191,088 research outputs found
A Bi-Hamiltonian Formulation for Triangular Systems by Perturbations
A bi-Hamiltonian formulation is proposed for triangular systems resulted by
perturbations around solutions, from which infinitely many symmetries and
conserved functionals of triangular systems can be explicitly constructed,
provided that one operator of the Hamiltonian pair is invertible. Through our
formulation, four examples of triangular systems are exhibited, which also show
that bi-Hamiltonian systems in both lower dimensions and higher dimensions are
many and varied. Two of four examples give local 2+1 dimensional bi-Hamiltonian
systems and illustrate that multi-scale perturbations can lead to
higher-dimensional bi-Hamiltonian systems.Comment: 16 pages, to appear in J. Math. Phy
Dissipate locally, couple globally: a sharp transition from decoupling to infinite range coupling in Josephson arrays with on-site dissipation
We study the T=0 normal to superconducting transition of Josephson arrays
with {\it on-site} dissipation. A perturbative renormalization group solution
is given. Like the previously studied case of {\it bond} dissipation (BD), this
is a "floating" to coupled (FC) phase transition. {\it Unlike} the BD
transition, at which {\it only} nearest-neighbor couplings become relevant,
here {\it all} inter-grain couplings, out to {\it infinitely} large distances,
do so simultaneously. We predict, for the first time in an FC transition, a
diverging spatial correlation length. Our results show the robustness of
floating phases in dissipative quantum systems.Comment: 7+ pages, 3 eps figures, Europhysics Letters preprint format, as
publishe
Flow effects on multifragmentation in the canonical model
A prescription to incorporate the effects of nuclear flow on the process of
multifragmentation of hot nuclei is proposed in an analytically solvable
canonical model. Flow is simulated by the action of an effective negative
external pressure. It favors sharpening the signatures of liquid-gas phase
transition in finite nuclei with increased multiplicity and a lowered phase
transition temperature.Comment: 13 pages, 5 Post Script figures (accepted for publication in PRC
Renormalization group for the probability distribution of magnetic impurities in a random-field model
Extending the usual Ginzburg-Landau theory for the random-field Ising model,
the possibility of dimensional reduction is reconsidered. A renormalization
group for the probability distribution of magnetic impurities is applied. New
parameters corresponding to the extra coupling constants in the
replica Hamiltonian are introduced. Although they do not affect the critical
phenomena near the upper critical dimension, they can when dimensions are
lowered.Comment: 16 pages, 11 figures, revte
Collapse and revival oscillations as a probe for the tunneling amplitude in an ultra-cold Bose gas
We present a theoretical study of the quantum corrections to the revival time
due to finite tunneling in the collapse and revival of matter wave interference
after a quantum quench. We study hard-core bosons in a superlattice potential
and the Bose-Hubbard model by means of exact numerical approaches and
mean-field theory. We consider systems without and with a trapping potential
present. We show that the quantum corrections to the revival time can be used
to accurately determine the value of the hopping parameter in experiments with
ultracold bosons in optical lattices.Comment: 10 pages, 12 figures, typos in section 3A correcte
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