5,807 research outputs found
Fundamental Plane Distances to Early-type Field Galaxies in the South Equatorial Strip. I. The Spectroscopic Data
Radial velocities and central velocity dispersions are derived for 238 E/S0
galaxies from medium-resolution spectroscopy. New spectroscopic data have been
obtained as part of a study of the Fundamental Plane distances and peculiar
motions of early-type galaxies in three selected directions of the South
Equatorial Strip, undertaken in order to investigate the reality of large-scale
streaming motion; results of this study have been reported in M\"uller
(1998). The new APM South Equatorial Strip Catalog () was used to select the sample of field galaxies in
three directions: (1) 15h10 - 16h10; (2) 20h30 - 21h50; (3) 00h10 - 01h30. The
spectra obtained have a median S/N per of 23, an instrumental
resolution (FWHM) of 4 , and the spectrograph resolution
(dispersion) is 100 km~s. The Fourier cross-correlation method
was used to derive the radial velocities and velocity dispersions. The velocity
dispersions have been corrected for the size of the aperture and for the galaxy
effective radius. Comparisons of the derived radial velocities with data from
the literature show that our values are accurate to 40 km~s. A
comparison with results from J\orgensen et al. (1995) shows that the derived
central velocity dispersion have an rms scatter of 0.036 in .
There is no offset relative to the velocity dispersions of Davies et al.
(1987).Comment: accepted for publication in Astronomy & Astrophysics Supplement
Serie
Real Time Evolution in Quantum Many-Body Systems With Unitary Perturbation Theory
We develop a new analytical method for solving real time evolution problems
of quantum many-body systems. Our approach is a direct generalization of the
well-known canonical perturbation theory for classical systems. Similar to
canonical perturbation theory, secular terms are avoided in a systematic
expansion and one obtains stable long-time behavior. These general ideas are
illustrated by applying them to the spin-boson model and studying its
non-equilibrium spin dynamics.Comment: Final version as accepted for publication in Phys. Rev. B (4 pages, 3
figures
Localized low-frequency Neumann modes in 2d-systems with rough boundaries
We compute the relative localization volumes of the vibrational eigenmodes in
two-dimensional systems with a regular body but irregular boundaries under
Dirichlet and under Neumann boundary conditions. We find that localized states
are rare under Dirichlet boundary conditions but very common in the Neumann
case. In order to explain this difference, we utilize the fact that under
Neumann conditions the integral of the amplitudes, carried out over the whole
system area is zero. We discuss, how this condition leads to many localized
states in the low-frequency regime and show by numerical simulations, how the
number of the localized states and their localization volumes vary with the
boundary roughness.Comment: 7 pages, 4 figure
Similarity Renormalization Group for Nucleon-Nucleon Interactions
The similarity renormalization group (SRG) is based on unitary
transformations that suppress off-diagonal matrix elements, forcing the
hamiltonian towards a band-diagonal form. A simple SRG transformation applied
to nucleon-nucleon interactions leads to greatly improved convergence
properties while preserving observables, and provides a method to consistently
evolve many-body potentials and other operators.Comment: 5 pages, 6 figures (8 figure files); references updated and
acknowledgment adde
Dynamical scaling analysis of the optical Hall conductivity in the quantum Hall regime
Dynamical scaling analysis is theoretically performed for the ac (optical)
Hall conductivity as a function of Fermi
energy and frequency for the two-dimensional electron
gas and for graphene. In both systems, results based on exact diagonalization
show that displays a well-defined dynamical
scaling, for which the dynamical critical exponent as well as the localization
exponent are fitted and plugged in. A crossover from the dc-like bahavior to
the ac regime is identified. The dynamical scaling analysis has enabled us to
quantify the plateau in the ac Hall conductivity previously obtained, and to
predict that the plateaux structure in ac is robust enough to be observed in
the THz regime.Comment: 5 pages, 3 figure
First Order Superfluid to Bose Metal Transition in Systems with Resonant Pairing
Systems showing resonant superfluidity, driven by an exchange coupling of
strength between uncorrelated pairs of itinerant fermions and tightly bound
ones, undergo a first order phase transition as increases beyond some
critical value . The superfluid phase for is characterized by
a gap in the fermionic single particle spectrum and an acoustic sound-wave like
collective mode of the bosonic resonating fermion pairs inside this gap. For
this state gives way to a phase uncorrelated bosonic liquid with a
spectrum.Comment: 5 pages, 3 figure
Educating Lawyers: Preparation for the Profession of Law
Examines the unique aspects and limitations of legal education, as part of a series of reports from the foundation's Preparation for the Professions Program
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