共查询到20条相似文献,搜索用时 93 毫秒
1.
The angular variations of the five-fold differential cross section obtained by using different wave functions of helium are
compared with experimental data. It is found that in the coplanar geometry two kinematical arrangements, (i) equal energy
sharing between the two ejected electrons with one of them ejected along the momentum transfer direction and the other along
varying direction and (ii) the Bethe ridge condition with fixed sum of ejected electron energies and varying angle between
them, are very sensitive to e-e correlations contained in the target wave function. This comparison has been used to show
that open-shell class of wave functions better incorporate e-e correlations than the closed-shell class. 相似文献
2.
In this paper, we investigate how much of the numerical artefacts introduced by finite system size and choice of boundary conditions can be removed by finite size scaling, for strongly correlated systems with quasi-long-range order. Starting from the exact ground-state wave functions of hardcore bosons and spinless fermions with infinite nearest-neighbor repulsion on finite periodic chains and finite open chains, we compute the two-point, density-density, and pair-pair correlation functions, and fit these to various asymptotic power laws. Comparing the finite-periodic-chain and finite-open-chain correlations with their infinite-chain counterparts, we find reasonable agreement among them for the power-law amplitudes and exponents, but poor agreement for the phase shifts. More importantly, for chain lengths on the order of 100, we find our finite-open-chain calculation overestimates some infinite-chain exponents (as did a recent density-matrix renormalization-group (DMRG) calculation on finite smooth chains), whereas our finite-periodic-chain calculation underestimates these exponents. We attribute this systematic difference to the different choice of boundary conditions. Eventually, both finite-chain exponents approach the infinite-chain limit: by a chain length of 1000 for periodic chains, and >2000 for open chains. There is, however, a misleading apparent finite size scaling convergence at shorter chain lengths, for both our finite-chain exponents, as well as the finite-smooth-chain exponents. Implications of this observation are discussed. 相似文献
3.
Dušanka Leki?Sun?ica Elezovi?-Had?i? 《Physica A》2011,390(11):1941-1952
Semi-flexible compact polymers modeled by Hamiltonian walks with bending rigidity are studied on 3 and 4-simplex fractal lattices. Hamiltonian walks are weighted according to the number of bends in the walk, and total weights are obtained by an exact recursive treatment. Asymptotic form of the partition function, with temperature dependent scaling parameters, as well as the corresponding critical exponents, is determined. Various thermodynamic quantities are calculated numerically and presented graphically, and the possibility of phase transition between a compact molten globule and an ordered ‘crystal’ state is investigated. No phase transition is found on either of these two lattices, meaning that fractal geometry here prevents any kind of orientational order. 相似文献
4.
Le Doussal P 《Physical review letters》2006,96(23):235702
We study, using functional renormalization, two copies of an elastic system pinned by mutually correlated random potentials. Short scale decorrelation depends on a nontrivial boundary layer regime with (possibly multiple) chaos exponents. Large scale mutual displacement correlations behave as [x - x'](2zeta-mu), mu proportional to the difference between Flory (or mean field) and exact roughness exponents zeta. For short range disorder mu>0 and small; e.g., for random bond interfaces mu=5zeta-epsilon, epsilon=4-d, and mu=epsilon{[(2pi)(2)/36]-1} for the one component Bragg glass. Random field (i.e., long range) disorder exhibits finite residual correlations (no chaos mu=0) described by new functional renormalization fixed points. Temperature and dynamic chaos (depinning) are discussed. 相似文献
5.
Einert TR Sing CE Alexander-Katz A Netz RR 《The European physical journal. E, Soft matter》2011,34(12):130-16
We study the conformational dynamics within homopolymer globules by solvent-implicit Brownian dynamics simulations. A strong
dependence of the internal chain dynamics on the Lennard-Jones cohesion strength e \varepsilon and the globule size N
G is observed. We find two distinct dynamical regimes: a liquid-like regime (for e \varepsilon < es \varepsilon_{{\rm s}}^{} with fast internal dynamics and a solid-like regime (for e \varepsilon > es \varepsilon_{{\rm s}}^{} with slow internal dynamics. The cohesion strength es \varepsilon_{{\rm s}}^{} of this freezing transition depends on N
G . Equilibrium simulations, where we investigate the diffusional chain dynamics within the globule, are compared with non-equilibrium
simulations, where we unfold the globule by pulling the chain ends with prescribed velocity (encompassing low enough velocities
so that the linear-response, viscous regime is reached). From both simulation protocols we derive the internal viscosity within
the globule. In the liquid-like regime the internal friction increases continuously with e \varepsilon and scales extensive in N
G . This suggests an internal friction scenario where the entire chain (or an extensive fraction thereof) takes part in conformational
reorganization of the globular structure. 相似文献
6.
