143,384 research outputs found
Comparing the Tsallis distribution with and without thermodynamical description in p+p collisions
We compare two types of Tsallis distribution, i.e., with and without
thermodynamical description, using the experimental data from the STAR, PHENIX,
ALICE and CMS Collaborations on the rapidity and energy dependence of the
transverse momentum spectra in p+p collisions. Both of them can give us the
similar fitting power to the particle spectra. We show that the Tsallis
distribution with thermodynamical description gives lower temperatures than the
ones without it. The extra factor (transverse mass) in the Tsallis
distribution with thermodynamical description plays an important role in the
discrepancies between the two types of Tsallis distribution. But for the heavy
particles, the choice to use the or (transverse energy) in the
Tsallis distribution becomes more crucial.Comment: 9 pages, 5 figure
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Commercial property prices and bank performance
We seek to assess the effect of changes in commercial property prices on bank behaviour
and performance in a range of industrialised economies, extending the existing micro literature on
bank performance. The results suggest that, consistent with macro-level studies, commercial property
prices have a marked impact on the behaviour and performance of individual banks. The signs found
are consistent with a view that commercial property provides important forms of collateral that are
perceived by banks to reduce risk and encourage lending. Such an impact exists even when
conventional independent variables determining bank performance are included. Moreover, there is
evidence that the magnitude of this impact is related to the size of the bank, the direction of
commercial property price movements, and regional factors. The results have implications for risk
managers, regulators and monetary policy makers. Notably, they underline the crucial relevance of
commercial property prices as a macroprudential variable that warrants close scrutiny by the
authorities. They also highlight the need to develop indicators of individual bank exposure to the
property market that could help to calibrate the potential impact of changes in prices in stress tests
Gravitational Lensing Statistics as a Probe of Dark Energy
By using the comoving distance, we derive an analytic expression for the
optical depth of gravitational lensing, which depends on the redshift to the
source and the cosmological model characterized by the cosmic mass density
parameter , the dark energy density parameter and its
equation of state . It is shown that, the larger the
dark energy density is and the more negative its pressure is, the higher the
gravitational lensing probability is. This fact can provide an independent
constraint for dark energy.Comment: 9 pages, 2 figure
Lifetime Improvement in Wireless Sensor Networks via Collaborative Beamforming and Cooperative Transmission
Collaborative beamforming (CB) and cooperative transmission (CT) have
recently emerged as communication techniques that can make effective use of
collaborative/cooperative nodes to create a virtual
multiple-input/multiple-output (MIMO) system. Extending the lifetime of
networks composed of battery-operated nodes is a key issue in the design and
operation of wireless sensor networks. This paper considers the effects on
network lifetime of allowing closely located nodes to use CB/CT to reduce the
load or even to avoid packet-forwarding requests to nodes that have critical
battery life. First, the effectiveness of CB/CT in improving the signal
strength at a faraway destination using energy in nearby nodes is studied.
Then, the performance improvement obtained by this technique is analyzed for a
special 2D disk case. Further, for general networks in which
information-generation rates are fixed, a new routing problem is formulated as
a linear programming problem, while for other general networks, the cost for
routing is dynamically adjusted according to the amount of energy remaining and
the effectiveness of CB/CT. From the analysis and the simulation results, it is
seen that the proposed method can reduce the payloads of energy-depleting nodes
by about 90% in the special case network considered and improve the lifetimes
of general networks by about 10%, compared with existing techniques.Comment: Invited paper to appear in the IEE Proceedings: Microwaves, Antennas
and Propagation, Special Issue on Antenna Systems and Propagation for Future
Wireless Communication
Accelerating universe from gravitational leakage into extra dimensions: confrontation with SNeIa
There is mounting observational evidence that the expansion of our universe
is undergoing an acceleration. A dark energy component has usually been invoked
as the most feasible mechanism for the acceleration. However, it is desirable
to explore alternative possibilities motivated by particle physics before
adopting such an untested entity. In this work, we focus our attention on an
acceleration mechanism: one arising from gravitational leakage into extra
dimensions. We confront this scenario with high- type Ia supernovae compiled
by Tonry et al. (2003) and recent measurements of the X-ray gas mass fractions
in clusters of galaxies published by Allen et al. (2002,2003). A combination of
the two databases gives at a 99% confidence level that
, , and
, indicating a closed universe. We then
constrain the model using the test of the turnaround redshift, , at
which the universe switches from deceleration to acceleration. We show that, in
order to explain that acceleration happened earlier than within
the framework of gravitational leakage into extra dimensions, a low matter
density, , or a closed universe is necessary.Comment: 16 pages, 4 figures, accepted for publication in Ap
Superconductivity in Ti-doped Iron-Arsenide Compound Sr4Cr0.8Ti1.2O6Fe2As2
Superconductivity was achieved in Ti-doped iron-arsenide compound
Sr4Cr0.8Ti1.2O6Fe2As2 (abbreviated as Cr-FeAs-42622). The x-ray diffraction
measurement shows that this material has a layered structure with the space
group of \emph{P4/nmm}, and with the lattice constants a = b = 3.9003 A and c =
15.8376 A. Clear diamagnetic signals in ac susceptibility data and
zero-resistance in resistivity data were detected at about 6 K, confirming the
occurrence of bulk superconductivity. Meanwhile we observed a superconducting
transition in the resistive data with the onset transition temperature at 29.2
K, which may be induced by the nonuniform distribution of the Cr/Ti content in
the FeAs-42622 phase, or due to some other minority phase.Comment: 3 pages, 3 figure
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