553 research outputs found
A Heavy Fermion Can Create a Soliton: A 1+1 Dimensional Example
We show that quantum effects can stabilize a soliton in a model with no
soliton at the classical level. The model has a scalar field chirally coupled
to a fermion in 1+1 dimensions. We use a formalism that allows us to calculate
the exact one loop fermion contribution to the effective energy for a spatially
varying scalar background. This energy includes the contribution from
counterterms fixed in the perturbative sector of the theory. The resulting
energy is therefore finite and unambiguous. A variational search then yields a
fermion number one configuration whose energy is below that of a single free
fermion.Comment: 10 pages, RevTeX, 2 figures composed from 4 .eps files; v2: fixed
minor errors, added reference; v3: corrected reference added in v
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Radon Measurements at the Molten Salt Reactor Experiment (MSRE) Facility from August 1997 through April 1998
From August 1997 through April 1998, radon and radon progeny measurements were collected at the Molten Salt Reactor Experiment (MSRE) facility at Oak Ridge National Laboratory. The purpose of the measurements was to determine the baseline concentrations of 222Rn (radon), 220Rn (thoron), and their progeny in the air at selected points with emphasis on the characterization of 220Rn and its daughter products in the high bay area. The daughter product concentrations ranged from the equivalent of approximately 0.001 times the derived air concentration (DAC) of the isotope mixture up to 0.09 DAC, with the highest measurements occurring inside the pit above the equipment drain tank cell. Direct radon measurements in this area indicated a relatively constant 222Rn concentration with an average value of 1.4 pCi/L and a 220Rn concentration that fluctuated from <1 pCi/L up to about 30 pCi/L. Measurements were also collected inside the vent house adjacent to building 7503. The progeny concentrations inside the room ranged from an equivalent of about 0.002 DAC up to 0.01 DAC. The direct radon measurements in the vent house indicated a relatively constant 222Rn concentration with an average value of 0.7 pCi/L while the 220Rn concentration varied appreciably and ranged from <0.5 pCi/L up to almost 200 pCi/L with an average concentration of 18 pCi/L
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Supplemental Release Limits for the Directed Reuse of Lead in Shielding Products by the Department of Energy
The DOE National Center of Excellence for Metals Recycle (NMR) proposes to define and implement a complex-wide directed reuse strategy for surplus radiologically impacted lead (Pb) as part of the U.S. Department of Energy's commitment to the safe and cost-effective recycle or reuse of excess materials and equipment across the DOE complex. NMR will, under this proposal, act on behalf of the DOE Office of Environmental Management, Office of Technical Program Integration (specifically EM-22), as the Department's clearinghouse for DOE surplus lead and lead products by developing and maintaining a cost-effective commercially-based contaminated lead recycle program. It is NMR's intention, through this directed reuse strategy, to mitigate the adverse environmental and economic consequences of managing surplus lead as a waste within the complex. This approach would promote the safe and cost-effective reuse of DOE's scrap and surplus lead in support of the Department's goals of resource utilization, energy conservation, pollution prevention and waste minimization. This report discusses recommendations for supplemental radiological limits for the directed reuse of contaminated lead and lead products by the DOE within the nuclear industry. The limits were selected--with slight modification--from the recently published American National Standards Institute and Health Physics Society standard N13.12 titled Surface and Volume Radioactivity Standards for Clearance (ANSI/HPS 1999) and are being submitted for formal approval by the DOE. Health and measurement implications from the adoption and use of the limits for directed reuse scenarios are discussed within this report
Introduction
Nando Sigona, Alan Gamlen, Giulia Libertore, Hélène Neveu-Kringelbac
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Supplemental Release Limits for the Directed Reuse of Steel in Road Barriers and Lead in Shielding Products by the Department of Energy
The DOE National Center of Excellence for Metals Recycle (NMR) proposes to define and implement a complex-wide directed reuse strategy for surplus radiologically impacted lead (Pb) and steel as part of the U.S. Department of Energy's commitment to the safe and cost-effective recycle or reuse of excess materials and equipment across the DOE complex. NMR will, under this proposal, act on behalf of the DOE Office of Environmental Management, Office of Technical Program Integration (specifically EM-22), as the Department's clearinghouse for DOE surplus lead, steel and products created from these materials by developing and maintaining a cost-effective commercially-based contaminated lead and steel recycle program. It is NMR's intention, through this directed reuse strategy, to mitigate the