249 research outputs found
Fixed point results using Ft-contractions in ordered metric spaces having t-property
In this paper, we prove the existence of fixed points of Ft-contraction mappings in partially ordered metric spaces not necessarily complete. We require that the ordered metric space has the t-property, which is a new concept introduced recently by Rashid et.al. We also give some examples to illustrate the new concepts and obtained results.The publication of this article was funded by the Qatar National Library
Mixed g-monotone property and quadruple fixed point theorems in partially ordered metric spaces
Tripled coincidence point theorems for a φ-contractive mapping in a complete metric space without the mixed g-monotone property
Ginzburg-Landau model with small pinning domains
We consider a Ginzburg-Landau type energy with a piecewise constant pinning
term in the potential . The function is different from
1 only on finitely many disjoint domains, called the {\it pinning domains}.
These pinning domains model small impurities in a homogeneous superconductor
and shrink to single points in the limit ; here, \v is the inverse of
the Ginzburg-Landau parameter. We study the energy minimization in a smooth
simply connected domain with Dirichlet boundary
condition on \d \O, with topological degree {\rm deg}_{\d \O} (g) = d
>0. Our main result is that, for small \v, minimizers have distinct
zeros (vortices) which are inside the pinning domains and they have a degree
equal to 1. The question of finding the locations of the pinning domains with
vortices is reduced to a discrete minimization problem for a finite-dimensional
functional of renormalized energy. We also find the position of the vortices
inside the pinning domains and show that, asymptotically, this position is
determined by {\it local renormalized energy} which does not depend on the
external boundary conditions.Comment: 39 page
Shocks and dust formation in nova V809 Cep
The discovery that many classical novae produce detectable GeV -ray
emission has raised the question of the role of shocks in nova eruptions. Here
we use radio observations of nova V809 Cep (Nova Cep 2013) with the Jansky Very
Large Array to show that it produced non-thermal emission indicative of
particle acceleration in strong shocks for more than a month starting about six
weeks into the eruption, quasi-simultaneous with the production of dust.
Broadly speaking, the radio emission at late times -- more than a six months or
so into the eruption -- is consistent with thermal emission from of freely expanding, ~K ejecta. At 4.6 and 7.4 GHz, however, the
radio light-curves display an initial early-time peak 76 days after the
discovery of the eruption in the optical (). The brightness temperature at
4.6 GHz on day 76 was greater than , an order of magnitude above what
is expected for thermal emission. We argue that the brightness temperature is
the result of synchrotron emission due to internal shocks within the ejecta.
The evolution of the radio spectrum was consistent with synchrotron emission
that peaked at high frequencies before low frequencies, suggesting that the
synchrotron from the shock was initially subject to free-free absorption by
optically thick ionized material in front of the shock. Dust formation began
around day 37, and we suggest that internal shocks in the ejecta were
established prior to dust formation and caused the nucleation of dust
Some new fixed point theorems for the Meir-Keeler contractions on partial Hausdorff metric spaces
Common fixed points of two pairs of mappings satisfying (E.A)-property in partial metric spaces
Multi-Wavelength Observations Of A New Redback Millisecond Pulsar 4FGL J1910.7-5320
We present the study of multi-wavelength observations of an unidentified
Fermi Large Area Telescope (LAT) source, 4FGL J1910.7-5320, a new candidate
redback millisecond pulsar binary. In the 4FGL 95% error region of 4FGL
J1910.7-5320, we find a possible binary with a 8.36-hr orbital period from the
Catalina Real-Time Transient Survey (CRTS), confirmed by optical spectroscopy
using the SOAR telescope. This optical source was recently independently
discovered as a redback pulsar by the TRAPUM project, confirming our
prediction. We fit the optical spectral energy distributions of 4FGL
J1910.7-5320 with a blackbody model, inferring a maximum distance of 4.1 kpc by
assuming that the companion fills its Roche-lobe with a radius of R = 0.7R_sun.
Using a 12.6 ks Chandra X-ray observation, we identified an X-ray counterpart
for 4FGL J1910.7-5320, with a spectrum that can be described by an absorbed
power-law with a photon index of 1.0+/-0.4. The spectrally hard X-ray emission
shows tentative evidence for orbital variability. Using more than 12 years of
Fermi-LAT data, we refined the position of the {\gamma}-ray source, and the
optical candidate still lies within the 68% positional error circle. In
addition to 4FGL J1910.7-5320, we find a variable optical source with a
periodic signal of 4.28-hr inside the 4FGL catalog 95% error region of another
unidentified Fermi source, 4FGL J2029.5-4237. However, the {\gamma}-ray source
does not have a significant X-ray counterpart in a 11.7 ks Chandra observation,
with a 3-{\sigma} flux upper limit of 2.4*10^-14 erg cm^-2 s^-1 (0.3-7 keV).
Moreover, the optical source is outside our updated Fermi-LAT 95% error circle.
These observational facts all suggest that this new redback millisecond pulsar
powers the {\gamma}-ray source 4FGL J1910.7-5320 while 4FGL J2029.5-4237 is
unlikely the {\gamma}-ray counterpart to the 4.28-hr variable.Comment: Accepted for publication in Ap
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