The next generation of TeV detectors is expected to have a significantly enhanced performance. It is therefore constructive to search for new TeV candidates for observation. This paper focuses on TeV candidates among the high-synchrotron-peaked BL La
certae objects (HBLs) reported in the fourth catalog of active galactic nuclei detected by the Fermis Large Area Telescope, i.e., 4LAC. By cross-matching the Fermi data with radio and optical observations, we collected the multiwavelength features of 180 HBLs with known redshift. The data set contains 39 confirmed TeV sources and 141 objects whose TeV detection has not yet been reported (either not yet observed, or observed but not detected). Using two kinds of supervised machine-learning (SML) methods, we searched for new possible TeV candidates (PTCs) among the nondetected objects by assessing the similarity of their multi-wavelength properties to existing TeV-detected objects. The classification results of the two SML classifiers were combined and the 24 highest-confidence PTCs were proposed as the best candidates. We calculate, here, the 12 year averaged Fermi spectra of these PTCs and estimate their detectability by extrapolating the Fermi spectrum and including the extragalactic background light attenuation. Four candidates are suggested to have a high likelihood of being detected by the Large High Altitude Air Shower Observatory and 24 are candidates for the Cerenkov Telescope Array observations.
BICEP3 is a 520 mm aperture on-axis refracting telescope at the South Pole, which observes the polarization of the cosmic microwave background (CMB) at 95 GHz to search for the B-mode signal from inflationary gravitational waves. In addition to this
main target, we have developed a low-elevation observation strategy to extend coverage of the Southern sky at the South Pole, where BICEP3 can quickly achieve degree-scale E-mode measurements over a large area. An interesting E-mode measurement is probing a potential polarization anomaly around the CMB Cold Spot. During the austral summer seasons of 2018-19 and 2019-20, BICEP3 observed the sky with a flat mirror to redirect the beams to various low elevation ranges. The preliminary data analysis shows degree-scale E-modes measured with high signal-to-noise ratio.
The jets of blazars are renowned for their multi-wavelength flares and rapid extreme variability; however, there are still some important unanswered questions about the physical processes responsible for these spectral and temporal changes in emissio
n properties. In this paper, we develop a time-dependent particle evolution model for the time-varying emission spectrum of blazars. In the model, we introduce time-dependent electric and magnetic fields, which consistently include the variability of relevant physical quantities in the transport equation. The evolution on the electron distribution is numerically solved from a generalized transport equation that contains the terms describing the electrostatic, first-order and second-order emph{Fermi} acceleration, escape of particles due to both advection and spatial diffusion, as well as energy losses due to the synchrotron emission and inverse-Compton scattering of both synchrotron and external ambient photon fields. We find that the light curve profiles of blazars are consistent with the particle spectral evolution resulting from time-dependent electric and magnetic fields, rather than the effects of the acceleration or the cooling processes. The proposed model is able to simultaneously account for the variability of both the energy spectrum and the light curve profile of the BL Lac object Mrk 421 with reasonable assumptions about the physical parameters. The results strongly indicate that the magnetic field evolution in the dissipated region of a blazar jet can account for the variabilities.
Electrons are accelerated at the shock wave diffuse and advect outward, and subsequently drift away into the emitting region of the jet that is located in the downstream flow from the plane shock. The current work considers the acceleration of the el
ectrons in the shock front. Assuming a proper boundary condition at the interface between the shock and the downstream zones, a novel particle distribution in the downstream flow is proposed in this work to reproduce the broadband spectral energy distribution of BL Lac objects. We find that (1) we can obtain the particle distribution downstream of the shock wave in four cases; (2) electrons with higher energy ($gamma>gamma_{0}$) dominate the emission spectrum; (3) the distinctly important physical parameters assumed in our model can reasonably reproduce the multi-wavelength spectrum of the high-synchrotron-peaked BL Lac object Markarian 421 (Mrk 421).
We develop an algorithmic framework for graph colouring that reduces the problem to verifying a local probabilistic property of the independent sets. With this we give, for any fixed $kge 3$ and $varepsilon>0$, a randomised polynomial-time algorith
m for colouring graphs of maximum degree $Delta$ in which each vertex is contained in at most $t$ copies of a cycle of length $k$, where $1/2le tle Delta^frac{2varepsilon}{1+2varepsilon}/(logDelta)^2$, with $lfloor(1+varepsilon)Delta/log(Delta/sqrt t)rfloor$ colours. This generalises and improves upon several notable results including those of Kim (1995) and Alon, Krivelevich and Sudakov (1999), and more recent ones of Molloy (2019) and Achlioptas, Iliopoulos and Sinclair (2019). This bound on the chromatic number is tight up to an asymptotic factor $2$ and it coincides with a famous algorithmic barrier to colouring random graphs.
