Correlator of Topological Charge Densities in Instanton Model in QCD

The QCD sum rule for the correlator of topological charge densities and related to it longitudinal part of the correlator of singlet axial currents is considered in the framework of instanton model. The coupling constant of eta'-meson with the singlet axial current is determined. Its value appears to be in a good coincidence with the value determined recently from the connection of the part of proton spin, carried by u,d,s quarks, with the derivative of QCD topological susceptibility. From the same sum rule eta-eta' mixing angle is found in the framework of two mixing angles model. Its value is close to that found in the chiral effective theory. The correlator of topological charge densities at large momenta is calculated.Comment: 14 pages, 2 figure

Convergence of economic growth in Russian megacities

Purpose: The article presents the results of an empirical analysis of the economic growth of Russian cities with a population of over 1 million people (megacities). Design/Methodology/Approach: The analyzed indicator is the city product calculated according to the UN methodology for the period from 2010 to 2016. The paper analyses the process of β- and σ-convergence across Russian megacities using methods of spatial econometrics in addition to the traditional β-convergence techniques from the neoclassical theoretical framework. Findings: The dynamics of the coefficient of variation confirmed the presence of σ-convergence in city product. Empirically, positive spatial autocorrelation has been confirmed. Beta-convergence for Russian megacities is found to be significant and the spatial location of megacities significantly affects β-convergence. Control factors such as fixed capital investment per capita in 2010, average retail volume per capita in 2010, average annual number of employees of enterprises and organizations in 2010 and the dummy variable introduced for “federal cities” Moscow and St. Petersburg are all found to have positive and statistically significant impact on economic growth. Practical Implications: Policymakers may take the results into account under the planning of economical strategies for megacities and regions in Russia in order to facilitate the regional economic growth and the speed of convergence. Originality/Value: The main contribution of the study is the consideration of the economical growth for the megacities and not for the regions as it often used to be the case in similar studies. The important finding is that megacities‘ economies do converge and the influence of control factors is pronounced.peer-reviewe

Spectral Line Broadening and Angular Blurring due to Spacetime Geometry Fluctuations

We treat two possible phenomenological effects of quantum fluctuations of spacetime geometry: spectral line broadening and angular blurring of the image of a distance source. A geometrical construction will be used to express both effects in terms of the Riemann tensor correlation function. We apply the resulting expressions to study some explicit examples in which the fluctuations arise from a bath of gravitons in either a squeezed state or a thermal state. In the case of a squeezed state, one has two limits of interest: a coherent state which exhibits classical time variation but no fluctuations, and a squeezed vacuum state, in which the fluctuations are maximized.Comment: 21 pages, 2 figures. Dedicated to Raphael Sorkin on the occasion of his 60th birthday. (v2: several references added and some minor errors corrected

Correlations in a two-dimensional Bose gas with long range interactions

We study the correlations of two-dimensional dipolar excitons in coupled quantum wells with a dipole -- dipole repulsive interaction. We show that at low concentrations, the Bose degeneracy of the excitons is accompanied by strong multi-particle correlations and the system behaves as a Bose liquid. At high concentration the particles interaction suppresses quantum coherence and the system behaves similar to a classical liquid down to a temperature lower than typical for a Bose gas. We evaluate the interaction energy per particle and the resulting blue shift of the exciton luminescence that is a direct tool to measure the correlations. This theory can apply to other systems of bosons with extended interaction.Comment: 11 pages including 2 figure

Phase diagram of the antiferromagnetic XY model in two dimensions in a magnetic field

The phase diagram of the quasi-two-dimensional easy-plane antiferromagnetic model, with a magnetic field applied in the easy plane, is studied using the self-consistent harmonic approximation. We found a linear dependence of the transition temperature as a function of the field for large values of the field. Our results are in agreement with experimental data for the spin-1 honeycomb compound BaNi_2V_2O_3Comment: 3 page

Coherent and incoherent pumping of electrons in double quantum dots

We propose a new mode of operation of an electron pump consisting of two weakly coupled quantum dots connected to reservoirs. An electron can be transferred within the device at zero bias voltage when it is subjected to electromagnetic radiation, thereby exciting the double dot. The excited state can decay by transferring charge from one lead and to the other lead in one direction. Depending on the energies of the intermediate states in the pumping cycle, which are controlled by the gate voltages, this transport is either incoherent via well-known sequential tunneling processes, or coherent via a inelastic co-tunneling process. The latter novel mode of operation is possible only when interdot Coulomb charging is important. The D.C. transport through the system can be controlled by the frequency of the applied radiation. We concentrate on the resonant case, when the frequency matches the energy difference for exciting an electron from one dot into the other. The resonant peaks in the pumping current should be experimentally observable. We have developed a density matrix approach which describes the dynamics of the system on timescales much larger than the period of the applied irradiation. In contrast to previous works we additionally consider the case of slow modulation of the irradiation amplitude. Harmonic modulation produces additional sidepeaks in the photoresponse, and pulsed modulation can be used to resolve the Rabi frequency in the time-averaged current.Comment: 5 pages, 6 figures. This is an extension of cond-mat/9707310 "A coherent double-quantum-dot electron pump" This version has been accepted for publication in Phys. Rev. B. Changes: Added references. Corrected typos. Changed content mainly the introduction. Regime of device operation is now specified more precisely. A stability diagram has been added as a figure has been adde

Videoconferencing via satellite. Opening Congress to the people: Technical report

The feasibility of using satellite videoconferencing as a mechanism for informed dialogue between Congressmen and constituents to strengthen the legislative process was evaluated. Satellite videoconferencing was defined as a two-way interactive television with the TV signals transmitted by satellite. With videoconferencing, one or more Congressmen in Washington, D. C. can see, hear and talk with groups of citizens at distant locations around the country. Simultaneously, the citizens can see, hear and talk with the Congressmen

Semiclassical quantization of SU(3) skyrmions

Semiclassical quantization of the SU(3)-skyrmions is performed by means of the collective coordinate method. The quantization condition known for the SU(2)-solitons quantized with SU(3) collective coordinates is generalized for the SU(3) skyrmions with strangeness content different from zero. Quantization of the dipole-type configuration with large strangeness content found recently is considered as an example, the spectrum and the mass splitting of the quantized states are estimated. The energy and baryon number density of SU(3) skyrmions are presented in the form emphasizing their symmetry in different SU(2) subgroups of SU(3), and the lower boundary for the static energy of SU(3) skyrmions is derived.Comment: 16 pages, 2 figures (available upon request). Submitted to JETP on May 6, 1997; in print. A preliminary short version of this paper is hep-th/960916

Rapidly Rotating Fermi Gases

We show that the density profile of a Fermi gas in rapidly rotating potential will develop prominent features reflecting the underlying Landau level like energy spectrum. Depending on the aspect ratio of the trap, these features can be a sequence of ellipsoidal volumes or a sequence of quantized steps.Comment: 4 pages, 1 postscript fil

Wave Function Structure in Two-Body Random Matrix Ensembles

We study the structure of eigenstates in two-body interaction random matrix ensembles and find significant deviations from random matrix theory expectations. The deviations are most prominent in the tails of the spectral density and indicate localization of the eigenstates in Fock space. Using ideas related to scar theory we derive an analytical formula that relates fluctuations in wave function intensities to fluctuations of the two-body interaction matrix elements. Numerical results for many-body fermion systems agree well with the theoretical predictions.Comment: 4 pages, 2 figure