10,858 research outputs found
The Fornax Spectroscopic Survey I. Survey Strategy and Preliminary Results on the Redshift Distribution of a Complete Sample of Stars and Galaxies
The Fornax Spectroscopic Survey will use the Two degree Field spectrograph
(2dF) of the Anglo-Australian Telescope to obtain spectra for a complete sample
of all 14000 objects with 16.5<=Bj<=19.7 in a 12 square degree area centred on
the Fornax Cluster. By selecting all objects---both stars and
galaxies---independent of morphology, we cover a much larger range of surface
brightness and scale size than previous surveys. In this paper we present
results from the first 2dF field. Redshift distributions and velocity
structures are shown for all observed objects in the direction of Fornax,
including Galactic stars, galaxies in and around the Fornax Cluster, and for
the background galaxy population. The velocity data for the stars show the
contributions from the different Galactic components, plus a small tail to high
velocities. We find no galaxies in the foreground to the cluster in our 2dF
field. The Fornax Cluster is clearly defined kinematically. The mean velocity
from the 26 cluster members having reliable redshifts is 1560+/-80 km/s. They
show a velocity dispersion of 380+/-50 km/s. Large-scale structure can be
traced behind the cluster to a redshift beyond z=0.3. Background compact
galaxies and low surface brightness galaxies are found to follow the general
galaxy distribution.Comment: LaTeX format; uses aa.cls (included). Accepted for publication in
Astronomy and Astrophysic
Kovacs effects in an aging molecular liquid
We study by means of molecular dynamics simulations the aging behavior of a
molecular model of ortho-terphenyl. We find evidence of a a non-monotonic
evolution of the volume during an isothermal-isobaric equilibration process, a
phenomenon known in polymeric systems as Kovacs effect. We characterize this
phenomenology in terms of landscape properties, providing evidence that, far
from equilibrium, the system explores region of the potential energy landscape
distinct from the one explored in thermal equilibrium. We discuss the relevance
of our findings for the present understanding of the thermodynamics of the
glass state.Comment: RevTeX 4, 4 pages, 5 eps figure
Relativistic Quantum Games in Noninertial Frames
We study the influence of Unruh effect on quantum non-zero sum games. In
particular, we investigate the quantum Prisoners' Dilemma both for entangled
and unentangled initial states and show that the acceleration of the
noninertial frames disturbs the symmetry of the game. It is shown that for
maximally entangled initial state, the classical strategy C (cooperation)
becomes the dominant strategy. Our investigation shows that any quantum
strategy does no better for any player against the classical strategies. The
miracle move of Eisert et al (1999 Phys. Rev. Lett. 83 3077) is no more a
superior move. We show that the dilemma like situation is resolved in favor of
one player or the other.Comment: 8 Pages, 2 figures, 2 table
Thermodynamics of the glassy state: effective temperature as an additional system parameter
A system is glassy when the observation time is much smaller than the
equilibration time. A unifying thermodynamic picture of the glassy state is
presented. Slow configurational modes are in quasi-equilibrium at an effective
temperature. It enters thermodynamic relations with the configurational entropy
as conjugate variable. Slow fluctuations contribute to susceptibilities via
quasi-equilibrium relations, while there is also a configurational term.
Fluctuation-dissipation relations also involve the effective temperature.
Fluctuations in the energy are non-universal, however. The picture is supported
by analytically solving the dynamics of a toy model.Comment: 5 pages, REVTEX. Phys. Rev. Lett, to appea
The Holographic Model of Dark Energy and Thermodynamics of Non-Flat Accelerated Expanding Universe
Motivated by recent results on non-vanishing spatial curvature \cite{curve}
we employ the holographic model of dark energy to investigate the validity of
first and second laws of thermodynamics in non-flat (closed) universe enclosed
by apparent horizon and the event horizon measured from the sphere of
horizon named . We show that for the apparent horizon the first law is
roughly respected for different epochs while the second laws of thermodynamics
is respected while for as the system's IR cut-off first law is broken down
and second law is respected for special range of deceleration parameter. It is
also shown that at late-time universe is equal to and the
thermodynamic laws are hold, when the universe has non-vanishing curvature.
