722 research outputs found
Observation of Two New N* Peaks in J/psi -> and Decays
The system in decays of is limited to be
isospin 1/2 by isospin conservation. This provides a big advantage in studying
compared with and experiments which mix
isospin 1/2 and 3/2 for the system. Using 58 million decays
collected with the Beijing Electron Positron Collider, more than 100 thousand
events are obtained. Besides two well known
peaks at 1500 MeV and 1670 MeV, there are two new, clear peaks in
the invariant mass spectrum around 1360 MeV and 2030 MeV. They are the
first direct observation of the peak and a long-sought "missing"
peak above 2 GeV in the invariant mass spectrum. A simple
Breit-Wigner fit gives the mass and width for the peak as MeV and MeV, and for the new peak above 2 GeV
as MeV and MeV, respectively
Multiple-path Quantum Interference Effects in a Double-Aharonov-Bohm Interferometer
We investigate quantum interference effects in a double-Aharonov-Bohm (AB) interferometer consisting of five quantum dots sandwiched between two metallic electrodes in the case of symmetric dot-electrode couplings by the use of the Green’s function equation of motion method. The analytical expression for the linear conductance at zero temperature is derived to interpret numerical results. A three-peak structure in the linear conductance spectrum may evolve into a double-peak structure, and two Fano dips (zero conductance points) may appear in the quantum system when the energy levels of quantum dots in arms are not aligned with one another. The AB oscillation for the magnetic flux threading the double-AB interferometer is also investigated in this paper. Our results show the period of AB oscillation can be converted from 2π to π by controlling the difference of the magnetic fluxes threading the two quantum rings
Correlations between the peak flux density and the position angle of inner-jet in three blazars
We aim to investigate the relation between the long-term flux density and the
position angle (PA) evolution of inner-jet in blazars. We have carried out the
elliptic Gaussian model-fit to the `core' of 50 blazars from 15 GHz VLBA data,
and analyzed the variability properties of three blazars from the model-fit
results. Diverse correlations between the long-term peak flux density and the
PA evolution of the major axis of the `core' have been found in 20% of
the 50 sources. Of them, three typical blazars have been analyzed, which also
show quasi-periodic flux variations of a few years (T). The correlation between
the peak flux density and the PA of inner-jet is positive for S5~0716+714, and
negative for S4~1807+698. The two sources cannot be explained with the
ballistic jet models, the non-ballistic models have been analyzed to explain
the two sub-luminal blazars. A correlation between the peak flux density and
the PA (with a T/4 time lag) of inner-jet is found in [HB89]~1823+568, this
correlation can be explained with a ballistic precession jet model. All the
explanations are based mainly on the geometric beaming effect; physical flux
density variations from the jet base would be considered for more complicated
situations in future, which could account for the no or less significance of
the correlation between the peak flux density and the PA of inner-jet in the
majority blazars of our sample.Comment: 6 pages, 7 figures, accepted for publication in Astrophysics and
Space Scienc
Cosmic coincidence problem and variable constants of physics
The standard model of cosmology is investigated using time dependent
cosmological constant and Newton's gravitational constant . The
total energy content is described by the modified Chaplygin gas equation of
state. It is found that the time dependent constants coupled with the modified
Chaplygin gas interpolate between the earlier matter to the later dark energy
dominated phase of the universe. We also achieve a convergence of parameter
, with minute fluctuations, showing an evolving . Thus our
model fairly alleviates the cosmic coincidence problem which demands
at present time.Comment: 27 pages, 15 figure
Thermodynamics in gravity in the Palatini formalism
We investigate thermodynamics of the apparent horizon in gravity in
the Palatini formalism with non-equilibrium and equilibrium descriptions. We
demonstrate that it is more transparent to understand the horizon entropy in
the equilibrium framework than that in the non-equilibrium one. Furthermore, we
show that the second law of thermodynamics can be explicitly verified in both
phantom and non-phantom phases for the same temperature of the universe outside
and inside the apparent horizon.Comment: 20 pages, no figure, accepted in JCA
Combined constraints on modified Chaplygin gas model from cosmological observed data: Markov Chain Monte Carlo approach
We use the Markov Chain Monte Carlo method to investigate a global
constraints on the modified Chaplygin gas (MCG) model as the unification of
dark matter and dark energy from the latest observational data: the Union2
dataset of type supernovae Ia (SNIa), the observational Hubble data (OHD), the
cluster X-ray gas mass fraction, the baryon acoustic oscillation (BAO), and the
cosmic microwave background (CMB) data. In a flat universe, the constraint
results for MCG model are,
()
,
()
,
()
,
()
, and ()
.Comment: 12 pages, 1figur
Diagnostic for Dilaton Dark Energy
diagnostic can differentiate between different models of dark energy
without the accurate current value of matter density. We apply this geometric
diagnostic to dilaton dark energy(DDE) model and differentiate DDE model from
LCDM. We also investigate the influence of coupled parameter on the
evolutive behavior of with respect to redshift . According to the
numerical result of , we get the current value of equation of state
=-0.952 which fits the WMAP5+BAO+SN very well.Comment: 6 pages and 6 figures
In vivo mechanical loading rapidly activates beta-catenin signaling in osteocytes through a prostaglandin mediated mechanism
Statefinder and Om Diagnostics for Interacting New Holographic Dark Energy Model and Generalized Second Law of Thermodynamics
In this work, we have considered that the flat FRW universe is filled with
the mixture of dark matter and the new holographic dark energy. If there is an
interaction, we have investigated the natures of deceleration parameter,
statefinder and diagnostics. We have examined the validity of the first
and generalized second laws of thermodynamics under these interactions on the
event as well as apparent horizon. It has been observed that the first law is
violated on the event horizon. However, the generalized second law is valid
throughout the evolution of the universe enveloped by the apparent horizon.
When the event horizon is considered as the enveloping horizon, the generalized
second law is found to break down excepting at late stage of the universe.Comment: 9 pages, 13 figure
- …