arXiv subjects

Jie Jiang

Publications and source records attributed to Jie Jiang.

At least 325 records · Page 18Linked to original sources

arXiv2019

Different contributions to space weather and space climate from different big solar active regions

The purpose of this paper is to show that large active regions (ARs) with different magnetic configurations have different contributions to short-term and long-term variations of the Sun. As a case study, the complex $δ$-type AR 12673 and the simple $β$-type AR 12674 are investigated in detail. Since the axial dipole moment at cycle minimum determines the amplitude of the subsequent cycle and space climate, we have assimilated the individual observed magnetic configurations of these two ARs into a surface flux transport model to compare their contributions to the axial dipole moment $D$. We find that AR 12673 has a significant effect on $D$ at the end of the cycle, making it weaker because of the abnormal and complicated magnetic polarities. An initial strongly positive $D$ ends up with a strongly negative value. The flare-poor AR 12674 has a greater contribution to the long-term axial dipole moment than the flare-rich AR 12673. We then carry out a statistical analysis of ARs larger than 800 $μ$Hem from 1976 to 2017. We use the flare index FI and define an axial dipole moment index DI to quantify the effects of each AR on space weather and space climate, respectively. Whereas the FI has a strong dependence on the magnetic configuration, the DI shows no such dependence. The DI is mainly determined by the latitudinal location and the latitudinal separation of the positive and negative magnetic fluxes of the ARs. Simple ARs have the same possibility as complex ARs to produce big DI values affecting space climate.

astro-ph.SR↗

arXiv2018

Numerical study of inflationary preheating with arbitrary power-law potential and a realization of curvaton mechanism

During inflationary preheating, the energy stored in the inflaton field is rapidly converted into excitations of other entropy fields. This stage is characterized by exponential particle production due to parametric resonance and is notoriously difficult to analyze using analytic methods. We develop a detailed numerical simulation to investigate inflationary preheating when the potential of the inflaton is a power-law function with arbitrary power index. To achieve a successful graceful exit from a primordial inflationary phase to a smooth, oscillatory phase during preheating, we assume the inflaton potential reduces to a quadratic function in the infrared regime, which may be regarded as a mass term at low energy scales. With this simplification, our numerical method may be applied to unconventional chaotic inflation models. To demonstrate its validity, we numerically analyze the preheating stage of axion-monodromy inflation which is inspired by string theory. By performing perturbation analyses, our result shows that the power spectrum of primordial curvature perturbation can be dominated by fluctuations of entropy field rather than those of inflaton, which can be regarded as a particular realization of the curvaton mechanism through a preheating process.

astro-ph.CO↗

arXiv2018

Circuit Complexity for Fermionic Thermofield Double states

Motivated by the holographic complexity proposals, in this paper, we investigate the time dependence of the complexity for the Fermionic thermofield double state (TFD) using the Nielsen approach and Fubini-Study (FS) approach separately. In both two approaches, we discuss the results for different reference states: the Dirac vacuum state and the Gaussian state which has no spatial entanglement (NSE). For Dirac vacuum reference state, we find that the complexity by both two approaches is time independent and the circuit complexity shares the same expression for both methods with the $L^2$ norm. For the NSE reference state, the complexity by the Nielsen approach is time-dependent while it by the FS approach is time-independent. Further, we find our dynamical results are in good agreement with the bosonic case, where the complexity evolves in time and saturates after a time at the order of the inverse temperature. And we show that the complexity of formation is also shared same similar behaviors with the holographic complexity.

hep-th↗

arXiv2018

Global Stability of Keller--Segel Systems in Critical Lebesgue Spaces

In this paper, we study the global stability of classical solutions to a Keller--Segel equations in scaling-invariant spaces. We prove that for any given $0<\mathcal{M}<1+λ_1$ with $λ_1$ being the first eigenvalue of Neumann Laplacian, the initial--boundary value problem of the Keller--Segel system has a unique globally bounded classical solution provided that the initial datum is chosen sufficiently close to $(\mathcal{M},\mathcal{M})$ in the norm of $L^{d/2}(Ω)\times \dot{W}^{1,d}(Ω)$ and satisfies a natral average mass condition. Our proof is based on the perturbation theory of semigroups and certain delicate exponential decay estimates for the linearized semigroup. Our result suggests a new observation that nontrivial classical solution for Keller--Segel equation can be obtained globally starting from suitable initial data with arbitrarily large total mass provided that volume of the bounded domain is large, correspondingly.

