Interspecific competition underlying mutualistic networks

Multiple classes of interactions may exist affecting one another in a given system. For the mutualistic networks of plants and pollinating animals, it has been known that the degree distribution is broad but often deviates from power-law form more significantly for plants than animals. To illuminate the origin of such asymmetry, we study a model network in which links are assigned under generalized preferential-selection rules between two groups of nodes and find the sensitive dependence of the resulting connectivity pattern on the model parameters. The nonlinearity of preferential selection can come from interspecific interactions among animals and among plants. The model-based analysis of real-world mutualistic networks suggests that a new animal determines its partners not only by their abundance but also under the competition with existing animal species, which leads to the stretched-exponential degree distributions of plants.     

Asymmetry through time dependency

Given a single network of interactions, asymmetry arises when the links aredirected. For example, if protein A upregulates protein B and protein Bupregulates protein C, then (in the absence of any further relationships between them) Amay affect C but not vice versa. This type of imbalance is reflected in the associatedadjacency matrix, which will lack symmetry. A different type of imbalance can arise wheninteractions appear and disappear over time. If A meets B today and B meets C tomorrow,then (in the absence of any further relationships between them) A may pass a message ordisease to C, but not vice versa. Hence, even when each interaction is a two-way exchange,the effect of time ordering can introduce asymmetry. This observation is very closelyrelated to the fact that matrix multiplication is not commutative. In this work, wedescribe a method that has been designed to reveal asymmetry in static networks and showhow it may be combined with a measure that summarizes the potential information flowbetween nodes in the temporal case. This results in a new method that quantifies theasymmetry arising through time ordering. We show by example that the new tool can be usedto visualize and quantify the amount of asymmetry caused by the arrow of time.     

一类异构多智能体系统固定和切换拓扑下的一致性分析

对包含一阶二阶智能体的异构系统有向图中的一致性问题进行研究.对该系统采用了一种线性分布式一致性协议,基于图论和矩阵分析的方法,分析了在固定和切换拓扑情况下系统获得一致性的充分条件,该条件与控制参数和通信拓扑有关.给出了固定拓扑中系统的一致平衡点,证明了仅通信拓扑中的根节点对平衡点起作用.数值仿真验证了理论分析的正确性.     

Mössbauer effect studies of some trimeric iron compounds

Mössbauer spectra of some basic iron (III) carboxylates are reported. The zero field spectra are quadrupole doublets with a characteristic temperature dependent asymmetry. In applied magnetic fields at 4·2°K large hyperfine magnetic fields are observed. These can only result from a Hamiltonian which is not symmetric in all three sites. This asymmetry may be due to a structural asymmetry or to small intercluster magnetic interactions.     

Synchronization in complex networks with age ordering

The propensity for synchronization is studied in a complex network of asymmetrically coupled units, where the asymmetry in a given link is determined by the relative age of the involved nodes. In growing scale-free networks, synchronization is enhanced when couplings from older to younger nodes are dominant. We describe the requirements for such an effect in a more general context and compare with the situations in nongrowing random networks with and without a degree ordering.     

Social power and opinion formation in complex networks

In this paper we investigate the effects of social power on the evolution of opinions in model networks as well as in a number of real social networks. A continuous opinion formation model is considered and the analysis is performed through numerical simulation. Social power is given to a proportion of agents selected either randomly or based on their degrees. As artificial network structures, we consider scale-free networks constructed through preferential attachment and Watts–Strogatz networks. Numerical simulations show that scale-free networks with degree-based social power on the hub nodes have an optimal case where the largest number of the nodes reaches a consensus. However, given power to a random selection of nodes could not improve consensus properties. Introducing social power in Watts–Strogatz networks could not significantly change the consensus profile.     

Leptogenesis from spin-gravity coupling following inflation

The energy levels of the left- and the right-handed neutrinos are split in the background of gravitational waves generated during inflation, which, in presence of lepton-number-violating interactions, gives rise to a net lepton asymmetry at equilibrium. Lepton number violation is achieved by the same dimension five operator which gives rise to neutrino masses after electroweak symmetry breaking. A net baryon asymmetry of the same magnitude can be generated from this lepton asymmetry by electroweak sphaleron processes.     

