7,472 research outputs found
The quantum dynamics of atomic magnets, co-tunneling and dipolar-biased tunneling
Multi-spins tunneling cross-relaxations in an ensemble of weakly-coupled
Ho ions, mediated by weak anisotropic dipolar interactions, can be
evidenced by ac-susceptibility measurements in a high temperature regime. Based
on a four-body representation, including the rare-earth nuclear spin, two-ions
tunneling mechanisms can be attributed to both dipolar-biased tunneling and
co-tunneling processes. The co-reversal involving entangled pairs of magnetic
moments is discussed with a particular emphasis, giving new evidences to
elucidate the many-body quantum dynamics.Comment: 4 figure
Comment on "Motion of an impurity particle in an ultracold quasi-one-dimensional gas of hard-core bosons [Phys. Rev. A 79, 033610 (2009)]"
Very recently Girardeau and Minguzzi [arXiv:0807.3366v2, Phys. Rev. A 79,
033610 (2009)] have studied an impurity in a one-dimensional gas of hard-core
bosons. In particular they deal with the general case where the mass of the
impurity is different from the mass of the bosons and the impurity-boson
interaction is not necessarily infinitely repulsive. We show that one of their
initial step is erroneous, contradicting both physical intuition and known
exact results. Their results in the general case apply only actually when the
mass of the impurity is infinite.Comment: Submitted to Phys. Rev. A on 30 April 200
On positive functions with positive Fourier transforms
Using the basis of Hermite-Fourier functions (i.e. the quantum oscillator
eigenstates) and the Sturm theorem, we derive the practical constraints for a
function and its Fourier transform to be both positive. We propose a
constructive method based on the algebra of Hermite polynomials. Applications
are extended to the 2-dimensional case (i.e. Fourier-Bessel transforms and the
algebra of Laguerre polynomials) and to adding constraints on derivatives, such
as monotonicity or convexity.Comment: 12 pages, 23 figures. High definition figures can be obtained upon
request at [email protected] or [email protected]
Analytical theory of the dressed bound state in highly polarized Fermi gases
We present an analytical treatment of a single \down atom within a Fermi sea
of \up atoms, when the interaction is strong enough to produce a bound state,
dressed by the Fermi sea. Our method makes use of a diagrammatic analysis, with
the involved diagrams taking only into account at most two particle-hole pairs
excitations. The agreement with existing Monte-Carlo results is excellent. In
the BEC limit our equation reduces exactly to the Skorniakov and
Ter-Martirosian equation. We present results when \up and \down atoms have
different masses, which is of interest for experiments in progress.Comment: 5 pages, 3 figure
On the nonlinear response of a particle interacting with fermions in a 1D lattice
By the Bethe ansatz method we study the energy dispersion of a particle
interacting by a local interaction with fermions (or hard core bosons) of equal
mass in a one dimensional lattice. We focus on the period of the Bloch
oscillations which turns out to be related to the Fermi wavevector of the Fermi
sea and in particular on how this dispersion emerges as a collective effect in
the thermodynamic limit. We show by symmetry that the dispersion is temperature
independent for a half-filled system. We also discuss the adiabatic coherent
collective response of the particle to an applied field.Comment: 4 pages, 4 figure
Existence of a Density Functional for an Intrinsic State
A generalization of the Hohenberg-Kohn theorem proves the existence of a
density functional for an intrinsic state, symmetry violating, out of which a
physical state with good quantum numbers can be projected.Comment: 6 page
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