adverse environmental and economic consequences of managing surplus lead and steel as a waste within the complex. This approach promotes the safe and cost-effective reuse of scrap metals in support of the Department's goals of resource utilization, energy conservation, pollution prevention and waste minimization. This report discusses recommendations for supplemental radiological release limits for the directed reuse of contaminated lead and steel by the DOE within the nuclear industry. The limits were originally selected from the American National Standards Institute and Health Physics Society standard N13.12 titled ''Surface and Volume Radioactivity Standards for Clearance'' (Health Physics Society, 1999) but were subsequently modified as a result of application-specific issues. Both the health and measurement implications from the adoption and use of the limits for directed reuse scenarios are discussed within this report
A Note on Fluxes and Superpotentials in M-theory Compactifications on Manifolds of G_2 Holonomy
We consider the breaking of N=1 supersymmetry by non-zero G-flux when
M-theory is compactified on a smooth manifold X of G_2 holonomy. Gukov has
proposed a superpotential W to describe this breaking in the low-energy
effective theory. We check this proposal by comparing the bosonic potential
implied by W with the corresponding potential deduced from the
eleven-dimensional supergravity action. One interesting aspect of this check is
that, though W depends explicitly only on G-flux supported on X, W also
describes the breaking of supersymmetry by G-flux transverse to X.Comment: 15 pages, harvmac, v2: reference adde
Heavy Fermion Stabilization of Solitons in 1+1 Dimensions
We find static solitons stabilized by quantum corrections in a
(1+1)-dimensional model with a scalar field chirally coupled to fermions. This
model does not support classical solitons. We compute the renormalized energy
functional including one-loop quantum corrections. We carry out a variational
search for a configuration that minimizes the energy functional. We find a
nontrivial configuration with fermion number whose energy is lower than the
same number of free fermions quantized about the translationally invariant
vacuum. In order to compute the quantum corrections for a given background
field we use a phase-shift parameterization of the Casimir energy. We identify
orders of the Born series for the phase shift with perturbative Feynman
diagrams in order to renormalize the Casimir energy using perturbatively
determined counterterms. Generalizing dimensional regularization, we
demonstrate that this procedure yields a finite and unambiguous energy
functional.Comment: 27 papes Latex, equation labels corrected, version to be published in
Nucl. Phys.
Drum vortons in high density QCD
Recently it was shown that high density QCD supports of number of topological
defects. In particular, there are U(1)_Y strings that arise due to K^0
condensation that occurs when the strange quark mass is relatively large. The
unique feature of these strings is that they possess a nonzero K^+ condensate
that is trapped on the core. In the following we will show that these strings
(with nontrivial core structure) can form closed loops with conserved charge
and currents trapped on the string worldsheet. The presence of conserved
charges allows these topological defects, called vortons, to carry angular
momentum, which makes them classically stable objects. We also give arguments
demonstrating that vortons carry angular momentum very efficiently (in terms of
energy per unit angular momentum) such that they might be the important degrees
of freedom in the cores of neutron stars.Comment: 11 pages, accepted for publication in Physical Review
Dimensional Changes in Dental Stone and Plaster
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66786/2/10.1177_00220345500290060601.pd
Parity Doubling Among the Baryons
We study the evidence for and possible origins of parity doubling among the
baryons. First we explore the experimental evidence, finding a significant
signal for parity doubling in the non-strange baryons, but little evidence
among strange baryons. Next we discuss potential explanations for this
phenomenon. Possibilities include suppression of the violation of the flavor
singlet axial symmetry () of QCD, which is broken by the triangle
anomaly and by quark masses. A conventional Wigner-Weyl realization of the
chiral symmetry would also result in parity
doubling. However this requires the suppression of families of \emph{chirally
invariant} operators by some other dynamical mechanism. In this scenario the
parity doubled states should decouple from pions. We discuss other explanations
including connections to chiral invariant short distance physics motivated by
large arguments as suggested by Shifman and others, and intrinsic
deformation of relatively rigid highly excited hadrons, leading to parity
doubling on the leading Regge trajectory. Finally we review the spectroscopic
consequences of chiral symmetry using a formalism introduced by Weinberg, and
use it to describe two baryons of opposite parity.Comment: 32 pages, 8 figures; v2 revised and expanded; submitted to Phys. Re
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