1,441 research outputs found
Gauge-invariant perturbations at second order in two-field inflation
We study the second-order gauge-invariant adiabatic and isocurvature
perturbations in terms of the scalar fields present during inflation, along
with the related fully non-linear space gradient of these quantities. We
discuss the relation with other perturbation quantities defined in the
literature. We also construct the exact cubic action of the second-order
perturbations (beyond any slow-roll or super-horizon approximations and
including tensor perturbations), both in the uniform energy density gauge and
the flat gauge in order to settle various gauge-related issues. We thus provide
the tool to calculate the exact non-Gaussianity beyond slow-roll and at any
scale.Comment: 28 pages, no figures. v2: Added a summary subsection 4.3 with further
discussion of the results. Generalized all super-horizon results of section 4
and appendix A to exact ones. Other minor textual changes and references
added. Conclusions unchanged. Matches published versio
Free Abelian 2-Form Gauge Theory: BRST Approach
We discuss various symmetry properties of the Lagrangian density of a four (3
+ 1)-dimensional (4D) free Abelian 2-form gauge theory within the framework of
Becchi-Rouet-Stora-Tyutin (BRST) formalism. The present free Abelian gauge
theory is endowed with a Curci-Ferrari type condition which happens to be a key
signature of the 4D non-Abelian 1-form gauge theory. In fact, it is due to the
above condition that the nilpotent BRST and anti-BRST symmetries of the theory
are found to be absolutely anticommuting in nature. For our present 2-form
gauge theory, we discuss the BRST, anti-BRST, ghost and discrete symmetry
properties of the Lagrangian densities and derive the corresponding conserved
charges. The algebraic structure, obeyed by the above conserved charges, is
deduced and the constraint analysis is performed with the help of the
physicality criteria where the conserved and nilpotent (anti-)BRST charges play
completely independent roles. These physicality conditions lead to the
derivation of the above Curci-Ferrari type restriction, within the framework of
BRST formalism, from the constraint analysis.Comment: LaTeX file, 21 pages, journal referenc
Curvaton and the inhomogeneous end of inflation
We study the primordial density perturbations and non-Gaussianities generated
from the combined effects of an inhomogeneous end of inflation and curvaton
decay in hybrid inflation. This dual role is played by a single isocurvature
field which is massless during inflation but acquire a mass at the end of
inflation via the waterfall phase transition. We calculate the resulting
primordial non-Gaussianity characterized by the non-linearity parameter,
, recovering the usual end-of-inflation result when the field decays
promptly and the usual curvaton result if the field decays sufficiently late.Comment: 13 pages, 5 figure
Gravitational Wave Background and Non-Gaussianity as a Probe of the Curvaton Scenario
We study observational implications of the stochastic gravitational wave
background and a non-Gaussian feature of scalar perturbations on the curvaton
mechanism of the generation of density/curvature fluctuations, and show that
they can determine the properties of the curvaton in a complementary manner to
each other. Therefore even if Planck could not detect any non-Gaussianity,
future space-based laser interferometers such as DECIGO or BBO could
practically exhaust its parameter space.Comment: 16 pages, 2 figure
Density Fluctuations in Thermal Inflation and Non-Gaussianity
We consider primordial fluctuations in thermal inflation scenario. Since the
thermal inflation drives about 10 -folds after the standard inflation, the
time of horizon-exit during inflation corresponding to the present
observational scale shifts toward the end of inflation. It generally makes the
primordial power spectrum more deviated from a scale-invariant one and hence
renders some models inconsistent with observations. We present a mechanism of
generating the primordial curvature perturbation at the end of thermal
inflation utilizing a fluctuating coupling of a flaton field with the fields in
thermal bath. We show that, by adopting the mechanism, some inflation models
can be liberated even in the presence of the thermal inflation. We also discuss
non-Gaussianity in the mechanism and show that large non-Gaussianity can be
generated in this scenario.Comment: 15 pages, 1 figures, minor change
