African University of Science and Technology: Recent submissions
Now showing items 601-620 of 4823
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The third way to 3D gravity
(World ScientificInternational Journal of Modern Physics D, 2015-10-09)Consistency of Einstein’s gravitational field equation Gµν ∝ Tµν imposes a “conservation condition” on the T-tensor that is satisfied by (i) matter stress tensors, as a consequence of the matter equations of motion, and ...
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Dynamical analysis in scalar field cosmology
(APSPhysical Review D, 2015-06-23)We give a general method to find exact cosmological solutions for scalar-field dark energy in the presence of perfect fluids. We use the existence of invariant transformations for the Wheeler De Witt (WdW) equation. We ...
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Interpreting the CMS l+l-jj missing ET Excess with a Leptoquark Model
(APSPhysical Review D, 2015-06-29)We present a model of leptoquarks (LQs) with a significant partial branching ratio into an extra sector, taken to be a viable dark matter candidate, other than the canonical lepton and jets final state. For LQs with mass ...
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Hyperbolic Inflation in the Light of Planck 2015 data
(APSPhysical Review D, 2015-05-18)Rubano and Barrow have discussed the emergence of a dark energy, with late-time cosmic acceleration arising from a self-interacting homogeneous scalar field with a potential of hyperbolic power type. Here, we study the ...
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Singular Inflation
(APSPhysical Review D, 2015-04-08)We prove that a homogeneous and isotropic universe containing a scalar field with a power-law potential, V(ϕ)=Aϕ^n, with 0<n<1 and A>0 always develops a finite-time singularity at which the Hubble rate and its first ...
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New Singularities in Unexpected Places
(World ScientificInternational Journal of Modern Physics D, 2015-09-28)Spacetime singularities have been discovered which are physically much weaker than those predicted by the classical singularity theorems. Geodesics evolve through them and they only display infinities in the derivatives ...
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On the Einstein-Weyl and conformal self-duality equations
(AIP PublishingJournal of Mathematical Physics, 2015-08-03)The equations governing anti-self-dual and Einstein-Weyl conformal geometries can be regarded as ‘master dispersionless systems’ in four and three dimensions respectively. Their integrability by twistor methods has been ...
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Multi-timescale analysis of phase transitions in precessing black-hole binaries
(American Physical SocietyPhysical Review D, 2015)The dynamics of precessing binary black holes (BBHs) in the post-Newtonian regime has a strong timescale hierarchy: the orbital timescale is very short compared to the spin-precession timescale which, in turn, is much ...
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Symmetric polynomials in information theory: entropy and subentropy
(AIP PublishingJournal of Mathematical Physics, 2015-06-12)Entropy and other fundamental quantities of information theory are customarily expressed and manipulated as functions of probabilities. Here we study the entropy H and subentropy Q as functions of the elementary symmetric ...
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Anatomy of the ATLAS diboson anomaly
(2015-08-19)We perform a general analysis of new physics interpretations of the recent ATLAS diboson excesses over Standard Model expectations in LHC Run I collisions. Firstly, we estimate a likelihood function in terms of the truth ...
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Vortex-ring-induced stratified mixing
(Cambridge University PressJournal of Fluid Mechanics, 2015-09-16)There is tantalizing evidence that some mechanically driven stratified flows tend towards a state of constant mixing efficiency. We provide insight into the energy balance leading to the constant mixing efficiency and ...
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Non-relativistic twistor theory and Newton-Cartan geometry
(SpringerCommunications in Mathematical Physics, 2016-01-14)We develop a non-relativistic twistor theory, in which Newton-Cartan structures of Newtonian gravity correspond to complex three-manifolds with a four-parameter family of rational curves with normal bundle O ⊕ O(2). We ...
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Quantum Conditional Mutual Information, Reconstructed States, and State Redistribution
(APSPhysical Review Letters, 2015-06-29)We give two strengthenings of an inequality for the quantum conditional mutual information of a tripartite quantum state recently proved by Fawzi and Renner, connecting it with the ability to reconstruct the state from its ...
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Superadditivity of private information for any number of uses of the channel
(APSPhysical Review Letters, 2015-07-20)The quantum capacity of a quantum channel is always smaller than the capacity of the channel for private communication. Both quantities are given by the infinite regularization of the coherent and the private information, ...
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Uniqueness of the Kerr-de Sitter spacetime as an algebraically special solution in five dimensions
(SpringerCommunications in Mathematical Physics, 2015-08-20)We determine the most general solution of the five-dimensional vacuum Einstein equation, allowing for a cosmological constant, with (i) a Weyl tensor that is type II or more special in the classification of Coley et al., ...
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The structure and stability of vortices in astrophysical discs
(University of CambridgeDepartment of Applied Mathematics and Theoretical Physics, 2015-10-06)This thesis finds that vortex instabilities are not necessarily a barrier to their potential as sites for planetesimal formation. It is challenging to build planetesimals from dust within the lifetime of a protoplanetary disc ...
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On the meaning of mixing efficiency for buoyancy driven mixing in stratified turbulent flows
(Cambridge University PressJournal of Fluid Mechanics, 2015-09-17)The concept of a mixing efficiency is widely used to relate the amount of irreversible diabatic mixing in a stratified flow to the amount of energy available to support mixing. This common measure of mixing in a flow is ...
