5,934 research outputs found
A Neutrino-Factory Muon Storage Ring to Provide Beams for Multiple Detectors Around the World
We briefly discuss the physics motivation for a neutrino factory with varying
baseline distances of about 1000 to 9000 km. We describe the amount of non
planarity of the storage ring required to service three or four detectors at
once. A novel bowtie storage ring is described that could in part provide these
beams; a preliminary lattice design is given. We give the space angles between
the various detector locations and possible sites for neutrino factories.
Finally we describe detectors at the Gran Sasso Laboratory and at a new
laboratory near Carlsbad, NM to observe the neutrino interactions with wrong
sign leptons.Comment: 8 pages. Presented at the 5th Int. Conf. sponsored by UCLA on the
Physics Potential and Develoment of mu^+mu^- Colliders (San Francisco,
December 15-17, 1999) and to be published in the Proceedings by AI
An edge index for the Quantum Spin-Hall effect
Quantum Spin-Hall systems are topological insulators displaying
dissipationless spin currents flowing at the edges of the samples. In
contradistinction to the Quantum Hall systems where the charge conductance of
the edge modes is quantized, the spin conductance is not and it remained an
open problem to find the observable whose edge current is quantized. In this
paper, we define a particular observable and the edge current corresponding to
this observable. We show that this current is quantized and that the
quantization is given by the index of a certain Fredholm operator. This
provides a new topological invariant that is shown to take same values as the
Spin-Chern number previously introduced in the literature. The result gives an
effective tool for the investigation of the edge channels' structure in Quantum
Spin-Hall systems. Based on a reasonable assumption, we also show that the edge
conducting channels are not destroyed by a random edge.Comment: 4 pages, 3 figure
Spectral flow in the supersymmetric - model with a interaction
The spectral flow in the supersymmetric {\it t-J} model with
interaction is studied by analyzing the exact spectrum with twisted boundary
conditions. The spectral flows for the charge and spin sectors are shown to
nicely fit in with the motif picture in the asymptotic Bethe ansatz. Although
fractional exclusion statistics for the spin sector clearly shows up in the
period of the spectral flow at half filling, such a property is generally
hidden once any number of holes are doped, because the commensurability
condition in the motif is not met in the metallic phase.Comment: 8 pages, revtex, Phys. Rev. B54 (1996) August 15, in pres
Observation of zigzag and armchair edges of graphite using scanning tunneling microscopy and spectroscopy
The presence of structure-dependent edge states of graphite is revealed by
both ambient- and ultra-highvacuum- (UHV) scanning tunneling microscopy (STM) /
scanning tunneling spectroscopy (STS) observations. On a hydrogenated zigzag
(armchair) edge, bright spots are (are not) observed together with (SQRT(3) by
SQRT(3))R30 superlattice near the Fermi level (V_S = −30 mV for a peak of
the local density of states (LDOS)) under UHV, demonstrating that a zigzag edge
is responsible for the edge states, although there is no appreciable difference
between as-prepared zigzag and armchair edges in air. Even in hydrogenated
armchair edge, however, bright spots are observed at defect points, at which
partial zigzag edges are created in the armchair edge.Comment: 4 pages, 4 figures, contents for experimental/theoretical reseachers,
accepted as an issue of Physical Review B (PRB
The Second Survey of the Molecular Clouds in the Large Magellanic Cloud by NANTEN. II. Star Formation
We studied star formation activities in the molecular clouds in the Large
Magellanic Cloud. We have utilized the second catalog of 272 molecular clouds
obtained by NANTEN to compare the cloud distribution with signatures of massive
star formation including stellar clusters, and optical and radio HII regions.
We find that the molecular clouds are classified into three types according to
the activities of massive star formation; Type I shows no signature of massive
star formation, Type II is associated with relatively small HII region(s) and
Type III with both HII region(s) and young stellar cluster(s). The radio
continuum sources were used to confirm that Type I GMCs do not host optically
hidden HII regions. These signatures of massive star formation show a good
spatial correlation with the molecular clouds in a sense they are located
within ~100 pc of the molecular clouds. Among possible ideas to explain the GMC
Types, we favor that the Types indicate an evolutionary sequence; i.e., the
youngest phase is Type I, followed by Type II and the last phase is Type III,
where the most active star formation takes place leading to cloud dispersal.
