence applicable. Moreover, these bounds are tight in a
strong sense as no non-coordinating search algorithm can achieve better
speed-ups. Overall, we highlight that, in faulty contexts in which coordination
between the searchers is technically difficult to implement, intrusive with
respect to privacy, and/or costly in term of resources, it might well be worth
giving up on coordination, and simply run our non-coordinating exhaustive
search algorithms
Vibration of a circular cylindrical elastic tank, partially filled with an incompressible fluid, undergoing an axial acceleration composed of a uniform and a periodic component technical memorandum no. 102
Forced vibration of circular cylindrical elastic shell partially filled with incompressible liquid and initially at rest in uniform gravitational fiel
Dynamic stability of a flexible booster subjected to a gimbled, periodically-varying end thrust Technical memorandum no. 104
Dynamic structural behavior of large rocket booster synthesized by two thin-walled cylinders and subjected to periodically varying end thrus
SUSY QCD Corrections to Higgs Pair Production from Bottom Quark Fusion
We present a complete next-to-leading order (NLO) calculation for the total
cross section for inclusive Higgs pair production via bottom-quark fusion at
the CERN Large Hadron Collider (LHC) in the minimal supersymmetric standard
model (MSSM) and the minimal supergravity model (mSUGRA). We emphasize the
contributions of squark and gluino loops (SQCD) and the decoupling properties
of our results for heavy squark and gluino masses. The enhanced couplings of
the b quark to the Higgs bosons in supersymmetric models with large tanb yield
large NLO SQCD corrections in some regions of parameter space.Comment: 24 pages, 10 figure
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