9,447 research outputs found
Lyth Bound, eternal inflation and future cosmological missions
In this paper we provide a new expression for the variation of the inflaton
field during the horizon crossing epoch in the context of single
field slow roll inflationary models. Such an expression represents a
generalization of the well-know Lyth bound. We also explore the consequences of
a detection of permille order of the tensor-to-scalar ratio amplitude, , as
well as an improvement on the estimation of the scalar spectral index,
and its running , by the upcoming CMB polarization experiments that
will provide plausible constraints on the quantity during the
horizon exit moment. In addition we discuss the relation between the local
variation of the field and the possibilities of an eternal inflation. The
results of the analysis are completely model independent.Comment: 9 pages, 5 figures, some typos correcte
Constraining the general reheating phase in the -attractor inflationary cosmology
In this paper we constrain some aspects of the general postinflationary phase
in the context of superconformal -attractor models of inflation. In
particular, we provide constraints on the duration of the reheating process,
, and on the reheating temperature, , simulating possible and
future results given by the next-generation of cosmological missions. Moreover,
we stress what kinds of equation-of-state parameter, , are favored for
different scenarios. The analysis does not depend on the details of the
reheating phase and it is performed assuming different measurements of the
tensor-to-scalar ratio .Comment: 8 pages, 2 figure
Reconstruction of the physics of Inflation from next generation cosmological experiments
In this work, we study the problem of the reconstruction of the
physics of inflation using current and future cosmological data from cosmic microwave background and gravitational waves experiments. In particular, we focus on the so-called (supergravity) α-attractor models of inflation constraining the shape of the potential
as well as the reheating properties of the these models. Furthermore, we approach the
problem of the reconstruction of the variation of the inflaton field during inflation providing a next order expression in terms of the inflationary variables
Average Rate of Downlink Heterogeneous Cellular Networks over Generalized Fading Channels - A Stochastic Geometry Approach
In this paper, we introduce an analytical framework to compute the average
rate of downlink heterogeneous cellular networks. The framework leverages
recent application of stochastic geometry to other-cell interference modeling
and analysis. The heterogeneous cellular network is modeled as the
superposition of many tiers of Base Stations (BSs) having different transmit
power, density, path-loss exponent, fading parameters and distribution, and
unequal biasing for flexible tier association. A long-term averaged maximum
biased-received-power tier association is considered. The positions of the BSs
in each tier are modeled as points of an independent Poisson Point Process
(PPP). Under these assumptions, we introduce a new analytical methodology to
evaluate the average rate, which avoids the computation of the Coverage
Probability (Pcov) and needs only the Moment Generating Function (MGF) of the
aggregate interference at the probe mobile terminal. The distinguishable
characteristic of our analytical methodology consists in providing a tractable
and numerically efficient framework that is applicable to general fading
distributions, including composite fading channels with small- and mid-scale
fluctuations. In addition, our method can efficiently handle correlated
Log-Normal shadowing with little increase of the computational complexity. The
proposed MGF-based approach needs the computation of either a single or a
two-fold numerical integral, thus reducing the complexity of Pcov-based
frameworks, which require, for general fading distributions, the computation of
a four-fold integral.Comment: Accepted for publication in IEEE Transactions on Communications, to
appea
An atypical case of trigeminal trophic syndrome: a legal medicine perspective in medical responsibility
BACKGROUND: Trigeminal trophic syndrome is a rare complication of peripheral or central damage to the trigeminal nerve characterized by anesthesia, paresthesia and a secondary persistent facial ulceration. METHODS: We describe the case of a 40-year-old woman with previous history of Le Fort I osteotomy for a class III malocclusion who developed trigeminal trophic syndrome. Atypically, the cutaneous symptoms appeared bilaterally and 8âyears after surgery. RESULTS: Differential diagnosis was based on clinical history, tissue biopsy and serologic evaluation. Atypical findings could be linked to the surgical burdens of Le Fort I osteotomy, a procedure characterized by a bilateral incision on the maxillofacial bones with a reasonable probability of causing a bilateral injury of the peripheral branches of the trigeminal nerve. CONCLUSION: Although the long delay between trigeminal trophic syndrome onset and surgery and the absence of adequate medical evidence cannot confirm a link with previous surgery in this case, the increasing number of maxillofacial surgery cases suggests that this complication may be more frequent in the next decades, and thus, involved specialists should be aware of this condition as a possible complication of maxillofacial surgery procedures
