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This paper presents a well-balanced numerical scheme for solving free surface flows involving wetting and drying. The proposed algorithm combines a component-wise approach with hydrostatic reconstruction strategy to compute flows over wet or dry surfaces and to satisfy the steady state condition of still water. The robustness of the proposed scheme is verified under several benchmark hydraulic tests.
The goal of this paper is to analyze the effective behavior of the solution of a wave equation with interior and boundary damping, defined in a periodically perforated medium. We deal, at the microscale, with an {epsilon}-periodic structure obtained by removing from a bounded connected open set {Omega} in R{sup n} a number of closed subsets of characteristic size {epsilon}. As a result, we obtain a perforated domain {Omega}{sup {epsilon}}, in which we consider a wave equation, with interior sources and damping and with dynamic boundary conditions imposed on the boundaries of the perforations. Assuming suitable initial conditions, we prove that the asymptotic behavior, as the small parameter e which characterizes the size of the perforations tends to zero, of the solution of such a problem is governed by a parabolic equation, defined on the entire domain {Omega}.
We investigate numerically some Boussinesq type equations with square or cubic and saturated nonlinearity. We examine the propagation, interaction and overtake interaction of soliton solutions. Moreover, we examine the effect of the saturation term on the solution and compare it with the classical case of the square or cubic nonlinearity without saturation. We calculate numerically the phase shift experienced by the solitons upon collision and conclude the impact of saturation.
We show how one can calculate radiative capture cross sections and astrophysical S-factors for nuclei in the mass region A{<=}20 using potential models. We produce a sizeable list of cases for which the model works well. Useful quantities, such as spectroscopic factors and asymptotic normalization coefficients, are obtained and compared to published data.
In 1954 the possibility of forming a 'super-radiant' (SR) state in a gas of atoms confined to a volume of a size smaller than the wave length of radiation was suggested by Dicke. The atoms, with two levels, are coupled through their common radiation field. This indirect coupling leads to a redistribution of decay widths among unstable intrinsic states. A strongly decaying SR state is created at the expense of the rest of the states of the system. The connection of this mechanism to the notion of doorway states in low-energy nuclear reactions is discussed and applications to well known nuclear physics phenomena are presented.
In order to understand primordial and stellar nucleosynthesis, we have studied {sup 2}H(d,p){sup 3}H reaction at 0.4 MeV down to astrophysical energies. Knowledge of its S-factor is interesting also to plan reactions for fusion reactors to produce energy. The {sup 2}H(d,p)H reaction has been studied through the Trojan Horse Method applied to the three-body reaction {sup 2}H(He,pt)H, at beam energy of 17 MeV. Once selection of protons and tritons detected in coincidence and the selection of quasi-free events, the obtained S-factor is compared with direct measurements. Such data are in agreement with the direct ones and a pole invariance test has been obtained comparing the present results with another {sup 2}H(d,p){sup 3}H THM measurements, where a different spectator particle was employed.
In this review paper we summarize basic concepts of T-duality. Starting from the simplest case of abelian T-duality, we show the techniques used for finding the dual model and summarize developments in the field of Poisson-Lie T-duality/plurality, which deals with non-abelian groups. We also mention possible extension of T-duality to supermanifolds.
The paper gives an outlook of the stochastic approach to derivation of heat kernel short-time asymptotic expansion and to effective evaluation of corresponding coefficients.
The paper is devoted to the study of the formal differential expressions (-{Delta}){sup l}u+a{delta}u for arbitrary l(set-membership sign)N and the dimension of R{sup d} equal d = 2l. Approximations of the singular part by means of a family of rank-one operators are constructed and resolvent convergence of this family is investigated. It is demonstrated that the results are different from the case d{ne}2l.
With a time asymmetric theory, in which quantum mechanical time evolution is given by a semigroup of operators rather than by a group, the states of open systems are represented by density operators exhibiting a branching behavior. To treat the indistinguishably of the members of experimental ensembles, we hypothesize that environmental interference occurs during events that are themselves fundamentally indistinguishable.
