Density of states and phase diagram of the antiferromagnetic spin chain with Dzyaloshinsky–Moriya interaction and spin-phonon coupling

The effects of DM interaction on the density-of-states, the dimerization and the phase diagram in the antiferromagnetic Heisenberg chain coupled with quantum phonons have been studied by a nonadiabatic analytical approach. The results show that the effect of the DM interaction is to increase the staggered antisymmetric spin exchange interaction order but to decrease the spin dimerization and their competitions result in the lattice dimerization ordering parameter to increase for large staggered DM interaction parameter β and decrease for small β. A crossover of β exists in which the dimerization ordering parameter changes non-monotonously. As the DM interaction parameter D increases, depending on the appropriate values of spin-phonon coupling, phonon frequency and β, the system undergoes phase transition from spin gapless state to gapped state or reversely and can even reenter between the two states. The relation between the phonon-staggered ordering parameter, the spin-dimer order parameter and the staggered DM interaction order parameter gives clearly their contributing weights to the lattice dimerization.     

Correlation among electronic polarizability, optical basicity and interaction parameter of Bi2O3–B2O3 glasses

For optical basicity and electronic polarizability, the previous studies basically concentrate on the wavelength range of the visible light region. However, heavy metal oxides glasses have a reputation of being good materials for infrared region. In this study, new data of the average electronic polarizability of the oxide ion _O^2-, optical basicity Λ and Yamashita–Kurosawa's interaction parameter A of Bi₂O₃–B₂O₃ glasses have been calculated in a wavelength range from 404.66 to 1083.03 nm. The present investigation suggests that both _O^2- and Λ increase gradually with increasing wave number, and A decreases with increasing wave number. Furthermore, close correlations are studied among _O^2-, Λ, A and refractive index n in this paper. Particularly, it has been found that a quantitative relationship between electronic polarizability and optical basicity is observed in a wavelength range from 404.66 to 1083.03 nm. Our present study extends over a wide range of _O^2-, Λ and A values.     

Electronic and optical properties of BaTe, BaSe and BaS from first principles

Electronic and optical properties of barium chalcogenide compounds BaX (X=S, Se and Te) in NaCl crystal structure are calculated using the band structure results obtained through the full potential linearized augmented plane wave (FP-LAPW) method. The exchange correlation potential is treated by the generalized gradient approximation. The real and imaginary parts of the dielectric function ε(ω), the optical absorption coefficient I(ω), the reflectivity R(ω) and the energy loss function are calculated. The calculated results show good agreement with the available experimental results, particularly in the low-energy region of the spectra. Furthermore the interband transitions responsible for the structures seen in the spectra are specified. It is shown that the chalcogen p states and Ba 5d states play a major role in optical transitions as initial and final states, respectively. The effect of the spin–orbit coupling on the optical properties is also investigated and found to be significant, especially in high-energy regions.     

Microscopic theory of Raman spectra of heavy fermion systems in the normal state

In this communication, we develop the microscopic theory of Raman spectra of the heavy fermion (HF) system in its normal state at low temperatures. The system is described by the Periodic Anderson Model along with the coupling of the phonon to the bare f-electrons as well as to the hybridization between the conduction band and the f-electrons. The phonon Green's function and the phonon self-energy are evaluated by the equations of motion method of Zubarev. The phonon spectral density function (SDF) is evaluated at low temperatures in the long wavelength limit. The calculation depicts three Raman active modes one of which corresponds to the strongly renormalized phonon at the value of the reduced frequency ) around 0.57 denoted as (P₀), and the other two at low reduced frequencies of and in the SDF. The effect of electron–phonon (EP) coupling on Raman excitation peaks is investigated to probe the nature of the electronic states of the system.     

The new multiplet, heavy baryon mass predictions, meson–baryon universality and effective supersymmetry in hadron spectrum

The recent measurement by CDF M(Σ_b)−M(Λ_b)=192 MeV is in striking agreement with our theoretical prediction M(Σ_b)−M(Λ_b)=194 MeV. In addition, the measured splitting agrees well with the predicted splitting of 22 MeV. We point out the connection between these predictions and an effective supersymmetry between mesons and baryons related by replacing a light antiquark by a light diquark. We discuss the theoretical framework behind these predictions and use it to provide additional predictions for the masses of spin- and spin- baryons containing heavy quarks, as well as for magnetic moments of Λ_b and Λ_c.     

