1,647 research outputs found
Exact Analysis of Entanglement in Gapped Quantum Spin Chains
We investigate the entanglement properties of the valence-bond-solid states
with generic integer-spin . Using the Schwinger boson representation of the
valence-bond-solid states, the entanglement entropy, the von Neumann entropy of
a subsystem, is obtained exactly and its relationship with the usual
correlation function is clarified. The saturation value of the entanglement
entropy, , is derived explicitly and is interpreted in terms of
the edge-state picture. The validity of our analytical results and the
edge-state picture is numerically confirmed. We also propose a novel
application of the edge state as a qubit for quantum computation.Comment: 4 pages, 2 figure
Passive spiral formation from halo gas starvation: Gradual transformation into S0s
Recent spectroscopic and high resolution -imaging observations have
revealed significant numbers of ``passive'' spiral galaxies in distant
clusters, with all the morphological hallmarks of a spiral galaxy (in
particular, spiral arm structure), but with weak or absent star formation.
Exactly how such spiral galaxies formed and whether they are the progenitors of
present-day S0 galaxies is unclear. Based on analytic arguments and numerical
simulations of the hydrodynamical evolution of a spiral galaxy's halo gas
(which is a likely candidate for the source of gas replenishment for star
formation in spirals), we show that the origin of passive spirals may well be
associated with halo gas stripping. Such stripping results mainly from the
hydrodynamical interaction between the halo gas and the hot intracluster gas.
Our numerical simulations demonstrate that even if a spiral orbits a cluster
with a pericenter distance 3 times larger than the cluster core radius,
80 % of the halo gas is stripped within a few Gyr and, accordingly,
cannot be accreted by the spiral. Furthermore, our study demonstrates that this
dramatic decline in the gaseous infall rate leads to a steady increase in the
parameter for the disk, with the spiral arm structure, although persisting,
becoming less pronounced as the star formation rate gradually decreases. These
results suggest that passive spirals formed in this way, gradually evolve into
red cluster S0s.Comment: 13 pages 4 figures (fig.1 = jpg format), accepted by Ap
On the Origin of Lyman Blobs at High Redshift: Submillimetric Evidence for a Hyperwind Galaxy at z=3.1
The most remarkable class of high-redshift objects observed so far is
extended Ly emission-line blobs found in an over-density region at
redshift 3.1. They may be either a dust-enshrouded, extreme starburst galaxy
with a large-scale galactic outflow (superwind) or cooling radiation from dark
matter halos. Recently one of these Ly blobs has been detected at
submillimeter wavelengths (450 and 850 m). Here we show that its
rest-frame spectral energy distribution between optical and far-infrared is
quite similar to that of Arp 220, which is a typical ultraluminous
starburst/superwind galaxy in the local universe. This suggests strongly that
the superwind model proposed by Taniguchi & Shioya is applicable to this
Ly blob. Since the blob is more luminous in the infrared by a factor of
30 than Arp 220, it comprises a new population of hyperwind galaxies at high
redshift.Comment: 4 pages, 1 figure. ApJ (Letters), in pres
Fluctuation Theorem in a Quantum-Dot Aharonov-Bohm Interferometer
In the present study, we investigate the full counting statistics in a
two-terminal Aharonov-Bohm interferometer embedded with an interacting quantum
dot. We introduce a novel saddle-point solution for a cumulant-generating
function, which satisfies the fluctuation theorem and accounts for the
interaction in the mean-field level approximation. Nonlinear transport
coefficients satisfy universal relations imposed by microscopic reversibility,
though the scattering matrix itself is not reversible. The skewness can be
finite even in equilibrium, owing to the interaction and is proportional to the
asymmetric component of nonlinear conductance.Comment: 5 pages, 2 figure
Symmetry in Full Counting Statistics, Fluctuation Theorem, and Relations among Nonlinear Transport Coefficients in the Presence of a Magnetic Field
We study full counting statistics of coherent electron transport through
multi-terminal interacting quantum-dots under a finite magnetic field.
