26,423 research outputs found
Interatomic collisions in two-dimensional and quasi-two-dimensional confinements with spin-orbit coupling
We investigate the low-energy scattering and bound states of two
two-component fermionic atoms in pure two-dimensional (2D) and quasi-2D
confinements with Rashba spin-orbit coupling (SOC). We find that the SOC
qualitatively changes the behavior of the 2D scattering amplitude in the
low-energy limit. For quasi-2D systems we obtain the analytic expression for
the effective-2D scattering amplitude and the algebraic equations for the
two-atom bound state energy. Based on these results, we further derive the
effective 2D interaction potential between two ultracold atoms in the quasi-2D
confinement with Rashba SOC. These results are crucial for the control of the
2D effective physics in quasi-2D geometry via the confinement intensity and the
atomic three-dimensional scattering length.Comment: 13pages, 5 figure
AutoAccel: Automated Accelerator Generation and Optimization with Composable, Parallel and Pipeline Architecture
CPU-FPGA heterogeneous architectures are attracting ever-increasing attention
in an attempt to advance computational capabilities and energy efficiency in
today's datacenters. These architectures provide programmers with the ability
to reprogram the FPGAs for flexible acceleration of many workloads.
Nonetheless, this advantage is often overshadowed by the poor programmability
of FPGAs whose programming is conventionally a RTL design practice. Although
recent advances in high-level synthesis (HLS) significantly improve the FPGA
programmability, it still leaves programmers facing the challenge of
identifying the optimal design configuration in a tremendous design space.
This paper aims to address this challenge and pave the path from software
programs towards high-quality FPGA accelerators. Specifically, we first propose
the composable, parallel and pipeline (CPP) microarchitecture as a template of
accelerator designs. Such a well-defined template is able to support efficient
accelerator designs for a broad class of computation kernels, and more
importantly, drastically reduce the design space. Also, we introduce an
analytical model to capture the performance and resource trade-offs among
different design configurations of the CPP microarchitecture, which lays the
foundation for fast design space exploration. On top of the CPP
microarchitecture and its analytical model, we develop the AutoAccel framework
to make the entire accelerator generation automated. AutoAccel accepts a
software program as an input and performs a series of code transformations
based on the result of the analytical-model-based design space exploration to
construct the desired CPP microarchitecture. Our experiments show that the
AutoAccel-generated accelerators outperform their corresponding software
implementations by an average of 72x for a broad class of computation kernels
Pion transverse-momentum spectrum and elliptic anisotropy of partially coherent source
In this letter, we study the pion momentum distribution of a coherent source
and investigate the influences of coherent emission on the pion
transverse-momentum () spectrum and elliptic anisotropy. With a partially
coherent source, constructed by a conventional viscous hydrodynamics model
(chaotic part) and a parameterized expanding coherent source model, we
reproduce the pion spectrum and elliptic anisotropy coefficient
in the peripheral Pb-Pb collisions at TeV. It
is found that the influences of coherent emission on the pion spectrum
and are related to the initial size and shape of the coherent
source, largely due to the interference effect. However, the effect of source
dynamical evolution on coherent emission is relatively small. The results of
the partially coherent source with 33% coherent emission and 67% chaotic
emission are consistent with the experimental measurements of the pion
spectrum, , and especially four-pion Bose-Einstein correlations.Comment: 8 pages, 4 figure
Thermodynamics of pairing transition in hot nuclei
The pairing correlations in hot nuclei Dy are investigated in terms
of the thermodynamical properties by covariant density functional theory. The
heat capacities are evaluated in the canonical ensemble theory and the
paring correlations are treated by a shell-model-like approach, in which the
particle number is conserved exactly. A S-shaped heat capacity curve, which
agrees qualitatively with the experimental data, has been obtained and analyzed
in details. It is found that the one-pair-broken states play crucial roles in
the appearance of the S shape of the heat capacity curve. Moreover, due to the
effect of the particle-number conservation, the pairing gap varies smoothly
with the temperature, which indicates a gradual transition from the superfluid
to the normal state.Comment: 13 pages, 4 figure
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