475 research outputs found
The three-body problem and the Hannay angle
The Hannay angle has been previously studied for a celestial circular
restricted three-body system by means of an adiabatic approach. In the present
work, three main results are obtained. Firstly, a formal connection between
perturbation theory and the Hamiltonian adiabatic approach shows that both lead
to the Hannay angle; it is thus emphasised that this effect is already
contained in classical celestial mechanics, although not yet defined nor
evaluated separately. Secondly, a more general expression of the Hannay angle,
valid for an action-dependent potential is given; such a generalised expression
takes into account that the restricted three-body problem is a time-dependent,
two degrees of freedom problem even when restricted to the circular motion of
the test body. Consequently, (some of) the eccentricity terms cannot be
neglected {\it a priori}. Thirdly, we present a new numerical estimate for the
Earth adiabatically driven by Jupiter. We also point out errors in a previous
derivation of the Hannay angle for the circular restricted three-body problem,
with an action-independent potential.Comment: 11 pages. Accepted by Nonlinearit
^{59}Co NMR evidence for charge ordering below T_{CO}\sim 51 K in Na_{0.5}CoO_2
The CoO layers in sodium-cobaltates NaCoO may be viewed as
a spin triangular-lattice doped with charge carriers. The underlying
physics of the cobaltates is very similar to that of the high cuprates.
We will present unequivocal Co NMR evidence that below ,
the insulating ground state of the itinerant antiferromagnet
NaCoO () is induced by charge ordering.Comment: Phys. Rev. Lett. 100 (2008), in press. 4 figure
The co-chaperone p23 controls root development through the modulation of auxin distribution in the Arabidopsis root meristem.
Homologues of the p23 co-chaperone of HSP90 are present in all eukaryotes, suggesting conserved functions for this protein throughout evolution. Although p23 has been extensively studied in animal systems, little is known about its function in plants. In the present study, the functional characterization of the two isoforms of p23 in Arabidopsis thaliana is reported, suggesting a key role of p23 in the regulation of root development. Arabidopsis p23 mutants, for either form, show a short root length phenotype with a reduced meristem length. In the root meristem a low auxin level associated with a smaller auxin gradient was observed. A decrease in the expression levels of PIN FORMED PROTEIN (PIN)1, PIN3, and PIN7, contextually to an inefficient polar localization of PIN1, was detected. Collectively these results suggest that both Arabidopsis p23 isoforms are required for root growth, in particular in the maintenance of the root meristem, where the proteins are located
The Isovector Quadrupole-Quadrupole Interaction Used in Shell Model Calculations
An interaction is used
in a shell model calculation for . Whereas for the state
is two-fold degenerate, introducing a negative causes an `isovector'
state to come down to zero energy at and an triplet
() to come down to zero energy at . These are
undesirable properties, but a large negative is apparently needed to fit
the energy of the isovector giant quadrupole resonance.Comment: 12 pages, revtex, 2 figures (available on request
The co-chaperone p23 controls root development through the modulation of auxin distribution in the Arabidopsis root meristem
p23 co-chaperones play a key role in the root meristem maintenance via regulation of auxin signalling and the consequent balance between cell differentiation and division rate at the transition zon
Huffman Coding with Letter Costs: A Linear-Time Approximation Scheme
We give a polynomial-time approximation scheme for the generalization of
Huffman Coding in which codeword letters have non-uniform costs (as in Morse
code, where the dash is twice as long as the dot). The algorithm computes a
(1+epsilon)-approximate solution in time O(n + f(epsilon) log^3 n), where n is
the input size
Geometric phases and anholonomy for a class of chaotic classical systems
Berry's phase may be viewed as arising from the parallel transport of a
quantal state around a loop in parameter space. In this Letter, the classical
limit of this transport is obtained for a particular class of chaotic systems.
It is shown that this ``classical parallel transport'' is anholonomic ---
transport around a closed curve in parameter space does not bring a point in
phase space back to itself --- and is intimately related to the Robbins-Berry
classical two-form.Comment: Revtex, 11 pages, no figures
Constructing a Large Variety of Dirac-Cone Materials in the BiSb Thin Film System
We theoretically predict that a large variety of Dirac-cone materials can be
constructed in BiSb thin films, and we here show how to
construct single-, bi- and tri- Dirac-cone materials with various amounts of
wave vector anisotropy. These different types of Dirac cones can be of special
interest to electronic devices design, quantum electrodynamics and other
fields
An Adiabatic Theorem without a Gap Condition
The basic adiabatic theorems of classical and quantum mechanics are
over-viewed and an adiabatic theorem in quantum mechanics without a gap
condition is described.Comment: Talk at QMath 7, Prague, 1998. 10 pages, 7 figure
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