107 research outputs found
Observation of Resonant Diffusive Radiation in Random Multilayered Systems
Diffusive Radiation is a new type of radiation predicted to occur in randomly
inhomogeneous media due to the multiple scattering of pseudophotons. This
theoretical effect is now observed experimentally. The radiation is generated
by the passage of electrons of energy 200KeV-2.2MeV through a random stack of
films in the visible light region. The radiation intensity increases resonantly
provided the Cherenkov condition is satisfied for the average dielectric
constant of the medium. The observed angular dependence and electron resonance
energy are in agreement with the theoretical predictions. These observations
open a road to application of diffusive radiation in particle detection,
astrophysics, soft X-ray generation and etc.. `Comment: 4pages, 4figure
A Carleman type theorem for proper holomorphic embeddings
In 1927, Carleman showed that a continuous, complex-valued function on the
real line can be approximated in the Whitney topology by an entire function
restricted to the real line. In this paper, we prove a similar result for
proper holomorphic embeddings. Namely, we show that a proper \cC^r embedding
of the real line into \C^n can be approximated in the strong \cC^r topology
by a proper holomorphic embedding of \C into \C^n
Baryon Junction Loops in HIJING/B\=Bv2.0 and the Baryon/Meson Anomaly at RHIC
A new version, v2.0, of the HIJING/B\=B Monte Carlo nuclear collision event
generator is introduced in order to explore further the possible role of baryon
junctions loops in the baryon/meson anomaly (2 5 GeV/c) observed in
200A GeV Au+Au reactions at RHIC. We show that junction loops with an enhanced
intrinsic GeV/c transverse momentum kick may provide a partial
explanation of the anomaly as well as other important baryon stopping
observables.Comment: 27 pages, Latex(revtex), 8 figure
Merging Galaxies in the SDSS EDR
We present a new catalog of merging galaxies obtained through an automated
systematic search routine. The 1479 new pairs of merging galaxies were found in
approximately 462 sq deg of the Sloan Digital Sky Survey Early Data Release
(SDSS EDR; Stoughton et al. 2002) photometric data, and the pair catalog is
complete for galaxies in the magnitude range 16.0 <= g* <= 20.
The selection algorithm, implementing a variation on the original
Karachentsev (1972) criteria, proved to be very efficient and fast. Merging
galaxies were selected such that the inter-galaxy separations were less than
the sum of the component galaxies' radii.
We discuss the characteristics of the sample in terms of completeness, pair
separation, and the Holmberg effect. We also present an online atlas of images
for the SDSS EDR pairs obtained using the corrected frames from the SDSS EDR
database. The atlas images also include the relevant data for each pair member.
This catalog will be useful for conducting studies of the general
characteristics of merging galaxies, their environments, and their component
galaxies. The redshifts for a subset of the interacting and merging galaxies
and the distribution of angular sizes for these systems indicate the SDSS
provides a much deeper sample than almost any other wide-area catalog to date.Comment: 58 pages, which includes 15 figures and 6 tables. Figures 2, 8, 9,
10, 11, 13, and 14 are provided as JPEG files. For online atlas, see
http://home.fnal.gov/~sallam/MergePair/ . Accepted for publication in A
Preliminary survey of backdrivable linear actuators for humanoid robots
This paper presents a preliminary survey of the use of direct drive linear motors for joint actuation of a humanoid robot. Their prime asset relies on backdrivability, a significant feature to properly cushion high impacts between feet and ground during dynamic walking or running. Our long-term goal is the design of high performance human size bipedal walking robots. However, this paper focuses on a preliminary feasibility study: the design and experimentation of a mono-actuator lower limb
The Conformal Anomaly of M5-Branes
We show that the conformal anomaly for N M5-branes grows like . The
method we employ relates Coulomb branch interactions in six dimensions to
interactions in four dimensions using supersymmetry. This leads to a relation
between the six-dimensional conformal anomaly and the conformal anomaly of N=4
Yang-Mills. Along the way, we determine the structure of the four derivative
interactions for the toroidally compactified (2,0) theory, while encountering
interesting novelties in the structure of the six derivative interactions.Comment: 38 pages, LaTeX; references adde
Strongly localized polaritons in an array of trapped two-level atoms interacting with a light field
We propose a new type of spatially periodic structure, i.e. polaritonic
crystal (PolC), to observe a "slow"/"stopped" light phenomenon due to coupled
atom-field states (polaritons) in a lattice. Under the tightbinding
approximation, such a system realizes an array of weakly coupled trapped
two-component atomic ensembles interacting with optical field in a
tunnel-coupled one dimensional cavity array. We have shown that the phase
transition to the superfluid Bardeen-Cooper-Schrieffer state, a so-called
(BCS)-type state of low branch polaritons, occurs under the strong coupling
condition. Such a transition results in the appearance of a macroscopic
polarization of the atomic medium at non-zero frequency. The principal result
is that the group velocity of polaritons depends essentially on the order
parameter of the system, i.e. on the average photon number in the cavity array.Comment: 16 pages, 6 figure
Optical Identification of the ASCA Medium Sensitivity Survey in the Northern Sky: Nature of Hard X-ray-selected Luminous Active Galactic Nuclei
We present the results of optical spectroscopic identifications of a bright
subsample of 2-10keV hard X-ray selected sources from the ASCA Medium
Sensitivity Survey in the northern sky. The flux limit of the subsample is
3*10^-13 erg s^-1 cm^-2 in the 2-10keV band. All but one of the 87 hard X-ray
selected sources are optically identified, with AGNs, 7 clusters of galaxies,
and 1 galactic star. It is the largest complete sample of hard X-ray selected
AGNs at the bright flux limit. Amounts of absorption to their nuclei are
estimated to be hydrogen column densities (N_H) of up to ~3*10^23 cm^-2 from
their X-ray spectra. Optical properties of X-ray absorbed AGNs with N_H >
1*10^22 cm^-2 indicate the effects of dust absorption: at redshifts, z<0.6,
AGNs without broad H\beta emission lines have significantly larger N_H value
than AGNs with broad H\beta emission lines. At z>0.6, the X-ray absorbed AGNs
have a large hard X-ray to optical flux ratio (log f2-10keV/fR > +1). However,
three X-ray absorbed z>0.6 AGNs show strong broad lines. In combination with
hard X-ray selected AGN samples from the ASCA Large Sky Survey, the ASCA Deep
Survey in the Lockman Hole and Chandra Deep Field North, the luminosity
distributions of absorbed and less-absorbed AGNs are compared.Comment: 56 pages with 14 figures. Accepted to ApJS. Fig.1 and tables are
available from http://www.subaru.naoj.org/staff/akiyama/papers/papers.htm
- …