58,153 research outputs found
p-wave Feshbach molecules
We have produced and detected molecules using a p-wave Feshbach resonance
between 40K atoms. We have measured the binding energy and lifetime for these
molecules and we find that the binding energy scales approximately linearly
with magnetic field near the resonance. The lifetime of bound p-wave molecules
is measured to be 1.0 +/- 0.1 ms and 2.3 +/- 0.2 ms for the m_l = +/- 1 and m_l
= 0 angular momentum projections, respectively. At magnetic fields above the
resonance, we detect quasi-bound molecules whose lifetime is set by the
tunneling rate through the centrifugal barrier
Solar activity forecast with a dynamo model
Although systematic measurements of the solar polar magnetic field exist only
from mid 1970s, other proxies can be used to infer the polar field at earlier
times. The observational data indicate a strong correlation between the polar
field at a sunspot minimum and the strength of the next cycle, although the
strength of the cycle is not correlated well with the polar field produced at
its end. This suggests that the Babcock Leighton mechanism of poloidal field
generation from decaying sunspots involves randomness, whereas the other
aspects of the dynamo process must be reasonably ordered and deterministic.
Only if the magnetic diffusivity within the convection zone is assumed to be
high, we can explain the correlation between the polar field at a minimum and
the next cycle. We give several independent arguments that the diffusivity must
be of this order. In a dynamo model with diffusivity like this, the poloidal
field generated at the mid latitudes is advected toward the poles by the
meridional circulation and simultaneously diffuses towards the tachocline,
where the toroidal field for the next cycle is produced. To model actual solar
cycles with a dynamo model having such high diffusivity, we have to feed the
observational data of the poloidal field at the minimum into the theoretical
model. We develop a method of doing this in a systematic way. Our model
predicts that cycle 24 will be a very weak cycle. Hemispheric asymmetry of
solar activity is also calculated with our model and compared with
observational data.Comment: 17 pages, 18 figures, submitted to MNRA
Monte Carlo Algorithm for Simulating Reversible Aggregation of Multisite Particles
We present an efficient and exact Monte Carlo algorithm to simulate
reversible aggregation of particles with dedicated binding sites. This method
introduces a novel data structure of dynamic bond tree to record clusters and
sequences of bond formations. The algorithm achieves a constant time cost for
processing cluster association and a cost between and
for processing bond dissociation in clusters with bonds.
The algorithm is statistically exact and can reproduce results obtained by the
standard method. We applied the method to simulate a trivalent ligand and a
bivalent receptor clustering system and obtained an average scaling of
for processing bond dissociation in acyclic
aggregation, compared to a linear scaling with the cluster size in standard
methods. The algorithm also demands substantially less memory than the
conventional method.Comment: 8 pages, 3 figure
Induced fission of 240Pu
We study the fission dynamics of 240Pu within an implementation of the
Density Functional Theory (DFT) extended to superfluid systems and real-time
dynamics. We demonstrate the critical role played by the pairing correlations.
The evolution is found to be much slower than previously expected in this fully
non-adiabatic treatment of nuclear dynamics, where there are no symmetry
restrictions and all collective degrees of freedom (CDOF) are allowed to
participate in the dynamics.Comment: 8 pages, 4 figures, talk given at The 6th International Conference on
Fission and Properties of Neutron-Rich Nuclei, Sanibel Island, Florida,
November 6-2 (2016
Common Space of Spin and Spacetime
Given Lorentz invariance in Minkowski spacetime, we investigate a common
space of spin and spacetime. To obtain a finite spinor representation of the
non-compact homogeneous Lorentz group including Lorentz boosts, we introduce an
indefinite inner product space (IIPS) with a normalized positive probability.
In this IIPS, the common momentum and common variable of a massive fermion turn
out to be ``doubly strict plus-operators''. Due to this nice property, it is
straightforward to show an uncertainty relation between fermion mass and proper
time. Also in IIPS, the newly-defined Lagrangian operators are self-adjoint,
and the fermion field equations are derivable from the Lagrangians. Finally,
the nonlinear QED equations and Lagrangians are presented as an example.Comment: 17 pages, a reference corrected, final version published on
Foundations of Physics Letters in June of 2005, as a personal tribute to
Einstein and Dira
Nucleon Sigma Term and In-medium Quark Condensate in the Modified Quark-Meson Coupling Model
We evaluate the nucleon sigma term and in-medium quark condensate in the
modified quark-meson coupling model which features a density-dependent bag
constant. We obtain a nucleon sigma term consistent with its empirical value,
which requires a significant reduction of the bag constant in the nuclear
medium similar to those found in the previous works. The resulting in-medium
quark condensate at low densities agrees well with the model independent linear
order result. At higher densities, the magnitude of the in-medium quark
condensate tends to increase, indicating no tendency toward chiral symmetry
restoration.Comment: 9 pages, modified version to be publishe
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