The first author together with Jenssen, Perkins and Roberts (2017) recently showed how local properties of the hard-core model on triangle-free graphs guarantee the existence of large independent sets, of size matching the best-known asymptotics due
to Shearer (1983). The present work strengthens this in two ways: first, by guaranteeing stronger graph structure in terms of colourings through applications of the Lovasz local lemma; and second, by extending beyond triangle-free graphs in terms of local sparsity, treating for example graphs of bounded local edge density, of bounded local Hall ratio, and of bounded clique number. This generalises and improves upon much other earlier work, including that of Shearer (1995), Alon (1996) and Alon, Krivelevich and Sudakov (1999), and more recent results of Molloy (2019), Bernshteyn (2019) and Achlioptas, Iliopoulos and Sinclair (2019). Our results derive from a common framework built around the hard-core model. It pivots on a property we call local occupancy, giving a clean separation between the methods for deriving graph structure with probabilistic information and verifying the requisite probabilistic information itself.
There are still some important unanswered questions about the detailed particle acceleration and escape occurring during the quiescent epoches. As a result, the particle distribution that is adopted in the blazar quiescent spectral model have numerou
s unconstrained shapes. To help remedy this problem, we introduce a analytical particle transport model to reproduce quiescent broadband spectral energy distribution of blazar. In this model, the exact electron distribution is solved from a generalized transport equation that contains the terms describing first-order and secondary-order emph{Fermi} acceleration, escape of particle due to both the advection and spatial diffusion, energy losses due to synchrotron emission and inverse-Compton scattering of an assumed soft photon field. We suggest that the advection is a significant escape mechanism in blazar jet. We find that in our model the advection process tends to harden the particle distribution, which enhances the high energy components of resulting synchrotron and synchrotron self-Comptom spectrum from jet. Our model is able to roughly reproduce the observed spectra of extreme BL Lac object 1ES 0414+009 with reasonable assumptions about the physical parameters.
Given $varepsilon>0$, there exists $f_0$ such that, if $f_0 le f le Delta^2+1$, then for any graph $G$ on $n$ vertices of maximum degree $Delta$ in which the neighbourhood of every vertex in $G$ spans at most $Delta^2/f$ edges, (i) an independent set
of $G$ drawn uniformly at random has at least $(1/2-varepsilon)(n/Delta)log f$ vertices in expectation, and (ii) the fractional chromatic number of $G$ is at most $(2+varepsilon)Delta/log f$. These bounds cannot in general be improved by more than a factor $2$ asymptotically. One may view these as strong
We report the results of searches for solar axions and galactic dark matter axions or axion-like particles with CDEX-1 experiment at the China Jinping Underground Laboratory, using 335.6 kg-days of data from a p-type point-contact germanium detector.
The data are compatible with the background model and no excess signals are observed. Limits of solar axions on the model independent coupling $g_{Ae}<2.5times10^{-11}$ from Compton, bremsstrahlung, atomic-recombination and deexcitation channel and $g^{text{eff}}_{AN}times g_{Ae}<6.1times10^{-17}$ from $^{57}$Fe M1 transition at 90 % confidence level are derived. Within the framework of the DFSZ and KSVZ models, our results exclude the axion mass heavier than 0.9 eV/c$^{2}$ and 173 eV/c$^{2}$, respectively. The derived constraints for dark matter axions below 1 keV improves over the previous results.
The CDEX-1 experiment conducted a search of low-mass (< 10 GeV/c2) Weakly Interacting Massive Particles (WIMPs) dark matter at the China Jinping Underground Laboratory using a p-type point-contact germanium detector with a fiducial mass of 915 g at a
physics analysis threshold of 475 eVee. We report the hardware set-up, detector characterization, data acquisition and analysis procedures of this experiment. No excess of unidentified events are observed after subtraction of known background. Using 335.6 kg-days of data, exclusion constraints on the WIMP-nucleon spin-independent and spin-dependent couplings are derived.
