7,610 research outputs found
Searching in Unstructured Overlays Using Local Knowledge and Gossip
This paper analyzes a class of dissemination algorithms for the discovery of
distributed contents in Peer-to-Peer unstructured overlay networks. The
algorithms are a mix of protocols employing local knowledge of peers'
neighborhood and gossip. By tuning the gossip probability and the depth k of
the k-neighborhood of which nodes have information, we obtain different
dissemination protocols employed in literature over unstructured P2P overlays.
The provided analysis and simulation results confirm that, when properly
configured, these schemes represent a viable approach to build effective P2P
resource discovery in large-scale, dynamic distributed systems.Comment: A revised version of the paper appears in Proc. of the 5th
International Workshop on Complex Networks (CompleNet 2014) - Studies in
Computational Intelligence Series, Springer-Verlag, Bologna (Italy), March
201
A Study of Holographic Renormalization Group Flows in d=6 and d=3
We present an explicit study of the holographic renormalization group (RG) in
six dimensions using minimal gauged supergravity. By perturbing the theory with
the addition of a relevant operator of dimension four one flows to a
non-supersymmetric conformal fixed point. There are also solutions describing
non-conformal vacua of the same theory obtained by giving an expectation value
to the operator. One such vacuum is supersymmetric and is obtained by using the
true superpotential of the theory. We discuss the physical acceptability of
these vacua by applying the criteria recently given by Gubser for the four
dimensional case and find that those criteria give a clear physical picture in
the six dimensional case as well. We use this example to comment on the role of
the Hamilton-Jacobi equations in implementing the RG. We conclude with some
remarks on AdS_4 and the status of three dimensional superconformal theories
from squashed solutions of M-theory.Comment: 15 pages, 5 figures, V2: minor change
Conformal Solutions Of Duality Invariant 2D Magnetohydrodynamic Turbulence
We consider possible conformal field theory (CFT) descriptions of the various
inertial ranges that exist in duality invariant Magnetohydrodynamics. Such
models arise as effective theories of dyonic plasmas in 3 dimensions in which
all fields are independent of the third coordinate. We find new constraints on
the allowed CFT's compared to those that may describe turbulence in
plasmas of electric charges only. The predictions from CFT concerning
equipartition of energy amongst the electric and magnetic fields are discussed,
and quantities exhibiting universal scaling are derived.Comment: Latex, 8 page
Duality Invariant Magnetohydrodynamics And Dyons
The theory of magnetohydrodynamics is extended to the cases of a plasma of
separate magnetic and electric charges, as well as to a plasma of dyons
respectively. In both these cases the system possesses electric-magnetic
duality symmetry. In the former case we find that because of the existence of
two independent generalized Ohm's law equations, the limit of infinite electric
and magnetic conductivity results in the vanishing of both electric and
magnetic fields, as well as the corresponding currents. In the dyonic case, we
find that the resulting duality-invariant system of equations are equivalent to
those of ordinary MHD, after suitable field redefinitions.Comment: 11 pages, late
Segond's fracture: a biomechanical cadaveric study using navigation
Background Segond’s fracture is a well-recognised radiological
sign of an anterior cruciate ligament (ACL) tear.
While previous studies evaluated the role of the anterolateral
ligament (ALL) and complex injuries on rotational
stability of the knee, there are no studies on the biomechanical
effect of Segond’s fracture in an ACL deficient
knee. The aim of this study was to evaluate the effect of a
Segond’s fracture on knee rotation stability as evaluated by
a navigation system in an ACL deficient knee.
Materials and methods Three different conditions were
tested on seven knee specimens: intact knee, ACL deficient
knee and ACL deficient knee with Segond’s fracture. Static
and dynamic measurements of anterior tibial translation
(ATT) and axial tibial rotation (ATR) were recorded by the
navigation system (2.2 OrthoPilot ACL navigation system
B. Braun Aesculap, Tuttlingen, Germany).
Results Static measurements at 30 showed that the mean
ATT at 30 of knee flexion was 5.1 ± 2.7 mm in the ACL
intact condition, 14.3 ± 3.1 mm after ACL cut
(P = 0.005), and 15.2 ± 3.6 mm after Segond’s fracture
(P = 0.08). The mean ATR at 30 of knee flexion was
20.7 ± 4.8 in the ACL intact condition, 26.9 ± 4.1 in
the ACL deficient knee (P[0.05) and 30.9 ± 3.8 after
Segond’s fracture (P = 0.005). Dynamic measurements
during the pivot-shift showed that the mean ATT was
7.2 ± 2.7 mm in the intact knee, 9.1 ± 3.3 mm in the
ACL deficient knee(P = 0.04) and 9.7 ± 4.3 mm in the
ACL deficient knee with Segond’s fracture (P = 0.07).