math.AP↗

arXiv2018

Holographic complexity in charged Vaidya black hole

In this paper, we use the "complexity equals action" (CA) conjecture to discuss growth rate of the complexity in a charged AdS-Vaidya black hole formed by collapsing an uncharged spherically symmetric thin shell of null fluid. Using the approach proposed by Lehner $et\, al.$, we evaluate the action growth rate and the slope of the complexity of formation. Then, we demonstrate that the behaviors of them are in agreement with the switchback effect for the light shock wave case. Moreover, we show that to obtain an expected property of the complexity, it is also necessary for the CA conjecture to add the particular counterterm on the null boundaries.

hep-th↗

arXiv2018

The longlived charged massive scalar field in the higher-dimensional Reissner--Nordström spacetime

The quasinormal resonance frequency of the higher-dimensional Reissner--Nordström (RN) black hole due to charged massive scalar field perturbation is deduced analytically in the eikonal regime. The characteristic decay timescale of the charged massive scalar perturbation in the background of the higher-dimensional RN spacetime is then obtained. The result reveals that longlived charged massive scalar field can exist in higher-dimensional RN spacetime under a certain condition.

gr-qc↗

arXiv2018

Circuit complexity for free Fermion with a mass quench

By using a recent approach proposed by Hackl $et\, al.$ to evaluate the complexity of the free fermionic Gaussian state, we compute the complexity of the Dirac vacuum state as well as the excited state of the Fermi system with a mass quench. First of all, we review the counting method given by Hackl $et\, al.$, and demonstrate that the result can be adapted to all of the compact transformation group $G$. Then, we utilize this result to study the time evolution of the complexity of these states. We show that, for the rotational invariant reference state, the total complexity of the incoming vacuum state will saturate the value of the instantaneous vacuum state at the late time, with a typical timescale to achieve the final stable state. Moreover, we find that the complexity growth under the sudden quench is directly proportional to the mass difference, which shares similar behaviors with the holograph complexity growth rate in an AdS-Vaidya black hole with a shock wave, even though the dual boundary CFT is strongly coupled. Finally, we obtain some features of the excited state and the non-rotational reference state.

hep-th↗

arXiv2018

Action growth rate for a higher curvature gravitational theory

In this paper, we use the "complexity equals action" (CA) conjecture to discuss the action growth rate in a black hole with multiple Killing horizons for a higher curvature theory of gravity. Based on the Noether charge formalism of Iyer and Wald, a general formalism can be resorting to finding the action growth rate within the WDW patch at the late time approximation. Moreover, as an application, we apply this formalism to a $U(1)$ invariance matter fields and utilise our results in two specific cases. Our results are universal and can be considered as the extension of the asymptotic AdS to the arbitrary asymptotic one.

hep-th↗

arXiv2018

Defect Engineering for Modulating the Trap States in Two-dimensional Photoconductor

Defect induced trap states are essential in determining the performance of semiconductor photodetectors. The de-trap time of carriers from a deep trap could be prolonged by several orders of magnitude as compared to shallow trap, resulting in additional decay/response time of the device. Here, we demonstrate that the trap states in two-dimensional ReS2 could be efficiently modulated by defect engineering through molecule decoration. The deep traps that greatly prolong the response time could be mostly filled by Protoporphyrin (H2PP) molecules. At the same time, carrier recombination and shallow traps would in-turn play dominant roles in determining the decay time of the device, which can be several orders of magnitude faster than the as-prepared device. Moreover, the specific detectivity of the device is enhanced (as high as ~1.89 x 10^13 Jones) due to the significant reduction of dark current through charge transfer between ReS2 and molecules. Defect engineering of trap states therefore provides a solution to achieve photodetectors with both high responsivity and fast response.

