54,266 research outputs found
On the sine-Gordon--Thirring equivalence in the presence of a boundary
In this paper, the relationship between the sine-Gordon model with an
integrable boundary condition and the Thirring model with boundary is discussed
and the reflection -matrix for the massive Thirring model, which is related
to the physical boundary parameters of the sine-Gordon model, is given. The
relationship between the the boundary parameters and the two formal parameters
appearing in the work of Ghoshal and Zamolodchikov is discussed.Comment: 14 pages, Latex, to be published in Int. J. Mod. Phys. A. Two
references adde
Simple scheme for two-qubit Grover search in cavity QED
Following the proposal by F. Yamaguchi et al.[Phys. Rev. A 66, 010302 (R)
(2002)], we present an alternative way to implement the two-qubit Grover search
algorithm in cavity QED. Compared with F. Yamaguchi et al.'s proposal, with a
strong resonant classical field added, our method is insensitive to both the
cavity decay and thermal field, and doesn't require that the cavity remain in
the vacuum state throughout the procedure. Moreover, the qubit definitions are
the same for both atoms, which makes the experiment easier. The strictly
numerical simulation shows that our proposal is good enough to demonstrate a
two-qubit Grover's search with high fidelity.Comment: manuscript 10 pages, 2 figures, to appear in Phys. Rev.
Combining Models of Approximation with Partial Learning
In Gold's framework of inductive inference, the model of partial learning
requires the learner to output exactly one correct index for the target object
and only the target object infinitely often. Since infinitely many of the
learner's hypotheses may be incorrect, it is not obvious whether a partial
learner can be modifed to "approximate" the target object.
Fulk and Jain (Approximate inference and scientific method. Information and
Computation 114(2):179--191, 1994) introduced a model of approximate learning
of recursive functions. The present work extends their research and solves an
open problem of Fulk and Jain by showing that there is a learner which
approximates and partially identifies every recursive function by outputting a
sequence of hypotheses which, in addition, are also almost all finite variants
of the target function.
The subsequent study is dedicated to the question how these findings
generalise to the learning of r.e. languages from positive data. Here three
variants of approximate learning will be introduced and investigated with
respect to the question whether they can be combined with partial learning.
Following the line of Fulk and Jain's research, further investigations provide
conditions under which partial language learners can eventually output only
finite variants of the target language. The combinabilities of other partial
learning criteria will also be briefly studied.Comment: 28 page
Can the Bump be Observed in the Early Afterglow of GRBS with X-Ray Line Emission Features?
Extremely powerful emission lines are observed in the X-ray afterglow of
several GRBs. The energy contained in the illuminating continuum which is
responsible for the line production exceeds 10 erg, much higher than
that of the collimated GRBs. It constrains the models which explain the
production of X-ray emission lines. In this paper, We argue that this energy
can come from a continuous postburst outflow. Focusing on a central engine of
highly magnetized millisecond pulsar or magnetar we find that afterglow can be
affected by the illuminating continuum, and therefore a distinct achromatic
bump may be observed in the early afterglow lightcurves. With the luminosity of
the continuous outflow which produces the line emission, we define the upper
limit of the time when the bump feature appears. We argue that the reason why
the achromatic bumps have not been detected so far is that the bumps should
appear at the time too early to be observed.Comment: 13 pags, 2 tables, appear in v603 n1 pt1 ApJ March 1, 2004 issu
Human African trypanosomiasis : the current situation in endemic regions and the risks for non-endemic regions from imported cases
Human African trypanosomiasis (HAT) is caused by Trypanosoma brucei
gambiense and T. b. rhodesiense and caused devastating epidemics during the 20th
century. Due to effective control programs implemented in the last two decades, the
number of reported cases has fallen to a historically low level. Although fewer than
977 cases were reported in 2018 in endemic countries, HAT is still a public health
problem in endemic regions until it is completely eliminated. In addition, almost 150
confirmed HAT cases were reported in non-endemic countries in the last three
decades. The majority of non-endemic HAT cases were reported in Europe, United
States and South Africa, due to historical alliances, economic links or geographic
proximity to disease endemic countries. Furthermore, with the implementation of the
âBelt and Roadâ project, sporadic imported HAT cases have been reported in China
as a warning sign of tropical diseases prevention. In this paper, we explore and
interpret the data on HAT incidence and find no positive correlation between the
number of HAT cases from endemic and non-endemic countries.This data will
provide useful information for better understanding the imported cases of HAT
globally in the post-elimination phase
Robust Hâ feedback control for uncertain stochastic delayed genetic regulatory networks with additive and multiplicative noise
The official published version can found at the link below.Noises are ubiquitous in genetic regulatory networks (GRNs). Gene regulation is inherently a stochastic process because of intrinsic and extrinsic noises that cause kinetic parameter variations and basal rate disturbance. Time delays are usually inevitable due to different biochemical reactions in such GRNs. In this paper, a delayed stochastic model with additive and multiplicative noises is utilized to describe stochastic GRNs. A feedback gene controller design scheme is proposed to guarantee that the GRN is mean-square asymptotically stable with noise attenuation, where the structure of the controllers can be specified according to engineering requirements. By applying control theory and mathematical tools, the analytical solution to the control design problem is given, which helps to provide some insight into synthetic biology and systems biology. The control scheme is employed in a three-gene network to illustrate the applicability and usefulness of the design.This work was funded by Royal Society of the U.K.; Foundation for the Author of National Excellent Doctoral Dissertation of China. Grant Number: 2007E4; Heilongjiang Outstanding Youth Science Fund of China. Grant Number: JC200809; Fok Ying Tung Education Foundation. Grant Number: 111064; International Science and Technology Cooperation Project of China. Grant Number: 2009DFA32050; University of Science and Technology of China Graduate Innovative Foundation
Generation of entangled photons by trapped ions in microcavities under a magnetic field gradient
We propose a potential scheme to generate entangled photons by manipulating
trapped ions embedded in two-mode microcavities, respectively, assisted by a
magnetic field gradient. By means of the spin-spin coupling due to the magnetic
field gradient and the Coulomb repulsion between the ions, we show how to
efficiently generate entangled photons by detecting the internal states of the
trapped ions. We emphasize that our scheme is advantageous to create complete
sets of entangled multi-photon states. The requirement and the experimental
feasibility of our proposal are discussed in detail.Comment: 2 Tables, 2 Figures, To appear in Phys. Rev.
Surface phase separation in nanosized charge-ordered manganites
Recent experiments showed that the robust charge-ordering in manganites can
be weakened by reducing the grain size down to nanoscale. Weak ferromagnetism
was evidenced in both nanoparticles and nanowires of charge-ordered manganites.
To explain these observations, a phenomenological model based on surface phase
separation is proposed. The relaxation of superexchange interaction on the
surface layer allows formation of a ferromagnetic shell, whose thickness
increases with decreasing grain size. Possible exchange bias and softening of
the ferromagnetic transition in nanosized charge-ordered manganites are
predicted.Comment: 4 pages, 3 figure
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