GSTDTAP

浏览/检索结果: 共15条,第1-10条 帮助

已选(0)清除 条数/页:   排序方式:
Nuclear force probed at short distances 期刊论文
NATURE, 2020, 578 (7796) : 524-525
作者:  Shukla, Aditi;  Yen, Jenny;  Pagano, Daniel J.;  Dodso, Anne E.;  Fei, Yuhan;  Gorham, Josh;  Seidman, J. G.;  Wickens, Marvin;  Kennedy, Scott
收藏  |  浏览/下载:23/0  |  提交时间:2020/07/03

The dense soup of matter in the core of neutron stars is hard to model, but particle-accelerator experiments in which energetic electrons scatter off atomic nuclei could help to explore this high-density regime.


A test of effective nucleon-nucleon interactions at short separations.


  
Simulation of Hubbard model physics in WSe2/WS2 moire superlattices 期刊论文
NATURE, 2020, 579 (7799) : 353-+
作者:  Stein, Reed M.;  Kang, Hye Jin;  McCorvy, John D.;  Glatfelter, Grant C.;  Jones, Anthony J.;  Che, Tao;  Slocum, Samuel;  Huang, Xi-Ping;  Savych, Olena;  Moroz, Yurii S.;  Stauch, Benjamin;  Johansson, Linda C.;  Cherezov, Vadim;  Kenakin, Terry;  Irwin, John J.;  Shoichet, Brian K.;  Roth, Bryan L.;  Dubocovich, Margarita L.
收藏  |  浏览/下载:32/0  |  提交时间:2020/07/03

Study of WSe2/WS2 moire superlattices reveals the phase diagram of the triangular-lattice Hubbard model, including a Mott insulating state at half-filling and a possible magnetic quantum phase transition near 0.6 filling.


The Hubbard model, formulated by physicist John Hubbard in the 1960s(1), is a simple theoretical model of interacting quantum particles in a lattice. The model is thought to capture the essential physics of high-temperature superconductors, magnetic insulators and other complex quantum many-body ground states(2,3). Although the Hubbard model provides a greatly simplified representation of most real materials, it is nevertheless difficult to solve accurately except in the one-dimensional case(2,3). Therefore, the physical realization of the Hubbard model in two or three dimensions, which can act as an analogue quantum simulator (that is, it can mimic the model and simulate its phase diagram and dynamics(4,5)), has a vital role in solving the strong-correlation puzzle, namely, revealing the physics of a large number of strongly interacting quantum particles. Here we obtain the phase diagram of the two-dimensional triangular-lattice Hubbard model by studying angle-aligned WSe2/WS2 bilayers, which form moire superlattices(6) because of the difference between the lattice constants of the two materials. We probe the charge and magnetic properties of the system by measuring the dependence of its optical response on an out-of-plane magnetic field and on the gate-tuned carrier density. At half-filling of the first hole moire superlattice band, we observe a Mott insulating state with antiferromagnetic Curie-Weiss behaviour, as expected for a Hubbard model in the strong-interaction regime(2,3,7-9). Above half-filling, our experiment suggests a possible quantum phase transition from an antiferromagnetic to a weak ferromagnetic state at filling factors near 0.6. Our results establish a new solid-state platform based on moire superlattices that can be used to simulate problems in strong-correlation physics that are described by triangular-lattice Hubbard models.


  
Repetitive floods intensify outmigration and climate gentrification in coastal cities 期刊论文
ENVIRONMENTAL RESEARCH LETTERS, 2020, 15 (3)
作者:  de Koning, Koen;  Filatova, Tatiana
收藏  |  浏览/下载:22/0  |  提交时间:2020/07/02
agent-based model  flood risk  climate gentrification  housing market  climate change  regime shift  
Loopy Levy flights enhance tracer diffusion in active suspensions 期刊论文
NATURE, 2020, 579 (7799) : 364-+
作者:  Hu, Bo;  Jin, Chengcheng;  Zeng, Xing;  Resch, Jon M.;  Jedrychowski, Mark P.;  Yang, Zongfang;  Desai, Bhavna N.;  Banks, Alexander S.;  Lowell, Bradford B.;  Mathis, Diane;  Spiegelman, Bruce M.
收藏  |  浏览/下载:28/0  |  提交时间:2020/07/03

A theoretical framework describing the hydrodynamic interactions between a passive particle and an active medium in out-of-equilibrium systems predicts long-range Levy flights for the diffusing particle driven by the density of the active component.


