149 research outputs found
VALUE ADDED TAX IN THE ECONOMIC CRISIS CONTEXT
This article tries to present the major aspects concerning the value added tax in the context of economic crisis in European Union countries and Romania. The paper realizes an analysis of the impact of economic crises on VAT in the European space underlining the current situation when the revenues from VAT represent a valuable source of financing the public expenditures. In Romania the economic crises has led to increasing o f VAT rate from 19% to 24%. This measure is an important fiscal measure for the state budget and this study tries to reflect the impact of this VAT rate increase on the public revenues and consumption.value added tax, economic crises, tax revenues
Precision cosmology from the clustering of large-scale structures
Cosmology is going through an exciting period characterized by increasingly large and diverse surveys of the Universe. The resulting datasets contain both cosmological and astrophysical information, and provide many different perspectives on the components of the Universe and its evolution. Despite this wealth of data, there are still many open questions and unknowns. These
vary from broad questions about the nature of dark energy and dark matter, to more concrete ones, such as how fast exactly is the Universe expanding. In this thesis, we will focus on spectroscopic surveys of the large-scale structure (LSS) in the Universe, and how they are used to study these
problems.
We begin in Chapters 1-4 with an introduction of modern cosmology, focusing on the topics relevant to LSS surveys and the analysis tools used to extract cosmological information from these datasets. After that, in Chapter 5 we use the latest baryon acoustic oscillation (BAO) measurements and baryon density constraints based on big bang nucleosynthesis (BBN) to measure the expansion rate of the Universe, through the Hubble constant. This is an independent measurement that contributes to the ongoing Hubble tension debate. In Chapter 6, we perform for the first time a Bayesian analysis of the Lyman-α (Lyα) forest correlation functions in order to measure BAO. Finally, in Chapter 7 we study the possibility of an analysis of the full shape of the Lyα forest correlation functions. This would expand on BAO analyses by providing cosmological information from a broader range of scales. The next generation of cosmological surveys is just starting with
the Dark Energy Spectroscopic Instrument (DESI). Throughout this thesis, we performed multiple studies that are relevant for future cosmological analyses with DESI. These analyses will advance our physical understanding of the Universe by precisely mapping its evolution to higher redshifts than ever before
The impact of economic crisis on the fiscal revenues
This paper tries to evaluate the situation of the fiscal revenues in Romania in the context of economic and financial crisis, because the fiscal revenues are the major source of financing the public expenditure. The evolution of the level of fiscal revenue is very important because maintain the budget equilibrium. The article reveals the major trends of the fiscal revenues after EU enlargement and in the actual context of economic crisis and the impact on the budget deficit and the public debt. The state intervention in revive of the economy has to be financed through the budget, and this means a higher budget deficit. The proper solution in this condition for assuring the financial stability of the economy it was an external borrow from IMF.fiscal revenues, budget deficit, public debt
THE IMPACT OF ECONOMIC CRISIS ON THE FISCAL REVENUES
This paper tries to evaluate the situation of the fiscal revenues in Romania in the context of economic and financial crisis, because the fiscal revenues are the major source of financing the public expenditure. The evolution of the level of fiscal revenufiscal revenues, budget deficit, public debt
Bayesian methods for fitting Baryon Acoustic Oscillations in the Lyman-α forest
We study and compare fitting methods for the Lyman-α (Lyα) forest 3D correlation function. We use the nested sampler PolyChord and the community code picca to perform a Bayesian analysis which we compare with previous frequentist analyses. By studying synthetic correlation functions, we find that the frequentist profile likelihood produces results in good agreement with a full Bayesian analysis. On the other hand, Maximum Likelihood Estimation with the Gaussian approximation for the uncertainties is inadequate for current data sets. We compute for the first time the full posterior distribution from the Lyα forest correlation functions measured by the extended Baryon Oscillation Spectroscopic Survey (eBOSS). We highlight the benefits of sampling the full posterior distribution by expanding the baseline analysis to better understand the contamination by Damped Lyα systems (DLAs). We make our improvements and results publicly available as part of the picca package
Baryon Acoustic Oscillations and the Hubble Constant: Past, Present and Future
We investigate constraints on the Hubble constant () using Baryon
Acoustic Oscillations (BAO) and baryon density measurements from Big Bang
Nucleosynthesis (BBN). We start by investigating the tension between galaxy BAO
measurements and those using the Lyman- forest, within a Bayesian
framework. Using the latest results from eBOSS DR14 we find that the
probability of this tension being statistical is assuming flat
CDM. We measure km s Mpc, with a weak
dependence on the BBN prior used, in agreement with results from Planck Cosmic
Microwave Background (CMB) results and in strong tension with distance ladder
results. Finally, we forecast the future of BAO BBN measurements of ,
using the Dark Energy Spectroscopic Instrument (DESI). We find that the choice
of BBN prior will have a significant impact when considering future BAO
measurements from DESI.Comment: 14 pages, 3 figure
Cosmology beyond BAO from the 3D distribution of the Lyman-α forest
We propose a new method for fitting the full-shape of the Lyman-α (Ly α) forest 3D correlation function in order to measure the Alcock-Paczynski (AP) effect. Our method preserves the robustness of baryon acoustic oscillations (BAO) analyses, while also providing extra cosmological information from a broader range of scales. We compute idealized forecasts for the Dark Energy Spectroscopic Instrument (DESI) using the Ly α autocorrelation and its cross-correlation with quasars, and show how this type of analysis improves cosmological constraints. The DESI Ly α BAO analysis is expected to measure H(zeff)rd and DM(zeff)/rd with a precision of ∼0.9 per cent, where H is the Hubble parameter, rd is the comoving BAO scale, DM is the comoving angular diameter distance, and the effective redshift of the measurement is zeff ≃ 2.3. By fitting the AP parameter from the full shape of the two correlations, we show that we can obtain a precision of ∼0.5−0.6 per cent on each of H(zeff)rd and DM(zeff)/rd. Furthermore, we show that a joint full-shape analysis of the Ly α auto and cross-correlation with quasars can measure the linear growth rate times the amplitude of matter fluctuations in spheres of 8 h−1Mpc, fσ8(zeff). Such an analysis could provide the first ever measurement of fσ8(zeff) at redshift zeff > 2. By combining this with the quasar autocorrelation in a joint analysis of the three high-redshift two-point correlation functions, we show that DESI could be able to measure fσ8(zeff ≃ 2.3) with a precision of 5−12 per cent, depending on the smallest scale fitted
Optimal data compression for Lyman- forest cosmology
The Lyman- (Ly) three-dimensional correlation functions have
been widely used to perform cosmological inference using the baryon acoustic
oscillation (BAO) scale. While the traditional inference approach employs a
data vector with several thousand data points, we apply near-maximal score
compression down to tens of compressed data elements. We show that carefully
constructed additional data beyond those linked to each inferred model
parameter are required to preserve meaningful goodness-of-fit tests that guard
against unknown systematics, and to avoid information loss due to non-linear
parameter dependencies. We demonstrate, on suites of realistic mocks and DR16
data from the Extended Baryon Oscillation Spectroscopic Survey, that our
compression framework is lossless and unbiased, yielding a posterior that is
indistinguishable from that of the traditional analysis. As a showcase, we
investigate the impact of a covariance matrix estimated from a limited number
of mocks, which is only well-conditioned in compressed space.Comment: Submitted to MNRA
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