92,502 research outputs found
Integrality of Homfly (1,1)-tangle invariants
Given an invariant J(K) of a knot K, the corresponding (1,1)-tangle invariant
J'(K)=J(K)/J(U) is defined as the quotient of J(K) by its value J(U) on the
unknot U.
We prove here that J' is always an integer 2-variable Laurent polynomial when
J is the Homfly satellite invariant determined by decorating K with any
eigenvector of the meridian map in the Homfly skein of the annulus.
Specialisation of the 2-variable polynomials for suitable choices of
eigenvector shows that the (1,1)-tangle irreducible quantum sl(N) invariants of
K are integer 1-variable Laurent polynomials.Comment: 10 pages, including several interspersed figure
Observing the sky at extremely high energies with the Cherenkov Telescope Array: Status of the GCT project
The Cherenkov Telescope Array is the main global project of ground-based
gamma-ray astronomy for the coming decades. Performance will be significantly
improved relative to present instruments, allowing a new insight into the
high-energy Universe [1]. The nominal CTA southern array will include a
sub-array of seventy 4 m telescopes spread over a few square kilometers to
study the sky at extremely high energies, with the opening of a new window in
the multi-TeV energy range. The Gamma-ray Cherenkov Telescope (GCT) is one of
the proposed telescope designs for that sub-array. The GCT prototype recorded
its first Cherenkov light on sky in 2015. After an assessment phase in 2016,
new observations have been performed successfully in 2017. The GCT
collaboration plans to install its first telescopes and cameras on the CTA site
in Chile in 2018-2019 and to contribute a number of telescopes to the
subsequent CTA production phase.Comment: 8 pages, 7 figures, ICRC201
Intrinsic limits governing MBE growth of Ga-assisted GaAs nanowires on Si(111)
Diffusion-enhanced and desorption-limited growth regimes of Ga-assisted GaAs
nanowires were identified. In the latter regime, the number of vertical NWs
with a narrow length distribution was increased by raising the growth
temperature. The maximum axial growth rate; which can be quantified by the
supplied rate of As atoms, is achieved when a dynamical equilibrium state is
maintained in Ga droplets i.e. the number of impinging As atoms on the droplet
surface is equivalent to that of direct deposited Ga atoms combining with the
diffusing ones. The contribution of Ga diffusion to the wire growth was
evidenced by the diameter-dependent NW axial growth rate
Sticky Particles and Stochastic Flows
Gaw\c{e}dzki and Horvai have studied a model for the motion of particles
carried in a turbulent fluid and shown that in a limiting regime with low
levels of viscosity and molecular diffusivity, pairs of particles exhibit the
phenomena of stickiness when they meet. In this paper we characterise the
motion of an arbitrary number of particles in a simplified version of their
model
Dipolar Dark Matter and Dark Energy
In previous work [L. Blanchet and A. Le Tiec, Phys. Rev. D 78, 024031
(2008)], a model of dark matter and dark energy based on the concept of
gravitational polarization was investigated. This model was shown to recover
the concordance cosmological scenario (Lambda-CDM) at cosmological scales, and
the phenomenology of the modified Newtonian dynamics (MOND) at galactic scales.
In this article we prove that the model can be formulated with a simple and
physically meaningful matter action in general relativity. We also provide
alternative derivations of the main results of the model, and some details on
the variation of the action.Comment: 11 pages, 2 figures; minor stylistic corrections, added references,
added appendix; to appear in Phys. Rev.
Bayesian Statistics at Work: the Troublesome Extraction of the CKM Phase alpha
In Bayesian statistics, one's prior beliefs about underlying model parameters
are revised with the information content of observed data from which, using
Bayes' rule, a posterior belief is obtained. A non-trivial example taken from
the isospin analysis of B-->PP (P = pi or rho) decays in heavy-flavor physics
is chosen to illustrate the effect of the naive "objective" choice of flat
priors in a multi-dimensional parameter space in presence of mirror solutions.
It is demonstrated that the posterior distribution for the parameter of
interest, the phase alpha, strongly depends on the choice of the
parameterization in which the priors are uniform, and on the validity range in
which the (un-normalizable) priors are truncated. We prove that the most
probable values found by the Bayesian treatment do not coincide with the
explicit analytical solution, in contrast to the frequentist approach. It is
also shown in the appendix that the alpha-->0 limit cannot be consistently
treated in the Bayesian paradigm, because the latter violates the physical
symmetries of the problem.Comment: 17 pages, 10 figure
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