9,438 research outputs found
Formalization of the fundamental group in untyped set theory using auto2
We present a new framework for formalizing mathematics in untyped set theory
using auto2. Using this framework, we formalize in Isabelle/FOL the entire
chain of development from the axioms of set theory to the definition of the
fundamental group for an arbitrary topological space. The auto2 prover is used
as the sole automation tool, and enables succinct proof scripts throughout the
project.Comment: 17 pages, accepted for ITP 201
Many-body dynamics of a Bose system with attractive interactions on a ring
We investigate the many-body dynamics of an effectively attractive
one-dimensional Bose system confined in a toroidal trap. The mean-field theory
predicts that a bright-soliton state will be formed when increasing the
interparticle interaction over a critical point. The study of quantum many-body
dynamics in this paper reveals that there is a modulation instability in a
finite Bose system correspondingly. We show that Shannon entropy becomes
irregular near and above the critical point due to quantum correlations. We
also study the dynamical behavior of the instability by exploring the momentum
distribution and the fringe visibility, which can be verified experimentally by
releasing the trapComment: 6 pages,5 figure
Potential of Geo-neutrino Measurements at JUNO
The flux of geoneutrinos at any point on the Earth is a function of the
abundance and distribution of radioactive elements within our planet. This flux
has been successfully detected by the 1-kt KamLAND and 0.3-kt Borexino
detectors with these measurements being limited by their low statistics. The
planned 20-kt JUNO detector will provide an exciting opportunity to obtain a
high statistics measurement, which will provide data to address several
questions of geological importance. This paper presents the JUNO detector
design concept, the expected geo-neutrino signal and corresponding backgrounds.
The precision level of geo-neutrino measurements at JUNO is obtained with the
standard least-squares method. The potential of the Th/U ratio and mantle
measurements is also discussed.Comment: 8 pages, 6 figures, an additional author added, final version to
appear in Chin. Phys.
On Beltrami Model of de Sitter Spacetime
Based on some important properties of space, we present a Beltrami model
that may shed light on the observable puzzle of space
and the paradox between the special relativity principle and cosmological
principle. In , there are inertial-type coordinates and
inertial-type observers. Thus, the classical observables can be defined for
test particles and light signals. In addition, by choosing the definition of
simultaneity the Beltrami metric is transformed to the Robertson-Walker-like
metric. It is of positive spatial curvature of order . This is more or
less indicated already by the CMB power spectrum from WMAP and should be
further confirmed by its data in large scale.Comment: 4 page
Medium-Term Earthquake Forecast Using Gravity Monitoring Data: Evidence from the Yutian and Wenchuan Earthquakes in China
Gravity changes derived from regional gravity monitoring data in China from 1998 to 2005 exhibited noticeable variations before the occurrence of two large earthquakes in 2008 in China—the 2008 Yutian (Xinjiang) Ms=7.3 earthquake and the 2008 Wenchuan (Sichuan) Ms=8.0 earthquake. Based on these gravity variations, a group of researchers at the Second Crust Monitoring and Application Center of China Earthquake Administration made a suggestion in December of 2006 that the possibility for the Yutian (Xinjiang) and Wenchuan (Sichuan) areas to experience a large earthquake in either 2007 or 2008 was high. We review the gravity monitoring data and methods upon which the researchers reached these medium-term earthquake forecasts. Experience related to the medium-term forecasts of the Yutian and Wenchuan earthquakes suggests that gravity changes derived from regional gravity monitoring data could potentially be a useful medium-term precursor of large earthquakes, but significant additional research is needed to validate and evaluate this hypothesis
Cylindrical vector beams for rapid polarization-dependent measurements in atomic systems
We demonstrate the use of cylindrical vector beams - beams with spatially
varying polarization - for detecting and preparing the spin of a warm rubidium
vapor in a spatially dependent manner. We show that a modified probe vector
beam can serve as an atomic spin analyzer for an optically pumped medium, which
spatially modulates absorption of the beam. We also demonstrate space-variant
atomic spin by optical pumping with the vector beams. The beams are thus
beneficial for making singleshot polarization-dependent measurements, as well
as for providing a means of preparing samples with position-dependent spin.Comment: 8 pages, 5 figures. Accepted in Optics Expres
The Multiphase Intracluster Medium in Galaxy Groups Probed by the Lyman Alpha Forest
The case is made that the intracluster medium (ICM) in spiral-rich galaxy
groups today probably has undergone much slower evolution than that in
elliptical-rich groups and clusters. The environments of proto-clusters and
proto-groups at z > 2 are likely similar to spiral-rich group environments at
lower redshift. Therefore, like the ICM in spiral-rich groups today, the ICM in
proto-groups and proto-clusters at z > 2 is predicted to be significantly
multiphased. The QSO Lyman alpha forest in the vicinity of galaxies is an
effective probe of the ICM at a wide range of redshift. Two recent observations
of Lyman alpha absorption around galaxies by Adelberger et al. and by
Pascarelle et al are reconciled, and it is shown that observations support the
multiphase ICM scenario. Galaxy redshifts must be very accurate for such
studies to succeed. This scenario can also explain the lower metallicity and
lower hot gas fraction in groups.Comment: 4 pages, 1 figure, replaced with the version after proo
Equity Incentives and corporate fraud in China
This is the author accepted manuscript. The final version is available from Springer Verlag via the DOI in this recordThis paper explores how managers’ and supervisors’ equity incentives impact the likelihood of committing corporate fraud in Chinese-listed firms. Previous research has shown that corporate fraud in China is a widespread phenomenon and has severe consequences for affected firms and executives. However, our understanding of the reasons that fraud is committed in a Chinese setting has been very limited thus far. This is an increasingly important topic, because corporate governance is rapidly changing in China, and it is unclear whether adopting the executive compensation practices of the West is appropriate for Chinese firms. We show that managers’ equity incentives increase their propensity to commit corporate fraud. We also find that this effect is more pronounced for state-owned firms. However, we find a negative but not significant relationship between the equity incentives of the supervisory board and the incidence of fraud
Mass Hierarchy Determination Using Neutrinos from Multiple Reactors
We report the results of Monte Carlo simulations of a medium baseline reactor
neutrino experiment. The difference in baselines resulting from the 1 km
separations of Daya Bay and Ling Ao reactors reduces the amplitudes of 1-3
oscillations at low energies, decreasing the sensitivity to the neutrino mass
hierarchy. A perpendicular detector location eliminates this effect. We
simulate experiments under several mountains perpendicular to the Daya Bay/Ling
Ao reactors, considering in particular the background from the TaiShan and
YangJiang reactor complexes. In general the hierarchy can be determined most
reliably underneath the 1000 meter mountain BaiYunZhang, which is 44.5 km from
Daya Bay. If some planned reactors are not built then nearby 700 meter
mountains at 47-51 km baselines gain a small advantage. Neglecting their low
overhead burdens, hills near DongKeng would be the optimal locations. We use a
weighted Fourier transform to avoid a spurious dependence on the high energy
neutrino spectrum and find that a neural network can extract quantities which
determine the hierarchy marginally better than the traditional RL + PV.Comment: 22 pages, added details on the neural network (journal version
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