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

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 $U/t$ 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 $U/t$ 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

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 Nd$_2$Fe$_{14}$B-type compounds

Volume expansion $\Delta V / V$ associated with the spin reorientation
process of Nd$_2$Fe$_{14}$B-type compounds has been investigated in terms of
simple crystalline-electric-field (CEF) model. In this system, $\Delta V / V$
is shown to be a direct measure of second order CEF energy. Calculated
anomalies in $\Delta V / V$ associated with the first-order magnetization
process of Nd$_2$Fe$_{14}$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

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

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

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

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