1,103 research outputs found
Cosmological Constraints on Dissipative Models of Inflation
(Abridged) We study dissipative inflation in the regime where the dissipative
term takes a specific form, \Gamma=\Gamma(\phi), analyzing two models in the
weak and strong dissipative regimes with a SUSY breaking potential. After
developing intuition about the predictions from these models through analytic
approximations, we compute the predicted cosmological observables through full
numerical evolution of the equations of motion, relating the mass scale and
scale of dissipation to the characteristic amplitude and shape of the
primordial power spectrum. We then use Markov Chain Monte Carlo techniques to
constrain a subset of the models with cosmological data from the cosmic
microwave background (WMAP three-year data) and large scale structure (SDSS
Luminous Red Galaxy power spectrum). We find that the posterior distributions
of the dissipative parameters are highly non-Gaussian and their allowed ranges
agree well with the expectations obtained using analytic approximations. In the
weak regime, only the mass scale is tightly constrained; conversely, in the
strong regime, only the dissipative coefficient is tightly constrained. A lower
limit is seen on the inflation scale: a sub-Planckian inflaton is disfavoured
by the data. In both weak and strong regimes, we reconstruct the limits on the
primordial power spectrum and show that these models prefer a {\it red}
spectrum, with no significant running of the index. We calculate the reheat
temperature and show that the gravitino problem can be overcome with large
dissipation, which in turn leads to large levels of non-Gaussianity: if
dissipative inflation is to evade the gravitino problem, the predicted level of
non-Gaussianity might be seen by the Planck satellite.Comment: 14 pages, 9 figures, Accepted by JCAP without text changes,
References adde
First Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Implications for Inflation
We confront predictions of inflationary scenarios with the WMAP data, in
combination with complementary small-scale CMB measurements and large-scale
structure data. The WMAP detection of a large-angle anti-correlation in the
temperature--polarization cross-power spectrum is the signature of adiabatic
superhorizon fluctuations at the time of decoupling. The WMAP data are
described by pure adiabatic fluctuations: we place an upper limit on a
correlated CDM isocurvature component. Using WMAP constraints on the shape of
the scalar power spectrum and the amplitude of gravity waves, we explore the
parameter space of inflationary models that is consistent with the data. We
place limits on inflationary models; for example, a minimally-coupled lambda
phi^4 is disfavored at more than 3-sigma using WMAP data in combination with
smaller scale CMB and large scale structure survey data. The limits on the
primordial parameters using WMAP data alone are: n_s(k_0=0.002
Mpc^{-1})=1.20_{-0.11}^{+0.12}, dn/dlnk=-0.077^{+0.050}_{- 0.052}, A(k_0=0.002
Mpc}^{-1})=0.71^{+0.10}_{-0.11} (68% CL), and r(k_0=0.002 Mpc^{-1})<1.28 (95%
CL).Comment: Accepted by ApJ; 49 pages, 9 figures. V2: Gives constraints from WMAP
data alone. Corrected approximation which made the constraints in Table 1 to
shift slightly. Corrected the Inflation Flow following the revision to
Kinney, astro-ph/0206032. No conclusions have been changed. For a detailed
list of changes see http://www.astro.princeton.edu/~hiranya/README.ERRATA.tx
Primordial Black Holes, Eternal Inflation, and the Inflationary Parameter Space after WMAP5
We consider constraints on inflation driven by a single, minimally coupled
scalar field in the light of the WMAP5 dataset, as well as ACBAR and the
SuperNova Legacy Survey. We use the Slow Roll Reconstruction algorithm to
derive optimal constraints on the inflationary parameter space. The scale
dependence in the slope of the scalar spectrum permitted by WMAP5 is large
enough to lead to viable models where the small scale perturbations have a
substantial amplitude when extrapolated to the end of inflation. We find that
excluding parameter values which would cause the overproduction of primordial
black holes or even the onset of eternal inflation leads to potentially
significant constraints on the slow roll parameters. Finally, we present a more
sophisticated approach to including priors based on the total duration of
inflation, and discuss the resulting restrictions on the inflationary parameter
space.Comment: v2: version published in JCAP. Minor clarifications and references
adde
Constraining Inflation
Slow roll reconstruction is derived from the Hamilton-Jacobi formulation of
inflationary dynamics. It automatically includes information from sub-leading
terms in slow roll, and facilitatesthe inclusion of priors based on the
duration on inflation. We show that at low inflationary scales the
Hamilton-Jacobi equations simplify considerably. We provide a new
classification scheme for inflationary models, based solely on the number of
parameters needed to specify the potential, and provide forecasts for likely
bounds on the slow roll parameters from future datasets. A minimal running of
the spectral index, induced solely by the first two slow roll parameters
(\epsilon and \eta) appears to be effectively undetectable by realistic Cosmic
Microwave Background experiments. However, we show that the ability to detect
this signal increases with the lever arm in comoving wavenumber, and we
conjecture that high redshift 21 cm data may allow tests of second order
consistency conditions on inflation. Finally, we point out that the second
order corrections to the spectral index are correlated with the inflationary
scale, and thus the amplitude of the CMB B-mode.Comment: 32 pages. v
Cross-Correlation Detection of Point Sources in WMAP First Year Data
We apply a Cross-correlation (CC) method developed previously for detecting
gamma-ray point sources to the WMAP first year data by using the Point-Spread
Function of WMAP and obtain a full sky CC coefficient map. Analyzing this map,
