2,658 research outputs found
Weak Charge Quantization as an Instanton of Interacting sigma-model
Coulomb blockade in a quantum dot attached to a diffusive conductor is
considered in the framework of the non-linear sigma-model. It is shown that the
weak charge quantization on the dot is associated with instanton configurations
of the Q-field in the conductor. The instantons have a finite action and are
replica non--symmetric. It is argued that such instantons may play a role in
the transition regime to the interacting insulator.Comment: 4 pages. The 2D case substantially modifie
Symmetry of Quantum Phase Space in a Degenerate Hamiltonian System
Using Husimi function approach, we study the ``quantum phase space'' of a
harmonic oscillator interacting with a plane monochromatic wave. We show that
in the regime of weak chaos, the quantum system has the same symmetry as the
classical system. Analytical results agree with the results of numerical
calculations.Comment: 11 pages LaTex, including 2 Postscript figure
Stationary cantilever vibrations in the oscillating cantilever-driven adiabatic reversals -- magnetic resonance force microscopy technique
We consider theoretically the novel technique in magnetic resonance force
microscopy which is called ``oscillating cantilever-driven adiabatic
reversals''. We present analytical and numerical analysis for the stationary
cantilever vibrations in this technique. For reasonable values of parameters we
estimate the resonant frequency shift as 6Hz per the Bohr magneton. We analyze
also the regime of small oscillations of the paramagnetic moment near the
transversal plane and the frequency shift of the damped cantilever vibrations.Comment: 12 pages RevTex
Wigner-Dyson Statistics from the Keldysh Sigma-Model
The level statistics of disordered metallic grains with broken time reversal
invariance is obtained from a saddle point analysis of the Keldysh nonlinear
sigma-model
Dynamics of excitations in a one-dimensional Bose liquid
We show that the dynamic structure factor of a one-dimensional Bose liquid
has a power-law singularity defining the main mode of collective excitations.
Using the Lieb-Liniger model, we evaluate the corresponding exponent as a
function of the wave vector and the interaction strength
Replica treatment of non-Hermitian disordered Hamiltonians
We employ the fermionic and bosonic replicated nonlinear sigma models to
treat Ginibre unitary, symplectic, and orthogonal ensembles of non-Hermitian
random matrix Hamiltonians. Using saddle point approach combined with Borel
resummation procedure we derive the exact large-N results for microscopic
density of states in all three ensembles. We also obtain tails of the density
of states as well the two-point function for the unitary ensemble.Comment: REVTeX 3.1, 13 pages, 1 figure; typos fixed (v2
Towards Classification of Phase Transitions in Reaction--Diffusion Models
Equilibrium phase transitions are associated with rearrangements of minima of
a (Lagrangian) potential. Treatment of non-equilibrium systems requires
doubling of degrees of freedom, which may be often interpreted as a transition
from the ``coordinate'' to the ``phase'' space representation. As a result, one
has to deal with the Hamiltonian formulation of the field theory instead of the
Lagrangian one. We suggest a classification scheme of phase transitions in
reaction-diffusion models based on the topology of the phase portraits of
corresponding Hamiltonians. In models with an absorbing state such a topology
is fully determined by intersecting curves of zero ``energy''. We identify four
families of topologically distinct classes of phase portraits stable upon RG
transformations.Comment: 14 pages, 9 figure
Quantum interference and Coulomb interaction in arrays of tunnel junctions
We study the electronic properties of an array of small metallic grains
connected by tunnel junctions. Such an array serves as a model for a granular
metal. Previous theoretical studies of junction arrays were based on models of
quantum dissipation which did not take into account the diffusive motion of
electrons within the grains. We demonstrate that these models break down at
sufficiently low temperatures: for a correct description of the screening
properties of a granular metal at low energies the diffusive nature of the
electronic motion within the grains is crucial. We present both a diagrammatic
and a functional integral approach to analyse the properties of junction
arrays. In particular, a new effective action is obtained which enables us to
describe the array at arbitrary temperature. In the low temperature limit, our
theory yields the correct, dynamically screened Coulomb interaction of a normal
metal, whereas at high temperatures the standard description in terms of
quantum dissipation is recovered.Comment: 14 pages, 7 figure
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