African University of Science and Technology: Recent submissions
Now showing items 641-660 of 4824
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Rapid mixing renders quantum dissipative systems stable
(APSPhysical Review A, 2015-04-09)The physics of many materials is modeled by quantum many-body systems with local interactions. If the model of the system is sensitive to noise from the environment, or small perturbations to the original interactions, ...
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Post-inflationary non-Gaussianities on the cosmic microwave background
(University of CambridgeDepartment of Applied Mathematics and Theoretical PhysicsTrinity Hall, 2015-06-30)The cosmic microwave background (CMB) provides unprecedented details about the history of our universe and helps to establish the standard model in modern cosmology. With the ongoing and future CMB observations, higher ...
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Unbounded number of channel uses may be required to detect quantum capacity
(NPGNature Communications, 2015-03-31)Transmitting data reliably over noisy communication channels is one of the most important applications of information theory, and is well understood for channels modelled by classical physics. However, when quantum effects ...
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Stability of local quantum dissipative systems
(SpringerCommunications in Mathematical Physics, 2015-04-07)Open quantum systems weakly coupled to the environment are modeled by completely positive, trace preserving semigroups of linear maps. The generators of such evolutions are called Lindbladians. In the setting of ...
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Plethora of transitions during breakup of liquid filaments
(PNASProceedings of the National Academy of Sciences, 2015-03-30)Thinning and breakup of liquid filaments are central to dripping of leaky faucets, inkjet drop formation, and raindrop fragmentation. As the filament radius decreases, curvature and capillary pressure, both inversely ...
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Stability analysis of matrix Wiener–Hopf factorization of Daniele–Khrapkov class and reliable approximate factorization
(Royal Society PublishingProceedings of the Royal Society of London A, 2015-05-06)This paper presents new stability results for matrix Wiener–Hopf factorization. The first part of the paper examines conditions for stability of Wiener–Hopf factorization in the Daniele–Khrapkov class. The second part of ...
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The relationship between a strip Wiener--Hopf problem and a line Riemann--Hilbert problem
(OUPIMA Journal of Applied Mathematics, 2015-03-31)In this paper, the Wiener–Hopf factorization problem is presented in a unified framework with the Riemann–Hilbert factorization. This allows to establish the exact relationship between the two types of factorization. In ...
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Liquid Ropes: A Geometrical Model for Thin Viscous Jet Instabilities
(APSPhysical Review Letters, 2015-04-30)Thin, viscous fluid threads falling onto a moving belt behave in a way reminiscent of a sewing machine, generating a rich variety of periodic stitchlike patterns including meanders, W patterns, alternating loops, and ...
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Lubricated viscous gravity currents
(CUPJournal of Fluid Mechanics, 2015-02-10)We present a theoretical and experimental study of viscous gravity currents lubricated by another viscous fluid from below. We use lubrication theory to model both layers as Newtonian fluids spreading under their own weight ...
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Constrained dynamics and higher derivative systems in modified gravity
(University of CambridgeDepartment of Applied Mathematics and Theoretical Physics, 2015-06-09)In this thesis, higher derivative theories and constrained dynamics are investigated in detail. In the first part of the thesis, we discuss how the Ostrogradski instability emerges in non-degenerate higher derivative ...
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Accelerated Gravitational Wave Parameter Estimation with Reduced Order Modeling
(APSPhysical Review Letters, 2015-02-20)Inferring the astrophysical parameters of coalescing compact binaries is a key science goal of the upcoming advanced LIGO-Virgo gravitational-wave detector network and, more generally, gravitational-wave astronomy. However, ...
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Early-time free-surface flow driven by a deforming boundary
(Cambridge University PressJournal of Fluid Mechanics, 2015-02-24)When a solid boundary deforms rapidly into a quiescent liquid layer, a flow is in- duced that can lead to jet formation. An asymptotic analytical solution is presented for this flow, driven by a solid boundary deforming ...
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Detecting pairwise correlations in spike trains: an objective comparison of methods and application to the study of retinal waves
(Society for NeuroscienceJournal of Neuroscience, 2014-10-22)Correlations in neuronal spike times are thought to be key to processing in many neural systems. Many measures have been proposed to summarize these correlations and of these the correlation index is widely used and is the ...
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On High-Frequency Sound Generated by Gust-Aerofoil Interaction in Shear Flow
(CUPJournal of Fluid Mechanics, 2015-02-04)A theoretical model is constructed to predict the far-field sound generated by high-frequency gust–aerofoil interaction in steady parallel shear flow, including the effects of aerofoil thickness. Our approach is to use ...
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Efficient mixing in stratified flows: experimental study of a Rayleigh-Taylor unstable interface within an otherwise stable stratification
(Cambridge University PressJournal of Fluid Mechanics, 2014-09-09)Boussinesq salt-water laboratory experiments of Rayleigh–Taylor instability (RTI) can achieve mixing efficiencies greater than 0.75 when the unstable interface is confined between two stable stratifications. This is much ...
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On the thermodynamic boundary conditions of a solidifying mushy layer with outflow
(CUPJournal of Fluid Mechanics, 2014-11-27)The free-boundary problem between a liquid region and a mushy layer (a reactive porous medium) must respect both thermodynamic and fluid dynamical considerations. We develop a steady two-dimensional forced-flow configuration ...
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A physically based parameterization of gravity drainage for sea-ice modelling
(Wiley on behalf of the American Geophysical UnionJournal of Geophysical Research: Oceans, 2014-09-02)We incorporate a physically derived parameterization of gravity drainage, in terms of a convective upwelling velocity, into a one-dimensional, thermodynamic sea- ice model of the kind currently used in coupled climate ...
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Vortex rings impinging on permeable boundaries
(Physics of Fluids, 2015-01-17)Experiments with vortex rings impinging permeable and solid boundaries are presented in order to investigate the influence of permeability. Utilizing Particle Image Velocimetry, we compared the behaviour of a vortex ring ...
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Redshifting of cosmological black bodies in BSBM varying-alpha theories
(APSPHYSICAL REVIEW D, 2014-12-04)We analyse the behaviour of black-body radiation in theories of electromagnetism which allow the electron charge and the fine structure constant to vary in space and time. We show that such theories can be expressed as ...
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Higher order corrections and unification in the minimal supersymmetric standard model: SOFTSUSY3.5
(ElsevierComputer Physics Communications, 2014-12-18)We explore the effects of three-loop minimal supersymmetric standard model renormalisation group equation terms and some leading two-loop threshold corrections on gauge and Yukawa unification: each being one loop higher ...