The mean ATR was 9.6 ± 1.8 in the intact knee,
12.3 ± 2.3 in the ACL deficient knee (P[0.05) and
19.1 ± 3.1 in the ACL deficient knee with Segond’s
lesion (P = 0.016).
Conclusion An isolated lesion of the ACL only affects
ATT during static and dynamic measurements, while the
addition of Segond’s fracture has a significant effect on
ATR in both static and dynamic execution of the pivot-shift
test, as evaluated with the aid of navigation
Stars in the Silurian sky : Echinoderm holdfasts from the Carnic Alps, Austria
A small collection of echinoderm holdfasts from the Ludlow Cardiola Formation of the Carnic Alps (Austria) contains a wide range of morphologies as a response of environmental adaptation. In general, the holdfasts have a globous and massive dome-like profile with several processes arranged in a sub-radial disposition, so to create a sort of 'star-like' outline. A small central depression is common but not present on all specimens. The distinctive holdfasts are preserved in an iron-rich phase, documenting a substitution that has also affected other non-echinoderm calcareous material
A record-driven growth process
We introduce a novel stochastic growth process, the record-driven growth
process, which originates from the analysis of a class of growing networks in a
universal limiting regime. Nodes are added one by one to a network, each node
possessing a quality. The new incoming node connects to the preexisting node
with best quality, that is, with record value for the quality. The emergent
structure is that of a growing network, where groups are formed around record
nodes (nodes endowed with the best intrinsic qualities). Special emphasis is
put on the statistics of leaders (nodes whose degrees are the largest). The
asymptotic probability for a node to be a leader is equal to the Golomb-Dickman
constant omega=0.624329... which arises in problems of combinatorical nature.
This outcome solves the problem of the determination of the record breaking
rate for the sequence of correlated inter-record intervals. The process
exhibits temporal self-similarity in the late-time regime. Connections with the
statistics of the cycles of random permutations, the statistical properties of
randomly broken intervals, and the Kesten variable are given.Comment: 30 pages,5 figures. Minor update
On the Thermal History of Calculable Gauge Mediation
Many messenger models with realistic gaugino masses are based on meta-stable
vacua. In this work we study the thermal history of some of these models.
Analyzing R-symmetric models, we point out that while some of the known
messenger models clearly prefer the supersymmetric vacuum, there is a vast
class of models where the answer depends on the initial conditions. Along with
the vacuum at the origin, the high temperature thermal potential also possesses
a local minimum far away from the origin. This vacuum has no analog at zero
temperature. The first order phase transition from this vacuum into the
supersymmetric vacuum is parametrically suppressed, and the theory, starting
from that vacuum, is likely to evolve to the desired gauge-mediation vacuum. We
also comment on the thermal evolution of models without R-symmetry.Comment: 22 pages. V2: Comments on the SM effects added. Minor corrections.
Reference added. Valuable discussion with S. Abel, J. Jaeckel and V. Khoze
acknowledged. V3: Types of EOGM explicitly defined in the introduction.
Discussions about the phase transitions expanded. Typo corrected. Journal
versio
Credit bureaus between risk-management, creditworthiness assessment and prudential supervision
"This text may be downloaded for personal research purposes only. Any additional reproduction for other purposes, whether in hard copy or electronically, requires the consent of the author. If cited or quoted, reference should be made to the full name of the author, the title, the working paper or other series, the year, and the publisher."This paper discusses the role and operations of consumer Credit Bureaus in the European Union in the context of the economic theories, policies and law within which they work. Across Europe there is no common practice of sharing the credit data of consumers which can be used for several purposes. Mostly, they are used by the lending industry as a practice of creditworthiness assessment or as a risk-management tool to underwrite borrowing decisions or price risk. However, the type, breath, and depth of information differ greatly from country to country. In some Member States, consumer data are part of a broader information centralisation system for the prudential supervision of banks and the financial system as a whole. Despite EU rules on credit to consumers for the creation of the internal market, the underlying consumer data infrastructure remains fragmented at national level, failing to achieve univocal, common, or defined policy objectives under a harmonised legal framework. Likewise, the establishment of the Banking Union and the prudential supervision of the Euro area demand standardisation and convergence of the data used to measure debt levels, arrears, and delinquencies. The many functions and usages of credit data suggest that the policy goals to be achieved should inform the legal and institutional framework of Credit Bureaus, as well as the design and use of the databases. This is also because fundamental rights and consumer protection concerns arise from the sharing of credit data and their expanding use
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