On the initial conditions of scalar and tensor fluctuations in f(R,ϕ)f(R,\phi) gravity

We have considered the perturbation equations governing the growth of fluctuations in generalized scalar tensor theory during inflation. we have found that the scalar metric perturbations at very early times are negligible compared with the scalar field perturbation, just like general relativity. At sufficiently early times, when $q/a\gg H$, we have obtained the metric and scalar field perturbation in the form of WKB solutions up to an undetermined coefficient. Then we have quantized the scalar fluctuations and expanded the metric and the scalar field perturbations with the help of annihilation and creation operators of the scalar field perturbation. The standard commutation relations of annihilation and creation operators fix the unknown coefficient. Going over to the gauge invariant quantities which are conserved beyond the horizon, we have obtained the initial condition of the generalized Mukhanov-Sasaki equation. And a similar procedure is performed for the case of tensor metric perturbation.Comment: 11 page

Bohmian Quantum Gravity in the Linear Field Approximation

In this paper we have applied Bohmian quantum theory to the linear field approximation of gravity and present a self--consistent quantum gravity theory in the linear field approximation. The theory is then applied to some specific problems, the Newtonian limit, and the static spherically symmetric solution. Some observable effects of the theory are investigated

Effectiveness Of Economic Sanctions: Empirical Research Revisited

This paper reexamines economic sanctions research and identifies explanatory variables used by many previous theoretical and empirical research studies on the effectiveness of voluntary and non-voluntary economic sanctions since World War I. A normative legal, political, and economic methodology is used to measure effectiveness of economic sanctions as a random walk process.  The paper concludes that choosing a target and imposing economic sanctions is a random process that occurs when a sender is faced with a real or perceived threat.  Sanctions are imposed as an alternative to inaction or going to war.  The theory and research on effectiveness of sanctions has been a mere exercise in running regressions on a series of random numbers and do not shed any light to guide policymaking

Trans-Planckian Effect in f(R)f(R) Cosmology

Apart from the assumption that the inflation started at an infinite time in the past, the more realistic initial state of the quantum fluctuations is described by a mixed quantum state imposed at a finite value of the initial time. One of the most important non-trivial vacua is the $\alpha$-vacuum, which is specified by a momentum cutoff $\Lambda$ \cite{Danielsson:2002kx}. As a consequence, the initial condition is imposed at different initial times for the different $k$-modes. This modifies the amplitude of the quantum fluctuations, and thus the corresponding power spectra. In this paper, we consider the imprint of the $\alpha$-vacuum state on the power spectrum of scalar perturbations in a generic $f(R)$ gravity by assuming an ultraviolet cutoff $\Lambda$. As a specific model, we consider the Starobinsky model and find the trans-Planckian power spectrum. We find that the leading order corrections to the scalar power spectra in $f(R)$ gravity have an oscillatory behavior as in general relativity \cite{Lim}, and furthermore, the results are in sufficient agreement with the $\Lambda$CDM model.Comment: 21 pages, 5 figures, 1 table

Developmental Relationship Programs: An Empirical Study Of The Impact Of Peer-Mentoring Programs

This paper provides an empirical analysis of the impact and effectiveness of developmental relationships provided through academic intervention programs at a medium-size master’s level public university in the Northeastern United States.  The programs’ curriculum follows the Model of Strategic Learning’s four pillars of learning and is administered to students with diverse interventional needs. This paper presents a brief review of the literature about effective developmental relationship programs (mentoring and coaching) in higher education.  Then, Ordinary Least Squares regressions, as well as paired samples t-tests, are used to test the impact of programs offered through developmental relationships to students with varying academic deficiencies.  The immediate, as well as longer-term, impact and sustainability of students’ enhanced performance is statistically examined.  The paper concludes that students who fully take advantage of developmental relationships benefit the most and sustain their higher level of performance beyond the immediate post one-time intervention period.  However, in the absence of additional intervention, the academic performance gains seem to subside and flatten out

