9,650 research outputs found
Random Walk over Basins of Attraction to Construct Ising Energy Landscapes
An efficient algorithm is developed to construct disconnectivity graphs by a
random walk over basins of attraction. This algorithm can detect a large number
of local minima, find energy barriers between them, and estimate local thermal
averages over each basin of attraction. It is applied to the SK spin glass
Hamiltonian where existing methods have difficulties even for a moderate number
of spins. Finite-size results are used to make predictions in the thermodynamic
limit that match theoretical approximations and recent findings on the free
energy landscapes of SK spin glasses.Comment: 2 Figures and 1 Table. To be published in Physical Review Letter
A convenient implementation of the overlap between arbitrary Hartree-Fock-Bogoliubov vacua for projection
Overlap between Hartree-Fock-Bogoliubov(HFB) vacua is very important in the
beyond mean-field calculations. However, in the HFB transformation, the
matrices are sometimes singular due to the exact emptiness () or full
occupation () of some single-particle orbits. This singularity may cause
some problem in evaluating the overlap between HFB vacua through Pfaffian. We
found that this problem can be well avoided by setting those zero occupation
numbers to some tiny values (e.g., ). This treatment does not
change the HFB vacuum state because are numerically zero
relative to 1. Therefore, for arbitrary HFB transformation, we say that the
matrices can always be nonsingular. From this standpoint, we present a
new convenient Pfaffian formula for the overlap between arbitrary HFB vacua,
which is especially suitable for symmetry restoration. Testing calculations
have been performed for this new formula. It turns out that our method is
reliable and accurate in evaluating the overlap between arbitrary HFB vacua.Comment: 5 pages, 2 figures. Published versio
Theory of resonant spin Hall effect
A biref review is presented on resonant spin Hall effect, where a tiny
external electric field induces a saturated spin Hall current in a
2-dimensional electron or hole gas in a perpendicular magnetic field. The
phenomenon is attributted to the energy level crossing associated with the
spin-orbit coupling and the Zeeman splitting. We summarize recent theoretical
development of the effect in various systems and discuss possible experiments
to observe the effect.Comment: 5 pages with 1 figure
Comment on 'Note on the dog-and-rabbit chase problem in introductory kinematics'
We comment on the recent paper by Yuan Qing-Xin and Du Yin-Xiao (Eur. J.
Phys. 29 (2008) N43-N45).Comment: 2 pages, no figure
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