arXiv subjects

Chunhua Li

Publications and source records attributed to Chunhua Li.

27 records · Page 2Linked to original sources

arXiv2016

Alignment and measurement of the magnetic field for the BESIII muon counter

Based on cosmic ray events without a magnetic field taken with the BESIII detector during the summer shutdown of BEPCII in 2012 and di-muon events from a data sample taken at center-of-mass energy of 3.686 GeV in 2009, we compare the coordinates of hits registered in the BESIII muon counter with the expected interaction point extrapolated from reconstructed tracks from the inner tracking system in the absence of a magnetic field. By minimizing the difference, we align the muon counter with the inner tracking system. Moreover, the strength of the magnetic field in the muon counter is measured for the first time with di-muon events from data taken at a center-of-mass energy of 3.686~GeV. After the alignment and the magnetic field strength measurement, the offsets in the reconstructed hit positions for muon tracks are reduced, which improves the muon identification. The alignment and magnetic field strength measurement have been adopted in the latest version of the BESIII offline software system. This addition to the software reduces the systematic uncertainty for the physics analysis in cases where the muon counter information is used.

physics.ins-det↗

arXiv2016

Remarks on derivative nonlinear Schrödinger systems with multiple masses

We prove global existence of small solutions to the initial value problem for a class of cubic derivative nonlinear Schrödinger systems with the masses satisfying suitable non-resonance relations. The large-time asymptotics of the solutions are also shown. This work is intended to provide a counterpart of the previous paper (arXiv:1507.07617) in which the mass resonance case was treated.

math.AP↗

arXiv2015

Computational Studies about the Interactions of Nanomaterials with Proteins and their Impacts

Intensive concerns about the biosafety of nanomaterials demand the systematic study of the mechanisms about their biological effects. Many biological effects can be attributed to the interaction of nanomaterials with protein and their impacts on protein function. On the other hand, nanomaterials exhibit the potential in a variety of biomedical applications, many of which also involve the direct interaction with protein. In this paper, we review some recent computational studies about this subject, especially the interaction of carbon and gold nanomaterials. Besides the hydrophobic and π-stacking interactions, the interaction mode of carbon nanomaterials can be regulated by their functional groups. And the coating of gold nanomaterials also adjusts their interaction mode, in addition to the coordination interaction with cysteine's sulfur group and histidine's imidazole group. Moreover, nanomaterials can interact with multiple proteins and the impacts on protein activity are attributed to a wide spectrum of mechanisms. The findings about the mechanisms of nanomaterial-protein interaction can further guide the design and development of nanomaterial to realize the applications in disease diagnosis and treatment.

physics.bio-ph↗

arXiv2015

On Schrödinger systems with cubic dissipative nonlinearities of derivative type

Consider the initial value problem for systems of cubic derivative nonlinear Schrödinger equations in one space dimension with the masses satisfying a suitable resonance relation. We give structural conditions on the nonlinearity under which the small data solution gains an additional logarithmic decay as $t \to +\infty$ compared with the corresponding free evolution.

math.AP↗

arXiv2014

Previous R&D of vibrating wire alignment technique for HEPS

The alignment tolerance of multipoles on a girder is better than 30um in the storage ring of High Energy Photon Source HEPS which will be the next project at IHEP Institute of High Energy Physics. This is difficult to meet the precision only using the traditional optical survey method. In order to achieve this goal, vibrating wire alignment technique with high precision and sensitivity is considered to be used in this project. This paper presents some previous research works about theory, scheme design and achievements.

physics.acc-ph↗

arXiv2013

A remark on decay rates of solutions for a system of quadratic nonlinear Schrödinger equations in 2D

We consider the initial value problem for a three-component system of quadratic nonlinear Schrödinger equations with mass resonance in two space dimensions. Under a suitable condition on the coefficients of the nonlinearity, we will show that the solution decays strictly faster than $O(t^{-1})$ as $t \to +\infty$ in $L^{\infty}$ by providing with an enhanced decay estimate of order $O((t \log t)^{-1})$. Differently from the previous works, our approach does not rely on the explicit form of the asymptotic profile of the solution at all.

math.AP↗

arXiv2011

Local Moment Formation of an Anderson Impurity on Graphene

We study the property of a magnetic impurity on a single-layer graphene within an Anderson impurity model. Due to the vanishing local density of states at the Fermi level in graphene, the impurity spin cannot be effectively screened out. Treating the problem within the Gutzwiller approximation, we found a region in the parameter space of $U$-$E^f$ where the impurity is in the local moment state, which is characterized by a zero effective hybridization between the bath electron and the magnetic impurity. Here $U$ is the onsite Coulomb repulsion of the impurity electrons and $E^f$ the impurity energy level. The competition between $U$ and $E^f$ is also discussed. While larger $U$ reduces double occupation and favors local moment formation, a deeper impurity level prefers double occupation and a nonzero hybridization and thus a Kondo screened state. For a fixed $U$, by continuously lowering the impurity level, the impurity first enters from a Kondo screened state into a local moment state and then departs from this state and re-enters into the Kondo screened state.

cond-mat.str-el↗

arXiv2009

Mott and Wigner-Mott transitions in doped correlated electron systems: effects of superlattice potential and inter-site correlation

We introduce the notion of superstructure Mottness to describe the Mott and Wigner-Mott transition in doped strongly correlated electron systems at commensurate filling fractions away from one electron per site. We show that superstructure Mottness emerges in an inhomogeneous electron system when the superstructure contains an odd number of electrons per supercell. We argue that superstructure Mottness exists even in the absence of translation symmetry breaking by a superlattice, provided that the extended or intersite Coulomb interaction is strong. In the latter case, superstructure Mottness offers a unifying framework for the Mott and Wigner physics and a nonperturbative, strong coupling description of the Wigner-Mott transition. We support our proposal by studying a minimal single-band ionic Hubbard $t$-$U$-$V$-$Δ$ model with nearest neighbor Coulomb repulsion $V$ and a two-sublattice ionic potential $Δ$. The model is mapped onto a Hubbard model with two effective ``orbitals'' representing the two sites within the supercell, the intra and interorbital Coulomb repulsion $U$ and $U^\prime \sim V$, and a crystal field splitting $Δ$. Charge order on the original lattice corresponds to orbital order. Developing a cluster Gutzwiller approximation, we study the effects and the interplay between $V$ and $Δ$ on the Mott and Wigner-Mott transitions at quarter-filling. We provide the mechanism by which the superlattice potential enhances the correlation effects and the tendency towards local moment formation, construct and elucidate the phase diagram in the unifying framework of superstructure Mottness.

cond-mat.str-el↗

arXiv2006

Inhomogeneous states with checkerboard order in the t-J Model

We study inhomogeneous states in the t-J model using an unrestricted Gutzwiller approximation. We find that $pa\times pa$ checkerboard order, where $p$ is a doping dependent number, emerges from Fermi surface instabilities of both the staggered flux phase and the Fermi liquid state with realistic band parameters. In both cases, the checkerboard order develops at wave vectors $(\pm 2π/pa,0)$, $(0,\pm2π/pa)$ that are tied to the peaks of the wave-vector dependent susceptibility, and is of the Lomer-Rice-Scott type. The properties of such periodic, inhomogeneous states are discussed in connection to the checkerboard patterns observed by STM in underdoped cuprates.

cond-mat.str-el↗