811 research outputs found
Lie Algebraic Similarity Transformed Hamiltonians for Lattice Model Systems
We present a class of Lie algebraic similarity transformations generated by
exponentials of two-body on-site hermitian operators whose Hausdorff series can
be summed exactly without truncation. The correlators are defined over the
entire lattice and include the Gutzwiller factor
, and two-site products of density
and spin
operators. The resulting non-hermitian many-body Hamiltonian can be solved in a
biorthogonal mean-field approach with polynomial computational cost. The
proposed similarity transformation generates locally weighted orbital
transformations of the reference determinant. Although the energy of the model
is unbound, projective equations in the spirit of coupled cluster theory lead
to well-defined solutions. The theory is tested on the 1D and 2D repulsive
Hubbard model where we find accurate results across all interaction strengths.Comment: The supplemental material is include
Composite fermion-boson mapping for fermionic lattice models
We present a mapping of elementary fermion operators onto a quadratic form of
composite fermionic and bosonic operators. The mapping is an exact isomorphism
as long as the physical constraint of one composite particle per cluster is
satisfied. This condition is treated on average in a composite particle
mean-field approach, which consists of an ansatz that decouples the composite
fermionic and bosonic sectors. The theory is tested on the one- and
two-dimensional Hubbard models. Using a Bogoliubov determinant for the
composite fermions and either a coherent or Bogoliubov state for the bosons, we
obtain a simple and accurate procedure for treating the Mott insulating phase
of the Hubbard model with mean-field computational cost
Symmetry-projected wave functions in quantum Monte Carlo calculations
We consider symmetry-projected Hartree-Fock trial wave functions in constrained-path Monte Carlo (CPMC) calculations. Previous CPMC calculations have mostly employed Hartree-Fock (HF) trial wave functions, restricted or unrestricted. The symmetry-projected HF approach results in a hierarchy of wave functions with increasing quality: the more symmetries that are broken and restored in a self-consistent manner, the higher the quality of the trial wave function. This hierarchy is approximately maintained in CPMC calculations: the accuracy in the energy increases and the statistical variance decreases when further symmetries are broken and restored. Significant improvement is achieved in CPMC with the best symmetry-projected trial wave functions over those from simple HF. We analyze and quantify the behavior using the two-dimensional repulsive Hubbard model as an example. In the sign-problem-free region, where CPMC can be made exact but a constraint is deliberately imposed here, spin-projected wave functions remove the constraint bias. Away from half filling, spatial symmetry restoration in addition to that of the spin leads to highly accurate results from CPMC. Since the computational cost of symmetry-projected HF trial wave functions in CPMC can be made to scale algebraically with system size, this provides a potentially general approach for accurate calculations in many-fermion systems
MUX-PLMs: Data Multiplexing for High-throughput Language Models
The widespread adoption of large language models such as ChatGPT and Bard has
led to unprecedented demand for these technologies. The burgeoning cost of
inference for ever-increasing model sizes coupled with hardware shortages has
limited affordable access and poses a pressing need for efficiency approaches
geared towards high throughput and performance. Multi-input multi-output (MIMO)
algorithms such as data multiplexing, offer a promising solution with a
many-fold increase in throughput by performing inference for multiple inputs at
the cost of a single input. Yet these approaches are not currently performant
enough to be deployed in modern systems. We change that by developing MUX-PLMs,
a class of high throughput pre-trained language models (PLMs) trained with data
multiplexing, that can be fine-tuned for any downstream task to yield
high-throughput high-performance. Our novel multiplexing and demultiplexing
modules proficiently entangle and disentangle inputs, and enable
high-performance high throughput \muxplms{} that are competitive with vanilla
PLMs while achieving 2x/5x inference speedup with only a drop on a
broad suite of tasks
SWE-bench: Can Language Models Resolve Real-World GitHub Issues?
Language models have outpaced our ability to evaluate them effectively, but
for their future development it is essential to study the frontier of their
capabilities. We consider real-world software engineering to be a rich,
sustainable, and challenging testbed for evaluating the next generation of
language models. We therefore introduce SWE-bench, an evaluation framework
including software engineering problems drawn from real GitHub issues
and corresponding pull requests across popular Python repositories. Given
a codebase along with a description of an issue to be resolved, a language
model is tasked with editing the codebase to address the issue. Resolving
issues in SWE-bench frequently requires understanding and coordinating changes
across multiple functions, classes, and even files simultaneously, calling for
models to interact with execution environments, process extremely long contexts
and perform complex reasoning that goes far beyond traditional code generation.
Our evaluations show that both state-of-the-art proprietary models and our
fine-tuned model SWE-Llama can resolve only the simplest issues. Claude 2 and
GPT-4 solve a mere % and % of instances respectively, even when
provided with an oracle retriever. Advances on SWE-bench represent steps
towards LMs that are more practical, intelligent, and autonomous.Comment: Data, code, and leaderboard are available at https://www.swebench.co
CSTS: Conditional Semantic Textual Similarity
Semantic textual similarity (STS) has been a cornerstone task in NLP that
measures the degree of similarity between a pair of sentences, with
applications in information retrieval, question answering, and embedding
methods. However, it is an inherently ambiguous task, with the sentence
similarity depending on the specific aspect of interest. We resolve this
ambiguity by proposing a novel task called conditional STS (C-STS) which
measures similarity conditioned on an aspect elucidated in natural language
(hereon, condition). As an example, the similarity between the sentences "The
NBA player shoots a three-pointer." and "A man throws a tennis ball into the
air to serve." is higher for the condition "The motion of the ball." (both
upward) and lower for "The size of the ball." (one large and one small).
C-STS's advantages are two-fold: (1) it reduces the subjectivity and ambiguity
of STS, and (2) enables fine-grained similarity evaluation using diverse
conditions. C-STS contains almost 20,000 instances from diverse domains and we
evaluate several state-of-the-art models to demonstrate that even the most
performant fine-tuning and in-context learning models (GPT-4, Flan, SimCSE)
find it challenging, with Spearman correlation scores of <50. We encourage the
community to evaluate their models on C-STS to provide a more holistic view of
semantic similarity and natural language understanding
Nuclear factor-kappa B in the liver of patients with chronic hepatitis C: decreased RelA expression is associated with enhanced fibrosis progression
The mechanisms of liver damage in chronic hepatitis C virus (HCV) infection are poorly understood. The transcription factor, nuclear factor-kappa B (NF-kappa B), regulates the expression of genes involved in apoptosis, inflammation, and antiviral response. It plays a protective role in several forms of liver damage. In this study, we analyzed NF-kappa B by gel mobility shift assay and immunohistochemistry in liver biopsies from HCV-infected patients, and we have determined the hepatic levels of the components of the NF-kappa B system by semiquantitative polymerase chain reaction (PCR). We found that NF-kappa B was activated in the liver of patients with chronic hepatitis C. Neither NF-kappa B activity nor the RNA levels of NF-kappa B subunits showed correlation with liver inflammatory activity, viral load, or HCV genotype. By contrast, hepatic mRNA values of RelA, the main element of active NF-kappa B, correlated inversely with apoptosis (r = -.68; P <.05) and with the rate of fibrosis progression (r = -.51; P <.04). In intermediate/rapid fibrosers, RelA mRNA levels were significantly decreased as compared with slow fibrosers (P <.003) and with normal livers (P <.03). In conclusion, we found that NF-kappa B is activated in chronic HCV-infected livers, and that the expression of RelA is inversely correlated with liver cell apoptosis and with the rate of fibrosis progression. Our data thus suggest that RelA expression may protect against liver fibrosis and hepatocellular damage
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