Non-Markovian dynamics of two non-coupled qubits interacting with two separate reservoirs with different spectral densities

The dynamics of two non-coupled qubits independently interacting with their reservoirs is solved by the time convolutionless projection operator method. We study two-qubit quantum correlation dynamics for two different types of spectral densities, which are a Lorentzian distribution and an Ohmic spectral density with a Lorentzian-Drude cutoff function. For two qubits initially prepared in the initial Bell state, quantum discord can keep longer time and reach larger values in nonMarkovian reservoirs for the first spectral distribution or by reducing the cutoff frequency for the second case. For the initial Bell-like state, the dynamic behaviors of quantum discord and entanglement are compared. The results show that a long time of quantum correlation can be obtained by adjusting some parameters in experiment and further confirm that the discord can capture quantum correlation in addition to entanglement.     

Dielectric constant of non-polar fluids

The theory of the static dielectric constant of non-polar fluids is re-examined using graph-theoretical techniques. A sample of arbitrary shape in an applied static electric field E ₀ is considered. The non-local tensor which transforms from E ₀ to the electrostatic polarization P is expressed as a sum of graphs. The relation appears simpler in terms of the inverse tensor, which is also obtained as a sum of graphs. Agreement with classical electrostatics is then manifest, and the shape-independence of the dielectric constant follows. An approximation suitable for numerical work is formulated, and a simplified version is solved analytically. The results are similar to those for fluids of rigid polar molecules in the Mean Spherical Model approximation. Reasons for both the similarities and the differences are given.     

Stability of gravity with a cosmological constant

The stability properties of Einstein theory with a cosmological constant Λ are investigated. For Λ > 0, stability is established for small fluctuations, about the de Sitter background, occurring inside the event horizon and semiclassical stability is analyzed. For Λ < 0, stability is demonstrated for all asymptotically anti-de Sitter metrics. The analysis is based on the general construction of conserved flux-integral expressions associated with the symmetries of a chosen background. The effects of an event horizon, which lead to Hawking radiation, are expressedfor general field hamiltonians. Stability for Λ < 0 is proved, using supergravity techniques, in terms of the graded anti-de Sitter algebra with spinorial charges also expressed as flux integrals.     

Dark energy interacting with two fluids

A cosmological model of dark energy interacting with dark matter and another general component of the universe is investigated. We found general constraints on these models imposing an accelerated expansion. The same is also studied in the case for holographic dark energy.     

两种非等温送风恒温恒湿机的实验研究

恒温恒湿机的用途之一是通过给机电设备机房降温,完成对电子设备的降温.去掉中间的降温媒介,直接对电子设备发热截面进行吹风降温,可以减掉机房照明和维护结构的发热量,从而节省电能.对于各部位发热量不同的设备发热截面,可以通过非等温送风型恒温恒湿机,实现从冷却设备到被冷却设备的点对点降温.对于两台发热量不同的电子设备,可以应用...     

Momentum spectra,anisotropic flow,and ideal fluids

If the matter produced in ultrarelativistic heavy-ion collisions reaches thermal equilibrium, its subsequent evolution follows the laws of ideal fluid dynamics. We show that general predictions can be made on this basis alone, irrespective of the details of the hydrodynamical model. We derive several scaling rules for momentum spectra and anisotropic flow (in particular the elliptic flow, v₂$v_2$, and the hexadecupole flow, v₄$v_4$) of identified particles. Comparison with existing data is briefly discussed, and qualitative predictions are made for LHC.     

Ranges of light ions in materials with different densities

The ranges of He, Li, Be, B, and C ions in gases and NIKFI-Ya2 nuclear photoemulsion are considered. The general features of the range variations as functions of the energy and ion nuclear charges are discussed. The results of calculations are compared with experimental data and the data of calculations using the SRIM-2013 program.     

Stability of constant nonabelian chromomagnetic fields

In this article we consider the problems of the stability of spherically symmetric and axially symmetric constant chromomagnetic fields given by translationally invariant potentials that satisfy the Yang-Mills equation with nonzero current, where variations of the current are equal to zero. For an unstable mode of wave nature, the nonlinear terms of the Lagrangian are taken into account. It is shown that in this connection, the perturbation imposed on the background field is finite in time. Consequently, nonlinearity of the system leads to stabilization of the system as a whole.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 14–16, December, 1987.     

Dielectric constant of polarizable,nonpolar fluids and suspensions

We study the dielectric constant of a polarizable, nonpolar fluid or suspension of spherical particles by use of a renormalized cluster expansion. The particles may have induced multipole moments of any order. We show that the Clausius-Mossotti formula results from a virtual overlap contribution. The corrections to the Clausius-Mossotti formula are expressed with the aid of a cluster expansion. The integrands of the cluster integrals are expressed in terms of two-body nodal connectors which incorporate all reflections between a pair of particles. We study the two- and three-body cluster integrals in some detail and show how these are related to the dielectric virial expansion and to the first term of the Kirkwood-Yvon expansion.     

Natural curvilinear coordinates for ideal MHD equations. Non-stationary flows with constant total pressure

Equations of magnetohydrodynamics (MHD) in the natural curvilinear system of coordinates where trajectories and magnetic lines play a role of coordinate curves are reduced to the non-linear vector wave equation coupled with the incompressibility condition in the form of the generalized Cauchy integral. The symmetry group of obtained equation, equivalence transformation, and group classification with respect to the constitutive equation are calculated. New exact solutions with functional arbitrariness describing non-stationary incompressible flows with constant total pressure are given by explicit formulae. The corresponding magnetic surfaces have the shape of deformed nested cylinders, tori, or knotted tubes.     

Finite-size scaling for near-critical continuum fluids at constant pressure

We consider the application of finite-size scaling methods to isothermal-isobaric (constant-NpT) simulations of pure continuum fluids. A finite-size scaling ansatz is made for the dependence of the relevant scaling operators on the particle number. To test the proposed scaling form, constant pressure simulations of the Lennard-Jones fluid at its liquid-vapour critical point are performed. The critical scaling operator distributions are obtained and their scaling with particle number is found to be consistent with the proposed behaviour. The forms of these scaling distributions are shown to be identical to their Ising model counterparts. The relative merits of employing the constant-NpT and grand canonical (constant-μVT) ensembles for simulations of fluid critically are also discussed.     

Stability of adhesion clusters under constant force

We solve the stochastic equations for a cluster of parallel bonds with shared constant loading, rebinding, and the completely dissociated state as an absorbing boundary. In the small force regime, cluster lifetime grows only logarithmically with bond number for weak rebinding, but exponentially for strong rebinding. Therefore rebinding is essential to ensure physiological lifetimes. The number of bonds decays exponentially with time for most cases, but in the intermediate force regime a small increase in loading can lead to much faster decay. This effect might be used by cell-matrix adhesions to induce signaling events through cytoskeletal loading.     

Nonlinear dynamics of the interface between continuous media with different densities

By reducing the hydrodynamic flow in the volume occupied by one or two fluids with different densities to the dynamics of the free surface or interface, equations describing their evolution are derived. These equations make it possible to study the essentially nonlinear stages of instability of free surfaces or interfaces in simple mathematical terms. It is shown that a perturbation of the free surface, however small, causes the formation and separation of a drop for a finite time. Accordingly, a perturbation, however small, of the interface between media with different densities results in the formation and subsequent separation of a large-scale vortex of the heavier fluid. Theoretical results agree qualitatively and quantitatively with experiments performed in [1, 2].