Key elements of global inflation
Against the background of large fluctuations in world commodity prices and global growth, combined with ongoing structural changes relating to globalization, this paper examines some of the key factors affecting global inflation. The paper empirically investigates various relative price and structural impacts on global inflation by: estimating a GVAR to examine how oil price shocks feed through to core and headline inflation; calculating the impact of increased imports from low-cost countries on manufacturing import prices; estimating Phillips curves in order to shed light on whether the inflationary process in the OECD countries has changed over time, particularly with respect to the roles of import prices, unit labour costs and the output gap. Overall, the paper finds that there seem to be various significant pressures on global trade prices and labour markets associated with structural factors possibly partly due to globalisation which, in addition to monetary policy, seem to be behind some of the changes in the inflation process over the period examined in this paper.Phillips Curve, inflation, output gap, import prices, unit labour costs, globalisation, monetary policy.
Variable Inflaton Equation of State and Reheating
We explore the consequences of a time-dependent inflaton Equation-of-State
(EoS) parameter in the context of the post-inflationary perturbative Boltzmann
reheating. In particular, we numerically solve the perturbative coupled system
of Boltzmann equations involving the inflaton energy density, the radiation
energy density and the related entropy density and temperature of the produced
particle thermal bath. We exploit reasonable Ans\"atze for the EoS and discuss
the robustness of the Boltzmann system. We also comment on the possible
microscopic origin related to a time dependent inflaton potential, discussing
the consequences on a preheating stage and the related (primordial)
gravitational waves.Comment: 16 pages, 6 figures, minor corrections, references added. Version
conformal to the published on
Location-Verification and Network Planning via Machine Learning Approaches
In-region location verification (IRLV) in wireless networks is the problem of
deciding if user equipment (UE) is transmitting from inside or outside a
specific physical region (e.g., a safe room). The decision process exploits the
features of the channel between the UE and a set of network access points
(APs). We propose a solution based on machine learning (ML) implemented by a
neural network (NN) trained with the channel features (in particular, noisy
attenuation values) collected by the APs for various positions both inside and
outside the specific region. The output is a decision on the UE position
(inside or outside the region). By seeing IRLV as an hypothesis testing
problem, we address the optimal positioning of the APs for minimizing either
the area under the curve (AUC) of the receiver operating characteristic (ROC)
or the cross entropy (CE) between the NN output and ground truth (available
during the training). In order to solve the minimization problem we propose a
twostage particle swarm optimization (PSO) algorithm. We show that for a long
training and a NN with enough neurons the proposed solution achieves the
performance of the Neyman-Pearson (N-P) lemma.Comment: Accepted for Workshop on Machine Learning for Communications, June 07
2019, Avignon, Franc
Modelling sustainable human development in a capability perspective
In this paper we model sustainable human development as intended in Sen's capability approach in a system dynamic framework. Our purpose is to verify the variations over time of some achieved functionings, due to structural dynamics and to variations of the institutional setting and instrumental freedoms (IF Vortex). The model is composed of two sections. The 'Left Side' one points out the 'demand' for functionings in an ideal world situation. The real world one, on the 'Right Side' indicates the 'supply' of functionings that the socio-economic system is able to provide individuals with. The general model, specifically tailored for Italy, can be simulated over desired time horizons: for each time period, we carry out a comparison between ideal world and real world functionings. On the basis of their distances, the model simulates some responses of decision makers. These responses, in turn influenced by institutions and instrumental freedoms, ultimately affect the dynamics of real world functionings, i.e. of sustainable human development.Functionings, Capabilities, Institutions, Instrumental Freedoms, Sustainable Human Development
- âŠ