2,976 research outputs found
Convergence rate of dimension reduction in Bose-Einstein condensates
In this paper, we study dimension reduction of the three-dimensional (3D)
Gross-Pitaevskii equation
(GPE) modelling Bose-Einstein condensation under different limiting
interaction and trapping frequencies parameter regimes.
Convergence rates for the dimension reduction of 3D ground state and dynamics
of the GPE in the case of disk-shaped condensation and cigar-shaped
condensation are reported based on our asymptotic and numerical results. In
addition, the parameter regimes in which the 3D GPE cannot be reduced to lower
dimensions are identified.Comment: 27pages; 9 figure
Bogoliubov Hamiltonian as Derivative of Dirac Hamiltonian via Braid Relation
In this paper we discuss a new type of 4-dimensional representation of the
braid group. The matrices of braid operations are constructed by q-deformation
of Hamiltonians. One is the Dirac Hamiltonian for free electron with mass m,
the other, which we find, is related to the Bogoliubov Hamiltonian for
quasiparticles in He-B with the same free energy and mass being m/2. In the
process, we choose the free q-deformation parameter as a special value in order
to be consistent with the anyon description for fractional quantum Hall effect
with .Comment: 3 pages, 5 figure
Spatial-Temporal Convolutional Attention for Mapping Functional Brain Networks
Using functional magnetic resonance imaging (fMRI) and deep learning to
explore functional brain networks (FBNs) has attracted many researchers.
However, most of these studies are still based on the temporal correlation
between the sources and voxel signals, and lack of researches on the dynamics
of brain function. Due to the widespread local correlations in the volumes,
FBNs can be generated directly in the spatial domain in a self-supervised
manner by using spatial-wise attention (SA), and the resulting FBNs has a
higher spatial similarity with templates compared to the classical method.
Therefore, we proposed a novel Spatial-Temporal Convolutional Attention (STCA)
model to discover the dynamic FBNs by using the sliding windows. To validate
the performance of the proposed method, we evaluate the approach on HCP-rest
dataset. The results indicate that STCA can be used to discover FBNs in a
dynamic way which provide a novel approach to better understand human brain.Comment: 5 pages, 5 figures, submitted to 20th IEEE International Symposium on
Biomedical Imaging (ISBI 2023
Impact of high-frequency pumping on anomalous finite-size effects in three-dimensional topological insulators
Lowering of the thickness of a thin-film three-dimensional topological
insulator down to a few nanometers results in the gap opening in the spectrum
of topologically protected two-dimensional surface states. This phenomenon,
which is referred to as the anomalous finite-size effect, originates from
hybridization between the states propagating along the opposite boundaries. In
this work, we consider a bismuth-based topological insulator and show how the
coupling to an intense high-frequency linearly polarized pumping can further be
used to manipulate the value of a gap. We address this effect within recently
proposed Brillouin-Wigner perturbation theory that allows us to map a
time-dependent problem into a stationary one. Our analysis reveals that both
the gap and the components of the group velocity of the surface states can be
tuned in a controllable fashion by adjusting the intensity of the driving field
within an experimentally accessible range and demonstrate the effect of
light-induced band inversion in the spectrum of the surface states for high
enough values of the pump.Comment: 6 pages, 3 figure
Influence of Spartina alterniflora invasion stages on macrobenthic communities on a tidal flat in Wenzhou Bay, China
Muitos habitats costeiros vêm sendo alterados substancialmente pela invasão de Spartina alterniflora no leste da China. Em 2007, em uma planície de maré situada em Wenzhou Bay, foram analisadas riqueza de espécies, densidade e diversidade da macrofauna bêntica em relação a diferentes estágios da invasão da gramínea e à estação do ano. Para as medidas de diversidade foram usados os índices de Margalef (R) e de Shannon (H'). Foram detectados efeitos significativos do estágio de invasão e época do ano sobre a macrofauna. As comunidades macrofaunais foram mais complexas nas manchas onde a invasão de S. alterniflora estava no seu início, quando considerados os locais onde as manchas estavam em estágios mais avançados. Através das análises de agrupamento e ordenação as comunidades puderam ser classificadas pelo tipo de habitat formado em cada estágio de invasão da Spartina. Os resultados indicaram que a biodiversidade aumentou no estágio de invasão inicial (idade de invasão de 1 a 2 anos), mas diminuiu gradativamente com os estágios intermediário (idade de invasão de 3 a 4 anos) e completo (idade de invasão de 5 a 6 anos), mostrando assim o efeito deletério de S. alterniflora sobre a estrutura da macrofauna presente no local.Many coastal habitats in eastern China are being substantially altered by the invasion of Spartina alterniflora. The species richness, density, Margalef's diversity index (R) and Shannon's diversity index (H') of macrobenthic communities on a tidal flat in Wenzhou Bay, China, were analyzed with the factors of invasion stage and season, in 2007. A significant effect of invasion stage, season, and the interaction between them on communities was detected. The macrobenthic community was more complex in the patch of initial S. alterniflora invasion than in the patches of some other invasion stages. Macrobenthic communities were classified by cluster and ordination in accordance with the habitat character of the S. alterniflora invasion stage. Our research demonstrated that the S. alterniflora invasion stage affected the macrobenthic communities significantly. The results indicated that biodiversity increased in the initial stage of invasion (invasion age 1-2 years) and then decreased in the stage of invasion underway (invasion age 3-4 years) and in the stage of invasion completed (invasion age 5-6 years); this phenomenon was related to the change in the S. alterniflora canopy which accompanied the invasion stages
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