Non-minimal Quintessence: Dynamics and coincidence problem

Brans--Dicke scalar--tensor theory provides a conformally coupling of the scalar field with gravity in Einstein's frame. This model is equivalent to an interacting quintessence in which dark matter is coupled to dark energy. This provides a natural mechanism to alleviate the coincidence problem. We investigate the dynamics of this model and show that it leads to comparable dark energy and dark matter densities today.Comment: To appear in Pramana Journal of Physics, 201

Study on population increase parameters of greenbug, Schizaphis graminum (Hem.: Aphididae), on common wheat varieties in Varamin region, Iran

The biology of greenbug, Schizaphis graminum Rondani, one of the most important pests of cereals in Varamin region of Iran, was studied in laboratory at 20 ± 1ËC, 60-70% R.H. and a photoperiod of 16: 8 (L: D) hours. The experiment was carried out by rearing aphids on the leaves of six common wheat varieties including: Mahdavi, Kavir, Niknezhad, Azadi, Tabasi, and Ghods using leaf cages. The nymphal development time, mortality, longevity and adult fertility of the aphid were recorded daily. The intrinsic rate of increase (rm), finite rate of increase (λ), and doubling time (DT) parameters were calculated. Results revealed that nymphal mortality rate was very low resembling that on sensitive wheat varieties. The aphid had relatively high longevity and short nymphal development time on all mentioned wheat varieties. The lowest aphid fertility rate was obtained on Kavir comparing to the fertility yielded on Mahdavi and Tabasi that was significantly higher (P < 0.01). Estimation of the intrinsic rate of increase revealed that the wheat varieties studied were susceptible to aphid, for the reason that the aphid population increased by constant exponential rate of 0.252-0.310 female/female/day. This showed high population increase potential at suitable conditions in the absence of natural enemies. Results proved that the Niknezhad, Tabasi and Ghods were the most suitable wheat varieties for rearing the aphid. The lowest rate of fertility, intrinsic rate of increase, and finite rate of increase, and the longest doubling time of aphid population were observed on Kavir, due to lower fecundity and longer nymphal development period. Therefore, the aphid population increase potential on Kavir was lower than that on the other varieties and so, expansion of sowing Kavir in Varamin region most probably may not result in aphid population increase

Cosmological spacetimes balanced by a scale covariant scalar field

A scale invariant, Weyl geometric, Lagrangian approach to cosmology is explored, with a a scalar field phi of (scale) weight -1 as a crucial ingredient besides classical matter \cite{Tann:Diss,Drechsler:Higgs}. For a particularly simple class of Weyl geometric models (called {\em Einstein-Weyl universes}) the Klein-Gordon equation for phi is explicitly solvable. In this case the energy-stress tensor of the scalar field consists of a vacuum-like term Lambda g_{mu nu} with variable coefficient Lambda, depending on matter density and spacetime geometry, and of a dark matter like term. Under certain assumptions on parameter constellations, the energy-stress tensor of the phi-field keeps Einstein-Weyl universes in locally stable equilibrium. A short glance at observational data, in particular supernovae Ia (Riess ea 2007), shows interesting empirical properties of these models.Comment: 28 pages, 1 figure, accepted by Foundations of Physic

Kinematic Self-Similar Plane Symmetric Solutions

This paper is devoted to classify the most general plane symmetric spacetimes according to kinematic self-similar perfect fluid and dust solutions. We provide a classification of the kinematic self-similarity of the first, second, zeroth and infinite kinds with different equations of state, where the self-similar vector is not only tilted but also orthogonal and parallel to the fluid flow. This scheme of classification yields twenty four plane symmetric kinematic self-similar solutions. Some of these solutions turn out to be vacuum. These solutions can be matched with the already classified plane symmetric solutions under particular coordinate transformations. As a result, these reduce to sixteen independent plane symmetric kinematic self-similar solutions.Comment: 29 pages, accepted for publication in Classical Quantum Gravit