In the context of the variational bi-complex, we re-explain that irreducible gauge systems define a particular example of a Lie algebroid. This is used to review some recent and not so recent results on gauge, global and asymptotic symmetries.
We present some results on the moduli space for the charge two-soliton solution of the non-commutative CP{sup 1} model. The associated Kaehler potential and its relation to the commutative case are discussed.
We present an alternative Hamiltonian description of a branelike universe immersed in a flat background spacetime. This model is named geodetic brane gravity. We set up the Regge-Teitelboim model to describe our Universe where such field theory is originally thought as a second order derivative theory. We refer to an Ostrogradski Hamiltonian formalism to prepare the system to its quantization. This approach comprize the manage of both first- and second-class constraints and the counting of degrees of freedom follows accordingly.
In this paper we study a gas of ultra light bosons as a candidate for dark matter in a higher dimensional framework. We briefly introduce the formalism of brane theory (BN) and and relevant aspects of ultra light bosonic dark matter (ULBDM) with the aim to combine both ideas in a single model. In this model, we assume two branes (visible and hidden brane) inside of the bulk and study the behavior of ULBDM in the hidden brane for an observer in the visible one. We reformulate the Friedmann equations for our Universe and the Friedmann equation concerning to the hidden brane. Thus, we can stablish the mutual interaction between the branes through the Hubble parameter, which measures the rate of expansion of our Universe. Finllay, we discuss that the hypothesis of ULBDM in the context of the braneworld theory is an interesting idea regarding the nature of dark matter.
A Hamiltonian formulation of the MHD plasma flow equations in terms of noncanonical variables is briefly discussed for the case of stationary axisymmetric configurations. This formulation makes it possible to cast these flow equations in a variational form with mixed (closed and/or open) boundary conditions. Within this framework the modelling of the acceleration channel of an applied-field Magneto-Plasma-Dynamic (MPD) thruster for space propulsion is discussed and shown to provide general relationships between the flow features and the thruster performance.
Both KdV theory and the standard pseudopotential theory require that solitons and double layers be explicitly super-acoustic, with the pseudopotential {psi}({phi},M) having a maximum at the origin. Recent studies of a variety of different three-component plasmas have shown that they may support finite amplitude solitons at the true acoustic speed of the plasma configuration, M{sub s}. These are associated with triple roots of the Sagdeev potential, and the usual soliton condition is replaced by {psi}''(0,M){<=}0. Sagdeev potentials for speeds marginally greater than M{sub s} then represent solitons of both polarities, one whose amplitude vanishes at M{sub s}(KdV-like), while the other is necessarily finite at M{sub s}('nonKdV-like'). Such coexistence regions have been observed to be linked to a critical plasma compositional parameter value for which {psi}'''(0,M{sub s}) = 0.
We present a class of three-dimensional solitary waves solutions of the Gross-Pitaevskii (GP) equation, which governs the dynamics of Bose-Einstein condensates (BECs). By imposing an external controlling potential, a desired time-dependent shape of the localized BEC excitation is obtained. The stability of some obtained localized solutions is checked by solving the time-dependent GP equation numerically with analytic solutions as initial conditions. The analytic solutions can be used to design external potentials to control the localized BECs in experiment.
Effects of the Landau diamagnetism and the Pauli paramagnetism on the longitudinal electric wave characteristics in a quantum plasma are studied. It is shown that a dispersion relation of the longitudinal wave propagating along a magnetic field strongly depends on the magnetic field, in radical contrast to the classical case. Instabilities of the quantized longitudinal electric waves are studied by a newly derived dispersion equation. Novel branches of longitudinal waves are found, which have no analogies without the Landau quantization. Growth rates of these new modes are obtained. The excitation of the zero sound by an electron beam is discussed and found that the quantization of the energy of electrons imposes a new condition. Furthermore, the excitation of Bogolyubov's type of spectrum by a strong electric field is considered.