602 research outputs found
An accelerator mode based technique for studying quantum chaos
We experimentally demonstrate a method for selecting small regions of phase
space for kicked rotor quantum chaos experiments with cold atoms. Our technique
uses quantum accelerator modes to selectively accelerate atomic wavepackets
with localized spatial and momentum distributions. The potential used to create
the accelerator mode and subsequently realize the kicked rotor system is formed
by a set of off-resonant standing wave light pulses. We also propose a method
for testing whether a selected region of phase space exhibits chaotic or
regular behavior using a Ramsey type separated field experiment.Comment: 5 pages, 3 figures, some modest revisions to previous version (esp.
to the figures) to aid clarity; accepted for publication in Physical Review A
(due out on January 1st 2003
Experimental observation of high-order quantum accelerator modes.
Using a freely falling cloud of cold cesium atoms periodically kicked by pulses from a vertical standing wave of laser light, we present the first experimental observation of high-order quantum accelerator modes. This confirms the recent prediction by Fishman, Guarneri, and Rebuzzini [Phys. Rev. Lett.10.1103/PhysRevLett.89.084101 89, 084101 (2002)]. We also show how these accelerator modes can be identified with the stable regions of phase space in a classical-like chaotic system, despite their intrinsically quantum origin
UK sustainable drainage systems: past, present and future
Urban drainage has developed from an engineering discipline, concerned principally with public health and safety outcomes, into a multifaceted vision linking drainage with environmental and wider social and economic imperatives to deliver multifunctional outcomes. UK attention is too often focused on surface water as ‘a problem’, despite international progress and initiatives showing that an ‘opportunity-centred’ approach needs to be taken. Sustainable drainage systems, or ‘Suds’, can, when they are part of an integrated approach to water management, cost-effectively provide many benefits beyond management of water quality and quantity. New tools are available that can design Suds for maximum value to society but this requires greater collaboration across disciplines to seize all of the opportunities available. This paper introduces those tools and a roadmap for their use, including guidance, design objectives and criteria for maximising benefits. These new supporting tools and guidance can help to provide a business case for greater use of Suds in future
Modelling Housing Market Fundamentals and the Response to Economic and Political Events: Empirical Evidence from Kuwait
Kuwait provides an interesting housing market to examine given its place as a major oil producer, its sensitivity to geo-political events and its unusual demographic characteristics. This paper firstly models the dynamics of the Kuwaiti housing market, using an errorcorrection framework. The findings highlight that the market is relatively volatile, with evidence of mean-reverting behaviour. The paper also examines the response of the market to seven regional and local events. Of particular interest is that the one event that results in a consistent significant response is domestic legislation directly concerned with housing. This has a far greater impact than local or regional geo-political events
Paleo-denudation rates suggest variations in runoff drove aggradation during last glacial cycle, Crete, Greece
Fluvial aggradation and incision are often linked to Quaternary climate cycles, but it usually remains unclear whether variations in runoff or sediment supply or both drive channel response to climate variability. Here we quantify sediment supply with paleo-denudation rates and provide geochronological constraints on aggradation and incision from the Sfakia and Elafonisi alluvial-fan sequences in Crete, Greece. We report seven optically stimulated luminescence (OSL)and ten radiocarbon ages, eight 10Be,and eight 36Cl denudation rates from modern channeland terrace sediments. For five samples, 10Be and 36Cl were measured on the same sample by measuring 10Be on chert and 36Cl on calcite. Results indicate relatively steady denudation rates throughout the past 80kyr, but the aggradation and incision history indicates a link with climate shifts. At the Elafonisi fan, we identify four periods of aggradation coinciding with Marine Isotope Stages (MIS) 2, 4, 5a/b, and likely 6, and three periods of incision coinciding with MIS 1, 3, and likely 5e. At the Sfakia fan, rapid aggradation occurred during MIS 2 and 4,followed by incision during MIS 1. Nearby climate and vegetation records show that MIS 2, 4, and 6 stadials were characterized by cold and dry climates with sparse vegetation, whereas forest cover and more humid conditions prevailed during MIS 1, 3, and 5. Our data thus suggest that past changes in climate had little effect on landscape-wide denudation rates but exerted a strong control on the aggradation-incision behaviour of alluvial channels on Crete. During glacial stages, we attribute aggradation to hillslope sediment release promoted by reduced vegetation cover and decreased runoff; conversely, incision occurred during relatively warm and wet stages due to increased runoff. In this landscape, past hydroclimate variations outcompeted changes in sediment supply as the primary driver of alluvial deposition and incision
Coherent Manipulation of Quantum Delta-kicked Dynamics: Faster-than-classical Anomalous Diffusion
Large transporting regular islands are found in the classical phase space of
a modified kicked rotor system in which the kicking potential is reversed after
every two kicks. The corresponding quantum system, for a variety of system
parameters and over long time scales, is shown to display energy absorption
that is significantly faster than that associated with the underlying classical
anomalous diffusion. The results are of interest to both areas of quantum chaos
and quantum control.Comment: 6 pages, 4 figures, to appear in Physical Review
Control of Dynamical Localization
Control over the quantum dynamics of chaotic kicked rotor systems is
demonstrated. Specifically, control over a number of quantum coherent phenomena
is achieved by a simple modification of the kicking field. These include the
enhancement of the dynamical localization length, the introduction of classical
anomalous diffusion assisted control for systems far from the semiclassical
regime, and the observation of a variety of strongly nonexponential lineshapes
for dynamical localization. The results provide excellent examples of
controlled quantum dynamics in a system that is classically chaotic and offer
new opportunities to explore quantum fluctuations and correlations in quantum
chaos.Comment: 9 pages, 7 figures, to appear in Physical Review
An updated measurement of the Hubble constant from near-infrared observations of Type Ia supernovae
We present a measurement of the Hubble constant () using type Ia
supernova (SNe Ia) in the near-infrared (NIR) from the recently updated sample
of SNe Ia in nearby galaxies with distances measured via Cepheid
period-luminosity relations by the SHOES project. We collect public
near-infrared photometry of up to 19 calibrator SNe Ia and further 57 SNe Ia in
the Hubble flow (), and directly measure their peak magnitudes in the
and band by Gaussian processes and spline interpolation. Calibrator
peak magnitudes together with Cepheid-based distances are used to estimate the
average absolute magnitude in each band, while Hubble-flow SNe are used to
constrain the zero-point intercept of the magnitude-redshift relation. Our
baseline result of is (stat) (syst) km s
Mpc in the band and (stat) (syst) km s
Mpc in the band, where the systematic uncertainties include the
standard deviation of up to 21 variations of the analysis, the 0.7\% distance
scale systematic from SHOES Cepheid anchors, a photometric zeropoint
systematic, and a cosmic variance systematic. Our final measurement represents
a measurement with a precision of 2.8\% in both bands. The variant with the
largest change in is when limiting the sample to SNe from CSP and CfA
programmes, noteworthy because these are the best calibrated, yielding
km s Mpc in both bands. We demonstrate stretch and
reddening corrections are still useful in the NIR to standardize SN Ia NIR peak
magnitudes. Based on our results, in order to improve the precision of the
measurement with SNe Ia in the NIR in the future, we would need to
increase the number of calibrator SNe Ia, be able to extend the
Hubble-Lema\^itre diagram to higher-z, and include standardization procedures
to help reducing the NIR intrinsic scatter.Comment: 15 pages, 8 figures. Accepted in A&
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