5,629 research outputs found
Traveling Wave in a Ratio-dependent Holling-Tanner System with Nonlocal Diffusion and Strong Allee Effect
In this paper, a ratio-dependent Holling-Tanner system with nonlocal
diffusion is taken into account, where the prey is subject to a strong Allee
effect. To be special, by applying Schauder's fixed point theorem and iterative
technique, we provide a general theory on the existence of traveling waves for
such system. Then appropriate upper and lower solutions and a novel sequence,
similar to squeeze method, are constructed to demonstrate the existence of
traveling waves for c>c*. Moreover, the existence of traveling wave for c=c* is
also established by spreading speed theory and comparison principle. Finally,
the nonexistence of traveling waves for c<c* is investigated, and the minimal
wave speed then is determined
Spectroastrometric Reverberation Mapping of Broad-line Regions
Spectroastrometry measures source astrometry as a function of
wavelength/velocity. Reverberations of spectroastrometric signals naturally
arise in broad-line regions (BLRs) of active galactic nuclei as a result of the
continuum variations that drive responses of the broad emission lines with time
delays. Such signals provide a new diagnostic for mapping BLR kinematics and
geometry, complementary to the traditional intensity reverberation mapping (RM)
technique. We present the generic mathematical formulism for spectroastrometric
RM and show that under realistic parameters of a phenomenological BLR model,
the spectroastrometric reverberation signals vary on a level of several to tens
of microarcseconds, depending on the BLR size, continuum variability, and
angular-size distance. We also derive the analytical expressions of
spectroastrometric RM for an inclined ring-like BLR. We develop a Bayesian
framework with a sophisticated Monte-Carlo sampling technique to analyze
spectroastrometic data and infer the BLR properties, including the central
black hole mass and angular-size distance. We demonstrate the potential of
spectroastrometric RM in spatially resolving BLR kinematics and geometry
through a suite of simulation tests. An application to realistic observation
data of 3C~273 obtains tentative, but enlightening results, reinforcing the
practical feasibility of conducting spectroastrometric RM experiments on bright
AGNs with the operating Very Large Telescope Interferometer as well as possibly
with the planned next-generation 30m-class telescopes.Comment: 22 pages, 17 figures, 2 tables; ApJ in press; The code BRAINS
available at https://github.com/LiyrAstroph/BRAIN
Traveling Waves of Modified Leslie-Gower Predator-prey Systems
The spreading phenomena in modified Leslie-Gower reaction-diffusion
predator-prey systems are the topic of this paper. We mainly study the
existence of two different types of traveling waves. Be specific, with the aid
of the upper and lower solutions method, we establish the existence of
traveling wave connecting the prey-present state and the coexistence state or
the prey-present state and the prey-free state by constructing different and
appropriate Lyapunov functions. Moreover, for traveling wave connecting the
prey-present state and the prey-free state, we gain more monotonicity
information on wave profile based on the asymptotic behavior at negative
infinite. Finally, our results are applied to modified Leslie-Gower system with
Holling II type or Lotka-Volterra type, and then a novel Lyapunov function is
constructed for the latter, which further enhances our results. Meanwhile, some
numerical simulations are carried to support our results
A sufficient condition on successful invasion by the predator
In this paper, we provide a sufficient condition on successful invasion by
the predator. Specially, we obtain the persistence of traveling wave solutions
of predator-prey system, in which the predator can survive without the
predation of the prey. This proof heavily depends on comparison principle of
scalar monostable equation, the rescaling method and phase-plane analysis
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