16,901 research outputs found
New Fe II energy levels from stellar spectra
The spectra of B-type and early A-type stars show numerous unidentified lines
in the whole optical range, especially in the 5100 - 5400 A interval. Because
Fe II transitions to high energy levels should be observed in this region, we
used semiempirical predicted wavelengths and gf-values of Fe II to identify
unknown lines. Semiempirical line data for Fe II computed by Kurucz are used to
synthesize the spectrum of the slow-rotating, Fe-overabundant CP star HR 6000.
We determined a total of 109 new 4f levels for Fe II with energies ranging from
122324 cm^-1 to 128110 cm^-1. They belong to the Fe II subconfigurations
3d^6(^3P)4f (10 levels), 3d^6(^3H)4f (36 levels), 3d^6(^3F)4f (37 levels), and
3d^6(^3G)4f (26 levels). We also found 14 even levels from 4d (3 levels), 5d (7
levels), and 6d (4 levels) configurations. The new levels have allowed us to
identify more than 50% of the previously unidentified lines of HR 6000 in the
wavelength region 3800-8000 A. Tables listing the new energy levels are given
in the paper; tables listing the spectral lines with loggf>/=-1.5 that are
transitions to the 4f energy levels are given in the Online Material. These new
levels produce 18000 lines throughout the spectrum from the ultraviolet to the
infrared.Comment: Paper accepted by A&A for publicatio
The Theory Behind TheoryMine
Abstract. We describe the technology behind the TheoryMine novelty gift company, which sells the rights to name novel mathematical theorems. A tower of four computer systems is used to generate recursive theories, then to speculate conjectures in those theories and then to prove these conjectures. All stages of the process are entirely automatic. The process guarantees large numbers of sound, novel theorems of some intrinsic merit.
Optical Versus Mid-Infrared Spectroscopic Classification of Ultraluminous Infrared Galaxies
The origin of huge infrared luminosities of ultraluminous infrared galaxies
(ULIGs) is still in question. Recently, Genzel et al. made mid-infrared (MIR)
spectroscopy of a large number of ULIGs and found that the major energy source
in them is massive stars formed in the recent starburst activity; i.e.,
70% -- 80% of the sample are predominantly powered by the starburst. However,
it is known that previous optical spectroscopic observations showed that the
majority of ULIGs are classified as Seyferts or LINERs (low-ionization nuclear
emission-line regions). In order to reconcile this difference, we compare types
of emission-line activity for a sample of ULIGs which have been observed in
both optical and MIR. We confirm the results of previous studies that the
majority of ULIGs classified as LINERs based on the optical emission-line
diagnostics turn to be starburst-dominated galaxies based on the MIR ones.
Since the MIR spectroscopy can probe more heavily-reddened, inner parts of the
ULIGs, it is quite unlikely that the inner parts are powered by the starburst
while the outer parts are powered by non-stellar ionization sources. The most
probable resolution of this dilemma is that the optical emission-line nebulae
with the LINER properties are powered predominantly by shock heating driven by
the superwind activity; i.e., a blast wave driven by a collective effect of a
large number of supernovae in the central region of galaxy mergers.Comment: 15 pages, 2 tables, and 3 eps figures. The Astrophysical Journal
(Part 1), in pres
Models for energy and charge transport and storage in biomolecules
Two models for energy and charge transport and storage in biomolecules are
considered. A model based on the discrete nonlinear Schrodinger equation with
long-range dispersive interactions (LRI's) between base pairs of DNA is offered
for the description of nonlinear dynamics of the DNA molecule. We show that
LRI's are responsible for the existence of an interval of bistability where two
stable stationary states, a narrow, pinned state and a broad, mobile state,
coexist at each value of the total energy. The possibility of controlled
switching between pinned and mobile states is demonstrated. The mechanism could
be important for controlling energy storage and transport in DNA molecules.
Another model is offered for the description of nonlinear excitations in
proteins and other anharmonic biomolecules. We show that in the highly
anharmonic systems a bound state of Davydov and Boussinesq solitons can exist.Comment: 12 pages (latex), 12 figures (ps
Photoassisted sequential resonant tunneling through superlattices
We have analyzed theoretically the photoassisted tunneling current through a
superlattice in the presence of an AC potential. For that purpose we have
developed a new model to calculate the sequential resonant currrent trhough a
superlattice based in the TRansfer Hamiltonian Method. The tunneling current
presents new features due to new effective tunneling chanels coming from the
photoside bands induced by the AC field. Our theoretical results are in good
agreement with the available experimental evidence.Comment: Revtex 3.0 4 pages, 4 figures uuencoded compressed tar-fil
High Excitation Molecular Gas in the Magellanic Clouds
We present the first survey of submillimeter CO 4-3 emission in the
Magellanic Clouds. The survey is comprised of 15 6'x6' maps obtained using the
AST/RO telescope toward the molecular peaks of the Large and Small Magellanic
Clouds. We have used these data to constrain the physical conditions in these
objects, in particular their molecular gas density and temperature. We find
that there are significant amounts of molecular gas associated with most of
these molecular peaks, and that high molecular gas temperatures are pervasive
throughout our sample. We discuss whether this may be due to the low
metallicities and the associated dearth of gas coolants in the Clouds, and
conclude that the present sample is insufficient to assert this effect.Comment: 18 pages, 3 figures, 5 tables. To appear in Ap
Superconductivity-Related Insulating Behavior
We present the results of an experimental study of superconducting,
disordered, thin-films of amorphous Indium Oxide. These films can be driven
from the superconducting phase to a reentrant insulating state by the
application of a perpendicular magnetic field (). We find that the high-
insulator exhibits activated transport with a characteristic temperature,
. has a maximum value () that is close to the
superconducting transition temperature () at = 0, suggesting a
possible relation between the conduction mechanisms in the superconducting and
insulating phases. and display opposite dependences on the
disorder strength.Comment: Tex file and 5 figures; Revised version; To appear in Phys. Rev.
Lett. (2004
Controllable coherent population transfers in superconducting qubits for quantum computing
We propose an approach to coherently transfer populations between selected
quantum states in one- and two-qubit systems by using controllable
Stark-chirped rapid adiabatic passages (SCRAPs). These {\it evolution-time
insensitive} transfers, assisted by easily implementable single-qubit
phase-shift operations, could serve as elementary logic gates for quantum
computing. Specifically, this proposal could be conveniently demonstrated with
existing Josephson phase qubits. Our proposal can find an immediate application
in the readout of these qubits. Indeed, the broken parity symmetries of the
bound states in these artificial "atoms" provide an efficient approach to
design the required adiabatic pulses.Comment: 4 pages, 6 figures. to appear in Physical Review Letter
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