arXiv subjects

Bin Wang

Publications and source records attributed to Bin Wang.

At least 973 records · Page 54Linked to original sources

arXiv2012

Modeling $f(R)$ gravity in terms of mass dilation rate

We review the conformal equivalence in describing the background expansion of the universe by $f(R)$ gravity both in the Jordan frame and the Einstein frame. In the Jordan frame, we present the general analytic expression for $f(R)$ models that have the same expansion history as the $Λ$CDM model. This analytic form can provide further insights on how cosmology can be used to test the $f(R)$ gravity at the largest scales. Moreover we present a systematic and self-consistent way to construct the viable $f(R)$ model in Jordan frame using the mass dilation rate function from the Einstein frame through the conformal transformation. In addition, we extend our study to the linear perturbation theories and we further exhibit the equivalence of the $f(R)$ gravity presented in the Jordan frame and Einstein frame in the perturbed space-time. We argue that this equivalence has solid physics root.

astro-ph.CO↗

arXiv2012

Probing charge scattering mechanisms in suspended graphene by varying its dielectric environment

Graphene with high carrier mobility μ is required both for graphene-based electronic devices and for the investigation of the fundamental properties of graphene's Dirac fermions. It is largely accepted that the mobility-limiting factor in graphene is the Coulomb scattering off of charged impurities that reside either on graphene or in the underlying substrate. This is true both for traditional graphene devices on SiO2 substrates and possibly for the recently reported high-mobility suspended and supported devices. An attractive approach to reduce such scattering is to place graphene in an environment with high static dielectric constant κ that would effectively screen the electric field due to the impurities. However, experiments so far report only a modest effect of high-κ environment on mobility. Here, we investigate the effect of the dielectric environment of graphene by studying electrical transport in multi-terminal graphene devices that are suspended in liquids with κ ranging from 1.9 to 33. For non-polar liquids (κ<5) we observe a rapid increase of μ with κ and report a record room-temperature mobility as large as ~60,000 cm2/Vs for graphene devices in anisole (κ=4.3), while in polar liquids (κ>18) we observe a drastic drop in mobility. We demonstrate that non-polar liquids enhance mobility by screening charged impurities adsorbed on graphene, while charged ions in polar liquids cause the observed mobility suppression. Furthermore, using molecular dynamics simulation we establish that scattering by out-of-plane flexural phonons, a dominant scattering mechanism in suspended graphene in vacuum at room temperature, is suppressed by the presence of liquids. We expect that our findings may provide avenues to control and reduce carrier scattering in future graphene-based electronic devices.

cond-mat.mes-hall↗

arXiv2012

Gauss-Bonnet holographic superconductors in Born-Infeld electrodynamics with backreactions

We develop a general holographic superconductor away from the probe limit by considering the corrections both in the gravity and in the gauge matter fields. We find the consistent effects of the high curvature correction in the gravity, the nonlinear correction in the gauge matter field and the backreaction on the dynamics of bulk AdS background and boundary CFT. They all have the effect to protect the stability of the bulk spacetime and hinder the formation of the scalar hair condensation on the boundary.

hep-th↗

arXiv2011

Obstructions to the deformations of curves to other hypersurfaces

We are interested in obstructions to the FIRST order deformation of a pair of a smooth hypersurface $f_0$ and a smooth curve $C_0$ contained in $f_0$. In the first half of the paper, we give necessary conditions for the pair to deform in the first order. In particular, for a rational curve $C_0$, this necessary condition is $$H^1(N_{C_0}f_0(1))=0.$$ In the second half, we apply the necessary conditions from the first half of the paper to study the geometry of smooth curves in hypersurfaces. The main application is for the case where $C_0$ is a rational curve.

math.AG↗

arXiv2011

Genus of curves in generic hypersurfaces

This is the continuation of our paper [10]. In this paper which is self contained, we would like to give a different obstruction formula to the FIRST order deformation of the pair of a smooth curve and a smooth hypersurface. This obstruction formula leads to a genus formula for a smooth curve in a smooth hypersurface. As an application we show that smooth elliptic curves in a smooth hypersurface of degree $$h\geq 2n-1$$ in the projective space $\mathbf P^n, n\geq 3,$ can't deform in the first order to all hypersurfaces of the same degree. In particular, there are no smooth elliptic curves in generic hypersurfaces of degree $$h\geq 2n-1.$$ This application in return leads to a study of the deformation of the pair mentioned above.