cond-mat.mtrl-sci↗

arXiv2018

Predictability of the solar cycle over one cycle

The prediction of the strength of future solar cycles is of interest because of its practical significance for space weather and as a test of our theoretical understanding of the solar cycle. The Babcock-Leighton mechanism allows predictions by assimilating the observed magnetic field on the surface. But the emergence of sunspot groups has the random properties, which make it impossible to accurately predict the solar cycle and also strongly limit the scope of cycle predictions. Hence we develop the scheme to investigate the predictability of the solar cycle over one cycle. When a cycle has been ongoing for more than 3 years, the sunspot group emergence can be predicted along with its uncertainty during the rest time of the cycle. The method for doing this is to start by generating a set of random realizations which obey the statistical relations of the sunspot emergence. We then use a surface flux transport model to calculate the possible axial dipole moment evolutions. The correlation between the axial dipole moment at cycle minimum and the subsequent cycle strength and other empirical properties of solar cycles are used to predict the possible profiles of the subsequent cycle. We apply this scheme to predict the large-scale field evolution from 2018 to the end of cycle 25, whose maximum strength is expected to lie in the range from 93 to 155 with a probability of 95\%.

astro-ph.SR↗

arXiv2018

Entropy in the interior of a Kerr black hole

Christodoulou and Rovelli have shown that the maximal interior volume of a Schwarzschild black hole linearly grows with time. Recently, their conclusion has been extended to the Reissner{-}Nordstr$\ddot{\text{o}}$m and Kerr black holes. Meanwhile, the entropy of interior volume in a Schwarzschild black hole has also been calculated. Here, a new method calculating the entropy of interior volume of the black hole is given and it can be used in more general cases. Using this method, the entropy associated with the volume of a Kerr black hole is calculated and it is found that the entropy is proportional to the Bekenstein-Hawking entropy in the early stage of black hole evaporation. Using the differential form, the entropy of interior volume in a Schwarzschild black hole is recalculated. It is shown that the proportionality coefficient between the entropy and the Bekenstein-Hawking entropy is half of that given in the previous literature. Moreover, the black hole information paradox is brought up again and discussed.

gr-qc↗

arXiv2018

Observation of Meisser effect in Kapton Tapes

Composed of organic compounds, Kapton tape is regularly used as a non-conducting and non-magnetic material in cryogenic experiments. Here we report the discovery of Meisser effect at transition temperature (Tc) of ~ 3.8 K and ~ 8.0 K in Kapton tapes. New organic superconducting materials may be further explored in the tapes.

cond-mat.supr-con↗

arXiv2017

Predicting solar surface large-scale magnetic field of Cycle 24

The Sun's surface field, especially the polar field, sets the boundary condition for the coronal and heliospheric magnetic fields, but also provides us insight into the dynamo process. The evolution of the polar fields results from the emergence and subsequent evolution of magnetic flux through the solar surface. In this paper we use a Monte Carlo approach to investigate the evolution of the fields during the decay phase of cycle 24. Our simulations include the emergence of flux through the solar surface with statistical properties derived from previous cycles. The well-calibrated surface flux transport model is used to follow the evolution of the large-scale field. We find the polar field can be well reproduced one year in advance using the observed synoptic magnetograms as the initial condition. The temporary variation of the polar field measured by Wilcox Solar Observatory (WSO), e.g., the strong decrease of the south polar field during 2016-2017 which is not shown by SDO/HMI and NSO/SOLIS data usually is not well reproduced. We suggest observational effects, such as the effect of the large gradient of the magnetic field around the southern polar cap and the low resolution of WSO might be responsible. The northern hemisphere polar field is predicted to increase during 2017. The southern polar field is predicted to be stable during 2017-2018. At the end of 2017, the magnetic field in two poles is predicted to be similar (although of opposite polarities). The expected value for the dipole moment around 2020 is 1.76$\pm$0.68 G and $2.11\pm0.69$ G based on the initial conditions from SDO/HMI and NSO/SOLIS synoptic magnetograms, respectively. It is comparable to that observed one at the end of Cycle 23 (about 1.6G based on SOHO/MDI).

astro-ph.SR↗

arXiv2017

Interfacial amplification for graphene based position-sensitive-detectors

Position-sensitive-detectors (PSDs) based on lateral photoeffect has been widely used in diverse applications, including optical engineering, aerospace and military fields. With increasing demand in long distance, low energy consumption, and weak signal sensing systems, the poor responsivity of conventional PSDs has become a bottleneck limiting its applications. Herein, we present a high performance graphene based PSDs with revolutionary interfacial amplification mechanism. Signal amplification in the order of ~10^4 has been demonstrated by utilizing the ultrahigh mobility of graphene and long lifetime of photo-induced carriers at the interface of SiO2/Si. This would improve the detection limit of Si-based PSDs from uW to nW level, without sacrificing the spatial resolution and response speed. Such interfacial amplification mechanism is compatible with current Si technology and can be easily extended to other sensing systems.

