271,149 research outputs found
The narrow and moving HeII lines in nova KT Eri
We present outburst and quiescence spectra of the classical nova KT Eri and
discuss the appearance of a sharp HeII 4686 Ang emission line, whose origin is
a matter of discussion for those novae that showed a similar component. We
suggest that the sharp HeII line, when it first appeared toward the end of the
outburst optically thick phase, comes from the wrist of the dumbbell structure
characterizing the ejecta as modeled by Ribeiro et al. (2013). When the ejecta
turned optically thin, the already sharp HeII line became two times narrower
and originated from the exposed central binary. During the optically thin
phase, the HeII line displayed a large change in radial velocity that had no
counterpart in the Balmer lines (both their narrow cores and the broad
pedestals). The large variability in radial velocity of the HeII line continued
well into quiescence, and it remains the strongest emission line observed over
the whole optical range.Comment: in press in A&
Seasonal variation of the temporal variance of long-lived trace gases measured during MAP
A series of balloon observations of long lived trace gases was performed in the midlatitude stratosphere during MAP. The temporal variance of the local mixing ratios of CH4, N2O, CFCl3, and CF2Cl2 indicates a substantial annual variability. The concept of the equivalent displacement height (EDH), introduced by Ehhalt et al., is used to investigate some features of transport activity in the lower stratosphere. It appears that most of the temporal variance originates from strong transport effects during the periods of the spring and autumn turn-around of the stratospheric circulation. The dynamical process was found to be considerably reduced during October
Canonical Coherent States for the Relativistic Harmonic Oscillator
In this paper we construct manifestly covariant relativistic coherent states
on the entire complex plane which reproduce others previously introduced on a
given representation, once a change of variables unit disk is performed. We also introduce higher-order, relativistic
creation and annihilation operators, \C,\Cc, with canonical commutation
relation [\C,\Cc]=1 rather than the covariant one [\Z,\Zc]\approx Energy
and naturally associated with the group. The canonical (relativistic)
coherent states are then defined as eigenstates of \C. Finally, we construct
a canonical, minimal representation in configuration space by mean of
eigenstates of a canonical position operator.Comment: 11 LaTeX pages, final version, shortened and corrected, to appear in
J. Math. Phy
Automatic assembly design project 1968/9 :|breport of economic planning committee
Investigations into automatic assembly systems have
been carried out. The conclusions show the major
features to be considered by a company operating
the machine to assemble the contact block with regard
to machine output and financial aspects.
The machine system has been shown to be economically
viable for use under suitable conditions, but the
contact block is considered to be unsuitable for
automatic assembly.
Data for machine specification, reliability and
maintenance has been provided
On coherent systems of type (n,d,n+1) on Petri curves
We study coherent systems of type on a Petri curve of genus
. We describe the geometry of the moduli space of such coherent systems
for large values of the parameter . We determine the top critical value
of and show that the corresponding ``flip'' has positive codimension.
We investigate also the non-emptiness of the moduli space for smaller values of
, proving in many cases that the condition for non-emptiness is the
same as for large . We give some detailed results for and
applications to higher rank Brill-Noether theory and the stability of kernels
of evaluation maps, thus proving Butler's conjecture in some cases in which it
was not previously known.Comment: 33 page
Near-threshold production of , and at a fixed-target experiment at the future ultra-high-energy proton colliders
We outline the opportunities to study the production of the Standard Model
bosons, , and at "low" energies at fixed-target experiments
based at possible future ultra-high-energy proton colliders, \ie\ the
High-Energy LHC, the Super proton-proton Collider and the Future Circular
Collider -- hadron-hadron. These can be indeed made in conjunction with the
proposed future colliders designed to reach up to TeV by using
bent crystals to extract part of the halo of the beam which would then impinge
on a fixed target. Without disturbing the collider operation, this technique
allows for the extraction of a substantial amount of particles in addition to
serve for a beam-cleaning purpose. With this method, high-luminosity
fixed-target studies at centre-of-mass energies above the , and
masses, GeV, are possible. We also discuss the
possibility offered by an internal gas target, which can also be used as
luminosity monitor by studying the beam transverse shape
Fast high--voltage amplifiers for driving electro-optic modulators
We describe five high-voltage (60 to 550V peak to peak), high-speed (1-300ns
rise time; 1.3-300MHz bandwidth) linear amplifiers for driving capacitive or
resistive loads such as electro-optic modulators. The amplifiers use bipolar
transistors in various topologies. Two use electron tubes to overcome the speed
limitations of high-voltage semiconductors. All amplifiers have been built.
Measured performance data is given for each.Comment: 9pages, 6figures, 6tables, to appear in Review of Scientific
Instrument
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