Effect of Doppler broadening on gain in an open V-type inversionless lasing system

Our study shows that for the copropagating probing and driving fields, the gain without inversion doesn't monotonously decrease or increase with the increasement of Doppler width. When the driving field is resonant, at a suitable Doppler width, we can get a maximum value of the gain without inversion, which is much larger than that obtained when Doppler broadening is absent.     

How to reach the orbital configuration of the inner three planets in HD 40307 planet system?

The formation of the present configuration of three hot super-Earths in the planet system HD 40307 is a challenge to dynamical astronomers.With the two successive period ratios both near and slightly larger than 2,the system may have evolved from pairwise2:1 mean motion resonances(MMRs).In this paper,we investigate the evolutions of the period ratios of the three planets after the primordial gas disk was depleted.Three routines are found to probably result in the current configuration under tidal dissipation with the center star,they are:(i)through apsidal alignment only;(ii)out of pairwise 2:1 MMRs,then through apsidal alignment;(iii)out of the 4:2:1 Laplace Resonance(LR),then through apsidal alignment.All the three scenarios require the initial eccentricities of planets～0.15,which implies a planetary scattering history during and after the gas disk was depleted.All the three routines will go through the apsidal alignment phase,and enter a state with near-zero eccentricities finally.We also find some special characteristics for each routine.If the system went through pairwise 2:1 MMRs at the beginning,the MMR of the outer two planets would be broken first to reach the current state.As for routine(iii),the planets would be out of the LR at the place where some high-order resonances are located.At the high-order resonances 17:8 or 32:15 of the planets c and d,the system will possibly enter the current state as the final equilibrium.     

Can a strong magnetic background modify the nature of the chiral transition in QCD?

The presence of a strong magnetic background can modify the nature and the dynamics of the chiral phase transition at finite temperature: for high enough magnetic fields, comparable to the ones expected to be created in noncentral high-energy heavy ion collisions at RHIC and the LHC, the original crossover is turned into a first-order transition. We illustrate this effect within the linear sigma model with quarks to one loop in the scheme for N_f=2.     

Frequency–time correlation of inhomogeneous broadening in a three-level system and the stimulated photon echo locking effect

The frequency–time correlation of inhomogeneous broadening on different transitions in a threelevel resonant medium in the presence of external spatially nonuniform electric fields is considered. It is shown that, under a certain relationship between the magnitudes of gradients of external nonuniform electric fields acting at different moments of time, it is possible to control the magnitude of the frequency–time correlation on different frequency transitions. An increase in the frequency–time correlation coefficient with certain strengths of external spatially nonuniform electric fields leads to the recovery of the phase memory of the system and an increase in the stimulated photon echo intensity.     

Effects of phase fluctuation in an open four-level inversionless lasing system

A steady analytical solution of an open four-level inversionless lasing system with a driving field having the phase fluctuation has been given, and the effects of the finite width due to the phase fluctuation on the gain, dispersion, and population difference have been analyzed by using the numerical simulation from the steady analytical solution. It is found that: with the linewidth increasing, the gain decreases and the absolute value of population difference between levels coupled by the probe field increases, but the variation of the linewidth cannot change the properties of the inversionless lasing and refractive index increase of the system; when the linewidth does not equal to zero, the system can still get a high refractive index with zero absorption, and these conclusions have very obvious difference from those obtained in other inversionless lasing systems.     

How should complexity scale with system size?

We study how statistical complexity depends on the system size and how the complexity of the whole system relates to the complexity of its subsystems. We study this size dependence for two well-known complexity measures, the excess entropy of Grassberger and the neural complexity introduced by Tononi, Sporns and Edelman. We compare these results to properties of complexity measures that one might wish to impose when seeking an axiomatic characterization. It turns out that those two measures do not satisfy all those requirements, but a renormalized version of the TSE-complexity behaves reasonably well.     

Squeezing in a three-level Jaynes-Cummings model with strong field

Squeezing in three-level Jaynes-Cummings model with the strong initial coherent state is studied numerically. The dependence of the squeezing on the field intensity and time is analysed. The cases that the light field is initially in a Fock state and in a squeezed vacuum state are also discussed.     

How to Define the Equality of Durations in Measurement of Time

We develop the research on measurement of time worked by Poincarh, Einstein, Landau and other researchers. Based on the convention that the velocity of light is isotropic and is a constant in empty spacetime, we not only answer the question about the definition of the synchronization of rate of clocks located at different places, but also find the solution to the issue of how to define the equality of two durations in measurement of time.     

Implications of the Marangoni effect on the onset of Rayleigh–Benard convection in a two-layer system with a deformable interface

The European Physical Journal Special Topics - The paper deals with the investigation of the implications of the Marangoni effect on the onset of Rayleigh-Benard convection in a two-layer system...     