Electric induction interactions between molecules through fifth-order perturbation theory

Electric induction interactions in a system of N molecules of arbitrary asymmetry are examined in the first five orders of non-degenerate perturbation theory. The results are used to evaluate fourth-order induction interactions between two hydrogen fluoride molecules     

Leptogenesis and composite heavy neutrinos with gauge-mediated interactions

Leptogenesis is an appealing framework to account for the baryon asymmetry in the universe. To this end physics beyond the standard model is demanded. In this paper we investigate the possibility to attain successful leptogenesis with composite Majorana neutrinos. We work in the framework of effective gauge-mediated and contact interactions without any reference to an underlying compositeness theory. This approach is the one adopted in all current experimental searches for composite fermions at colliders. In the case of gauge-mediated interactions, we calculate the CP asymmetry in heavy composite neutrino decays. Both the direct and the indirect CP asymmetry are derived and resonant leptogenesis is also discussed. We find that the Sakharov conditions can be met and, for some choice of the parameters, the correct order of magnitude of the baryon asymmetry is reproduced.     

A simple consensus algorithm for distributed averaging in random geographical networks

Random geographical networks are realistic models for wireless sensor networks which are used in many applications. Achieving average consensus is very important in sensor networks and the faster the consensus is, the durable the sensors?? life, and thus, the better the performance of the network. In this paper we compared the performance of a number of linear consensus algorithms with application to distributed averaging in random geographical networks. Interestingly, the simplest algorithm ?C where only the degree of receiving nodes is needed for the averaging ?C had the best performance in terms of the consensus time. Furthermore, we proved that the network has guaranteed convergence with this simple algorithm.     

Charge asymmetry in inelastic π−p interactions at 205 GeV/c for particles with transverse momentum > 1.0 GeVc

In 205 GeV/cπ^?p inelastic interactions, negative particles with transverse momentum greater than 1.0 GeV/c moving forward in the center of mass outnumber similar positive particles by a factor of 3.7 to 1, greatly in excess of the corresponding ratio for small transverse momentum. The asymmetry is reversed in the backward direction. The forward asymmetry is most prominent in 2-, 4-, and 6-prong interactions, but both forward and backward asymmetries are also substantial for higher multiplicity interactions.     

Quantum leptogenesis I

Thermal leptogenesis explains the observed matter–antimatter asymmetry of the universe in terms of neutrino masses, consistent with neutrino oscillation experiments. We present a full quantum mechanical calculation of the generated lepton asymmetry based on Kadanoff–Baym equations. Origin of the asymmetry is the departure from equilibrium of the statistical propagator of the heavy Majorana neutrino, together with CP violating couplings. The lepton asymmetry is calculated directly in terms of Green’s functions without referring to “number densities”. Compared to Boltzmann and quantum Boltzmann equations, the crucial difference are memory effects, rapid oscillations much faster than the heavy neutrino equilibration time. These oscillations strongly suppress the generated lepton asymmetry, unless the standard model gauge interactions, which cause thermal damping, are properly taken into account. We find that these damping effects essentially compensate the enhancement due to quantum statistical factors, so that finally the conventional Boltzmann equations again provide rather accurate predictions for the lepton asymmetry.     

Importance of the heavier singlet neutrinos in leptogenesis

We argue that fast interactions of the lightest singlet neutrino N1 would project part of a preexisting lepton asymmetry L{p} onto a direction that is protected from N1 washout effects, thus preventing it from being erased. In particular, we consider an asymmetry generated in N2 decays, assuming that N1 interactions are fast enough to bring N1 into full thermal equilibrium. If N1 decays occur at T > or = 10{9} GeV, that is, before the muon Yukawa interactions enter into thermal equilibrium, then generically part of L{p} survives. In this case some of the constraints implied by the standard N1 leptogenesis scenario hold only if L{p} approximately 0. For T < or = 10{9} GeV, L{p} is generally erased, unless special alignment or orthogonality conditions in flavor space are realized.     

