10,083 research outputs found
Noise spectra of stochastic pulse sequences: application to large scale magnetization flips in the finite size 2D Ising model
We provide a general scheme to predict and derive the contribution to the
noise spectrum of a stochastic sequence of pulses from the distribution of
pulse parameters. An example is the magnetization noise spectra of a 2D Ising
system near its phase transition. At , the low frequency spectra is
dominated by magnetization flips of nearly the entire system. We find that both
the predicted and the analytically derived spectra fit those produced from
simulations. Subtracting this contribution leaves the high frequency spectra
which follow a power law set by the critical exponents.Comment: 4 pages, 5 figures. We improved text and included a predicted noise
curve in Figure 4. 2 examples from Figure 3 are remove
Interdecadal variability of winter precipitation in Southeast China
Interdecadal variability of observed winter precipitation in Southeast China (1961β2010) is characterized by the first empirical orthogonal function of the three-monthly Standardized Precipitation Index (SPI) subjected to a 9-year running mean. For interdecadal time scales the dominating spatial modes represent monopole features involving the Arctic Oscillation (AO) and the sea surface temperature (SST) anomalies. Dynamic composite analysis (based on NCEP/NCAR reanalyzes) reveals the following results: (1) Interdecadal SPI-variations show a trend from a dryer state in the 1970s via an increase during the 1980s towards stabilization on wetter conditions commencing with the 1990s. (2) Increasing wetness in Southeast China is attributed to an abnormal anticyclone over south Japan, with northward transport of warm and humid air from the tropical Pacific to South China. (3) In mid-to-high latitudes the weakened southward flow of polar airmasses induces low-level warming over Eurasia due to stronger AO by warmer zonal temperature advection. This indicates that AO is attributed to the Southeast China precipitation increase influenced by circulation anomalies over the mid-to-high latitudes. (4) The abnormal moisture transport along the southwestern boundary of the abnormal anticyclone over south Japan is related to anomalous south-easterlies modulated by the SST anomalies over Western Pacific Ocean; a positive (negative) SST anomaly will strengthen (weaken) warm and humid air transport, leading to abundant (reduced) precipitation in Southeast China. That is both AO and SST anomalies determine the nonlinear trend observed in winter precipitation over Southeast China
Search for charmonium and bottomonium states in at B factories
We study the production of charmonium states in at B factories with (n=1,2,3), (m=1,2), and
. In the S and P wave case, contributions of tree-QED with one-loop
QCD corrections are calculated within the framework of nonrelativistic
QCD(NRQCD) and in the D-wave case only the tree-QED contribution are
considered. We find that in most cases the QCD corrections are negative and
moderate, in contrast to the case of double charmonium production , where QCD corrections are positive and large in most cases. We
also find that the production cross sections of some of these states in
are larger than that in by an
order of magnitude even after the negative QCD corrections are included. So we
argue that search for the X(3872), X(3940), Y(3940), and X(4160) in at B factories may be helpful to clarify the nature of these
states. For completeness, the production of bottomonium states in
annihilation is also discussed.Comment: 13pages, 4 figure
- β¦