3,861 research outputs found
Search for exotic contributions to atmospheric neutrino oscillations
The energy spectrum of neutrino-induced upward-going muons in MACRO was
analysed in terms of relativity principles violating effects, keeping standard
mass-induced atmospheric neutrino oscillations as the dominant effect. The data
disfavor these possibilities even at a sub-dominant level; stringent 90% C.L.
limits are placed on the Lorentz invariance violation parameter at = 0 and at = 1. The limits can be re-interpreted as
bounds on the Equivalence Principle violation parameters.Comment: Presented at the 29th I.C.R.C., Pune, India (2005
Geodesics in the space of measure-preserving maps and plans
We study Brenier's variational models for incompressible Euler equations.
These models give rise to a relaxation of the Arnold distance in the space of
measure-preserving maps and, more generally, measure-preserving plans. We
analyze the properties of the relaxed distance, we show a close link between
the Lagrangian and the Eulerian model, and we derive necessary and sufficient
optimality conditions for minimizers. These conditions take into account a
modified Lagrangian induced by the pressure field. Moreover, adapting some
ideas of Shnirelman, we show that, even for non-deterministic final conditions,
generalized flows can be approximated in energy by flows associated to
measure-preserving maps
Time correlations of high energy muons in an underground detector
We present the result of a search for correlations in the arrival times of
high energy muons collected from 1995 till 2000 with the streamer tube system
of the complete MACRO detector at the underground Gran Sasso Lab. Large samples
of single muons (8.6 million), double muons (0.46 million) and multiple muons
with multiplicities from 3 to 6 (0.08 million) were selected. These samples
were used to search for time correlations of cosmic ray particles coming from
the whole upper hemisphere or from selected space cones. The results of our
analyses confirm with high statistics a random arrival time distribution of
high energy cosmic rays.Comment: (12 pages, 7 figures, Accepted for publication in Astroparticle
Physics
Monge's transport problem in the Heisenberg group
We prove the existence of solutions to Monge transport problem between two
compactly supported Borel probability measures in the Heisenberg group equipped
with its Carnot-Caratheodory distance assuming that the initial measure is
absolutely continuous with respect to the Haar measure of the group
INJURY CRITERIA FOR ATHLETES SUBJECTED TO HEAD IMPACT
INTRODUCTION - Among the athletic actions leading to human body contact the ones involving head impact and spine loading are particularly problematic as they may lead to serious injuries, even disabilities. This fact has been recognized in different sports, such as American football or cycling where head protective equipment is mandatory. Due to tight safety requirements, the aerospace and automotive industries have their activities bounded by regulations that use measures of the human tolerance to body impact and large accelerations. The criteria used to predict injury, the Head lnjury Criteria (HIC) or the Severity Index (SI), are based on the integral of the head acceleration for a period of time. The potential for injury that they provide have been established as a result of extensive testing. The objective of this paper is to show that these measures can still be used in sports activities. METHODOLOGY - In order for the injury criteria to be used in different situations it is necessary to use a human body model and a proper description of the impact situations A model made of 12 rigid segments is used for this purpose. Here the biomechanical segments are prevented from achieving unacceptable relative positions by a set of penalty forces In the biomechanical joints. The contact of the body segments of different athletes and the surrounding obstacles is modelled using an Hertzian contact theory which accounts for energy dissipation. The model used is general and can be improved to include body protection equipment. RESULTS - The biomechanical model is applied in two cases involving of impact: a car driver and a player experiencing a tackle. For each case the injury criteria are used to predict the potential for injury. Based on the results the application of the automotive industry measures of head injury in sports activities are discussed. CONCLUSIONS - The injury criteria for head impact used in the aerospace and automotive industries is still suitable for application to sports activities. However more detailed models of the head-neck complex and of the spine should be considered. The limits that define the injury potential must also be redefined for sports activities. REFERENCES Jalon, J.G. (1994). Ktnematic and dynamic simulation of multibody systems, Heidelberg: Springer-Verlag. Wismans, J (1994). Course Notes on Injury Biomechanics, Faculty of Mechanical Engineering, Eindhoven University of Technology, The Netherlands Laananen, D (1 983). Computer Simulation of an aircraft seat and occupant in a crash environment - Vol. 1: Technical report, US Dep. of Transportation, F A A,, Technical Report DOTIFANCT-82133-1 Ruan, J.S., Khalil, T., King, A I. ('1994). Dynamic response of human head to impact by three-dimensional finite element analysis. ASME J. of Biomechanical Engineering, 116. 44-50 Lankarani. H . Malapati. S R., Menon, R. (1993). Evaluation of Head lnjury Criteria NlAR Report 93-2, National Institute for Aviation Research. Wichita State University
Leptonic CP Violation Search and the Ambiguity of dm^2_31
We consider a search for the CP-violating angle deltaCP in long baseline
neutrino oscillation experiments. We show that the subleading deltaCP-dependent
terms in the nu_mu -> nu_e oscillation probability can be easily obscured by
the ambiguity of the leading term which depends on |dm^2_31|. It is thus
necessary to determine the value of dm^2_31 with a sufficient accuracy. The
nu_mu survival events, which can be accumulated simultaneously with the nu_e
appearance events, can serve for this purpose owing to its large statistics.
