Microscopic calculation of the surface absorption in the optical potential

We calculated the contributions of the two-particle one-hole (2p-1h) and the one-particle two-hole (1p-1h) excitations to the imaginary partW(E, R) of then-⁴⁰Ca optical potential. The bound single particle states and energies of the⁴⁰Ca nucleus are calculated quantum mechanically by solving the Schrödinger equation with a Woods-Saxon potential. For the excited states in the continuum we use the Thomas-Fermi approximation. Different forms of contact residual interactions have been tested. A combination of aδ-force and a smeared SDI can fit the phenomenologicalW(E, R).     

The shell model and collective structures in54,55,56Fe

Extensive shell-model calculations have been performed on^54,55,56Fe. The results obtained in a model space with two and with up to threef _7/2 holes in the,⁵⁶Ni core are compared with experiment. The Surface Delta Interaction (SDI) and the Kuo Brown interaction (KB) have been used to calculate energy levels, spectroscopic factors and electromagnetic properties resulting especially for⁵⁶Fe in a remarkably good agreement with experiment. Admixtures of three-hole components in the wave functions are significant and increase with mass number. Properties of high-spin states withJ≦15 are discussed. Pronounced collective features derived microscopically are expected in⁵⁶Fe. Finally some suggestions for interesting experiments are given.     

The FBCS model and the inverse gap equations applied to the tin isotopes

The FBCS model for odd nuclei and the inverse gap equations are applied to a whole sequence of tin isotopes,viz.^111–125Sn. From spectroscopic data on the odd isotopes, the single-particle energies and interaction strengths are obtained. With these parameters the lowest states of the even isotopes are calculated by a number-projected two-quasiparticle diagonalization and by the usual BCS one. This is done with two Gaussian interactions and the SDI. In the case of the Gaussian forces the experimental energies are well reproduced by the number-projected treatment. Effective charges for Eλ transitions, which are required to reproduce the experimental transition rates, are rather constant for the whole series of isotopes, in case of the number-projected treatment. In addition a number of spectroscopic factors for one-nucleon transfer reactions are calculated and good agreement with experiments is observed.     

Ionization of lithium in a strong laser field

In this work, we present ab initio computations of the interaction of helium and lithium with a strong laser field. By computing the two-and three-particle wave functions, we retain the full electron correlation and numerically integrate the time-dependent Schrödinger equation (TDSE) restricted to one dimension. The correlated nonsequential double ionization (NSDI) and the sequential double ionization (SDI) is studied. Our results show a clear transition from NSDI to SDI for increasing intensities. The correlated double ionization is found to be sensitive to the spin configuration of the ionized pair. Our model allows us to “measure” two different channels of double ionization (one with both spins aligned and one with spins antialigned).     

A comment on the common one-dimensional derivation of the van der Waals forces

In many physical text-books a simple one-dimensional model is used to derive the characteristic 1/R ⁷-dependence of the attractive van der Waals forces. We show that this calculation is wrong. The long range forces in this simple model are not attractive but repulsive proportional to 1/R ⁶. Only a three-dimensional calculation yields the correct behavior.     

On the Global Regularity of a Helical-Decimated Version of the 3D Navier-Stokes Equations

We study the global regularity, for all time and all initial data in H ^1/2, of a recently introduced decimated version of the incompressible 3D Navier-Stokes (dNS) equations. The model is based on a projection of the dynamical evolution of Navier-Stokes (NS) equations into the subspace where helicity (the L ²-scalar product of velocity and vorticity) is sign-definite. The presence of a second (beside energy) sign-definite inviscid conserved quadratic quantity, which is equivalent to the H ^1/2-Sobolev norm, allows us to demonstrate global existence and uniqueness, of space-periodic solutions, together with continuity with respect to the initial conditions, for this decimated 3D model. This is achieved thanks to the establishment of two new estimates, for this 3D model, which show that the H ^1/2 and the time average of the square of the H ^3/2 norms of the velocity field remain finite. Such two additional bounds are known, in the spirit of the work of H. Fujita and T. Kato (Arch. Ration. Mech. Anal. 16:269–315, 1964; Rend. Semin. Mat. Univ. Padova 32:243–260, 1962), to be sufficient for showing well-posedness for the 3D NS equations. Furthermore, they are directly linked to the helicity evolution for the dNS model, and therefore with a clear physical meaning and consequences.     

