1,200 research outputs found
A remotely-operated facility for evaluation of post-combustion CO2 capture technologies on industrial sites
ACTTROM (Advanced Capture Testing in a Transportable Remotely-Operated Minilab) is a transportable test facility for bench-scale evaluation of postcombustion CO2 capture technologies using real industrial flue gases. It is designed to be remote-operable, requiring visits only once per month for maintenance and sample collection. ACTTROM is the first facility of its kind, owned and operated by academia for collaborative research in an industrial environment, and this has resulted in a number of unique developments to facilitate remote operation at an industrial host site. Specifically, it has been necessary to design the unit to automatically correct or mitigate the effects of fault conditions, and to be remotely-monitored via a user interface at 24 hour intervals
Poincare Invariant Three-Body Scattering
Relativistic Faddeev equations for three-body scattering are solved at
arbitrary energies in terms of momentum vectors without employing a partial
wave decomposition. Relativistic invariance is incorporated withing the
framework of Poincar\'e invariant quantum mechanics. Based on a Malfliet-Tjon
interaction, observables for elastic and breakup scattering are calculated and
compared to non-relativistic ones.Comment: 4 pages, 2 figures. Proceedings of the workshop "Critical Stability
of Few-Body Quantum Systems" 200
A (Running) Bolt for New Reasons
We construct a four-parameter family of smooth, horizonless, stationary
solutions of ungauged five-dimensional supergravity by using the
four-dimensional Euclidean Schwarzschild metric as a base space and
"magnetizing" its bolt. We then generalize this to a five-parameter family
based upon the Euclidean Kerr-Taub-Bolt. These "running Bolt" solutions are
necessarily non-static. They also have the same charges and mass as a
non-extremal black hole with a classically-large horizon area. Moreover, in a
certain regime their mass can decrease as their charges increase. The existence
of these solutions supports the idea that the singularities of non-extremal
black holes are resolved by low-mass modes that correct the singularity of the
classical black hole solution on large (horizon-sized) scales.Comment: 25 pages, 3 figures, LaTeX; v2: minor changes, references adde
How quantum bound states bounce and the structure it reveals
We investigate how quantum bound states bounce from a hard surface. Our
analysis has applications to ab initio calculations of nuclear structure and
elastic deformation, energy levels of excitons in semiconductor quantum dots
and wells, and cold atomic few-body systems on optical lattices with sharp
boundaries. We develop the general theory of elastic reflection for a composite
body from a hard wall. On the numerical side we present ab initio calculations
for the compression of alpha particles and universal results for two-body
states. On the analytical side we derive a universal effective potential that
gives the reflection scattering length for shallow two-body states.Comment: final publication version, new lattice results on alpha particle
compression, 5 pages, 2 figure
Spin in relativistic quantum theory
We discuss the role of spin in Poincar\'e invariant formulations of quantum
mechanics.Comment: 54 page
Two-Nucleon Scattering without partial waves using a momentum space Argonne V18 interaction
We test the operator form of the Fourier transform of the Argonne V18
potential by computing selected scattering observables and all Wolfenstein
parameters for a variety of energies. These are compared to the GW-DAC database
and to partial wave calculations. We represent the interaction and transition
operators as expansions in a spin-momentum basis. In this representation the
Lippmann-Schwinger equation becomes a six channel integral equation in two
variables. Our calculations use different numbers of spin-momentum basis
elements to represent the on- and off-shell transition operators. This is
because different numbers of independent spin-momentum basis elements are
required to expand the on- and off-shell transition operators. The choice of on
and off-shell spin-momentum basis elements is made so that the coefficients of
the on-shell spin-momentum basis vectors are simply related to the
corresponding off-shell coefficients.Comment: 14 pages, 8 Figures, typos correcte
Effective DBHF Method for Asymmetric Nuclear Matter and Finite Nuclei
A new decomposition of the Dirac structure of nucleon self-energies in the
Dirac Brueckner-Hartree-Fock (DBHF) approach is adopted to investigate the
equation of state for asymmetric nuclear matter. The effective coupling
constants of , , and mesons with a density
dependence in the relativistic mean field approach are deduced by reproducing
the nucleon self-energy resulting from the DBHF at each density for symmetric
and asymmetric nuclear matter. With these couplings the properties of finite
nuclei are investigated. The agreement of charge radii and binding energies of
finite nuclei with the experimental data are improved simultaneously in
comparison with the projection method. It seems that the properties of finite
nuclei are sensitive to the scheme used for the DBHF self-energy extraction. We
may conclude that the properties of the asymmetric nuclear matter and finite
nuclei could be well described by the new decomposition approach of the G
matrix.Comment: 16 pages, 5 figure
Quantum Computing with Atomic Josephson Junction Arrays
We present a quantum computing scheme with atomic Josephson junction arrays.
