共查询到20条相似文献,搜索用时 15 毫秒
1.
Kei-Ichi UedaYasumasa Nishiura 《Physica D: Nonlinear Phenomena》2012,241(1):37-59
A cascade process involving stripe splitting in reaction-diffusion systems with isotropically growing one-dimensional domains is studied. Such cascades, propagating from a smaller domain to a larger domain, have been proposed as an answer to the criticism that the Turing mechanism lacks robustness because many stable patterns can coexist on a large domain and, therefore, the final state is very sensitive to the initial conditions. In contrast, if the system starts with a small domain, very few stable patterns are possible, which limits the sensitivity to the initial conditions. In order to show the validity and limitations of this scenario, we clarify the underlying mathematical mechanism that drives various types of stripe-splitting via a reduction from partial differential equations to ordinary differential equations, as well as investigating global arrangements of the set of n-mode stripe branches with Dn-symmetry of the stripe locations. The mathematical simplification above allows us to reveal how each n-mode stripe branch is destabilized as the domain grows and to characterize the associated eigenprofiles that actually determine the manner of splitting at the infinitesimal level. We find that all the Dn-symmetry-breaking instabilities typically occur simultaneously up to leading order before the saddle-node point of the n-mode stripe branch is reached. The instability with the largest real part is of the alternate type: every other peak splits at the infinitesimal level. A symmetry-preserving instability appears at the saddle-node point, which drives the simultaneous type of splitting, i.e., mode-doubling. Due to competition between these two types of instabilities, the problem depends subtly on the growth speed. Alternate splitting typically arises for slow growth and simultaneous splitting for fast growth. For intermediate growth rates, the manner of splitting becomes mixed and sensitive to fluctuations. 相似文献
2.
Chemically induced dynamic electron polarization (CIDEP) of galvinoxyl was measured in various excited molecule-galvinoxyl
systems prepared by laser photolysis. Most of the systems examined showed net emission CIDEP, which is well explained by the
quartet precursor radical-triplet pair mechanism with exchange interaction,J, of negative sign (quartet is higher than doublet). Several systems with molecules such as naphthalene, quinoxaline, biphenyl
and triphenylene, however, showed net absorption CIDEP. Time profiles of CIDEP and kinetic analysis of quenching suggest that
net absorption CIDEP is generated during the triplet quenching process by the galvinoxyl radical. We conclude that the net
absorption CIDEP is produced during the triplet quenching if theJ value of radical-triplet encounter pair is positive. This is the first report of the radical-triplet encounter pairs with
positiveJ value. The mechanism for this unusual positive sign ofJ value is discussed on the basis of the spin-selective configuration interaction between the doublet spin correlated states
of radical-triplet and charge transfer encounter pairs. 相似文献
3.
The charge structure and interaction mechanism on In-doped sulphur spinel FeInxCr2−xS4 are studied. The temperature dependence of magnetization μB, measured from 60 K to room temperature, suggests that FeInxCr2−xS4 (x=0.1, 0.3) are ferrimagnetic. The Néel temperature is decreased with increasing non-magnetic In substitution as consequence of reduction of superexchange interaction for increased lattice parameter. FeInxCr2−xS4 is investigated by Mössbauer spectra from 4.2 K to room temperature. The asymmetric line broadening is observed for the sample FeInxCr2−xS4 and considered to be dynamic Jahn–Teller relaxation. The charge state of Fe ions is ferrous in character. 相似文献
4.
5.
The close coupled equations provide low-energy cross sections which are in good agreement with the experimental values. 相似文献
6.
J. Haidenbauer 《The European Physical Journal A - Hadrons and Nuclei》2007,33(3):287-290
We present a new model for the hyperon-nucleon (ΛN , ΣN interaction, derived within the meson exchange framework. The model incorporates the standard one-boson exchanges of the
lowest pseudoscalar and vector meson multiplets with coupling constants fixed by SU(6) flavor symmetry relations. As a new feature, the contribution in the scalar-isoscalar (σ sector is derived from a microscopic
model of correlated ππ and Kˉ exchange. The same model is also used to constrain the interaction resulting from the vector-isovector (ρ exchange channel.
Additional short-ranged ingredients of the model in the scalar-isovector (a0) and scalar-isospin-1/2 (κ channels are likewise viewed as arising from meson-meson correlations but are treated phenomenologically.
With this model a satisfactory reproduction of the available hyperon-nucleon data is achieved. 相似文献
7.
Using a combination of linear response theory and constrained orbital hybridization approach, we study the mechanism of magnetic exchange interaction of iron-based superconductor. We reproduce the observed highly anisotropic exchange interaction, and our constrained orbital calculation unambiguously identifies that the anisotropic feature of exchange interaction is not sensitive to the unequal dxz/dyz orbital population. 相似文献
8.
Mohapatra RN 《Physical review letters》1987,59(14):1510-1512
9.
