64,178 research outputs found
Density Expansion for the Mobility in a Quantum Lorentz Model
We consider the mobility of electrons in an environment of static hard-sphere
scatterers, which provides a realistic description of electrons in Helium gas.
A systematic expansion in the scatterer density is carried to second order
relative to the Boltzmann result, and the analytic contribution at this order
is derived, together with the known logarithmic term in the density expansion.
It is shown that existing experimental data are consistent with the existence
of the logarithmic term in the density expansion, but more precise experiments
are needed in order to unambiguously detect it. We show that our calculations
provide the necessary theoretical information for such an experiment, and give
a detailed discussion of a suitable parameter range.Comment: 17pp., REVTeX, 7 figure attached as 8 postscript files, db/94/
BFT Hamiltonian embedding for SU(3) Skyrmion
We newly apply the Batalin, Fradkin and Tyutin (BFT) formalism to the SU(3)
flavor Skyrmion model to investigate the Weyl ordering correction to the
structure of the hyperfine splittings of strange baryons. On the other hand,
the Berry phases and Casimir effects are also discussed.Comment: 14 pages, modified titl
Paired and altruistic kidney donation in the UK: algorithms and experimentation
We study the computational problem of identifying optimal
sets of kidney exchanges in the UK. We show how to expand an integer
programming-based formulation [1, 19] in order to model the criteria that
constitute the UK definition of optimality. The software arising from this
work has been used by the National Health Service Blood and Transplant
to find optimal sets of kidney exchanges for their National Living Donor
Kidney Sharing Schemes since July 2008.We report on the characteristics
of the solutions that have been obtained in matching runs of the scheme
since this time. We then present empirical results arising from the real
datasets that stem from these matching runs, with the aim of establishing
the extent to which the particular optimality criteria that are present
in the UK influence the structure of the solutions that are ultimately
computed. A key observation is that allowing 4-way exchanges would be
likely to lead to a significant number of additional transplants
The spectral properties of the Falicov-Kimball model in the weak-coupling limit
The and electron density of states of the one-dimensional
Falicov-Kimball model are studied in the weak-coupling limit by exact
diagonalization calculations. The resultant behaviors are used to examine the
-electron gap (), the -electron gap (), and the
-electron gap () as functions of the -level energy
and hybridization . It is shown that the spinless Falicov-Kimball model
behaves fully differently for zero and finite hybridization between and
states. At zero hybridization the energy gaps do not coincide (), and the activation gap vanishes
discontinuously at some critical value of the -level energy . On the
other hand, at finite hybridization all energy gaps coincide and vanish
continuously at the insulator-metal transition point . The
importance of these results for a description of real materials is discussed.Comment: 10 pages, 7 figures, LaTe
Strange Quark PDFs and Implications for Drell-Yan Boson Production at the LHC
Global analyses of Parton Distribution Functions (PDFs) have provided
incisive constraints on the up and down quark components of the proton, but
constraining the other flavor degrees of freedom is more challenging.
Higher-order theory predictions and new data sets have contributed to recent
improvements. Despite these efforts, the strange quark PDF has a sizable
uncertainty, particularly in the small x region. We examine the constraints
from experiment and theory, and investigate the impact of this uncertainty on
LHC observables. In particular, we study W/Z production to see how the s-quark
uncertainty propagates to these observables, and examine the extent to which
precise measurements at the LHC can provide additional information on the
proton flavor structure.Comment: 14 pages, 11 figures, added reference
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