14,113 research outputs found
Automatic Engineering of Long Prompts
Large language models (LLMs) have demonstrated remarkable capabilities in
solving complex open-domain tasks, guided by comprehensive instructions and
demonstrations provided in the form of prompts. However, these prompts can be
lengthy, often comprising hundreds of lines and thousands of tokens, and their
design often requires considerable human effort. Recent research has explored
automatic prompt engineering for short prompts, typically consisting of one or
a few sentences. However, the automatic design of long prompts remains a
challenging problem due to its immense search space. In this paper, we
investigate the performance of greedy algorithms and genetic algorithms for
automatic long prompt engineering. We demonstrate that a simple greedy approach
with beam search outperforms other methods in terms of search efficiency.
Moreover, we introduce two novel techniques that utilize search history to
enhance the effectiveness of LLM-based mutation in our search algorithm. Our
results show that the proposed automatic long prompt engineering algorithm
achieves an average of 9.2% accuracy gain on eight tasks in Big Bench Hard,
highlighting the significance of automating prompt designs to fully harness the
capabilities of LLMs
Structural phase transitions in epitaxial perovskite films
Three different film systems have been systematically investigated to
understand the effects of strain and substrate constraint on the phase
transitions of perovskite films. In SrTiO films, the phase transition
temperature T was determined by monitoring the superlattice peaks
associated with rotations of TiO octahedra. It is found that T depends
on both SrTiO film thickness and SrRuO buffer layer thickness. However,
lattice parameter measurements showed no sign of the phase transitions,
indicating that the tetragonality of the SrTiO unit cells was no longer a
good order parameter. This signals a change in the nature of this phase
transition, the internal degree of freedom is decoupled from the external
degree of freedom. The phase transitions occur even without lattice relaxation
through domain formation. In NdNiO thin films, it is found that the
in-plane lattice parameters were clamped by the substrate, while out-of-plane
lattice constant varied to accommodate the volume change across the phase
transition. This shows that substrate constraint is an important parameter for
epitaxial film systems, and is responsible for the suppression of external
structural change in SrTiO and NdNiO films. However, in SrRuO films
we observed domain formation at elevated temperature through x-ray reciprocal
space mapping. This indicated that internal strain energy within films also
played an important role, and may dominate in some film systems. The final
strain states within epitaxial films were the result of competition between
multiple mechanisms and may not be described by a single parameter.Comment: REVTeX4, 14 figure
Hole Doping Dependence of the Coherence Length in Thin Films
By measuring the field and temperature dependence of magnetization on
systematically doped thin films, the critical current
density and the collective pinning energy are determined in
single vortex creep regime. Together with the published data of superfluid
density, condensation energy and anisotropy, for the first time we derive the
doping dependence of the coherence length or vortex core size in wide doping
regime directly from the low temperature data. It is found that the coherence
length drops in the underdoped region and increases in the overdoped side with
the increase of hole concentration. The result in underdoped region clearly
deviates from what expected by the pre-formed pairing model if one simply
associates the pseudogap with the upper-critical field.Comment: 4 pages, 4 figure
Scalable Control Variates for Monte Carlo Methods via Stochastic Optimization
Control variates are a well-established tool to reduce the variance of Monte Carlo estimators. However, for large-scale problems including high-dimensional and large-sample settings, their advantages can be outweighed by a substantial computational cost. This paper considers control variates based on Stein operators, presenting a framework that encompasses and generalizes existing approaches that use polynomials, kernels and neural networks. A learning strategy based on minimising a variational objective through stochastic optimization is proposed, leading to scalable and effective control variates. Novel theoretical results are presented to provide insight into the variance reduction that can be achieved, and an empirical assessment, including applications to Bayesian inference, is provided in support
Andreev Reflection and Spin Injection into and wave Superconductors
We study the effect of spin injection into and wave superconductors,
with an emphasis on the interplay between boundary and bulk spin transport
properties. The quantities of interest include the amount of non-equilibrium
magnetization (), as well as the induced spin-dependent current () and
boundary voltage (). In general, the Andreev reflection makes each of the
three quantities depend on a different combination of the boundary and bulk
contributions. The situation simplifies either for half-metallic ferromagnets
or in the strong barrier limit, where both and depend solely on the
bulk spin transport/relaxation properties. The implications of our results for
the on-going spin injection experiments in high cuprates are discussed.Comment: 4 pages, REVTEX, 1 figure included; typos correcte
Free-standing Fe2O3 nanomembranes enabling ultra-long cycling life and high rate capability for Li-ion batteries
With Fe2O3 as a proof-of-concept, free-standing nanomembrane structure is demonstrated to be highly advantageous to improve the performance of Li-ion batteries. The Fe2O3 nanomembrane electrodes exhibit ultra-long cycling life at high current rates with satisfactory capacity (808 mAh g-1 after 1000 cycles at 2 C and 530 mAh g-1 after 3000 cycles at 6 C) as well as repeatable high rate capability up to 50 C. The excellent performance benefits particularly from the unique structural advantages of the nanomembranes. The mechanical feature can buffer the strain of lithiation/delithiation to postpone the pulverization. The two-dimensional transport pathways in between the nanomembranes can promote the pseudo-capacitive type storage. The parallel-laid nanomembranes, which are coated by polymeric gel-like film and SEI layer with the electrolyte in between layers, electrochemically behave like numerous "mini-capacitors" to provide the pseudo-capacitance thus maintain the capacity at high rate
The Droplet State and the Compressibility Anomaly in Dilute 2D Electron Systems
We investigate the space distribution of carrier density and the
compressibility of two-dimensional (2D) electron systems by using the local
density approximation. The strong correlation is simulated by the local
exchange and correlation energies. A slowly varied disorder potential is
applied to simulate the disorder effect. We show that the compressibility
anomaly observed in 2D systems which accompanies the metal-insulator transition
can be attributed to the formation of the droplet state due to disorder effect
at low carrier densities.Comment: 4 pages, 3 figure
Transitions from small to large Fermi momenta in a one-dimensional Kondo lattice model
We study a one-dimensional system that consists of an electron gas coupled to
a spin-1/2 chain by Kondo interaction away from half-filling. We show that
zero-temperature transitions between phases with "small" and "large" Fermi
momenta can be continuous. Such a continuous but Fermi-momentum-changing
transition arises in the presence of spin anisotropy, from a Luttinger liquid
with a small Fermi momentum to a Kondo-dimer phase with a large Fermi momentum.
We have also added a frustrating next-nearest-neighbor interaction in the spin
chain to show the possibility of a similar Fermi-momentum-changing transition,
between the Kondo phase and a spin-Peierls phase, in the spin isotropic case.
This transition, however, appears to involve a region in which the two phases
coexist.Comment: The updated version clarifies the definitions of small and large
Fermi momenta, the role of anisotropy, and how Kondo interaction affects
Luttinger liquid phase. 12 pages, 5 figure
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