207 research outputs found
Visibility diagrams and experimental stripe structure in the quantum Hall effect
We analyze various properties of the visibility diagrams that can be used in
the context of modular symmetries and confront them to some recent experimental
developments in the Quantum Hall Effect. We show that a suitable physical
interpretation of the visibility diagrams which permits one to describe
successfully the observed architecture of the Quantum Hall states gives rise
naturally to a stripe structure reproducing some of the experimental features
that have been observed in the study of the quantum fluctuations of the Hall
conductance. Furthermore, we exhibit new properties of the visibility diagrams
stemming from the structure of subgroups of the full modular group.Comment: 8 pages in plain TeX, 7 figures in a single postscript fil
The static potential in QED with non-minimal coupling
Here we study the effect of the non-minimal coupling j^{\mu}\eps
\partial^{\nu} A^{\alpha} on the static potential in multiflavor QED.
Both cases of four and two components fermions are studied separately at
leading order in the expansion. Although a non-local Chern-Simons term
appears, in the four components case the photon is still massless leading to a
confining logarithmic potential similar to the classical one. In the two
components case, as expected, the parity breaking fermion mass term generates a
traditional Chern-Simons term which makes the photon massive and we have a
screening potential which vanishes at large inter-charge distance. The extra
non-minimal couplings have no important influence on the static potential at
large inter-charge distances. However, interesting effects show up at finite
distances. In particular, for strong enough non-minimal coupling we may have a
new massive pole in the photon propagator while in the opposite limit there may
be no poles at all in the irreducible case. We also found that, in general, the
non-minimal couplings lead to a finite range {\bf repulsive} force between
charges of opposite signs.Comment: 19 pages and 7 figure
3D MHD Modeling of the Gaseous Structure of the Galaxy: Synthetic Observations
We generated synthetic observations from the four-arm model presented in
Gomez & Cox (2004) for the Galactic ISM in the presence of a spiral
gravitational perturbation. We found that velocity crowding and diffusion have
a strong effect in the l-v diagram. The v-b diagram presents structures at the
expected spiral arm velocities, that can be explained by the off-the-plane
structure of the arms presented in previous papers of this series. Such
structures are observed in the Leiden/Dwingeloo HI survey. The rotation curve,
as measured from the inside of the modeled galaxy, shows similarities with the
observed one for the Milky Way Galaxy, although it has large deviations from
the smooth circular rotation corresponding to the background potential. The
magnetic field inferred from a synthetic synchrotron map shows a largely
circular structure, but with interesting deviations in the midplane due to
distortion of the field from circularity in the interarm regions.Comment: Accepted for publication in ApJ. Better quality figures in
http://www.astro.umd.edu/~gomez/publica/3d_galaxy-3.pd
The Aesthetics of Paradoxism (Second Edition)
In the history of thought and creation, the decisive events, the great and significant moments, the strongly affirmative stages - then the imposition of the optimizing novelties - have depended on the name and prestige of a personality. Referring to those, we personalize further on. The examples are extremely numerous, even in our nearest past. When we mention a creation - in the largest sense of the term - with the name of the personality who illustrates it most extensively at a given time, we state precisely the specific importance of it; we give it, with other words, the identity to which we can refer continuously with full knowledge and without causing any confusion among the receivers. The facts are called with the name of the man who produced them, and in this way we can compose a parallel onomastic dictionary, in which the work is included in the person’s space, keeping its content. The consecrated proper names evolve through quickly imposed habits, a large range of increments that announce the essential outline of their peak production. No space for ambiguity remains when we address to readers or listeners who are somewhat acquainted with the subject and we use such terms as Aristotelianism, Platonism, Kantianism, Hegelianism, Proustianism, Eminescianism, Barbianism, etc. We have even the advantage of a centered communication when we suggest with a sole notion the work as well as its dominant features, linked with the renown of the concerned author. There is no doubt that this way of denomination, when practiced a long time, has become a reflex and now is part of the habits of a correct expression. And neither the semantic objectification of works by a person nor the inherent axiological sanction disturb anybody. Personification being inevitable in creation, the history of art can be superposed to the history of the authors or, at, least gets tangled very strongly with them. It is precisely the case with the recent literary movement of Paradoxism, conceived in Romania and affirmed in the United States, which is closely bound to the temperament, inclination, taste and creative disposition of its initiator and organizer, the poet-mathematician Florentin Smarandache (paradoxism = smarandachism, in an “internal” and already notorious interpretation)
Duality and Non-linear Response for Quantum Hall Systems
We derive the implications of particle-vortex duality for the electromagnetic
response of Quantum Hall systems beyond the linear-response regime. This
provides a first theoretical explanation of the remarkable duality which has
been observed in the nonlinear regime for the electromagnetic response of
Quantum Hall systems.Comment: 7 pages, 1 figure, typeset in LaTe
First Detection of the Zeeman Effect in the 36 GHz Class I methanol maser line with the EVLA
We report the first detection of the Zeeman effect in the 36 GHz Class I
methanol maser line. The observations were carried out with 13 antennas of the
EVLA toward the high mass star forming region M8E. Based on our adopted Zeeman
splitting factor of $z = 1.7 Hz/mG, we detect a line of sight magnetic field of
-31.3 +/- 3.5 mG and 20.2 +/- 3.5 mG to the northwest and southeast of the
maser line peak respectively. This change in sign over a 1300 AU size scale may
indicate that the masers are tracing two regions with different fields, or that
the same field curves across the regions where the masers are being excited.
