5,234 research outputs found
Heavy Flavour Physics at the LHC
A summary of results in heavy flavour physics from Run 1 of the LHC is
presented. Topics discussed include spectroscopy, mixing, CP violation and rare
decays of charmed and beauty hadrons.Comment: 25 pages, 9 figures (total 17 subfigures). Invited review for Comptes
Rendus de Physique de l'Academie des Science
Interaction of point sources and vortices for incompressible planar fluids
We consider a new system of differential equations which is at the same time
gradient and locally Hamiltonian. It is obtained by just replacing a factor in
the equations of interaction for N point vortices, and it is interpreted as an
interaction of N point sources. Because of the local Hamiltonian structure and
the symmetries it obeys, it does possess some of the first integrals that
appear in the N vortex problem. We will show that binary collisions are easily
blown up in this case since the equations of motion are of first order. This
method may be easily generalized to the blow up of higher order collisions. We
then generalize the model further to interactions of sources and vortices.Comment: 9 page
Estimation of the material budget of the LHCb detector
The material budget of the LHCb detector at the time of the DC 06 data challenge is estimated
Dynamics of Conformal Maps for a Class of Non-Laplacian Growth Phenomena
Time-dependent conformal maps are used to model a class of growth phenomena
limited by coupled non-Laplacian transport processes, such as nonlinear
diffusion, advection, and electro-migration. Both continuous and stochastic
dynamics are described by generalizing conformal-mapping techniques for viscous
fingering and diffusion-limited aggregation, respectively. A general notion of
time in stochastic growth is also introduced. The theory is applied to
simulations of advection-diffusion-limited aggregation in a background
potential flow. A universal crossover in morphology is observed from
diffusion-limited to advection-limited fractal patterns with an associated
crossover in the growth rate, controlled by a time-dependent effective Peclet
number. Remarkably, the fractal dimension is not affected by advection, in
spite of dramatic increases in anisotropy and growth rate, due to the
persistence of diffusion limitation at small scales.Comment: 4 pages, 2 figures (six color plates
Using ordinary multiplication to do relativistic velocity addition
Relativistic addition of velocities in one dimension, though a mainstay of
introductory physics, contributes much less physical insight than it could. For
such calculations, we propose the use of velocity factors (two-way doppler
factors). Velocities can easily, often by inspection, be turned into velocity
factors, and vice versa. Velocity factors compose by ordinary multiplication.
This simple device considerably extends the kinds of questions that can be
asked and answered in an introductory course.Comment: 6 page
Two-way coupling of FENE dumbbells with a turbulent shear flow
We present numerical studies for finitely extensible nonlinear elastic (FENE)
dumbbells which are dispersed in a turbulent plane shear flow at moderate
Reynolds number. The polymer ensemble is described on the mesoscopic level by a
set of stochastic ordinary differential equations with Brownian noise. The
dynamics of the Newtonian solvent is determined by the Navier-Stokes equations.
