72 research outputs found
Reliability of fluctuation-induced transport in a Maxwell-demon-type engine
We study the transport properties of an overdamped Brownian particle which is
simultaneously in contact with two thermal baths. The first bath is modeled by
an additive thermal noise at temperature . The second bath is associated
with a multiplicative thermal noise at temperature . The analytical
expressions for the particle velocity and diffusion constant are derived for
this system, and the reliability or coherence of transport is analyzed by means
of their ratio in terms of a dimensionless P\'{e}clet number. We find that the
transport is not very coherent, though one can get significantly higher
currents.Comment: 14 pages, 5 figure
Probing Dark Energy with Supernovae: Exploiting Complementarity with the Cosmic Microwave Background
A primary goal for cosmology and particle physics over the coming decade will
be to unravel the nature of the dark energy that drives the accelerated
expansion of the Universe. In particular, determination of the
equation-of-state of dark energy, w equivalent p/rho, and its time variation,
dw/dz, will be critical for developing theoretical understanding of the new
physics behind this phenomenon. Type Ia supernovae (SNe) and cosmic microwave
background (CMB) anisotropy are each sensitive to the dark energy
equation-of-state. SNe alone can determine w(z) with some precision, while CMB
anisotropy alone cannot because of a strong degeneracy between the matter
density Omega_M and w. However, we show that the Planck CMB mission can
significantly improve the power of a deep SNe survey to probe w and especially
dw/dz. Because CMB constraints are nearly orthogonal to SNe constraints in the
Omega_M-w plane, for constraining w(z) Planck is more useful than precise
determination of Omega_M. We discuss how the CMB/SNe complementarity impacts
strategies for the redshift distribution of a supernova survey to determine
w(z) and conclude that a well-designed sample should include a substantial
number of supernovae out to redshifts z ~ 2.Comment: More discussion of CMB systematics and many new references added.
Matches the PRD versio
QCD ghost f(T)-gravity model
Within the framework of modified teleparallel gravity, we reconstruct a f(T)
model corresponding to the QCD ghost dark energy scenario. For a spatially flat
FRW universe containing only the pressureless matter, we obtain the time
evolution of the torsion scalar T (or the Hubble parameter). Then, we calculate
the effective torsion equation of state parameter of the QCD ghost f(T)-gravity
model as well as the deceleration parameter of the universe. Furthermore, we
fit the model parameters by using the latest observational data including
SNeIa, CMB and BAO data. We also check the viability of our model using a
cosmographic analysis approach. Moreover, we investigate the validity of the
generalized second law (GSL) of gravitational thermodynamics for our model.
Finally, we point out the growth rate of matter density perturbation. We
conclude that in QCD ghost f(T)-gravity model, the universe begins a matter
dominated phase and approaches a de Sitter regime at late times, as expected.
Also this model is consistent with current data, passes the cosmographic test,
satisfies the GSL and fits the data of the growth factor well as the LCDM
model.Comment: 19 pages, 9 figures, 2 tables. arXiv admin note: substantial text
overlap with arXiv:1111.726
Reconstructing the Cosmic Expansion History up to Redshift z=6.29 with the Calibrated Gamma-Ray Bursts
Recently, Gamma-Ray Bursts (GRBs) were proposed to be a complementary
cosmological probe to type Ia supernovae (SNIa). GRBs have been advocated to be
standard candles since several empirical GRB luminosity relations were proposed
as distance indicators. However, there is a so-called circularity problem in
the direct use of GRBs. Recently, a new idea to calibrate GRBs in a completely
cosmology independent manner has been proposed, and the circularity problem can
be solved. In the present work, following the method proposed by Liang {\it et
al.}, we calibrate 70 GRBs with the Amati relation using 307 SNIa. Then,
following the method proposed by Shafieloo {\it et al.}, we smoothly
reconstruct the cosmic expansion history up to redshift with the
calibrated GRBs. We find some new features in the reconstructed results.Comment: 12 pages, 4 figures, 1 table, revtex4; v2: title changed, accepted by
Eur. Phys. J. C; v3: published versio
Influence of s± symmetry on unconventional superconductivity in pnictides above the Pauli limit â two-band model study
The handbook for standardised field and laboratory measurements in terrestrial climate-change experiments and observational studies
Climate change is a worldwide threat to biodiversity and ecosystem structure, functioning, and services. To understand the underlying drivers and mechanisms, and to predict the consequences for nature and people, we urgently need better understanding of the direction and magnitude of climateâchange impacts across the soilâplantâatmosphere continuum. An increasing number of climateâchange studies is creating new opportunities for meaningful and highâquality generalisations and improved process understanding. However, significant challenges exist related to data availability and/or compatibility across studies, compromising opportunities for data reâuse, synthesis, and upscaling. Many of these challenges relate to a lack of an established âbest practiceâ for measuring key impacts and responses. This restrains our current understanding of complex processes and mechanisms in terrestrial ecosystems related to climate change
Taxa transpiratĂłria de mudas de eucalipto em resposta a nĂveis de ĂĄgua no solo e Ă convivĂȘncia com braquiĂĄria
The FuldeâFerrellâLarkinâOvchinnikov State in Pnictides
Fe-based superconductors (FeSC) exhibit all the properties of systems that
allow the formation of a superconducting phase with oscillating order
parameter, called the Fulde--Ferrell--Larkin--Ovchinnikov (FFLO) phase. By the
analysis of the Cooper pair susceptibility in two-band FeSC, such systems are
shown to support the existence of a FFLO phase, regardless of the exhibited
order parameter symmetry. We also show the state with nonzero Cooper pair
momentum, in superconducting FeSC with
symmetry, to be the ground state of the system in a certain parameter range.Comment: 8 pages, 4 figures Journal of Low Temperature Physics, (2013
Plant architecture of Paspalum vaginatum schwartz modified by nitrate and ammonium nutrition
Fungos conidiais em Euterpe oleracea Mart. (açaizeiro) na Ilha do Combu, Parå-Brasil
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