956 research outputs found
Can the level of sustainability impact firms’ credit risk? A study on European firms
Sustainability has become a topic of increasing relevance. This dissertation investigates the
impact of sustainability on the credit risk of European firms over the period of 2005 to 2021,
aiming to answer the research question of whether the level of sustainability can impact firms‘
credit risk. Firms' Total ESG Scores and their corresponding Pillar Scores are used as
sustainability measures for the analysis. To proxy credit risk, S&P ratings, converted into
default probabilities using European transition matrices, are employed, thereby circumventing
the problem of non-equidistant scaling of credit ratings. The final dataset consists of 412
European firms.
The multivariate regression results show that a higher level of sustainability can reduce a firm's
credit risk. However, these results are conditional on the rating category. Only firms with an
investment-grade rating seem to benefit from a higher level of sustainability. Yet the impact of
sustainability on their credit risk is not particularly large. Furthermore, the results of a sectoral
analysis show that sustainability only has an impact on credit risk in certain industry sectors
and that not all firms in the respective industries benefit equally. Finally, a temporal analysis
shows that the impact of sustainability varies over time.A sustentabilidade tem vindo a tornar-se um tema de crescente relevância. Esta dissertação
investiga o impacto da sustentabilidade no risco de crédito das empresas europeias durante o
período de 2005 a 2021, com o objectivo de responder à questão de investigação de saber se o
nível de sustentabilidade tem impacto no risco de crédito das empresas. Para a análise, os Total
ESG Scores das empresas e os correspondentes Pillar Scores são utilizados como medidas de
sustentabilidade. Para representar o risco de crédito, são utilizadas as notações da S&P,
convertidas em probabilidades de incumprimento utilizando matrizes de transição europeias,
contornando assim o problema do escalonamento não equidistante das notações de crédito. O
conjunto final de dados é constituído por 412 empresas europeias.
Os resultados da regressão multivariada mostram que um nível mais elevado de
sustentabilidade pode reduzir o risco de crédito de uma empresa. No entanto, estes resultados
são condicionados pela categoria de notação. Apenas as empresas com uma notação de grau de
investimento parecem beneficiar de um nível mais elevado de sustentabilidade. No entanto, o
impacto da sustentabilidade no seu risco de crédito não é particularmente grande. Além disso,
os resultados de uma análise sectorial mostram que a sustentabilidade só tem impacto no risco
de crédito em determinados sectores industriais e que nem todas as empresas dos respectivos
sectores beneficiam da mesma forma. Por último, uma análise temporal mostra que o impacto
da sustentabilidade varia ao longo do tempo
Testing Hu-Sawicki f(R) gravity with the Effective Field Theory approach
We show how to fully map a specific model of modified gravity into the
Einstein-Boltzmann solver EFTCAMB. This approach consists in few steps and
allows to obtain the cosmological phenomenology of a model with minimal effort.
We discuss all these steps, from the solution of the dynamical equations for
the cosmological background of the model to the use of the mapping relations to
cast the model into the effective field theory language and use the latter to
solve for perturbations. We choose the Hu-Sawicki f(R) model of gravity as our
working example. After solving the background and performing the mapping, we
interface the algorithm with EFTCAMB and take advantage of the effective field
theory framework to integrate the full dynamics of linear perturbations,
returning all quantities needed to accurately compare the model with
observations. We discuss some observational signatures of this model, focusing
on the linear growth of cosmic structures. In particular we present the
behavior of and that, unlike the CDM scenario, are
generally scale dependent in addition to redshift dependent. Finally, we study
the observational implications of the model by comparing its cosmological
predictions to the Planck 2015 data, including CMB lensing, the WiggleZ galaxy
survey and the CFHTLenS weak lensing survey measurements. We find that while
WiggleZ data favor a non-vanishing value of the Hu-Sawicki model parameter,
, and consequently a large value of , CFHTLenS
drags the estimate of back to the CDM limit.Comment: 13 pages, 8 figure
Effective Field Theory of Cosmic Acceleration: constraining dark energy with CMB data
We introduce EFTCAMB/EFTCosmoMC as publicly available patches to the commonly
used CAMB/CosmoMC codes. We briefly describe the structure of the codes, their
applicability and main features. To illustrate the use of these patches, we
obtain constraints on parametrized pure EFT and designer models, both on
CDM and CDM background expansion histories, using data from Planck
temperature and lensing potential spectra, WMAP low- polarization spectra
(WP), and baryon acoustic oscillation (BAO). Upon inspecting theoretical
stability of the models on the given background, we find non-trivial parameter
spaces that we translate into viability priors. We use different combinations
of data sets to show their individual effects on cosmological and model
parameters. Our data analysis results show that, depending on the adopted data
sets, in the CDM background case this viability priors could dominate the
marginalized posterior distributions. Interestingly, with Planck+WP+BAO+lensing
data, in gravity models, we get very strong constraints on the constant
dark energy equation of state, .Comment: 12 pages, 3 figures, 2 tables. Matching version accepted by PRD. The
EFTCAMB/EFTCosmoMC codes are available at:
http://wwwhome.lorentz.leidenuniv.nl/~hu/codes
Effective Field Theory of Cosmic Acceleration: an implementation in CAMB
We implement the effective field theory (EFT) approach to dark energy and
modified gravity in the public Einstein-Boltzmann solver CAMB. The resulting
code, which we dub EFTCAMB, is a powerful and versatile tool that can be used
for several objectives. It can be employed to evolve the full dynamics of
linear scalar perturbations in any given single field dark energy or modified
gravity model, once the latter is mapped into the EFT formalism. It offers a
numerical implementation of EFT as a model-independent framework to test
gravity on cosmological scales. EFTCAMB has a built-in check for the
fulfillment of general stability conditions such as the absence of ghost and
superluminal propagation of perturbations. It handles phantom-divide crossing
models and does not contain any quasi-static approximation, but rather evolves
the full dynamics of perturbations on linear scales. As we will show, the
latter is an important feature in view of the accuracy and scale range of
upcoming surveys. We show the reliability and applicability of our code by
evolving the dynamics of linear perturbations and extracting predictions for
power spectra in several models. In particular we perform a thorough analysis
of f(R) theories, comparing our outputs with those of an existing code for LCDM
backgrounds, and finding an agreement that can reach 0.1% for models with a
Compton wavelength consistent with current cosmological data. We then showcase
the flexibility of our code studying two different scenarios. First we produce
new results for designer f(R) models with a time-varying dark energy equation
of state. Second, we extract predictions for linear observables in some
parametrized EFT models with a phantom-divide crossing equation of state for
dark energy.Comment: 23 pages, 6 figures. Matching version accepted by PRD. Minor changes
in the appendi
Do current cosmological observations rule out all Covariant Galileons?
