Detection of a Physical Difference between the CDM Halos in Simulation and in Nature

Numerical simulation is an important tool that is helpful for us to understand the process of structure formation in the universe. However, many simulation results of cold dark matter （CDM） halos on a small scale are inconsistent with observations： the central density profile is too cuspy and there are too many substructures, Here we point out that both the problems may be connected with a hitherto unrecognized bias in the simulated halos. Although CDM halos in nature and in simulation are both virialized systems of collisionless CDM particles, gravitational encounter cannot be neglected in the simulated halos because they contain many fewer particles. We demonstrate this by two numerical experiments, showing that there is a difference on the microcosmic scale between the natural and simulated halos. The simulated halo is more akin to globular clusters where gravitational encounter is known to lead to such drastic phenomena as core collapse. Such an artificial core collapse process appears to link the two problems together in the bottom-up scenario of structure formation in the ACDM universe. The discovery of this bias also has implications on the applicability of the Jeans theorem in galactic dynamics.     

Dynamics of Entropy and Nonclassicality Features of the Interaction between a ◇-type Four-Level Atom and a Single-Mode Field in the Presence of Intensity-Dependent Coupling and Kerr Nonlinearity

The interaction between a◇-type four-level atom and a single-mode field in the presence of Kerr medium with intensity-dependent coupling involving multi-photon processes has been studied. Using the generalized(nonlinear)Jaynes–Cummings model, the exact analytical solution of the wave function for the considered system under particular condition, has been obtained when the atom is initially excited to the topmost level and the field is in a coherent state. Some physical properties of the atom-field entangled state such as linear entropy showing the entanglement degree, Mandel parameter, mean photon number and normal squeezing of the resultant state have been calculated. The effects of Kerr medium, detuning and the intensity-dependent coupling on the temporal behavior of the latter mentioned nonclassical properties have been investigated. It is shown that by appropriately choosing the evolved parameters in the interaction process, each of the above nonclassicality features, which are of special interest in quantum optics as well as quantum information processing, can be revealed.     

Penrose’s circles in the CMB and a test of inflation

We present a calculation of the angular size of the circles in the CMB predicted by Penrose on the basis of his conformal cyclic cosmology. If these circles are detected, the existence of an upper limit on their angular radius would provide a challenge for inflation.     

Decay of a Bose-Einstein condensate in a dissipative lattice – the mean-field approximation and beyond

The dynamical evolution of a Bose-Einstein condensate in an open optical lattice is studied. Based on the Bose-Hubbard model we rederive the mean-field limit for the case of an environmental coupling including dissipation and phase-noise. Moreover, we include the next order correlation functions to investigate the dynamical behavior beyond mean field. We observe that particle loss can lead to surprising dynamics, as it can suppress decay and at the same time restore the coherence of the condensate. These behavior can be used to engineer the evolution, e.g. in the form of a stochastic resonance-like response, to inhibit tunneling or to create stable nonlinear structures of the condensate.     

Particle resonance in the Dirac equation in the presence of a delta interaction and a perturbative hyperbolic potential

We show that the energy spectrum of the one-dimensional Dirac equation, in the presence of an attractive vectorial delta potential, exhibits a resonant behavior when one includes an asymptotically spatially vanishing weak electric field associated with a hyperbolic tangent potential. We solve the Dirac equation in terms of Gauss hyper-geometric functions and show explicitly how the resonant behavior depends on the strength of the electric field evaluated at the support of the point interaction. We derive an approximate expression for the value of the resonances and compare the results calculated for the hyperbolic potential with those obtained for a linear perturbative potential. Finally, we characterize the resonances with the help of the phase shift and the Wigner delay time.     

Is there a spatial correlation in the distribution of adsorbed atoms in the cages of a zeolite?

Monte Carlo simulations of the cage-to-cage jumps of Xe atoms in a crystalline zeolite using the experimentally observed molecular rate constants for cage-to-cage jumps were carried out to determine if there is a systematic spatial correlation of the distributions of Xe atoms among the cages at equilibrium. The neighbours of cages having an Xe occupancy that is less than the average occupancy are found to have distributions that are skewed toward higher occupancy compared with the overall distribution. On the other hand, the neighbours of cages having an Xe occupancy that is greater than the average occupancy are found to have distributions that are skewed toward lower occupancy than the overall distribution.     

Quantum electrodynamics in a laser and the electron laser collisionQuantum electrodynamics in a laser and the electron laser collision

Quantum electrodynamics in a laser is formulated, in which the electron-laser interaction is exactly considered, while the interaction of an electron and a single photon is considered by perturbation. The formulation is applied to the electron- laser collisions. The effect of coherence between photons in the laser is therefore fully considered in these collisions. The possibility of y-ray laser generation by use of this kind of collision is discussed.     

