19,705 research outputs found
Private Data System Enabling Self-Sovereign Storage Managed by Executable Choreographies
With the increased use of Internet, governments and large companies store and
share massive amounts of personal data in such a way that leaves no space for
transparency. When a user needs to achieve a simple task like applying for
college or a driving license, he needs to visit a lot of institutions and
organizations, thus leaving a lot of private data in many places. The same
happens when using the Internet. These privacy issues raised by the centralized
architectures along with the recent developments in the area of serverless
applications demand a decentralized private data layer under user control. We
introduce the Private Data System (PDS), a distributed approach which enables
self-sovereign storage and sharing of private data. The system is composed of
nodes spread across the entire Internet managing local key-value databases. The
communication between nodes is achieved through executable choreographies,
which are capable of preventing information leakage when executing across
different organizations with different regulations in place. The user has full
control over his private data and is able to share and revoke access to
organizations at any time. Even more, the updates are propagated instantly to
all the parties which have access to the data thanks to the system design.
Specifically, the processing organizations may retrieve and process the shared
information, but are not allowed under any circumstances to store it on long
term. PDS offers an alternative to systems that aim to ensure self-sovereignty
of specific types of data through blockchain inspired techniques but face
various problems, such as low performance. Both approaches propose a
distributed database, but with different characteristics. While the
blockchain-based systems are built to solve consensus problems, PDS's purpose
is to solve the self-sovereignty aspects raised by the privacy laws, rules and
principles.Comment: DAIS 201
Hydrodynamic limit of asymmetric exclusion processes under diffusive scaling in
We consider the asymmetric exclusion process. We start from a profile which
is constant along the drift direction and prove that the density profile, under
a diffusive rescaling of time, converges to the solution of a parabolic
equation
Singularity Theory in Classical Cosmology
This paper compares recent approaches appearing in the literature on the
singularity problem for space-times with nonvanishing torsion.Comment: 4 pages, plain-tex, published in Nuovo Cimento B, volume 107, pages
849-851, year 199
Arbitrary p-form Galileons
We show that scalar, 0-form, Galileon actions --models whose field equations
contain only second derivatives-- can be generalized to arbitrary even p-forms.
More generally, they need not even depend on a single form, but may involve
mixed p combinations, including equal p multiplets, where odd p-fields are also
permitted: We construct, for given dimension D, general actions depending on
scalars, vectors and higher p-form field strengths, whose field equations are
of exactly second derivative order. We also discuss and illustrate their
curved-space generalizations, especially the delicate non-minimal couplings
required to maintain this order. Concrete examples of pure and mixed actions,
field equations and their curved space extensions are presented.Comment: 8 pages, no figure, RevTeX4 format, v2: minor editorial changes
reflecting the published version in PRD Rapid Communication
Generalized Galileons: All scalar models whose curved background extensions maintain second-order field equations and stress tensors
We extend to curved backgrounds all flat-space scalar field models that obey purely second-order equations, while maintaining their second-order dependence on both field and metric. This extension simultaneously restores to second order the, originally higher derivative, stress tensors as well. The process is transparent and uniform for all dimensions
Covariant Galileon
We consider the recently introduced "galileon" field in a dynamical
spacetime. When the galileon is assumed to be minimally coupled to the metric,
we underline that both field equations of the galileon and the metric involve
up to third-order derivatives. We show that a unique nonminimal coupling of the
galileon to curvature eliminates all higher derivatives in all field equations,
hence yielding second-order equations, without any extra propagating degree of
freedom. The resulting theory breaks the generalized "Galilean" invariance of
the original model.Comment: 10 pages, no figure, RevTeX4 format; v2 adds footnote 1, Ref. [12],
reformats the link in Ref. [14], and corrects very minor typo
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
New Developments in the Spectral Asymptotics of Quantum Gravity
A vanishing one-loop wave function of the Universe in the limit of small
three-geometry is found, on imposing diffeomorphism-invariant boundary
conditions on the Euclidean 4-ball in the de Donder gauge. This result suggests
a quantum avoidance of the cosmological singularity driven by full
diffeomorphism invariance of the boundary-value problem for one-loop quantum
theory. All of this is made possible by a peculiar spectral cancellation on the
Euclidean 4-ball, here derived and discussed.Comment: 7 pages, latex file. Paper prepared for the Conference "QFEXT05:
Quantum Field Theory Under the Influence of External Conditions", Barcelona,
September 5 - September 9, 2005. In the final version, the presentation has
been further improved, and yet other References have been adde
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