260 research outputs found
Critical phenomena in gravitational collapse of Husain-Martinez-Nunez scalar field
We construct analytical models to study the critical phenomena in
gravitational collapse of the Husain-Martinez-Nunez massless scalar field. We
first use the cut-and-paste technique to match the conformally flat solution
( ) onto an outgoing Vaidya solution. To guarantee the continuity of the
metric and the extrinsic curvature, we prove that the two solutions must be
joined at a null hypersurface and the metric function in Vaidya spacetime must
satisfy some constraints. We find that the mass of the black hole in the
resulting spacetime takes the form , where the
critical exponent is equal to . For the case , we show
that the scalar field must be joined onto two pieces of Vaidya spacetimes to
avoid a naked singularity. We also derive the power-law mass formula with
. Compared with previous analytical models constructed from a
different scalar field with continuous self-similarity, we obtain the same
value of . However, we show that the solution with is not
self-similar. Therefore, we provide a rare example that a scalar field without
self-similarity also possesses the features of critical collapse.Comment: 14 pages, 6 figure
Tunneling Effect Near Weakly Isolated Horizon
The tunneling effect near a weakly isolated horizon (WIH) has been studied.
By applying the null geodesic method of Parikh and Wilczek and Hamilton-Jacibi
method of Angheben et al. to a weakly isolated horizon, we recover the
semiclassical emission rate in the tunneling process. We show that the
tunneling effect exists in a wide class of spacetimes admitting weakly isolated
horizons. The general thermodynamic nature of WIH is then confirmed.Comment: 7 pages, accepted for publication in Physical Review
On Newman-Penrose constants of stationary electrovacuum spacetimes
A theorem related to the Newman-Penrose constants is proven. The theorem
states that all the Newman-Penrose constants of asymptotically flat,
stationary, asymptotically algebraically special electrovacuum spacetimes are
zero. Straightforward application of this theorem shows that all the
Newman-Penrose constants of the Kerr-Newman spacetime must vanish.Comment: 11pages, no figures accepted by PR
Relation-dependent Contrastive Learning with Cluster Sampling for Inductive Relation Prediction
Relation prediction is a task designed for knowledge graph completion which
aims to predict missing relationships between entities. Recent subgraph-based
models for inductive relation prediction have received increasing attention,
which can predict relation for unseen entities based on the extracted subgraph
surrounding the candidate triplet. However, they are not completely inductive
because of their disability of predicting unseen relations. Moreover, they fail
to pay sufficient attention to the role of relation as they only depend on the
model to learn parameterized relation embedding, which leads to inaccurate
prediction on long-tail relations. In this paper, we introduce
Relation-dependent Contrastive Learning (ReCoLe) for inductive relation
prediction, which adapts contrastive learning with a novel sampling method
based on clustering algorithm to enhance the role of relation and improve the
generalization ability to unseen relations. Instead of directly learning
embedding for relations, ReCoLe allocates a pre-trained GNN-based encoder to
each relation to strengthen the influence of relation. The GNN-based encoder is
optimized by contrastive learning, which ensures satisfactory performance on
long-tail relations. In addition, the cluster sampling method equips ReCoLe
with the ability to handle both unseen relations and entities. Experimental
results suggest that ReCoLe outperforms state-of-the-art methods on commonly
used inductive datasets
Effect of CCR5-Δ32 Heterozygosity on HIV-1 Susceptibility: A Meta-Analysis
So far, many studies have investigated the distribution of CCR5 genotype between HIV-1 infected patients and uninfected people. However, no definite results have been put forward about whether heterozygosity for a 32-basepair deletion in CCR5 gene (CCR5-Δ32) can affect HIV-1 susceptibility.We performed a meta-analysis of 18 studies including more than 12000 subjects for whom the CCR5-Δ32 polymorphism was genotyped. Odds ratio (OR) with 95% confidence interval (CI) were employed to assess the association of CCR5-Δ32 polymorphism with HIV-1 susceptibility.Compared with the wild-type CCR5 homozygotes, the pooled OR for CCR5-Δ32 heterozygotes was 1.02 (95%CI, 0.88–1.19) for healthy controls (HC) and 0.95 (95%CI, 0.71–1.26) for exposed uninfected (EU) controls. Similar results were found in stratified analysis by ethnicity, sample size and method of CCR5-Δ32 genotyping.The meta-analysis indicated that HIV-1 susceptibility is not significantly affected by heterozygosity for CCR5-Δ32
Unsupervised Explanation Generation via Correct Instantiations
While large pre-trained language models (PLM) have shown their great skills
at solving discriminative tasks, a significant gap remains when compared with
humans for explanation-related tasks. Among them, explaining the reason why a
statement is wrong (e.g., against commonsense) is incredibly challenging. The
major difficulty is finding the conflict point, where the statement contradicts
our real world. This paper proposes Neon, a two-phrase, unsupervised
explanation generation framework. Neon first generates corrected instantiations
of the statement (phase I), then uses them to prompt large PLMs to find the
conflict point and complete the explanation (phase II). We conduct extensive
experiments on two standard explanation benchmarks, i.e., ComVE and e-SNLI.
According to both automatic and human evaluations, Neon outperforms baselines,
even for those with human-annotated instantiations. In addition to explaining a
negative prediction, we further demonstrate that Neon remains effective when
generalizing to different scenarios.Comment: Accepted to AAAI-2
DDT: Dual-branch Deformable Transformer for Image Denoising
Transformer is beneficial for image denoising tasks since it can model
long-range dependencies to overcome the limitations presented by inductive
convolutional biases. However, directly applying the transformer structure to
remove noise is challenging because its complexity grows quadratically with the
spatial resolution. In this paper, we propose an efficient Dual-branch
Deformable Transformer (DDT) denoising network which captures both local and
global interactions in parallel. We divide features with a fixed patch size and
a fixed number of patches in local and global branches, respectively. In
addition, we apply deformable attention operation in both branches, which helps
the network focus on more important regions and further reduces computational
complexity. We conduct extensive experiments on real-world and synthetic
denoising tasks, and the proposed DDT achieves state-of-the-art performance
with significantly fewer computational costs.Comment: The code is avaliable at: https://github.com/Merenguelkl/DD
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