14203442
Quantum-classical phase transition of escape rates in biaxial spin particles
By using a stereographic projection of the unit sphere of magnetization vector onto a complex plane for the equations of motion, the effect of an external magnetic field for integrability of the system is discussed. The properties of the Jest solutions and the scattering data are then investigated through introducing transformations other than the Riemann surface in order to avoid double-valued functions of the usual spectral parameter. The exact multisoliton solutions are investigated by means of the Binet-Cauchy formula. The results showed that under the action of an external magnetic field nonlinear magnetization depends essentially on two parameters: its center moves with a constant velocity, while its shape changes with another constant velocity; its amplitude and width vary periodically with time, while its shape is also dependent on time and is unsymmetric with respect to its center. The orientation of the nonlinear magnetization in the plane orthogonal to the anisotropy axis changes with an external magnetic field. The total magnetic momentum and the integral of the motion coincident with its z component depend on time. The mean number of spins derivated from the ground state in a localized magnetic excitations is dependent on time. The asymptotic behavior of multisoliton solutions, the total displacement of center, and the phase shift of the jth peak an also analyzed. [S0163-1829(99)07121-0].
94690392
Isovector channel of quarkmeson-coupling model and its effect on symmetry energy
Abstract The non-relativistic approximation of the quark–meson-coupling model has been discussed and compared with the Skyrme–Hartree–Fock model which includes spin exchanges. Calculations show that the spin-exchange interaction has important effect on the descriptions of finite nuclei and nuclear matter through the Fock exchange. Also in the quark–meson-coupling model, it is the Fock exchange that leads to a nonlinear density-dependent isovector channel and changes the density-dependent behavior of the symmetry energy.
118555345
Alternate proof of the Rowe-Rosensteel proposition and seniority conservation
In this thesis the properties of unbound nuclei like 12,13Li are studiedby extending the multistep shell model to the complex energy plane. Thenuclei 12Li and 13Li are described starting from the one-particle states in 10Liand two-particle states in 11Li. The ground state of 12Li is found to be anantibound state. No bound or antibound state is found in 13Li. It is alsoshown that the odd proton plays a minor role in these nuclei.This framework is also applied to study the recently proposed spin-alignedproton-neutron pair coupling scheme. For this the MSM is extended to theproton-neutron space as well as the isospin space. In the model, a nonorthogonalbasis is introduced, which allows us to identify simultaneously theroles played by all configurations. The four-particle, six-particle and eightparticlenuclei in the heaviest N = Z region are evaluated using the MSMbasis within the space spanned by the single 0g9/2 hole shell.A novel Monte Carlo representation in the complex energy plane is alsodeveloped for studying nuclear excitations in the continuum. The calculationson realistic potentials show a stable performance and high accuracy in the oneparticleand two-particle cases. This will provide a convenient tool to studyopen systems with many nucleons in the continuum.
121654775
The possible effect of scalar meson on the symmetry energy curve in the viewpoint of the quark-meson-coupling model
We give the energy density functional of quark-meson-coupling model within the Hartree-Fock approximation and make comparison with relativistic-mean-field and Skyrme-Hartree-Fock models. We find that the discrepancy of these models is mainly from the isovector channel of the energy density functional, which is also the major cause of different descriptions of symmetry energy against density. In the viewpoint of quark-meson-coupling model, the scalar meson through Fock exchange makes a density dependent form of the isovector channel which can soften the symmetry energy curve.
110752379
The High Dynamics Readout of PMT for BGO Calorimeter
For one cell of BGO-EM energy deposition of electron/gamma with energy above TeV is between 0.5 MIPs and 105 MIPs, the readout system need to cover this high dynamic range.
117939789
Magnetic shield of PMT used in DAMPE electromagnetic calorimeter
The magnetic characteristics of photomultiplier tube R5610A-01 are studied in this paper. The experimental data shows that the gain of R5610A-01 loses about 53% when the magnetic field is 3G along its +X axis. A cylinder of one-layer permalloy strip is able to reduce the effect of 3G magnetic field on the PMT's gain to less than 1%.
119095268
Cosmological Constant as Vacuum Energy Density of Quantum Field Theories on Noncommutative Spacetime
We propose a new approach to understand hierarchy problem for cosmological constant in terms of considering noncommutative nature of space-time. We calculate that vacuum energy density of the noncommutative quantum field theories in nontrivial background, which admits a smaller cosmological constant by introducing an higher noncommutative scale $\mu_{NC}\sim M_p$. The result $\rho_\Lambda\sim 10^{-6}\Lambda_{SUSY}^8M_p^4/\mu_{NC}^8$ yields cosmological constant at the order of current observed value for supersymmetry breaking scale at 10TeV. It is the same as Banks' phenomenological formula for cosmological constant.
118664939
Nearby supernova rates from the Lick Observatory Supernova Search – III. The rate–size relation, and the rates as a function of galaxy Hubble type and colour
This is the third paper of a series in which we present new measurements of the observed rates of supernovae (SNe) in the local Universe, determined from the Lick Observatory Supernova Search (LOSS). We have considered a sample of ∼1000 SNe and used an optimal subsample of 726 SNe (274 SNe Ia, 116 SNe Ibc and 324 SNe II) to determine our rates. We study the trend of the rates as a function of a few quantities available for our galaxy sample, such as luminosity in the B and K bands, stellar mass and morphological class. We discuss different choices (SN samples, input SN luminosity functions, inclination correction factors) and their effect on the rates and their uncertainties. A comparison between our SN rates and the published measurements shows that they are consistent with each other to within the uncertainties when the rate calculations are done in the same manner. Nevertheless, our data demonstrate that the rates cannot be adequately described by a single parameter using either galaxy Hubble types or B ― K colours. A secondary parameter in galaxy 'size', expressed by luminosity or stellar mass, is needed to adequately describe the rates in the rate-size relation: the galaxies of smaller sizes have higher SN rates per unit mass or per unit luminosity. The trends of the SN rates in galaxies of different Hubble types and colours are discussed. We examine possible causes for the rate-size relation. Physically, such a relation for the core-collapse SNe is probably linked to the correlation between the specific star-formation rate and the galaxy sizes, but it is not clear whether the same link can be established for SNe Ia. We discuss the two-component ('tardy' and 'prompt') model for SN Ia rates, and find that the SN Ia rates in young stellar populations might have a strong correlation with the core-collapse SN rates. We derive volumetric rates for the different SN types [e.g. for SNe Ia, a rate of (0.301 ± 0.062) x 10 ―4 SN Mpc ―3 yr ―1 at redshift 0] and compare them to the measurements at different redshifts. Finally, we estimate the SN rate for the Milky Way Galaxy to be 2.84 ± 0.60 SNe per century (with a systematic uncertainty of a factor of ∼2), consistent with published SN rates based on several different techniques.
14243928
Dilepton and photon productions from a coherent pion oscillation
Abstract Since the electromagnetic current for a pion system coincides with the third component of the isovector current, the isospin angular oscillation of a coherent field can be a significant source for the electromagnetic emissions. We study the characteristic dilepton and photon emissions from the classical pion field oscillation in the QCD vacuum. The general analytical solution obtained in the nonlinear σ model is used to calculate the electromagnetic current density, which exhibits a light-front singularity and decreases rapidly as inverse square of the proper time due to a longitudinal expansion. The momentum and invariant mass spectra of the direct photon and dilepton are calculated using the space-time evolution of the chiral condensate field.