621 research outputs found
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Multimode Dynamics and Emergence of a Characteristic Length Scale in a One-Dimensional Quantum System
We study the nonequilibrium dynamics of a coherently split one-dimensional Bose gas by measuring the full probability distribution functions of matter-wave interference. Observing the system on different length scales allows us to probe the dynamics of excitations on different energy scales, revealing two distinct length-scale-dependent regimes of relaxation. We measure the crossover length scale separating these two regimes and identify it with the prethermalized phase-correlation length of the system. Our approach enables a direct observation of the multimode dynamics characterizing one-dimensional quantum systems.Physic
Many-body localization and thermalization in the full probability distribution function of observables
We investigate the relation between thermalization following a quantum quench
and many-body localization in quasiparticle space in terms of the long-time
full distribution function of physical observables. In particular, expanding on
our recent work [E. Canovi {\em et al.}, Phys. Rev. B {\bf 83}, 094431 (2011)],
we focus on the long-time behavior of an integrable XXZ chain subject to an
integrability-breaking perturbation. After a characterization of the breaking
of integrability and the associated localization/delocalization transition
using the level spacing statistics and the properties of the eigenstates, we
study the effect of integrability-breaking on the asymptotic state after a
quantum quench of the anisotropy parameter, looking at the behavior of the full
probability distribution of the transverse and longitudinal magnetization of a
subsystem. We compare the resulting distributions with those obtained in
equilibrium at an effective temperature set by the initial energy. We find
that, while the long time distribution functions appear to always agree {\it
qualitatively} with the equilibrium ones, {\it quantitative} agreement is
obtained only when integrability is fully broken and the relevant eigenstates
are diffusive in quasi-particle space.Comment: 18 pages, 11 figure
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Prethermalization Revealed by the Relaxation Dynamics of Full Distribution Functions
We detail the experimental observation of the non-equilibrium many-body phenomenon prethermalization. We study the dynamics of a rapidly and coherently split one-dimensional Bose gas. An analysis based on the use of full quantum mechanical probability distributions of matter wave interference contrast reveals that the system evolves toward a quasi-steady state. This state, which can be characterized by an effective temperature, is not the final thermal equilibrium state. We compare the evolution of the system to an integrable Tomonaga–Luttinger liquid model, and show that the system dephases to a prethermalized state rather than undergoing thermalization toward a final thermal equilibrium state.Physic
Impact of droughts on the carbon cycle in European vegetation : a probabilistic risk analysis using six vegetation models
Peer reviewedPublisher PD
Fine-suspended sediment and water budgets for a large, seasonally dry tropical catchment: Burdekin River catchment, Queensland, Australia
The Burdekin River catchment (~130,400 km2) is a seasonally dry tropical catchment located in north-east Queensland, Australia. It is the single largest source of suspended sediment to the Great Barrier Reef (GBR). Fine sediments are a threat to ecosystems on the GBR where they contribute to elevated turbidity (reduced light), sedimentation stress, and potential impacts from the associated nutrients. Suspended sediment data collected over a 5 year period were used to construct a catchment-wide sediment source and transport budget. The Bowen River tributary was identified as the major source of end-of-river suspended sediment export, yielding an average of 530 t km−2 yr−1 during the study period. Sediment trapping within a large reservoir (1.86 million ML) and the preferential transport of clays and fine silts downstream of the structure were also examined. The data reveal that the highest clay and fine silt loads—which are of most interest to environmental managers of the GBR—are not always sourced from areas that yield the largest total suspended sediment load (i.e., all size fractions). Our results demonstrate the importance of incorporating particle size into catchment sediment budget studies undertaken to inform management decisions to reduce downstream turbidity and sedimentation. Our data on sediment source, reservoir influence, and subcatchment and catchment yields will improve understandings of sediment dynamics in other tropical catchments, particularly those located in seasonally wet-dry tropical savannah/semiarid climates. The influence of climatic variability (e.g., drought/wetter periods) on annual sediment loads within large seasonally dry tropical catchments is also demonstrated by our data
Manipulation and removal of defects in spontaneous optical patterns
Defects play an important role in a number of fields dealing with ordered
structures. They are often described in terms of their topology, mutual
interaction and their statistical characteristics. We demonstrate theoretically
and experimentally the possibility of an active manipulation and removal of
defects. We focus on the spontaneous formation of two-dimensional spatial
structures in a nonlinear optical system, a liquid crystal light valve under
single optical feedback. With increasing distance from threshold, the
spontaneously formed hexagonal pattern becomes disordered and contains several
defects. A scheme based on Fourier filtering allows us to remove defects and to
restore spatial order. Starting without control, the controlled area is
progressively expanded, such that defects are swept out of the active area.Comment: 4 pages, 4 figure
Проблема правової культури в історії філософсько-педагогічної думки
(uk) Стаття присвячена проблемі правової культури в історії філософсько-педагогічної думки
Quantum Quench in the Transverse Field Ising chain I: Time evolution of order parameter correlators
We consider the time evolution of order parameter correlation functions after
a sudden quantum quench of the magnetic field in the transverse field Ising
chain. Using two novel methods based on determinants and form factor sums
respectively, we derive analytic expressions for the asymptotic behaviour of
one and two point correlators. We discuss quenches within the ordered and
disordered phases as well as quenches between the phases and to the quantum
critical point. We give detailed account of both methods.Comment: 65 pages, 21 figures, some typos correcte
Coral record of southeast Indian Ocean marine heatwaves with intensified Western Pacific temperature gradient
Increasing intensity of marine heatwaves has caused widespread mass coral bleaching events, threatening the integrity and functional diversity of coral reefs. Here we demonstrate the role of inter-ocean coupling in amplifying thermal stress on reefs in the poorly studied southeast Indian Ocean (SEIO), through a robust 215-year (1795-2010) geochemical coral proxy sea surface temperature (SST) record. We show that marine heatwaves affecting the SEIO are linked to the behaviour of the Western Pacific Warm Pool on decadal to centennial timescales, and are most pronounced when an anomalously strong zonal SST gradient between the western and central Pacific co-occurs with strong La Niña's. This SST gradient forces large-scale changes in heat flux that exacerbate SEIO heatwaves. Better understanding of the zonal SST gradient in the Western Pacific is expected to improve projections of the frequency of extreme SEIO heatwaves and their ecological impacts on the important coral reef ecosystems off Western Australia
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