Nonperturbative infrared effects for light scalar fields in de Sitter space

We study the phi^4 scalar field theory in de Sitter space using the 2PI effective action formalism. This formalism enables us to investigate the nonperturbative quantum effects. We use the mean field and gap equations and calculate the physical mass and effective potential. We find that nonperturbative infrared effects on de Sitter space produce a curvature-induced mass and work to restore the broken Z_2 symmetry.Comment: 14 pages, 3 figures, section 2 revised, discussion in section 4 changed, results not change

Constraints on mode couplings and modulation of the CMB with WMAP data

We investigate a possible asymmetry in the statistical properties of the cosmic microwave background temperature field and to do so we construct an estimator aiming at detecting a dipolar modulation. Such a modulation is found to induce correlations between multipoles with $\Delta\ell=1$. Applying this estimator, to the V and W bands of the WMAP data, we found a significant detection in the V band. We argue however that foregrounds and in particular point sources are the origin of this signal.Comment: 14 pages, 14 figure

Structural and photoelectric properties of tensile strained BiFeO3

An in-depth structural study of a 23-nm-thick BiFeO3 film grown on orthorhombic NdScO3(110)O substrates demonstrates the presence of a mixed phases. Atomic resolution scanning transmission electron microscopy measurements reveal an out-of-plane stripe domain structure typical of rhombohedral BiFeO3 films but with a polarization component along pseudocubic ⟨100⟩PC or canted from the ⟨111⟩PC towards the in-plane direction. Photovoltaic measurements display an anomalous modulation of the open circuit voltage as temperature is decreased that is attributed to a structural change associated with a transition to a single structural phase

High order correlation functions for self interacting scalar field in de Sitter space

We present the expressions of the three- and four-point correlation functions of a self interacting light scalar field in a de Sitter spacetime at tree order respectively for a cubic and a quartic potential. Exact expressions are derived and their limiting behaviour on super-horizon scales are presented. Their essential features are shown to be similar to those obtained in a classical approach.Comment: 8 pages, 4 figure

Chenier Morphodynamics on the Amazon-Influenced Coast of Suriname, South America: Implications for Beach Ecosystem Services

The 350-km long coast of Suriname, South America, is part of a unique system in the world characterized by large-scale mud supply from the Amazon and exposed to Atlantic waves. Large banks migrate alongshore from the Amazon to the Orinoco delta, separated by ‘inter-bank’ zones. Banks dissipate waves, partially weld onshore, and are colonized by mangroves, whereas waves in inter-bank areas cause shoreline erosion, mitigated where rare cheniers develop. Cheniers assure coastal protection and recreational and ecosystem services, notably providing nesting sites for marine turtles. Cheniers are also under pressure from sand mining. In order to gain a better understanding of how these cheniers form and evolve, a study was conducted on Braamspunt beach, a major turtle-nesting chenier in Suriname constructed from sand supplied by the Maroni River. Satellite images between 1987 and 2018 show a reduction of the alongshore extent of the chenier, following sand supply cut-off from the Maroni by a mud bank migrating westward towards the mouth of the Suriname River, exacerbated by mud-blanketing of sand. Commercial sand mining has further affected the beach, but mined volumes are not known. Field surveys (high-resolution topography, drone photogrammetry, wave measurements) conducted in February, 2016 highlight two chenier types depending on sand availability, transport and wave reworking: a high-tide reflective/low-tide dissipative and longshore transport-dominated type 1 exhibiting berm scarping, and a low, overwash-dominated type 2. As the mud-bank’s leading edge impinges on the inter-bank trailing edge, sand sequestering by mud and storage in type 2 washovers entail less available sand downdrift. Type 1 lost over 4200 m3 of sand in just 3–4 days. An increasingly deficient budget induces progressive change to type 2, morphodynamically better adapted to diminution of available sand, and epitomizing chenier fragmentation and isolation within the muddy Guianas coastal plain. By affecting the morphology and sand budget of Braamspunt, these changes lower opportunities for turtle-nesting. Further reduction of the length of exposed chenier is apparently halted near the Suriname River mouth where mud is liquefied by the outflowing river and tidal jet, but the continued existence of this preserved beach could be endangered by sand mining

Possible Enhancement of High Frequency Gravitational Waves

We study the tensor perturbations in a class of non-local, purely gravitational models which naturally end inflation in a distinctive phase of oscillations with slight and short violations of the weak energy condition. We find the usual generic form for the tensor power spectrum. The presence of the oscillatory phase leads to an enhancement of gravitational waves with frequencies somewhat less than 10^{10} Hz.Comment: 27 pages, 11 figures, LaTeX.2

Stress Tensor Correlators in the Schwinger-Keldysh Formalism

We express stress tensor correlators using the Schwinger-Keldysh formalism. The absence of off-diagonal counterterms in this formalism ensures that the +- and -+ correlators are free of primitive divergences. We use dimensional regularization in position space to explicitly check this at one loop order for a massless scalar on a flat space background. We use the same procedure to show that the ++ correlator contains the divergences first computed by `t Hooft and Veltman for the scalar contribution to the graviton self-energy.Comment: 14 pages, LaTeX 2epsilon, no figures, revised for publicatio

K-essential Phantom Energy: Doomsday around the Corner? Revisited

We generalize some of those results reported by Gonz\'{a}lez-D\'{i}az by further tuning the parameter ($\beta$) which is closely related to the canonical kinetic term in $k$-essence formalism. The scale factor $a(t)$ could be negative and decreasing within a specific range of $\beta$ ($\equiv -1/\omega$, $\omega$ : the equation-of-state parameter) during the initial evolutional period.Comment: 1 Figure, 6 page

PD effluent specimen collection: your questions answered

When a patient on peritoneal dialysis (PD) presents with suspected PD-related peritonitis (e.g. cloudy PD fluid and abdominal pain), one of the most important initial aspects of management is for the nephrology nurse/home dialysis nurse to collect PD effluent specimens for white blood cells count, Gram stain, culture and sensitivity for inspection and to send for laboratory testing before antibiotics are started. A review by seven members of the International Society for Peritoneal Dialysis (ISPD) Nursing Committee of all 133 questions posted to the ISPD website ‘Questions about PD’ over the last 4 years (January 2018–December 2021), revealed 97 posted by nephrology nurses from around the world. Of these 97 questions, 10 were noted to be related to best practices for PD effluent specimen collection. For our review, we focused on these 10 questions along with their responses by the members of the ISPD ‘Ask The Experts Team’, whereby existing best practice recommendations were considered, if available, relevant literature was cited and differences in international practice discussed. We revised the original responses for clarity and updated the references. We found that these 10 questions were quite varied but could be organised into four categories: how to collect PD effluent safely; how to proceed with PD effluent collection; how to collect PD effluent for assessment; and how to proceed with follow-up PD effluent collection after intraperitoneal antibiotics have been started. In general, we found that there was limited evidence in the PD literature to answer several of these 10 questions posted to the ISPD website ‘Questions about PD’ by nephrology nurses from around the world on this important clinical topic of best practices for PD effluent specimen collection. Some of these questions were also not addressed in the latest ISPD Peritonitis Guidelines. Moreover, when polling members of our ISPD Nursing Committee we found when answering a few of these questions, nursing practice varied within and among countries. We encourage PD nurses to conduct their own research on this important topic, focusing on areas where research evidence is lacking