The beryllium atom and beryllium positive ion in strong magnetic fields

The ground and a few excited states of the beryllium atom in external uniform magnetic fields are calculated by means of our 2D mesh Hartree-Fock method for field strengths ranging from zero up to 2.35*10^9T. With changing field strength the ground state of the Be atom undergoes three transitions involving four different electronic configurations which belong to three groups with different spin projections S_z=0,-1,-2. For weak fields the ground state configuration arises from the 1s^2 2s^2, S_z=0 configuration. With increasing field strength the ground state evolves into the two S_z=-1 configurations 1s^22s 2p_{-1} and 1s^2 2p_{-1}3d_{-2}, followed by the fully spin polarised S_z=-2 configuration 1s2p_{-1}3d_{-2}4f_{-3}. The latter configuration forms the ground state of the beryllium atom in the high field regime \gamma>4.567. The analogous calculations for the Be^+ ion provide the sequence of the three following ground state configurations: 1s^22s and 1s^22p_{-1} (S_z=-1/2) and 1s2p_{-1}3d_{-2} (S_z=-3/2).Comment: 15 pages, 7 figure

Decay Constants and Semileptonic Form Factors of Pseudoscalar Mesons

A relativistic constituent quark model is adopted to give an unified description of the leptonic and semileptonic decays of pseudoscalar mesons (\pi, K, D, D_s, B, B_s). The calculated leptonic decay constants and form factors are found to be in good agreement with available experimental data and the results of other approaches. Eventually, the model is found to reproduce the scaling behaviours of spin-flavor symmetry in the heavy-quark limit.Comment: 5 pages LaTeX; based on talk given at the "QFTHEP '99 Workshop", Moscow, May 27- June 2, 199

A model of gravitation with global U(1)-symmetry

It is shown that an embedding of the general relativity $4-$space into a flat $12-$space gives a model of gravitation with the global $U(1)-$symmetry and the discrete $D_{1}-$one. The last one may be transformed into the $SU(2)-$symmetry of the unified model, and the demand of independence of $U(1)-$ and $SU(2)-$transformations leads to the estimate $\sin^{2}\theta_{min}=0,20$ where $\theta_{min}$ is an analog of the Weinberg angle of the standard model.Comment: 7 page

Relativistic cross sections of mass stripping and tidal disruption of a star by a super-massive rotating black hole

[abbreviated] We consider the problem of tidal disruption of a star by a super-massive Kerr black hole. Using a numerically fast Lagrangian model of the tidally disrupted star we survey the parameter space of the problem and find the regions in the parameter space where the total disruption of the star or a partial mass loss take place as a result of fly-by around the black hole. Our treatment is based on General Relativity, and we consider the range of the black hole masses where the tidal disruption competes with the relativistic effect of direct capture of the star by the black hole. We find that our results can be represented on the plane of specific orbital angular momenta of the star $(j_{\theta}, j_{\phi})$. We calculate the contours of a given mass loss of the star on this plane, referred to as the tidal cross sections, for a given black hole mass $M$, rotational parameter $a$ and inclination of the trajectory of the star with respect to the black hole equatorial plane. It is shown that the tidal cross sections can be approximated as circles symmetric above the axis $j_{\phi}=0$, and shifted with respect to the origin of the coordinates in direction of negative $j_{\theta}$. The radii and shifts of these circles are obtained numerically for the black hole masses in the range $5\cdot 10^{5}M_{\odot}-10^{9}M_{\odot}$ and different values of $a$. It is shown that when $a=0$ the tidal disruption takes place for $M < 5\cdot 10^{7}M_{\odot}$ and when $a\approx 1$ the tidal disruption is possible for $M < 10^{9}M_{\odot}$.Comment: 11 pages, 16 figures, A&A in press, the text is clarified, the title and the abstract shown in text are change

Light Curve Solutions of Eclipsing Binaries in SMC

We propose a procedure for light-curve solution of eclipsing binary stars in the Small Magellanic Cloud for which photometric data have been obtained in the framework of the OGLE project as well as way of determination of the global stellar parameters on the basis of the obtained solutions, some empirical relations as well as the distance to the SMC. Several examples illustrate this procedure.Comment: 10 pages, 2 figures, accepte

The semileptonic form factors of B and D mesons in the Quark Confinement Model

The form factors of the weak currents, which appear in the semileptonic decays of the heavy pseudoscalar mesons, are calculated within the quark confinement model by taking into account, for the first time, the structure of heavy meson vertex and the finite quark mass contribution in the heavy quark propagators. The results are in quite good agreement with the experimental data.Comment: 12 pages LaTeX (elsart.sty) + 3 figure

Exchange and correlation energies of ground states of atoms and molecules in strong magnetic fields

Using a Hartree-Fock mesh method and a configuration interaction approach based on a generalized Gaussian basis set we investigate the behaviour of the exchange and correlation energies of small atoms and molecules, namely th e helium and lithium atom as well as the hydrogen molecule, in the presence of a magnetic field covering the regime B=0-100a.u. In general the importance of the exchange energy to the binding properties of at oms or molecules increases strongly with increasing field strength. This is due to the spin-flip transitions and in particular due to the contributions of the tightly bound hydrogenic state s which are involved in the corresponding ground states of different symmetries. In contrast to the exchange energy the correlation energy becomes less relevant with increasing field strength. This holds for the individual configurations constituting the ground state and for the crossovers of the global ground state.Comment: 4 Figures acc.f.publ.in Phys.Rev.

Correlations of the local density of states in quasi-one-dimensional wires

We report a calculation of the correlation function of the local density of states in a disordered quasi-one-dimensional wire in the unitary symmetry class at a small energy difference. Using an expression from the supersymmetric sigma-model, we obtain the full dependence of the two-point correlation function on the distance between the points. In the limit of zero energy difference, our calculation reproduces the statistics of a single localized wave function. At logarithmically large distances of the order of the Mott scale, we obtain a reentrant behavior similar to that in strictly one-dimensional chains.Comment: Published version. Minor technical and notational improvements. 16 pages, 1 figur