623 research outputs found
Forbidden activation levels in a non-stationary tunneling process
Tunneling in the presence of an opaque barrier, part of which varies in time,
is investigated numerically and analytically in one dimension. Clearly, due to
the varying barrier a tunneling particle experiences spectral widening.
However, in the case of strong perturbations, the particles' activation to
certain energies is avoided. We show that this effect occurs only when the
perturbation decays faster than 1/t^2.Comment: 4pages,2 figures (Revtex
Universal Mortality Law, Life Expectancy and Immortality
Well protected human and laboratory animal populations with abundant
resources are evolutionary unprecedented, and their survival far beyond
reproductive age may be a byproduct rather than tool of evolution. Physical
approach, which takes advantage of their extensively quantified mortality,
establishes that its dominant fraction yields the exact law, and suggests its
unusual mechanism. The law is universal for all animals, from yeast to humans,
despite their drastically different biology and evolution. It predicts that the
universal mortality has short memory of the life history, at any age may be
reset to its value at a significantly younger age, and mean life expectancy
extended (by biologically unprecedented small changes) from its current maximal
value to immortality. Mortality change is rapid and stepwise. Demographic data
and recent experiments verify these predictions for humans, rats, flies,
nematodes and yeast. In particular, mean life expectancy increased 6-fold (to
"human" 430 years), with no apparent loss in health and vitality, in nematodes
with a small number of perturbed genes and tissues. Universality allows one to
study unusual mortality mechanism and the ways to immortality
The quantum group, Harper equation and the structure of Bloch eigenstates on a honeycomb lattice
The tight-binding model of quantum particles on a honeycomb lattice is
investigated in the presence of homogeneous magnetic field. Provided the
magnetic flux per unit hexagon is rational of the elementary flux, the
one-particle Hamiltonian is expressed in terms of the generators of the quantum
group . Employing the functional representation of the quantum group
the Harper equation is rewritten as a systems of two coupled
functional equations in the complex plane. For the special values of
quasi-momentum the entangled system admits solutions in terms of polynomials.
The system is shown to exhibit certain symmetry allowing to resolve the
entanglement, and basic single equation determining the eigenvalues and
eigenstates (polynomials) is obtained. Equations specifying locations of the
roots of polynomials in the complex plane are found. Employing numerical
analysis the roots of polynomials corresponding to different eigenstates are
solved out and the diagrams exhibiting the ordered structure of one-particle
eigenstates are depicted.Comment: 11 pages, 4 figure
Synthetic Gauge Fields for Vibrational Excitations of Trapped ions
The vibrations of a collection of ions in a microtrap array can be described
in terms of hopping phonons. We show theoretically that the vibrational
couplings may be tailored by using a gradient of the microtrap frequencies,
together with a periodic driving of the trapping potential. These ingredients
allow us to induce effective gauge fields on the vibrational excitations, such
that phonons mimic the behavior of charged particles in a magnetic field. In
particular, microtrap arrays are ideally suited to realize the famous
Aharonov-Bohm effect, and observe the paradigmatic edge states typical from
quantum-Hall samples and topological insulators.Comment: replaced with published versio
- …