5,672 research outputs found
On extensions of representations for compact Lie groups
Let be a closed normal subgroup of a compact Lie group such that
is connected. This paper provides a necessary and sufficient condition
for every complex representation of to be extendible to , and also for
every complex -vector bundle over the homogeneous space to be trivial.
In particular, we show that the condition holds when the fundamental group of
is torsion free.Comment: 10 pages, AMS-LaTeX v1.
Model-based Offline Reinforcement Learning with Count-based Conservatism
In this paper, we propose a model-based offline reinforcement learning method
that integrates count-based conservatism, named . Our
method utilizes the count estimates of state-action pairs to quantify model
estimation error, marking the first algorithm of demonstrating the efficacy of
count-based conservatism in model-based offline deep RL to the best of our
knowledge. For our proposed method, we first show that the estimation error is
inversely proportional to the frequency of state-action pairs. Secondly, we
demonstrate that the learned policy under the count-based conservative model
offers near-optimality performance guarantees. Through extensive numerical
experiments, we validate that with hash code
implementation significantly outperforms existing offline RL algorithms on the
D4RL benchmark datasets. The code is accessible at
.Comment: Accepted in ICML 202
Incremental Few-Shot Object Detection via Simple Fine-Tuning Approach
In this paper, we explore incremental few-shot object detection (iFSD), which
incrementally learns novel classes using only a few examples without revisiting
base classes. Previous iFSD works achieved the desired results by applying
meta-learning. However, meta-learning approaches show insufficient performance
that is difficult to apply to practical problems. In this light, we propose a
simple fine-tuning-based approach, the Incremental Two-stage Fine-tuning
Approach (iTFA) for iFSD, which contains three steps: 1) base training using
abundant base classes with the class-agnostic box regressor, 2) separation of
the RoI feature extractor and classifier into the base and novel class branches
for preserving base knowledge, and 3) fine-tuning the novel branch using only a
few novel class examples. We evaluate our iTFA on the real-world datasets
PASCAL VOC, COCO, and LVIS. iTFA achieves competitive performance in COCO and
shows a 30% higher AP accuracy than meta-learning methods in the LVIS dataset.
Experimental results show the effectiveness and applicability of our proposed
method.Comment: Accepted to ICRA 202
Squeeze All: Novel Estimator and Self-Normalized Bound for Linear Contextual Bandits
We propose a linear contextual bandit algorithm with
regret bound, where is the dimension of contexts and isthe time
horizon. Our proposed algorithm is equipped with a novel estimator in which
exploration is embedded through explicit randomization. Depending on the
randomization, our proposed estimator takes contributions either from contexts
of all arms or from selected contexts. We establish a self-normalized bound for
our estimator, which allows a novel decomposition of the cumulative regret into
\textit{additive} dimension-dependent terms instead of multiplicative terms. We
also prove a novel lower bound of under our problem
setting. Hence, the regret of our proposed algorithm matches the lower bound up
to logarithmic factors. The numerical experiments support the theoretical
guarantees and show that our proposed method outperforms the existing linear
bandit algorithms.Comment: Accepted in Artificial Intelligence and Statistics 202
Ultraviolet photodepletion spectroscopy of dibenzo-18-crown-6-ether complexes with alkali metal cations
Ultraviolet photodepletion spectra of dibenzo-18-crown-6-ether complexes with alkali metal cations (M+-DB18C6, M = Cs, Rb, K, Na, and Li) were obtained in the gas phase using electrospray ionization quadrupole ion-trap reflectron time-of-flight mass spectrometry. The spectra exhibited a few distinct absorption bands in the wavenumber region of 35450−37800 cm^(−1). The lowest-energy band was tentatively assigned to be the origin of the S_0-S_1 transition, and the second band to a vibronic transition arising from the “benzene breathing” mode in conjunction with symmetric or asymmetric stretching vibration of the bonds between the metal cation and the oxygen atoms in DB18C6. The red shifts of the origin bands were observed in the spectra as the size of the metal cation in M^+-DB18C6 increased from Li^+ to Cs^+. We suggested that these red shifts arose mainly from the decrease in the binding energies of larger-sized metal cations to DB18C6 at the electronic ground state. These size effects of the metal cations on the geometric and electronic structures, and the binding properties of the complexes at the S_0 and S_1 states were further elucidated by theoretical calculations using density functional and time-dependent density functional theories
Angle Dependence of Landau Level Spectrum in Twisted Bilayer Graphene
In the context of the low energy effective theory, the exact Landau level
spectrum of quasiparticles in twisted bilayer graphene with small twist angle
is analytically obtained by spheroidal eigenvalues. We analyze the dependence
of the Landau levels on the twist angle to find the points, where the two-fold
degeneracy for twist angles is lifted in the nonzero modes and below/above
which massive/massless fermion pictures become valid. In the perpendicular
magnetic field of 10\,T, the degeneracy is removed at %angles around 3 degrees for a few low levels, specifically,
for the first pair of nonzero levels and
for the next pair. Massive quasiparticle
appears at in 10\,T, %angles less
than 1.17 degrees. which match perfectly with the recent experimental results.
Since our analysis is applicable to the cases of arbitrary constant magnetic
fields, we make predictions for the same experiment performed in arbitrary
constant magnetic fields, e.g., for B=40\,T we get and the sequence of angles for the pairs of nonzero energy levels. The symmetry restoration
mechanism behind the massive/massless transition is conjectured to be a
tunneling (instanton) in momentum space.Comment: 8 pages, 7 figures, version to appear in PR
Development and characterization of nine polymorphic microsatellite markers in the seven-spotted lady beetle, Coccinella septempunctata (Coleoptera: Coccinellidae)
In this study, nine microsatellite loci were isolated and characterized from the seven-spotted lady beetle, Coccinella septempunctata (Coleoptera: Coccinellidae). The loci were validated and characterized using 20 samples collected from five Korean localities. These results indicate that some loci were highly variable in terms of number of alleles (2 to 13), heterozygosity (0.10 to 0.40), and polymorphic information content (0.31 to 0.85). These microsatellite markers will be very valuable for population genetic studies of C. septempunctata.Key words: Seven-spotted lady beetle, Coccinella septempunctata, microsatellite Deoxyribonucleic acid (DNA)
Image-Object-Specific Prompt Learning for Few-Shot Class-Incremental Learning
While many FSCIL studies have been undertaken, achieving satisfactory
performance, especially during incremental sessions, has remained challenging.
One prominent challenge is that the encoder, trained with an ample base session
training set, often underperforms in incremental sessions. In this study, we
introduce a novel training framework for FSCIL, capitalizing on the
generalizability of the Contrastive Language-Image Pre-training (CLIP) model to
unseen classes. We achieve this by formulating image-object-specific (IOS)
classifiers for the input images. Here, an IOS classifier refers to one that
targets specific attributes (like wings or wheels) of class objects rather than
the image's background. To create these IOS classifiers, we encode a bias
prompt into the classifiers using our specially designed module, which
harnesses key-prompt pairs to pinpoint the IOS features of classes in each
session. From an FSCIL standpoint, our framework is structured to retain
previous knowledge and swiftly adapt to new sessions without forgetting or
overfitting. This considers the updatability of modules in each session and
some tricks empirically found for fast convergence. Our approach consistently
demonstrates superior performance compared to state-of-the-art methods across
the miniImageNet, CIFAR100, and CUB200 datasets. Further, we provide additional
experiments to validate our learned model's ability to achieve IOS classifiers.
We also conduct ablation studies to analyze the impact of each module within
the architecture.Comment: 8 pages, 4 figures, 4 table
- …