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中国科学院国家科学图书馆机构知识库Fri, 23 Jun 2017 22:38:04 GMT2017-06-23T22:38:04ZGeneralized minimum dominating set and application in automatic text summarization
http://ir.itp.ac.cn/:80/handle/311006/21266
题名: Generalized minimum dominating set and application in automatic text summarization
作者: Xu, Yi-Zhi; Zhou, Hai-JunMon, 27 Feb 2017 06:31:42 GMThttp://ir.itp.ac.cn/:80/handle/311006/212662017-02-27T06:31:42ZThe rock-paper-scissors game
http://ir.itp.ac.cn/:80/handle/311006/21265
题名: The rock-paper-scissors game
作者: Zhou, HJ
摘要: Rock-Paper-Scissors (RPS), a game of cyclic dominance, is not merely a popular children's game but also a basic model system for studying decision-making in non-cooperative strategic interactions. Aimed at students of physics with no background in game theory, this paper introduces the concepts of Nash equilibrium and evolutionarily stable strategy, and reviews some recent theoretical and empirical efforts on the non-equilibrium properties of the iterated RPS, including collective cycling, conditional response patterns and microscopic mechanisms that facilitate cooperation. We also introduce several dynamical processes to illustrate the applications of RPS as a simplified model of species competition in ecological systems and price cycling in economic markets.Mon, 27 Feb 2017 06:31:41 GMThttp://ir.itp.ac.cn/:80/handle/311006/212652017-02-27T06:31:41ZA spin glass approach to the directed feedback vertex set problem
http://ir.itp.ac.cn/:80/handle/311006/21264
题名: A spin glass approach to the directed feedback vertex set problem
作者: Zhou, HJ
摘要: A directed graph (digraph) is formed by vertices and arcs (directed edges) from one vertex to another. A feedback vertex set (FVS) is a set of vertices that contains at least one vertex of every directed cycle in this digraph. The directed feedback vertex set problem aims at constructing a FVS of minimum cardinality. This is a fundamental cycle-constrained hard combinatorial optimization problem with wide practical applications. In this paper we construct a spin glass model for the directed FVS problem by converting the global cycle constraints into local arc constraints, and study this model through the replica-symmetric (RS) mean field theory of statistical physics. We then implement a belief propagation-guided decimation (BPD) algorithm for single digraph instances. The BPD algorithm slightly outperforms the simulated annealing algorithm on large random graph instances. The RS mean field results and algorithmic results can be further improved by working on a more restrictive (and more difficult) spin glass model.Mon, 27 Feb 2017 06:31:40 GMThttp://ir.itp.ac.cn/:80/handle/311006/212642017-02-27T06:31:40ZIdentifying optimal targets of network attack by belief propagation
http://ir.itp.ac.cn/:80/handle/311006/21263
题名: Identifying optimal targets of network attack by belief propagation
作者: Mugisha, S; Zhou, HJ
摘要: For a network formed by nodes and undirected links between pairs of nodes, the network optimal attack problem aims at deleting a minimum number of target nodes to break the network down into many small components. This problem is intrinsically related to the feedback vertex set problem that was successfully tackled by spin-glass theory and an associated belief propagation-guided decimation (BPD) algorithm [Zhou, Eur. Phys. J. B 86, 455 (2013)]. In the present work we apply the BPD algorithm (which has approximately linear time complexity) to the network optimal attack problem and demonstrate that it has much better performance than a recently proposed collective information algorithm [Morone and Makse, Nature 524, 65 (2015)] for different types of random networks and real-world network instances. The BPD-guided attack scheme often induces an abrupt collapse of the whole network, which may make it very difficult to defend.Mon, 27 Feb 2017 06:31:39 GMThttp://ir.itp.ac.cn/:80/handle/311006/212632017-02-27T06:31:39ZSpin-glass phase transitions and minimum energy of the random feedback vertex set problem
http://ir.itp.ac.cn/:80/handle/311006/21262
题名: Spin-glass phase transitions and minimum energy of the random feedback vertex set problem
作者: Qin, SM; Zeng, Y; Zhou, HJ
