2,812 research outputs found
The nonlinear field equation of the three-point correlation function of galaxies
Based on the field theory of density fluctuation under Newtonian gravity, we
obtain analytically the nonlinear equation of 3-pt correlation function
of galaxies in a homogeneous, isotropic, static universe. The density
fluctuations have been kept up to second order. By the Fry-Peebles ansatz and
the Groth-Peebles ansatz, the equation of becomes closed and differs
from the Gaussian approximate equation. Using the boundary condition inferred
from the data of SDSS, we obtain the solution at fixed
, which exhibits a shallow -shape along the angle and,
nevertheless, decreases monotonously along the radial . We show its
difference with the Gaussian solution. As a direct criterion of
non-Gaussianity, the reduced deviates from the Gaussianity
plane , exhibits a deeper -shape along and varies weakly along
, agreeing with the observed data.Comment: 11 pages, 6 figure
Leptophilic dark matter in gauged model in light of DAMPE cosmic ray excess
Motivated by the very recent cosmic-ray electron+positron excess observed by
DAMPE collaboration, we investigate a Dirac fermion dark matter (DM) in the
gauged model. DM interacts with the electron and muon via the
gauge boson . The model can explain the DAMPE data well.
Although a non-zero DM-nucleon cross section is only generated at one loop
level and there is a partial cancellation between and
couplings, we find that a large portion of mass is ruled out from
direct DM detection limit leaving the allowed mass to be close to two
times of the DM mass. Implications for and , and muon anomaly are also studied.Comment: Discussions added, version accepted by EPJ
Vacuum stability in stau-neutralino coannihilation in MSSM
The stau-neutralino coannihilation provides a feasible way to accommodate the
observed cosmological dark matter (DM) relic density in the minimal
supersymmetric standard model (MSSM). In such a coannihilation mechanism the
stau mass usually has an upper bound since its annihilation rate becomes small
with the increase of DM mass. Inspired by this observation, we examine the
upper limit of stau mass in the parameter space with a large mixing of staus.
We find that the stau pair may dominantly annihilate into dibosons and hence
the upper bound on the stau mass ( GeV) obtained from the
final states can be relaxed. Imposing the DM relic density constraint and
requiring a long lifetime of the present vacuum, we find that the lighter stau
mass can be as heavy as about 1.4 TeV for the stau maximum mixing. However, if
requiring the present vacuum to survive during the thermal history of the
universe, this mass limit will reduce to about 0.9 TeV. We also discuss the
complementarity of vacuum stability and direct detections in probing this stau
coannihilation scenario.Comment: 12 pages, 6 figure
Probing GeV-scale MSSM neutralino dark matter in collider and direct detection experiments
Given the recent constraints from the dark matter (DM) direct detections, we
examine a light GeV-scale (2-30 GeV) neutralino DM in the alignment limit of
the Minimal Supersymmetric Standard Model (MSSM). In this limit without
decoupling, the heavy CP-even scalar plays the role of the Standard Model
(SM) Higgs boson while the other scalar can be rather light so that the DM
can annihilate through the resonance or into a pair of to achieve the
observed relic density. With the current collider and cosmological constraints,
we find that such a light neutralino DM above 6 GeV can be excluded by the
XENON-1T (2017) limits while the survivied parameter space below 6 GeV can be
fully covered by the future germanium-based light dark matter detections (such
as CDEX), by the Higgs coupling precison measurements or by the production
process at an electron-positron collider (Higgs factory).Comment: 15 pages, 5 figures. Discussions and references added, version
accepted by PL
PTab: Using the Pre-trained Language Model for Modeling Tabular Data
Tabular data is the foundation of the information age and has been
extensively studied. Recent studies show that neural-based models are effective
in learning contextual representation for tabular data. The learning of an
effective contextual representation requires meaningful features and a large
amount of data. However, current methods often fail to properly learn a
contextual representation from the features without semantic information. In
addition, it's intractable to enlarge the training set through mixed tabular
datasets due to the difference between datasets. To address these problems, we
propose a novel framework PTab, using the Pre-trained language model to model
Tabular data. PTab learns a contextual representation of tabular data through a
three-stage processing: Modality Transformation(MT), Masked-Language
Fine-tuning(MF), and Classification Fine-tuning(CF). We initialize our model
with a pre-trained Model (PTM) which contains semantic information learned from
the large-scale language data. Consequently, contextual representation can be
learned effectively during the fine-tuning stages. In addition, we can
naturally mix the textualized tabular data to enlarge the training set to
further improve representation learning. We evaluate PTab on eight popular
tabular classification datasets. Experimental results show that our method has
achieved a better average AUC score in supervised settings compared to the
state-of-the-art baselines(e.g. XGBoost), and outperforms counterpart methods
under semi-supervised settings. We present visualization results that show PTab
has well instance-based interpretability
Simplified TeV leptophilic dark matter in light of DAMPE data
Using a simplified framework, we attempt to explain the recent DAMPE cosmic
flux excess by leptophilic Dirac fermion dark matter (LDM). The
scalar () and vector () mediator fields connecting LDM and
Standard Model particles are discussed. Under constraints of DM relic density,
gamma-rays, cosmic-rays and Cosmic Microwave Background (CMB), we find that the
couplings , , and can
produce the right bump in flux for a DM mass around 1.5 TeV with a
natural thermal annihilation cross-section today. Among them, coupling is tightly constrained by
PandaX-II data (although LDM-nucleus scattering appears at one-loop level) and
the surviving samples appear in the resonant region, . We also study the related collider signatures, such as dilepton
production , and muon anomaly. Finally,
we present a possible realization for such leptophilic dark matter.Comment: discussions added, version accepted by JHE
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