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Relaxation Of Brownian Particles In A Gravitational Field
We describe an upper level undergraduate experiment on the time-dependent behavior of a suspension of Brownian particles under gravitational attraction. We employed the Fokker-Planck equation in the strong friction limit and measured the time-evolution of the probability distribution for 1.0 mu m diameter latex Brownian particles in water at room temperature and pressure. The experiment provides evidence of the atomic nature of water.Physic
Symmetry in Critical Random Boolean Network Dynamics
Using Boolean networks as prototypical examples, the role of symmetry in the
dynamics of heterogeneous complex systems is explored. We show that symmetry of
the dynamics, especially in critical states, is a controlling feature that can
be used both to greatly simplify analysis and to characterize different types
of dynamics. Symmetry in Boolean networks is found by determining the frequency
at which the various Boolean output functions occur. There are classes of
functions that consist of Boolean functions that behave similarly. These
classes are orbits of the controlling symmetry group. We find that the symmetry
that controls the critical random Boolean networks is expressed through the
frequency by which output functions are utilized by nodes that remain active on
dynamical attractors. This symmetry preserves canalization, a form of network
robustness. We compare it to a different symmetry known to control the dynamics
of an evolutionary process that allows Boolean networks to organize into a
critical state. Our results demonstrate the usefulness and power of using the
symmetry of the behavior of the nodes to characterize complex network dynamics,
and introduce a novel approach to the analysis of heterogeneous complex
systems
Quantum and Classical Chaos in Kicked Coupled Jaynes-Cummings Cavities
We consider two Jaynes-Cummings cavities coupled periodically with a photon
hopping term. The semi-classical phase space is chaotic, with regions of
stability over some ranges of the parameters. The quantum case exhibits dynamic
localization and dynamic tunneling between classically forbidden regions. We
explore the correspondence between the classical and quantum phase space and
propose a scheme for implementing the system experimentally
Phase transition from nuclear matter to color superconducting quark matter: the effect of the isospin
We compute the mixed phase of nuclear matter and 2SC matter for different
temperatures and proton fractions. After showing that the symmetry energy of
the 2SC phase is, to a good approximation, three times larger than the one of
the normal quark phase, we discuss and compare all the properties of the mixed
phase with a 2SC component or a normal quark matter component. In particular,
the local isospin densities of the nuclear and the quark component and the
stiffness of the mixed phase are significantly different whether the 2SC phase
or the normal quark phase are considered. If a strong diquark pairing is
adopted for the 2SC phase, there is a possibility to eventually enter in the
nuclear matter 2SC matter mixed phase in low energy heavy ions collisions
experiments. Possible observables able to discern between the formation of the
2SC phase or the normal quark phase are finally discussed.Comment: 9 pages, 8 figure
Chaos assisted adiabatic passage
We study the exact dynamics underlying stimulated Raman adiabatic passage
(STIRAP) for a particle in a multi-level anharmonic system (the infinite
square-well) driven by two sequential laser pulses, each with constant carrier
frequency. In phase space regions where the laser pulses create chaos, the
particle can be transferred coherently into energy states different from those
predicted by traditional STIRAP. It appears that a transition to chaos can
provide a new tool to control the outcome of STIRAP
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