12,267 research outputs found
Local Markov Property for Models Satisfying Composition Axiom
The local Markov condition for a DAG to be an independence map of a
probability distribution is well known. For DAGs with latent variables,
represented as bi-directed edges in the graph, the local Markov property may
invoke exponential number of conditional independencies. This paper shows that
the number of conditional independence relations required may be reduced if the
probability distributions satisfy the composition axiom. In certain types of
graphs, only linear number of conditional independencies are required. The
result has applications in testing linear structural equation models with
correlated errors.Comment: Appears in Proceedings of the Twenty-First Conference on Uncertainty
in Artificial Intelligence (UAI2005
Polynomial Constraints in Causal Bayesian Networks
We use the implicitization procedure to generate polynomial equality
constraints on the set of distributions induced by local interventions on
variables governed by a causal Bayesian network with hidden variables. We show
how we may reduce the complexity of the implicitization problem and make the
problem tractable in certain causal Bayesian networks. We also show some
preliminary results on the algebraic structure of polynomial constraints. The
results have applications in distinguishing between causal models and in
testing causal models with combined observational and experimental data.Comment: Appears in Proceedings of the Twenty-Third Conference on Uncertainty
in Artificial Intelligence (UAI2007
Riemann-Hilbert approach and N-soliton formula for the N-component Fokas-Lenells equations
In this work, the generalized -component Fokas-Lenells(FL) equations,
which have been studied by Guo and Ling (2012 J. Math. Phys. 53 (7) 073506) for
, are first investigated via Riemann-Hilbert(RH) approach. The main
purpose of this is to study the soliton solutions of the coupled
Fokas-Lenells(FL) equations for any positive integer , which have more
complex linear relationship than the analogues reported before. We first
analyze the spectral analysis of the Lax pair associated with a matrix spectral problem for the -component FL equations. Then, a kind
of RH problem is successfully formulated. By introducing the special conditions
of irregularity and reflectionless case, the -soliton solution formula of
the equations are derived through solving the corresponding RH problem.
Furthermore, take and for examples, the localized structures and
dynamic propagation behavior of their soliton solutions and their interactions
are discussed by some graphical analysis.Comment: 29 pages, 10 figure
The normalized Laplacian spectra of the double corona based on -graph
For simple graphs , and , we denote their double corona based
on -graph by . This paper determines the
normalized Laplacian spectrum of in terms of
these of , and whenever , and are regular. The
obtained result reduces to the normalized Laplacian spectra of the -vertex
corona and -edge corona by
choosing or as a null-graph, respectively. Finally, applying the
results of the paper, we construct infinitely many pairs of normalized
Laplacian cospectral graphs.Comment: 9 pages, 19 conferenc
Inverse scattering transform for the integrable nonlocal Lakshmanan-Porsezian-Daniel equation
In this work, a generalized nonlocal Lakshmanan-Porsezian-Daniel (LPD)
equation is introduced, and its integrability as an infinite dimensional
Hamilton dynamic system is established. Motivated by the ideas of Ablowitz and
Musslimani (2016 Nonlinearity 29 915), we successfully derive the inverse
scattering transform (IST) of the nonlocal LPD equation. The direct scattering
problem of the equation is first constructed, and some important symmetries of
the eigenfunctions and the scattering data are discussed. By using a novel
Left-Right Riemann-Hilbert (RH) problem, the inverse scattering problem is
analyzed, and the potential function is recovered. By introducing the special
conditions of reflectionless case, the time-periodic soliton solutions formula
of the equation is derived successfully. Take and
for example, we obtain some interesting phenomenon such as breather-type
solitons, arc solitons, three soliton and four soliton. Furthermore, the
influence of parameter on these solutions is further considered via
the graphical analysis. Finally, the eigenvalues and conserved quantities are
investigated under a few special initial conditions.Comment: 33 pages, 8 figure
78 Pairs of Possible PSR-SNR Associations
We discuss the criteria to associate PSRs with SNRs, and summary 78 pairs of
possible PSR-SNR associations which is the most complete sample so far. We
refine them into three categories according to degree of reliability. Statistic
study on PSR-SNR associations helps us understand massive star evolution and
constrain pulsar's theory models.Comment: Accepted for publication in NARIT Conference Series (NCS), 2 pages, 1
tabl
Deformation of a soft boundary induced and enhanced by enclosed active particles
We simulate a two dimensional model of self-propelled particles confined by a
deformable boundary. The particles tend to accumulate near the boundary and the
shape of the boundary deforms upon the collisions. We find that there are two
typical stages in the variation of the morphology with the increase of active
force. One is at small force characterized by radially inhomogeneous
redistribution of particles and suppression of local fluctuations of the
boundary. The other is at large force featured by angularly redistribution of
particles and global shape deformation of the boundary. The last two processes
are strongly cooperative. We also find different mechanisms in the particle
redistribution and opposite force-dependences of the rate of the shape
variation at low and high particle concentrations.Comment: 11 pages, 6 figure
Itinerant metamagnetism in manganites caused by the field-induced electronic nematic order
Itinerant metamagnetism transition is observed and studied in perovskite
La1-xCaxMn0.90Cu0.10O3 system for x = 0.30. At a constant low temperature, 10 K
< T < 150 K, there is a continuous second-order metamagnetism jump from a low
magnetic state to a high one with the magnetic field H increasing. However, at
an exceeding low temperature, T = 2.5 K, the metamagnetism jump at H = 3.5 T
becomes to be a robust first-order transition, and another metamagnetism
transition occurs at a higher field H = 7.0 T. Since there is no charge
ordering sign in the present system, it can not be understood by using the
phase separation model or the prior martensite/austenitic phase transition
scenario. A theoretical electronic nematic order phase formation is evidenced
to answer for the two consecutive metamagnetic transitions, which separate the
nematic phase from the low-field (H 7.0 T)
isotropic phases.Comment: 10 pages, 5 figure
Inequality Constraints in Causal Models with Hidden Variables
We present a class of inequality constraints on the set of distributions
induced by local interventions on variables governed by a causal Bayesian
network, in which some of the variables remain unmeasured. We derive bounds on
causal effects that are not directly measured in randomized experiments. We
derive instrumental inequality type of constraints on nonexperimental
distributions. The results have applications in testing causal models with
observational or experimental data.Comment: Appears in Proceedings of the Twenty-Second Conference on Uncertainty
in Artificial Intelligence (UAI2006
Spontaneous symmetry breaking induced unidirectional rotation of chain-grafted colloid in the active bath
Exploiting the energy of randomly moving active agents such as bacteria is a
fascinating way to power a microdevice. Here we show, by simulations, that a
chain-grafted disk-like colloid can rotate unidirectionally when immersed in a
thin film of active particle suspension. The spontaneous symmetry breaking of
chain configurations is the origin of the unidirectional rotation. Long
persistence time, large propelling force and/or small rotating friction are
keys to keeping the broken symmetry and realizing the rotation. In the rotating
state, we find very simple linear relations, e.g. between mean angular speed
and propelling force. The time-evolving asymmetry of chain configurations
reveals that there are two types of non-rotating state. Our findings provide
new insights into the phenomena of spontaneous symmetry breaking in active
systems with flexible objects and also open the way to conceive new
soft/deformable microdevices.Comment: 14 pages (single column, double spaced), 5 figure
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