2,636 research outputs found
Selfdecomposability of Weak Variance Generalised Gamma Convolutions
Weak variance generalised gamma convolution processes are multivariate
Brownian motions weakly subordinated by multivariate Thorin subordinators.
Within this class, we extend a result from strong to weak subordination that a
driftless Brownian motion gives rise to a self-decomposable process. Under
moment conditions on the underlying Thorin measure, we show that this condition
is also necessary. We apply our results to some prominent processes such as the
weak variance alpha-gamma process, and illustrate the necessity of our moment
conditions in some cases
Optically mediated nonlinear quantum optomechanics
We consider theoretically the optomechanical interaction of several
mechanical modes with a single quantized cavity field mode for linear and
quadratic coupling. We focus specifically on situations where the optical
dissipation is the dominant source of damping, in which case the optical field
can be adiabatically eliminated, resulting in effective multimode interactions
between the mechanical modes. In the case of linear coupling, the coherent
contribution to the interaction can be exploited e.g. in quantum state swapping
protocols, while the incoherent part leads to significant modifications of cold
damping or amplification from the single-mode situation. Quadratic coupling can
result in a wealth of possible effective interactions including the analogs of
second-harmonic generation and four-wave mixing in nonlinear optics, with
specific forms depending sensitively on the sign of the coupling. The
cavity-mediated mechanical interaction of two modes is investigated in two
limiting cases, the resolved sideband and the Doppler regime. As an
illustrative application of the formal analysis we discuss in some detail a
two-mode system where a Bose-Einstein condensate is optomechanically linearly
coupled to the moving end mirror of a Fabry-P\'erot cavity.Comment: 11 pages, 8 figure
Radiative decays of decuplet hyperons
We calculate the radiative decay widths of decuplet hyperons in a chiral
constituent quark model including electromagnetic exchange currents between
quarks. Exchange currents contribute significantly to the E2 transition
amplitude, while they largely cancel for the M1 transition amplitude.
Strangeness suppression of the radiative hyperon decays is found to be weakened
by exchange currents. Differences and similarities between our results and
other recent model predictions are discussed.Comment: 11 pages, 1 eps figure, revtex, accepted for publication in Phys.
Rev.
Magnetization screening from gluonic currents and scaling law violation in the ratio of magnetic form factors for neutron and proton
The ratio exhibits a decrease for four-momentum transfer
Q^2 increasing beyond 1 GeV^2 indicating different spatial distributions for
charge and for magnetization inside the proton. One-gluon exchange currents can
explain this behaviour. The SU(6) breaking induced by gluonic currents predicts
furthermore that the ratio of neutron to proton magnetic form factors
falls with increasing Q^2. We find that the
experimental data are consistent with our expectations of an almost linear
decrease of the ratio with increasing Q^2,
supporting the statement that the spatial distributions of magnetization are
different for protons and for neutrons.Comment: 10 pages, 3 figure
Optimal Design of Bacterial Carpets for Fluid Pumping
In this work, we outline a methodology for determining optimal helical flagella placement and phase shift that maximize fluid pumping through a rectangular flow meter above a simulated bacterial carpet. This method uses a Genetic Algorithm (GA) combined with a gradient-based method, the Broyden-Fletcher-Goldfarb-Shanno (BFGS) algorithm, to solve the optimization problem and the Method of Regularized Stokeslets (MRS) to simulate the fluid flow. This method is able to produce placements and phase shifts for small carpets and could be adapted for implementation in larger carpets and various fluid tasks. Our results show that given identical helices, optimal pumping configurations are influenced by the size of the flow meter. We also show that intuitive designs, such as uniform placement, do not always lead to a high-performance carpet
A Peer-to-Peer Approach to Content-Based Publish/Subscribe
Publish/subscribe systems are successfully used to decouple distributed applications. However, their e#ciency is closely tied to the topology of the underlying network, the design of which has been neglected. Peer-to-peer network topologies can o#er inherently bounded delivery depth, load sharing, and self-organisation. In this paper, we present a contentbased publish/subscribe system routed over a peer-to-peer topology graph. The implications of combining these approaches are explored and a particular implementation using elements from Rebeca and Chord is proven correct
The immune response of rainbow trout to Flavobacterium psychrophilum following immersion-challenge model with and without hydrogen peroxide pre-treatment
On higher congruences between cusp forms and Eisenstein series
In this paper we present several finite families of congruences between cusp
forms and Eisenstein series of higher weights at powers of prime ideals. We
formulate a conjecture which describes properties of the prime ideals and their
relation to the weights. We check the validity of the conjecture on several
numerical examples.Comment: 20 page
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