we find that the CC method is a powerful tool to examine the WMAP foreground
residuals which can be further cleaned accordingly. Evident foreground signals
are found in WMAP foreground cleaned maps and Tegmark cleaned map. In this
process 101 point-sources are detected, and 26 of them are new sources besides
the originally listed WMAP 208 sources. We estimate the flux of these new
sources and verify them by another method. As a result, a revised mask file
based on the WMAP first year data is produced by including these new sources.Comment: 14 pages, 10 figures; accepted for publication by ChJA
New Solutions of the Inflationary Flow Equations
The inflationary flow equations are a frequently used method of surveying the
space of inflationary models. In these applications the infinite hierarchy of
differential equations is truncated in a way which has been shown to be
equivalent to restricting the set of models considered to those characterized
by polynomial inflaton potentials. This paper explores a different method of
solving the flow equations, which does not truncate the hierarchy and in
consequence covers a much wider class of models while retaining the practical
usability of the standard approach.Comment: References added, and a couple of comment
Boundary Effective Field Theory and Trans-Planckian Perturbations: Astrophysical Implications
We contrast two approaches to calculating trans-Planckian corrections to the
inflationary perturbation spectrum: the New Physics Hypersurface [NPH] model,
in which modes are normalized when their physical wavelength first exceeds a
critical value, and the Boundary Effective Field Theory [BEFT] approach, where
the initial conditions for all modes are set at the same time, and modified by
higher dimensional operators enumerated via an effective field theory
calculation. We show that these two approaches -- as currently implemented --
lead to radically different expectations for the trans-Planckian corrections to
the CMB and emphasize that in the BEFT formalism we expect the perturbation
spectrum to be dominated by quantum gravity corrections for all scales shorter
than some critical value. Conversely, in the NPH case the quantum effects only
dominate the longest modes that are typically much larger than the present
horizon size. Furthermore, the onset of the breakdown in the standard
inflationary perturbation calculation predicted by the BEFT formalism is likely
to be associated with a feature in the perturbation spectrum, and we discuss
the observational signatures of this feature in both CMB and large scale
structure observations. Finally, we discuss possible modifications to both
calculational frameworks that would resolve the contradictions identified here.Comment: Reworded commentary, reference added (v2) References added (v3
Assessment of the landscape characteristics of the habitat of wild elephants in Sri Lanka
For the long term conservation of wild elephants in Sri Lanka, information on landscape characteristics i.e. where and what landscape support the population of wild elephants is vital. Though there have been several studies on the biology, distribution and habitat preferences of elephant in the past yet landscape characters have not been considered any detail. Hence the present study was done using 5X5km grid overlaid on 1:50000 scale land use maps of the country covering the historic elephant range in Sri Lanka. In 2011, each of the 25 km2 cell was covered by interviewing knowledgeable forest communities and wildlife officers as a reliable source of information on presence and absent of elephants in the area. Vegetation types, terrain, water availability and road densities & human population densities were recognized as landscape characteristics. The study was focused to assess correlation among landscape characters and elephant presence. Elephants occupied >30% of Sri Lanka‟s land area with approximately 40% being contained within protected areas where human access is regulated. Elephant range was largely contiguous except for a few isolated forest areas. However the large portion of elephant range is not protected. Prevalence of monsoonal forest and mosaic of different vegetation types were the strongest positive predictors of elephant presence. Road density and human population density were significant negative predictors. That the elephant populations had increased was the common perception among 78% of respondents. Although 36% of respondents regarded elephants as a threat, 93% support their legal protection. This positive attitude toward protection would facilitate conservation efforts. Establishment of additional protected areas and forest connectivity through implementing proper land use plans in areas where the elephants are present would enhance elephant conservation. In addition to that further studies could be implemented to plan for the maintenance of viable population of wild elephants in Sri Lanka
Bergamot natural products eradicate cancer stem cells (CSCs) by targeting mevalonate, Rho-GDI-signalling and mitochondrial metabolism
Here, we show that a 2:1 mixture of Brutieridin and Melitidin, termed “BMF”, has a statin-like properties, which
blocks the action of the rate-limiting enzyme for mevalonate biosynthesis, namely HMGR (3-hydroxy-3-methylglutaryl-
CoA-reductase). Moreover, our results indicate that BMF functionally inhibits several key characteristics
of CSCs. More specifically, BMF effectively i) reduced ALDH activity, ii) blocked mammosphere
formation and iii) inhibited the activation of CSC-associated signalling pathways (STAT1/3, Notch and Wnt/
beta-catenin) targeting Rho-GDI-signalling. In addition, BMF metabolically inhibited mitochondrial respiration
(OXPHOS) and fatty acid oxidation (FAO). Importantly, BMF did not show the same toxic side-effects in normal
fibroblasts that were observed with statins. Lastly, we show that high expression of the mRNA species encoding
HMGR is associated with poor clinical outcome in breast cancer patients, providing a potential companion
diagnostic for BMF-directed personalized therapy
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