摘要: A feedback vertex set (FVS) of an undirected graph contains vertices from every cycle of this graph. Constructing a FVS of sufficiently small cardinality is very difficult in the worst cases, but for random graphs this problem can be efficiently solved by converting it into an appropriate spin-glass model [H.-J. Zhou, Eur. Phys. J. B 86, 455 (2013)]. In the present work we study the spin-glass phase transitions and the minimum energy density of the random FVS problem by the first-step replica-symmetry-breaking (1RSB) mean-field theory. For both regular random graphs and Erdos-Renyi graphs, we determine the inverse temperature beta(1) at which the replica-symmetric mean-field theory loses its local stability, the inverse temperature beta(d) of the dynamical (clustering) phase transition, and the inverse temperature beta(s) of the static (condensation) phase transition. These critical inverse temperatures all change with the mean vertex degree in a nonmonotonic way, and beta(d) is distinct from beta(s) for regular random graphs of vertex degrees K > 60, while beta(d) are identical to beta(s) for Erdos-Renyi graphs at least up to mean vertex degree c = 512. We then derive the zero-temperature limit of the 1RSB theory and use it to compute the minimum FVS cardinality.Mon, 27 Feb 2017 06:31:38 GMThttp://ir.itp.ac.cn/:80/handle/311006/212622017-02-27T06:31:38ZServing by local consensus in the public service location game
http://ir.itp.ac.cn/:80/handle/311006/21261
题名: Serving by local consensus in the public service location game
作者: Sun, YF; Zhou, HJ
摘要: We discuss the issue of distributed and cooperative decision-making in a network game of public service location. Each node of the network can decide to host a certain public service incurring in a construction cost and serving all the neighboring nodes and itself. A pure consumer node has to pay a tax, and the collected tax is evenly distributed to all the hosting nodes to remedy their construction costs. If all nodes make individual best-response decisions, the system gets trapped in an inefficient situation of high tax level. Here we introduce a decentralized local-consensus selection mechanism which requires nodes to recommend their neighbors of highest local impact as candidate servers, and a node may become a server only if all its non-server neighbors give their assent. We demonstrate that although this mechanism involves only information exchange among neighboring nodes, it leads to socially efficient solutions with tax level approaching the lowest possible value. Our results may help in understanding and improving collective problem-solving in various networked social and robotic systems.Mon, 27 Feb 2017 06:31:37 GMThttp://ir.itp.ac.cn/:80/handle/311006/212612017-02-27T06:31:37ZFast and simple decycling and dismantling of networks
http://ir.itp.ac.cn/:80/handle/311006/21260
题名: Fast and simple decycling and dismantling of networks
作者: Zdeborova, L; Zhang, P; Zhou, HJ
摘要: Decycling and dismantling of complex networks are underlying many important applications in network science. Recently these two closely related problems were tackled by several heuristic algorithms, simple and considerably sub-optimal, on the one hand, and involved and accurate message-passing ones that evaluate single-node marginal probabilities, on the other hand. In this paper we propose a simple and extremely fast algorithm, CoreHD, which recursively removes nodes of the highest degree from the 2-core of the network. CoreHD performs much better than all existing simple algorithms. When applied on real-world networks, it achieves equally good solutions as those obtained by the state-of-art iterative message-passing algorithms at greatly reduced computational cost, suggesting that CoreHD should be the algorithm of choice for many practical purposes.Mon, 27 Feb 2017 06:31:36 GMThttp://ir.itp.ac.cn/:80/handle/311006/212602017-02-27T06:31:36ZImplications of the first AMS-02 measurement for dark matter annihilation and decay
http://ir.itp.ac.cn/:80/handle/311006/21259
题名: Implications of the first AMS-02 measurement for dark matter annihilation and decay
作者: Jin, HB; Wu, YL; Zhou, YF
摘要: In light of the first measurement of the positron fraction by the AMS-02 experiment, we perform a detailed global analysis on the interpretation of the latest data of PAMELA, Fermi-LAT, and AMS-02 in terms of dark matter (DM) annihilation and decay in various propagation models. The allowed regions for the DM particle mass and annihilation cross section or decay life-time are obtained for channels with leptonic final states: 2e, 2 mu, 2 tau, 4e, 4 mu and 4 tau. We show that for the conventional astrophysical background the AMS-02 positron fraction data alone favour a DM particle mass similar to 500 (800) GeV if DM particles annihilate dominantly into 2 mu (4 mu) final states, which is significantly lower than that favoured by the Fermi-LAT data of the total flux of electrons and positrons. The allowed regions by the two experiments do not overlap at a high confidence level (99.99999%C.L.). We consider a number of propagation models with different halo height Z(h), diffusion parameters D-0 and delta(1/2), and power indices of primary nucleon sources gamma(p1/p2). The normalization and the slope of