arXiv subjects

Hongshi Zong

Publications and source records attributed to Hongshi Zong.

27 records · Page 2Linked to original sources

arXiv2013

The contribution of ultracompact dark matter minihalos to the isotropic radio background

The ultracompact minihalos could be formed during the earlier epoch of the universe. The dark matter annihilation within them is very strong due to the steep density profile, $ρ\sim r^{-2.25}$. The high energy electrons and positrons from the dark matter annihilation can inverse Compton scatter (ICS) with the background photons, such as CMB photons, to acquire higher energy. On the other hand, the synchrotron radiation can also be produced when they meet the magnetic field. In this paper, we study the signals from the UCMHs due to the dark matter annihilation for the radio, X-ray and $γ$-ray band. We found that for the radio emission the UCMHs can provide one kind of source for the radio excess observed by ARCADE 2. But the X-ray signals due to the ICS effect or the $γ$-ray signals mainly due to the prompt emission from dark matter would exceed the present observations, such as Fermi, COMPTEL and CHANDRA. We found that the strongest limits on the fraction of UCMHs come from the X-ray observations and the constraints from the radio data are the weakest.

astro-ph.HE↗

arXiv2013

Dark Matter Decay and the Abundance of Ultracompact Minihalos

Ultracompact minihalos would be formed if there are larger density perturbations ($0.0003 < δρ/ρ< 0.3$) in the earlier epoch. The density profile of them is steeper than the standard dark matter halos. If the dark matter can annihilate or decay into the standard particles, e.g., photons, these objects would be the potential astrophysical sources. In order to be consistent with the observations, such as $Fermi$, the abundance of ultracompact minihalos must be constrained. On the other hand, the formation of these objects has very tight relation with the primordial curvature perturbations on smaller scale, so the fraction of ultracompact minihalos is very important for modern cosmology. In previous works, the studies are focused on the dark matter annihilation for these objects. But if the dark matter is not annihilated, the dark matter decay is another important possible case. On the other hand, the abundance of ultracompact minihalos is related to many other parameters, such as the mass of dark matter, the decay channels and the density profile of dark matter halo. One of the important aspects of this work is that we investigate the $γ$-ray signals from nearby ultracompact minihalos due to dark matter decay and another important aspect is to study in detail how the different decay channels and density profiles affect the constraints on the abundance of ultracompact minihalos.

astro-ph.CO↗

arXiv2012

Connecting neutron star observations to the high density equation of state of quasi-particle model

The observation of $1.97\pm0.04$ solar-mass neutron-like star gives constraint on the equation of state (EOS) of cold, condensed matter. In this paper, the EOS for both pure quark star and hybrid star with a quark core described by quasi-particle model are considered. The parameters of quasi-particle model which affect the mass of both quark star and hybrid star can be constrained by the observation.

astro-ph.HE↗

arXiv2011

Constraints on ultracompact minihalos from extragalactic γ-ray background

It has been proposed that ultracompact minihalos (UCMHs) might be formed in earlier epoch. If dark matter consists of Weakly Interacting Massive Particles (WIMPs), UCMHs can be treated as the γ-ray sources due to dark matter annihilation within them. In this paper, we investigate the contributions of UCMHs formed during three phase transi- tions (i.e., electroweak symmetry breaking, QCD confinement and e+ e- annihilation) to the extragalactic γ-ray background. Moreover, we use the Fermi-LAT observation data of the extragalactic γ-ray background to get the constraints on the current abundance of UCMHs produced during these phase transitions. We also compare these results with those obtained from Cosmic Microwave Background (CMB) observations and find that the constraints from the Fermi-LAT are more stringent than those from CMB

astro-ph.CO↗

arXiv2011

The Abundance of New Kind of Dark Matter Structures

A new kind of dark matter structures, ultracompact minihalos (UCMHs) was proposed recently. They would be formed during the radiation dominated epoch if the large density perturbations are existent. Moreover, if the dark matter is made up of weakly interacting massive particles, the UCMHs can have effect on cosmological evolution because of the high density and dark matter annihilation within them. In this paper, one new parameter is introduced to consider the contributions of UCMHs due to the dark matter annihilation to the evolution of cosmology, and we use the current and future CMB observations to obtain the constraint on the new parameter and then the abundance of UCMHs. The final results are applicable for a wider range of dark matter parameters

astro-ph.HE↗

arXiv2011

New Constraints on Primordial Minihalo Abundance Using Cosmic Microwave Background Observations

It was proposed that the massive compact halo objects (MCHOs) would be produced during an earlier epoch of cosmology if the density perturbations are between $3 \times 10^{-4}$ and 0.3. Then these objects can accrete dark matter particles onto them due to their high density. If the dark matter is in the form of the weakly interacting massive particles, the MCHOs can have a significant effect on the evolution of cosmology due to the dark matter annihilation within them. Using the WMAP-7 years data, we investigated the constraints on the current abundance of MCHOs ($f_{MCHOs}$) formed during the $e^{+} e^{-}$ annihilation phase transition. We have found that the $2σ$ constraint is $f_{MCHOs} \lesssim 10^{-4}$ for dark matter masses in the range between 1 GeV and 1 TeV.

astro-ph.CO↗

arXiv2001

Tensor susceptibility of the QCD vacuum from an effective quark-quark interaction

Treating the bilocal quark-quark interaction kernel as an input parameter, the self-energy functions can be determined from the ``rainbow'' Dyson-Schwinger equation, which is obtained in the global color symmetry model. The tensor susceptibility of QCD vacuum can be calculated directly from these self-energy functions. The values we obtained are much smaller than the estimations from QCD sum rules and from chiral constituent quark model.

hep-ph↗

arXiv2001

A New Approach to the Calculation of Some Properties of Vacuum and $π$ and $σ$ Mesons

It is shown in a systematic way that the instanton dilute model can be combined with the global colour symmetry model to form a new nonperturbative QCD model. Based on the quark propagator derived in the instanton dilute liquid approximation, the quark condensate $<\bar{q}q>$, the mixed quark gluon condensate $g_{s}<\bar{q}G_{μν}σ^{μν}q>$, the four quark condensate $<|bar{q}Γq\bar{q}Γq>$ and tensor, pion vacuum susceptibilities have been calculated at the mean field level in the framework of the new nonperturbative QCD model. The numerical results are compatible with the values obtained within other nonperturbative approaches. The calculated masses and decay constants of $π$ and $σ$ mesons are also close to the experimental values.

hep-ph↗

arXiv1999

Statistical Properties of Charmonium Spectrum and a New Mechanism of J/ψSuppression

The statistical properties of Charmonium energy spectrum determined by the Bethe-Salpeter equation are investigated. It is found that the regular motion of the $c\bar{c}$ system can be expected at a small value of color screening mass but the chaotic motion at a large one. It is shown that the level mixing due to color screening serves as a new mechanism resulting in the J/$ψ$ suppression. Moreover, this kind of suppression can occur before the color screening mass reaches its critical value for J/$ψ$ dissociation. It implies that a strong J/$ψ$ suppression is possible in the absence of dissociation of J/$ψ$.

nucl-th↗