We revisit the cosmology of Covariant Galileon gravity in view of the most
recent cosmological data sets, including weak lensing. As a higher derivative
theory, Covariant Galileon models do not have a CDM limit and predict
a very different structure formation pattern compared with the standard
CDM scenario. Previous cosmological analyses suggest that this model
is marginally disfavoured, yet can not be completely ruled out. In this work we
use a more recent and extended combination of data, and we allow for more
freedom in the cosmology, by including a massive neutrino sector with three
different mass hierarchies. We use the Planck measurements of Cosmic Microwave
Background temperature and polarization; Baryonic Acoustic Oscillations
measurements by BOSS DR12; local measurements of ; the joint light-curve
analysis supernovae sample; and, for the first time, weak gravitational lensing
from the KiDS collaboration. We find, that in order to provide a reasonable
fit, a non-zero neutrino mass is indeed necessary, but we do not report any
sizable difference among the three neutrino hierarchies. Finally, the
comparison of the Bayesian Evidence to the CDM one shows that in all
the cases considered, Covariant Galileon models are statistically ruled out by
cosmological data.Comment: 8 pages, 5 figures, 2 tables. The Covariant Galileon patch of EFTCAMB
is released in the EFTCAMB developers version - accepted version by PR
Horava Gravity in the Effective Field Theory formalism: from cosmology to observational constraints
We consider Horava gravity within the framework of the effective field theory
(EFT) of dark energy and modified gravity. We work out a complete mapping of
the theory into the EFT language for an action including all the operators
which are relevant for linear perturbations with up to sixth order spatial
derivatives. We then employ an updated version of the EFTCAMB/EFTCosmoMC
package to study the cosmology of the low-energy limit of Horava gravity and
place constraints on its parameters using several cosmological data sets. In
particular we use cosmic microwave background (CMB) temperature-temperature and
lensing power spectra by Planck 2013, WMAP low-l polarization spectra, WiggleZ
galaxy power spectrum, local Hubble measurements, Supernovae data from SNLS,
SDSS and HST and the baryon acoustic oscillations measurements from BOSS, SDSS
and 6dFGS. We get improved upper bounds, with respect to those from Big Bang
Nucleosynthesis, on the deviation of the cosmological gravitational constant
from the local Newtonian one. At the level of the background phenomenology, we
find a relevant rescaling of the Hubble rate at all epoch, which has a strong
impact on the cosmological observables; at the level of perturbations, we
discuss in details all the relevant effects on the observables and find that in
general the quasi-static approximation is not safe to describe the evolution of
perturbations. Overall we find that the effects of the modifications induced by
the low-energy Horava gravity action are quite dramatic and current data place
tight bounds on the theory parameters.Comment: v1: 27 pages, 7 figures. v2: 28 pages, 7 figures. Changes in Figs.
2,3,4,6,7 and Tabs. 1,2. Matches published version in Phys. Dark Uni
A Digital Twin Based Self-Calibration Tool for Fault Prediction of FDM Additive Manufacturing Systems
Among the advantages of introducing digital twins on production systems, there is the ability to identify their eventual
critical state and to enable predictive maintenance policies. The failure of a manufacturing process, in general, can be
anticipated in phase of simulation, if tied up to wrong settings, or in phase of operation, if tied up to environmental
variables. In both cases, knowing the conditions that could cause the failure allows to intervene in a timely and effective
manner. Here a method is proposed to explore the system operating parameters in a systematic way: the system is able to
process signals collected in real time by machine's sensors and to reproduce both the trajectories of the moving parts and
the material deposition process. This also makes possible to predict manufacturing tolerances that will be obtained. On a
FDM Cartesian 3D printer a self-calibration procedure is used to find the maximum torque that can be delivered by the
drives at different speeds in an automatic and repeatable way to find the maximum speed and acceleration at which the
machine can operate safely. Additional accelerometers were installed on the machine to validate the adopted procedure:
tests results demonstrate the effectiveness of the system
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