The system consists of a small number of atoms with three internal states and
trapped in a far-off resonant optical lattice. Raman lasers provide the
"Josephson" tunneling, and the collision interaction between atoms represent
the "capacitive" couplings between the modes. The qubit states are collective
states of the atoms with opposite persistent currents. This system is closely
analogous to the superconducting flux qubit. Single qubit quantum logic gates
are performed by modulating the Raman couplings, while two-qubit gates result
from a tunnel coupling between neighboring wells. Readout is achieved by tuning
the Raman coupling adiabatically between the Josephson regime to the Rabi
regime, followed by a detection of atoms in internal electronic states.
Decoherence mechanisms are studied in detail promising a high ratio between the
decoherence time and the gate operation time.Comment: 7 figure
Computational Nuclear Physics and Post Hartree-Fock Methods
We present a computational approach to infinite nuclear matter employing
Hartree-Fock theory, many-body perturbation theory and coupled cluster theory.
These lectures are closely linked with those of chapters 9, 10 and 11 and serve
as input for the correlation functions employed in Monte Carlo calculations in
chapter 9, the in-medium similarity renormalization group theory of dense
fermionic systems of chapter 10 and the Green's function approach in chapter
11. We provide extensive code examples and benchmark calculations, allowing
thereby an eventual reader to start writing her/his own codes. We start with an
object-oriented serial code and end with discussions on strategies for porting
the code to present and planned high-performance computing facilities.Comment: 82 pages, to appear in Lecture Notes in Physics (Springer), "An
advanced course in computational nuclear physics: Bridging the scales from
quarks to neutron stars", M. Hjorth-Jensen, M. P. Lombardo, U. van Kolck,
Editor
Renormalization group approach to an Abelian sandpile model on planar lattices
One important step in the renormalization group (RG) approach to a lattice
sandpile model is the exact enumeration of all possible toppling processes of
sandpile dynamics inside a cell for RG transformations. Here we propose a
computer algorithm to carry out such exact enumeration for cells of planar
lattices in RG approach to Bak-Tang-Wiesenfeld sandpile model [Phys. Rev. Lett.
{\bf 59}, 381 (1987)] and consider both the reduced-high RG equations proposed
by Pietronero, Vespignani, and Zapperi (PVZ) [Phys. Rev. Lett. {\bf 72}, 1690
(1994)] and the real-height RG equations proposed by Ivashkevich [Phys. Rev.
Lett. {\bf 76}, 3368 (1996)]. Using this algorithm we are able to carry out RG
transformations more quickly with large cell size, e.g. cell for
the square (sq) lattice in PVZ RG equations, which is the largest cell size at
the present, and find some mistakes in a previous paper [Phys. Rev. E {\bf 51},
1711 (1995)]. For sq and plane triangular (pt) lattices, we obtain the only
attractive fixed point for each lattice and calculate the avalanche exponent
and the dynamical exponent . Our results suggest that the increase of
the cell size in the PVZ RG transformation does not lead to more accurate
results. The implication of such result is discussed.Comment: 29 pages, 6 figure
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