14,326 research outputs found
From Quark Gluon Plasma to a Perfect Fluid of Quarks and Beyond
With high energy heavy ion collisions one tries to create a new forms of
matter that is similar to the one present at the birth of our Universe. Recent
development on flow pattern, initial energy-density and freeze-out temperature
shows that most likely this new form of matter is in a deconfined state, has
colored degrees of freedom and is more fluid-like than gas-like. In present
paper we calculate estimations on the physical properties of this new-old
matter.Comment: 10 pages, 5 figures, to appear in the proceedings of the 44th
International School of Subnuclear Physics, Erice, Sicily, 29 August - 7
September 200
The psychometric properties of ADCS - activities of daily living inventory and comparison of different ADL scores
Several multi-item activities of daily living (ADL) scales have been developed for assessment of functional status of patients with Alzheimer’s Disease (AD) in the last few decades. A disadvantage of the large number of scales is that scores of different ADL scales cannot be compared directly with each other. ADL scales which are used by McNamee’s (Townsend's disability scale) and Hill’s (Medicare Beneficiary definitions and Katz index of ADL) provide suitable tools for modelling the cost-effectiveness of different treatments in patients with Alzheimer’s disease, since they report empirical results about the relationship between the degree of functional impairment (healthcare costs) and the prevalence of institutionalisation.
The IDEAL trial examines the efficacy of Exelon Patch with the ADCS - Activities of Daily Living Inventory (ADCS-ADL). This ADL instrument is not directly comparable to the ADL scales used by McNamee and Hill. However, the use of the ADL scale from the IDEAL study to predict the prevalence of institutionalisation with scales by Hill and McNamee would be desirable. Because of the generic nature of the ADL construct, and considering the fact that these well validated ADL instruments identify the main physical impairments and functional disabilities in Alzheimer's disease, we should expect high overlap in item content between different ADL instruments. The high overlap in item content between instruments, and the similar wording and scoring criteria, makes it possible to pair each impairment with another. The intention of this study was to establish the link between these ADL scales in order to provide appropriate conditions for further economic analyses on the dataset provided by the IDEAL study
Global existence and exponential decay for hyperbolic dissipative relativistic fluid theories
We consider dissipative relativistic fluid theories on a fixed flat, compact,
globally hyperbolic, Lorentzian manifold. We prove that for all initial data in
a small enough neighborhood of the equilibrium states (in an appropriate
Sobolev norm), the solutions evolve smoothly in time forever and decay
exponentially to some, in general undetermined, equilibrium state. To prove
this, three conditions are imposed on these theories. The first condition
requires the system of equations to be symmetric hyperbolic, a fundamental
requisite to have a well posed and physically consistent initial value
formulation. The second condition is a generic consequence of the entropy law,
and is imposed on the non principal part of the equations. The third condition
is imposed on the principal part of the equations and it implies that the
dissipation affects all the fields of the theory. With these requirements we
prove that all the eigenvalues of the symbol associated to the system of
equations of the fluid theory have strictly negative real parts, which in fact,
is an alternative characterization for the theory to be totally dissipative.
Once this result has been obtained, a straight forward application of a general
stability theorem due to Kreiss, Ortiz, and Reula, implies the results above
mentioned.Comment: 10 pages, Late
Quantum Computing on Lattices using Global Two-Qubit Gate
We study the computation power of lattices composed of two dimensional
systems (qubits) on which translationally invariant global two-qubit gates can
be performed. We show that if a specific set of 6 global two qubit gates can be
performed, and if the initial state of the lattice can be suitably chosen, then
a quantum computer can be efficiently simulatedComment: 9 page
Operator algebra quantum homogeneous spaces of universal gauge groups
In this paper, we quantize universal gauge groups such as SU(\infty), as well
as their homogeneous spaces, in the sigma-C*-algebra setting. More precisely,
we propose concise definitions of sigma-C*-quantum groups and sigma-C*-quantum
homogeneous spaces and explain these concepts here. At the same time, we put
these definitions in the mathematical context of countably compactly generated
spaces as well as C*-compact quantum groups and homogeneous spaces. We also
study the representable K-theory of these spaces and compute it for the quantum
homogeneous spaces associated to the universal gauge group SU(\infty).Comment: 14 pages. Merged with [arXiv:1011.1073
Extreme Supernova Models for the Superluminous Transient ASASSN-15lh
The recent discovery of the unprecedentedly superluminous transient
ASASSN-15lh (or SN 2015L) with its UV-bright secondary peak challenges all the
power-input models that have been proposed for superluminous supernovae. Here
we examine some of the few viable interpretations of ASASSN-15lh in the context
of a stellar explosion, involving combinations of one or more power inputs. We
model the lightcurve of ASASSN-15lh with a hybrid model that includes
contributions from magnetar spin-down energy and hydrogen-poor circumstellar
interaction. We also investigate models of pure circumstellar interaction with
a massive hydrogen-deficient shell and discuss the lack of interaction features
in the observed spectra. We find that, as a supernova ASASSN-15lh can be best
modeled by the energetic core-collapse of a ~40 Msun star interacting with a
hydrogen-poor shell of ~20 Msun. The circumstellar shell and progenitor mass
are consistent with a rapidly rotating pulsational pair-instability supernova
progenitor as required for strong interaction following the final supernova
explosion. Additional energy injection by a magnetar with initial period of 1-2
ms and magnetic field of 0.1-1 x 10^14 G may supply the excess luminosity
required to overcome the deficit in single-component models, but this requires
more fine-tuning and extreme parameters for the magnetar, as well as the
assumption of efficient conversion of magnetar energy into radiation. We thus
favor a single-input model where the reverse shock formed in a strong SN
ejecta-CSM interaction following a very powerful core-collapse SN explosion can
supply the luminosity needed to reproduce the late-time UV-bright plateau.Comment: 8 pages, 3 figure
On the Explanation of the Paramagnetic Meissner Effect in Superconductor/Ferromagnet Heterostructures
An increase of the magnetic moment in superconductor/ferromagnet (S/F)
bilayers V(40nm)/F [FFe(1,3nm), Co(3nm), Ni(3nm)] was observed using SQUID
magnetometry upon cooling below the superconducting transition temperature Tc
in magnetic fields of 10 Oe to 50 Oe applied parallel to the sample surface. A
similar increase, often called the paramagnetic Meissner effect (PME), was
observed before in various superconductors and superconductor/ferromagnet
systems. To explain the PME effect in the presented S/F bilayers a model based
on a row of vortices located at the S/F interface is proposed. According to the
model the magnetic moment induced below Tc consists of the paramagnetic
contribution of the vortex cores and the diamagnetic contribution of the
vortex-free region of the S layer. Since the thickness of the S layer is found
to be 3-4 times less than the magnetic field penetration depth, this latter
diamagnetic contribution is negligible. The model correctly accounts for the
sign, the approximate magnitude and the field dependence of the paramagnetic
and the Meissner contributions of the induced magnetic moment upon passing the
superconducting transition of a ferromagnet/superconductor bilayer
The Initial-Boundary Value Problem in General Relativity
In this article we summarize what is known about the initial-boundary value
problem for general relativity and discuss present problems related to it.Comment: 11 pages, 2 figures. Contribution to a special volume for Mario
Castagnino's seventy fifth birthda
- …