arXiv subjects

B. Wang

Publications and source records attributed to B. Wang.

142 records · Page 8Linked to original sources

arXiv2009

Localization in one-dimensional incommensurate lattices beyond the Aubry-André model

Localization properties of particles in one-dimensional incommensurate lattices without interaction are investigated with models beyond the tight-binding Aubry-André (AA) model. Based on a tight-binding t_1 - t_2 model with finite next-nearest-neighbor hopping t_2, we find the localization properties qualitatively different from those of the AA model, signaled by the appearance of mobility edges. We then further go beyond the tight-binding assumption and directly study the system based on the more fundamental single-particle Schrödinger equation. With this approach, we also observe the presence of mobility edges and localization properties dependent on incommensuration.

quant-ph↗

arXiv2009

Probing Kitaev Models on Small Lattices

We address the following important question: how to distinguish Kitaev models experimentally realized on small lattices from other non-topological interacting spin models. Based on symmetry arguments and exact diagonalization, we show that a particularly characteristic pattern of spin-spin correlations survives despite finite size, open boundary and thermal effects. The pattern is robust against small residual perturbing interactions and can be utilized to distinguish the Kitaev interactions from other interactions such as antiferromagnetic Heisenberg interactions. The effect of external magnetic field is also considered and found to be not critical.

cond-mat.str-el↗

arXiv2009

Signature of the interaction between dark energy and dark matter in galaxy clusters

We investigate the influence of an interaction between dark energy and dark matter upon the dynamics of galaxy clusters. We obtain the general Layser-Irvine equation in the presence of interactions, and find how, in that case, the virial theorem stands corrected. Using optical, X-ray and weak lensing data from 33 relaxed galaxy clusters, we put constraints on the strength of the coupling in the dark sector. We find that this coupling is small but positive, indicating that dark energy can be decaying into dark matter.

astro-ph↗

arXiv2009

Quantum phase diagram of fermion mixtures with population imbalance in one-dimensional optical lattices

With a recently developed time evolving block decimation (TEBD) algorithm, we numerically study the ground state quantum phase diagram of fermi mixtures with attractive inter-species interactions loaded in one-dimensional optical lattices. For our study, we adopt a general asymmetric Hubbard model (AHM) with species-dependent tunneling rates to incorporate the possibility of mass imbalance in the mixtures. We find clear signatures for the existence of a Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase in this model in the presence of population imbalance. Our simulation also reveals that in the presence of mass imbalance, the parameter space for FFLO states shrinks or even completely vanishes depending on the strength of the attractive interaction and the degree of mass imbalance.

quant-ph↗

arXiv2009

Helium star donor channel for the progenitors of type Ia supernovae

Type Ia supernovae (SNe Ia) play an important role in astrophysics, especially in the study of cosmic evolution. There are several progenitor models for SNe Ia proposed in the past years. In this paper, we have carried out a detailed study of the He star donor channel, in which a carbon-oxygen white dwarf (CO WD) accretes material from a He main sequence star or a He subgiant to increase its mass to the Chandrasekhar mass. Employing Eggleton's stellar evolution code with an optically thick wind assumption, and adopting the prescription of Kato & Hachisu (2004) for the mass accumulation efficiency of the He-shell flashes onto the WDs, we performed binary evolution calculations for about 2600 close WD binary systems. According to these calculations, we mapped out the initial parameters for SNe Ia in the orbital period--secondary mass ($\log P^{\rm i}-M^{\rm i}_2$) plane for various WD masses from this channel. The study shows that the He star donor channel is noteworthy for producing SNe Ia (i.e. $\sim 1.2\times10^{-3} {\rm yr}^{-1}$ in the Galaxy), and that the progenitors from this channel may appear as supersoft X-ray sources. Importantly, this channel can explain SNe Ia with short delay times ($\la 10^{8}$ yr), which is consistent with recent observational implications of young populations of SN Ia progenitors.

astro-ph.SR↗

arXiv2008

Superfluidity of fermions with repulsive on-site interaction in an anisotropic optical lattice near a Feshbach resonance

We present a numerical study on ground state properties of a one-dimensional (1D) general Hubbard model (GHM) with particle-assisted tunnelling rates and repulsive on-site interaction (positive-U), which describes fermionic atoms in an anisotropic optical lattice near a wide Feshbach resonance. For our calculation, we utilize the time evolving block decimation (TEBD) algorithm, which is an extension of the density matrix renormalization group and provides a well-controlled method for 1D systems. We show that the positive-U GHM, when hole-doped from half-filling, exhibits a phase with coexistence of quasi-long-range superfluid and charge-density-wave orders. This feature is different from the property of the conventional Hubbard model with positive-U, indicating the particle-assisted tunnelling mechanism in GHM brings in qualitatively new physics.

cond-mat.other↗

arXiv2008

Suppression or enhancement of the Fulde-Ferrell-Larkin-Ovchinnikov order in a one-dimensional optical lattice with particle correlated tunnelling

We study through controlled numerical simulation the ground state properties of spin-polarized strongly interacting fermi gas in an anisotropic optical lattice, which is described by an effective one-dimensional general Hubbard model with particle correlated hopping rate. We show that the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) type of state, while enhanced by a negative correlated hopping rate, can be completely suppressed by positive particle correlated hopping, yielding to an unusual magnetic phase even for particles with on-site attractive interaction We also find several different phase separation patterns for these atoms in an inhomogeneous harmonic trap, depending on the correlated hopping rate.

quant-ph↗

arXiv2008

An Updated Search of Steady TeV $γ-$Ray Point Sources in Northern Hemisphere Using the Tibet Air Shower Array

