Structure of light hypernuclei

The structure of light hypernuclei with strangeness S=−1 and −2 is investigated with the microscopic cluster model and the Gaussian expansion method (GEM). We emphasize that the cluster picture as well as the mean-field picture is invaluable to understand the structure of Λ hypernuclei, Σ hypernuclei and double Λ hypernuclei. A variety of aspects of Λ hypernuclei is demonstrated through a systematic study of p-shell hypernuclei (,, , , , , ) and sd-shell ones (, ): for example, the appearance of genuine hypernuclear states with new spatial symmetry which cannot be seen in ordinary nuclei, the glue-like role of the Λ particle which shrinks the size of nuclear core and thus reduces the B(E2) value, and the halo and skin structures in and etc. The typical light hypernucleus is thoroughly investigated, including its production, structure and decay. Precise three-body and four-body calculations of , and using GEM provide important information on the spin structure of the underlying ΛN interaction, by comparing with recent experimental data from γ-ray hypernuclear spectroscopy. The Λ–Σ coupling effect is studied in and . The binding mechanism of is discussed together with the possible existence of , emphasizing the fact that the study of is useful for extracting information on the ΣN interaction differing from that from . A systematic study of double-Λ hypernuclei, constrained by the NAGARA data () within a four-body cluster model indicates that the recently observed Demachi–Yanagi event can be interpreted as the 2⁺ state of . The effect of hyperon mixing in and is investigated using one-boson-exchange potentials and quark-cluster-model interactions for the S=−2 sector. A close relation between nuclear deep hole states and hypernuclei is discussed, emphasizing the selection rule for fragmentation of the s-hole in light nuclei, which is promising for understanding the production mechanism of double-Λ and twin-Λ hypernuclei via Ξ-atomic capture.     

Existence of different intermediate Hamiltonians in type A -fold supersymmetry

Type A -fold supercharge admits a one-parameter family of factorizations into product of first-order linear differential operators due to an underlying symmetry. As a consequence, a type A -fold supersymmetric system can have different intermediate Hamiltonians corresponding to different factorizations. We derive the necessary and sufficient conditions for the latter system to possess intermediate Hamiltonians for the case. We then show that whenever it has (at least) one intermediate Hamiltonian, it can admit second-order parasupersymmetry and a generalized 2-fold superalgebra. As an illustration, we construct a set of generalized Pöschl–Teller potentials of this kind.     

Theoretical study of optical recording with a solid immersion lens illuminated by focused double-ring-shaped radially-polarized beam

Based on the Richards–Wolf vector diffraction theory, the intensity distributions in the recording sample near a solid immersion lens are calculated for two different radially-polarized beams ( and modes). Numerical results show that a double-ring-shaped mode focusing has some excellent features in near-field optical storage, compared with a single-ring-shaped mode focusing. The recording density is markedly improved, the focal depth of the near-field recording system is substantially increased, and a subsurface recording is effectively obtained using the mode focusing.     

Scaling and long-range dependence in option pricing I: Pricing European option with transaction costs under the fractional Black–Scholes model

This paper deals with the problem of discrete time option pricing by the fractional Black–Scholes model with transaction costs. By a mean self-financing delta-hedging argument in a discrete time setting, a European call option pricing formula is obtained. The minimal price of an option under transaction costs is obtained as timestep , which can be used as the actual price of an option. In fact, is an adjustment to the volatility in the Black–Scholes formula by using the modified volatility to replace the volatility σ, where is the Hurst exponent, and k is a proportional transaction cost parameter. In addition, we also show that timestep and long-range dependence have a significant impact on option pricing.     

Three equations of state for solids considering thermal effect

 The Einstein model to consider thermal effect in universal equations of state (UEOS) is modified. It is proposed that the zero-point vibration term should be deleted in a thermal UEOS, and the parameters cannot be directly taken as experimental data at a reference temperature, V_R, B_R, and , but their values at absolute zero temperature, V₀, B₀, and . An approach is proposed to solve V₀, B₀, and from V_R, B_R, and . The approaches are applied to three typical universal EOSs, including the Baonza, mGLJ and Morse EOSs. The numerical results show that the solved values of parameters are almost identical for different EOSs. And the thermo-physical properties predicted through different EOSs are almost identical at zero- and low-pressure conditions, once the same approach and input experimental data are used to solve the parameters. It is concluded that the prediction of thermo-physical properties at zero- and low-pressure conditions cannot be taken as the criteria to judge the applicability of a universal EOS.     

Step formation on hydrogen-etched 6H-SiC{0 0 0 1} surfaces

The formation of step bunches and/or facets on hydrogen-etched 6H-SiC(0 0 0 1) and () surfaces has been studied, using both nominally on-axis and intentionally miscut (i.e. vicinal) substrates. It is found that small miscuts on the (0 0 0 1) surface produce full unit-cell high steps, while half unit-cell high steps are observed on the () surface. The observed step normal direction is found to be for both surfaces. Hence, for intentionally miscut material, a miscut oriented towards this direction produces much better order in the step array compared to a miscut oriented towards a direction. For (0 0 0 1) vicinal surfaces that are miscut towards the direction, the formation of surface ripples is observed for 3° miscut and the development of small facets (nanofacets) is found for higher miscut angles. Much less faceting is observed on miscut () surfaces. Additionally, the (0 0 01) surface is found to have a much larger spatial anisotropy in step energies than the () surface.     

