852 research outputs found
Charge-Spin Separation in 2D Fermi Systems: Singular Interactions as Modified Commutators, and Solution of 2D Hubbard Model in Bosonized Approximation
The general 2-dimensional fermion system with repulsive interactions
(typified by the Hubbard Model) is bosonized, taking into account the finite
on-shell forward scattering phase shift derived in earlier papers. By taking
this phase shift into account in the bosonic commutation relations a consistent
picture emerges showing the charge-spin separation and anomalous exponents of
the Luttinger liquid.Comment: Latex file 14 pages. email: [email protected]
Does Liver Transplantation in the Rat Cause a Regenerative Response
This study was conducted to determine the pattern of early regenerative response to orthotopic intact
liver transplantation in the rat and to investigate whether the response differed in grafts with or without
revascularisation of the arterial bed
Oxygen consumption rate of Caenorhabditis elegans as a high-throughput endpoint of toxicity testing using the Seahorse XF(e)96 Extracellular Flux Analyzer
Du Preez G, Fourie H, Daneel M, et al. Oxygen consumption rate of Caenorhabditis elegans as a high-throughput endpoint of toxicity testing using the Seahorse XF(e)96 Extracellular Flux Analyzer. Scientific Reports. 2020;10(1): 4239.Caenorhabditis elegans presents functioning, biologically relevant phenotypes and is frequently used as a bioindicator of toxicity. However, most C. elegans in vivo effect-assessment methods are laborious and time consuming. Therefore, we developed a novel method to measure the oxygen consumption rate of C. elegans as a sublethal endpoint of toxicity. This protocol was tested by exposing 50 larval stage one C. elegans individuals for 48h (at 20 degrees C) to different concentrations of two toxicants i.e. benzylcetyldimethylammonium chloride (BAC-C16) and cadmium (Cd). Following exposures, the oxygen consumption rate of the C. elegans individuals were measured using the high-throughput functionality of the Seahorse XF(e)96 Extracellular Flux Analyzer. Dose-response curves for BAC-C16 (R-2=0.93; P=0.001) and Cd (R-2=0.98; P=0.001) were created. Furthermore, a strong, positive correlation was evidenced between C. elegans oxygen consumption rate and a commonly used, ecologically relevant endpoint of toxicity (growth inhibition) for BAC-C16 (R-2=0.93; P=0.0001) and Cd (R-2=0.91; P=0.0001). The data presented in this study show that C. elegans oxygen consumption rate can be used as a promising functional measurement of toxicity
Spin-Charge Separation, Anomalous Scaling and the Coherence of Hopping in exactly solved Two Chain Models
The coherence of transport between two one-dimensional interacting Fermi
liquids, coupled by single particle hopping and interchain interaction, is
examined in the context of two exactly soluble models. It is found that the
coherence of the inter-chain hopping depends on the interplay between
inter-chain hopping and inter-chain interaction terms, and not simply on the
ground state spectral properties of an isolated chain. Specifically, the
splitting of levels in associated with interchain hopping in a soluble
model is found to be enhanced by the introduction of interchain interaction. It
is also shown that, for an exactly solvable model with both and
interactions, coherent interchain hopping coexists with anomalous scaling and
non-Fermi liquid behavior in the chain direction.Comment: Two postscript figure
Single-Particle Properties of a Two-Dimensional Fermi Liquid at finite Frequencies and Temperatures
We review the leading momentum, frequency and temperature dependences of the
single particle self-energy and the corresponding term in the entropy of a two
dimensional Fermi liquid (FL) with a free particle spectrum. We calculate the
corrections to these leading dependences for the paramagnon model and the
electron gas and find that the leading dependences are limited to regions of
energy and temperature which decrease with decreasing number density of
fermions. This can make it difficult to identify the frequency and temperature
dependent characteristics of a FL ground state in experimental quantities in
low density systems even when complications of band structure and other degrees
of freedom are absent. This is an important consideration when the normal state
properties of the undoped cuprate superconductors are analyzed.Comment: Revtex, 15 pages with 13 figures. minor corrections. Accepted for
publication in Phy. Rev.