Brownian motion is widely used as a model of diffusion in equilibrium media throughout the physical, chemical and biological sciences. However, many real-world systems are intrinsically out of equilibrium owing to energy-dissipating active processes underlying their mechanical and dynamical features(1). The diffusion process followed by a passive tracer in prototypical active media, such as suspensions of active colloids or swimming microorganisms(2), differs considerably from Brownian motion, as revealed by a greatly enhanced diffusion coefficient(3-10) and non-Gaussian statistics of the tracer displacements(6,9,10). Although these characteristic features have been extensively observed experimentally, there is so far no comprehensive theory explaining how they emerge from the microscopic dynamics of the system. Here we develop a theoretical framework to model the hydrodynamic interactions between the tracer and the active swimmers, which shows that the tracer follows a non-Markovian coloured Poisson process that accounts for all empirical observations. The theory predicts a long-lived Levy flight regime(11) of the loopy tracer motion with a non-monotonic crossover between two different power-law exponents. The duration of this regime can be tuned by the swimmer density, suggesting that the optimal foraging strategy of swimming microorganisms might depend crucially on their density in order to exploit the Levy flights of nutrients(12). Our framework can be applied to address important theoretical questions, such as the thermodynamics of active systems(13), and practical ones, such as the interaction of swimming microorganisms with nutrients and other small particles(14) (for example, degraded plastic) and the design of artificial nanoscale machines(15).


  
Long-term cyclic persistence in an experimental predator-prey system 期刊论文
NATURE, 2020, 577 (7789) : 226-+
作者:  Blasius, Bernd;  Rudolf, Lars;  Weithoff, Guntram;  Gaedke, Ursula;  Fussmann, Gregor F.
收藏  |  浏览/下载:31/0  |  提交时间:2020/04/16

Predator-prey cycles rank among the most fundamental concepts in ecology, are predicted by the simplest ecological models and enable, theoretically, the indefinite persistence of predator and prey(1-4). However, it remains an open question for how long cyclic dynamics can be self-sustained in real communities. Field observations have been restricted to a few cycle periods(5-8) and experimental studies indicate that oscillations may be short-lived without external stabilizing factors(9-19). Here we performed microcosm experiments with a planktonic predator-prey system and repeatedly observed oscillatory time series of unprecedented length that persisted for up to around 50 cycles or approximately 300 predator generations. The dominant type of dynamics was characterized by regular, coherent oscillations with a nearly constant predator-prey phase difference. Despite constant experimental conditions, we also observed shorter episodes of irregular, non-coherent oscillations without any significant phase relationship. However, the predator-prey system showed a strong tendency to return to the dominant dynamical regime with a defined phase relationship. A mathematical model suggests that stochasticity is probably responsible for the reversible shift from coherent to non-coherent oscillations, a notion that was supported by experiments with external forcing by pulsed nutrient supply. Our findings empirically demonstrate the potential for infinite persistence of predator and prey populations in a cyclic dynamic regime that shows resilience in the presence of stochastic events.


  
Regime switching effect of financial development on energy intensity: Evidence from Markov-switching vector error correction model 期刊论文
ENERGY POLICY, 2019, 135
作者:  Pan, Xiongfeng;  Uddin, Md. Kamal;  Saima, Umme;  Guo, Shucen;  Guo, Ranran
收藏  |  浏览/下载:27/0  |  提交时间:2020/02/17
Financial development  Energy intensity  Markov-switching  Vector error correction model  Regime switching  Bangladesh  
Factors affecting interdecadal variability of air-sea-CO2 fluxes in the tropical Pacific, revealed by an ocean physical-biogeochemical model 期刊论文
CLIMATE DYNAMICS, 2019, 53: 3985-4004
作者:  Tian, Feng;  Zhang, Rong-Hua;  Wang, Xiujun
收藏  |  浏览/下载:24/0  |  提交时间:2019/11/27
Tropical Pacific  Interdecadal variability of air-sea CO2 fluxes  Regime shift  Wind speed  Ocean physicalbiogeochemical model  
Process-based evaluation of the VALUE perfect predictor experiment of statistical downscaling methods 期刊论文
INTERNATIONAL JOURNAL OF CLIMATOLOGY, 2019, 39 (9) : 3868-3893
作者:  Soares, P. M. M.;  Maraun, D.;  Brands, S.;  Jury, M. W.;  Gutierrez, J. M.;  San-Martin, D.;  Hertig, E.;  Huth, R.;  Vozila, A. Belusic;  Cardoso, Rita M.;  Kotlarski, S.;  Drobinski, P.;  Obermann-Hellhund, A.
收藏  |  浏览/下载:11/0  |  提交时间:2019/11/27
bias adjustment  climate change  downscaling  model output statistics  perfect prognosis  regime-oriented  
Investigation Parameters for Sound Induced by Fluid Displacement in Rock Samples 期刊论文
WATER RESOURCES RESEARCH, 2019, 55 (5) : 4220-4232
作者:  Mikhailov, Dmitry;  Sergeev, Stanislav
收藏  |  浏览/下载:14/0  |  提交时间:2019/11/26
acoustic emission  displacement  porous medium  flow regime  laboratory study  mathematical model  
Secular variation of rainfall regime in the central region of Argentina 期刊论文
ATMOSPHERIC RESEARCH, 2018, 213: 196-210
作者:  de La Casa, Antonio C.;  Ovando, Gustavo G.;  Diaz, Guillermo J.
收藏  |  浏览/下载:9/0  |  提交时间:2019/04/09
Rainfall regime  Climate change  Trend  Linear model  Periodic model