10,271 research outputs found
Interacting Fermi Gases in Disordered One-Dimensional Lattices
Interacting two-component Fermi gases loaded in a one-dimensional (1D)
lattice and subject to harmonic trapping exhibit intriguing compound phases in
which fluid regions coexist with local Mott-insulator and/or band-insulator
regions. Motivated by experiments on cold atoms inside disordered optical
lattices, we present a theoretical study of the effects of a random potential
on these ground-state phases. Within a density-functional scheme we show that
disorder has two main effects: (i) it destroys the local insulating regions if
it is sufficiently strong compared with the on-site atom-atom repulsion, and
(ii) it induces an anomaly in the compressibility at low density from quenching
of percolation.Comment: 7 pages, 4 figures, submitte
Moral Grandstanding in Public Discourse: Status-Seeking Motives as a Potential Explanatory Mechanism in Predicting Conflict
Public discourse is often caustic and conflict-filled. This trend seems to be particularly evident when the content of such discourse is around moral issues (broadly defined) and when the discourse occurs on social media. Several explanatory mechanisms for such conflict have been explored in recent psychological and social-science literatures. The present work sought to examine a potentially novel explanatory mechanism defined in philosophical literature: Moral Grandstanding. According to philosophical accounts, Moral Grandstanding is the use of moral talk to seek social status. For the present work, we conducted six studies, using two undergraduate samples (Study 1, N = 361; Study 2, N = 356); a sample matched to U.S. norms for age, gender, race, income, Census region (Study 3, N = 1,063); a YouGov sample matched to U.S. demographic norms (Study 4, N = 2,000); and a brief, one-month longitudinal study of Mechanical Turk workers in the U.S. (Study 5, Baseline N = 499, follow-up n = 296), and a large, one-week YouGov sample matched to U.S. demographic norms (Baseline N = 2,519, follow-up n = 1,776). Across studies, we found initial support for the validity of Moral Grandstanding as a construct. Specifically, moral grandstanding motivation was associated with status-seeking personality traits, as well as greater political and moral conflict in daily life
The Chemical Evolution of the Milky Way
The field of chemical evolution modeling of the Galaxy is experiencing in the
last years a phase of high activity and important achievements. There are,
however, several open questions which still need to be answered. In this review
I summarize what have been the most important achievements and what are some of
the most urgent questions to be answered.Comment: 10 pages including 3 figs, to appear in "The Chemical Evolution of
the Milky Way. Stars vs Clusters", Proceedings of the Sept.1999 Vulcano
Workshop, F.Giovannelli and F.Matteucci eds (Kluwer, Dordrecht) in pres
Many-body effective mass enhancement in a two-dimensional electron liquid
Motivated by a large number of recent magnetotransport studies we have
revisited the problem of the microscopic calculation of the quasiparticle
effective mass in a paramagnetic two-dimensional (2D) electron liquid (EL). Our
systematic study is based on a generalized approximation which makes use
of the many-body local fields and takes advantage of the results of the most
recent QMC calculations of the static charge- and spin-response of the 2D EL.
We report extensive calculations for the many-body effective mass enhancement
over a broad range of electron densities. In this respect we critically examine
the relative merits of the on-shell approximation, commonly used in
weak-coupling situations, {\it versus} the actual self-consistent solution of
the Dyson equation. We show that already for and higher, a
solution of the Dyson equation proves here necessary in order to obtain a well
behaved effective mass. Finally we also show that our theoretical results for a
quasi-2D EL, free of any adjustable fitting parameters, are in good qualitative
agreement with some recent measurements in a GaAs/AlGaAs heterostructure.Comment: 12 pages, 3 figures, CMT28 Conference Proceedings, work related to
cond-mat/041226
Single-particle and collective excitations in a charged Bose gas at finite temperature
The main focus of this work is on the predictions made by the dielectric
formalism in regard to the relationship between single-particle and collective
excitation spectra in a gas of point-like charged bosons at finite temperature
below the critical region of Bose-Einstein condensation. Illustrative
numerical results at weak coupling () are presented within the Random
Phase Approximation. We show that within this approach the single-particle
spectrum forms a continuum extending from the transverse to the longitudinal
plasma mode frequency and leading to a double-peak structure as increases,
whereas the density fluctuation spectrum consists of a single broadening peak.
We also discuss the momentum distribution and the superfluidity of the gas.Comment: 15 pages, 5 figure
Self-consistent Overhauser model for the pair distribution function of an electron gas at finite temperature
We present calculations of the spin-averaged pair distribution function
in a homogeneous gas of electrons moving in dimensionality D=3 or D=2 at
finite temperature. The model involves the solution of a two-electron
scattering problem via an effective potential which embodies many-body effects
through a self-consistent Hartree approximation, leading to two-body wave
functions to be averaged over a temperature-dependent distribution of relative
momentum for electron pairs. We report illustrative numerical results for
in an intermediate-coupling regime and interpret them in terms of
changes of short-range order with increasing temperature.Comment: 6 pages, 5 figures, submitted to Solid State Communication
- …