Chiral symmetry,the 1/N expansion and the SU(N) thirring model

In the two-dimensional SU(N) Thirring model, the 1/N expansion seems to predict spontaneous breaking of the continuous chiral symmetry. This is impossible in two-dimensions. Reasoning along the lines of Berezinski, Kosterlitz and Thouless for the two-dimensional XY model, we argue that, in fact, rather than showing long-range order, $\text{〈}\text{ψ}\text{ψ(x)}\text{ψ}\text{ψ(0)〉}$ vanishes in this model as |x|^?1/N at large |x|. The 1/N expansion is, in fact, a rather good guide to the properties of this model.     

Calculations of the energy spectra of Zn,Ga, and Ge isotopes by the shell model

The effective Hamiltonian which was determined empirically by Koops and Glaudemans is tested in shell model calculations for the^65–68Zn,^67–69Ga, and^68–70Ge nuclei in the full (1p _3/2,0f _5/2,1p _1/2) ⁿ space. The resulting energy spectra are compared with the experimental spectra and results of previous calculations. The overall agreement with experiment is as satisfactory for these nuclei as for the Ni and Cu isotopes, by which the Hamiltonian was determined. It is noticed that the spectra of⁶⁷Zn and^67,69Ga calculated in this work are similar to those provided by the Alaga model.     

On the Q 2 dependence of nuclear structure functions

The recent high statistics NMC data on the Tin to Carbon structure function ratio seems to indicate, for the first time, a significant Q ² dependence, especially at small values of Bjorken x, x < 0.05, and Q ² > 1 GeV². A purely log(Q ²)-type dependence of the structure functions, which is consistent with the free nucleon data, yields a fairly flat ratio with little or no Q ² dependence. In view of this seeming contradiction, we re-examine the applicability of such a model to nuclear structure functions in such a kinematical regime. We find that the model is consistent with all data, within experimental errors, without any need for introducing additional Q ² dependences or higher twist contributions. The model correctly reproduces the Q ² dependence of the Carbon structure function as well. We also critically examine the Q ² dependence of the corresponding spin dependent structure functions.     

Energy levels and probabilities of radiative transitions in the Kr IX ion

The energy levels of the 3d ⁹4l (l = 1–3) and 3p ⁵3d ¹⁰4l (l = 0, 1) configurations in the Kr IX ion and the probabilities of radiative transitions to the ground state from these excited states have been calculated within the relativistic perturbation theory using a zero-approximation model potential. The results are shown to be stable within this approximation. The well-known problem of anomalously low accuracy of the calculations of some higher lying singlet levels is considered.     

A Semi-empirical tight-binding theory of the electronic structure of semiconductors2

A nearest-neighbor semi-empirical tight-binding theory of energy bands in zincblende and diamond structure materials is developed and applied to the following sp³-bonded semiconductors: C, Si, Ge, Sn, SiC, GaP, GaAs, GaSb, InP, InAs, InSb, AlP, AlAs, AlSb, ZnSe, and ZnTe. For each of these materials the theory uses only thirteen parameters to reproduce the major features of conduction and valence bands. The matrix elements exhibit chemical trends: the differences in diagonal matrix elements are proportional to differences in free-atom orbital energies and the off-diagonal matrix elements obey the d^?2 rule of Harrison et al. The lowest energy conduction bands are well described as a result of the introduction of an excited s state, s¹. on each atom. Examination of the chemical trends in this sp³s¹ model yields a crude but “universal” sp³s¹ model whose parameters do not depend explicitly on band gaps, but rather are functions of atomic energies and bond lengths alone. The “universal” model, although cruder than the sp³s¹ model for any single semiconductor, can be employed to study relationships between the band structures of different semiconductors; we use it to predict band edge discontinuities of heterojunctions.     

A New Unified Dark Fluid Model and Its Cosmic Constraint

In this paper, we propose a new unified dark fluid (UDF) model with equation of state (EoS) w(a)=?α/(β a ^?n +1), which includes the generalized Chaplygin gas model (gGg) as its special case, where α, β and n are three positive numbers. It is clear that this model reduces to the gCg model with EoS w(a)=?B _s /(B _s +(1?B _s )a ^?3(1+α)), when α=1, β=(1?B _s )/B _s and n=3(1+α). By combination the cold dark matter and the cosmological constant, one can coin a EoS of unified dark fluid in the form of w(a)=?1/(1+(1?Ω_Λ)a ^?3/Ω_Λ). With this observations, our proposed EoS provides a possible deviation from ΛCDM model when the model parameters α and n deviate from 1 and 3 respectively. By using the currently available cosmic observations from type Ia supernovae (SN Ia) Union2.1, baryon acoustic oscillation (BAO) and cosmic microwave background radiation (CMB), we test the viability of this model and detect the possible devotion from the ΛCDM model. The results show that the new UDF model fits the cosmic observation as well as that of the ΛCDM model and no deviation is found from the ΛCDM model in 3σ confidence level. However, our new UDF model can give a non-zero sound speed, as a contrast, which is zero for the ΛCDM model. We expect the large structure formation information can distinct the new UDF model from the ΛCDM model.     

