780 research outputs found
Statistical networks emerging from link-node interactions
We study a model for a statistical network formed by interactions between its
nodes and links. Each node can be in one of two states (Ising spin up or down)
and the node-link interaction facilitates linking between the like nodes. For
high temperatures the influence of the nodes on the links can be neglected, and
we get the Ising ferromagnet on the random (Erdos-Renyi) graph. For low
temperatures the nodes get spontaneously ordered. Due to this, the connectivity
of the network enhances and links having a common node are correlated. The
emerged network is clustered. The node-link interaction shifts the percolation
threshold of the random graph to much smaller values, and the very percolation
transition can become of the first order: the giant cluster coexist with the
unconnected phase leading to bistability and hysteresis. The model can be
applied to the striction phenomena in magnets and to studying opinion formation
in the sociophysical context.Comment: 4 pages, 1 figur
Symmetric photon-photon coupling by atoms with Zeeman-split sublevels
We propose a simple scheme for highly efficient nonlinear interaction between
two weak optical fields. The scheme is based on the attainment of
electromagnetically induced transparency simultaneously for both fields via
transitions between magnetically split F=1 atomic sublevels, in the presence of
two driving fields. Thereby, equal slow group velocities and symmetric
cross-coupling of the weak fields over long distances are achieved. By simply
tuning the fields, this scheme can either yield giant cross-phase modulation or
ultrasensitive two-photon switching.Comment: Modified scheme, 4 pages, 1 figur
Magneto-optical rotation and cross-phase modulation via coherently driven tripod atoms
We study the interaction of a weak probe field, having two orthogonally
polarized components, with an optically dense medium of four-level atoms in a
tripod configuration. In the presence of a coherent driving laser,
electromagnetically induced transparency is attained in the medium,
dramatically enhancing its linear as well as nonlinear dispersion while
simultaneously suppressing the probe field absorption. We present the
semiclassical and fully quantum analysis of the system. We propose an
experimentally feasible setup that can induce large Faraday rotation of the
probe field polarization and therefore be used for ultra-sensitive optical
magnetometry. We then study the Kerr nonlinear coupling between the two
components of the probe, demonstrating a novel regime of symmetric, extremely
efficient cross-phase modulation, capable of fully entangling two single-photon
pulses. This scheme may thus pave the way to photon-based quantum information
applications, such as deterministic all-optical quantum computation, dense
coding and teleportation.Comment: Corrected typo
Work fluctuation theorems for harmonic oscillators
The work fluctuations of an oscillator in contact with a thermostat and
driven out of equilibrium by an external force are studied experimentally and
theoretically within the context of Fluctuation Theorems (FTs). The oscillator
dynamics is modeled by a second order Langevin equation. Both the transient and
stationary state fluctuation theorems hold and the finite time corrections are
very different from those of a first order Langevin equation. The periodic
forcing of the oscillator is also studied; it presents new and unexpected short
time convergences. Analytical expressions are given in all cases
Attitudes, practices and beliefs towards worksite smoking among administrators of private and public enterprises in Armenia
As one of the first studies to investigate smoking-related worksite practices, attitudes and beliefs in former Soviet countries, these findings provide insight into law enforcement processes for economies in transition. The study team conducted focus group discussions with worksite administrators to explore their beliefs, attitudes and practices related to worksite smoking. These findings guided development of a quantitative instrument to collect more representative data on the same issues. Research revealed widespread confusion between the concepts of worksite smoking restrictions and smoke-free workplaces. Public awareness campaigns that promote promulgation and enforcement of worksite smoking regulations could increase employee demand for smoke-free worksites
Classification of Singular Fibres on Rational Elliptic Surfaces in Characteristic Three
We determine and list all possible configurations of singular fibres on
rational elliptic surfaces in characteristic three. In total, we find that 267
distinct configurations exist. This result complements Miranda and Persson's
classification in characteristic zero, and Lang's classification in
characteristic two.Comment: 40 Pages. Minor typos correcte
Anomalous latent heat in non-equilibrium phase transitions
We study first-order phase transitions in a two-temperature system, where due
to the time-scale separation all the basic thermodynamical quantities (free
energy, entropy, etc) are well-defined. The sign of the latent heat is found to
be counterintuitive: it is positive when going from the phase where the
temperatures and the entropy are higher to the one where these quantities are
lower. The effect exists only out of equilibrium and requires conflicting
interactions. It is displayed on a lattice gas model of ferromagnetically
interacting spin-1/2 particles.Comment: 4 pages, 2 figure
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