52 research outputs found
Time-dependent correlation function of the Jordan-Wigner operator as a Fredholm determinant
We calculate a correlation function of the Jordan-Wigner operator in a class
of free-fermion models formulated on an infinite one-dimensional lattice. We
represent this function in terms of the determinant of an integrable Fredholm
operator, convenient for analytic and numerical investigations. By using Wick's
theorem, we avoid the form-factor summation customarily used in literature for
treating similar problems.Comment: references added, introduction and conclusion modified, version
accepted for publication in J. Stat. Mec
Quantum flutter of supersonic particles in one-dimensional quantum liquids
The non-equilibrium dynamics of strongly correlated many-body systems
exhibits some of the most puzzling phenomena and challenging problems in
condensed matter physics. Here we report on essentially exact results on the
time evolution of an impurity injected at a finite velocity into a
one-dimensional quantum liquid. We provide the first quantitative study of the
formation of the correlation hole around a particle in a strongly coupled
many-body quantum system, and find that the resulting correlated state does not
come to a complete stop but reaches a steady state which propagates at a finite
velocity. We also uncover a novel physical phenomenon when the impurity is
injected at supersonic velocities: the correlation hole undergoes long-lived
coherent oscillations around the impurity, an effect we call quantum flutter.
We provide a detailed understanding and an intuitive physical picture of these
intriguing discoveries, and propose an experimental setup where this physics
can be realized and probed directly.Comment: 13 pages, 9 figure
Low-temperature crossover in the momentum distribution of cold atomic gases in one dimension
The momentum distribution function for the two-component 1D gases of bosons
and fermions is studied in the limit of strong interatomic repulsion. A
pronounced reconstruction of the distribution is found at a temperature much
smaller than the Fermi temperature. This new temperature scale, which equals
the Fermi temperature divided by the dimensionless coupling strength, is a
feature of the two-component model and does not exist in the one-component
case. We estimate the parameters relevant for the experimental observation of
the crossover effect.Comment: 6 pages, 2 figure
Excitations in two-component Bose-gases
In this paper, we study a strongly correlated quantum system that has become
amenable to experiment by the advent of ultracold bosonic atoms in optical
lattices, a chain of two different bosonic constituents. Excitations in this
system are first considered within the framework of bosonization and Luttinger
liquid theory which are applicable if the Luttinger liquid parameters are
determined numerically. The occurrence of a bosonic counterpart of fermionic
spin-charge separation is signalled by a characteristic two-peak structure in
the spectral functions found by dynamical DMRG in good agreement with
analytical predictions. Experimentally, single-particle excitations as probed
by spectral functions are currently not accessible in cold atoms. We therefore
consider the modifications needed for current experiments, namely the
investigation of the real-time evolution of density perturbations instead of
single particle excitations, a slight inequivalence between the two
intraspecies interactions in actual experiments, and the presence of a
confining trap potential. Using time-dependent DMRG we show that only
quantitative modifications occur. With an eye to the simulation of strongly
correlated quantum systems far from equilibrium we detect a strong dependence
of the time-evolution of entanglement entropy on the initial perturbation,
signalling limitations to current reasonings on entanglement growth in
many-body systems
MODELING THERMAL TREE STRUCTURES ON A WATER SURFACE IN COMSOL MULTIPHYSICS
The movement of the heated fluid is modeled using Comsol Multiphusics software. Tree-like temperature structures are obtained on the surface of the water. This result is consistent with previous observations and modeling
Exploring the growth of correlations in a quasi one-dimensional trapped Bose gas
Phase correlations, density fluctuations and three-body loss rates are
relevant for many experiments in quasi one-dimensional geometries. Extended
mean-field theory is used to evaluate correlation functions up to third order
for a quasi one-dimensional trapped Bose gas at zero and finite temperature. At
zero temperature and in the homogeneous limit, we also study the transition
from the weakly correlated Gross-Pitaevskii regime to the strongly correlated
Tonks-Girardeau regime analytically. We compare our results with the exact
Lieb-Liniger solution for the homogeneous case and find good agreement up to
the cross-over regime.Comment: 36 pages, 21 color pdf/jpeg figures, submitted to NJP, corrected
reference
Terbium photo-, cathodo- and X-ray luminescence in sol-gel derived films in porous anodic alumina
Photo-, cathodo-, and X-ray luminescence of terbium in sol-gel derived films, fabricated in porous anodic alumina is studied. The cell size of the fabricated film convertor of irradiation is about 250 nm. The methods of increase Tb luminescence under diverse excitation conditions are discussed. © 2012 CriMiCo
The Russian-American gallium experiment (SAGE) Cr neutrino source measurement
No description supplie
Measurement of the response of a gallium metal solar neutrino experiment to neutrinos from a [Formula Presented] source
The neutrino capture rate measured by the Russian-American Gallium Experiment is well below that predicted by solar models. To check the response of this experiment to low-energy neutrinos, a 517 kCi source of [Formula Presented]Cr was produced by irradiating 512.7 g of 92.4%-enriched [Formula Presented]Cr in a high-flux fast neutron reactor. This source, which mainly emits monoenergetic 747-keV neutrinos, was placed at the center of a 13.1 ton target of liquid gallium and the cross section for the production of [Formula Presented]Ge by the inverse beta decay [Formula Presented] was measured to be [Formula Presented] The ratio of this cross section to the theoretical cross section of Bahcall for this reaction is 0.95 ±0.12 [Formula Presented] (theor) and to the cross section of Haxton is 0.87±0.11 (expt)±0.09 (theor). This good agreement between prediction and observation implies that the overall experimental efficiency is correctly determined and provides considerable evidence for the reliability of the solar neutrino measurement. © 1999 The American Physical Society
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