Extensive Monte Carlo data analysis gives clear evidence that collapsed linear polymers in two dimensions fall in the universality class of athermal, dense self-avoiding walks, as conjectured by Duplantier [Phys. Rev. Lett. 71, 4274 (1993)].10.1103/PhysRevLett.71.4274 However, the boundary of the globule has self-affine roughness and does not determine the anticipated nonzero topological boundary contribution to entropic exponents. Scaling corrections are due to subleading contributions to the partition function corresponding to polymer configurations with one end located on the globule-solvent interface. 相似文献
7.
By considering the Kane-Mele-Hubbard approximation on the honeycomb lattice, we investigate the spin-spin correlation for two magnetic impurities in zigzag edge silicene-like nanoflake (ZSiLF). The dependence of the spatial behaviors of RKKY interaction on the electron-electron (e-e), intrinsic spin-orbit interactions (ISOI) and, electric field are systematically investigated. Generally, the spatial behaviors of the RKKY interaction sensitively change by changing e-e interaction and electric field strengths in the presence of ISOI. The ISOI in a ZSiLF result in long-range in-plane and Ising interactions. Moreover, e-e interaction induces non-zero Dzyaloshinsky-Moriya (DM) term and nearly distance-independent Ising interaction (similar to graphene nanoflake) in the presence of ISOI. Furthermore, with considering e-e interaction, the in-plane DM interaction increases by increasing the strengths of the electric field and ISOI. 相似文献
8.
S. Müller L. Schäfer 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(3):351-369
We give a detailed analysis of the intersection properties of polymers. Using the renormalization group we provide a full
crossover function for the dependence of the number of intersections in a single polymer on chain length and excluded volume
strength. We compare our results with Monte-Carlo data and with exact calculations for a random walk, finding good agreement
in all respects. Restricting to the vicinity of the eight ternary fixed points we also calculate the number of intersections
between two chains placed at a fixed distance, including the two halves of a block-copolymer. The analysis of these systems
confirms the interpretation of the different contributions to the number of intersections in a single chain. Due to the highly
nontrivial character of the correlations in a polymer chain the correction exponents in both cases however are different.
None of the results can be extracted from any Flory-type estimate.
Received: 1 April 1997 / Revised: 24 October 1997 /
Accepted: 29 January 1998 相似文献
9.
Using particle simulations of the uniform shear flow of a rough dilute granular gas, we show that the translational and rotational velocities are strongly correlated in direction, but there is no orientational correlation-induced singularity at perfectly smooth (beta=-1) and rough (beta=1) limits for elastic collisions (e=1); both the translational and rotational velocity distribution functions remain close to a Gaussian for these two limiting cases. Away from these two limits, the orientational as well as spatial velocity correlations are responsible for the emergence of non-Gaussian high-velocity tails. The tails of both distribution functions follow stretched exponentials, with the exponents depending on normal (e) and tangential (beta) restitution coefficients. 相似文献
10.
Recent studies of correlations of intensity in databases of natural images revealed a remarkable property. The two point correlations are described in terms of power law behavior, with an exponent which seems to be robust. In the present Letter we consider the statistical meaning of that result. We study many individual images of one of the databases considered. We find that the same law characterizing the correlations in the whole database governs also images randomly chosen from that database, with one essential difference. The exponent characterizing each image is specific and differs from the exponent characterizing the whole database. The distribution of single image exponents has been measured and found to exhibit a rather heavy tail. The database exponent cannot, thus, be considered as a statistical representative of a single image exponent. Possible reasons for the diversity in image exponents are discussed. 相似文献
11.
The decay of the collisional contribution to the shear-stress autocorrelation function is shown to be inconsistent with at
–3/2 inverse-power law. The decay of the self part (a combination of pair and triplet correlations) indicates a stretched-exponential decay with a density-independent exponent. The pair contribution by itself also shows stretched-exponential behavior in both two and three dimensions, with different, but still density-independent, exponents. At very long times this stretched-exponential decay of the pair correlations switches over to an algebraic decay, consistent with the diffusional separation of pairs of particles. 相似文献
12.
J. Lermé G. Celep M. Broyer E. Cottancin M. Pellarin A. Arbouet D. Christofilos C. Guillon P. Langot N. Del Fatti F. Vallée 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2005,34(1-3):199-204
Effects of confinement on the electron-electron (e-e) and electron-phonon (e-ph) thermalization dynamics in noble metal clusters are calculated using simple approaches. The model predictions are compared with femtosecond pump-probe measurements which display an acceleration of the e-e and e-ph relaxation dynamics. The size-effects on the e-e relaxation dynamics are consistent with a model involving the surface-induced reduction of the screening efficiency of the Coulomb e-e interaction. With regard to the e-ph relaxation dynamics, this model yields too large time constants, pointing out deficiencies of the standard modelling of the e-ph energy exchanges in bulk metals. Analysis of these deficiencies shows that the bare e-ion interaction has to be involved in the transition matrix element describing the non-adiabatic e-ph energy exchanges. 相似文献
13.