Absolute photoionization cross sections with ultra-high energy resolution for Ar, Kr, Xe and N2 in inner-shell ionization regions

The high-resolution absolute photoionization cross sections for Ar, Kr, Xe and N₂ in the inner-shell ionization region have been measured using a multi-electrode ion chamber and monochromatized synchrotron radiation. The energy ranges of the incident photons for the target gases were as follows: Ar: 242–252 eV (2p Rydberg excitation), Kr: 1650–1770 eV (near the 2p ionization thresholds), Xe: 665–720 eV (near the 3d ionization thresholds) and 880–1010 eV (near the 3p ionization thresholds), N₂: 400–425 eV (N 1s excitation and ionization). It is the first time to measure the absolute ionization cross sections of Ar, Kr, Xe and N₂ over the present energy ranges with the energy resolution of over 10,000. The natural lifetime widths of , , and resonances for Ar, resonance for Xe, and resonance for N₂ have been obtained based on the cross sections determined. The ionization energies into the Ar⁺ (), Ar⁺ () and Xe⁺ () ionic states are also determined using the Rydberg formula.     

Graphic Bernstein results in curved pseudo-Riemannian manifolds

We generalize a Bernstein-type result due to Albujer and Alías, for maximal surfaces in a curved Lorentzian product 3-manifold of the form , to higher dimension and codimension. We consider M a complete spacelike graphic submanifold with parallel mean curvature, defined by a map f:Σ₁→Σ₂ between two Riemannian manifolds and of sectional curvatures K₁ and K₂, respectively. We take on Σ₁×Σ₂ the pseudo-Riemannian product metric g₁−g₂. Under the curvature conditions, and K₁≥K₂, we prove that, if the second fundamental form of M satisfies an integrability condition, then M is totally geodesic, and it is a slice if at some point. For bounded K₁, K₂ and hyperbolic angle θ, we conclude that M must be maximal. If M is a maximal surface and , we show M is totally geodesic with no need for further assumptions. Furthermore, M is a slice if at some point pΣ₁, K₁(p)>0, and if Σ₁ is flat and K₂<0 at some point f(p), then the image of f lies on a geodesic of Σ₂.     

Measurement of at

We present a measurement of the cross section for Z boson production times the branching fraction to tau lepton pairs in collisions at . The measurement is performed in the channel in which one tau lepton decays into a muon and neutrinos, and the other tau lepton decays hadronically or into an electron and neutrinos. The data sample corresponds to an integrated luminosity of 1.0 fb⁻¹ collected with the DØ detector at the Fermilab Tevatron Collider. The sample contains 1511 candidate events with an estimated 20% background from jets or muons misidentified as tau leptons. We obtain , which is consistent with the standard model prediction.     

Fractional quasiexcitons in incompressible electron liquids

A new kind of many-body excitonic state composed of fractionally charged constituents is introduced. The constituents are a trion (X^-) embedded in an incompressible electron liquid and Laughlin quasiholes (QH's). Laughlin electron–trion correlations lead to an effective trion charge of -e/3. This many-body excitation is called “quasiexciton” and denoted by to distinguish it from a normal trion. The can bind one or two (e/3)-charged QH's, giving a neutral or a positive . The energy spectra and photoluminescence from radiative quasiexciton decay are studied numerically and interpreted using a generalized composite Fermion model of the e–X^- fluid.     

Gate-controlled de Haas–van Alphen effect in an interacting two-dimensional electron system

We have measured the de Haas–van Alphen (dHvA) oscillations of a gated two-dimensional electron system formed in a modulation-doped AlGaAs/GaAs heterojunction by means of a novel and highly sensitive cantilever magnetometer. We achieve a sensitivity of at a magnetic field by detecting the deflection of the cantilever using a fiber optic interferometer. The dHvA oscillation at ν=1 yields a thermodynamic energy gap that scales linearly with the applied magnetic field for . The slope corresponds to an exchange enhanced g factor g^*=3.5±0.3 originating from electron–electron interaction in the spin-polarized state of the 2DES.     

Intensity transformation of vector Bessel beams using a multilayer system

We theoretically investigate the generation of vector Bessel beams of the order m using a phase shifted superposition of TE and TM electromagnetic Bessel beams. Such Bessel beams are characterized by the intensity profile described by the superposition of squared Bessel functions of the orders (m-1) and (m+1). We derive the conditions for creating the special distributions of the intensity, which are determined by only one Bessel function, or . We offer the approach of intensity transformation based on the Bessel beam transmission through a multilayer system. Finally, we reveal the perfect intensity transformation transferring the whole energy from - to -profile of intensity distribution.     

