85 research outputs found
Copolymer adsorption kinetics at a selective liquid-liquid interface: Scaling theory and computer experiment
We consider the adsorption kinetics of a regular block-copolymer of total
length and block size at a selective liquid-liquid interface in the
limit of strong localization. We propose a simple analytic theory based on
scaling considerations which describes the relaxation of the initial coil into
a flat-shaped layer. The characteristic times for attaining equilibrium values
of the gyration radius components perpendicular and parallel to the interface
are predicted to scale with chain length and block length as
(here is the Flory exponent)
and as , although initially the rate of coil
flattening is expected to decrease with block size as . Since
typically for multiblock copolymers, our results suggest that the
flattening dynamics proceeds faster perpendicular rather than parallel to the
interface. We also demonstrate that these scaling predictions agree well with
the results of extensive Monte Carlo simulations of the localization dynamics.Comment: 4 pages, 4 figures, submited to Europhys. Let
Semiclassical theory for many-body Fermionic systems
We present a treatment of many-body Fermionic systems that facilitates an
expression of the well-known quantities in a series expansion of the Planck's
constant. The ensuing semiclassical result contains to a leading order of the
response function the classical time correlation function of the observable
followed by the Weyl-Wigner series, on top of these terms are the
periodic-orbit correction terms. The treatment given here starts from linear
response assumption of the many-body theory and in its connection with
semiclassical theory, it makes no assumption of the integrability of classical
dynamics underlying the one-body quantal system. Applications of the framework
are also discussed.Comment: 18 pages, Te
Anatomy of quantum chaotic eigenstates
The eigenfunctions of quantized chaotic systems cannot be described by
explicit formulas, even approximate ones. This survey summarizes (selected)
analytical approaches used to describe these eigenstates, in the semiclassical
limit. The levels of description are macroscopic (one wants to understand the
quantum averages of smooth observables), and microscopic (one wants
informations on maxima of eigenfunctions, "scars" of periodic orbits, structure
of the nodal sets and domains, local correlations), and often focusses on
statistical results. Various models of "random wavefunctions" have been
introduced to understand these statistical properties, with usually good
agreement with the numerical data. We also discuss some specific systems (like
arithmetic ones) which depart from these random models.Comment: Corrected typos, added a few references and updated some result
Quantum computers in phase space
We represent both the states and the evolution of a quantum computer in phase
space using the discrete Wigner function. We study properties of the phase
space representation of quantum algorithms: apart from analyzing important
examples, such as the Fourier Transform and Grover's search, we examine the
conditions for the existence of a direct correspondence between quantum and
classical evolutions in phase space. Finally, we describe how to directly
measure the Wigner function in a given phase space point by means of a
tomographic method that, itself, can be interpreted as a simple quantum
algorithm.Comment: 16 pages, 7 figures, to appear in Phys Rev
Features of Time-independent Wigner Functions
The Wigner phase-space distribution function provides the basis for Moyal's
deformation quantization alternative to the more conventional Hilbert space and
path integral quantizations. General features of time-independent Wigner
functions are explored here, including the functional ("star") eigenvalue
equations they satisfy; their projective orthogonality spectral properties;
their Darboux ("supersymmetric") isospectral potential recursions; and their
canonical transformations. These features are illustrated explicitly through
simple solvable potentials: the harmonic oscillator, the linear potential, the
Poeschl-Teller potential, and the Liouville potential.Comment: 18 pages, plain LaTex, References supplemente
Quark Imaging in the Proton Via Quantum Phase-Space Distributions
We develop the concept of quantum phase-space (Wigner) distributions for
quarks and gluons in the proton. To appreciate their physical content, we
analyze the contraints from special relativity on the interpretation of elastic
form factors, and examine the physics of the Feynman parton distributions in
the proton's rest frame. We relate the quark Wigner functions to the
transverse-momentum dependent parton distributions and generalized parton
distributions, emphasizing the physical role of the skewness parameter. We show
that the Wigner functions allow to visualize quantum quarks and gluons using
the language of the classical phase space. We present two examples of the quark
Wigner distributions and point out some model-independent features.Comment: 20 pages with 3 fiture
GRIPS - Gamma-Ray Imaging, Polarimetry and Spectroscopy
We propose to perform a continuously scanning all-sky survey from 200 keV to
80 MeV achieving a sensitivity which is better by a factor of 40 or more
compared to the previous missions in this energy range. The Gamma-Ray Imaging,
Polarimetry and Spectroscopy (GRIPS) mission addresses fundamental questions in
ESA's Cosmic Vision plan. Among the major themes of the strategic plan, GRIPS
has its focus on the evolving, violent Universe, exploring a unique energy
window. We propose to investigate -ray bursts and blazars, the
mechanisms behind supernova explosions, nucleosynthesis and spallation, the
enigmatic origin of positrons in our Galaxy, and the nature of radiation
processes and particle acceleration in extreme cosmic sources including pulsars
and magnetars. The natural energy scale for these non-thermal processes is of
the order of MeV. Although they can be partially and indirectly studied using
other methods, only the proposed GRIPS measurements will provide direct access
to their primary photons. GRIPS will be a driver for the study of transient
sources in the era of neutrino and gravitational wave observatories such as
IceCUBE and LISA, establishing a new type of diagnostics in relativistic and
nuclear astrophysics. This will support extrapolations to investigate star
formation, galaxy evolution, and black hole formation at high redshifts.Comment: to appear in Exp. Astron., special vol. on M3-Call of ESA's Cosmic
Vision 2010; 25 p., 25 figs; see also www.grips-mission.e
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