math.AG↗

arXiv2011

Holographic superconductor models with the Maxwell field strength corrections

We study the effect of the quadratic field strength correction to the usual Maxwell field on the holographic dual models in the backgrounds of AdS black hole and AdS soliton. We find that in the black hole background, the higher correction to the Maxwell field makes the condensation harder to form and changes the expected relation in the gap frequency. This effect is similar to that caused by the curvature correction. However, in the soliton background we find that different from the curvature effect, the correction to the Maxwell field does not influence the holographic superconductor and insulator phase transition.

gr-qc↗

arXiv2011

Perturbations around the AdS Born-Infeld black holes

We study the quasinormal mode of the perturbation of the scalar field interacting with the electromagnetic field in the backgrounds of Schwarzschild AdS black hole, the Reissner-Nordstrom AdS black hole and the Born-Infeld AdS black hole. We disclose influence by the electric charge $Q$, the coupling between the scalar and electromagnetic field $q$ and the Born-Infeld parameter $b$ on the quasinormal frequencies of the scalar perturbation. We observe the possible growing mode in the perturbation when the scalar field strongly couples to the electromagnetic field. When the electromagnetic field becomes nonlinear described by the Born-Infeld electrodynamics, the nonlinearity described by the Born-Infeld parameter can hinder the growing mode to appear in the scalar perturbation. The quasinormal mode of the scalar field perturbation can help us further understand the physics in the holographic superconductor.

gr-qc↗

arXiv2011

Bandwidth Selection for Weighted Kernel Density Estimation

In the this paper, the authors propose to estimate the density of a targeted population with a weighted kernel density estimator (wKDE) based on a weighted sample. Bandwidth selection for wKDE is discussed. Three mean integrated squared error based bandwidth estimators are introduced and their performance is illustrated via Monte Carlo simulation. The least-squares cross-validation method and the adaptive weight kernel density estimator are also studied. The authors also consider the boundary problem for interval bounded data and apply the new method to a real data set subject to informative censoring.

stat.ME↗

arXiv2011

Analytical investigation of the phase transition between holographic insulator and superconductor in Gauss-Bonnet gravity

We employ the variational method for the Sturm-Liouville eigenvalue problem to analytically study the phase transition between the holographic insulator and superconductor in the Gauss-Bonnet gravity. By investigating the s-wave and p-wave holographic insulator/superconductor models, we find that this analytic method is more effective to obtain the analytic results on the condensation and the critical phenomena in the AdS soliton background in Gauss-Bonnet gravity. Our analytic result can be used to back up the numerical computations in the AdS soliton with Gauss-Bonnet correction.

gr-qc↗

arXiv2011

Deep connection between f(R) gravity and the interacting dark sector model

We examine the conformal equivalence between the $f(R)$ gravity and the interacting dark sector model. We review the well-known result that the conformal transformation physically corresponds to the mass dilation which marks the strength of interaction between dark sectors. Instead of modeling f(R) gravity in the Jordan frame, we construct the $f(R)$ gravity in terms of mass dilation function in the Einstein frame. We find that the condition to keep $f(R)$ gravity consistent with CMB observations ensures the energy flow from dark energy to dark matter in the corresponding interacting model, which meets the requirement to alleviate the coincidence problem in the Einstein framework.

gr-qc↗

arXiv2011

Quasinormal behavior of massless scalar field perturbation in Reissner-Nordstrom anti-de Sitter spacetimes

We present a comprehensive study of the massless scalar field perturbation in the Reissner-Nordstrom anti-de Sitter (RNAdS) spacetime and compute its quasinormal modes (QNM). For the lowest lying mode, we confirm and extend the dependence of the QNM frequencies on the black hole charge got in previous works. In near extreme limit, under the scalar perturbation we find that the imaginary part of the frequency tends to zero, which is consistent with the previous conjecture based on electromagnetic and axial gravitational perturbations. For the extreme value of the charge, the asymptotic field decay is dominated by a power-law tail, which shows that the extreme black hole can still be stable to scalar perturbations. We also study the higher overtones for the RNAdS black hole and find large variations of QNM frequencies with the overtone number and black hole charge. The nontrivial dependence of frequencies on the angular index is also discussed.

