The one-dimensional basic contact process is a Markov process for which particles give birth on vacant nearest neighbor sites at rate >0 and particles die at rate one. We introduce a one-dimensional contact process with a single inhomogeneous site: the evolution is as above except that a particle located at the origin does not die. Let c be the critical value of the basic contact process. We show that for c the upper invariant measures of the inhomogeneous contact process and the basic contact process coincide except at a finite number of sites. The behavior at =c is much more intersting: the upper invariant measure of the inhomogeneous contact process concentrates on configurations with infinitely many particles, while it is known that the critical basic contact process dies out. So a single inhomogeneity may provoke a perturbation unbounded in space. As a byproduct of our analysis we prove that the connectivity probabilities of the critical basic contact process are not summable. We also give a biological interpretation of this model. 相似文献
Thed-dimensional random Cantor set is a generalization of the classical middle-thirds Cantor set. Starting with the unit cube [0, 1]d, at every stage of the construction we divide each cube remaining intoMd equal subcubes, and select each of these at random with probabilityp. The resulting limit set is a random fractal, which may be crossed by paths or (d–1)-dimensional sheets. We examine the critical probabilityps(M, d) marking the existence of these sheet crossings, and show that ps(M,d)1–pc(Md) asM, where pc(Md) is the critical probability of site percolation on the lattice (Md) obtained by adding the diagonal edges to the hypercubic lattice d. This result is then used to show that, at least for sufficiently large values ofM, the phases corresponding to the existence of path and sheet crossings are distinct. 相似文献
Let be a nonconstant real entire function of genus and assume that all the zeros of are distributed in some infinite strip , . It is shown that (1) if has nonreal zeros in the region , and has nonreal zeros in the same region, and if the points and are located outside the Jensen disks of , then has exactly critical zeros in the closed interval , (2) if is at most of order , , and minimal type, then for each positive constant there is a positive integer such that for all has only real zeros in the region , and (3) if is of order less than , then has just as many critical points as couples of nonreal zeros.
Densities, heat capacities and conductivities of water-surfactant--cyclodextrin (-CD) ternary systems were determined at 25°C. The surfactants studied were sodium dodecylsulfate (NaDS) and dodecyltrimethylammonium bromide (DTAB). From conductivity data, apparent critical micelle concentrations (cmc*) and degree of ionization of micelles were obtained at a fixed -CD concentration (mCD). From the cmc* value and that in water (cmc) the stoichiometry of the surfactant--CD complex was calculated. At a given mCD, the apparent molar volume V,CD and heat capacity C,CD of -CD in the two surfactants were calculated as functions of surfactant concentration mS. For both NaDS and DTAB, V,CD increases with mS up to about the cmc beyond which it decreases to a constant value at high mS, the opposite is observed for C,CD. With NaDS, a jump in the C,CD vs, mS trend was detected and ascribed to a structural NaDS micellar transition. The apparent molar volume VS and heat capacity CS of NaDS and DTAB in the water--CD mixture 0.017 m were also obtained. From these properties and those in pure water, the volume VS and heat capacity CS of transfer of the surfactant from water to water+-CD mixture as functions of mS were calculated. For both surfactants, the VS vs. mS trends increase to the cmc and then decrease in a monotonic manner, whereas CS increases regularly with mS in the pre-micellar region and is essentially constant in the post-micellar region. The VS vs. mS trends were qualitatively explained in terms of dispersed, complexed and micellized surfactant contributions. 相似文献
Let Ω be a bounded smooth domain inR2. Letf:R→R be a smooth non-linearity behaving like exp{s2} ass→∞. LetF denote the primitive off. Consider the functionalJ:H01
(Ω)→R given by
It can be shown thatJ is the energy functional associated to the following nonlinear problem: −Δu=f(u) in Ω,u=0 on ρΩ. In this paper we consider the global compactness properties ofJ. We prove thatJ fails to satisfy the Palais-Smale condition at the energy levels {k/2},k any positive integer. More interestingly, we show thatJ fails to satisfy the Palais-Smale condition at these energy levels along two Palais-Smale sequences. These two sequences
exhibit different blow-up behaviours. This is in sharp contrast to the situation in higher dimensions where there is essentially
one Palais-Smale sequence for the corresponding energy functional. 相似文献
Spherical harmonics have been important tools for solving geophysical and astrophysical problems. Methods have been developed to effectively implement spherical harmonic expansion approximations. However, the Gibbs phenomenon was already observed by Weyl for spherical harmonic expansion approximations to functions with discontinuities, causing undesirable oscillations over the entire sphere.