Angular distributions of photoneutrons from the 207, 208Pb(γ, n0) reactions

Angular distributions of photoneutrons from the ^{207, 208}Pb(γ, n₀) reactions were measured at 11 angles around θ = 90°. The γ-source, E_γ = 7–11.4 MeV, contained discrete lines (ΔE ? 30 eV) obtained from n-capture and was used in conjunction with a high-resolution ³He spectrometer. Strong evidence for an E2 contribution and for E2-E1 and possibly E1-M1 interference was obtained in both ²⁰⁷Pb and ²⁰⁸Pb. The results are compared with calculations using a direct-semidirect model which involved an E1 and isoscalar E2 giant resonances. The results indicate that this model could explain only certain features of the data while most of the other features remain unexplained.     

Comments on the calculation of the extended state electron mobility in amorphous silicon

In a recent paper Silver and his collaborators concluded that the extended state electron mobility micro_c in amorphous silicon was about 500 cm²V^-1s^-1. The calculations leading to this value were based on the multi-trapping transport model, the experimental drift mobility value of μ_e = 1 cm²V^-1s^-1, the tail state distribution suggested by field effect data and an assumed thermalisation depth of the electrons of 0.29eV. In the following it will be shown from experimental results that the above thermalisation depth is fundamentally inconsistent with the observations and, when used with the measured micro_e, leads to unrealistically high calculated micro_c -values. We also show that with a thermalisation depth appropriate to the conditions under which micro_e is determined, the experimental results and the computed micro_c-values (10 - 20 cm²V^-1s^-1) form a consistent picture.     

Causality in 1+1-dimensional Yukawa model-II

The limits g → large, M → large with (g ³/M) ?=? const. of the 1+1-dimensional Yukawa model are discussed. The conclusion of the results on bound states of the Yukawa model in this limit (obtained in arXiv:0908.4510v3 [hep-th]) is taken into account. It is found that model reduces to an effective non-local ? ³ theory in this limit. Causality violation also is observed in this limit.     

Damping of the giant spin-flip dipole and spin-flip quadrupole charge exchange modes in 90Zr

The damping of the giant spin-flip dipole (L=1, S=1, T=1, J^π=0⁻, 1⁻, 2⁻) and spin-flip quadrupole (L=2, S=1, T=1, J^π=1⁺, 2⁺, 3⁺) charge exchange resonances in ⁹⁰Zr is calculated in a microscopic nuclear structure model which includes both one-particle-one-hole (1p1h) and two-particle-two-hole (2p2h) configurations in a systematic way. It is shown that the coupling to 2p2h configurations gives rise to a strongly energy dependent spreading width which shifts a large fraction of transition strength to high excitation energies. The implications for the analysis of intermediate energy ⁹⁰Zr(p,n) data is discussed.     

Phase transitions and the high temperature expansion for the reggeon calculus

We study a recently proposed lattice version of the reggeon field theory. First a simple one-dimensional system possessing many of the features of the reggeon calculus (Ising model in an imaginary magnetic field) is solved. Surprisingly, the system is found to undergo a phase transition at a non-zero critical temperature, which, although of first order obeys the universality and scaling laws previously postulated for the reggeon calculus. Returning to the full lattice theory, the machinery for performing a high temperature expansion is set up, and initial calculations carried out to order T^?3. In this order, best estimates for the critical indices η and v in the asymptotic elastic amplitude A(s,t) ～ is (ln s)^ηf(t(lns)^v) yield $\text{η = 0 (}\text{1}\text{2}\text{～ 1), v = 0(1}\text{1}\text{2}\text{～ 2)}$. Check on the method, including comparisons with known Ising model results, are also discussed.     

Unitarity bounds in the vector condensate model of electroweak interactions

We replace the standard model scalar doublet by a doublet of vector fields and generate masses by dynamical symmetry breaking. Oblique radiative corrections are small if the new vector bosons (B ⁺,B ⁰) are heavy. In this note it is shown that the model has a low momentum scale and above Λ?2 TeV it does not respect the perturbative unitarity. From tree-graph unitarity the allowed region ofB ⁺ (B ⁰) mass is estimated asm _B ⁺≥333 GeV (m _B ⁰≥373 GeV) at Λ=1 TeV.