4,736 research outputs found
Fermionization of two-component few-fermion systems in a one-dimensional harmonic trap
The nature of strongly interacting Fermi gases and magnetism is one of the
most important and studied topics in condensed-matter physics. Still, there are
many open questions. A central issue is under what circumstances strong
short-range repulsive interactions are enough to drive magnetic correlations.
Recent progress in the field of cold atomic gases allows to address this
question in very clean systems where both particle numbers, interactions and
dimensionality can be tuned. Here we study fermionic few-body systems in a one
dimensional harmonic trap using a new rapidly converging effective-interaction
technique, plus a novel analytical approach. This allows us to calculate the
properties of a single spin-down atom interacting with a number of spin-up
particles, a case of much recent experimental interest. Our findings indicate
that, in the strongly interacting limit, spin-up and spin-down particles want
to separate in the trap, which we interpret as a microscopic precursor of
one-dimensional ferromagnetism in imbalanced systems. Our predictions are
directly addressable in current experiments on ultracold atomic few-body
systems.Comment: 12 pages, 6 figures, published version including two appendices on
our new numerical and analytical approac
An interpolatory ansatz captures the physics of one-dimensional confined Fermi systems
Interacting one-dimensional quantum systems play a pivotal role in physics.
Exact solutions can be obtained for the homogeneous case using the Bethe ansatz
and bosonisation techniques. However, these approaches are not applicable when
external confinement is present. Recent theoretical advances beyond the Bethe
ansatz and bosonisation allow us to predict the behaviour of one-dimensional
confined systems with strong short-range interactions, and new experiments with
cold atomic Fermi gases have already confirmed these theories. Here we
demonstrate that a simple linear combination of the strongly interacting
solution with the well-known solution in the limit of vanishing interactions
provides a simple and accurate description of the system for all values of the
interaction strength. This indicates that one can indeed capture the physics of
confined one-dimensional systems by knowledge of the limits using wave
functions that are much easier to handle than the output of typical numerical
approaches. We demonstrate our scheme for experimentally relevant systems with
up to six particles. Moreover, we show that our method works also in the case
of mixed systems of particles with different masses. This is an important
feature because these systems are known to be non-integrable and thus not
solvable by the Bethe ansatz technique.Comment: 22 pages including methods and supplementary materials, 11 figures,
title slightly change
Post-Wick theorems for symbolic manipulation of second-quantized expressions in atomic many-body perturbation theory
Manipulating expressions in many-body perturbation theory becomes unwieldily
with increasing order of the perturbation theory. Here I derive a set of
theorems for efficient simplification of such expressions. The derived rules
are specifically designed for implementing with symbolic algebra tools. As an
illustration, we count the numbers of Brueckner-Goldstone diagrams in the first
several orders of many-body perturbation theory for matrix elements between two
states of a mono-valent system.Comment: J. Phys. B. (in press); Mathematica packages available from
http://wolfweb.unr.edu/homepage/andrei/WWW-tap/mathematica.htm
Getting ready for the marriage market? The association between divorce risks and investments in attractive body mass among married Europeans
This article explores to what extent married middle-aged individuals in Europe are governed by the risk of experiencing divorce, when shaping their physical appearance. The main result is that divorce risks, proxied by national divorce rates, are negatively connected to body mass index (BMI) among married individuals but unrelated to BMI among singles. Hence, it seems that married people in societies where divorce risks are high are more inclined to invest in their outer appearance. One interpretation is that high divorce rates make married people prepare for a potential divorce and future return to the marriage market
Chiral surfaces self-assembling in one-component systems with isotropic interactions
We show that chiral symmetry can be broken spontaneously in one-component
systems with isotropic interactions, i.e. many-particle systems having maximal
a priori symmetry. This is achieved by designing isotropic potentials that lead
to self-assembly of chiral surfaces. We demonstrate the principle on a simple
chiral lattice and on a more complex lattice with chiral super-cells. In
addition we show that the complex lattice has interesting melting behavior with
multiple morphologically distinct phases that we argue can be qualitatively
predicted from the design of the interaction.Comment: 4 pages, 4 figure
Complexity Measures from Interaction Structures
We evaluate new complexity measures on the symbolic dynamics of coupled tent
maps and cellular automata. These measures quantify complexity in terms of
-th order statistical dependencies that cannot be reduced to interactions
between units. We demonstrate that these measures are able to identify
complex dynamical regimes.Comment: 11 pages, figures improved, minor changes to the tex
A COMPARISON OF THE MMPI-2 AND RORSCHACH INKBLOT TECHNIQUE IN ASSESSING SCHIZOPHRENIA
The study examined the concordance of Rorschach and
MMPI-2 variables relating to schizophrenia. 85 psychiatric
inpatients were administered both the MMPI-2 and Rorschach.
A profile analysis compared individuals who elevated on the
Rorschach SCZI index to nonelevators. No significant
profile differences were found using a SCZI index cutoff of
4. When more distinct SCZI index groups were created ( ≥ 5
vs. ≤ 2) the profiles were found to be significantly
different (average MMPI-2 profile for elevated SCZI group =
8-6-7) and the elevated SCZI group evidenced higher MMPI
scale scores overall. The 8-6-7 profile has been
associated with schizophrenia in previous research. The
sensitivity, specificity, and hit rate of both instruments
in predicting clinical diagnoses were also calculated. The
MMPI-2 demonstrated better sensitivity while the SCZI index
yielded higher specificity; the combination of instruments
produced the best hit rate. The study demonstrated a
relationship between MMPI-2 and Rorschach variables related
to psychosis
- …