cond-mat.mes-hall↗

arXiv2017

FISF: Better User Experience using Smaller Bandwidth for Panoramic Virtual Reality Video

The panoramic video is widely used to build virtual reality (VR) and is expected to be one of the next generation Killer-Apps. Transmitting panoramic VR videos is a challenging task because of two problems: 1) panoramic VR videos are typically much larger than normal videos but they need to be transmitted with limited bandwidth in mobile networks. 2) high-resolution and fluent views should be provided to guarantee a superior user experience and avoid side-effects such as dizziness and nausea. To address these two problems, we propose a novel interactive streaming technology, namely Focus-based Interactive Streaming Framework (FISF). FISF consists of three parts: 1) we use the classic clustering algorithm DBSCAN to analyze real user data for Video Focus Detection (VFD); 2) we propose a Focus-based Interactive Streaming Technology (FIST), including a static version and a dynamic version; 3) we propose two optimization methods: focus merging and prefetch strategy. Experimental results show that FISF significantly outperforms the state-of-the-art. The paper is submitted to Sigcomm 2017, VR/AR Network on 31 Mar 2017 at 10:44:04am EDT.

cs.MM↗

arXiv2016

Blow-up for a Three Dimensional Keller-Segel Model with Consumption of Chemoattractant

We investigate blow-up properties for the initial-boundary value problem of a Keller-Segel model with consumption of chemoattractant when the spatial dimension is three. Through a kinetic reformulation of the Keller-Segel model, we first derive some higher-order estimates and obtain certain blow-up criteria for the local classical solutions. These blow-up criteria generalize the results in [4,5] from the whole space $\mathbb{R}^3$ to the case of bounded smooth domain $Ω\subset \mathbb{R}^3$. Lower global blow-up estimate on $\|n\|_{L^\infty(Ω)}$ is also obtained based on our higher-order estimates. Moreover, we prove local non-degeneracy for blow-up points.

math.AP↗

arXiv2016

Probing the Intrinsic Optical Quality of CVD Grown MoS2

The optical emission efficiency of two dimensional layered transition metal dichalcogenides (TMDs) is one of the most important parameter that affects their optoelectronic performance. Optimization of growth parameters of chemical vapor deposition (CVD) to achieve optoelectronics-grade quality TMDs is therefore highly desirable. Here, we present a systematic photoluminescence (PL) spectroscopic approach to assess the intrinsic optical and crystalline quality of CVD grown MoS2. We suggest that the intensity ratio between PL measured in air and vacuum could be used as an effective way to monitor the intrinsic optical quality of CVD MoS2. Low temperature PL measurements are also used to evaluate the structural defects in MoS2 by defect-associated bound exciton emission, which is well correlated with the field effect carrier mobilities of MoS2 grown at different temperatures. This work therefore provides a sensitive, noninvasive method to characterize the optical properties of TMDs, allow tuning of growth parameters for the development of optoelectronic devices.

cond-mat.mtrl-sci↗

arXiv2016

Three Photon Absorption in Optical Parametric Oscillators Based on OP-GaAs

We report on the first singly-resonant (SR), synchronously pumped optical parametric oscillator (OPO) based on orientation-patterned gallium arsenide (OP-GaAs). Together with a doubly resonant (DR) degenerate OPO based on the same OP-GaAs material, the output spectra cover 3 to 6 $μ$m within ~3 dB of relative power. The DR-OPO has the highest output power reported to date from a femtosecond, synchronously pumped OPO based on OP-GaAs. We discovered strong three photon absorption with a coefficient of 0.35 ${\pm}$ 0.06 cm${^3}$/GW${^2}$ for our OP-GaAs sample, which limits the output power of these OPOs as mid-IR light sources. We present a detailed study of the three photon loss on the performance of both the SR and DR-OPOs, and compare them to those without this loss mechanism.

physics.optics↗