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1.
Using renormalization group techniques, we investigate the large distance behavior of a driven, interacting lattice gas in the disordered phase. Unlike the equilibrium Ising model, its behavior, ford>2, is controlled by aline of fixed points, each of which is interpreted as a dynamical system violating the fluctuation-dissipation theorem (FDT). As a consequence, correlation functions at large distances typically decay according to a power law instead of an exponential. Ford2, the renormalization group flows towards an FDT-satisfying fixed point, which corresponds to the high-temperature, strong-drive limit. In the steady state of such a model (a driven, free lattice gas), correlations are known to be exactly zero. Nevertheless, our correlations are still dominated by power laws, since the FDT-breaking operators aredangerously irrelevant (marginal ind=2). Thus, for anyd, the long wavelength properties cannot be obtained by taking either the non-interacting or theT limit, unlike for the equilibrium Ising model.  相似文献   

2.
A geometrical gravitational theory based on the connection ={ } + ln + lng ln is developed. The field equations for the new theory are uniquely determined apart from one unknown dimensionless parameter 2. The geometry on which our theory is based is an extension of the Weyl geometry, and by the extension the gravitational coupling constant and the gravitational mass are made to be dynamical and geometrical. The fundamental geometrical objects in the theory are a metricg and two gauge scalars and. Physically the gravitational potential corresponds tog in the same way as in general relativity, the gravitational coupling constant to –2, and the gravitational mass tou(, ), which is a coscalar of power –1 algebraically made of and. The theory satisfies the weak equivalence principle, but breaks the strong one generally. We shall find outu(, )= on the assumption that the strong one keeps holding good at least for bosons of low spins. Thus we have the simple correspondence between the geometrical objects and the gravitational objects. Since the theory satisfies the weak one, the inertial mass is also dynamical and geometrical in the same way as is the gravitational mass. Moreover, the cosmological term in the theory is a coscalar of power –4 algebraically made of andu(, ), so it is dynamical, too. Finally we give spherically symmetric exact solutions. The permissible range of the unknown parameter 2 is experimentally determined by applying the solutions to the solar system.  相似文献   

3.
We consider a stochastic system of particles in a two dimensional lattice and prove that, under a suitable limit (i.e.N, 0,N2const, whereN is the number of particles and is the mesh of the lattice) the one-particle distribution function converges to a solution of the two-dimensional Broadwell equation for all times for which the solution (of this equation) exists. Propagation of chaos is also proven.Research partially supported by CNR-PS-MMAIT  相似文献   

4.
We extend the bichromatic majority model by including (one-dimensional isotropic) correlations and numerically discuss, through Monte Carlo simulations, the simple, 1/3, and 2/3 majority rules. We calculate, as functions of the concentration and correlation degree, the mean finite cluster size, and the order parameterm as well as their respective critical exponents and. We find1 regardless of the correlation degree or the type of majority. Also, a supplementary divergence of is observed at the>0 borderline.  相似文献   

5.
LetN, be von-Neumann-Algebras on a Hilbert space , a comon cyclic and separarting vector. Assume to be cyclic and separating also forN . Denote byJ , J N the modular conjugations to (, ), and N the associated modular operators. If and these data define in a canonical way a conformal quantum field theory in a cricle. Conversely, the chiral part of a conformal quantum field theory in two dimensions always yields such data in a natural way.Partly supported by the DFG, SFB 288 Differentiageometrie und Quantenphysik  相似文献   

6.
A lattice model is used to study the properties of an infinite self-avoiding linear polymer chain that occupies a fraction, 01, of sites on ad-dimensional hypercubic lattice. The model introduces an (attractive or repulsive) interaction energy between nonbonded monomers that are nearest neighbors on the lattice. The lattice cluster theory enables us to derive a double series expansion in and d–1 for the chain free energy per segment while retaining the full dependence. Thermodynamic quantities, such as the entropy, energy, and mean number of contacts per segment, are evaluated, and their dependences on, , andd are discussed. The results are in good accordance with known limiting cases.  相似文献   

7.
We consider a sequencev of non-stationary solutions of the incompressible 2D-Euler equation, locally bounded inL 2. We prove that if the defect measure is supported in a one-dimensional set (3) of some special type (which we call finite type), the weak limitv ofv is a solution of the Euler equations: our theorem is of the type concentration-cancellation.  相似文献   

8.
Renormalized transport equations for general Fokker-Planck systems are derived and applied to the bistable potential model. The exact equation for the expectation value x t can be evaluated in both domains Dx ± and xD 0 outside and between the potential minima, leading to drastic differences of the dynamics prevailing inD ± andD 0, respectively.  相似文献   

9.
The positron lifetime and DSC measerments for EBBA and DOBAMBC have been made with heating and cooling clycles. The experimental results show that a shorter lifetime (1) is essentially independent of temperature while the longer lifetime (2) and the intensity (I 2) change abruptly double or triple with temperature. Consequently, the EBBA has only nematic phases while the DOBAMBC has two liquid-crystalline phases (smectic C* and smectic A) with transition temperatures as follows: for EBBA, solid nematic (304.5 K), nematic isotropic (356.5 K), isotropic nematic (356.5 K), nematic solid (301 K); and for DOBAMBC, solid smectic C* (346 K), smectic C* smectic A (357.5 K), smectic A isotropic (389 K). These critical temperatures are in accordance with the transition temperatures measured by DSC. In addition, the difference in the solid-nematic transition temperature in the heating and cooling cycles was also observed. A discussion about the correlation of the observed changes in lifetime (2) with the changes in molecular orientational order (S) and dielectric anisotropy () is presented.  相似文献   

10.
We consider the Dyson equation associated with the BCS superconducting state from a mathematical point of view. The Dyson equation gives rise to a modified gap equation that is similar to the BCS gap equation, but with a different kernel. We first show that for strong coupling (such that the McMillan parameter ||1) both the real and imaginary parts of the solution (E) of the modified gap equation alternate in sign as function of the excitation energyE, the periods being 40 for positive and 40/3 for negative . (0 is the frequency of an Einstein spectrum of phonons). A closed, algebraic approximation to (E) is 2||0log[cotan(E/ )]. Finally, the poles of the kernel of the integral equation are located in the complex-E plane. For the new-type, oscillatory solution of the modified gap equation the analogue of the causal (zero-temperature) Green's function is shown to have different analytic properties from those of the smooth Eliashberg solution of BCS theory.  相似文献   

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