Enhanced quantum searching via entanglement and partial diffusion

In this paper, we will define a quantum operator that performs the standard inversion about the mean only on a subspace of the system (Partial Diffusion Operator). This operator is used together with entanglement in a quantum search algorithm that runs in for searching an unstructured list of size N with M matches such that 1≤M≤N. We will show that the performance of the algorithm is more reliable than known fixed operators quantum search algorithms especially for multiple matches where we can get a solution after a single iteration with probability over 90% if the number of matches is approximately more than one-third of the search space. We will show that the algorithm will be able to handle the case where the number of matches M is unknown in advance in such that 1≤M≤N.     

Discrete symmetry and CP phase of the quark mixing matrix

A simple specific pattern of the two 3×3 quark mass matrices is proposed, resulting in a prediction of the CP phase of the charged-current mixing matrix V_CKM, i.e., sin2₁(β)=0.733, which is in remarkable agreement with data, i.e., sin2₁=0.728±0.056±0.023 from Belle and sin2β=0.722±0.040±0.023 from BaBar. This pattern can be maintained by a discrete family symmetry, an example of which is D₇, the symmetry group of the heptagon.     

: Hadronic molecules in effective field theory

We consider the implications from the possibility that the recently observed state X(3872) is a meson–antimeson molecule. We write an effective Lagrangian consistent with the heavy-quark and chiral symmetries needed to describe X(3872). We explore the consequences of the assumption that X(3872) is a molecular bound state of D^*0 and mesons for the existence of bound states in the and channels.     

Near tribimaximal neutrino mixing with symmetry

The discrete subgroup Δ(27) of SU(3) has the interesting multiplication rule , which is used to obtain near tribimaximal neutrino mixing. Using present neutrino oscillation data as input, this model predicts that the effective mass m_ee measured in neutrinoless double beta decay will be 0.14 eV.     

Analytical treatment of a generalized Hubbard Hamiltonian and of polarization in organic molecular aggregates

Starting with a Hamiltonian which comprises onsite, transfer and generalized Hubbard electron–electron plus a linear electron–phonon interaction, allowing in principle any number of sites i and excitations ν, we derive a matrix equation for the dimer problem. Regarding the general electronic sub-Hamiltonian coupled to an electric field H_F, an expression for the polarization P(t) is derived analytically.     

Corner bifurcations in non-smoothly forced impact oscillators

We consider an impacting mechanical system in which a particle at position u(t) impacts with a periodically moving obstacle at position z(t), the motion of which is non-smooth. In particular we look at corner events when u impacts with z very close to a point where z loses smoothness. We show that this leads, through a corner bifurcation, to complex dynamics in u which can include periodic orbits of arbitrary period and period-adding cascades. By analysing associated maps close to the corner event, we show that this dynamics can be understood in terms of the iterations of a two-dimensional, piecewise linear, discontinuous map. We also show some links between this analysis and the difficult problem of understanding the motion of three objects which may have simultaneous impacts.     

Correlators of matrix models on homogeneous spaces

We investigate the correlators of TrA_μA_ν in matrix models on homogeneous spaces: S² and S²×S². Their expectation value is a good order parameter to measure the geometry of the space on which non-commutative gauge theory is realized. They also serve as the Wilson lines which carry the minimum momentum. We develop an efficient procedure to calculate them through 1PI diagrams. We determine the large N scaling behavior of the correlators. The order parameter shows that fuzzy S²×S² acquires a 4-dimensional fractal structure in contrast to fuzzy S². We also find that the two point functions exhibit logarithmic scaling violations.     

Kaonic nuclear state search via reaction at rest on He target

Very recently, we have performed a couple of experiments, KEK PS-E549/E570, for the detailed study of the strange tribaryon S⁰(3115) obtained in KEK PS-E471. In contrast to the previous proton spectrum, no narrow (20 MeV) peak structure was found either in the inclusive ⁴He(stopped K⁻, p) or in the semi-inclusive ⁴He(stopped K⁻, pX^±) reaction channel, which is equivalent to the previous E471 event trigger condition. Detailed analysis of the present data and simulation shows that the peak, corresponding to S⁰(3115), has been an experimental artifact. Present analysis does not exclude the possible existence of a much wider structure.     

