2,591 research outputs found
Numerical Study of Photo-Induced Dynamics in Double-Exchange Model
Photo-induced spin and charge dynamics in double-exchange model are
numerically studied. The Lanczos method and the density-matrix
renormalization-group method are applied to one-dimensional finite-size
clusters. By photon irradiation in a charge ordered (CO) insulator associated
with antiferromagnetic (AFM) correlation, both the CO and AFM correlations
collapse rapidly, and appearances of new peaks inside of an insulating gap are
observed in the optical spectra and the one-particle excitation spectra. Time
evolutions of the spin correlation and the in-gap state are correlated with
each other, and are governed by the transfer integral of conduction electrons.
Results are interpreted by the charge kink/anti-kink picture and their
effective motions which depend on the localized spin correlation. Pump-photon
density dependence of spin and charge dynamics are also studied. Roles of spin
degree of freedom are remarkable in a case of weak photon density. Implications
of the numerical results for the pump-probe experiments in perovskite
manganites are discussed.Comment: 16 pages, 16 figure
Modeling near-field tsunami observations to improve finite-fault slip models for the 11 March 2011 Tohoku earthquake
The massive tsunami generated by the 11 March 2011 Tohoku earthquake (M_w 9.0) was widely recorded by GPS buoys, wave gauges, and ocean bottom pressure sensors around the source. Numerous inversions for finite-fault slip time histories have been performed using seismic and/or geodetic observations, yielding generally consistent patterns of large co-seismic slip offshore near the hypocenter and/or up-dip near the trench, where estimated peak slip is ~60 m. Modeling the tsunami generation and near-field wave processes using two detailed rupture models obtained from either teleseismic P waves or high-rate GPS recordings in Japan allows evaluation of how well the finite-fault models account for the regional tsunami data. By determining sensitivity of the tsunami calculations to rupture model features, we determine model modifications that improve the fit to the diverse tsunami data while retaining the fit to the seismic and geodetic observations
Rank-Ordering Statistics of Extreme Events: Application to the Distribution of Large Earthquakes
Rank-ordering statistics provides a perspective on the rare, largest elements
of a population, whereas the statistics of cumulative distributions are
dominated by the more numerous small events. The exponent of a power law
distribution can be determined with good accuracy by rank-ordering statistics
from the observation of only a few tens of the largest events. Using analytical
results and synthetic tests, we quantify the systematic and the random errors.
We also study the case of a distribution defined by two branches, each having
a power law distribution, one defined for the largest events and the other for
smaller events, with application to the World-Wide (Harvard) and Southern
California earthquake catalogs. In the case of the Harvard moment catalog, we
make more precise earlier claims of the existence of a transition of the
earthquake magnitude distribution between small and large earthquakes; the
-values are for large shallow earthquakes and for smaller shallow earthquakes. However, the cross-over
magnitude between the two distributions is ill-defined. The data available at
present do not provide a strong constraint on the cross-over which has a
probability of being between magnitudes and for shallow
earthquakes; this interval may be too conservatively estimated. Thus, any
influence of a universal geometry of rupture on the distribution of earthquakes
world-wide is ill-defined at best. We caution that there is no direct evidence
to confirm the hypothesis that the large-moment branch is indeed a power law.
In fact, a gamma distribution fits the entire suite of earthquake moments from
the smallest to the largest satisfactorily. There is no evidence that the
earthquakes of the Southern California catalog have a distribution with tw
Elastic wave velocities of Apollo 12 rocks at high pressures
New results of P- and S-wave velocity measurements on two Apollo 12 rocks, 12052 and 12065, under pressures up to 10 kbars are presented. These rocks are basalt-like crystalline rocks with a bulk density of about 3.26 g/cm^3 and a mean atomic weight of 24.5. Like the Apollo 11 rocks, the velocities and the wave transmission efficiency are surprisingly low at low pressures despite their
relatively tight texture; at pressures below 200 bars, Q is estimated to be less than 100. The velocities increase very rapidly with pressure and approach 7.0 km/sec (P wave) and 3.9 km/sec (S wave) towards 10 kbars. No evidence is found for an increase of Q at 1 MHz with a reduction of the ambient pressure to 3 x 10^(-3) torr
The 25 October 2010 Mentawai tsunami earthquake (M_w 7.8) and the tsunami hazard presented by shallow megathrust ruptures
The 25 October 2010 Mentawai, Indonesia earthquake (M_w 7.8) ruptured the shallow portion of the subduction zone seaward of the Mentawai islands, off-shore of Sumatra, generating 3 to 9 m tsunami run-up along southwestern coasts of the Pagai Islands that took at least 431 lives. Analyses of teleseismic P, SH and Rayleigh waves for finite-fault source rupture characteristics indicate âŒ90 s rupture duration with a low rupture velocity of âŒ1.5 km/s on the 10° dipping megathrust, with total slip of 2â4 m over an âŒ100 km long source region. The seismic moment-scaled energy release is 1.4 Ă 10^(â6), lower than 2.4 Ă 10^(â6) found for the 17 July 2006 Java tsunami earthquake (M_w 7.8). The Mentawai event ruptured up-dip of the slip region of the 12 September 2007 Kepulauan earthquake (M_w 7.9), and together with the 4 January 1907 (M 7.6) tsunami earthquake located seaward of Simeulue Island to the northwest along the arc, demonstrates the significant tsunami generation potential for shallow megathrust ruptures in regions up-dip of great underthrusting events in Indonesia and elsewhere
Dynamical coupling and separation of multiple degrees of freedom in a photoexcited double-exchange system
We present a theory of ultrafast photo-induced dynamics in a spin-charge
coupled system, motivated by pump-probe experiments in perovskite manganites. A
microscopic picture for multiple dynamics in spin and charge degrees is focused
on. Real-time simulations are carried out by two complimentary methods. Our
calculation demonstrates that electron motion governs a short-time scale where
charge and spin dynamics are combined strongly, while, in a long-time scale
controlled by spin relaxation, charge sector does not follow remarkable change
in spin sector. Present results are in contrast to a conventional
double-exchange picture in equilibrium states.Comment: 5 pages, 4 figures, to be published in Phys. Rev. Let
Exact Analysis of ESR Shift in the Spin-1/2 Heisenberg Antiferromagnetic Chain
A systematic perturbation theory is developed for the ESR shift and is
applied to the spin-1/2 Heisenberg chain. Using the Bethe ansatz technique, we
exactly analyze the resonance shift in the first order of perturbative
expansion with respect to an anisotropic exchange interaction. Exact result for
the whole range of temperature and magnetic field, as well as asymptotic
behavior in the low-temperature limit are presented. The obtained g-shift
strongly depends on magnetic fields at low temperature, showing a significant
deviation from the previous classical result.Comment: 4 pages, 3 figures,to be published in Phys. Rev. Let
- âŠ