Using the data taken from Tibet II High Density (HD) Array (1997 February-1999 September) and Tibet-III array (1999 November-2005 November), our previous northern sky survey for TeV $γ-$ray point sources has now been updated by a factor of 2.8 improved statistics. From $0.0^{\circ}$ to $60.0^{\circ}$ in declination (Dec) range, no new TeV $γ-$ray point sources with sufficiently high significance were identified while the well-known Crab Nebula and Mrk421 remain to be the brightest TeV $γ-$ray sources within the field of view of the Tibet air shower array. Based on the currently available data and at the 90% confidence level (C.L.), the flux upper limits for different power law index assumption are re-derived, which are approximately improved by 1.7 times as compared with our previous reported limits.

astro-ph↗

arXiv2007

New estimation of the spectral index of high-energy cosmic rays as determined by the Compton-Getting anisotropy

The amplitude of the Compton-Getting (CG) anisotropy contains the power-law index of the cosmic-ray energy spectrum. Based on this relation and using the Tibet air-shower array data, we measure the cosmic-ray spectral index to be $-3.03 \pm 0.55_{stat} \pm < 0.62_{syst}$ between 6 TeV and 40 TeV, consistent with $-$2.7 from direct energy spectrum measurements. Potentially, this CG anisotropy analysis can be utilized to confirm the astrophysical origin of the ``knee'' against models for non-standard hadronic interactions in the atmosphere.

astro-ph↗

arXiv2007

Future plan for observation of cosmic gamma rays in the 100 TeV energy region with the Tibet air shower array : simulation and sensitivity

The Tibet air shower array, which has an effective area of 37,000 square meters and is located at 4300 m in altitude, has been observing air showers induced by cosmic rays with energies above a few TeV. We have a plan to add a large muon detector array to it for the purpose of increasing its sensitivity to cosmic gamma rays in the 100 TeV energy region by discriminating them from cosmic-ray hadrons. We have deduced the attainable sensitivity of the muon detector array using our Monte Carlo simulation. We report here on the detailed procedure of our Monte Carlo simulation.

astro-ph↗

arXiv2007

Future plan for observation of cosmic gamma rays in the 100 TeV energy region with the Tibet air shower array : physics goal and overview

The Tibet air shower array, which has an effective area of 37,000 square meters and is located at 4300 m in altitude, has been observing air showers induced by cosmic rays with energies above a few TeV. We are planning to add a large muon detector array to it for the purpose of increasing its sensitivity to cosmic gamma rays in the 100 TeV (10 - 1000 TeV) energy region by discriminating them from cosmic-ray hadrons. We report on the possibility of detection of gamma rays in the 100 TeV energy region in our field of view, based on the improved sensitivity of our air shower array deduced from the full Monte Carlo simulation.

astro-ph↗

arXiv2007

Field electron emission mechanism in an ultrathin multilayer planar cold cathode

Field electron emission from an ultrathin multilayer planar cold cathode (UMPC) including quantum well structure has been both experimentally and theoretically investigated. We found that only tuning the energy levels of UMPC the field electron emission (FE) characteristic can be evidently improved, which is unexplained by the conventional FE mechanism. Field electron emission mechanism dependent on the quantum structure effect, which supplies a favorable location of electron emission and enhances tunneling ability, has been presented to expound the notable amelioration. An approximate formula brought forward can predict the quantum FE enhancement, which the theoretical prediction is close to the experimental result.

cond-mat.mes-hall↗

arXiv2006

Implementation of controlled SWAP gates for quantum fingerprinting and photonic quantum computation

We propose a scheme to implement quantum controlled SWAP gates by directing single-photon pulses to a two-sided cavity with a single trapped atom. The resultant gates can be used to realize quantum fingerprinting and universal photonic quantum computation. The performance of the scheme is characterized under realistic experimental noise with the requirements well within the reach of the current technology.

quant-ph↗

arXiv2005

Robust quantum gates on neutral atoms with cavity-assisted photon-scattering

We propose a scheme to achieve quantum computation with neutral atoms whose interactions are catalyzed by single photons. Conditional quantum gates, including an $N$-atom Toffoli gate and nonlocal gates on remote atoms, are obtained through cavity-assisted photon scattering in a manner that is robust to random variation in the atom-photon coupling rate and which does not require localization in the Lamb-Dicke regime. The dominant noise in our scheme is automatically detected for each gate operation, leading to signalled errors which do not preclude efficient quantum computation even if the error probability is close to the unity.

quant-ph↗

arXiv2004

Engineering Schrödinger cat states through cavity-assisted interaction of coherent optical pulses

We propose a scheme to engineer Schrödinger-cat states of propagating optical pulses. Multi-dimensional and multi-partite cat states can be generated simply by reflecting coherent optical pulses successively from a single-atom cavity. The influences of various sources of noise, including the atomic spontaneous emission and the pulse shape distortion, are characterized through detailed numerical simulation, which demonstrates practicality of this scheme within the reach of current experimental technology.

quant-ph↗

arXiv2002

Evolving of a massless scalar field in Reissner--Nordström Anti--de Sitter spacetimes

We investigate the evolution of a scalar field propagating in Reissner--Nordström Anti--de Sitter spacetime. Due to the characteristic of spacetime geometry, the radiative tails associated with a massless scalar field propagation have an oscillatory exponential decay. The object--picture of the quasinormal ringing has also been obtained. For small charges, the approach to thermal equilibrium is faster for larger charges. However, after the black hole charge reaches a critical value, we get the opposite behavior for the imaginary frequencies of the quasinormal modes. Some possible explanations concerning the wiggle of the imaginary frequencies have been given. The picture of the quasinormal modes depending on the multipole index has also been illustrated.

hep-th↗