9,104 research outputs found
Exit from Inflation with a First-Order Phase Transition and a Gravitational Wave Blast
In double-field inflation, which exploits two scalar fields, one of the
fields rolls slowly during inflation whereas the other field is trapped in a
meta-stable vacuum. The nucleation rate from the false vacuum to the true one
becomes substantial enough that triggers a first order phase transition and
ends inflation. We revisit the question of first order phase transition in an
"extended" model of hybrid inflation, realizing the double-field inflationary
scenario, and correctly identify the parameter space that leads to a first
order phase transition at the end of inflation. We compute the gravitational
wave profile which is generated during this first order phase transition.
Assuming instant reheating, the peak frequency falls in the GHz to GHz
frequency band and the amplitude varies in the range , depending on the value of the
cosmological constant in the false vacuum. The signature could be observed by
the planned Chongqing high frequency gravitational probe. For a narrow band of
vacuum energies, the first order phase transition can happen after the end of
inflation via the violation of slow-roll, with a peak frequency that varies
from THz to THz. For smaller values of cosmological constant, even
though inflation can end via slow-roll violation, the universe gets trapped in
a false vacuum whose energy drives a second phase of eternal inflation. This
range of vacuum energies do not lead to viable inflationary models, unless the
value of the cosmological constant is compatible with the observed value,
eV.Comment: v1: 15 pages, 8 Figures; v2: typos corrected;v3: matched the PLB
versio
Growth, profitability and savings of quoted public limited companies 1964-70
This study by extending an earlier study by Haq and Baqai (1967) on growth, profitability and savings of companies quoted on the Karachi Stock Exchange analysis movements of these key variables and identifies key factors and events which explain them for the entire period of the 1960s
Rescuing Single Field Inflation from the Swampland
The difficulty of building metastable vacua in string theory has led some to
conjecture that, in the string theory landscape, potentials satisfy
. This condition, which is
supported by different explicit constructions, suggests that the EFTs which
lead to metastable de-Sitter vacua belong to what is dubbed as swampland. This
condition endangers the paradigm of single field inflation. In this paper, we
show how scalar excited initial states cannot rescue single field inflation
from the swampland, as they produce large local scalar non-gaussianity, which
is in conflict with the Planck upper bound. Instead, we demonstrate that one
can salvage single field inflation using excited initial states for tensor
perturbations, which in this case produce only large flattened non-gaussianity
in the tensor bispectrum. We comment on the possible methods one can prepare
such excited initial conditions for the tensor perturbations.Comment: v1: 8 pages double columns, no figures; v2: references added, matched
the PLB versio
Development of D-Statcom in hardware in the loop system for voltage SAG mitigation
The problem of power quality (PQ) is of utmost concern today. The widespread use of
electronic equipment such as adjustable speed drive (ASD), programmable logic
controller (PLC), information technology equipment in power electronics applications
such as energy-efficient lighting brings about a complete change in the nature of the
electrical load. These loads are simultaneously major causes and major victims due to
power quality problems. The most common types of power quality problems are
voltage drops. The main causes of the voltage drop are due to a short circuit in the
system, a switching operation, the starting of the large motor, a sudden increase in line
loads, electrical fault on utility power lines caused by an animal, trees or other objects
in contact with power lines. Therefore, this project is about to develop a Distributed
Static Compensator (D-STATCOM) for voltage sag mitigation in hardware in the loop
(HIL) with phase shift control technique for maintaining the bus bar-load voltage. It is
because the intermittent switching of heavy loads results in voltage sag in the
distribution line. The distribution line 400V and the D-STATCOM are modeled using
MATLAB-SIMULINK software. In this work, the 6-pulse D-STATCOM
configuration with IGBT has been designed. The HIL was develop using the low-cost
microcontrollers which are the Arduino Mega 2560 and Raspberry Pi Type B2 with
high accuracy response for high speed communication on mimic the real time
response. In order to run the D-STATCOM in HIL and test the mitigation of sag,
software design is first carried out to illustrate the use of D-STATCOM in mitigating
voltage sag in a distribution line. The simulation results for software design proved
that the D-STATCOM is capable of mitigating voltage sag as well as improving power
quality of a system and the voltage sag 20% was corrected from 200V to normal
voltage 245V. The D-STATCOM that has been modeled successfully and able to
mitigate the voltage sag by using D-STATCOM in (HIL). At last the results have been
analyzed and compared with the results which get in software
The impact of socio-economic factors on small business success
ļ»æSmall enterprises play a vital role in economic development as they can provide the economy with efficiency,
innovation, competition and employment. Entrepreneurs are responsible for the success of their businesses and have
to face up with definite challenges in doing so. To know what constitute critical determinants of small business
success data were collected from 60 randomly selected respondents in the Dera Ismail Khan district, Khyber
Pakhtunkhawa, Pakistan, who were administered with structured questionnaires. Regression analyses of the findings
showed the positive and significant impact factors of investment, entrepreneurial experience, business profile and culture with R2=0.638 and F= 11.222. The provision of ample opportunities to develop skills for business
enhancement is suggested as the rational way forward
The impact of teacher wages on the performance of students: evidence from PISA
Teacher profile and characteristics are not weightless because student achievements are heavily teacher dependent. In this detailed and in-depth research, the impact of teacher wages on studentsā achievement was assessed in different ways by using different measuring sticks; starting salary, salary after 15 year of experience, salary per hour of net teaching time and salary ratio to GDP per capita and by using country scores, of 15 year old pupil enrolled in lower secondary school, in OECD member countries. For this propose PISA 2000, 2003 and 2006 survey data of studentsā scores were used. The independent variables āwagesā was regressed on the dependent variable āstudents total mean country scoreā. The results of these analyses gave an indication that there is a positive impact of teacher wages on studentsā performance.characteristics, profile, qualities, impact, teacher, learning, achievements, performance, student, salary, wages, gender, PISA, OECD
Solving Pakistan's Poverty Puzzle: Whom Should We Believe? What Should We Do?
Understanding Pakistanās economic performance has never been easy. Its capacity to generate impressive rates of economic growth in the 1960s and 1980s with low levels of savings, investment and very poor human development indicators confounded its critics. Indeed during the overall period 1960ā1990 Pakistanās growth performance would place it in the top ten countries in the world. This made an eminent economist Professor Richard Eckaus remark, āPakistan is a puzzle, a miracle of levitation. With one of the lowest domestic savings rate in Asia, its economy has performed quite creditably. Since we do not believe in miracles, we have to wonder whether the capital inflows that have sustained this growth will lastā.1 Unfortunately they did not. Pakistanās growth rate in the 1990s came tumbling down, the result of a number of factors of which a decline in capital inflows also played a significant part. If Pakistanās growth performance has been in part difficult to justify then understanding or explaining changes and wide fluctuations in its poverty levels has posed even a more challenging task. Pakistan has witnessed over the last three decades periods of high economic growth, as in the 1960s, accompanied with increasing poverty levels, periods of low economic growth, as in the 1970s, accompanied by reductions in poverty levels, periods of high economic growth leading to a decline in poverty as in the 1980s and periods of low economic growth as in the 1990s accompanied by as we shall see by increasing poverty levels.
International Labor Migration and Its Implications in the APEC Region
This paper identifies some of the key issues confronting the Asia-Pacific member-economies that arise from the discussions in the APEC forum. A brief review of existing labor flows within the APEC regions is presented. A discussion on how globalization and trade liberalization will impact on the international movements of labor in the APEC regions is also included.globalization, trade sector, liberalization, APEC
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