Microscopic reversibility leads to the symmetry of the cumulant generating
function, which generalizes the fluctuation theorem in the context of quantum
transport. Using this symmetry, we derive the Onsager-Casimir relation in the
linear transport regime and universal relations among nonlinear transport
coefficients.Comment: 4.1pages, 1 figur
Synchronization of Excitatory Neurons with Strongly Heterogeneous Phase Responses
In many real-world oscillator systems, the phase response curves are highly
heterogeneous. However, dynamics of heterogeneous oscillator networks has not
been seriously addressed. We propose a theoretical framework to analyze such a
system by dealing explicitly with the heterogeneous phase response curves. We
develop a novel method to solve the self-consistent equations for order
parameters by using formal complex-valued phase variables, and apply our theory
to networks of in vitro cortical neurons. We find a novel state transition that
is not observed in previous oscillator network models.Comment: 4 pages, 3 figure
Symmetry protected Z2-quantization and quaternionic Berry connection with Kramers degeneracy
As for a generic parameter dependent hamiltonian with the time reversal (TR)
invariance, a non Abelian Berry connection with the Kramers (KR) degeneracy are
introduced by using a quaternionic Berry connection. This quaternionic
structure naturally extends to the many body system with the KR degeneracy. Its
topological structure is explicitly discussed in comparison with the one
without the KR degeneracy. Natural dimensions to have non trivial topological
structures are discussed by presenting explicit gauge fixing. Minimum models to
have accidental degeneracies are given with/without the KR degeneracy, which
describe the monopoles of Dirac and Yang. We have shown that the Yang monopole
is literally a quaternionic Dirac monopole. The generic Berry phases
with/without the KR degeneracy are introduced by the complex/quaternionic Berry
connections. As for the symmetry protected quantization of these
general Berry phases, a sufficient condition of the -quantization
is given as the inversion/reflection equivalence. Topological charges of the
SO(3) and SO(5) nonlinear -models are discussed in their relation to
the Chern numbers of the and models as well.Comment: Submitted for New J. Physics, Special issue on Topological
Insulators. 18 pages, 2 figure
Starburst-driven Starbursts in the Heart of Ultraluminous Infrared Galaxies
There is increasing evidence for the presence of blue super star clusters in
the central regions of ultraluminous infrared galaxies like Arp 220.
Ultraluminous galaxies are thought to be triggered by galaxy mergers, and it
has often been argued that these super star clusters may form during violent
collisions between gas clouds in the final phase of the mergers. We now
investigate another set of models which differ from previous ones in that the
formation of the super star clusters is linked directly to the very intense
starburst occurring at the very center of the galaxy. Firstly we show that a
scenario in which the super star clusters form in material compressed by shock
waves originating from the central starburst is implausible because the objects
so produced are much smaller than the observed star clusters in Arp 220. We
then investigate a scenario (based on the Shlosman-Noguchi model) in which the
infalling dense gas disk is unstable gravitationally and collapses to form
massive gaseous clumps. Since these clumps are exposed to the external high
pressure driven by the superwind (a blast wave driven by a collective effect of
a large number of supernovae in the very core of the galaxy), they can collapse
and then massive star formation may be induced in them. The objects produced in
this kind of collapse have properties consistent with those of the observed
super star clusters in the center of Arp 220.Comment: 13 pages, 1 figure, ApJ (Letters) in pres
Numerical study of pi-junction using spin filtering barriers
We numerically investigate the Josephson transport through ferromagnetic
insulators (FIs) by taking into account its band structure. By use of the
recursive Green's function method, we found the formation of the pi junction in
the case of the fully spin-polarized FI (FPFI), e.g., LaBaCuO.
Moreover, the 0-pi transition is induced by increasing the thickness of FPFI.
On the other hand, Josephson current through the Eu chalcogenides shows the pi
junction behavior in the case of the strong d-f hybridization between the
conduction d and the localized f electrons of Eu. Such FI-based Josephson
junctions may become a element in the architecture of future quantum
information devices.Comment: 9 pages, 5 figure
Photometric evolution of dusty starburst mergers:On the nature of ultra-luminous infrared galaxies
By performing N-body simulations of chemodynamical evolution of galaxies with
dusty starbursts, we investigate photometric evolution of gas-rich major
mergers in order to explore the nature of ultraluminous infrared galaxies
(ULIRGs) with the total infrared luminosity ( for
m) of . Main results are the following three.
(1) Global colors and absolute magnitudes the during dusty starburst of a major
merger do not change with time significantly, because interstellar dust heavily
obscures young starburst populations that could cause rapid evolution of
photometric properties of the merger. (2) Dust extinction of stellar
populations in a galaxy merger with large infrared luminosity (
) is selective in the sense that younger stellar
populations are preferentially obscured by dust than old ones. This is because
younger populations are located in the central region where a larger amount of
dusty interstellar gas can be transferred from the outer gas-rich regions of
the merger. (3) Both and the ratio of to band
luminosity ) increases as the star formation rate increase during
the starburst of the present merger model, resulting in the positive
correlation between and .Comment: 32 pages 25 figures,2001,ApJ,in press. For all 25 PS figures
(including fig25.ps), see
http://newt.phys.unsw.edu.au/~bekki/res.dir/paper.dir/apj06.dir/fig.tar.g
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