4,736 research outputs found
About Gravitomagnetism
The gravitomagnetic field is the force exerted by a moving body on the basis
of the intriguing interplay between geometry and dynamics which is the analog
to the magnetic field of a moving charged body in electromagnetism. The
existence of such a field has been demonstrated based on special relativity
approach and also by special relativity plus the gravitational time dilation
for two different cases, a moving infinite line and a uniformly moving point
mass, respectively. We treat these two approaches when the applied cases are
switched while appropriate key points are employed. Thus, we demonstrate that
the strength of the resulted gravitomagnetic field in the latter approach is
twice the former. Then, we also discuss the full linearized general relativity
and show that it should give the same strength for gravitomagnetic field as the
latter approach. Hence, through an exact analogy with the electrodynamic
equations, we present an argument in order to indicate the best definition
amongst those considered in this issue in the literature. Finally, we
investigate the gravitomagnetic effects and consequences of different
definitions on the geodesic equation including the second order approximation
terms.Comment: 16 pages, a few amendments have been performed and a new section has
been adde
Global well-posedness for a slightly supercritical surface quasi-geostrophic equation
We use a nonlocal maximum principle to prove the global existence of smooth
solutions for a slightly supercritical surface quasi-geostrophic equation. By
this we mean that the velocity field is obtained from the active scalar
by a Fourier multiplier with symbol , where
is a smooth increasing function that grows slower than as
.Comment: 11 pages, second version with slightly stronger resul
Heat Conduction Process on Community Networks as a Recommendation Model
Using heat conduction mechanism on a social network we develop a systematic
method to predict missing values as recommendations. This method can treat very
large matrices that are typical of internet communities. In particular, with an
innovative, exact formulation that accommodates arbitrary boundary condition,
our method is easy to use in real applications. The performance is assessed by
comparing with traditional recommendation methods using real data.Comment: 4 pages, 2 figure
Bayesian Networks for Max-linear Models
We study Bayesian networks based on max-linear structural equations as
introduced in Gissibl and Kl\"uppelberg [16] and provide a summary of their
independence properties. In particular we emphasize that distributions for such
networks are generally not faithful to the independence model determined by
their associated directed acyclic graph. In addition, we consider some of the
basic issues of estimation and discuss generalized maximum likelihood
estimation of the coefficients, using the concept of a generalized likelihood
ratio for non-dominated families as introduced by Kiefer and Wolfowitz [21].
Finally we argue that the structure of a minimal network asymptotically can be
identified completely from observational data.Comment: 18 page
Incompressible flow in porous media with fractional diffusion
In this paper we study the heat transfer with a general fractional diffusion
term of an incompressible fluid in a porous medium governed by Darcy's law. We
show formation of singularities with infinite energy and for finite energy we
obtain existence and uniqueness results of strong solutions for the
sub-critical and critical cases. We prove global existence of weak solutions
for different cases. Moreover, we obtain the decay of the solution in ,
for any , and the asymptotic behavior is shown. Finally, we prove the
existence of an attractor in a weak sense and, for the sub-critical dissipative
case with , we obtain the existence of the global attractor
for the solutions in the space for any
Intermediate Tail Dependence: A Review and Some New Results
The concept of intermediate tail dependence is useful if one wants to
quantify the degree of positive dependence in the tails when there is no strong
evidence of presence of the usual tail dependence. We first review existing
studies on intermediate tail dependence, and then we report new results to
supplement the review. Intermediate tail dependence for elliptical, extreme
value and Archimedean copulas are reviewed and further studied, respectively.
For Archimedean copulas, we not only consider the frailty model but also the
recently studied scale mixture model; for the latter, conditions leading to
upper intermediate tail dependence are presented, and it provides a useful way
to simulate copulas with desirable intermediate tail dependence structures.Comment: 25 pages, 1 figur
Teacher Training for Children with Autism Spectrum Disorders in Finland
This chapter first provides a short description of the historical background and development of special education teacher training in Finland. The relationship between special education and teaching pupils with autism spectrum disorder (ASD) is covered by chronologically presenting the main events, turning points, publications, and people that have had a significant effect on the education of pupils with ASD in Finland. This is followed by a description of the organization of teacher training, in general, and the particular characteristics of teaching pupils with ASD. In the context of ASD, it is essential to examine questions concerning the link between learning as social practice and the challenges of interaction manifested in learning difficulties. The chapter ends with a description of the continuing teacher education for special education teachers in Finland.Peer reviewe
Universality classes in Burgers turbulence
We establish necessary and sufficient conditions for the shock statistics to
approach self-similar form in Burgers turbulence with L\'{e}vy process initial
data. The proof relies upon an elegant closure theorem of Bertoin and Carraro
and Duchon that reduces the study of shock statistics to Smoluchowski's
coagulation equation with additive kernel, and upon our previous
characterization of the domains of attraction of self-similar solutions for
this equation
- …