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排序方式: 共有172条查询结果,搜索用时 15 毫秒
111.
Peleg O Bartal G Freedman B Manela O Segev M Christodoulides DN 《Physical review letters》2007,98(10):103901
We study wave dynamics in honeycomb photonic lattices, and demonstrate the unique phenomenon of conical diffraction around the singular diabolical (zero-effective-mass) points connecting the first and second bands. This constitutes the prediction and first experimental observation of conical diffraction arising solely from a periodic potential. It is also the first study on k space singularities in photonic lattices. In addition, we demonstrate "honeycomb gap solitons" residing in the gap between the second and the third bands, reflecting the special properties of these lattices. 相似文献
112.
For any D-dimensional quantum lattice system, the fidelity between two ground state many-body wave functions is mapped onto the partition function of a D-dimensional classical statistical vertex lattice model with the same lattice geometry. The fidelity per lattice site, analogous to the free energy per site, is well defined in the thermodynamic limit and can be used to characterize the phase diagram of the model. We explain how to compute the fidelity per site in the context of tensor network algorithms, and demonstrate the approach by analyzing the two-dimensional quantum Ising model with transverse and parallel magnetic fields. 相似文献
113.
We study, theoretically and experimentally, the nonlinear dynamics of a wave packet launched inside a trap potential. Increasing the power of the wave packet transforms its dynamics from linear tunneling through a potential barrier, to soliton tunneling, and eventually, above a well-defined threshold, to the ejection of a soliton from the potential trap. 相似文献
114.
A double-sided variant of the information bottleneck method is considered. Let be a bivariate source characterized by a joint pmf . The problem is to find two independent channels and (setting the Markovian structure ), that maximize subject to constraints on the relevant mutual information expressions: and . For jointly Gaussian and , we show that Gaussian channels are optimal in the low-SNR regime but not for general SNR. Similarly, it is shown that for a doubly symmetric binary source, binary symmetric channels are optimal when the correlation is low and are suboptimal for high correlations. We conjecture that Z and S channels are optimal when the correlation is 1 (i.e., ) and provide supporting numerical evidence. Furthermore, we present a Blahut–Arimoto type alternating maximization algorithm and demonstrate its performance for a representative setting. This problem is closely related to the domain of biclustering. 相似文献
115.
Eran Bouchbinder Itamar Procaccia Shani Sela 《Journal of statistical physics》2006,125(5-6):1025-1064
Experiments on fracture surface morphologies offer increasing amounts of data that can be analyzed using methods of statistical
physics. One finds scaling exponents associated with correlation and structure functions, indicating a rich phenomenology
of anomalous scaling. We argue that traditional models of fracture fail to reproduce this rich phenomenology and new ideas
and concepts are called for. We present some recent models that introduce the effects of deviations from homogeneous linear
elasticity theory on the morphology of fracture surfaces, successfully reproducing the multiscaling phenomenology at least
in 1+1 dimensions. For surfaces in 2+1 dimensions we introduce novel methods of analysis based on projecting the data on the
irreducible representations of the SO(2) symmetry group. It appears that this approach organizes effectively the rich scaling
properties. We end up proposing new experiments in which the rotational symmetry is not broken, such that the scaling properties
should be particularly simple. 相似文献
116.
Z. Sela 《Geometric And Functional Analysis》2006,16(3):707-730
This paper is the sixth in a sequence on the structure of sets of solutions to systems of equations in a free group, projections
of such sets, and the structure of elementary sets defined over a free group. In the sixth paper we use the quantifier elimination
procedure presented in the two parts of the fifth paper in the sequence, to answer some of A. Tarski’s problems on the elementary
theory of a free group, and to classify finitely generated (f.g.) groups that are elementarily equivalent to a non-abelian
f.g. free group.
Received (resubmission): January 2004 Revision: January 2006 Accepted: January 2006
Partially supported by an Israel Academy of Sciences fellowship. 相似文献
117.
Z. Sela 《Geometric And Functional Analysis》2006,16(3):537-706
This paper is the sixth in a sequence on the structure of sets of solutions to systems of equations in a free group, projections
of such sets, and the structure of elementary sets defined over a free group. In the two papers on quantifier elimination
we use the iterative procedure that validates the correctness of an AE sentence defined over a free group, presented in the fourth paper, to show that the Boolean algebra of AE sets defined over a free group is invariant under projections, hence, show that every elementary set defined over a free
group is in the Boolean algebra of AE sets. The procedures we use for quantifier elimination, presented in this paper, enable us to answer affirmatively some of
Tarski’s questions on the elementary theory of a free group in the last paper of this sequence.
Received (resubmission): January 2004 Revision: November 2005 Accepted: March 2006
Partially supported by an Israel Academy of Sciences Fellowship. 相似文献
118.
Nonlinear Dynamics - The Twistcar vehicle is a classic example of a nonholonomic dynamical system. The vehicle model consists of two rigid links connected by an actuated rotary joint and supported... 相似文献
119.
Yizhar Or 《Regular and Chaotic Dynamics》2014,19(1):64-80
Painlevé’s paradox occurs in the rigid-body dynamics of mechanical systems with frictional contacts at configurations where the instantaneous solution is either indeterminate or inconsistent. Dynamic jamming is a scenario where the solution starts with consistent slippage and then converges in finite time to a configuration of inconsistency, while the contact force grows unbounded. The goal of this paper is to demonstrate that these two phenomena are also relevant to the field of robotic walking, and can occur in two classical theoretical models of passive dynamic walking — the rimless wheel and the compass biped. These models typically assume sticking contact and ignore the possibility of foot slippage, an assumption which requires sufficiently large ground friction. Nevertheless, even for large friction, a perturbation that involves foot slippage can be kinematically enforced due to external forces, vibrations, or loose gravel on the surface. In this work, the rimless wheel and compass biped models are revisited, and it is shown that the periodic solutions under sticking contact can suffer from both Painlevé’s paradox and dynamic jamming when given a perturbation of foot slippage. Thus, avoidance of these phenomena and analysis of orbital stability with respect to perturbations that include slippage are of crucial importance for robotic legged locomotion. 相似文献
120.