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Miao Li

Publications and source records attributed to Miao Li.

At least 145 records · Page 8Linked to original sources
arXiv2019

Measuring the speed of gravitational waves with the distorted pulsars

The measurement of the speed of gravitational waves (GWs) is useful to distinguish general relativity from massive gravity. We propose a new model-independent strategy to measure the speed of GWs with the distorted pulsars. Theoretically, when the the GW frequencies from a distorted pulsar are twice the frequencies of EM pulses, they should be emitted at the same time. By measuring the arrival times of these two signals emitted at the same time, the speed of GWs can be calculated with the time difference. Specifically, when the glitches of pulsars are taken into consideration, some pulsars in our Galaxy and nearby galaxies are potential to test our new strategy at high accuracy in the foreseeable future. On the other hand, the new method is meaningful as a motivation for future design of instruments.

astro-ph.HE↗
arXiv2019

The redshift dependence of Alcock-Paczynski effect: cosmological constraints from the current and next generation observations

The tomographic Alcock-Paczynski (AP) test is a robust large-scale structure (LSS) measurement that receives little contamination from the redshift space distortion (RSD). It has placed tight cosmological constraints by using small and intermediate clustering scales of the LSS data. However, previous works have neglected the cross-correlation among different redshift bins, which could cause the statistical uncertainty being underestimated by $\sim$20\%. In this work, we further improve this method by including this multi-redshifts full correlation. We apply it to the SDSS DR12 galaxies sample and find out that, for $Λ$CDM, the combination of AP with the Planck+BAO dataset slightly reduces (within 1-$σ$) $Ω_m$ to $0.304\pm0.007$ (68.3\% CL). This then leads to a larger $H_0$ and also mildly affects $Ω_b h^2$, $n_s$ and the derived parameters $z_*$, $r_*$, $z_{re}$ but not $τ$, $A_s$ and $σ_8$. For the flat $w$CDM model, our measurement gives $Ω_m=0.301\pm 0.010$ and $w=-1.090\pm 0.047$, where the additional AP measurement reduces the error budget by $\sim 25\%$. When including more parameters into the analysis, the AP method also improves the constraints on $Ω_k$, $\sum m_μ$, $N_{\rm eff}$ by $20-30\%$. Early universe parameters such as $dn_s/d{\rm ln}k$ and $r$, however, are unaffected. Assuming the dark energy equation of state $w=w_0+w_a \frac{z}{1+z}$, the Planck+BAO+SNIa+$H_0$+AP datasets prefer a dynamical dark energy at $\approx1.5 σ$ CL. Finally, we forecast the cosmological constraints expected from the DESI galaxy survey and find that combining AP with CMB+BAO method would improve the $w_0$-$w_a$ constraint by a factor of $\sim 10$.

astro-ph.CO↗
arXiv2019

Simulating Gas Inflow at the Disk-Halo Interface

The interaction between inflowing gas clouds and galactic outflows at the interface where the galactic disk transitions into the circumgalactic medium is an important process in galaxy fueling, yet remains poorly understood. Using a series of tall-box hydrodynamic ENZO simulations, we have studied the interaction between smooth gas inflow and supernovae-driven outflow at the disk-halo interface with pc-scale resolution. A realistic wind of outflowing material is generated by supernovae explosions in the disk, while inflowing gas is injected at the top boundary of the simulation box with an injection velocity ranging from $10-100 \rm \ km \ s^{-1}$. We find that cooling and hydrodynamic instabilities drive the injected gas to fragment into cold ($\sim 10^{3}$ K) cloud clumps with typical densities of $\sim 1 \rm \ cm^{-3}$. These clumps initially accelerate before interacting and partially mixing with the outflow and decelerating to velocities in the 50-100 $\rm km \ s^{-1}$ range. When the gas clumps hit the disk, $10\%-50 \%$ of the injected material is able to accrete (depending on the injection velocity). Clumps originating from gas injected with a higher initial velocity approach the disk with greater ram pressure, allowing them to penetrate through the disk in low density regions. We use (equilibrium) CLOUDY photoionization models to generate absorption and emission signatures of gas accretion, finding that our mock HI and H$α$ observables are prominent and generally consistent with measurements in the Milky Way. We do not predict enhanced emission/absorption for higher ionization states such as OVI.

astro-ph.GA↗
arXiv2019

Local well-posedness of semilinear space-time fractional Schrödinger equation

The semilinear space-time fractional Schrödinger equation is considered. First, we give the explicit form for the fundamental solutions by using the Fox $H$-functions in order to to establish some $L^s$ decay estimates. After that, we give some space-time estimates for the mild solutions from which the local well-posedness is derived on some proper Banach space.