Therefore, the combined analysis of nu_e appearance and nu_mu survival events
is crucial to provide a restrictive constraint on deltaCP. Taking a test
experimental setup, we demonstrate in the deltaCP-dm^2_31 plane that the
analysis of nu_e appearance events leads to less restrictive constraints on the
value of deltaCP due to the ambiguity of dm^2_31 and that the combined analysis
efficiently improves the constraints.Comment: ReVTeX file, 9 pages, 7 figures. Discussions added in Sections 1, 2,
and 4; Reference expande
Calculus and heat flow in metric measure spaces and applications to spaces with Ricci bounds from below
This paper is devoted to a deeper understanding of the heat flow and to the
refinement of calculus tools on metric measure spaces (X,d,m). Our main results
are:
- A general study of the relations between the Hopf-Lax semigroup and
Hamilton-Jacobi equation in metric spaces (X,d).
- The equivalence of the heat flow in L^2(X,m) generated by a suitable
Dirichlet energy and the Wasserstein gradient flow of the relative entropy
functional in the space of probability measures P(X).
- The proof of density in energy of Lipschitz functions in the Sobolev space
W^{1,2}(X,d,m).
- A fine and very general analysis of the differentiability properties of a
large class of Kantorovich potentials, in connection with the optimal transport
problem.
Our results apply in particular to spaces satisfying Ricci curvature bounds
in the sense of Lott & Villani [30] and Sturm [39,40], and require neither the
doubling property nor the validity of the local Poincar\'e inequality.Comment: Minor typos corrected and many small improvements added. Lemma 2.4,
Lemma 2.10, Prop. 5.7, Rem. 5.8, Thm. 6.3 added. Rem. 4.7, Prop. 4.8, Prop.
4.15 and Thm 4.16 augmented/reenforced. Proof of Thm. 4.16 and Lemma 9.6
simplified. Thm. 8.6 corrected. A simpler axiomatization of weak gradients,
still equivalent to all other ones, has been propose
Fokker-Planck type equations with Sobolev diffusion coefficients and BV drift coefficients
In this paper we give an affirmative answer to an open question mentioned in
[Le Bris and Lions, Comm. Partial Differential Equations 33 (2008),
1272--1317], that is, we prove the well-posedness of the Fokker-Planck type
equations with Sobolev diffusion coefficients and BV drift coefficients.Comment: 11 pages. The proof has been modifie
Perimeter of sublevel sets in infinite dimensional spaces
We compare the perimeter measure with the Airault-Malliavin surface measure
and we prove that all open convex subsets of abstract Wiener spaces have finite
perimeter. By an explicit counter-example, we show that in general this is not
true for compact convex domains
Comparative time-resolved photoemission from the Cu(100) and Cu(111) surfaces
Citation: Ambrosio, M. J., & Thumm, U. (2016). Comparative time-resolved photoemission from the Cu(100) and Cu(111) surfaces. Physical Review A, 94(6), 14. doi:10.1103/PhysRevA.94.063424Motivated by the striking dependence of the valence electronic structure of transition metal surfaces on their crystallographic orientation, and by emerging experiments on laser-assisted extended ultraviolet (XUV) photoemission from solid surfaces, we calculate photoemission spectra from Cu(100) and Cu(111) surfaces as a function of the photoelectron final kinetic energy and the delay between the ionizing attosecond XUV pulse train and assisting infrared (IR) laser pulse. Our numerical simulations predict distinct differences in delay-dependent photoelectron energy distributions and photoemission time delays for Cu(100) and Cu(111) surfaces. These differences can be scrutinized experimentally with existing technology in a suggested in situ comparative RABBITT (reconstruction of attosecond beating by interference of two-photon transitions) configuration by placing the two surfaces on a sliding platform while keeping all optical components and pathlengths fixed. Our calculations also show that the inclusion of the Fresnel-reflected incident IR pulse at the metal-vacuum interface modifies photoelectron spectra and photoemission time delays in a characteristic way that reveals the degree of spatial location of the initial electronic states
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