411 research outputs found
Non-Involutive Constrained Systems and Hamilton-Jacobi Formalism
In this work we discuss the natural appearance of the Generalized Brackets in
systems with non-involutive (equivalent to second class) constraints in the
Hamilton-Jacobi formalism. We show how a consistent geometric interpretation of
the integrability conditions leads to the reduction of degrees of freedom of
these systems and, as consequence, naturally defines a dynamics in a reduced
phase space.Comment: 12 page
General Relativity in two dimensions: a Hamilton-Jacobi constraint analysis
We will analyze the constraint structure of the Einstein-Hilbert first-order
action in two dimensions using the Hamilton-Jacobi approach. We will be able to
find a set of involutive, as well as a set of non-involutive constraints. Using
generalized brackets we will show how to assure integrability of the theory, to
eliminate the set of non-involutive constraints, and to build the field
equations
Hamilton-Jacobi Approach for First Order Actions and Theories with Higher Derivatives
In this work we analyze systems described by Lagrangians with higher order
derivatives in the context of the Hamilton-Jacobi formalism for first order
actions. Two different approaches are studied here: the first one is analogous
to the description of theories with higher derivatives in the hamiltonian
formalism according to [Sov. Phys. Journ. 26 (1983) 730; the second treats the
case where degenerate coordinate are present, in an analogy to reference [Nucl.
Phys. B 630 (2002) 509]. Several examples are analyzed where a comparison
between both approaches is made
Average shape of fluctuations for subdiffusive walks
We study the average shape of fluctuations for subdiffusive processes, i.e.,
processes with uncorrelated increments but where the waiting time distribution
has a broad power-law tail. This shape is obtained analytically by means of a
fractional diffusion approach. We find that, in contrast with processes where
the waiting time between increments has finite variance, the fluctuation shape
is no longer a semicircle: it tends to adopt a table-like form as the
subdiffusive character of the process increases. The theoretical predictions
are compared with numerical simulation results.Comment: 4 pages, 6 figures. Accepted for publication Phys. Rev. E (Replaced
for the latest version, in press.) Section II rewritte
Search for neutrinos from the tidal disruption events AT2019dsg and AT2019fdr with the ANTARES telescope
The authors acknowledge the financial support of the funding agencies: Centre National de la Recherche Scientifique (CNRS), Commissariat a l'energie atomique et aux energies alternatives (CEA), Commission Europeenne (FEDER fund and Marie Curie Program), Institut Universitaire de France (IUF), LabEx UnivEarthS (ANR-10-LABX-0023 and ANR-18-IDEX-0001), Region Ile-de-France (DIM-ACAV), Region Alsace (contrat CPER), Region Provence-Alpes-Cote d'Azur, Departement du Var and Ville de La Seyne-sur-Mer, France; Bundesministerium fur Bildung und Forschung (BMBF), Germany; Istituto Nazionale di Fisica Nucleare (INFN), Italy; Nederlandse organisatie voor Wetenschappelijk Onderzoek (NWO), the Netherlands; Council of the President of the Russian Federation for young scientists and leading scientific schools supporting grants, Russia; Executive Unit for Financing Higher Education, Research, Development and Innovation (UEFISCDI), Romania; Ministerio de Ciencia e Innovacion (MCI) and Agencia Estatal de Investigacion: Programa Estatal de Generacion de Conocimiento (refs. PGC2018-096663-B-C41, -A-C42, -B-C43, -B-C44) (MCI/FEDER), Severo Ochoa Centre of Excellence and MultiDark Consolider, Junta de Andalucia (ref. SOMM17/6104/UGR and A-FQM-053-UGR18), Generalitat Valenciana: Grisolia (ref. GRISOLIA/2018/119) and GenT (ref. CIDEGENT/2018/034) programs, Spain; Ministry of Higher Education, Scientific Research and Professional Training, Morocco. We also acknowledge the technical support of Ifremer, AIM and Foselev Marine for the sea operation and the CC-IN2P3 for the computing facilities.On October 1, 2019, the IceCube Collaboration detected a muon track neutrino with
high probability of being of astrophysical origin, IC191001A. After a few hours, the tidal
disruption event (TDE) AT2019dsg, observed by the Zwicky Transient Facility (ZTF), was
indicated as the most likely counterpart of the IceCube track. More recently, the followup
campaign of the IceCube alerts by ZTF suggested a second TDE, AT2019fdr, as a
promising counterpart of another IceCube muon track candidate, IC200530A, detected on
May 30, 2020. These are the second and third associations between astrophysical sources
and high-energy neutrinos after the compelling identification of the blazar TXS 0506+056.