Short communication: Current fishery status of ribbonfish Trichiurus lepturus Linnaeus, 1758) (Trichiuridae) from Makran coast (northeast Arabian Sea)
Ribbonfishes are typical inmates of pelagic waters of the world oceans and it is a cosmopolitan species (Parin, 1968., 1988; Nakamura and Parin, 1993). It is a slim, commercially important marine species of Pakistan. Ribbonfish are spread in the Indo-Pacific and Atlantic areas as well as throughout the Indian coast with plenty in the northwest and central east coasts (Nair and Prakasan, 2003). They belong to the family Trichiuridae and are represented in Pakistani waters by two species namely, Trichiurus lepturus, and Lepturacanthus savala .These species are found all over the year but the abundant species in Pakistan is T. lepturus (Bianchi, 1985)
Affleck-Dine baryogenesis with modulated reheating
Modulated reheating scenario is one of the most attractive models that
predict possible detections of not only the primordial non-Gaussianity but also
the tensor fluctuation through future CMB observations such as the Planck
satellite, the PolarBeaR and the LiteBIRD satellite experiments. We study the
baryonic-isocurvature fluctuations in the Affleck-Dine baryogenesis with the
modulated reheating scenario. We show that the Affleck-Dine baryogenesis can be
consistent with the modulated reheating scenario with respect to the current
observational constraint on the baryonic-isocurvature fluctuations.Comment: 7 page
Multiple field inflation
Inflation offers a simple model for very early evolution of our Universe and
the origin of primordial perturbations on large scales. Over the last 25 years
we have become familiar with the predictions of single-field models, but
inflation with more than one light scalar field can alter preconceptions about
the inflationary dynamics and our predictions for the primordial perturbations.
I will discuss how future observational data could distinguish between
inflation driven by one field, or many fields. As an example, I briefly review
the curvaton as an alternative to the inflaton scenario for the origin of
structure.Comment: 27 pages, no figures. To appear in proceedings of 22nd IAP
Colloquium, Inflation +25, Paris, June 200
Local non-Gaussianity from rapidly varying sound speeds
We study the effect of non-trivial sound speeds on local-type non-Gaussianity
during multiple-field inflation. To this end, we consider a model of
multiple-field DBI and use the deltaN formalism to track the super-horizon
evolution of perturbations. By adopting a sum separable Hubble parameter we
derive analytic expressions for the relevant quantities in the two-field case,
valid beyond slow variation. We find that non-trivial sound speeds can, in
principle, curve the trajectory in such a way that significant local-type
non-Gaussianity is produced. Deviations from slow variation, such as rapidly
varying sound speeds, enhance this effect. To illustrate our results we
consider two-field inflation in the tip regions of two warped throats and find
large local-type non-Gaussianity produced towards the end of the inflationary
process.Comment: 30 pages, 7 figures; typos corrected, references added, accepted for
publication in JCA
Application of water hyacinth in phytoremediation of wastewater
Wastewater is any water source that a human has used for domestic, agricultural, commercial, or industrial activity. Wastewater needs to be treated before being discharged into the environment to reduce contamination of water bodies. The wastewater treatment must follow the Environmental Quality (Sewage) Regulations, 2009. Rivers in Malaysia continue to suffer wastewater pollution from the inefficiency of treatment. Wastewater has been recognized as the significant cause of these issues. Many physical, chemical, and biological techniques have evolved for sewage treatment. It has been observed that biological procedures are advantageous, and one of these procedures that can be considered is phytoremediation. Thus, this study investigated the effectiveness of water hyacinths in treating wastewater, such as the effluent from the wastewater treatment plant, river, and pond in Pusat Asasi, UiTM Dengkil, Selangor, by phytoremediation. Different parameters of pH, suspended solids, phosphorus, ammonia-nitrogen, nitrite-nitrogen, nitrate-nitrogen, chemical oxygen demand and biological oxygen demand have been assessed. The research has been conducted with experimental works of 14 days. The laboratory works showed a significant reduction in most parameters after two weeks of phytoremediation
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