5,461 research outputs found
Vortices in atomic-molecular Bose-Einstein condensates
The structure and stability of vortices in hybrid atomic-molecular
Bose-Einstein condensates is analyzed in the framework of a two-component
Gross-Pitaevskii-type model that describes the stimulated Raman-induced
photoassociation process. New types of topological vortex states are predicted
to exist in the coherently coupled two-component condensates even without a
trap, and their nontrivial dynamics in the presence of losses is demonstrated.Comment: 7 pages, 6 figure
Characterizing the transition from diffuse atomic to dense molecular clouds in the Magellanic clouds with [CII], [CI], and CO
We present and analyze deep Herschel/HIFI observations of the [CII] 158um,
[CI] 609um, and [CI] 370um lines towards 54 lines-of-sight (LOS) in the Large
and Small Magellanic clouds. These observations are used to determine the
physical conditions of the line--emitting gas, which we use to study the
transition from atomic to molecular gas and from C^+ to C^0 to CO in their low
metallicity environments. We trace gas with molecular fractions in the range
0.1<f(H2)<1, between those in the diffuse H2 gas detected by UV absorption
(f(H2)<0.2) and well shielded regions in which hydrogen is essentially
completely molecular. The C^0 and CO column densities are only measurable in
regions with molecular fractions f(H2)>0.45 in both the LMC and SMC. Ionized
carbon is the dominant gas-phase form of this element that is associated with
molecular gas, with C^0 and CO representing a small fraction, implying that
most (89% in the LMC and 77% in the SMC) of the molecular gas in our sample is
CO-dark H2. The mean X_CO conversion factors in our LMC and SMC sample are
larger than the value typically found in the Milky Way. When applying a
correction based on the filling factor of the CO emission, we find that the
values of X_CO in the LMC and SMC are closer to that in the Milky Way. The
observed [CII] intensity in our sample represents about 1% of the total
far-infrared intensity from the LOSs observed in both Magellanic Clouds.Comment: 32 pages, 21 figures, Accepted to Ap
Vortices and domain walls in a Chern-Simons theory with magnetic moment interaction
We study the structure and properties of vortices in a recently proposed
Abelian Maxwell-Chern-Simons model in dimensions. The model which is
described by gauge field interacting with a complex scalar field, includes two
parity and time violating terms: the Chern-Simons and the anomalous magnetic
terms. Self-dual relativistic vortices are discussed in detail. We also find
one dimensional soliton solutions of the domain wall type. The vortices are
correctly described by the domain wall solutions in the large flux limit.Comment: To be published in Phys RevD 23 pages, RevTex, 5 figure
Bogomol'nyi equations for solitons in Maxwell-Chern-Simons gauge theories with the magnetic moment interaction term
Without assuming rotational invariance, we derive Bogomol'nyi equations for
the solitons in the abelian Chern-Simons gauge theories with the anomalous
magnetic moment interaction. We also evaluate the number of zero modes around a
static soliton configuration.Comment: 9 pages, Revtex, SNUTP-94/6
Forecasting COVID-19 Cases in the Philippines Using Various Mathematical Models
Due to the rapid increase of COVID-19 infection cases in many countries such as the Philippines, efforts in forecasting daily infections have been made to better manage the pandemic and respond effectively. In this study, we considered the cumulative COVID-19 infection cases in the Philippines from 6 March 2020 to 31 July 2020, and forecasted the cases from 1–15 August 2020 using various mathematical models—weighted moving average, exponential smoothing, Susceptible-Exposed-Infected-Recovered (SEIR) model, Ornstein-Uhlenbeck process, Autoregressive Integrated Moving Average (ARIMA) model, and random forest. We compared the results to the actual data using traditional error metrics. Our results showed that the ARIMA (1,2,1) model had the closest forecast values to the actual data. Policymakers can use this result in determining which forecast method to use for their community to have data-based information for the preparation of their personnel and facilities.
