4,906 research outputs found
Multidimensional Bosonization
Bosonization of degenerate fermions yields insight both into Landau Fermi
liquids, and into non-Fermi liquids. We begin our review with a pedagogical
introduction to bosonization, emphasizing its applicability in spatial
dimensions greater than one. After a brief historical overview, we present the
essentials of the method. Well known results of Landau theory are recovered,
demonstrating that this new tool of many-body theory is robust. Limits of
multidimensional bosonization are tested by considering several examples of
non-Fermi liquids, in particular the composite fermion theory of the
half-filled Landau level. Nested Fermi surfaces present a different challenge,
and these may be relevant in the cuprate superconductors. We conclude by
discussing the future of multidimensional bosonization.Comment: 91 pages, 15 eps figures, LaTeX. Minor changes to match the published
versio
Hydrogeologic characterization of an alpine glacial till, Snowy Range, Wyoming
2011 Fall.Includes bibliographical references.Characterization of sediment hydraulic properties is essential to understanding groundwater movement. In many mountain watersheds, surficial geologic material, such as glacial till, plays an important role in water and nutrient chemical cycling. Hydraulic properties of alpine glacial tills are infrequently measured, requiring efforts to characterize this complex geologic material. This research involved the use of multiple measurement techniques to determine the saturated hydraulic conductivity of surficial glacial tills at the Glacier Lakes Ecosystem Experiments Site (GLEES) in south-central Wyoming. During the summer of 2010, three in situ methods (double-ring infiltrometer, mini disk infiltrometer, and Guelph permeameter) were used to measure field-saturated hydraulic conductivity (K sat) at 32 locations around GLEES. Estimated K sat values obtained with the double-ring infiltrometer had a geometric mean of 0.12 cm/min and range of 0.007 to 0.40 cm/min. The Guelph permeameter had a geometric mean of 0.094 cm/min and range of 0.003 cm/min to 0.776 cm/min, and the mini disk infiltrometer obtained estimates with a geometric mean of 0.014 cm/min and ranged from 0.002 cm/min to 0.043 cm/min. The double-ring infiltrometer and Guelph permeameter measure K sat at a physical scale that is large enough to incorporate the large mixture of particle sizes that comprise the till. With a smaller physical measurement scale, the mini disk is predominantly influenced by the fine-grained fraction of the till. Using geometric mean K sat values obtained with the double-ring and mini disk infiltrometers and available snowpack data from the 2005 water year, a physically-based hydrologic and energy-balance model was used to simulate snowpack depletion, soil moisture changes, and groundwater recharge. Simulated sediment moisture changes were used to estimate vertical flow rates toward the water table. Using a higher K sat obtained at a larger physical measurement scale, the calculated flow rate 2 m below the surface is approximately three times that of the low K sat scenarios. Thus, the scale dependency of hydraulic conductivity is important when quantifying groundwater recharge in mountain watersheds
Why the Universe Started from a Low Entropy State
We show that the inclusion of backreaction of massive long wavelengths
imposes dynamical constraints on the allowed phase space of initial conditions
for inflation, which results in a superselection rule for the initial
conditions. Only high energy inflation is stable against collapse due to the
gravitational instability of massive perturbations. We present arguments to the
effect that the initial conditions problem {\it cannot} be meaningfully
addressed by thermostatistics as far as the gravitational degrees of freedom
are concerned. Rather, the choice of the initial conditions for the universe in
the phase space and the emergence of an arrow of time have to be treated as a
dynamic selection.Comment: 12 pages, 2 figs. Final version; agrees with accepted version in
Phys. Rev.
Hall Effect in the mixed state of moderately clean superconductors
The Hall conductivity in the mixed state of a clean () type-II
s-wave superconductor is determined from a microscopic calculation within a
quasiclassical approximation. We find that below the superconducting transition
the contribution to the transverse conductivity due to dynamical fluctuations
of the order parameter is compensated by the modification of the quasiparticle
contribution. In this regime the nonlinear behaviour of the Hall angle is
governed by the change in the effective quasiparticle scattering rate due to
the reduction in the density of states at the Fermi level. The connection with
experimental results is discussed
Exact Nonperturbative Unitary Amplitudes for 1->N Transitions
I present an extension to arbitrary N of a previously proposed field
theoretic model, in which unitary amplitudes for processes were
obtained. The Born amplitude in this extension has the behavior
expected in a bosonic field theory. Unitarity
is violated when , or when Numerical
solutions of the coupled Schr\"odinger equations shows that for weak coupling
and a large range of N>\ncrit, the exact unitary amplitude is reasonably fit
by a factorized expression |A(1->N)| \sim (0.73 /N) \cdot \exp{(-0.025/\g2)}.
The very small size of the coefficient 1/\g2 , indicative of a very weak
exponential suppression, is not in accord with standard discussions based on
saddle point analysis, which give a coefficient The weak dependence
on could have experimental implications in theories where the exponential
suppression is weak (as in this model). Non-perturbative contributions to
few-point correlation functions in this theory would arise at order $K\ \simeq\
\left((0.05/\g2)+ 2\ ln{N}\right)/ \ ln{(1/\g2)}\g2.$Comment: 11 pages, 3 figures (not included
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