Modified gravity and the stability of de Sitter space

Within the context of modified gravity and dark energy scenarios of the accelerating universe, we study the stability of de Sitter space with respect to inhomogeneous perturbations using a gauge-independent formalism. In modified gravity the stability condition is exactly the same that one obtains from a homogeneous perturbation analysis, while the stability condition in scalar-tensor gravity is more restrictive.Comment: 5 pages, no figures, RevTeX, to appear in Phys. Rev. D (Rapid Communications section

Education, Skills and Labor Market Outcomes: Results from Large-Scale Adult Skills Surveys in Urban Areas in 12 Countries

In recent years, skills development has become a priority among developed and developing countries alike. The World Bank Group, in its quest to end extreme poverty and promote shared prosperity, has joined efforts with countries and multilateral development partners to ensure that individuals have access to quality education and training opportunities and that employers can find the skills they need to operate. The skills towards employability and productivity (STEP) skills measurement program is part of the World Bank's portfolio of analytical products on skills. The STEP program consists of two survey instruments that collect information on the supply and demand for skills in urban areas: a household survey and an employer survey. STEP has been implemented in waves, the first surveys being implemented in seven countries in 2012 (Bolivia, Colombia, Ghana, Lao Peoples Democratic Republic (PDR), Ukraine, Vietnam, and the Yunnan Province in China), and the second in five countries in 2013 (Armenia, Azerbaijan, Georgia, Kenya, and Macedonia, Former Yugoslav Republic of (FYR)). The data presented in this publication correspond to these countries. It illustrates the similarities and differences among groups that have completed different education levels on a wide range of issues and outcomes. Section one analyzes the trajectory of skills acquisition: participation in early childhood education programs, educational attainment by gender, and participation in training and apprenticeship programs. Section two explores background conditions associated with educational attainment, including the socioeconomic status of survey respondents at age 15, the educational attainment of their parents, their households' asset levels, their health (as expressed by the presence of chronic illness), and their overall satisfaction with life. Section three covers cognitive skills: writing, numeracy, and reading (which is also evaluated through a direct reading assessment). Section four covers job-relevant skills, which are task-specific and which respondents possess or use on the job; and section five covers socio-emotional skills, using established metrics to measure personality and behavior. Section six covers the status of survey respondents in the labor market: whether they are employed, unemployed, or inactive

Towards Dead Time Inclusion in Neuronal Modeling

A mathematical description of the refractoriness period in neuronal diffusion modeling is given and its moments are explicitly obtained in a form that is suitable for quantitative evaluations. Then, for the Wiener, Ornstein-Uhlenbeck and Feller neuronal models, an analysis of the features exhibited by the mean and variance of the first passage time and of refractoriness period is performed.Comment: 12 pages, 1 figur

Negative energy and stability in scalar-tensor gravity

Linearized gravitational waves in Brans-Dicke and scalar-tensor theories carry negative energy. A gauge-invariant analysis shows that the background Minkowski space is stable at the classical level with respect to linear scalar and tensor inhomogeneous perturbations.Comment: 9 pages, latex, to appear in Phys. Rev.

Matter instability in modified gravity

The Dolgov-Kawasaki instability discovered in the matter sector of the modified gravity scenario incorporating a 1/R correction to Einstein gravity is studied in general f(R) theories. A stability condition is found in the metric version of these theories to help ruling out models that are unviable from the theoretical point of view.Comment: 4 pages, revtex, to appear in Phys. Rev. D. In the revised version, an error concerning the Palatini version of these theories has been corrected and the references update

Automatic Patient Modeling for Hyperthermia Treatment Planning of Head and Neck Cancer

Head and neck (H&N) cancer is the term used to describe a wide range of malig- nant tumors originating in the upper airways and swallowing tracts. In 2012, this disease accounted for approximately 5% of all cancers worldwide, with 680,000 new cases diagnosed and 370,000 recorded deaths, resulting as the seventh most common cancer worldwide. The H&N region is often divided in subregions containing dfferent tumor sites, as depicted in Figure 1.1: the oral cavity, paranasal sinus and nasal cavity, salivary glands, nasopharynx, oropharynx, hypopharynx (bot- tom part of the throat) and larynx. Tumors in the eyes, brain and skin are generally not considered H&N cancer

