1,445 research outputs found
Electronic susceptibilities in systems with anisotropic Fermi surfaces
The low temperature dependence of the spin and charge susceptibilities of an
anisotropic electron system in two dimensions is analyzed. It is shown that the
presence of inflection points at the Fermi surface leads, generically, to a dependence, and a more singular behavior, ,
is also possible. Applications to quasi two-dimensional materials are
discussed.Comment: 8 pages, 5 figures, revtex 4 styl
Developing an Inclusive Learning Environment for Refugee Students in Higher Education
The purpose of this session is to facilitate a dialogue focused on creating an inclusive learning environment for a marginalized population of adult learners, refugee students in higher education
Was it a dream or nightmare? A narrative exploration of adult refugee learners’ experiences in a community college
Refugees enter the United States seeking a safe place to rebuild their lives after surviving life-threatening situations. In this journey, education is seen as a bridge from instability to self-sufficiency. The purpose of this narrative inquiry was to better understand the experiences of adult refugee learners as they navigate higher education in the United States. The research questions were: How do adult refugee learners’ prior life experiences influence the transition to higher education? How does the intersection of ethnicity and immigration status influence the higher education experience? and What strategies do adult refugee learners employ to navigate higher education
The Advantage of Increased Resolution in the Study of Quasar Absorption Systems
We compare a new R = 120,000 spectrum of PG1634+706 (z_QSO = 1.337,m_V =
14.9) obtained with the HDS instrument on Subaru to a R = 45, 000 spectrum
obtained previously with HIRES/Keck. In the strong MgII system at z = 0.9902
and the multiple cloud, weak MgII system at z = 1.0414, we find that at the
higher resolution, additional components are resolved in a blended profile. We
find that two single-cloud weak MgII absorbers were already resolved at R =
45,000, to have b = 2 - 4 km/s. The narrowest line that we measure in the R =
120, 000 spectrum is a component of the Galactic NaI absorption, with b =
0.90+/-0.20 km/s. We discuss expectations of similarly narrow lines in various
applications, including studies of DLAs, the MgI phases of strong MgII
absorbers, and high velocity clouds. By applying Voigt profile fitting to
synthetic lines, we compare the consistency with which line profile parameters
can be accurately recovered at R = 45,000 and R = 120,000. We estimate the
improvement gained from superhigh resolution in resolving narrowly separated
velocity components in absorption profiles. We also explore the influence of
isotope line shifts and hyperfine splitting in measurements of line profile
parameters, and the spectral resolution needed to identify these effects. Super
high resolution spectra of quasars, which will be routinely possible with
20-meter class telescopes, will lead to greater sensitivity for absorption line
surveys, and to determination of more accurate physical conditions for cold
phases of gas in various environments.Comment: To appear in AJ. Paper with better resolution images available at
http://www.astro.psu.edu/users/anand/superhigh.AJ.pd
Leading Temperature Corrections to Fermi Liquid Theory in Two Dimensions
We calculate the basic parameters of the Fermi Liquid: the scattering vertex,
the Landau interaction function, the effective mass, and physical
susceptibilities for a model of two-dimensional (2D) fermions with a short
ranged interaction at non-zero temperature. The leading temperature dependences
of the spin components of the scattering vertex, the Landau function, and the
spin susceptibility are found to be linear. T-linear terms in the effective
mass and in the ``charge-sector''- quantities are found to cancel to second
order in the interaction, but the cancellation is argued not to be generic. The
connection with previous studies of the 2D Fermi-Liquid parameters is
discussed.Comment: 4 pages, 1 figur
The Chemical and Ionization Conditions in Weak Mg II Absorbers
We present an analysis of the chemical and ionization conditions in a sample
of 100 weak Mg II absorbers identified in the VLT/UVES archive of quasar
spectra. Using a host of low ionization lines associated with each absorber in
this sample, and on the basis of ionization models, we infer that the
metallicity in a significant fraction of weak Mg II clouds is constrained to
values of solar or higher, if they are sub-Lyman limit systems. Based on the
observed constraints, we present a physical picture in which weak Mg II
absorbers are predominantly tracing two different astrophysical
processes/structures. A significant population of weak Mg II clouds, those in
which N(Fe II) is much less than N(Mg II), identified at both low (z ~ 1) and
high (z ~ 2) redshift, are potentially tracing gas in the extended halos of
galaxies, analogous to the Galactic high velocity clouds. These absorbers might
correspond to alpha-enhanced interstellar gas expelled from star-forming
galaxies, in correlated supernova events. On the other hand, N(FeII)
approximately equal to N(Mg II) clouds, which are prevalent only at lower
redshifts (z < 1.5), must be tracing Type Ia enriched gas in small, high
metallicity pockets in dwarf galaxies, tidal debris, or other intergalactic
structures.Comment: 35 pages (including tables & figures). Accepted for publication in
ApJ. A high resolution version of the paper is available at
"http://www.astro.wisc.edu/~anand/weakMgII.pdf
Neutron scattering and molecular correlations in a supercooled liquid
We show that the intermediate scattering function for neutron
scattering (ns) can be expanded naturely with respect to a set of molecular
correlation functions that give a complete description of the translational and
orientational two-point correlations in the liquid. The general properties of
this expansion are discussed with special focus on the -dependence and hints
for a (partial) determination of the molecular correlation functions from
neutron scattering results are given. The resulting representation of the
static structure factor is studied in detail for a model system using
data from a molecular dynamics simulation of a supercooled liquid of rigid
diatomic molecules. The comparison between the exact result for and
different approximations that result from a truncation of the series
representation demonstrates its good convergence for the given model system. On
the other hand it shows explicitly that the coupling between translational
(TDOF) and orientational degrees of freedom (ODOF) of each molecule and
rotational motion of different molecules can not be neglected in the
supercooled regime.Further we report the existence of a prepeak in the
ns-static structure factor of the examined fragile glassformer, demonstrating
that prepeaks can occur even in the most simple molecular liquids. Besides
examining the dependence of the prepeak on the scattering length and the
temperature we use the expansion of into molecular correlation
functions to point out intermediate range orientational order as its principle
origin.Comment: 13 pages, 7 figure
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