Improving photovoltaic properties via electric-field-induced orientation of conjugated polymer

A high electric field is applied to polarize the undoped MEH-PPV and the MEH-PPV: C₆₀ composite thin film in the process of spin-coating. Due to the polarization causing the orientation of the MEH-PPV chains, the resulting thin-film devices show improved photovoltaic properties. For undoped MEH-PPV devices, oriented under the electric field of 6×10³ V cm⁻¹, the short-circuit current and the external quantum efficiency (EQE) are enhanced by a factor of 2.5 and 2, respectively. For MEH-PPV–fullerene composite devices, oriented under the same field, the and the EQE are improved by a factor of 1.8 and 1.7, respectively.     

Complex CKM matrix, spontaneous CP violation and generalized symmetry

The multi-Higgs models having spontaneous CP violation (SPCPV) and natural flavor conservation (NFC) lead to a real CKM matrix V contradicting current evidence in favour of a complex V. This contradiction can be removed by using a generalized μ–τ (called 23) symmetry in place of the discrete symmetry conventionally used to obtain NFC. If the 23 symmetry is exact then the Higgs induced flavour changing neutral currents (FCNC) vanish as in the case of NFC. 23 breaking introduces SPCPV, a phase in V and suppressed FCNC among quarks. The FCNC couplings between i and j generations show a hierarchy with the result that the FCNC can have observable consequences in B mixing without conflicting with the mixing. Detailed fits to the quark masses and the CKM matrix are used to obtain the (complex) couplings and . Combined constraints from flavour and CP violations in the K, B_d, B_s, D mesons are analyzed within the model. They allow (i) relatively light Higgs, 100–150 GeV (ii) measurable extra contributions to the magnitudes and phases of the mixing amplitudes and (iii) the mixing at the current sensitivity level.     

Influence of spin on the activation energies at

The activation energy Δ of the fractional quantum Hall state at constant filling factor and also at and has been measured as a function of the perpendicular magnetic field B while modulating the electron density via a top gate. At small magnetic fields we observe a linear increase of Δ with the magnetic field. The slope of Δ vs. B allows us to directly extract the composite fermion g-factor.     

The local Hurst exponent of the financial time series in the vicinity of crashes on the Polish stock exchange market

We investigate the local fractal properties of the financial time series based on the whole history evolution (1991–2007) of the Warsaw Stock Exchange Index (WIG), connected with the largest developing financial market in Europe. Calculating the so-called local time-dependent Hurst exponent for the WIG time series we find the dependence between the behavior of the local fractal properties of the WIG time series and the crashes’ appearance on the financial market. We formulate the necessary conditions based on the behavior which have to be satisfied if the rupture or crash point is expected soon. As a result we show that the signal to sell or the signal to buy on the stock exchange market can be translated into evolution pattern. We also find a relation between the rate of the drop and the total correction the WIG index gains after the crash. The current situation on the market, particularly related to the recent Fed intervention in September ’07, is also discussed.     

Optical characterization of the heating performance of microchannel fluid flow

The temperature dependent quantum efficiency of fluorescent dyes can be used to measure changes in temperature of the fluorescent dye molecules. This paper describes the use of Rhodamine dye as a temperature sensitive based fluorescence indicator for the characterization of heating in a pressure driven microfluidic device with high spatial resolution. A microheating element is used to control the temperature of the fluid in order to create localized heating in the microchannel. The temperature dependent fluorescence intensity of Rhodamine 6G for a concentration of is characterized with a 5th order polynomial then used to detect the temperature of the fluid in a microchannel. Fluid temperatures in the range of 20– are measured with an uncertainty of using a confocal fluorescence microscope. This method enables the characterization, imaging and mapping of three-dimensional temperature gradients within a microchannel.     

Epitaxial Heusler alloy films on GaAs(0 0 1) substrates

We present results on fabrication, and structural and electrical properties of single-crystal heterostructures grown by molecular beam epitaxy. The exact stoichiometry of the Heusler alloy films can be achieved for almost lattice matched films. As evidenced by high-resolution X-ray diffraction, transmission electron microscopy, and resistivity measurements, we find an optimum growth temperature of , to obtain ferromagnetic layers with high crystal and interface perfection as well as high degree of atomic ordering. .     

Observation of γ-delayed 3α breakup of the 15.11 and 12.71 MeV states in C

The reactions at 4.9 MeV and at 8.5 MeV have been used to investigate the γ decay of states in ¹²C. By measuring the four-body final state in complete kinematics we are able to detect γ transitions indirectly. We find γ transitions from the 15.11 MeV state in ¹²C to the 12.71, 11.83, 10.3 and 7.65 MeV states followed by their breakup into three α particles. The relative γ-ray branching ratios obtained are (1.2±0.3), (0.32±0.12), (1.4±0.2) and (4.4±0.8)%, respectively, with the remaining (92.7±1.0)% of the γ decays going to the bound states. We obtain Γ_α/Γ=(2.8±1.2)% for the isospin-forbidden α decay of the 15.11 MeV state. From the 12.71 MeV state we find γ transitions to the 10.3 and 7.65 MeV states. The relative γ-ray branching ratios are and , respectively, with the remaining of the γ decays going to the bound states. Finally, we discuss the relation between the β decay of ¹²N and ¹²B to states in ¹²C and the γ decay of the 15.11 MeV analog in ¹²C to the same states.