Consensus problem in multi-agent systems with physical position neighbourhood evolving network

In multi-agent system (MAS), the communication topology of agent network plays a very important role in its consensus problem. To describe the communication topologies of MAS, a class of evolving network models with the concept of physical position neighbourhood connectivity are proposed and studied in this paper. The analysis and simulation results for network parameters such as the first nonzero eigenvalue and maximal eigenvalue of graph Laplacian matrix, clustering coefficients, average distances and degree distributions for different evolving parameters of these models are presented. The dynamical behaviour of each node on the consensus problem is also studied. It was found that the time to reach consensus becomes shorter sharply with the increasing of neighbourhood depth of the nodes in these models. And it was also found that for the maximal distance preferential attachment model (Model 3), the synthetic characteristic, such as robustness to communication delay, as well as convergence speed in consensus problem, is the best in all these models.     

Weak neutral-current effects in electron-scattering coincidence experiments

Using a recently developed helicity analysis of electron-scattering coincidence experiments, we derive general expressions for the asymmetry in the coincidence cross section with polarized incident electrons. The asymmetry cross section is expressed in terms of the helicity components of the electromagnetic and weak neutral currents in the center-of-momentum frame. The asymmetry arises from an interference between the electromagnetic and weak neutral currents and from parity admixtures in the nuclear wave functions. In the limit of heavy, static nuclei, connection can be made to the usual multipole matrix elements of the electromagnetic and weak interactions. Some simple examples are discussed for the case where the reaction proceeds through a single intermediate resonance.     

Tackling Information Asymmetry in Networks: A New Entropy-Based Ranking Index

Information is a valuable asset in socio-economic systems, a significant part of which is entailed into the network of connections between agents. The different interlinkages patterns that agents establish may, in fact, lead to asymmetries in the knowledge of the network structure; since this entails a different ability of quantifying relevant, systemic properties (e.g. the risk of contagion in a network of liabilities), agents capable of providing a better estimation of (otherwise) inaccessible network properties, ultimately have a competitive advantage. In this paper, we address the issue of quantifying the information asymmetry of nodes: to this aim, we define a novel index—InfoRank—intended to rank nodes according to their information content. In order to do so, each node ego-network is enforced as a constraint of an entropy-maximization problem and the subsequent uncertainty reduction is used to quantify the node-specific accessible information. We, then, test the performance of our ranking procedure in terms of reconstruction accuracy and show that it outperforms other centrality measures in identifying the “most informative” nodes. Finally, we discuss the socio-economic implications of network information asymmetry.

     

Essentially nonequilibrium steady state of atoms in an optical field

The kinetics of atoms in the monochromatic field of a standing wave has been considered taking into account the recoil effects that appear under the interaction of the atoms with photons of the field. It has been shown that the steady-state solution of the kinetic equation for the atomic density matrix can have considerable asymmetry in the phase space. There is also asymmetry in the fluxes of atoms in the ground and excited states, predominantly near the nodes of the optical field.     

Normal thermal conduction in lattice models with asymmetric harmonic interparticle interactions

We study the thermal conduction behaviors of one-dimensional lattice models with asymmetric harmonic interparticle interactions. Normal thermal conductivity that is independent of system size is observed when the lattice chains are long enough. Because only the harmonic interactions are involved, the result confirms, without ambiguity, that asymmetry plays a key role in normal thermal conduction in one-dimensional momentum conserving lattices. Both equilibrium and nonequilibrium simulations are performed to support the conclusion.     

Asymmetries in the nonmesonic weak decay of polarized lambda hypernuclei

The nonmesonic weak decay of polarized Lambda hypernuclei is studied for the first time by taking into account, with a Monte Carlo intranuclear cascade code, the nucleon final state interactions. A one-meson-exchange model is employed to describe the Lambda-->N-->nN processes in a finite nucleus framework. The relationship between the intrinsic Lambda asymmetry parameter a(Lambda) and the asymmetry a(M)(Lambda) accessible in experiments is discussed. A strong dependence of a(M)(Lambda) on nucleon final state interactions and detection threshold is obtained. Our results for a(M)(Lambda) are consistent with (11)(Lambda)B--> and (12)(Lambda)C--> data but disagree with observations in (5)(Lambda)H-->e.     

Weak interaction asymmetries in pp̄ colliding beams

Charge asymmetry and polarization effects in lepton pair production in pp? collisions are investigated in order to distinguish between the standard unified model of electromagnetic and weak interactions and possible alternatives.