The impact of the auditee’s industry on type II audit misclassifications

Abstract. The purpose of this thesis is to contribute to the literature concerning Going Concern opinions and their relative misclassifications. Firms prepare their financial statements under the Going Concern assumption, under which the firm is expected to continue operating during the normal course of business without facing bankruptcy risks. Auditors are required to deliver an opinion concerning the appropriateness of the Going Concern assumption. Past literature refers to Type II audit misclassifications when discussing those misclassifications occurring when auditors fail to modify an audit report for Going Concern, and the client subsequently files for bankruptcy within one year from the issuance of the report. Type II audit misclassifications are often seen as “audit failures” by regulators and investors, as auditors failed to warn about the Going Concern issues of their clients, and the same also have consequences for auditors, who face potential litigation fees and reputation loss in case they do not render a GCO to a firm that subsequently fails. The focus of this thesis is for this reason on Type II audit misclassifications. Past research has broadly studied factors influencing GCO issuances and their relative misclassifications (e.g., client size, audit tenure, auditor dependency). This study explores whether the industry the auditee belongs to can be a potential determinant of increased likelihood of Type II misclassifications. A distinction between complex industries (e.g., Construction, Financial services, IT services) and non-complex industries is made following a previous line of research and binary logistic regression models are used to analyze the association between the industries and the likelihood of Type II audit misclassifications. The hypotheses are that an increased likelihood of Type II audit misclassifications might be observed in complex industries and, specifically, in the IT services industry, as these industries are more unpredictable due to revenue-recognition and measurement processes that are heavily influenced by accruals and longer-than-average operating cycles. The results show that the likelihood of auditors failing to issue a GCO when needed is higher when the client belongs to a complex industry and if it belongs to the IT services industry alone. These findings might be helpful for the decision-making process of those investors who positively weigh a clean audit report of a firm for their investment decisions. Further, this increased likelihood of Type II audit misclassifications in the aforementioned industries might serve as groundwork for future research and for practitioners, as additional audit procedures and audit requirements might be needed when clients belong to complex industries

Cosmological implications of an evolutionary quantum gravity

The cosmological implications of an evolutionary quantum gravity are analyzed in the context of a generic inhomogeneous model. The Schr\"{o}dinger problem is formulated and solved in the presence of a scalar field, an ultrarelativistic matter and a perfect gas regarded as the dust-clock. Considering the actual phenomenology, it is shown how the evolutionary approach overlaps the Wheeler-DeWitt one.Comment: 4 pages; to appear in the proceedings of the II Stueckelberg Workshop, Int.J.Mod.Phys.A, references adde

de Sitter space and the equivalence between f(R) and scalar-tensor gravity

It is shown that, when f'' is non-vanishing, metric f(R) gravity is completely equivalent to a scalar-tensor theory (with zero Brans-Dicke parameter) with respect to perturbations of de Sitter space, contrary to previous expectations. Moreover, the stability conditions of de Sitter space with respect to homogeneous and inhomogeneous perturbations coincide in most scalar-tensor theories, as is the case in metric f(R) gravity.Comment: 4 pages, revtex, to appear in Phys. Rev. D. Revised version contains additional and updated reference

Transforming nonlocality into frequency dependence: a shortcut to spectroscopy

Measurable spectra are theoretically very often derived from complicated many-body Green's functions. In this way, one calculates much more information than actually needed. Here we present an in principle exact approach to construct effective potentials and kernels for the direct calculation of electronic spectra. In particular, the potential that yields the spectral function needed to describe photoemission turns out to be dynamical but {\it local} and {\it real}. As example we illustrate this ``photoemission potential'' for sodium and aluminium, modelled as homogeneous electron gas, and discuss in particular its frequency dependence stemming from the nonlocality of the corresponding self-energy. We also show that our approach leads to a very short derivation of a kernel that is known to well describe absorption and energy-loss spectra of a wide range of materials