3,745 research outputs found
Constrained dynamics of a polymer ring enclosing a constant area
The dynamics of a polymer ring enclosing a constant {\sl algebraic} area is
studied. The constraint of a constant area is found to couple the dynamics of
the two Cartesian components of the position vector of the polymer ring through
the Lagrange multiplier function which is time dependent. The time dependence
of the Lagrange multiplier is evaluated in a closed form both at short and long
times. At long times, the time dependence is weak, and is mainly governed by
the inverse of the first mode of the area. The presence of the constraint
changes the nature of the relaxation of the internal modes. The time
correlation of the position vectors of the ring is found to be dominated by the
first Rouse mode which does not relax even at very long times. The mean square
displacement of the radius vector is found to be diffusive, which is associated
with the rotational diffusion of the ring.Comment: 6 page
Active ageing – Enhancing digital literacies in elderly citizens
Being digital and information literate is crucial in nowadays society, although not every citizen has the necessary means and resources to achieve these skills, especially the elderly ones. Therefore it is necessary to develop ways to help them to enhance their digital and information competences. In this paper we will present an ongoing project that was designed and implemented with the goal to provide elderly citizens with the necessary skills of a networked society, contributing for an active ageing. The methods used were based on a set of hands on workshops delivered by a team of voluntary students and teacher, with the help of collaborators from a nursing home. The workshops were developed accordingly with the detected needs of a group of elderly citizens, based on the answers of an implemented questionnaire.info:eu-repo/semantics/publishedVersio
Possible persistent current in a ring made of the perfect crystalline insulator
A mesoscopic conducting ring pierced by magnetic flux is known to support the
persistent electron current. Here we propose possibility of the persistent
current in the ring made of the perfect crystalline insulator. We consider a
ring-shaped lattice of one-dimensional "atoms" with a single energy level. We
express the Bloch states in the lattice as a linear combination of atomic
orbitals. The discrete energy level splits into the energy band which serves as
a simple model of the valence band. We show that the insulating ring (with the
valence band fully filled by electrons) supports a nonzero persistent current,
because each atomic orbital overlaps with its own tail when making one loop
around the ring. In the tight-binding limit only the neighboring orbitals
overlap. In that limit the persistent current at full filling becomes zero
which is a standard result.Comment: Conference proceedings. Accepted for publication in Physica
A law of the iterated logarithm sublinear expectations
In this paper, motivated by the notion of independent identically distributed
(IID) random variables under sub-linear expectations initiated by Peng, we
investigate a law of the iterated logarithm for capacities. It turns out that
our theorem is a natural extension of the Kolmogorov and the Hartman-Wintner
laws of the iterated logarithm
Recursive computation of the invariant measure of a stochastic differential equation driven by a L\'evy process
We investigate some recursive procedures based on an exact or ``approximate''
Euler scheme with decreasing step in vue to computation of invariant measures
of solutions to S.D.E. driven by a L\'evy process. Our results are valid for a
large class of S.D.E. that can be governed by L\'evy processes with few moments
or can have a weakly mean-reverting drift, and permit to find again the a.s.
C.L.T for stable processes
Macroscopic Anisotropy and Symmetry Breaking in the Pyrochlore Antiferromagnet GdTiO}
In the Heisenberg antiferromagnet , the exchange interactions
are geometrically frustrated by the pyrochlore lattice structure. This ESR
study reveals a strong temperature dependent anisotropy with respect to a [111]
body diagonal below a temperature K, despite the spin only nature of
the ion. Anisotropy and symmetry breaking can nevertheless appear
through the superexchange interaction. The presence of short range planar
correlation restricted to specific Kagom\'{e} planes is sufficient to explain
the two ESR modes studied in this work.Comment: 4 pages, 5 figure
Decoherence processes in a current biased dc SQUID
A current bias dc SQUID behaves as an anharmonic quantum oscillator
controlled by a bias current and an applied magnetic flux. We consider here its
two level limit consisting of the two lower energy states | 0 \right> and |
1 \right>. We have measured energy relaxation times and microwave absorption
for different bias currents and fluxes in the low microwave power limit.
Decoherence times are extracted. The low frequency flux and current noise have
been measured independently by analyzing the probability of current switching
from the superconducting to the finite voltage state, as a function of applied
flux. The high frequency part of the current noise is derived from the
electromagnetic environment of the circuit. The decoherence of this quantum
circuit can be fully accounted by these current and flux noise sources.Comment: 4 pages, 4 figure
Anyons, group theory and planar physics
Relativistic and nonrelativistic anyons are described in a unified formalism
by means of the coadjoint orbits of the symmetry groups in the free case as
well as when there is an interaction with a constant electromagnetic field. To
deal with interactions we introduce the extended Poincar\'e and Galilei Maxwell
groups.Comment: 22 pages, journal reference added, bibliography update
Hopf instantons, Chern-Simons vortices, and Heisenberg ferromagnets
The dimensional reduction of the three-dimensional fermion-Chern-Simons model
(related to Hopf maps) of Adam et el. is shown to be equivalent to (i) either
the static, fixed--chirality sector of our non-relativistic spinor-Chern-Simons
model in 2+1 dimensions, (ii) or a particular Heisenberg ferromagnet in the
plane.Comment: 4 pages, Plain Tex, no figure
Scalar and vector meson exchange in V->P0P0gamma decays
The scalar contributions to the radiative decays of light vector mesons into
a pair of neutral pseudoscalars, , are studied within the
framework of the Linear Sigma Model. This model has the advantage of
incorporating not only the scalar resonances in an explicit way but also the
constraints required by chiral symmetry. The experimental data on
, ,
and are satisfactorily accommodated in our
framework. Theoretical predictions for ,
, and the ratio are also given.Comment: 42 pages, 11 figures. A new paragraph explaining the seminal
contribution of Ref. [19] is adde
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