Recently, methods for removing the Gibbs phenomenon for one-dimensional discontinuous functions have been successfully developed by Gottlieb and Shu. They proved that the knowledge of the first expansion coefficients (either Fourier or Gegenbauer) of a piecewise analytic function is enough to recover an exponentially convergent approximation to the point values of in any subinterval in which the function is analytic.
Here we take a similar approach, proving that knowledge of the first spherical harmonic coefficients yield an exponentially convergent approximation to a spherical piecewise smooth function in any subinterval , where the function is analytic. Thus we entirely overcome the Gibbs phenomenon.
We calculate 800 coefficients of the high-temperature expansion of the magnetic susceptibility of Dyson's hierarchical model with a Landau-Ginzburg measure. Log-periodic corrections to the scaling laws appear as in the case of an Ising measure. The period of oscillation appears to be a universal quantity given in good approximation by the logarithm of the largest eigenvalue of the linearized RG transformation, in agreement with a possibility suggested by Wilson and developed by Niemeijer and van Leeuwen. We estimate to be 1.300 (with a systematic error of the order of 0.002), in good agreement with the results obtained with other methods, such as the -expansion. We briefly discuss the relationship between the oscillations and the zeros of the partition function near the critical point in the complex temperature plane. 相似文献
The surface critical behavior of the two-dimensional Ising model with homogeneous perturbations in the surface interactions is studied on the one-dimensional quantum version. A transfer-matrix method leads to an eigenvalue equation for the excitation energies. The spectrum at the bulk critical point is obtained using anL–1 expansion, whereL is the length of the Ising chain. It exhibits the towerlike structure which is characteristic of conformal models in the case of irrelevant surface perturbations (hs/Js0) as well as for the relevant perturbationhs=0 for which the surface is ordered at the bulk critical point leading to an extraordinary surface transition. The exponents are deduced from the gap amplitudes and confirmed by exact finite-size scaling calculations. Both cases are finally related through a duality transformation. 相似文献
Natural gases containing sour components exhibit different gas compressibility factor(Z) behavior than do sweet gases.Therefore,a new accurate method should be developed to account for these differences.Several methods are available today for calculating the Z-factor from an cquation of state. However,these equations are more complex than the foregoing correlations,involving a large number of parameters,which require more complicated and longer computations.The aim of this study is to develop a simplified calculation method for a rapid estimating Z-factor for sour natural gases containing as much as 90% total acid gas.In this article,two new correlations are first presented for calculating the pseudo- critical pressure and temperature of the gas mixture as a function of the gas specific gravity.Then,a simple correlation on the basis of the standard gas compressibility factor chart is introduced for a quick estimation of sweet gases' compressibility factor as a function of reduced pressure and temperature.Finally,a new corrective term related to the mole fractions of carbon dioxide and hydrogen sulfide is developed. 相似文献
Specific conductivities, densities, heat capacities, and enthalpies of dilution at 25‡C were measured forN,N,N-octylpentyldimethylammonium chloride (OPAC) in water-urea mixtures at various urea concentrations mu as functions of the surfactant concentration ms. From conductivity data, the cmc and the degree of the counterion dissociation Β of the OPAC micelles were calculated. The
cmc increases linearly with increasingmu while Βvs. mu is a smooth concave curve. From the experimental thermodynamic data, the apparentYΦ and partialY2 molar properties (volumes, heat capacities, and relative enthalpies) are derived as functions of mu andms. The effect of urea on the dependences of the different properties on ms are discussed. From data in the premicellar region the standard partial molar volumesV20
and heat capacitiesCp20
were evaluated. It was observed thatV20
increases linearly withmu whileCp20
decreases. The properties of OPAC in the dispersed and micellized forms at the cmc were obtained and, therefore, the thermodynamic
functions of micellization were calculated on the basis of the pseudo-phase transition model. 相似文献