The number of the three types of GMCs should be proportional to the time scale
of each evolutionary stage if a steady state of massive star and cluster
formation is a good approximation. By adopting the time scale of the youngest
stellar clusters, 10 Myrs, we roughly estimate the timescales of Types I, II
and III to be 6 Myrs, 13 Myrs and 7 Myrs, respectively, corresponding to a
lifetime of 20-30 Myrs for the GMCs with a mass above the completeness limit, 5
x 10^4 Msun.Comment: accepted to the Astrophysical Journal Supplement Series. 20 figures
and 4 tables. Higher resolution color PDF is found at
http://www.a.phys.nagoya-u.ac.jp/~kawamura/research/NANTEN_LMC_2_preprint.pdf
(47 pages,32MB
Adiabatic Ground-State Properties of Spin Chains with Twisted Boundary Conditions
We study the Heisenberg spin chain with twisted boundary conditions, focusing
on the adiabatic flow of the energy spectrum as a function of the twist angle.
In terms of effective field theory for the nearest-neighbor model, we show that
the period 2 (in unit ) obtained by Sutherland and Shastry arises from
irrelevant perturbations around the massless fixed point, and that this period
may be rather general for one-dimensional interacting lattice models at half
filling. In contrast, the period for the Haldane-Shastry spin model with
interaction has a different and unique origin for the period, namely,
it reflects fractional statistics in Haldane's sense.Comment: 6 pages, revtex, 3 figures available on request, to appear in J.
Phys. Soc. Jp
Kojima-1Lb Is a Mildly Cold Neptune around the Brightest Microlensing Host Star
We report the analysis of additional multiband photometry and spectroscopy and new adaptive optics (AO) imaging of the nearby planetary microlensing event TCP J05074264+2447555 (Kojima-1), which was discovered toward the Galactic anticenter in 2017 (Nucita et al.). We confirm the planetary nature of the light-curve anomaly around the peak while finding no additional planetary feature in this event. We also confirm the presence of apparent blending flux and the absence of significant parallax signal reported in the literature. The AO image reveals no contaminating sources, making it most likely that the blending flux comes from the lens star. The measured multiband lens flux, combined with a constraint from the microlensing model, allows us to narrow down the previously unresolved mass and distance of the lens system. We find that the primary lens is a dwarf on the K/M boundary (0.581 ± 0.033 M⊙) located at 505 ± 47 pc, and the companion (Kojima-1Lb) is a Neptune-mass planet (20.0 ± 2.0 M⊕) with a semimajor axis of 1.08^(+0.62)_(-0.18) au. This orbit is a few times smaller than those of typical microlensing planets and is comparable to the snow-line location at young ages. We calculate that the a priori detection probability of Kojima-1Lb is only ~35%, which may imply that Neptunes are common around the snow line, as recently suggested by the transit and radial velocity techniques. The host star is the brightest among the microlensing planetary systems (K_s = 13.7), offering a great opportunity to spectroscopically characterize this system, even with current facilities
Dynamics of a Generalized Cosmological Scalar-Tensor Theory
A generalized scalar-tensor theory is investigated whose cosmological term
depends on both a scalar field and its time derivative. A correspondence with
solutions of five-dimensional Space-Time-Matter theory is noted. Analytic
solutions are found for the scale factor, scalar field and cosmological term.
Models with free parameters of order unity are consistent with recent
observational data and could be relevant to both the dark-matter and
cosmological-"constant" problems.Comment: 13 page
Statistical mechanics of non-hamiltonian systems: Traffic flow
Statistical mechanics of a small system of cars on a single-lane road is
developed. The system is not characterized by a Hamiltonian but by a
conditional probability of a velocity of a car for the given velocity and
distance of the car ahead. Distribution of car velocities for various densities
of a group of cars are derived as well as probabilities of density fluctuations
of the group for different velocities. For high braking abilities of cars
free-flow and congested phases are found. Platoons of cars are formed for
system of cars with inefficient brakes. A first order phase transition between
free-flow and congested phase is suggested.Comment: 12 pages, 6 figures, presented at TGF, Paris, 200
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