arXiv subjects
Publications and source records attributed to Bo Liu.
Measurements of the X(3872) mass, $ψ(2S)$ production cross-section and $χ_{c2}/χ_{c1}$ production ratio using around 35$\rm pb^{-1}$ of pp collision data at $\sqrt{s}$ = 7 TeV during the 2010 LHC running period with the LHCb detector are presented.
There are mutually contradictory views in the literature of the kinematics and structure of high-ionization line (e.g. CIV) emitting regions in active galactic nuclei (AGNs). Two kinds of broad emission line region (BELR) models have been proposed, outflow and gravitationally bound BELR, which are supported respectively by blueshift of the CIV line and reverberation mapping observations. To reconcile these two apparently different models, we present a detailed comparison study between the CIV and MgII lines using a sample of AGNs selected from the Sloan Digital Sky Survey. We find that the kinematics of the CIV region is different from that of MgII, which is thought to be controlled by gravity. A strong correlation is found between the blueshift and asymmetry of the CIV profile and the Eddington ratio. This provides strong observational support for the postulation that the outflow is driven by radiation pressure. In particular, we find robust evidence that the CIV line region is largely dominated by outflow at high Eddington ratios, while it is primarily gravitationally bounded at low Eddington ratios. Our results indicate that these two emitting regions coexist in most of AGNs. The emission strength from these two gases varies smoothly with Eddington ratio in opposite ways. This explanation naturally reconciles the apparently contradictory views proposed in previous studies. Finally, candidate models are discussed which can account for both, the enhancement of outflow emission and suppression of normal BEL, in AGN with high Eddington ratios.
In this paper, we first establish an $S^1$-equivariant index theorem for Spin$^c$ Dirac operators on $\mathbb{Z}/k$ manifolds, then combining with the methods developed by Taubes \cite{MR998662} and Liu-Ma-Zhang \cite{MR1870666,MR2016198}, we extend Witten's rigidity theorem to the case of $\mathbb{Z}/k$ Spin$^c$ manifolds. Among others, our results resolve a conjecture of Devoto \cite{MR1405063}
We present an explicit expression of the anomaly formula for the Cappell-Miller holomorphic torsion for Kähler manifolds.
The quotient complexity, also known as state complexity, of a regular language is the number of distinct left quotients of the language. The quotient complexity of an operation is the maximal quotient complexity of the language resulting from the operation, as a function of the quotient complexities of the operands. The class of star-free languages is the smallest class containing the finite languages and closed under boolean operations and concatenation. We prove that the tight bounds on the quotient complexities of union, intersection, difference, symmetric difference, concatenation, and star for star-free languages are the same as those for regular languages, with some small exceptions, whereas the bound for reversal is 2^n-1.
We combine recent long Gamma Ray Bursts (GRBs) sample including 52 objects out to z$=$6.3 compiled from Swift Gamma Ray Bursts by Schaefer (2006) with Type Ia Supernova (SNIa), Cosmic Microwave Background (CMB) and Baryon Oscillation (BAO) to constrain cosmologies. We study the constraints arising from GRBs alone and the complementarity of GRBs to other cosmological probes. To analyze the cosmological role of GRBs, we adopt the Hubble constant as a free parameter with a prior in the range of $H_0=72\pm8\enspace\kmsmpc$ instead of a fixed $H_0$ used in previous studies. By jointly using SNIa gold/SNLS samples and GRBs, the constraints on \Om -\Ol parameter space are dramatically improved in comparing with those from SNIa data alone. The complementarity of GRBs is mostly from the sub-sample with z$>$1.5 due to the different parameter degeneracies involved in luminosity distances at different redshifts. Including GRB data in addition to SNIa, BAO and CMB in our analysis, we find that the concordance model with \Om $\sim$0.3 and \Ol$\sim$0.7 is still well within 1$σ$ confidence range.
By concern of compression of charge density field, the corrected Lorentz force formula and consequent inference is presented. And further radiation frequency property of an individual charge density field in magnetic dipole is analyzed respectively for radiant property of the charged particle and the emitted electromagnetic wave transfer property between the moving radiant source and observer. As results, the behavior and radiation frequency property of the electron beam in magnetic dipole is interpreted upon the individual's behavior and property. At final, the potential application is put forward for wider interest.
Within Kirkwood theory, we study the translational diffusion coefficient of a single polymer chain in dilute solution, and focus on the small difference between the short--time Kirkwood value $D^{(K)}$ and the asymptotic long--time value $D$. We calculate this correction term by highly accurate large--scale Brownian Dynamics simulations, and show that it is in perfect agreement with the rigorous variational result $D < D^{(K)}$, and with Fixman's Green--Kubo formula, which is re--derived. This resolves the puzzle posed by earlier numerical results (Rey {\em et al.}, Macromolecules 24, 4666 (1991)), which rather seemed to indicate $D > D^{(K)}$; the older data are shown to have insufficient statistical accuracy to resolve this question. We then discuss the Green--Kubo integrand in some detail. This function behaves very differently for pre--averaged vs. fluctuating hydrodynamics, as shown for the initial value by analytical considerations corroborated by numerical results. We also present further numerical data on the chain's statics and dynamics.