Keywords: forecasting · epidemics · moving average · exponential smoothing · ARIMA · Ornstein-Uhlenbeck · SEIR · random fores
Studies of Quasi Periodic Oscillations in the Black Hole Transient XTE J 1817-330
We have used archival RXTE PCA data to investigate timing and spectral
characteristics of the transient XTE J1817-330. The data pertains to 160 PCA
pointed observations made during the outburst period 2006, January 27 to August
2. A detailed analysis of Quasi-Periodic Oscillations (QPOs) in this black hole
X-ray binary is carried out. Power density spectra were obtained using the
light curves of the source. QPOs have been detected in the 2-8 keV band in 10
of the observations. In 8 of these observations, QPOs are present in the 8-14
keV and in 5 observations in the 15-25 keV band. XTE J1817-330 is the third
black hole source from which the low frequency QPOs are clearly detected in
hard X-rays. The QPO frequency lies in ~ 4-9 Hz and the rms amplitude in
1.7-13.3% range, the amplitude being higher at higher energies. We have fitted
the PDS of the observations with Lorentzian and power law models. Energy
spectra are derived for those observations in which the QPOs are detected to
investigate any dependence of the QPO characteristic on the spectral
parameters. These spectra are well fitted with a two component model that
includes the disk black body component and a power law component. The QPO
characteristics and their variations are discussed and its implication on the
origin of the QPOs are examinedComment: 16 page, 9 figures and 2 tables. Accepted in MNRAS Journa
Bogomol'nyi Equations of Maxwell-Chern-Simons vortices from a generalized Abelian Higgs Model
We consider a generalization of the abelian Higgs model with a Chern-Simons
term by modifying two terms of the usual Lagrangian. We multiply a dielectric
function with the Maxwell kinetic energy term and incorporate nonminimal
interaction by considering generalized covariant derivative. We show that for a
particular choice of the dielectric function this model admits both topological
as well as nontopological charged vortices satisfying Bogomol'nyi bound for
which the magnetic flux, charge and angular momentum are not quantized. However
the energy for the topolgical vortices is quantized and in each sector these
topological vortex solutions are infinitely degenerate. In the nonrelativistic
limit, this model admits static self-dual soliton solutions with nonzero finite
energy configuration. For the whole class of dielectric function for which the
nontopological vortices exists in the relativistic theory, the charge density
satisfies the same Liouville equation in the nonrelativistic limit.Comment: 30 pages(4 figures not included), RevTeX, IP/BBSR/93-6
Radio Interferometric Planet Search II: Constraints on sub-Jupiter-Mass Companions to GJ 896A
We present results from the Radio Interferometric Planet (RIPL) search for
compan- ions to the nearby star GJ 896A. We present 11 observations over 4.9
years. Fitting astrometric parameters to the data reveals a residual with
peak-to-peak amplitude of ~ 3 mas in right ascension. This residual is well-fit
by an acceleration term of 0.458 \pm 0.032 mas/y^2. The parallax is fit to an
accuracy of 0.2 mas and the proper motion terms are fit to accuracies of 0.01
mas/y. After fitting astrometric and acceleration terms residuals are 0.26 mas
in each coordinate, demonstrating that stellar jitter does not limit the
ability to carry out radio astrometric planet detection and characterization.
The acceleration term originates in part from the companion GJ 896B but the
amplitude of the acceleration in declination is not accurately predicted by the
orbital model. The acceleration sets a mass upper limit of 0.15 MJ at a
semi-major axis of 2 AU for a planetary companion to GJ 896A. For semi-major
axes between 0.3 and 2 AU upper limits are determined by the maximum angular
separation; the upper limits scale from the minimum value in proportion to the
inverse of the radius. Upper limits at larger radii are set by the acceleration
and scale as the radius squared. An improved solution for the stellar binary
system could improve the exoplanet mass sensitivity by an order of magnitude.Comment: Accepted for publication in Ap
Kepler-424 b: A "lonely" hot Jupiter that found a companion
Peer reviewedFinal Accepted Versio
Magnetic operations: a little fuzzy physics?
We examine the behaviour of charged particles in homogeneous, constant and/or
oscillating magnetic fields in the non-relativistic approximation. A special
role of the geometric center of the particle trajectory is elucidated. In
quantum case it becomes a 'fuzzy point' with non-commuting coordinates, an
element of non-commutative geometry which enters into the traditional control
problems. We show that its application extends beyond the usually considered
time independent magnetic fields of the quantum Hall effect. Some simple cases
of magnetic control by oscillating fields lead to the stability maps differing
from the traditional Strutt diagram.Comment: 28 pages, 8 figure
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