math.AP↗
arXiv2018

Exploring cooperative game mechanisms of scientific coauthorship networks

Scientific coauthorship, generated by collaborations and competitions among researchers, reflects effective organizations of human resources. Researchers, their expected benefits through collaborations, and their cooperative costs constitute the elements of a game. Hence we propose a cooperative game model to explore the evolution mechanisms of scientific coauthorship networks. The model generates geometric hypergraphs, where the costs are modelled by space distances, and the benefits are expressed by node reputations, i. e. geometric zones that depend on node position in space and time. Modelled cooperative strategies conditioned on positive benefit-minus-cost reflect the spatial reciprocity principle in collaborations, and generate high clustering and degree assortativity, two typical features of coauthorship networks. Modelled reputations generate the generalized Poisson parts and fat tails appeared in specific distributions of empirical data, e. g. paper team size distribution. The combined effect of modelled costs and reputations reproduces the transitions emerged in degree distribution, in the correlation between degree and local clustering coefficient, etc. The model provides an example of how individual strategies induce network complexity, as well as an application of game theory to social affiliation networks.

physics.soc-ph↗
arXiv2018

Massive black hole and Population III galaxy formation in over-massive dark matter halos with violent merger histories

We propose the formation of massive pristine dark-matter (DM) halos with masses of $\sim 10^8~M_\odot$, due to the dynamical effects of frequent mergers in rare regions of the Universe with high baryonic streaming velocity relative to DM. Since the streaming motion prevents gas collapse into DM halos and delays prior star formation episodes, the gas remains metal-free until the halo virial temperatures $\gtrsim 2\times 10^4~{\rm K}$. The minimum cooling mass of DM halos is boosted by a factor of $\sim 10-30$ because frequent major mergers of halos further inhibit gas collapse. We use Monte Carlo merger trees to simulate the DM assembly history under a streaming velocity of twice the root-mean-square value, and estimate the number density of massive DM halos containing pristine gas as $\simeq 10^{-4}~{\rm cMpc}^{-3}$. When the gas infall begins, efficient Ly$α$ cooling drives cold streams penetrating inside the halo and feeding a central galactic disk. When one stream collides with the disk, strong shock forms a dense and hot gas cloud, where the gas never forms H$_2$ molecules due to effective collisional dissociation. As a result, a massive gas cloud forms by gravitational instability and collapses directly into a massive black hole (BH) with $M_\bullet \sim 10^5~M_\odot$. Almost simultaneously, a galaxy with $M_{\star, \rm tot}\sim 10^6~M_\odot$ composed of Population III stars forms in the nuclear region. If the typical stellar mass is as high as $\sim 100~M_\odot$, the galaxy could be detected with the James Webb Space Telescope even at $z\gtrsim 15$. These massive seed BHs would be fed by continuous gas accretion from the host galaxy, and grow to be bright quasars observed at $z\gtrsim 6$.

astro-ph.GA↗
arXiv2018

Kozai-Lidov Mechanism inside Retrograde Mean Motion Resonances

As the discoveries of more minor bodies in retrograde resonances with giant planets, such as 2015 BZ509 and 2006 RJ2, our curiosity about the Kozai-Lidov dynamics inside the retrograde resonance has been sparked. In this study, we focus on the 3D retrograde resonance problem and investigate how the resonant dynamics of a minor body impacts on its own Kozai-Lidov cycle. Firstly we deduce the action-angle variables and canonical transformations that deal with the retrograde orbit specifically. After obtaining the dominant Hamiltonian of this problem, we then carry out the numerical averaging process in closed form to generate phase-space portraits on a $e-ω$ space. The retrograde 1:1 resonance is particularly scrutinized in detail, and numerical results from a CRTBP model shows a great agreement with the our semi-analytical portraits. On this basis, we inspect two real minor bodies currently trapped in retrograde 1:1 mean motion resonance. It is shown that they have different Kozai-Lidov states, which can be used to analyze the stability of their unique resonances. In the end, we further inspect the Kozai-Lidov dynamics inside the 2:1 and 2:5 retrograde resonance, and find distinct dynamical bifurcations of equilibrium points on phase-space portraits.

astro-ph.EP↗
arXiv2018

Inverses of generators of integrated fractional resolvent operator functions

This paper is devoted to the inverse generator problem in the setting of generators of integrated resolvent operator functions. It is shown that if the operator $A$ is the generator of a tempered $β$-times integrated $α$-resolvent operator function ($(α,β)$-ROF) and it is injective, then the inverse operator $A^{-1}$ is the generator of a tempered $(α,γ)$-ROF for all $γ> β+1/2,$ by means of an explicit representation of the integrated resolvent operator function based in Bessel functions of first kind. Analytic resolvent operator functions are also considered, showing that $A^{-1}$ is in addition the generator of a tempered $(δ,0)$-ROF for all $δ<α.$ Moreover, the optimal decay rate of $(α,β)$-ROFs as $t\to \infty$ is given. These result are applied to fractional Cauchy problem unsolved in the fractional derivative.