Momentum transfer of the dumbbells with the solvent is implemented by an
additional volume forcing term in the Navier-Stokes equations, such that both
components of the resulting viscoelastic fluid are connected by a two-way
coupling. The dynamics of the dumbbells is given then by Newton's second law of
motion including small inertia effects. We investigate the dynamics of the flow
for different degrees of dumbbell elasticity and inertia, as given by
Weissenberg and Stokes numbers, respectively. For the parameters accessible in
our study, the magnitude of the feedback of the polymers on the macroscopic
properties of turbulence remains small as quantified by the global energy
budget and the Reynolds stresses. A reduction of the turbulent drag by up to
20% is observed for the larger particle inertia. The angular statistics of the
dumbbells shows an increasing alignment with the mean flow direction for both,
increasing elasticity and inertia. This goes in line with a growing asymmetry
of the probability density function of the transverse derivative of the
streamwise turbulent velocity component. We find that dumbbells get stretched
referentially in regions where vortex stretching or bi-axial strain dominate
the local dynamics and topology of the velocity gradient tensor.Comment: 20 pages, 10 Postscript figures (Figures 5 and 10 in reduced quality
Analytic structure of the S-matrix for singular quantum mechanics
The analytic structure of the S-matrix of singular quantum mechanics is examined within a multichannel framework, with primary focus on its dependence with respect to a parameter (Ω) that determines the boundary conditions. Specifically, a characterization is given in terms of salient mathematical and physical properties governing its behavior. These properties involve unitarity and associated current-conserving Wronskian relations, time-reversal invariance, and Blaschke factorization. The approach leads to an interpretation of effective nonunitary solutions in singular quantum mechanics and their determination from the unitary family.Fil: Camblong, Horacio E.. University of San Francisco; Estados UnidosFil: Epele, Luis Nicolas. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Instituto de FĂsica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de FĂsica La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de FĂsica. Laboratorio de FĂsica TeĂłrica; ArgentinaFil: Fanchiotti, Huner. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Instituto de FĂsica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de FĂsica La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de FĂsica. Laboratorio de FĂsica TeĂłrica; ArgentinaFil: GarcĂa Canal, Carlos Alberto. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Instituto de FĂsica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de FĂsica La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de FĂsica. Laboratorio de FĂsica TeĂłrica; Argentin
The initial development of a jet caused by fluid, body and free surface interaction with a uniformly accelerated advancing or retreating plate. Part 1. The principal flow
The free surface and flow field structure generated by the uniform acceleration (with dimensionless acceleration Ï) of a rigid plate, inclined at an angle α â (0, Ï/2) to the exterior horizontal, as it advances (Ï > 0) or retreats (Ï < 0) from an initially stationary and horizontal strip of inviscid, incompressible fluid under gravity, are studied in the small-time limit via the method of matched asymptotic expansions. This work generalises the case of a uniformly accelerating plate advancing into a fluid as studied in Needham et al. (2008). Particular attention is paid to the innermost asymptotic regions encompassing the initial interaction between the plate and the free surface. We find that the structure of the solution to the governing initial boundary value problem is characterised in terms of the parameters α and ÎŒ (where ÎŒ = 1+Ï tan α), with a bifurcation in structure as ÎŒ changes sign. This bifurcation in structure leads us to question the well-posedness and stability of the governing initial boundary value problem with respect to small perturbations in initial data in the innermost asymptotic regions, the discussion of which will be presented in the companion paper Gallagher et al. (2016) . In particular, when (α, ÎŒ) â (0, Ï/2) Ă R+, the free surface close to the initial contact point remains monotone, and encompasses a swelling jet when (α, ÎŒ) â (0, Ï/2)Ă[1,â), or a collapsing jet when (α, ÎŒ) â (0, Ï/2) Ă (0, 1). However, when (α, ÎŒ) â (0, Ï/2) Ă Râ, the collapsing jet develops a more complex structure, with the free surface close to the initial contact point now developing a finite number of local oscillations, with near resonance type behaviour occurring close to a countable set of critical plate angles α = αân â (0, Ï/2) (n = 1, 2, . . .)
Superantenna made of transformation media
We show how transformation media can make a superantenna that is either
completely invisible or focuses incoming light into a needle-sharp beam. Our
idea is based on representating three-dimensional space as a foliage of sheets
and performing two-dimensional conformal maps on each shee
Diffusion-Limited Aggregation on Curved Surfaces
We develop a general theory of transport-limited aggregation phenomena
occurring on curved surfaces, based on stochastic iterated conformal maps and
conformal projections to the complex plane. To illustrate the theory, we use
stereographic projections to simulate diffusion-limited-aggregation (DLA) on
surfaces of constant Gaussian curvature, including the sphere () and
pseudo-sphere (), which approximate "bumps" and "saddles" in smooth
surfaces, respectively. Although curvature affects the global morphology of the
aggregates, the fractal dimension (in the curved metric) is remarkably
insensitive to curvature, as long as the particle size is much smaller than the
radius of curvature. We conjecture that all aggregates grown by conformally
invariant transport on curved surfaces have the same fractal dimension as DLA
in the plane. Our simulations suggest, however, that the multifractal
dimensions increase from hyperbolic () geometry, which
we attribute to curvature-dependent screening of tip branching.Comment: 4 pages, 3 fig
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