Stabilization of the p-wave superfluid state in an optical lattice

It is hard to stabilize the p-wave superfluid state of cold atomic gas in free space due to inelastic collisional losses. We consider the p-wave Feshbach resonance in an optical lattice, and show that it is possible to have a stable p-wave superfluid state where the multi-atom collisional loss is suppressed through the quantum Zeno effect. We derive the effective Hamiltonian for this system, and calculate its phase diagram in a one-dimensional optical lattice. The results show rich phase transitions between the p-wave superfluid state and different types of insulator states induced either by interaction or by dissipation.Comment: 5 pages, 5 figure

Nonlinear forecasts of ?<i>o</i>F2: variation of model predictive accuracy over time

International audienceSpace weather effects can strongly influence high-frequency (HF) communications by changing the ionospheric environment through which the radio waves propagate. Since many systems utilize HF communications, the ability to make real-time assessments of propagation conditions is an important part of space weather monitoring systems. In this paper, we present new techniques for measuring high-latitude HF communications link parameters using data from SuperDARN radars. These techniques use ground-scatter returns to define the variation in skip distance with frequency. From these data, the maximum usable frequency (MUF) as a function of range is determined and ionospheric critical frequencies are estimated. These calculations are made in near-real-time and the results are made available on the World Wide Web. F-region critical frequencies calculated using this method show good agreement with ionosonde data

The Traveling Salesman Problem: Low-Dimensionality Implies a Polynomial Time Approximation Scheme

The Traveling Salesman Problem (TSP) is among the most famous NP-hard optimization problems. We design for this problem a randomized polynomial-time algorithm that computes a (1+eps)-approximation to the optimal tour, for any fixed eps>0, in TSP instances that form an arbitrary metric space with bounded intrinsic dimension. The celebrated results of Arora (A-98) and Mitchell (M-99) prove that the above result holds in the special case of TSP in a fixed-dimensional Euclidean space. Thus, our algorithm demonstrates that the algorithmic tractability of metric TSP depends on the dimensionality of the space and not on its specific geometry. This result resolves a problem that has been open since the quasi-polynomial time algorithm of Talwar (T-04)

Enhanced ferroelectric and piezoelectric properties in doped lead-free (Bi0.5Na0.5)0.94Ba0.06TiO3 thin films

Doping effects with respect to the electrical properties of morphotropic phase boundary Bi0.5Na0.50.94Ba0.06TiO3 thin films epitaxially grown on CaRuO3 electroded LaAlO30.3Sr2AlTaO60.35 (001) substrates were investigated. Substantial enhancement of ferroelectricity and piezoelectricity has been achieved in La+Ce codoped films with a remanent polarization Pr of 29.5 C/cm2 and a remanent piezoelectric coefficient d33f of 31 pm/V, whereas Mn doping seems more favorite to reduce the leakage current by two order of magnitude. Both doped films exhibited diodelike I-V characteristics, which are correlated with resistance switching effect

Quantum Circulant Preconditioner for Linear System of Equations

We consider the quantum linear solver for $Ax=b$ with the circulant preconditioner $C$. The main technique is the singular value estimation (SVE) introduced in [I. Kerenidis and A. Prakash, Quantum recommendation system, in ITCS 2017]. However, some modifications of SVE should be made to solve the preconditioned linear system $C^{-1} Ax = C^{-1} b$. Moreover, different from the preconditioned linear system considered in [B. D. Clader, B. C. Jacobs, C. R. Sprouse, Preconditioned quantum linear system algorithm, Phys. Rev. Lett., 2013], the circulant preconditioner is easy to construct and can be directly applied to general dense non-Hermitian cases. The time complexity depends on the condition numbers of $C$ and $C^{-1} A$, as well as the Frobenius norm $\|A\|_F$

Exterior optical cloaking and illusions by using active sources: a boundary element perspective

Recently, it was demonstrated that active sources can be used to cloak any objects that lie outside the cloaking devices [Phys. Rev. Lett. \textbf{103}, 073901 (2009)]. Here, we propose that active sources can create illusion effects, so that an object outside the cloaking device can be made to look like another object. invisibility is a special case in which the concealed object is transformed to a volume of air. From a boundary element perspective, we show that active sources can create a nearly "silent" domain which can conceal any objects inside and at the same time make the whole system look like an illusion of our choice outside a virtual boundary. The boundary element method gives the fields and field gradients (which can be related to monopoles and dipoles) on continuous curves which define the boundary of the active devices. Both the cloaking and illusion effects are confirmed by numerical simulations

Neuroprotective roles of asiaticoside on hydrogen peroxide-induced toxicity in SH-SY5Y cells

This study aims to determine whether the neuroprotective role of asiaticoside at maximum non-toxic dose (MNTD) or half MNTD (½MNTD) on H2O2-induced neurotoxicity in SH-SY5Y cells was mediated by regulation of reactive oxygen species (ROS) and nitric oxide (NO) through inducible nitric oxide synthase (iNOS) and heme-oxygenase 1 (HO-1). The levels of ROS, NO, iNOS and HO-1 in SH-SY5Y cells pre-treated with asiaticoside ½MNTD were significantly reduced by 15.3, 55.6, 24.8 and 6.7 %, respectively as compared to the H2O2 treatment group. Cells pre-treated MNTD only reduced the iNOS level significantly. Asiaticoside, particularly at ½MNTD reduced the ROS, NO and iNOS levels. Contrarily, the HO-1 expression was down-regulated when treated with asiaticoside, which further suggest that asiaticoisde exerted its neuroprotective effects via HO-1 regulation.Keywords: Asiaticoside; Heme-oxygenase 1; Inducible nitric oxide synthase; Nitric oxide; Reactive oxygen species