9,079 research outputs found
The largest virialized dark halo in the universe
Using semi-analytic approach, we present an estimate of the properties of the
largest virialized dark halos in the present universe for three different
scenarios of structure formation: SCDM, LCDM and OCDM models. The resulting
virial mass and temperature increase from the lowest values of and 9.8 keV in OCDM, the mid-range values of and 31 keV in LCDM, to the highest values of
, 65 keV in SCDM. As compared with the
largest virialized object seen in the universe, the richest clusters of
galaxies, we can safely rule out the OCDM model. In addition, the SCDM model is
very unlikely because of the unreasonably high virial mass and temperature. Our
computation favors the prevailing LCDM model in which superclusters may be
marginally regarded as dynamically-virialized systems.Comment: 5 pages, Accepted by Int. J. Mod. Phys.
NCAGC: A Neighborhood Contrast Framework for Attributed Graph Clustering
Attributed graph clustering is one of the most fundamental tasks among graph
learning field, the goal of which is to group nodes with similar
representations into the same cluster without human annotations. Recent studies
based on graph contrastive learning method have achieved remarkable results
when exploit graph-structured data. However, most existing methods 1) do not
directly address the clustering task, since the representation learning and
clustering process are separated; 2) depend too much on data augmentation,
which greatly limits the capability of contrastive learning; 3) ignore the
contrastive message for clustering tasks, which adversely degenerate the
clustering results. In this paper, we propose a Neighborhood Contrast Framework
for Attributed Graph Clustering, namely NCAGC, seeking for conquering the
aforementioned limitations. Specifically, by leveraging the Neighborhood
Contrast Module, the representation of neighbor nodes will be 'push closer' and
become clustering-oriented with the neighborhood contrast loss. Moreover, a
Contrastive Self-Expression Module is built by minimizing the node
representation before and after the self-expression layer to constraint the
learning of self-expression matrix. All the modules of NCAGC are optimized in a
unified framework, so the learned node representation contains
clustering-oriented messages. Extensive experimental results on four attributed
graph datasets demonstrate the promising performance of NCAGC compared with 16
state-of-the-art clustering methods. The code is available at
https://github.com/wangtong627/NCAGC
Strong Lensing Probabilities in a Cosmological Model with a Running Primordial Power Spectrum
The combination of the first-year Wilkinson Microwave Anisotropy Probe (WMAP)
data with other finer scale cosmic microwave background (CMB) experiments (CBI
and ACBAR) and two structure formation measurements (2dFGRS and Lyman
forest) suggest a CDM cosmological model with a running spectral power
index of primordial density fluctuations. Motivated by this new result on the
index of primordial power spectrum, we present the first study on the predicted
lensing probabilities of image separation in a spatially flat CDM
model with a running spectral index (RSI-CDM model). It is shown that
the RSI-CDM model suppress the predicted lensing probabilities on
small splitting angles of less than about 4 compared with that of
standard power-law CDM (PL-CDM) model.Comment: 11 pages including 1 figures. Accepted for publication in Modern
Physics Letters A (MPLA), minor revision
Generation of rotational ground state HD ions in an ion trap using a resonance-enhanced threshold photoionization process
We report a method for producing ultracold HD+ molecular ions populated in a
rotational ground state in an ion trap based on [2+1'] resonance-enhanced
threshold photoionization (RETPI) and sympathetic cooling with the laser-cooled
Be ions. The effect of electric field of the ion trap on the RETPI process
of neutral HD molecules and the blackbody radiation (BBR) on the population
evolution of rotational states of the generated polar HD+ ions have been
studied. The initial rotational ground state population of HD ions is
0.93(12). After the cumulation time of 5 s, the rotational ground state
population is reduced to 0.77(8) due to the BBR coupling. This method of
generating ultracold state-selected HD ions is beneficial for the studies
in precision rovibrational spectroscopy, state-controlled cold chemical
reaction, and quantum logic spectroscopy.Comment: accepted by PRA, 7 pages, 7 figure
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