227 research outputs found
A-VIP: Anonymous Verification and Inference of Positions in Vehicular Networks
MiniconferenceInternational audienceKnowledge of the location of vehicles and tracking of the routes they follow are a requirement for a number of applications, including e-tolling and liability attribution in case of accidents. However, public disclosure of the identity and position of drivers jeopardizes user privacy, and securing the tracking through asymmetric cryptography may have an exceedingly high computational cost. Additionally, there is currently no way an authority can verify the correctness of the position information provided by a potentially misbehaving car. In this paper, we address all of the issues above by introducing A-VIP, a lightweight framework for privacy preserving and tracking of vehicles. A-VIP leverages anonymous position beacons from vehicles, and the cooperation of nearby cars collecting and reporting the beacons they hear. Such information allows an authority to verify the locations announced by vehicles, or to infer the actual ones if needed. We assess the effectiveness of A-VIP through both realistic simulation and testbed implementation results, analyzing also its resilience to adversarial attacks
Long-term perturbations due to a disturbing body in elliptic inclined orbit
In the current study, a double-averaged analytical model including the action
of the perturbing body's inclination is developed to study third-body
perturbations. The disturbing function is expanded in the form of Legendre
polynomials truncated up to the second-order term, and then is averaged over
the periods of the spacecraft and the perturbing body. The efficiency of the
double-averaged algorithm is verified with the full elliptic restricted
three-body model. Comparisons with the previous study for a lunar satellite
perturbed by Earth are presented to measure the effect of the perturbing body's
inclination, and illustrate that the lunar obliquity with the value 6.68\degree
is important for the mean motion of a lunar satellite. The application to the
Mars-Sun system is shown to prove the validity of the double-averaged model. It
can be seen that the algorithm is effective to predict the long-term behavior
of a high-altitude Martian spacecraft perturbed by Sun. The double-averaged
model presented in this paper is also applicable to other celestial systems.Comment: 28 pages, 6 figure
Thermodynamic Properties of the Dimerised and Frustrated S=1/2 Chain
By high temperature series expansion, exact diagonalisation and temperature
density-matrix renormalisation the magnetic susceptibility and the
specific heat of dimerised and frustrated chains are computed.
All three methods yield reliable results, in particular for not too small
temperatures or not too small gaps. The series expansion results are provided
in the form of polynomials allowing very fast and convenient fits in data
analysis using algebraic programmes. We discuss the difficulty to extract more
than two coupling constants from the temperature dependence of .Comment: 14 pages, 13 figures, 4 table
Symmetries of Pairing Correlations in Superconductor-Ferromagnet Nanostructures
Using selection rules imposed by the Pauli principle, we classify pairing
correlations according to their symmetry properties with respect to spin,
momentum, and energy. We observe that inhomogeneity always leads to mixing of
even- and odd-energy pairing components. We investigate the superconducting
pairing correlations present near interfaces between superconductors and
ferromagnets, with focus on clean systems consisting of singlet superconductors
and either weak or half-metallic ferromagnets. Spin-active scattering in the
interface region induces all of the possible symmetry components. In
particular, the long-range equal-spin pairing correlations have odd-frequency
s-wave and even-frequency p-wave components of comparable magnitudes. We also
analyze the Josephson current through a half-metal. We find analytic
expressions and an interesting universality in the temperature dependence of
the critical current in the tunneling limit.Comment: 20 pages, 5 figures, added citations, corrected typo
Elementary Excitations in Dimerized and Frustrated Heisenberg Chains
We present a detailed numerical analysis of the low energy excitation
spectrum of a frustrated and dimerized spin Heisenberg chain. In
particular, we show that in the commensurate spin--Peierls phase the ratio of
the singlet and triplet excitation gap is a universal function which depends on
the frustration parameter only. We identify the conditions for which a second
elementary triplet branch in the excitation spectrum splits from the continuum.
We compare our results with predictions from the continuum limit field theory .
We discuss the relevance of our data in connection with recent experiments on
, , and .Comment: Corrections to the text + 1 new figure, will appear in PRB (august
98
Compatibilidade entre a inoculação de rizóbios e fungicidas aplicados em sementes de feijoeiro-comum
ϒ production in p–Pb collisions at √sNN=8.16 TeV
ϒ production in p–Pb interactions is studied at the centre-of-mass energy per nucleon–nucleon collision √sNN = 8.16 TeV with the ALICE detector at the CERN LHC. The measurement is performed reconstructing bottomonium resonances via their dimuon decay channel, in the centre-of-mass rapidity intervals 2.03 < ycms < 3.53 and −4.46 < ycms < −2.96, down to zero transverse momentum. In this work, results on the ϒ(1S) production cross section as a function of rapidity and transverse momentum are presented. The corresponding nuclear modification factor shows a suppression of the ϒ(1S) yields with respect to pp collisions, both at forward and backward rapidity. This suppression is stronger in the low transverse momentum region and shows no significant dependence on the centrality of the interactions. Furthermore, the ϒ(2S) nuclear modification factor is evaluated, suggesting a suppression similar to that of the ϒ(1S). A first measurement of the ϒ(3S) has also been performed. Finally, results are compared with previous ALICE measurements in p–Pb collisions at √sNN = 5.02 TeV and with theoretical calculations.publishedVersio
(Anti-)deuteron production in pp collisions at 1as=13TeV
The study of (anti-)deuteron production in pp collisions has proven to be a powerful tool to investigate the formation mechanism of loosely bound states in high-energy hadronic collisions. In this paper the production of (anti-)deuterons is studied as a function of the charged particle multiplicity in inelastic pp collisions at s=13 TeV using the ALICE experiment. Thanks to the large number of accumulated minimum bias events, it has been possible to measure (anti-)deuteron production in pp collisions up to the same charged particle multiplicity (d Nch/ d \u3b7 3c 26) as measured in p\u2013Pb collisions at similar centre-of-mass energies. Within the uncertainties, the deuteron yield in pp collisions resembles the one in p\u2013Pb interactions, suggesting a common formation mechanism behind the production of light nuclei in hadronic interactions. In this context the measurements are compared with the expectations of coalescence and statistical hadronisation models (SHM)
Multiplicity dependence of inclusive J/psi production at midrapidity in pp collisions at root s=13 TeV
Measurements of the inclusive J/psi yield as a function of charged-particle pseudorapidity density dN(ch)/d eta in pp collisions at root s = 13 TeV with ALICE at the LHC are reported. The J/psi meson yield is measured at midrapidity (vertical bar y vertical bar <0.9) in the dielectron channel, for events selected based on the charged-particle multiplicity at midrapidity (vertical bar eta vertical bar <1) and at forward rapidity (-3.7 <eta <-1.7 and 2.8 <eta <5.1); both observables are normalized to their corresponding averages in minimum bias events. The increase of the normalized J/psi yield with normalized dN(ch)/d eta is significantly stronger than linear and dependent on the transverse momentum. The data are compared to theoretical predictions, which describe the observed trends well, albeit not always quantitatively. (C) 2020 European Organization for Nuclear Research. Published by Elsevier B.V.Peer reviewe
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