2,471 research outputs found
The dynamical nature of time
It is usually assumed that the "" parameter in the equations of dynamics
can be identified with the indication of the pointer of a clock. Things are not
so easy, however. In fact, since the equations of motion can be written in
terms of but also of , being any well behaved function, each
one of those infinite parametric times is as good as the Newtonian one to
study classical dynamics. Here we show that the relation between the
mathematical parametric time in the equations of dynamics and the physical
dynamical time that is measured with clocks is more complex and subtle
than usually assumed. These two times, therefore, must be carefully
distinguished since their difference may have significant consequences.
Furthermore, we show that not all the dynamical clock-times are necessarily
equivalent and that the observational fingerprint of this non-equivalence has
the same form as that of the Pioneer anomaly.Comment: 13 pages, no figure
Mixing-induced Spontaneous Supersymmetry Breaking
It is conjectured that flavor mixing furnishes a universal mechanism for the
spontaneous breaking of supersymmetry. The conjecture is proved explicitly for
the mixing of two Wess--Zumino supermultiplets and arguments
for its general validity are given. The mechanism relies on the fact that,
despite mixing treats fermions and bosons symmetrically, both the fermionic and
the bosonic zero point energies are shifted by a positive amount and this kind
of shift does not respect supersymmetry.Comment: 5 pages, 1 figure, Eq(12) of V1 corrected to Eq(22), explicit
off-shell formulation included, one reference adde
Parsimonious Time Series Clustering
We introduce a parsimonious model-based framework for clustering time course
data. In these applications the computational burden becomes often an issue due
to the number of available observations. The measured time series can also be
very noisy and sparse and a suitable model describing them can be hard to
define. We propose to model the observed measurements by using P-spline
smoothers and to cluster the functional objects as summarized by the optimal
spline coefficients. In principle, this idea can be adopted within all the most
common clustering frameworks. In this work we discuss applications based on a
k-means algorithm. We evaluate the accuracy and the efficiency of our proposal
by simulations and by dealing with drosophila melanogaster gene expression
data
Sample-to-sample fluctuations of power spectrum of a random motion in a periodic Sinai model
The Sinai model of a tracer diffusing in a quenched Brownian potential is a
much studied problem exhibiting a logarithmically slow anomalous diffusion due
to the growth of energy barriers with the system size. However, if the
potential is random but periodic, the regime of anomalous diffusion crosses
over to one of normal diffusion once a tracer has diffused over a few periods
of the system. Here we consider a system in which the potential is given by a
Brownian Bridge on a finite interval and then periodically repeated
over the whole real line, and study the power spectrum of the diffusive
process in such a potential. We show that for most of realizations of
in a given realization of the potential, the low-frequency behavior is
, i.e., the same as for standard Brownian motion, and
the amplitude is a disorder-dependent random variable with a finite
support. Focusing on the statistical properties of this random variable, we
determine the moments of of arbitrary, negative or positive order
, and demonstrate that they exhibit a multi-fractal dependence on , and a
rather unusual dependence on the temperature and on the periodicity , which
are supported by atypical realizations of the periodic disorder. We finally
show that the distribution of has a log-normal left tail, and
exhibits an essential singularity close to the right edge of the support, which
is related to the Lifshitz singularity. Our findings are based both on analytic
results and on extensive numerical simulations of the process .Comment: 8 pages, 5 figure
Impact of Lorentz Violation Models on Exoplanets’ Dynamics
Many exoplanets have been detected by the radial velocity method, according to which the motion of a binary system around its center of mass can produce a periodical variation of the Doppler effect of the light emitted by the host star. These variations are influenced by both Newtonian and non-Newtonian perturbations to the dominant inverse-square acceleration; accordingly, exoplanetary systems lend themselves to testing theories of gravity alternative to general relativity. In this paper, we consider the impact of the Standard Model Extension (a model that can be used to test all possible Lorentz violations) on the perturbation of radial velocity and suggest that suitable exoplanets’ configurations and improvements in detection techniques may contribute to obtaining new constraints on the model parameters
RAYGO: Reserve As You GO
The capability to predict the precise resource requirements of a microservice-based application is a very important problem for cloud services. In fact, the allocation of abundant resources guarantees an excellent quality of experience (QoE) for the hosted services, but it can translate into unnecessary costs for the cloud customer due to the reserved (but unused) resources. On the other side, poor resource provisioning may turn out in scarce performance when experiencing an unexpected peak of demand. This paper proposes RAYGO, a novel approach for dynamic resource provisioning to microservices in Kubernetes that (i) reliefs the customers from the definition of appropriate execution boundaries, (ii) ensures the right amount of resources at any time, according to the past and the predicted usage, and (iii) operates at the application level, acknowledging the dependency between multiple correlated microservices
Early diagnosis of perioperative myocardial infarctionafter cdoronary bypass grafting: Why is the incidenceso high?
Computing Without Borders: The Way Towards Liquid Computing
Despite the de-facto technological uniformity fostered by the cloud and edge computing paradigms, resource fragmentation across isolated clusters hinders the dynamism in application placement, leading to suboptimal performance and operational complexity. Building upon and extending these paradigms, we propose a novel approach envisioning a transparent continuum of resources and services on top of the underlying fragmented infrastructure, called liquid computing. Fully decentralized, multi-ownership-oriented and intent-driven, it enables an overarching abstraction for improved applications execution, while at the same time opening up for new scenarios, including resource sharing and brokering. Following the above vision, we present liqo, an open-source project that materializes this approach through the creation of dynamic and seamless Kubernetes multi-cluster topologies. Extensive experimental evaluations have shown its effectiveness in different contexts, both in terms of Kubernetes overhead and compared to other open-source alternatives
Fine-root morphological and growth traits in a Turkey-oak stand in relation to seasonal changes in soil moisture in the Southern Apennines, Italy
We investigated the effects of seasonal changes
in soil moisture on the morphological and growth traits
of fine roots (<2 mm in diameter) in a mature Turkeyoak
stand (Quercus cerris L.) in the Southern Apennines
of Italy. Root samples (diameter: <0.5, 0.5\u20131.0, 1.0\u20131.5,
and 1.5\u20132.0 mm) were collected with the Auger method.
Mean annual fine-root mass and length on site was
443 g m!2 (oak fine roots 321 g m!2; other species
122 g m!2) and 3.18 km m!2 (oak fine roots 1.14 km
m!2; other species 2.04 km m!2), respectively. Mean
specific root length was 8.3 m g!1. All fine-root traits
displayed a complex pattern that was significantly related
to season. In the four diameter classes, both fineroot
biomass and length peaked in summer when soil
water content was the lowest and air temperature the
highest of the season. Moreover, both fine-root biomass
and length were inversely related with soil moisture
(p < 0.001). The finest roots (<0.5 mm in diameter)
constituted an important fraction of total fine-root
length (79 %), but only 21 % of biomass. Only in this
root class, consequent to change in mean diameter,
specific root length peaked when soil water content was
lowest showing an inverse relationship (p < 0.001).
Furthermore, fine-root production and turnover decreased
with increasing root diameter. These results
suggest that changes in root length per unit mass, and
pulses in root growth to exploit transient periods of low
soil water content may enable trees to increase nutrient
and water uptake under seasonal drought conditions
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