13,401 research outputs found
Cosmic Evolution of Black Holes and Spheroids. II: Scaling Relations at z=0.36
We combine Hubble Space Telescope images of a sample of 20 Seyfert galaxies
at z=0.36 with spectroscopic information from the Keck Telescope to determine
the black hole mass - spheroid luminosity relation (M-L), the Fundamental Plane
(FP) of the host galaxies and the M-sigma relation. Assuming pure luminosity
evolution, we find that the host spheroids had smaller luminosity and stellar
velocity dispersion than today for a fixed M. The offsets correspond to Delta
log L_B,0=0.40+-0.11+-0.15 (Delta log M = 0.51+-0.14+-0.19) and Delta log sigma
= 0.13+-0.03+-0.05 (Delta log M = 0.54+-0.12+-0.21), respectively for the M-L
and M-sigma relation. A detailed analysis of known systematic errors and
selection effects shows that they cannot account for the observed offset. The
data are inconsistent with pure luminosity evolution and the existence of
universal and tight scaling relations. To obey the three local scaling
relations by z=0 the distant spheroids have to grow their stellar mass by
approximately 60% (\Delta log M_sph=0.20+-0.14) in the next 4 billion years.
The measured evolution can be expressed as M/ M_sph ~ (1+z)^{1.5+-1.0}. Based
on the disturbed morphologies of a fraction of the sample (6/20) we suggest
collisional mergers with disk-dominated systems as evolutionary mechanism.Comment: 17 pages, 10 figures; accepted for publication in the Astrophysical
Journa
Performance of a family of omni and steered antennas for mobile satellite applications
The design and performance of a family of vehicle antennas developed at JPL in support of an emerging US Mobile Satellite Service (MSS) system are described. Test results of the antennas are presented. Trends for future development are addressed. Recommendations on design approaches for vehicle antennas of the first generation MSS are discussed
Curvature-induced spin-orbit coupling and spin relaxation in a chemically clean single-layer graphene
The study of spin-related phenomena in materials requires knowledge on the
precise form of effective spin-orbit coupling of conducting carriers in the
solid-states systems. We demonstrate theoretically that curvature induced by
corrugations or periodic ripples in single-layer graphenes generates two types
of effective spin-orbit coupling. In addition to the spin-orbit coupling
reported previously that couples with sublattice pseudospin and corresponds to
the Rashba-type spin-orbit coupling in a corrugated single-layer graphene,
there is an additional spin-orbit coupling that does not couple with the
pseudospin, which can not be obtained from the extension of the
curvature-induced spin-orbit coupling of carbon nanotubes. Via numerical
calculation we show that both types of the curvature-induced spin-orbit
coupling make the same order of contribution to spin relaxation in chemically
clean single-layer graphene with nanoscale corrugation. The spin relaxation
dependence on the corrugation roughness is also studied.Comment: 8 pages, 4 figure
A review of High Performance Computing foundations for scientists
The increase of existing computational capabilities has made simulation
emerge as a third discipline of Science, lying midway between experimental and
purely theoretical branches [1, 2]. Simulation enables the evaluation of
quantities which otherwise would not be accessible, helps to improve
experiments and provides new insights on systems which are analysed [3-6].
Knowing the fundamentals of computation can be very useful for scientists, for
it can help them to improve the performance of their theoretical models and
simulations. This review includes some technical essentials that can be useful
to this end, and it is devised as a complement for researchers whose education
is focused on scientific issues and not on technological respects. In this
document we attempt to discuss the fundamentals of High Performance Computing
(HPC) [7] in a way which is easy to understand without much previous
background. We sketch the way standard computers and supercomputers work, as
well as discuss distributed computing and discuss essential aspects to take
into account when running scientific calculations in computers.Comment: 33 page
Controlling quasiparticle excitations in a trapped Bose-Einstein condensate
We describe an approach to quantum control of the quasiparticle excitations
in a trapped Bose-Einstein condensate based on adiabatic and diabatic changes
in the trap anisotropy. We describe our approach in the context of Landau-Zener
transition at the avoided crossings in the quasiparticle excitation spectrum.
We show that there can be population oscillation between different modes at the
specific aspect ratios of the trapping potential at which the mode energies are
almost degenerate. These effects may have implications in the expansion of an
excited condensate as well as the dynamics of a moving condensate in an atomic
wave guide with a varying width
Bell inequality for pairs of particle-number-superselection-rule restricted states
Proposals for Bell inequality tests on systems restricted by superselection
rules often require operations that are difficult to implement in practice. In
this paper, we derive a new Bell inequality, where pairs of states are used to
by-pass the superselection rule. In particular, we focus on mode entanglement
of an arbitrary number of massive particles and show that our Bell inequality
detects the entanglement in the pair when other inequalities fail. However, as
the number of particles in the system increases, the violation of our Bell
inequality decreases due to the restriction in the measurement space caused by
the superselection rule. This Bell test can be implemented using techniques
that are routinely used in current experiments.Comment: 9 pages, 6 figures; v2 is the published versio
Effects of pressure on the ferromagnetic state of the CDW compound SmNiC2
We report the pressure response of charge-density-wave (CDW) and
ferromagnetic (FM) phases of the rare-earth intermetallic SmNiC2 up to 5.5 GPa.
The CDW transition temperature (T_{CDW}), which is reflected as a sharp
inflection in the electrical resistivity, is almost independent of pressure up
to 2.18 GPa but is strongly enhanced at higher pressures, increasing from 155.7
K at 2.2 GPa to 279.3 K at 5.5 GPa. Commensurate with the sharp increase in
T_{CDW}, the first-order FM phase transition, which decreases with applied
pressure, bifurcates into the upper (T_{M1}) and lower (T_c) phase transitions
and the lower transition changes its nature to second order above 2.18 GPa.
Enhancement both in the residual resistivity and the Fermi-liquid T^2
coefficient A near 3.8 GPa suggests abundant magnetic quantum fluctuations that
arise from the possible presence of a FM quantum critical point.Comment: 5 pages, 5 figure
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