660 research outputs found
The emergence of the Cabibbo angle in non-degenerate coupled systems of fermions
Investigating, in direct continuation of our previous paper hep-ph/0606303
the implications of the non-unitarity of mixing matrices for non-degenerate
coupled systems that we demonstrated there, we examine more accurately the
vicinity of Cabibbo-like mixing in quantum field theory. We show that it is
possible to preserve one of its main features, namely that, in the space of
mass eigenstates, the two requirements -- of universality for weak diagonal
currents and -- of the absence of their non-diagonal counterparts, although not
fulfilled separately any more, can however reduce to a single condition for a
unique mixing angle theta\_c. This leads to tan (2 theta\_c)=+/- 1/2, or cos
theta\_c \approx 0.9732, only 7/10000 away from experimental results. No mass
ratio appears in the argumentation.Comment: This is a different version of hep-ph/0607193, with a simplified
argumentation, a clearer connection with hep-ph/0606303. The solution for the
Cabibbo angle is also expressed in terms of the golden number. To appear in
Phys. Lett.
Quark Lagrangian diagonalization versus non-diagonal kinetic terms
Loop corrections induce a dependence on the momentum squared of the
coefficients of the Standard Model Lagrangian, making highly non-trivial (or
even impossible) the diagonalization of its quadratic part. Fortunately, the
introduction of appropriate counterterms solves this puzzle.Comment: 2 pages, 1 figur
Ocean Governance and Maritime Security in a Placeful Environment: The Case of the European Union
Adopting a critical geopolitics approach that accounts for the mutually reinforcing link between geo-informed narratives and power projection practices, this article proposes that ocean governance and maritime security have translated into states’ and regional organisations’ increasing control over maritime spaces. This leads to a certain territorialisation of the sea, not so much from a sovereignty and jurisdictional perspective but from a functional and normative perspective. The article starts by discussing the ways oceans have been represented and shows that they are far from a placeless void, both in practice and in discourse. The article then frames the analysis of ocean governance and maritime security within critical geopolitics, and elaborates on the case of the European Union’s narrative and practice. It concludes on the mutually reinforcing link between discourse and practice in the field of ocean governance and maritime security in general, and on the consequences in terms of power projection for the EU in particular. Scholars working on ocean governance and maritime security are encouraged to challenge the traditional view that oceans are placeless
Wide range and tunable linear TMR sensor using two exchange pinned electrodes
A magnetic tunnel junction sensor is proposed, with both the detection and
the reference layers pinned by IrMn. Using the differences in the blocking
temperatures of the IrMn films with different thicknesses, crossed anisotropies
can be induced between the detection and the reference electrodes. The pinning
of the sensing electrode ensures a linear and reversible output. It also allows
tuning both the sensitivity and the linear range of the sensor. The authors
show that the sensitivity varies linearly with the ferromagnetic thickness of
the detection electrode. It is demonstrated that an increased thickness leads
to a rise of sensitivity and a reduction of the operating range
Discrete symmetries and the propagator approach to coupled fermions in Quantum Field Theory. Generalities. The case of a single fermion-antifermion pair
Starting from Wigner's symmetry representation theorem, we give a general
account of discrete symmetries (parity P, charge conjugation C, time-reversal
T), focusing on fermions in Quantum Field Theory. We provide the rules of
transformation of Weyl spinors, both at the classical level (grassmanian wave
functions) and quantum level (operators). Making use of Wightman's definition
of invariance, we outline ambiguities linked to the notion of classical
fermionic Lagrangian. We then present the general constraints cast by these
transformations and their products on the propagator of the simplest among
coupled fermionic system, the one made with one fermion and its antifermion.
Last, we put in correspondence the propagation of C eigenstates (Majorana
fermions) and the criteria cast on their propagator by C and CP invariance.Comment: 37 pages, LaTeX. version to appear in "Annals of Physics (N.Y.)
