4,834 research outputs found
A renormalizable supersymmetric SO(10) model
A realistic grand unified model has never been constructed in the literature
due to three major difficulties: the seesaw mechanism without spoiling gauge
coupling unification, the doublet-triplet splitting and the proton decay
suppression. We propose a renormalizable supersymmetric SO(10) model with all
these difficulties solved naturally by imposing an extra discrete symmetry.Comment: 12 page
Adaptive Domain Generalization via Online Disagreement Minimization
Deep neural networks suffer from significant performance deterioration when
there exists distribution shift between deployment and training. Domain
Generalization (DG) aims to safely transfer a model to unseen target domains by
only relying on a set of source domains. Although various DG approaches have
been proposed, a recent study named DomainBed, reveals that most of them do not
beat the simple Empirical Risk Minimization (ERM). To this end, we propose a
general framework that is orthogonal to existing DG algorithms and could
improve their performance consistently. Unlike previous DG works that stake on
a static source model to be hopefully a universal one, our proposed AdaODM
adaptively modifies the source model at test time for different target domains.
Specifically, we create multiple domain-specific classifiers upon a shared
domain-generic feature extractor. The feature extractor and classifiers are
trained in an adversarial way, where the feature extractor embeds the input
samples into a domain-invariant space, and the multiple classifiers capture the
distinct decision boundaries that each of them relates to a specific source
domain. During testing, distribution differences between target and source
domains could be effectively measured by leveraging prediction disagreement
among source classifiers. By fine-tuning source models to minimize the
disagreement at test time, target domain features are well aligned to the
invariant feature space. We verify AdaODM on two popular DG methods, namely ERM
and CORAL, and four DG benchmarks, namely VLCS, PACS, OfficeHome, and
TerraIncognita. The results show AdaODM stably improves the generalization
capacity on unseen domains and achieves state-of-the-art performance.Comment: 11 pages, 4 figure
Nonlinear Hall Effects in Strained Twisted Bilayer WSe
Recently, it has been pointed out that the twisting of bilayer WSe would
generate topologically non-trivial flat bands near the Fermi energy. In this
work, we show that twisted bilayer WSe (tWSe) with uniaxial strain
exhibits a large nonlinear Hall (NLH) response due to the non-trivial Berry
curvatures of the flat bands. Moreover, the NLH effect is greatly enhanced near
the topological phase transition point which can be tuned by a vertical
displacement field. Importantly, the nonlinear Hall signal changes sign across
the topological phase transition point and provides a way to identify the
topological phase transition and probe the topological properties of the flat
bands. The strong enhancement and high tunability of the NLH effect near the
topological phase transition point renders tWSe and related moire materials
new platforms for rectification and second harmonic generations.Comment: 5 pages, 3 figures. Comments are welcom
Inverting the General Order Sweep Map
Inspired by Thomas-Williams work on the modular sweep map, Garsia and Xin
gave a simple algorithm for inverting the sweep map on rational -Dyck
paths for a coprime pairs of positive integers. We find their idea
naturally extends for general Dyck paths. Indeed, we define a class of Order
sweep maps on general Dyck paths, using different sweep orders on level . We
prove that each such Order sweep map is a bijection. This includes sweep map
for general Dyck paths and incomplete general Dyck paths as special cases
A renormalizable supersymmetric SO(10) model with natural doublet-triplet splitting
We propose a renormalizable supersymmetric SO(10) model where the
doublet-triplet splitting problem is solved using the Dimopoulos-Wilczek
mechanism. An unwanted coupling is forbidden through a filter sector. To
suppress proton decay without spoiling gauge coupling unification, there is a
problem in the weak doublets which requires further improvements.Comment: 14 Pages, 1 figure
GRB 221009A with an unconventional precursor: a typical two-stage collapsar scenario?
As the brightest Gamma-Ray burst (GRB) ever detected, GRB 221009A may offer a
chance that reveals some interesting features which are hidden in those bursts
that are not so bright. There seems a very weak emission with a flux of
erg cm s between the first pulse (~s, is the trigger time) and the main burst (appears from
s). Thus the gap time between them is not really quiescent, and the
first pulse could be taken as an unconventional precursor, which may provide a
peculiar case study for the GRB-precursor phenomena. A two-stage collapsar
scenario is proposed as the most likely origin for this burst. In this model,
the jet for the precursor is produced during the initial core-collapse phase,
and should be weak enough not to disrupt the star when it breaks out of the
envelope, so that the fallback accretion process and the forming of the disk
could continue. We present an approach in which the duration and flux both
provide constraints on the luminosity () and the Lorentz factor at
the breakout time () of this weak jet. The estimated erg s and has an order of ten,
which are well consistent with the theoretical prediction. Besides, the weak
emission in the gap time could be interpreted as a MHD outflow due to a
magnetically driven wind during the period from the proto-neutron star phase to
forming the accretion disk in this scenario.Comment: 12 pages, 5 figures, submmited the revised version on June 17t
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