44,066 research outputs found

    Stripe Formation in Fermionic Atoms on 2-D Optical Lattice inside a Box Trap: DMRG Studies for Repulsive Hubbard Model with Open Boundary Condition

    Full text link
    We suggest that box shape trap enables to observe intrinsic properties of the repulsive Hubbard model in a fixed doping in contrast to the harmonic trap bringing about spatial variations of atom density profiles. In order to predict atomic density profile under the box trap, we apply the directly-extended density-matrix renormalization group method to 4-leg repulsive Hubbard model with the open boundary condition. Consequently, we find that stripe formation is universal in a low hole doping range and the stripe sensitively changes its structure with variations of U/tU/t and the doping rate. A remarkable change is that a stripe formed by a hole pair turns to one by a bi-hole pair when entering a limited strong U/tU/t range. Furthermore, a systematic calculation reveals that the Hubbard model shows a change from the stripe to the Friedel like oscillation with increasing the doping rate

    Metastability of R-Charged Black Holes

    Full text link
    The global stability of R-charged AdS black holes in a grand canonical ensemble is examined by eliminating the constraints from the action, but without solving the equations of motion, thereby constructing the reduced action of the system. The metastability of the system is found to set in at a critical value of the chemical potential which is conjugate to the R-charge. The relation among the small black hole, large black hole and the instability is discussed. The result is consistent with the metastability found in the AdS/CFT-conjectured dual field theory. The "renormalized" temperature of AdS black holes, which has been rather ad hoc, is suggested to be the boundary temperature in the sense of AdS/CFT correspondence. As a byproduct of the analysis, we find a more general solution of the theory and its properties are briefly discussed.Comment: 36 pages, 7 figures, v2 is the published version. the exposition is made slightly shorter and hopefully cleare

    Crystal-field-induced magnetostrictions in the spin reorientation process of Nd2_2Fe14_{14}B-type compounds

    Full text link
    Volume expansion ΔV/V\Delta V / V associated with the spin reorientation process of Nd2_2Fe14_{14}B-type compounds has been investigated in terms of simple crystalline-electric-field (CEF) model. In this system, ΔV/V\Delta V / V is shown to be a direct measure of second order CEF energy. Calculated anomalies in ΔV/V\Delta V / V associated with the first-order magnetization process of Nd2_2Fe14_{14}B are presented, which well reproduced the observations.Comment: 2 pages, 2 figures, to appear in J. Magn. Magn. Mate

    Initial Shock Waves for Explosive Nucleosynthesis in Type II Supernova

    Get PDF
    We have performed 1-dimensional calculations for explosive nucleosynthesis in collapse-driven supernova and investigated its sensitivity to the initial form of the shock wave. We have found the tendency that the peak temperature becomes higher around the mass cut if the input energy is injected more in the form of kinetic energy rather than internal energy. Then, the mass cut becomes larger, and, as a result, neutron-rich matter is less included in the ejecta; this is favorable for producing the observational data compared with a previous model. Our results imply that the standard method to treat various processes for stellar evolution, such as convection and electron capture during the silicon burning stage, are still compatible with the calculation of explosive nucleosynthesis.Comment: 20 pages, 6 figures, LaTe

    The Grounds For Time Dependent Market Potentials From Dealers' Dynamics

    Full text link
    We apply the potential force estimation method to artificial time series of market price produced by a deterministic dealer model. We find that dealers' feedback of linear prediction of market price based on the latest mean price changes plays the central role in the market's potential force. When markets are dominated by dealers with positive feedback the resulting potential force is repulsive, while the effect of negative feedback enhances the attractive potential force.Comment: 9 pages, 3 figures, proceedings of APFA

    R-Process Nucleosynthesis In Neutrino-Driven Winds From A Typical Neutron Star With M = 1.4 Msun

    Full text link
    We study the effects of the outer boundary conditions in neutrino-driven winds on the r-process nucleosynthesis. We perform numerical simulations of hydrodynamics of neutrino-driven winds and nuclear reaction network calculations of the r-process. As an outer boundary condition of hydrodynamic calculations, we set a pressure upon the outermost layer of the wind, which is approaching toward the shock wall. Varying the boundary pressure, we obtain various asymptotic thermal temperature of expanding material in the neutrino-driven winds for resulting nucleosynthesis. We find that the asymptotic temperature slightly lower than those used in the previous studies of the neutrino-driven winds can lead to a successful r-process abundance pattern, which is in a reasonable agreement with the solar system r-process abundance pattern even for the typical proto-neutron star mass Mns ~ 1.4 Msun. A slightly lower asymptotic temperature reduces the charged particle reaction rates and the resulting amount of seed elements and lead to a high neutron-to-seed ratio for successful r-process. This is a new idea which is different from the previous models of neutrino-driven winds from very massive (Mns ~ 2.0 Msun) and compact (Rns ~ 10 km) neutron star to get a short expansion time and a high entropy for a successful r-process abundance pattern. Although such a large mass is sometimes criticized from observational facts on a neutron star mass, we dissolve this criticism by reconsidering the boundary condition of the wind. We also explore the relation between the boundary condition and neutron star mass, which is related to the progenitor mass, for successful r-process.Comment: 14 pages, 2 figure
    • …