We study theoretically the alternating current (ac) transport property through a two-channel clean quantum wire of finite length in the presence of both inter-channel and intra-channel electron-electron (e-e) interactions. Using the bosonization technique and linear response theory, we have obtained analytical expressions of the ac conductance. Interestingly, the ac conductance oscillations, with two different frequencies, form a beat which governs the behavior of the transport property in the presence of inter-channel e-e interaction. This result provides us with a new way to control the transport property of narrow quantum wires by engineering the Fermi velocities in the two different channels, i.e., the electron density. 相似文献
14.
Ferrier M Rowe AC Guéron S Bouchiat H Texier C Montambaux G 《Physical review letters》2008,100(14):146802
We investigate weak localization in metallic networks etched in a two-dimensional electron gas between 25 and 750 mK when electron-electron (e-e) interaction is the dominant phase breaking mechanism. We show that, at the highest temperatures, the contributions arising from trajectories that wind around the rings and trajectories that do not are governed by two different length scales. This is achieved by analyzing separately the envelope and the oscillating part of the magnetoconductance. For T > or approximately 0.3 K we find L phi env proportional T(-1/3) for the envelope and L phi osc proportional, T(-1/2) for the oscillations, in agreement with the prediction for a single ring [T. Ludwig and A. D. Mirlin, Phys. Rev. B 69, 193306 (2004); 10.1103/PhysRevB.69.193306C. Texier and G. Montambaux, Phys. Rev. B 72, 115327 (2005); 10.1103/PhysRevB.72.115327C. Texier, Phys. Rev. B76, 153312 (2007)10.1103/PhysRevB.76.153312]. This is the first experimental confirmation of the geometry dependence of decoherence due to e-e interaction. 相似文献
15.
16.
Employing the multifractal detrended fluctuation analysis (MF-DFA), the multifractal properties of trading behavior of individual and institutional traders in the Tehran Stock Exchange (TSE) are numerically investigated. Using daily trading volume time series of these two categories of traders, the scaling exponents, generalized Hurst exponents, generalized fractal dimensions and singularity spectrum are derived. Furthermore, two main sources of multifractality, i.e. temporal correlations and fat-tailed probability distributions are also examined. We also compare our results with data of S&P 500. Results of this paper suggest that for both classes of investors in TSE, multifractality is mainly due to long-range correlation while for S&P 500, the fat-tailed probability distribution is the main source of multifractality. 相似文献
17.
A phase diagram for a surface-interacting long flexible partially-directed polymer chain in a two-dimensional poor solvent, where the possibility of collapse in the bulk exists, is determined using exact enumeration methods. We used a model of self-attracting self-avoiding walks and evaluated 30 steps in series. An intermediate phase between the desorbed collapsed and adsorbed expanded phases, having the conformation of a surface-attached globule, is found. The four phases, viz ., (i) desorbed expanded (DE), (ii) desorbed collapsed (DC), (iii) adsorbed expanded (AE), (iv) surface-attached globule (SAG), are found to meet at a multicritical point. These features are in agreement with those of an isotropic (or non-directed) polymer chain. 相似文献
18.
19.
Arbieto Alexander Matheus Carlos Pacifico Maria José 《Journal of statistical physics》2004,117(1-2):243-260
A dynamical system is called partially hyperbolic if it exhibits three invariant directions, one unstable (expanding), one stable (contracting) and one central direction (somewhere in between the other two). We prove that topologically mixing partially hyperbolic diffeomorphisms whose central direction is non-uniformly contracting (negative Lyapunov exponents) almost everywhere have the Bernoulli property: the system is equivalent to an i. i. d. (independently identically distributed) random process. In particular, these systems are mixing: correlations of integrable functions go to zero as time goes to infinity. We also extend this result in two different ways. Firstly, for 3-dimensional diffeomorphisms, if one requires only non-zero (instead of negative) Lyapunov exponents then one still gets a quasi-Bernoulli property. Secondly, if one assumes accessibility (any two points are joined by some path whose legs are stable segments and unstable segments) then it suffices to requires the mostly contracting property on a positive measure subset, to obtain the same conclusions. 相似文献
20.
A. Yu. Grosberg 《Journal of statistical physics》1985,38(1-2):149-160
The collapse (globulization) of an ideal heteropolymer chain under the action of an external attractive field is considered. The problem of the collapse of different types of primary structures, including mobile, periodic, large-block, and statistical structures, is formulated. It is shown that for a random heteropolymer, the mathematical image of the globular state is the chain-length independence of the probability distribution of a random thermal distribution function of the end monomer coordinates. The free energy per monomer of a chain in a globular state and local densities of monomers of all types are shown to be a self-averaging quantities. An exactly solvable model is proposed for a globule formed by a statistical heteropolymer chain. In this model, different types of monomers are attracted to different centers by linear elastic forces with identical elastic constants. The modulus of elasticity is obtained for a heteropolymer globule with respect to the attraction of different types of monomers in different directions. It is shown that this modulus is higher for a short-periodic polymer than for a statistical one. 相似文献