Defining the fluid temperature to be proportional to horizon temperature the
range for coefficient of proportionality is obtained provided that the
generalized second law of thermodynamics is hold.Comment: 12 pages, no figure, abstract and text extended, references added,
accepted for publication in JCA
Confronting the Superbubble Model with X-ray Observations of 30 Dor C
We present an analysis of XMM-Newton observations of the superbubble 30 Dor C
and compare the results with the predictions from the standard wind-blown
bubble model. We find that the observed X-ray spectra cannot be fitted
satisfactorily with the model alone and that there is evidence for nonthermal
X-ray emission, which is particularly important at > 4 keV. The total
unabsorbed 0.1-10 keV luminosities of the eastern and western parts of the
bubble are ~3 10^36 erg/s and ~5 10^36 erg/s, respectively. The unabsorbed
0.1-10 keV luminosity of the bubble model is 4 10^36 erg/s and so the power-law
component contributes between 1/3 and 1/2 to the total unabsorbed luminosity in
this energy band. The nature of the hard nonthermal emission is not clear,
although recent supernovae in the bubble may be responsible. We expect that
about one or two core-collapse supernovae could have occured and are required
to explain the enrichment of the hot gas, as evidenced by the overabundance of
alpha-elements by a factor of 3, compared to the mean value of 0.5 solar for
the interstellar medium in the Large Magellanic Cloud. As in previous studies
of various superbubbles, the amount of energy currently present in 30 Dor C is
significantly less than the expected energy input from the enclosed massive
stars over their lifetime. We speculate that a substantial fraction of the
input energy may be radiated in far-infrared by dust grains, which are mixed
with the hot gas because of the thermal conduction and/or dynamic mixing.Comment: 25 pages, 4 figures. To appear in The Astrophysical Journal, August
20, 2004 issu
Interacting holographic dark energy model and generalized second law of thermodynamics in non-flat universe
In the present paper we consider the interacting holographic model of dark
energy to investigate the validity of the generalized second laws of
thermodynamics in non-flat (closed) universe enclosed by the event horizon
measured from the sphere of the horizon named . We show that for as the
system's IR cut-off the generalized second law is respected for the special
range of the deceleration parameter.Comment: 11 pages, no figure
On the reduced density matrix for a chain of free electrons
The properties of the reduced density matrix describing an interval of N
sites in an infinite chain of free electrons are investigated. A commuting
operator is found for arbitrary filling and also for open chains. For a half
filled periodic chain it is used to determine the eigenfunctions for the
dominant eigenvalues analytically in the continuum limit. Relations to the
critical six-vertex model are discussed.Comment: 8 pages, small changes, Equ.(24) corrected, final versio
Land surface phenological response to decadal climate variability across Australia using satellite remote sensing
© 2014 Author(s). Land surface phenological cycles of vegetation greening and browning are influenced by variability in climatic forcing. Quantitative spatial information on phenological cycles and their variability is important for agricultural applications, wildfire fuel accumulation, land management, land surface modeling, and climate change studies. Most phenology studies have focused on temperature-driven Northern Hemisphere systems, where phenology shows annually recurring patterns. However, precipitation-driven non-annual phenology of arid and semi-arid systems (i.e., drylands) received much less attention, despite the fact that they cover more than 30% of the global land surface. Here, we focused on Australia, a continent with one of the most variable rainfall climates in the world and vast areas of dryland systems, where a detailed phenological investigation and a characterization of the relationship between phenology and climate variability are missing. To fill this knowledge gap, we developed an algorithm to characterize phenological cycles, and analyzed geographic and climate-driven variability in phenology from 2000 to 2013, which included extreme drought and wet years. We linked derived phenological metrics to rainfall and the Southern Oscillation Index (SOI). We conducted a continent-wide investigation and a more detailed investigation over the Murray-Darling Basin (MDB), the primary agricultural area and largest river catchment of Australia. Results showed high inter-and intra-annual variability in phenological cycles across Australia. The peak of phenological cycles occurred not only during the austral summer, but also at any time of the year, and their timing varied by more than a month in the interior of the continent. The magnitude of the phenological cycle peak and the integrated greenness were most significantly correlated with monthly SOI within the preceding 12 months. Correlation patterns occurred primarily over northeastern Australia and within the MDB, predominantly over natural land cover and particularly in floodplain and wetland areas. Integrated greenness of the phenological cycles (surrogate of vegetation productivity) showed positive anomalies of more than 2 standard deviations over most of eastern Australia in 2009-2010, which coincided with the transition from the El Niño-induced decadal droughts to flooding caused by La Niña
- …