hep-th↗

arXiv2011

Geometrical Model for Non-Zero theta_13

Based on Friedberg and Lee's geometric picture by which the tribimaximal Pontecorvo-Maki-Nakawaga-Sakata leptonic mixing matrix is constructed, namely, corresponding mixing angles correspond to the geometric angles among the sides of a cube. We suggest that the three realistic mixing angles, which slightly deviate from the values determined for the cube, are due to a viable deformation from the perfectly cubic shape. Taking the best-fitted results of $θ_{12}$ and $θ_{23}$ as inputs, we determine the central value of $\sin^22θ_{13}$ should be 0.0238, with a relatively large error tolerance; this value lies in the range of measurement precision of the Daya Bay experiment and is consistent with recent results from the T2K Collaboration.

hep-ph↗

arXiv2011

Calculation of bulk viscosity of QCD at zero temperature and finite chemical potential

In this letter, based on Kubo's formula and the QCD low energy theorem, we propose a direct formula for calculating the bulk viscosity of QCD at finite chemical potential $μ$ and zero temperature. According to this formula, the bulk viscosity at finite $μ$ is totally determined by the dressed quark propagator at finite $μ$. We then use a dynamical, confining Dyson-Schwinger equation model of QCD to calculate the bulk viscosity at finite $μ$. It is found that no sharp peak behavior of the bulk viscosity at finite $μ$ is observed, which is quite different from that of the bulk viscosity at finite temperature.

hep-ph↗

arXiv2011

Clemens' conjecture: part I

This is a series of two papers in which we solve the Clemens conjecture: there are only finitely many smooth rational curves of each degree in a generic quintic threefold. In this first paper, we deal with a family of smooth Calabi-Yau threefolds f_εfor a small complex number ε. We give an geometric obstruction, deviated quasi-regular deformations B_b of c_ε, to a deformation of the rational curve c_εin a Calabi-Yau threefold f_ε.

math.AG↗

arXiv2011

Clemens' conjecture: part II

This is the part II of our series of two papers, "Clemens' conjecture: part I", "Clemens' conjecture: part II". Continuing from part I, in this paper we turn our attention to general quintic threefolds. In a universal quintic threefold X, we construct a family of quasi-regular deformation B_b such that the generic member in this family is non-deviated, but some special member is deviated. By the result from part I, this is impossible unless there is no one parameter family of smooth rational curves in a generic quintic threefold.

math.AG↗

arXiv2011

Holographic superconductor developed in BTZ black hole background with backreactions

We develop a holographic superconductor in BTZ black hole background with backreactions. We investigate the influence of the backreaction on the condensation of the scalar hair and the dynamics of perturbation in the background spacetime. When the Breitenlohner-Freedman bound is approached, we argue that only one of two possible operators can reflect the real property of the condensation in the holographic superconductor. This argument is supported by the investigation in dynamics.

hep-th↗

arXiv2011

Breaking parameter degeneracy in interacting dark energy models from observations

We study the interacting dark energy model with time varying dark energy equation of state. We examine the stability in the perturbation formalism and the degeneracy among the coupling between dark sectors, the time-dependent dark energy equation of state and dark matter abundance in the cosmic microwave background radiation. Further we discuss the possible ways to break such degeneracy by doing global fitting using the latest observational data and we get a tight constraint on the interaction between dark sectors.

astro-ph.CO↗

arXiv2011

Quench induced Mott insulator to superfluid quantum phase transition

Mott insulator to superfluid quenches have been used by recent experiments to generate exotic superfluid phases. While the final Hamiltonian following the sudden quench is that of a superfluid, it is not a priori clear how close the final state of the system approaches the ground state of the superfluid Hamiltonian. To understand the nature of the final state we calculate the temporal evolution of the momentum distribution following a Mott insulator to superfluid quench. Using the numerical infinite time-evolving block decimation approach and the analytical rotor model approximation we establish that the one and two dimensional Mott insulators following the quench equilibriate to thermal states with spatially short-ranged coherence peaks in the final momentum distribution and therefore are not strict superfluids. However, in three dimensions we find a divergence in the momentum distribution indicating the emergence of true superfluid order.

cond-mat.quant-gas↗