541 research outputs found
Low-velocity anisotropic Dirac fermions on the side surface of topological insulators
We report anisotropic Dirac-cone surface bands on a side-surface geometry of
the topological insulator BiSe revealed by first-principles
density-functional calculations. We find that the electron velocity in the
side-surface Dirac cone is anisotropically reduced from that in the
(111)-surface Dirac cone, and the velocity is not in parallel with the wave
vector {\bf k} except for {\bf k} in high-symmetry directions. The size of the
electron spin depends on the direction of {\bf k} due to anisotropic variation
of the noncollinearity of the electron state. Low-energy effective Hamiltonian
is proposed for side-surface Dirac fermions, and its implications are presented
including refractive transport phenomena occurring at the edges of tological
insulators where different surfaces meet.Comment: 4 pages, 2 columns, 4 figure
OWQ: Lessons learned from activation outliers for weight quantization in large language models
Large language models (LLMs) with hundreds of billions of parameters show
impressive results across various language tasks using simple prompt tuning and
few-shot examples, without the need for task-specific fine-tuning. However,
their enormous size requires multiple server-grade GPUs even for inference,
creating a significant cost barrier. To address this limitation, we introduce a
novel post-training quantization method for weights with minimal quality
degradation. While activation outliers are known to be problematic in
activation quantization, our theoretical analysis suggests that we can identify
factors contributing to weight quantization errors by considering activation
outliers. We propose an innovative PTQ scheme called outlier-aware weight
quantization (OWQ), which identifies vulnerable weights and allocates
high-precision to them. Our extensive experiments demonstrate that the 3.01-bit
models produced by OWQ exhibit comparable quality to the 4-bit models generated
by OPTQ
Thermodynamics of d-dimensional hard sphere fluids confined to micropores
We derive an analytical expression of the second virial coefficient of d-dimensional hard sphere fluids confined to slit pores by applying Speedy and Reiss’ interpretation of cavity space. We confirm that this coefficient is identical to the one obtained from the Mayer cluster expansion up to second order with respect to fugacity. The key step of both approaches is to evaluate either the surface area or the volume of the d-dimensional exclusion sphere confined to a slit pore. We, further, present an analytical form of thermodynamic functions such as entropy and pressure tensor as a function of the size of the slit pore. Molecular dynamics simulations are performed for d = 2 and d = 3, and the results are compared with analytically obtained equations of state. They agree satisfactorily in the low density regime, and, for given density, the agreement of the results becomes excellent as the width of the slit pore gets smaller, because the higher order virial coefficients become unimportant
Temporal Dynamic Quantization for Diffusion Models
The diffusion model has gained popularity in vision applications due to its
remarkable generative performance and versatility. However, high storage and
computation demands, resulting from the model size and iterative generation,
hinder its use on mobile devices. Existing quantization techniques struggle to
maintain performance even in 8-bit precision due to the diffusion model's
unique property of temporal variation in activation. We introduce a novel
quantization method that dynamically adjusts the quantization interval based on
time step information, significantly improving output quality. Unlike
conventional dynamic quantization techniques, our approach has no computational
overhead during inference and is compatible with both post-training
quantization (PTQ) and quantization-aware training (QAT). Our extensive
experiments demonstrate substantial improvements in output quality with the
quantized diffusion model across various datasets
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