BCS-BEC crossover at finite temperature in the broken-symmetry phase
The BCS-BEC crossover is studied in a systematic way in the broken-symmetry
phase between zero temperature and the critical temperature. This study bridges
two regimes where quantum and thermal fluctuations are, respectively,
important. The theory is implemented on physical grounds, by adopting a
fermionic self-energy in the broken-symmetry phase that represents fermions
coupled to superconducting fluctuations in weak coupling and to bosons
described by the Bogoliubov theory in strong coupling. This extension of the
theory beyond mean field proves important at finite temperature, to connect
with the results in the normal phase. The order parameter, the chemical
potential, and the single-particle spectral function are calculated numerically
for a wide range of coupling and temperature. This enables us to assess the
quantitative importance of superconducting fluctuations in the broken-symmetry
phase over the whole BCS-BEC crossover. Our results are relevant to the
possible realizations of this crossover with high-temperature cuprate
superconductors and with ultracold fermionic atoms in a trap.Comment: 21 pages, 15 figure
Theory of the temperature and doping dependence of the Hall effect in a model with x-ray edge singularities in d=oo
We explain the anomalous features in the Hall data observed experimentally in
the normal state of the high-Tc superconductors. We show that a consistent
treatment of the local spin fluctuations in a model with x-ray edge
singularities in d=oo reproduces the temperature and the doping dependence of
the Hall constant as well as the Hall angle in the normal state. The model has
also been invoked to justify the marginal-Fermi-liquid behavior, and provides a
consistent explanation of the Hall anomalies for a non-Fermi liquid in d=oo.Comment: 5 pages, 4 figures, To appear in Phys. Rev. B, title correcte
Coherent quasiparticle weight and its connection to high-T_c superconductivity from angle-resolved photoemission
In conventional superconductors, the pairing energy gap (\Delta) and
superconducting phase coherence go hand-in-hand. As the temperature is lowered,
both the energy gap and phase coherence appear at the transition temperature
T_c. In contrast, in underdoped high-T_c superconductors (HTSCs), a pseudogap
appears at a much higher temperature T^*, smoothly evolving into the
superconducting gap at T_c. Phase coherence on the other hand is only
established at T_c, signaled by the appearance of a sharp quasiparticle (QP)
peak in the excitation spectrum. Another important difference between the two
types of superconductors is in the ratio of 2\Delta / T_c=R. In BCS theory,
R~3.5, is constant. In the HTSCs this ratio varies widely, continuing to
increase in the underdoped region, where the gap increases while T_c decreases.
Here we report that in HTSCs it is the ratio z_A\Delta_m/T_c which is
approximately constant, where \Delta_m is the maximum value of the d-wave gap,
and z_A is the weight of the coherent excitations in the spectral function.
This is highly unusual, since in nearly all phase transitions, T_c is
determined by an energy scale alone. We further show that in the
low-temperature limit, z_{\it A} increases monotonically with increasing doping
x. The growth is linear, i.e. z_A(x)\propto x, in the underdoped to optimally
doped regimes, and slows down in overdoped samples. The reduction of z_A with
increasing temperature resembles that of the c-axis superfluid density.Comment: 11 pages, 5 figures, revised versio
Nesting Induced Precursor Effects: a Renormalization Group Approach
We develop a controlled weak coupling renormalization group (RG) approach to
itinerant electrons. Within this formalism we rederive the phase diagram for
two-dimensional (2D) non-nested systems. Then we study how nesting modifies
this phase diagram. We show that competition between p-p and p-h channels,
leads to the manifestation of unstable precursor fixed points in the RG flow.
This effect should be experimentally measurable, and may be relevant for an
explanation of pseudogaps in the high temperature superconductors (HTC), as a
crossover phenomenon.Comment: 4 pages, 4 figures, 1 tabl
Signatures of the correlation hole in total and partial cross sections
In a complex scattering system with few open channels, say a quantum dot with
leads, the correlation properties of the poles of the scattering matrix are
most directly related to the internal dynamics of the system. We may ask how to
extract these properties from an analysis of cross sections. In general this is
very difficult, if we leave the domain of isolated resonances. We propose to
consider the cross correlation function of two different elastic or total cross
sections. For these we can show numerically and to some extent also
analytically a significant dependence on the correlations between the
scattering poles. The difference between uncorrelated and strongly correlated
poles is clearly visible, even for strongly overlapping resonances.Comment: 25 pages, 13 Postscript figures, typos corrected and references adde
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