91,217 research outputs found
Quantifying the impact of future Sandage-Loeb test data on dark energy constraints
The Sandage-Loeb (SL) test is a unique method to probe dark energy in the
"redshift desert" of , and thus it provides an important
supplement to the other dark energy probes. Therefore, it is of great
importance to quantify how the future SL test data impact on the dark energy
constraints. To avoid the potential inconsistency in data, we use the
best-fitting model based on the other geometric measurements as the fiducial
model to produce 30 mock SL test data. The 10-yr, 20-yr, and 30-yr observations
of SL test are analyzed and compared in detail. We show that compared to the
current combined data of type Ia supernovae, baryon acoustic oscillation,
cosmic microwave background, and Hubble constant, the 30-yr observation of SL
test could improve the constraint on by about and the
constraint on by about . Furthermore, the SL test can also improve the
measurement of the possible direct interaction between dark energy and dark
matter. We show that the SL test 30-yr data could improve the constraint on
by about and for the and models, respectively.Comment: 10 pages, 3 figure
Parameter estimation with Sandage-Loeb test
The Sandage-Loeb (SL) test directly measures the expansion rate of the
universe in the redshift range of by detecting redshift
drift in the spectra of Lyman- forest of distant quasars. We discuss
the impact of the future SL test data on parameter estimation for the
CDM, the CDM, and the CDM models. To avoid the potential
inconsistency with other observational data, we take the best-fitting dark
energy model constrained by the current observations as the fiducial model to
produce 30 mock SL test data. The SL test data provide an important supplement
to the other dark energy probes, since they are extremely helpful in breaking
the existing parameter degeneracies. We show that the strong degeneracy between
and in all the three dark energy models is well broken by the
SL test. Compared to the current combined data of type Ia supernovae, baryon
acoustic oscillation, cosmic microwave background, and Hubble constant, the
30-yr observation of SL test could improve the constraints on and
by more than 60\% for all the three models. But the SL test can only
moderately improve the constraint on the equation of state of dark energy. We
show that a 30-yr observation of SL test could help improve the constraint on
constant by about 25\%, and improve the constraints on and by
about 20\% and 15\%, respectively. We also quantify the constraining power of
the SL test in the future high-precision joint geometric constraints on dark
energy. The mock future supernova and baryon acoustic oscillation data are
simulated based on the space-based project JDEM. We find that the 30-yr
observation of SL test would help improve the measurement precision of
, , and by more than 70\%, 20\%, and 60\%, respectively,
for the CDM model.Comment: 16 pages, 9 figures, 3 tables; adding a new section to address future
SN and BAO observations; accepted for publication in JCA
Neutrinos and dark energy after Planck and BICEP2: data consistency tests and cosmological parameter constraints
The detection of the B-mode polarization of the cosmic microwave background
(CMB) by the BICEP2 experiment implies that the tensor-to-scalar ratio
should be involved in the base standard cosmology. In this paper, we extend the
CDM++neutrino/dark radiation models by replacing the cosmological
constant with the dynamical dark energy with constant . Four neutrino plus
dark energy models are considered, i.e., the CDM+, CDM+r +
, CDM+r + + , and CDM+r + + models. The current observational
data considered in this paper include the Planck temperature data, the WMAP
9-year polarization data, the baryon acoustic oscillation data, the Hubble
constant direct measurement data, the Planck Sunyaev-Zeldovich cluster counts
data, the Planck CMB lensing data, the cosmic shear data, and the BICEP2
polarization data. We test the data consistency in the four cosmological
models, and then combine the consistent data sets to perform joint constraints
on the models. We focus on the constraints on the parameters , ,
, and .Comment: 22 pages, 8 figures, 5 table
Digging for biosynthetic dark matter.
An analysis of bacterial communities in soil samples from around the world reveals unexplored diversity in biosynthetic enzymes
Surjective endomorphisms of projective surfaces -- the existence of infinitely many dense orbits
Let be a surjective endomorphism of a normal projective
surface. When , applying an (iteration of)
-equivariant minimal model program (EMMP), we determine the geometric
structure of . Using this, we extend the second author's result to singular
surfaces to the extent that either has an -invariant non-constant
rational function, or has infinitely many Zariski-dense forward orbits;
this result is also extended to Adelic topology (which is finer than Zariski
topology)
"Hard-scattering" approach to very hindered magnetic-dipole transitions in quarkonium
For a class of hindered magnetic dipole () transition processes, such as
(the discovery channel of the meson),
the emitted photon is rather energetic so that the traditional approaches based
on multipole expansion may be invalidated. We propose that a "hard-scattering"
picture, somewhat analogous to the pion electromagnetic form factor at large
momentum transfer, may be more plausible to describe such types of transition
processes. We work out a simple factorization formula at lowest order in the
strong coupling constant, which involves convolution of the Schr\"odinger wave
functions of quarkonia with a perturbatively calculable part induced by
exchange of one semihard gluon between quark and antiquark. This formula,
without any freely adjustable parameters, is found to agree with the measured
rate of rather well, and can also reasonably
account for other recently measured hindered transition rates. The
branching fractions of are also
predicted.Comment: v3; 5 pages, 1 figure and 1 table; title changed, presentation
improve
Thermodynamics of two-dimensional conformal field theory dual to black holes
In this note we investigate the first law of thermodynamics of the
two-dimensional conformal field theory (CFT) that is dual to black holes. We
start from the Cardy formula and get the CFT thermodynamics with minimal
reasonable assumptions. We use both the microcanonical ensemble and canonical
ensemble versions of the Cardy formula. In the black hole/CFT correspondence
the black hole is dual to a CFT with excitations, and the black hole mass
and charge correspond to the energy and charge of the excited CFT. The CFT
left- and right-moving central charges should be quantized, and so we
assume that they are mass-independent. Also we assume the difference of the
left- and right-moving sector levels is mass-independent dual to
level matching condition. The thermodynamics of two-dimensional CFT we get is
universal and supports the thermodynamics method of black hole/CFT
correspondence.Comment: 10 page
Redshift drift exploration for interacting dark energy
By detecting redshift drift in the spectra of Lyman- forest of
distant quasars, Sandage-Loeb (SL) test directly measures the expansion of the
universe, covering the "redshift desert" of . Thus this
method is definitely an important supplement to the other geometric
measurements and will play a crucial role in cosmological constraints. In this
paper, we quantify the ability of SL test signal by a CODEX-like spectrograph
for constraining interacting dark energy. Four typical interacting dark energy
models are considered: (i) , (ii) ,
(iii) , and (iv) . The results show
that for all the considered interacting dark energy models, relative to the
current joint SN+BAO+CMB+ observations, the constraints on and
would be improved by about 60\% and 30--40\%, while the constraints on
and would be slightly improved, with a 30-yr observation of SL
test. We also explore the impact of SL test on future joint geometric
observations. In this analysis, we take the model with as an
example, and simulate future SN and BAO data based on the space-based project
WFIRST. We find that in the future geometric constraints, the redshift drift
observations would help break the geometric degeneracies in a meaningful way,
thus the measurement precisions of , , , and could
be substantially improved using future probes.Comment: 6 pages, 5 figures; accepted for publication in EPJC. arXiv admin
note: text overlap with arXiv:1407.712
- …