A microscopic theory of π-meson double charge exchange (DCE) on light nuclei has been suggested and developed on the supposition that the corresponding elementary process proceeds by quasi-α-particle formation within the nucleus. Light nuclei consisting of both α-particles and α-particles and clusters of other kinds are considered. To describe the bound state of the quasi-α- particle and the continuum spectrum state of four identical nucleons, the four-body hyperspherical basis has been applied, while to obtain the wave functions of the centers of mass of the cluster relative motion we solve either the three-body Schrödinger equation (in the case of a three-body cluster configuration) or the two-body Schrödinger equation (in the case of a two-body cluster configuration). The reactions π± + 12C → π + 4p(4n) + 2α, π− + 7Li → π+ + 4n + 3H, π± + 6Li → π + 4p(4n) + n + p, π± + 6Li → π + 4p(4n) + d are investigated. It is shown that the effect of the final-state interaction between the four nucleons emitted by the nucleus in the process of π-meson DCE is rather important. The available experimental data on the 7Li nucleus can be explained quite satisfactorily on the supposition that this nucleus has a two-body cluster structure, and, hence, the π-meson DCE process occurs only on the α-particle.The differential and total cross sections of the reactions under investigation calculated as functions of the incident pion energy are essentially different for different nucleon-nucleon potentials. Experimental study of DCE on α-particle nuclei is shown to be a timely problem. 相似文献
10.
11.
在高导流系数的宽带速调管中,电子束径向及横向速度都会发生显著变化,运动电子与间隙电场之间的能量交换是非线性的互作用过程。为了能全面描述这些现象,基于圆环模型导出了相应的理论公式,并据此编写了用于速调管注波互作用分析的2.5维程序LSP。随后使用该程序针对一个实际的S波段宽带速调管做了详细计算,与1维程序相比,LSP的计算结果与实测值具有更好的一致性。 相似文献
12.
We study the interplay of topological excitations in stripe phases: charge dislocations, charge loops, and spin vortices. In two dimensions these defects interact logarithmically on large distances. Using a renormalization-group analysis in the Coulomb-gas representation of these defects, we calculate the phase diagram and the critical properties of the transitions. Depending on the interaction parameters, spin and charge order can disappear at a single transition or in a sequence of two transitions (spin-charge separation). These transitions are nonuniversal with continuously varying critical exponents. We also determine the nature of the points where three phases coexist. 相似文献
13.
We present a combined experimental and theoretical study of cold reactive collisions between laser-cooled Ca+ ions and Rb atoms in an ion-atom hybrid trap. We observe rich chemical dynamics which are interpreted in terms of nonadiabatic and radiative charge exchange as well as radiative molecule formation using high-level electronic structure calculations. We study the role of light-assisted processes and show that the efficiency of the dominant chemical pathways is considerably enhanced in excited reaction channels. Our results illustrate the importance of radiative and nonradiative processes for the cold chemistry occurring in ion-atom hybrid traps. 相似文献
14.
Boothroyd AT Freeman PG Prabhakaran D Hiess A Enderle M Kulda J Altorfer F 《Physical review letters》2003,91(25):257201
We have observed a diffuse component to the low-energy magnetic excitation spectrum of stripe-ordered La(5/3)Sr(1/3)NiO4 probed by neutron inelastic scattering. The diffuse scattering forms a square pattern with sides parallel and perpendicular to the stripe directions. The signal is dispersive, with a maximum energy of approximately 10 meV. Probed at 2 meV, the scattering decreases in strength with increasing temperature, and is barely visible at 100 K. We argue that the signal originates from dynamic, quasi-one-dimensional, antiferromagnetic correlations among the stripe electrons. 相似文献
15.
B. M. Smirnov 《Journal of Experimental and Theoretical Physics》2001,92(6):951-959
The asymptotic resonant charge exchange theory is developed for slow collisions of atoms and ions with valent p-electrons. Because of a small rotation angle of the molecular axis in the course of the p-electron transition, the resonant charge exchange cross section is not sensitive to the rotational energy of colliding particles, and the cross sections are nearly equal for cases “a”, “b”, and “d” of the Hund coupling, and also for cases “c” and “e” of the Hund coupling. The cross sections of the resonant charge exchange process are evaluated under various conditions and for various elements of the periodical table with p-electron shells of atoms and ions. 相似文献
16.
Xiao-fu Lü B.S. Zou Hui-ming Ding Yu-xin Liu En-guang Zhao 《The European Physical Journal A - Hadrons and Nuclei》1998,3(4):377-380
The contribution of the σ meson exchange to the pionic double charge exchange (DCX) reaction is investigated. A concrete
calculation on the forward excitation function of the low energy DCX reaction 14C(π+, π−)14O has been performed. It shows that the contribution of the σ meson exchange can reproduce well the resonance like excitation
function of low energy DCX reaction.
Received: 5 August 1998 相似文献
17.
《Solid State Communications》1987,61(11):713-715
The electron correlation effect on the charge exchange problem in the time-dependent Newns-Anderson model with U→∞ is discussed in the approach of the expanded wavefunction in terms of electron-hole pair excitation. Only a limited case is analyzed rigorously on the expansion terms up to the eighth order of the admixture coupling constant to conclude that the same expression holds for the non-adiabatic exchange of the total charge as in the non-interacting case. This conclusion is conjectured to hold somewhat generally. 相似文献
18.
The existing experimental data on the d(n, p)nn and d(p, n)pp cross-sections in the forward direction are reviewed in terms of the Dean sum rule. It is shown that the measurement of the
ratio of the charge exchange on the deuteron to that on the proton might, if taken together with other experimental data,
allow a direct construction of the np → np scattering amplitude in the backward direction with few ambiguities.
Communicated by T. Hennino 相似文献
19.