New DRIE-Patterned Electrets for Vibration Energy Harvesting
This paper is about a new manufacturing process aimed at developing stable
SiO2/Si3N4 patterned electrets using a Deep Reactive Ion Etching (DRIE) step
for an application in electret-based Vibration Energy Harvesters (e-VEH). This
process consists in forming continuous layers of SiO2/Si3N4 electrets in order
to limit surface conduction phenomena and is a new way to see the problem of
electret patterning. Experimental results prove that patterned electrets
charged by a positive corona discharge show excellent stability with high
surface charge densities that may reach 5mC/m^2 on 1.1\mu m-thick layers, even
with fine patterning and harsh temperature conditions (up to 250{\deg}C). This
paves the way to new e-VEH designs and manufacturing processes.Comment: Proc. European Energy Conference, 201
Coupling techniques for nonlinear hyperbolic equations. III. The well-balanced approximation of thick interfaces
We continue our analysis of the coupling between nonlinear hyperbolic
problems across possibly resonant interfaces. In the first two parts of this
series, we introduced a new framework for coupling problems which is based on
the so-called thin interface model and uses an augmented formulation and an
additional unknown for the interface location; this framework has the advantage
of avoiding any explicit modeling of the interface structure. In the present
paper, we pursue our investigation of the augmented formulation and we
introduce a new coupling framework which is now based on the so-called thick
interface model. For scalar nonlinear hyperbolic equations in one space
variable, we observe that the Cauchy problem is well-posed. Then, our main
achievement in the present paper is the design of a new well-balanced finite
volume scheme which is adapted to the thick interface model, together with a
proof of its convergence toward the unique entropy solution (for a broad class
of nonlinear hyperbolic equations). Due to the presence of a possibly resonant
interface, the standard technique based on a total variation estimate does not
apply, and DiPerna's uniqueness theorem must be used. Following a method
proposed by Coquel and LeFloch, our proof relies on discrete entropy
inequalities for the coupling problem and an estimate of the discrete entropy
dissipation in the proposed scheme.Comment: 21 page
Liquid transport in scale space
International audienceWhen a liquid stream is injected into a gaseous atmosphere, it destabilizes and continuously passes through different states characterized by different morphologies. Throughout this process, the flow dynamics may be different depending on the region of the flow and the scales of the involved liquid structures. Exploring this multi-scale, multi-dimensional phenomenon requires some new theoretical tools, some of which need yet to be elaborated. Here, a new analytical framework is proposed on the basis of two-point statistical equations of the liquid volume fraction. This tool, which originates from single phase turbulence, allows us notably to decompose the fluxes of liquid in flow–position space and scale space. Direct numerical simulations of liquid–gas turbulence decaying in a triply periodic domain are then used to characterize the time and scale evolution of the liquid volume fraction. It is emphasized that two-point statistics of the liquid volume fraction depend explicitly on the geometrical properties of the liquid–gas interface and in particular its surface density. The stretch rate of the liquid–gas interface is further shown to be the equivalent for the liquid volume fraction (a non-diffusive scalar) of the scalar dissipation rate. Finally, a decomposition of the transport of liquid in scale space highlights that non-local interactions between non-adjacent scales play a significant role
Sex differences in brain plasticity: a new hypothesis for sex ratio bias in autism.
Several observations support the hypothesis that differences in synaptic and regional cerebral plasticity between the sexes account for the high ratio of males to females in autism. First, males are more susceptible than females to perturbations in genes involved in synaptic plasticity. Second, sex-related differences in non-autistic brain structure and function are observed in highly variable regions, namely, the heteromodal associative cortices, and overlap with structural particularities and enhanced activity of perceptual associative regions in autistic individuals. Finally, functional cortical reallocations following brain lesions in non-autistic adults (for example, traumatic brain injury, multiple sclerosis) are sex-dependent. Interactions between genetic sex and hormones may therefore result in higher synaptic and consecutively regional plasticity in perceptual brain areas in males than in females. The onset of autism may largely involve mutations altering synaptic plasticity that create a plastic reaction affecting the most variable and sexually dimorphic brain regions. The sex ratio bias in autism may arise because males have a lower threshold than females for the development of this plastic reaction following a genetic or environmental event
Mixed-convection from a bundle of heating cylinders in a cross-flow air-circulation. Experiment and analysis
Paper presented at the 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 1-4 July, 2007.Within the framework of radioactive waste management, the VALIDA program started to provide reliable data for the validation of numerical tools used to model the cooling of spent nuclear fuel containers in dry storage facilities. The design of such facilities implies thermal-hydraulic calculations in order to predict containers and wall temperatures. One has to make sure that these temperatures never exceed critical values. The understanding of mixed-convection flow in realistic conditions and more particularly the interaction between a global cross-flow circulation and local natural convection effects is a key point of these design studies. VALIDA experiments were carried out in this way at CEA on a multi canister configuration (7 rows heated tube bundle mounted vertically) in a special wind tunnel (length:12m, height: 3m width: 2m13) and cooled by a cross-flow air circulation. During the experiments, the air flow rate, the velocity profile and the heating power are controlled and have been adjusted to simulate various thermal-hydraulic conditions. A staggered tubes of seven rows of heated tubes (diameter 0.64m and height 2m) are placed in the wind tunnel, the 18 canisters arrangement use a triangular pitch (P/D = 1.66). Instrumentation includes thermocouples in the air flow, on the cylinders, and on the walls; the wind tunnel is rigged with two air-velocity measurement systems: LDV (Laser Doppler Velocimetry) and PIV (Particle Image Velocimetry). One presents the main experimental results reached with different values of the parameters: air velocity (0.25 to 1 m/s) and power density (300 to 600W/m²). From the downstream air measurements, a visualization of the temperature plume is obtained at different location behind the last tube. Measurements of air velocity are also performed with LDV laser in the air gap above the canisters. All the results show that the flow pattern of air strongly depends on the ratio of the buoyancy to the inertia forces. Convective transfers areas involving predominately forced or natural convection are distinguished thanks to established heat transfer correlations. A dimensionless buoyancy number Bo* is defined to characterize the experimental flow regimes obtained.cs201
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