math.FA↗
arXiv2018

The fractional d'Alembert's formulas

In this paper we develop generalized d'Alembert's formulas for abstract fractional integro-differential equations and fractional differential equations on Banach spaces. Some examples are given to illustrate our abstract results, and the probability interpretation of these fractional d'Alembert's formulas are also given. Moreover, we also provide d'Alembert's formulas for abstract fractional telegraph equations.

math.FA↗
arXiv2018

Centaurs potentially in retrograde co-orbit resonance with Saturn

Aims. 2015 BZ509 is the first asteroid confirmed to be in retrograde co-orbit resonance (or 1/-1 resonance) with the giant planets in the solar system. While Saturn is the only giant planet whose Trojans are not discovered until now, we identify some small bodies among Centaurs and Damocloids that are potentially in 1/-1 resonance with Saturn in the present study. Methods. We integrate numerically the motion of the 1000 clones (include the nominal orbit) of each Centaur whose orbit has a semi-major axis between 9.3 au and 9.8 au and an inclination i > 90 deg. To confirm and evaluate the 1/-1 resonant configurations mentioned above, we introduce a useful one-degree integrable approximation for planar 1/-1 resonance. Results. We identify four candidates potentially in 1/-1 resonance with Saturn. The capture in this particular resonant state during the 40000 yr integration timespan is very common for 2006 RJ2 (906/1000 clones), 2006 BZ8 (878/1000 clones), and 2017 SV13 (998/1000 clones), and it is less likely for 2012 YE8 (426/1000 clones). According to our statistical results, 2006 RJ2 is the best candidate to be currently in a 1/-1 mean motion resonance with Saturn, and 2017 SV13 is another important potential candidate. Moreover, 2012 YE8 and 2006 BZ8 are also Centaurs of interest but their current and long-term 1/-1 resonant state with Saturn is less likely. The proportions of the clones captured in the relative long-term stable co-orbit resonance (over 10000 yr) are also given. Conclusions. Small bodies in retrograde co-orbit resonance with giant planets may be more common than previously expected. Identification of these potential mysterious minor bodies encourages the search for such objects on a larger scale in our solar system. The findings of this paper are also useful for understanding the origin and dynamical evolution of the Centaurs and Damocloids on retrograde orbits.

astro-ph.EP↗
arXiv2018

Gravitational waves induced by the asymmetric jets of gamma-ray bursts

We study the gravitational wave (GW) production induced by the asymmetric jets of gamma-ray bursts (GRBs). The asymmetric jets result in a recoil force acted on the central compact object, whose motion leads to emission of GW. Under reasonable assumptions and simplifications, we derive the analytic form of the produce GWs. The amplitude of emitted GWs is estimated to be relatively low, but possibility exists that they can be detected by future experiments such as the Einstein Telescope. We find the dynamical properties of the central object, which is difficult to be studied via the electromagnetic (EW) channel, can be inferred by measuring the emitted GWs. Moreover, we find the emitted GWs can be used determine whether the relativistic jets is launched by the neutrino annihilation process or the Blandford-Znajek process, which cannot be clearly distinguished by the current GRB observations. Our work manifests the importance of the GW channel in multi-messenger astronomy. The physical information encoded in the GW and EW emissions of an astrophysical object is complementary to each other; in case some physics can not be effectively investigated using the EW channel alone, including the GW channel can be very helpful.

astro-ph.HE↗
arXiv2018

Dynamic portrait of the retrograde 1:1 mean motion resonance

Asteroids in mean motion resonances with giant planets are common in the solar system, but it was not until recently that several asteroids in retrograde mean motion resonances with Jupiter and Saturn were discovered. A retrograde co-orbital asteroid of Jupiter, 2015 BZ509 is confirmed to be in a long-term stable retrograde 1:1 mean motion resonance with Jupiter, which gives rise to our interests in its unique resonant dynamics. In this paper, we investigate the phase-space structure of the retrograde 1:1 resonance in detail within the framework of the circular restricted three-body problem. We construct a simple integrable approximation for the planar retrograde resonance using canonical contact transformation and numerically employ the averaging procedure in closed form. The phase portrait of the retrograde 1:1 resonance is depicted with the level curves of the averaged Hamiltonian. We thoroughly analyze all possible librations in the co-orbital region and uncover a new apocentric libration for the retrograde 1:1 resonance inside the planet's orbit. We also observe the significant jumps in orbital elements for outer and inner apocentric librations, which are caused by close encounters with the perturber.

