48,298 research outputs found
Lowest Order Constrained Variational Calculation of the Polarized Nuclear Matter with the Modern Potential
The lowest order constrained variational method is applied to calculate the
polarized symmetrical nuclear matter properties with the modern
potential performing microscopic calculations. Results based on the
consideration of magnetic properties show no sign of phase transition to a
ferromagnetic phase.Comment: 19 pages, 6 figure
Non-Fermi-Liquid Behavior from the Fermi-Liquid Approach
Non-Fermi liquid behavior of strongly correlated Fermi systems is derived
within the Landau approach. We attribute this behavior to a phase transition
associated with a rearrangement of the Landau state that leads to flattening of
a portion of the single-particle spectrum in the vicinity
of the Fermi surface. We demonstrate that the quasiparticle subsystem
responsible for the flat spectrum possesses the same thermodynamic properties
as a gas of localized spins. Theoretical results compare favorably with
available experimental data. While departing radically from prevalent views on
the origin of non-Fermi-liquid behavior, the theory advanced here is
nevertheless a conservative one of in continuing to operate within the general
framework of Landau theory.Comment: 8 pages, 4 figures, corrected list of author
Breathing oscillations of a trapped impurity in a Bose gas
Motivated by a recent experiment [J. Catani et al., arXiv:1106.0828v1
preprint, 2011], we study breathing oscillations in the width of a harmonically
trapped impurity interacting with a separately trapped Bose gas. We provide an
intuitive physical picture of such dynamics at zero temperature, using a
time-dependent variational approach. In the Gross-Pitaevskii regime we obtain
breathing oscillations whose amplitudes are suppressed by self trapping, due to
interactions with the Bose gas. Introducing phonons in the Bose gas leads to
the damping of breathing oscillations and non-Markovian dynamics of the width
of the impurity, the degree of which can be engineered through controllable
parameters. Our results reproduce the main features of the impurity dynamics
observed by Catani et al. despite experimental thermal effects, and are
supported by simulations of the system in the Gross-Pitaevskii regime.
Moreover, we predict novel effects at lower temperatures due to self-trapping
and the inhomogeneity of the trapped Bose gas.Comment: 7 pages, 3 figure
The effect of quantization on the FCIQMC sign problem
The sign problem in Full Configuration Interaction Quantum Monte Carlo
(FCIQMC) without annihilation can be understood as an instability of the
psi-particle population to the ground state of the matrix obtained by making
all off-diagonal elements of the Hamiltonian negative. Such a matrix, and hence
the sign problem, is basis dependent. In this paper we discuss the properties
of a physically important basis choice: first versus second quantization. For a
given choice of single-particle orbitals, we identify the conditions under
which the fermion sign problem in the second quantized basis of antisymmetric
Slater determinants is identical to the sign problem in the first quantized
basis of unsymmetrized Hartree products. We also show that, when the two
differ, the fermion sign problem is always less severe in the second quantized
basis. This supports the idea that FCIQMC, even in the absence of annihilation,
improves the sign problem relative to first quantized methods. Finally, we
point out some theoretically interesting classes of Hamiltonians where first
and second quantized sign problems differ, and others where they do not.Comment: 4 pages w/ 2 page appendix, 2 figures, 1 tabl
Polarized Neutron Matter: A Lowest Order Constrained Variational Approach
In this paper, we calculate some of the polarized neutron matter properties,
using the lowest order constrained variational method with the
potential and employing a microscopic point of view. A comparison is also made
between our results and those of other many-body techniques.Comment: 23 pages, 8 figure
Crew Motion and the Dynamic Environment of Spaceborne Experiments
Analytical study of crew motion on dynamic environment of orbiting laboratorie
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