Frenkel exciton model of electron energy loss spectroscopy in -PTCDA

Recent experimental findings concerning electron energy loss spectroscopy in -Perylene-tetracarboxylic-dianhydride are analysed in terms of a Frenkel exciton model. Taking into account the energy dispersion of excitations with finite momentum transfer, the k-dependence of the dielectric tensor and the corresponding electron energy loss functions can be calculated. The exciton dispersion with a minimum at k≠0 yields a red shift of the lineshape of loss functions at large k, as observed experimentally.     

Theoretical analysis of pit formation in GaAs surfaces in picosecond and femtosecond laser ablation regimes

In the present work, the effect of pit formation in laser-ablated GaAs surfaces is analyzed theoretically. The formation of pits has been previously observed during laser ablation experiments in the picosecond (35 ps) and the femtosecond (100 fs) regimes. In the present work, it is shown theoretically that the thermal conductivity of the laser-ablated GaAs surface is changed both in the picosecond and the femtosecond regimes as compared to the unexposed surface. The variation in thermal conductivity of an ablated surface depends upon the fraction of the thermal conductivity of the cracks (), and the fraction of the cross-sectional area of the cracks (γ). In the picosecond regime (35 ps), the thermal conductivity of the ablated GaAs surface decreases (both for single and multiple laser pulses) for all the values of and γ (between 0.1 and 0.9) as compared to the thermal conductivity of a smooth film with no pits. In the femtosecond regime (100 fs), the thermal conductivity of the ablated surface increases or decreases (both for single and multiple laser pulses) depending upon the value of and γ.     

Search for intermediate mass magnetic monopoles and nuclearites with the SLIM experiment

SLIM is a large area experiment (440 m²) installed at the Chacaltaya cosmic ray laboratory since 2001, and about 100 m² at Koksil, Himalaya, since 2003. It is devoted to the search for intermediate mass magnetic monopoles (10⁷–10¹³ GeV/c²) and nuclearites in the cosmic radiation using stacks of CR-39 and Makrofol nuclear track detectors. In four years of operation it will reach a sensitivity to a flux of about 10^-15 cm^-2 s^-1 sr^-1. We present the results of the calibration of CR-39 and Makrofol and the analysis of a first sample of the exposed detector.     

Exact correlated kinetic energy related to the electron density for two-electron model atoms with harmonic confinement

For arbitrary interparticle interaction u(r₁₂), the model two-electron atom in the title is shown to be such that the ground-state electron density ρ(r) is determined uniquely by the correlated kinetic energy density t_R(r) of the relative motion. Explicit results for t_R(r) are presented for the Hookean atom with force constant k=1/4, and also for . Possible relevance of the Hookean atom treatment to the ground state of the helium atom itself is briefly discussed.     

A texture for neutrino oscillations and leptogenesis

In an economical system with only two heavy right-handed neutrinos, we postulate a new texture for 3×2 Dirac mass matrix m_D. This model implies one massless light neutrino and thus displays only two patterns of mass spectrum for light neutrinos, namely hierarchical or inverse-hierarchical. Both the cases can correctly reproduce all the current neutrino oscillation data with a unique prediction and for the hierarchical and the inverse-hierarchical cases, respectively, which can be tested in next generation neutrino-less double beta decay experiments. Introducing a single physical CP phase in m_D, we examine baryon asymmetry through leptogenesis. Interestingly, through the CP phase there are correlations between the amount of baryon asymmetry and neutrino oscillation parameters. We find that for a fixed CP phase, the hierarchical case also succeeds in generating the observed baryon asymmetry in our universe, plus a non-vanishing U_e3 which is accessible in future baseline neutrino oscillation experiments.     

An extensive indoor Rn/Rn monitoring in North-East India

The behaviour of ubiquitous radon (), thoron () and their progeny in the indoor atmosphere generally reflect a complex interplay between a number of processes, the most important of which are radioactive -decay, ventilation, attachment to aerosols and deposition on the surfaces. The present work involved a long-term (1997–2000) passive monitoring of and in the indoor environment of the North-Eastern region of India. This region being a zone of high seismicity, the indoor radon and thoron measurement of the region will provide a better insight and a valuable database for any study related to radon and thoron anomalies.