the electron background are also allowed to vary. We find that the tension between the two experiments can be only slightly reduced in the propagation model with large Z(h) and D-0. The consistency of fit is improved for annihilation channels with 2 tau and 4 tau final states which favour TeV scale DM particle with large cross sections above similar to 10(-23) cm(3)s(-1). In all the considered leptonic channels, the current data favour the scenario of DM annihilation over DM decay. In the decay scenario, the charge asymmetric DM decay is slightly favoured.Mon, 27 Feb 2017 01:57:19 GMThttp://ir.itp.ac.cn/:80/handle/311006/212592017-02-27T01:57:19ZMultidimensionally-constrained relativistic mean-field models and potential-energy surfaces of actinide nuclei
http://ir.itp.ac.cn/:80/handle/311006/21258
题名: Multidimensionally-constrained relativistic mean-field models and potential-energy surfaces of actinide nuclei
作者: Lu, BN; Zhao, J; Zhao, EG; Zhou, SG
摘要: Background: Many different shape degrees of freedom play crucial roles in determining the nuclear ground state and saddle point properties and the fission path. For the study of nuclear potential energy surfaces, it is desirable to have microscopic and self-consistent models in which all known important shape degrees of freedom are included. Purpose: By breaking both the axial and the spatial reflection symmetries simultaneously, we develop multidimensionally-constrained relativistic mean field (MDC-RMF) models. Methods: The nuclear shape is assumed to be invariant under the reversion of x and y axes, i.e., the intrinsic symmetry group is V-4 and all shape degrees of freedom beta(lambda mu) with even mu, such as beta(20), beta(22), beta(30), beta(32), beta(40), ..., are included self-consistently. The single-particle wave functions are expanded in an axially deformed harmonic oscillator (ADHO) basis. The RMF functional can be one of the following four forms: the meson exchange or point-coupling nucleon interactions combined with the nonlinear or density- dependent couplings. The pairing effects are taken into account with the BCS approach. Results: The one-, two, and three-dimensional potential energy surfaces of Pu-240 are illustrated for numerical checks and for the study of the effect of the triaxiality on the fission barriers. Potential energy curves of even-even actinide nuclei around the first and second fission barriers are studied systematically. Besides the first ones, the second fission barriers in these nuclei are also lowered considerably by the triaxial deformation. This lowering effect is independent of the effective interactions used in the RMF functionals. Further discussions are made about different predictions on the effect of the triaxiality between the macroscopic-microscopic and MDC-RMF models, possible discontinuities on PES's from self-consistent approaches, and the restoration of broken symmetries. Conclusions: MDC-RMF models give a reasonably good description of fission barriers of even-even actinide nuclei. It is important to include both the nonaxial and the reflection asymmetric shapes simultaneously for the study of potential energy surfaces and fission barriers of actinide nuclei and of those in unknown mass regions such as, e.g., superheavy nuclei.Mon, 27 Feb 2017 01:57:18 GMThttp://ir.itp.ac.cn/:80/handle/311006/212582017-02-27T01:57:18ZSuperdeformed Lambda hypernuclei within relativistic mean field models
http://ir.itp.ac.cn/:80/handle/311006/21257
题名: Superdeformed Lambda hypernuclei within relativistic mean field models
作者: Lu, BN; Hiyama, E; Sagawa, H; Zhou, SG
摘要: We study the superdeformed (SD) states and corresponding SD hypernuclei of Ar isotopes with the multidimensionally constrained relativistic mean field (MDC-RMF) models, which can accommodate various shape degree of freedom. We found that the density profiles of SD states in Ar isotopes show a strong localization with a ring structure near the surface, while the central part of the density is dilute, showing a hole structure. This localization of SD density induces an appreciable deformation in the hyperon wave function and results in a large overlap between the core and the hyperon in the SD hypernuclei of Ar isotopes. Then the Lambda separation energy of the SD state becomes larger than that of a normally deformed or spherical ground state. This feature is different from that found in other nuclei such as S-32, Ni-56, and Zn-60 in which the Lambda separation energy of larger deformed state is smaller. In this context, the measurement of the Lambda separation energy may provide important information on the localization of the density profile of SD states.Mon, 27 Feb 2017 01:57:17 GMThttp://ir.itp.ac.cn/:80/handle/311006/212572017-02-27T01:57:17Z