The detected fields are not significantly different from the magnetic fields
detected in the 6.7 GHz Class II methanol maser line, indicating that methanol
masers may trace the large scale magnetic field, or that the magnetic field
remains unchanged during the early evolution of star forming regions. Given
what is known about the densities at which 36 GHz methanol masers are excited,
we find that the magnetic field is dynamically significant in the star forming
region.Comment: 10 pages, accepted by ApJ Letter
Errors in kinematic distances and our image of the Milky Way Galaxy
Errors in the kinematic distances, under the assumption of circular gas
orbits, were estimated by performing synthetic observations of a model disk
galaxy. It was found that the error is < 0.5 kpc for most of the disk when the
measured rotation curve was used, but larger if the real rotation curve is
applied. In both cases, the error is significantly larger at the positions of
the spiral arms. The error structure is such that, when kinematic distances are
used to develope a picture of the large scale density distribution, the most
significant features of the numerical model are significantly distorted or
absent, while spurious structure appears. By considering the full velocity
field in the calculation of the kinematic distances, most of the original
density structures can be recovered.Comment: Accepted for publication in A
A Study of Cyg OB2: Pointing the Way Towards Finding Our Galaxy's Super Star Clusters
New optical MK classification spectra have been obtained for 14 OB star
candidates identified by Comeron et al. (2002) and presumed to be possible
members of the Cyg OB2 cluster. All 14 candidate OB stars observed are indeed
early-type stars, strongly suggesting the remaining 31 candidates identified by
Comeron et al. are also early-type stars. However, as many as half of the new
stars appear to be significantly older than the previously studied optical
cluster, making their membership in Cyg OB2 suspect. Despite this, the
recognition of Cyg OB2 being a more massive and extensive star cluster than
previously realized, along with the recently recognized candidate super star
cluster Westerlund 1 only a few kpc away (Clark & Negueruela 2002), reminds us
that we are woefully under-informed about the massive cluster population in our
Galaxy. Extrapolations of the locally derived cluster luminosity function
indicate 10s to perhaps 100 of these very massive open clusters (Mcl ~ 10^4
M_sun, Mv ~ -11) should exist within our galaxy. Radio surveys will not detect
these massive clusters if they are more than a few million years old. Our best
hope for remedying this shortfall is through deep infrared searches and follow
up near-infrared spectroscopic observations, as was used by Comeron et al. to
locate candidate members of the Cyg OB2 association.Comment: 30 pages, 12 figures, ApJ in pres
An experimental study on (2) modular symmetry in the quantum Hall system with a small spin-splitting
Magnetic-field-induced phase transitions were studied with a two-dimensional
electron AlGaAs/GaAs system. The temperature-driven flow diagram shows the
features of the (2) modular symmetry, which includes distorted
flowlines and shiftted critical point. The deviation of the critical
conductivities is attributed to a small but resolved spin splitting, which
reduces the symmetry in Landau quantization. [B. P. Dolan, Phys. Rev. B 62,
10278.] Universal scaling is found under the reduction of the modular symmetry.
It is also shown that the Hall conductivity could still be governed by the
scaling law when the semicircle law and the scaling on the longitudinal
conductivity are invalid. *corresponding author:[email protected]: The revised manuscript has been published in J. Phys.: Condens.
Matte
The Stellar Content of Obscured Galactic Giant H II Regions III.: W31
We present near infrared (J, H, and K) photometry and moderate resolution
(lambda/Deltalambda = 3000) K-band spectroscopy of the embedded stellar cluster
in the giant H II region W31. Four of the brightest five cluster members are
early O--type stars based on their spectra. We derive a spectro--photometric
distance for W31 of 3.4 +/- 0.3 kpc using these new spectral types and infrared
photometry. The brightest cluster source at K is a red object which lies in the
region of the J - H vs. H - K color--color plot inhabited by stars with excess
emission in the K-band. This point source has an H plus K-band spectrum which
shows no photospheric features, which we interpret as being the result of
veiling by local dust emission. Strong Brackett series emission and permitted
FeII emission are detected in this source; the latter feature is suggestive of
a dense inflow or outflow. The near infrared position of this red source is
consistent with the position of a 5 GHz thermal radio source seen in previous
high angular resolution VLA images. We also identify several other K-band
sources containing excess emission with compact radio sources. These objects
may represent stars in the W31 cluster still embedded in their birth cocoons.Comment: LaTeX2e/aastex, 29 pages including 9 figures, 3 table
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