11,441 research outputs found
Macroscopic and mesoscopic matter waves
It has been shown earlier that matter waves which are known to lie typically
in the range of a few Angstrom, can also manifest in the macrodomain with a
wave length of a few centimeters, for electrons propagating along a magnetic
field. This followed from the predictions of a probability amplitude theory by
the author in the classical macrodomain of the dynamics of charged particles in
a magnetic field. It is shown in this paper that this case constitutes only a
special case of a generic situation whereby composite systems such as atoms and
molecules in their highly excited internal states,can exhibit matter wave
manifestation in macro and mesodomains. The wave length of these waves is
determined, not by the mass of the particle as in the case of the de Broglie
wave, but by the frequency, associated with the internal state of excitation,
and is given by a nonquantal expression, , being
the velocity of the particle. For the electrons in a magnetic field the
frequency corresponds to the gyrofrequency, and the nonquantal wave
length is given by ; being
the velocity of electrons along the magnetic field.Comment: 16 pages, LaTex, No figure
UBVRI CCD photometry of the OB associations Bochum 1 and Bochum 6
We report the first deep CCD photometry of 2460 stars in the field of
two poorly studied OB associations Bochum 1 and Bochum 6. We selected 15 and 14
probable members in Bochum 1 and Bochum 6 respectively using photometric
criteria and proper motion data of Tycho 2. Our analysis indicates variable
reddening having mean value of 0.470.10 and 0.710.13 mag
for Bochum 1 and Bochum 6 respectively. Using the zero-age main-sequence
fitting method, we derive a distance of 2.80.4 and 2.50.4 Kpc for
Bochum 1 and Bochum 6 respectively. We obtain an age of 105 Myrs for both
the associations from isochrone fitting. In both associations high and low mass
stars have probably formed together. Within the observational uncertainties,
mass spectrum of the both associations appears to be similar to the Salpeter's
one.Comment: 14 pages, 7 figures, 6 tables. Accepted for Bull. Astr. Soc. Indi
Non-uniform extinction in young open star clusters
The extinction law and the variation of colour excess with position,
luminosity as well as spectral class in young open star clusters NGC 663,
NGC869, NGC 884, NGC 1502, NGC 1893, NGC 2244, NGC 2264, NGC 6611, Tr 14, Tr
15,Tr 16, Coll 228, Tr 37 and Be 86 have been studied. The difference in the
minimum and maximum values of E(B-V) of cluster members has been considered as
a measure of the presence of non-uniform gas and dust inside the clusters. Its
value ranges from 0.22 to 1.03 mag in clusters under study, which indicates
that non-uniform extinction is present in all the clusters. It has been noticed
for the first time in NGC 1502 and Tr 37. It is also found that the
differential colour excess in open clusters, which may be due to the presence
of gas and dust, decreases systematically with the age of clusters indicating
that matter is used either in star formation or blown away by hot stars or
both. There is no uniformity in the variation of E(B-V) with either position or
spectral class or luminosity.Comment: 11 pages, 8 figures, 4 tables; accepted for publication in MNRAS,
typos adde
Particle energization through time-periodic helical magnetic fields
We solve for the motion of charged particles in a helical time-periodic ABC
(Arnold-Beltrami-Childress) magnetic field. The magnetic field lines of a
stationary ABC field with coefficients are chaotic, and we show that
the motion of a charged particle in such a field is also chaotic at late times
with positive Lyapunov exponent. We further show that in time-periodic ABC
fields, the kinetic energy of a charged particle can increase indefinitely with
time. At late times the mean kinetic energy grows as a power law in time with
an exponent that approaches unity. For an initial distribution of particles,
whose kinetic energy is uniformly distributed within some interval, the PDF of
kinetic energy is, at late times, close to a Gaussian but with steeper tails.Comment: uses Revtex 4 instead of Revtex 4-
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