astro-ph.EP↗
arXiv2018

Satellite capture mechanism in a sun-planet-binary four-body system

This paper studies the binary disruption problem and asteroid capture mechanism in a sun-planet-binary four-body system. Firstly, the binary disruption condition is studied and the result shows that the binary is always disrupted at the perigee of their orbit instantaneously. Secondly, an analytic expression to describe the energy exchange between the binary is derived based on the instantaneous disruption hypothesis. The analytic result is validated through numerical integration. We obtain the energy exchange in encounters simultaneously by the analytic expression and numerical integration. The maximum deviation of this two results is always less than 25% and the mean deviation is about 8.69%. The analytic expression can give us an intuitive description of the energy exchange between the binary. It indicates that the energy change depends on the hyperbolic shape of the binary orbit with respect to the planet, the masses of planet and the primary member of the binary, the binary phase at perigee. We can illustrate the capture/escape processes and give the capture/escape region of the binary clearly by numerical simulation. We analyse the influence of some critical factors to the capture region finally.

nlin.CD↗
arXiv2018

Feature analysis of multidisciplinary scientific collaboration patterns based on PNAS

The features of collaboration patterns are often considered to be different from discipline to discipline. Meanwhile, collaborating among disciplines is an obvious feature emerged in modern scientific research, which incubates several interdisciplines. The features of collaborations in and among the disciplines of biological, physical and social sciences are analyzed based on 52,803 papers published in a multidisciplinary journal PNAS during 1999 to 2013. From those data, we found similar transitivity and assortativity of collaboration patterns as well as the identical distribution type of collaborators per author and that of papers per author, namely a mixture of generalized Poisson and power-law distributions. In addition, we found that interdisciplinary research is undertaken by a considerable fraction of authors, not just those with many collaborators or those with many papers. This case study provides a window for understanding aspects of multidisciplinary and interdisciplinary collaboration patterns.

physics.soc-ph↗
arXiv2018

Continuum Reverberation Mapping of the Accretion Disks in Two Seyfert 1 Galaxies

We present optical continuum lags for two Seyfert 1 galaxies, MCG+08-11-011 and NGC 2617, using monitoring data from a reverberation mapping campaign carried out in 2014. Our light curves span the ugriz filters over four months, with median cadences of 1.0 and 0.6 days for MCG+08-11-011 and NGC\,2617, respectively, combined with roughly daily X-ray and near-UV data from Swift for NGC 2617. We find lags consistent with geometrically thin accretion-disk models that predict a lag-wavelength relation of $τ\propto λ^{4/3}$. However, the observed lags are larger than predictions based on standard thin-disk theory by factors of 3.3 for MCG+08-11-011 and 2.3 for NGC\,2617. These differences can be explained if the mass accretion rates are larger than inferred from the optical luminosity by a factor of 4.3 in MCG+08-11-011 and a factor of 1.3 in NGC\,2617, although uncertainty in the SMBH masses determines the significance of this result. While the X-ray variability in NGC\,2617 precedes the UV/optical variability, the long 2.6 day lag is problematic for coronal reprocessing models.

astro-ph.GA↗
arXiv2018

A Planar Tracking Game with Sensing Delays and its MATLAB Implementation

This paper proposes a new perspective on the conventional planar target tracking problem. One evader and one pursuer are considered in the dynamics. In the planar tracking, pursuer has the ability to measure the position and the velocity information of the evader but with sensing delays. The modeling and the controller design of the system are presented with details. Then, a computer game is developed and implemented using MATLAB/Simulink, which constitutes the main contribution of the paper.

eess.SY↗
arXiv2017

Reverberation Mapping of Optical Emission Lines in Five Active Galaxies

We present the first results from an optical reverberation mapping campaign executed in 2014, targeting the active galactic nuclei (AGN) MCG+08-11-011, NGC 2617, NGC 4051, 3C 382, and Mrk 374. Our targets have diverse and interesting observational properties, including a "changing look" AGN and a broad-line radio galaxy. Based on continuum-H$β$ lags, we measure black hole masses for all five targets. We also obtain H$γ$ and He{\sc ii}\,$λ4686$ lags for all objects except 3C 382. The He{\sc ii}\,$λ4686$ lags indicate radial stratification of the BLR, and the masses derived from different emission lines are in general agreement. The relative responsivities of these lines are also in qualitative agreement with photoionization models. These spectra have extremely high signal-to-noise ratios (100--300 per pixel) and there are excellent prospects for obtaining velocity-resolved reverberation signatures.

astro-ph.GA↗