Optimization of the cell in the ion–optical system of a powerful source of protons with energy 15 keV

We have described the results of numerical investigations of different versions of a three-electrode elementary slit cell for the formation a hydrogen ion beam with a relatively low energy and a high emission current density. The version of the cell chosen from the results of these investigations makes it possible to obtain a hydrogen atom beam with an energy of 15 keV, an ion current density of ~500 mA/cm², and an angular divergence of 24 mrad.     

Study of the SF 6 − ion lifetime in a rf quadrupole trap

We use an experimental apparatus to study SF ₆ ^– ions lifetimes. These ions are created inside a quadrupole rf trap by charge exchange between highly excited argon atoms and SF₆ molecules. Ions are observed from 200 s up to 15 ms after their creation time. In order to explain experimental results, collisions with SF₆ molecules and the influence of ionized core of argon are taken into account. A part of SF ₆ ^– ions are stabilized by the last influence. These results evidence a radiative stabilization phenomenon, the lifetime of which is estimated at about 5 ms.Equipe de Recherche associée au C.N.R.S. 0898Laboratoire associé au C.N.R.S. 0282     

Quantum entanglement in the system of two two-level atoms interacting with a single-mode vacuum field

The entanglement properties of the system of two two-level atoms interacting with a single-mode vacuum field are explored. The quantum entanglement between two two-level atoms and a single-mode vacuum field is investigated by using the quantum reduced entropy; the quantum entanglement between two two-level atoms, and that between a single two-level atom and a single-mode vacuum field are studied in terms of the quantum relative entropy. The influences of the atomic dipole--dipole interaction on the quantum entanglement of the system are also discussed. Our results show that three entangled states of two atoms--field, atom--atom, and atom--field can be prepared via two two-level atoms interacting with a single-mode vacuum field.     

How to reach a few percent level in determining the Lense–Thirring effect?

In this paper we explore the possibility of suitably combining the nodes of the existing geodetic LAGEOS, LAGEOS II and Ajisai laser-ranged satellites and of the radar altimeter Jason–1 satellite in order to increase the accuracy in testing the general relativistic gravitomagnetic Lense–Thirring secular effect in the gravitational field of the Earth. The proposal of introducing Ajisai and Jason–1 in such a combination comes from the expected benefits which could be obtained in reducing the aliasing secular impact of the classical part of the terrestrial gravitational field. According to the recently released EIGEN-CG01C combined GRACE + CHAMP + terrestrial gravimetry/altimetry Earth gravity model, the impact of the static part of the mismodelled even zonal harmonics of geopotential, which represent the major source of systematic error, amounts to 1.6%, at 1– level. It is better than the error which could be obtained with a two-node LAGEOS-LAGEOS II only combination (6% at 1–). Moreover, the proposed combination would be insensitive also to the secular variations of the low-degree even zonal harmonics, contrary to the LAGEOS-LAGEOS II only combination. Such variations could be a serious limiting factor over observational time spans many years long. The price to be paid for this improvements of the systematic error of gravitational origin is represented by the non-conservative forces introduced along with the new orbital elements. However, they would induce periodic perturbations, contrary to the gravitational noise. A major concern would be the assessment of the impact of the non-conservative accelerations on the Jason–1 node. According to the present-day force models, the mismodelling in the non-conservative forces would, at worst, induce an aliasing periodic signal with an amplitude of 4% of the Lense-Thirring effect over a time span of 2 years. However, an observational time span of just some years could safely be adopted in order to fit and remove the residual long–period non-gravitational signals affecting Jasons node, which, in the case of the direct solar radiation pressure, have a main periodicity of approximately 120 days. Of course, the possibility of getting time series of the Jasons node some years long should be demonstrated in reality.     

Is it possible to infer the equation of state of a mixture of hard discs from that of the one-component system?

(Molec. Phys., 1999, 96, 1185–1188)     

Atomic coherent trapping and phase property of the field in the system of two-level atoms interacting with a single-mode field

In this paper,the condition of the atomic coherent trapping in the system of twotwo-level atoms interacting with a single-mode coherent field has been obtained.And proper-ties of the light field in this case has also been analysed by means of the phase theory intro-duced by Barnett and Pegg,     

Is it possible to infer the equation of state of a mixture of hard discs from that of the one-component system?

Based on exact asymptotic properties of the composition-independent virial coefficients of a binary mixture of hard discs in the limits α = σ₂/σ₁ → 0, α → 1 and α → ∞, R. J. Wheatley (1998, Molec. Phys., 93, 965) has recently proposed an approximate interpolation equation for these coefficients. In this note, the equation of state equivalent to this interpolation is obtained, expressing the compressibility factor of the mixture in terms of that of the pure system. An extension to an arbitrary number of components is also given. The equation of state derived here is compared with another one recently proposed by following a different route (Santos, A., Yuste, S. B., and López de Haro, M., 1999, Molec. Phys., 96, 1) and with Monte Carlo simulation results. It is shown that the latter equation is more accurate than the former one, at least for not too disparate mixtures (0.7 < α < 1).