Calculation of the Parameters of a One‐Coordinate Model of the VGaSAs and VGaSnGa Complexes in Gallium Arsenide

Experimental optical bands of the emitting complexes (a gallium vacancy with a donor at the nearest, from the vacancy, sublattice site) V_GaS_As and V_GaSn_Ga in GaAs are investigated in a wide temperature range. The parameters of a onecoordinate model of these centers are determined. A configurationcoordinate diagram of the V_GaS_As complex is constructed. Calculation of the field dependences of emission rates is carried out in terms of the parameters of the onecoordinate model of the V_GaS_As complex and the data obtained are compared with the results of experimental studies of the emission of electron holes from a deeplying center of the V_GaS_As complex.     

Specific features of the hybridization of Frenkel and Wannier–Mott excitons in a microcavity

Polariton states have been investigated in a microcavity, where the energy of the Frenkel exciton in an organic quantum well and the energy of the semiconductor Wannier–Mott exciton in an inorganic quantum well are close to the microcavity optical mode. It has been shown that the interaction of each of these excitons with the microcavity optical mode leads to their interaction with each other and to the formation of mutually coupled hybrid excitations. The influence of the location of the quantum wells in a microcavity on the spectra of hybrid states with different polarizations has been analyzed.     

Calculation of Energies of the Ground and Low Excited States of a Confined Helium Atom in a Spherical Parabolic Well

Making use of the adiabatic hyperspherical approach, we report a calculation for the energy spectrum of the ground and low-excited states of the confined helium atom in a spherical parabolic well. We find that the energies of a spherical parabolic well are in good agreement with those of an impenetrable spherical box for the larger confined potential radius. However, the energy values of a spherical parabolic well are much lower than those of an impenetrable spherical box for small values of re. We also find that the confinement may cause accidental degeneracies between levels with different low-excited states and the inversion of the energy values.     

Existence and Asymptotic Stability of Periodic Solutions of the Reaction–Diffusion Equations in the Case of a Rapid Reaction

A singularly perturbed periodic in time problem for a parabolic reaction-diffusion equation in a two-dimensional domain is studied. The case of existence of an internal transition layer under the conditions of balanced and unbalanced rapid reaction is considered. An asymptotic expansion of a solution is constructed. To justify the asymptotic expansion thus constructed, the asymptotic method of differential inequalities is used. The Lyapunov asymptotic stability of a periodic solution is investigated.     

Determination of the Efficiency and Energy Transfer Rate in the Fluorescence of a Single Donor–Acceptor Pair Attached to a Biomolecule

Resonance energy transfer from a single donor molecule to a single acceptor molecule (Förster resonance energy transfer) is currently used to determine the microscopic parameters describing interconformational changes in a protein molecule to which this single donor–acceptor pair is attached. A recently developed method makes it possible to intricately search for such parameters using a formula for the efficiency of Förster resonance energy transfer, which is the sum of several Gaussians. Another simpler method for the determination of the desired parameters of interconformational transitions has been proposed in this work on the basis of statistical processing of fluctuating tracks of fluorescence of a single donor–acceptor pair attached to a protein molecule.     

The dynamics of 180° domains in a ferroelectric in the process of polarization reversal and electron emission

A model is proposed to describe the evolution of 180° domains in a ferroelectric. Closed analytic expressions are obtained for the velocity of sideways motion of a 180° domain wall in an electric field and numerical calculations are performed. The connection between polarization reversal and electron emission is discussed.     

Low-energy relation for the trace of the energy–momentum tensor in QCD and the gluon condensate in a magnetic field

The nonperturbative QCD vacuum in a magnetic field has been studied. A low-energy relation for the trace of the energy–momentum tensor in the magnetic field has been obtained. It has been shown that the derivatives of the quark and gluon contributions to the trace of the energy–momentum tensor with respect to the magnetic field coincide with each other. The magnetic field dependence of the gluon condensate has been calculated in the limits of strong and weak fields.     

On the appearance of the λ-point in a weakly nonideal Bose gas and the two-liquid Thiess-Landau model

Ultrasecondly quantized operators are defined, studied, and used to obtain asymptotic properties of the spectrum of a superfluidity problem with boundary. Dedicated to the memory of Vladimir Borovikov     

Temporal Fluctuations of Radiation of π and σ Components of a Mercury Capillary Lamp in the Presence of the Transverse Zeeman Effect

Russian Physics Journal - Temporal fluctuations of the intensity of radiation of the π component and of the sum of the σ+ and σ components of capillary low-pressure lamps filled with...     

Comparison of the ratios of the yields of cumulative K + and K − mesons with the predictions of the model of a collective sea of quark-antiquark pairs in nuclei

The results obtained by simulating, within the flucton model, the production and secondary interactions of cumulative K ⁺ and K ^? mesons in nuclei indicate that the ratios of their yields are in acceptable agreement with the predictions of the model of a collective sea of quark-antiquark pairs in nuclei. The calculations were performed with allowance for the kaon-hadronization length according to the model of bremsstrahlung-gluon emission and the parton model.