Here, the search for ANTARES neutrinos from the directions of AT2019dsg and AT2019fdr
using a time-integrated approach is presented. As no significant evidence for space clustering
is found in the ANTARES data, upper limits on the one-flavour neutrino flux and fluence
are set.Centre National de la Recherche Scientifique (CNRS)French Atomic Energy CommissionCommission Europeenne (FEDER fund and Marie Curie Program)Institut Universitaire de France (IUF)LabEx UnivEarthS ANR-10-LABX-0023
ANR-18-IDEX-0001Region Ile-de-FranceRegion Grand-EstRegion Provence-Alpes-Cote d'AzurFederal Ministry of Education & Research (BMBF)Istituto Nazionale di Fisica Nucleare (INFN)Netherlands Organization for Scientific Research (NWO)Netherlands GovernmentCouncil of the President of the Russian Federation for young scientists and leading scientific schools supporting grants, RussiaConsiliul National al Cercetarii Stiintifice (CNCS)Unitatea Executiva pentru Finantarea Invatamantului Superior, a Cercetarii, Dezvoltarii si Inovarii (UEFISCDI)Spanish GovernmentAgencia Estatal de Investigacion (MCI/FEDER) PGC2018-096663-B-C41
PGC2018-096663-A-C42
PGC2018-096663-B-C43
PGC2018-096663-B-C44Severo Ochoa Centre of Excellence and MultiDark Consolider, Junta de Andalucia SOMM17/6104/UGR
A-FQM-053-UGR18Generalitat Valenciana GRISOLIA/2018/119
CIDEGENT/2018/034Ministry of Higher Education, Scientific Research and Professional Training, Morocc
Colloquium: Mechanical formalisms for tissue dynamics
The understanding of morphogenesis in living organisms has been renewed by
tremendous progressin experimental techniques that provide access to
cell-scale, quantitative information both on theshapes of cells within tissues
and on the genes being expressed. This information suggests that
ourunderstanding of the respective contributions of gene expression and
mechanics, and of their crucialentanglement, will soon leap forward.
Biomechanics increasingly benefits from models, which assistthe design and
interpretation of experiments, point out the main ingredients and assumptions,
andultimately lead to predictions. The newly accessible local information thus
calls for a reflectionon how to select suitable classes of mechanical models.
We review both mechanical ingredientssuggested by the current knowledge of
tissue behaviour, and modelling methods that can helpgenerate a rheological
diagram or a constitutive equation. We distinguish cell scale ("intra-cell")and
tissue scale ("inter-cell") contributions. We recall the mathematical framework
developpedfor continuum materials and explain how to transform a constitutive
equation into a set of partialdifferential equations amenable to numerical
resolution. We show that when plastic behaviour isrelevant, the dissipation
function formalism appears appropriate to generate constitutive equations;its
variational nature facilitates numerical implementation, and we discuss
adaptations needed in thecase of large deformations. The present article
gathers theoretical methods that can readily enhancethe significance of the
data to be extracted from recent or future high throughput
biomechanicalexperiments.Comment: 33 pages, 20 figures. This version (26 Sept. 2015) contains a few
corrections to the published version, all in Appendix D.2 devoted to large
deformation
Performance of the First ANTARES Detector Line
In this paper we report on the data recorded with the first Antares detector
line. The line was deployed on the 14th of February 2006 and was connected to
the readout two weeks later. Environmental data for one and a half years of
running are shown. Measurements of atmospheric muons from data taken from
selected runs during the first six months of operation are presented.
Performance figures in terms of time residuals and angular resolution are
given. Finally the angular distribution of atmospheric muons is presented and
from this the depth profile of the muon intensity is derived.Comment: 14 pages, 9 figure
Grain Surface Models and Data for Astrochemistry
AbstractThe cross-disciplinary field of astrochemistry exists to understand the formation, destruction, and survival of molecules in astrophysical environments. Molecules in space are synthesized via a large variety of gas-phase reactions, and reactions on dust-grain surfaces, where the surface acts as a catalyst. A broad consensus has been reached in the astrochemistry community on how to suitably treat gas-phase processes in models, and also on how to present the necessary reaction data in databases; however, no such consensus has yet been reached for grain-surface processes. A team of ∼25 experts covering observational, laboratory and theoretical (astro)chemistry met in summer of 2014 at the Lorentz Center in Leiden with the aim to provide solutions for this problem and to review the current state-of-the-art of grain surface models, both in terms of technical implementation into models as well as the most up-to-date information available from experiments and chemical computations. This review builds on the results of this workshop and gives an outlook for future directions
Acoustic and optical variations during rapid downward motion episodes in the deep north-western Mediterranean Sea
An Acoustic Doppler Current Profiler (ADCP) was moored at the deep-sea site
of the ANTARES neutrino telescope near Toulon, France, thus providing a unique
opportunity to compare high-resolution acoustic and optical observations
between 70 and 170 m above the sea bed at 2475 m. The ADCP measured downward
vertical currents of magnitudes up to 0.03 m s-1 in late winter and early
spring 2006. In the same period, observations were made of enhanced levels of
acoustic reflection, interpreted as suspended particles including zooplankton,
by a factor of about 10 and of horizontal currents reaching 0.35 m s-1. These
observations coincided with high light levels detected by the telescope,
interpreted as increased bioluminescence. During winter 2006 deep dense-water
formation occurred in the Ligurian subbasin, thus providing a possible
explanation for these observations. However, the 10-20 days quasi-periodic
episodes of high levels of acoustic reflection, light and large vertical
currents continuing into the summer are not direct evidence of this process. It
is hypothesized that the main process allowing for suspended material to be
moved vertically later in the year is local advection, linked with topographic
boundary current instabilities along the rim of the 'Northern Current'.Comment: 30 pages, 7 figure
Measurement of Atmospheric Neutrino Oscillations with the ANTARES Neutrino Telescope
The data taken with the ANTARES neutrino telescope from 2007 to 2010, a total
live time of 863 days, are used to measure the oscillation parameters of
atmospheric neutrinos. Muon tracks are reconstructed with energies as low as 20
GeV. Neutrino oscillations will cause a suppression of vertical upgoing muon
neutrinos of such energies crossing the Earth. The parameters determining the
oscillation of atmospheric neutrinos are extracted by fitting the event rate as
a function of the ratio of the estimated neutrino energy and reconstructed
flight path through the Earth. Measurement contours of the oscillation
parameters in a two-flavour approximation are derived. Assuming maximum mixing,
a mass difference of eV is
obtained, in good agreement with the world average value.Comment: 9 pages, 5 figure
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